Food production will have to increase considerably over the next half century to ensure that everybody has all the food they want. The 9 billion or so individuals expected by 2050 will have to be much better fed than most of the present 6.5 billion.
At the moment, almost a billion people are under-nourished, receiving far from adequate levels of calories and other nutrients. The region with the largest number in this category is South Asia, where just under a quarter of the population are in this wretched condition. The region with the highest proportion in this category is Sub-Saharan Africa with over a third. Worldwide, some 170 million children under five years of age are underweight due to malnutrition. This makes them vulnerable to a range of diseases and it is estimated that around 3.7 million died in 2000 as a result. Two billion people or more have iron, iodine and zinc deficiencies and one fifth of the global disease burden is due to undernourishment.
Then there is the majority of people who receive a more or less adequate diet but with rising incomes aspire to more ‘luxury’ foods, such as fruit, vegetables, meat and dairy products, which for a given level of calorie consumption require a lot more resources to produce. The calories from a hectare of most varieties of fruit or vegetable are far less than the calories from a staple grain, such as corn, rice or wheat, grown on the same area. Likewise, in the case of grain-fed livestock and poultry that consume far more calories than what humans get from the final product. About 50 per cent of current world grain production goes to feeding animals rather than humans. Obviously if the grain were consumed directly, it would feed a lot more people. It would be more ‘calorie efficient’. Then we have increasing demand for products such as tea, coffee, alcoholic beverages, chocolate, herbs and spices that are not consumed for the nourishment but which draw on resources that would otherwise be available for the production of staples.
This increasing pressure on resources as most people move up the “food ladder” will be alleviated to some extent by a number of factors that increase calorie efficiency. These include: an increased preference for chicken rather than red meat; the development of a greater range of palatable meat substitutes; and the development of improved livestock and feed.
A major upsurge in vegetarianism might help, however, there are no signs of this happening. Besides, vegetarianism of the affluent requires a wide range of fruit, vegetables, herbs and spices and possibly various exotic grains that are low in yield and resource efficiency. Even in India where vegetarianism is imposed by the tyranny of religion, a growing share of grain is going to support the burgeoning dairy industry. Furthermore, total vegetarianism would actually be unhelpful, given that some resources are best used for meat production, e.g., grain by-products and pasture land that is unsuited for crops.
So, what are the prospects for improving average consumption levels and eventually reaching a stage where all countries have reached the satiation level achieved in developed countries? They are good as long as we can increase grain production at rates that exceed population growth. As for how long it will take, that will depend on the difference in the two growth rates.
Over time the task will be made easier as the rate of population growth declines. It has been falling since the late 1960s when it peaked at around 2.1 per cent. It is now around 1.13 per cent and according to the UN’s medium growth scenario, it is expected to fall further to 1.05 percent in the period 2010 to 2015, to 0.7 percent during 2025 to 2030 and 0.33 per cent during 2045 to 2050. So by mid century even a very modest increase in output would lead to an increase in the per capita average.
Doubling per capita consumption in developing countries can probably be achieved with a 2.4 to 2.6 fold increase in output. This is on the assumption that their population increases by 50 to 65 per cent (i.e., a world total between 9 and 10 billion) and that all the increase in output goes to developing countries. The latter assumption is realistic given that people in developed countries already have plenty to eat and their population is not expected to increase.
Grain production has been increasing at more or less a linear fashion over the last 45 years or more. While varying considerably from year to year, annual growth generally gravitated around 30 million tonnes. If we continue with a similar annual increase we will double production by around 2060 and provide more than a 50 per cent increase in per capita consumption in developing countries. A 2.5 fold increase would take until the final decade of the century.
If we can push up the pace and achieve the 2‑4 per cent annual growth rates achieved in the 1960s and 1970s we would reach the desired levels far more quickly. For example a 2 per cent annual growth rate would provide a 2.5 fold increase by 2050.
So, can we match or even exceed past achievements? Can science keep coming up with higher yielding crops and livestock? Can we ensure that there will be sufficient resources such as good quality land and water? Can we maintain or even increase the fish harvest? These and related questions will be addressed in the rest of the chapter.
The main reason for our success in increasing food production during the last 50 years has been the ability of science to increase the yield potential of our plants and livestock, and to improve their ability to cope with a range of hostile conditions. Can we maintain this performance or are we running out of steam?
The prospects look promising when you consider that we are at the beginning of a biotechnology revolution that is bound to bring major advances in plant and animal breeding. Biotechnology provides a tool kit that includes genetic engineering, genomics, marker assisted selection, cell and tissue culture, and increasing knowledge of how physiological characteristics can act as indicators of performance. This tool kit is already starting to bring results.
Both genetic engineering and marker assisted selection rely on our growing knowledge of genes being provided by genomics which aims to describe and decipher the location and function of all the genes of an organism, and the interactions between them.
Genetic engineering is opening up a totally new area of plant and livestock improvement. It allows us to directly manipulate the genes responsible for various attributes. This includes controlling the level of activity of genes by turning them on or off, or up or down, and also transferring genes from other plants or animals. Scientists will produce an increasing flow of results as they learn more about what genes confer what characteristics and improve their ability to manipulate genes, particularly multi-gene manipulation which is necessary in many cases.
Marker assisted selection (MAS) uses genetic markers to assist in selecting plant varieties with particular traits for inclusion in breeding programs. They are easily identified DNA sequences that are located near a specific gene associated with the trait. This technology is revolutionizing breeding methods because a large number of varieties can be screened for a desirable trait without having to grow them to maturity to determine its presence. Samples can be taken from seedlings and tested for the presence of the molecular marker. With traditional methods, a similar procedure would be far more time consuming and expensive, and often impractical. Checking for the continued presence of the markers can also determine whether the desired trait has been successfully transferred through the various stages of breeding and cross-breeding. This technology has already achieved considerable results, but will achieve a lot more as more is learnt about the role of genes in bestowing traits and their corresponding genetic marker is identified.
Tissue culture refers to a process where new plants are grown from individual cells or clusters of cells, often bypassing traditional cross-fertilization and seed production. This technique enables breeders to attempt wide crosses between varieties that could not be hybridized before and enable faster stabilization of breeding lines. Such methods are also used to produce pathogen-free plants for distribution to farmers and for germ plasm storage.
Better knowledge of what identifiable physiological features are associated with tolerance to certain conditions will assist the selection of varieties for inclusion in breeding programs. Features that are relevant to performance include: root structure that allows higher nutrient uptake, early ground cover to reduce evaporation of soil moisture and large seeds to assist early crop establishment.
There is also much that can be done without cutting edge science or major breakthroughs. In large parts of the developing world high yield plant varieties still need to be adapted to local conditions. And there are neglected crops such as cassava and banana that would benefit from the kind of attention that rice and wheat have received in the past. Likewise, livestock suited to the tropics can benefit from more research. Breeding the water buffalo for meat and milk is an example often cited.
There are also many farmers in the developing world who have yet to take advantage of what has already been achieved because their use requires a more advanced form of agriculture and economic infrastructure. This includes distribution of high-yielding hybrid seeds that cannot be home grown, support from extension services and access to necessary ancillary inputs such as fertilizer and reliable water needed to achieve the promised higher yields.
What is achieved in coming years will depend very much on the level of research funding. Research in recent times has been hampered by the cut back in funding to the major research institutions in the last decade, including those associated with the Consultative Group on International Agricultural Research (CGIAR), the main umbrella organization for research in developing countries. Funding began to decline once research efforts had dealt with the urgent problems of the 60s and 70s by providing a new generation of high yielding rice and wheat. Notwithstanding this problem there are still a whole range of important improvements at various stages along the pipeline. We’ll look first at the higher yielding plants currently being developed and then the advances in livestock and feed.
The examples provided are meant to give a general indication. They are not exhaustive and some of those in the pipeline may never see the light of day. Not included is speculation of what may be on offer two or three generations down the track when our knowledge is far more advanced. Perhaps, one day we will produce food directly without having plants or animals as intermediaries. If a plant can produce grain surely we can, and with a multitude of customized features. Likewise for producing muscle tissue (i.e., meat) without the rest of the animal. The output from any given input of land or water with such technology would increase dramatically.
Plants can be improved in a number of ways. Firstly we can increase their yield potential. This is the yield that can be achieved under the best conditions in terms of weather, water and soil. Secondly we can increase their capacity to narrow the gap between actual and potential yields under less than favorable conditions, i.e., conditions of stress. Thirdly we can increase the ability of the crop to survive in an edible state after it is harvested.
Yield potential of plants can be increased by various means. Hybridization is one approach. Thanks to an imperfectly understood effect called heterosis, the hybrid from a cross of two different plant varieties grows more vigorously and produces more grain than either parent. In some crops including maize this process is simple. However, with other major crops it is a difficult and ongoing process.
Hybrid rice was first developed in China in the early 1970s and is now planted on about half that country’s rice growing area. First generation hybrids have increased yields by 15 to 20 percent and second generation by a further 5 to 10 per cent of their predecessors. A third generation is now being developed which will increase yields even further. Other Asian countries are now beginning to follow suit, developing their own varieties in line with their own palates and environmental conditions. Chinese scientists have also recently managed to develop and test a hybrid wheat breed that could at least double their country’s present per-hectare yields. They have also recently created the first hybrid soybean which is expected to increase yields by 20 per cent.
Researchers can also breed plants that put more energy into grain production and less into the rest of the plant. Researchers are working on a new rice and wheat ‘architecture’ that will significantly increase their harvest index, in other words more grain and less plant. This will be achieved by developing varieties with larger grain heads on thicker but fewer stems.
Other fascinating approaches include: crop plants with an algae gene that boosts yields by almost a third because the new strain converts nitrogen fertilizer far more efficiently and rice with an antisense gene, that inhibits the formation of certain proteins and thus prolongs the grain-filling period of the plant. This rice, in its first field test, increased productivity by 40 per cent.
A long-term hope among some scientists is to create plants that are far more efficient at photosynthesis, the process that converts sunlight into energy. If this could be improved, plants could reach maturity more quickly, allowing more crops each year. Nitrogen fertilizer consumption could also be reduced because photosynthesis is the main consumer of this input. Apparently photosynthesis is very inefficient and worked a lot better back in the early days of plants when the atmosphere had little or no oxygen. A number of projects are doing very preliminary research on this problem.
Crops are generally grown under less than ideal conditions which subject them to stresses that can reduce yields quite significantly. These stresses are usually classified into biotic and abiotic. Biotic stresses include the ravages of diseases and insects, and competition from weeds, while abiotic (or non-biological) stress includes the effect of too much or too little water, excessive heat or cold and soil problems such as salinity, acidity and erosion.
Because the amount of damage is quite high, there is much to be gained by improving plant tolerance. And the prospects for progress in this area look very good, with the level of success depending mainly on the extent of funding and the supply of trained workers.
Where crops have a particular strain or wild relative that copes well with a particular stress, this feature can be incorporated into existing commercial varieties through cross breeding. This can be assisted by the use of molecular marker technology to screen a large number of varieties where it is known which gene expresses a particular feature. Where reproduction is through cuttings, tissue culture can provide farmers with disease free plants.
Using genetic engineering, changes can be made directly at the gene level to bestow tolerance. This may involve transferring a gene from a totally different life form that is known to cope well with the particular stress or tweaking the plants existing genes to achieve a similar effect. The more we know about genes and how to manipulate them, the more that can be achieved.
The examples provided below should give a fair indication of the kind of work being done. While some are already showing up in farmers’ fields most are still at the research and development stage. It is not an exhaustive list and there are no doubt very important omissions, and possibly some inclusions that will not meet up to expectations. We will start with biotic stresses.
Rice has been genetically engineered to resist devastating diseases such as sheath blight, bacterial blight and tungro virus. Sheath blight resistance has been achieved through the transfer of genes from an insect and from the soil bacterium Bacillus thuringiensis, more commonly called Bt. Scientists have also successfully transferred a bacterial resistance gene from wild rice to cultivated rice. In the case of barley, resistance to a particular disease has been conferred by a wine grape gene.
Scientists are working on a bread wheat that is resistant to the devastating leaf blotch. They have discovered a gene that provides resistance to this disease and are using marker technology to find wheat varieties with this gene. As soon as a seedling sprouts, a small piece of the young leaf can be ground and then a DNA test can be run. This shows whether the markers for the gene are present.
A transgenic potato is being developed that is resistant to the late-blight that caused the Irish famine in 1840 and still causes major havoc. Fungicide has limited effect, is expensive and when used in large amounts can be an environmental problem. The protective gene comes from a wild potato that scientists believe co-evolved in Mexico alongside the blight pathogen. Potatoes could also become a major food source in tropical countries with the development of a variety incorporating a gene from chicken that resists bacterial rot.
Reducing disease in the banana would make a major difference in poor countries where it is a staple food. Because the domesticated banana is usually a seedless clone which grows from cuttings, tissue culture is being introduced to propagate offspring that do not carry over disease from the parent plant. Disease-free cells are selected, removed under sterile conditions and placed in a growth medium. The resulting plants are then distributed to farmers.
Researchers are working to map the entire genetic code of a wild banana from East Asia in the hope it will reveal the genes that provide resistance to the two worst enemies of the banana crop – black Sigatoka and Panama fungal diseases. Once identified, researchers hope to insert these genes into edible var-ieties.
In the battle against viruses, techniques have been developed to insert harmless parts of the virus into the plant to set off an immune reaction much like an inoculation. And having become part of the plants genetic make up it is passed on to the next generation. The most dramatic example of such a process was papaya in Hawaii which had been devastated by papaya ring spot virus. A genetically engineered plant virtually brought the industry back from extinction. A biotech papaya is now being brought to farmers in Southeast Asia, the Caribbean and several other developing areas where papaya is a staple food. In Australia, scientists have developed a similar ‘vaccination’ technique that has already been used to create potatoes resistant to Potato Leaf Roll Virus and which they hope to apply to a range of plants that are vulnerable to viruses which up till now have proven to be virtually unbeatable.
Providing plants with their own defenses against insects and pests can often be far more effective than other measures such as pesticides, or, at the very least, an important adjunct. In recent years the most dramatic advance in this regard has been the development of so-called Bt crops. This has also been one of the major genetic engineering success stories to date. The plant expresses insecticidal proteins derived from genes cloned from the soil bacterium Bacillus thuringiensis (Bt). These proteins bind to receptor proteins in the insect gut, destroying cells and killing the insect in several days.
Quite large areas are now being sown with Bt corn, canola and cotton. A Bt potato has also been available for use, however, major buyers such as fast food chains have put the stopper on it for fear of been picketed by bio-fearmongers. The more widespread use of these Bt varieties in coming years and the introduction of the gene into other crops including rice and wheat will bring continuing benefits. Yield gains from using Bt corn are estimated to average 5 per cent in temperate regions and 10 per cent in tropical regions.
This is just the first of many toxins that will be provided to plants through genetic manipulation. Included among them will be the transfer of genes from other plants that have shown themselves to be more resistant to given insects. Australian researchers have added a gene from green beans to field peas, creating a crop with a built-in insecticide that is almost 100 per cent effective against pea-weevils, the most damaging pest in that country’s pea crop. Also resistance to the white-backed plant hopper is being transferred from barley to rice.
Plant ‘architecture’ can also provide protection. This includes: developing wheat with more solid stems that will be less susceptible to attack by Hessian fly and sawfly; maize with thicker epidermal cell walls that prevent armyworm larva establishing in the whorl (hair) of the plant; and plants with an enhanced natural ability to produce leaf wax which makes them more difficult for insects to consume.
One of the most destructive pests is the nematode, a microscopic worm that feeds on plant roots and comes in about 15,000 varieties. Scientists are using the genes for defense proteins that occur naturally in rice and sunflowers to fortify potatoes and bananas from this pest. And the breeding of a nematode resistant soybean has been made possible with the help of molecular marker technology.
Another stress that reduces crop yields is the competition from weeds. The biggest news in this area is the introduction of herbicide resistant genetically modified corn and soybeans. The crop contains a gene that makes it tolerant of the herbicide, Roundup, so that when a farmer sprays the field, weeds are killed but not the crops. This proves far more effective than when spraying can only be carried out prior to planting. A weed called striga can devastate grain and legume harvests in Sub-Saharan Africa. Researchers are countering this problem by developing a maize with a herbicide resistance derived from a naturally occurring gene in maize.
There is a concern that pests can evolve resistance to the pesticide being incorporated in plants by genetic engineering, just as they evolve resistance to pesticide sprays. So far resistance has not become a problem with Bt crops despite their having been in use since 1996. Scientist are looking at a number of strategies to delay or eliminate this danger. One approach is to use a Bt gene that is more widely expressed in the plant giving a better knock out punch that leaves less room for the build up of immunity that can happen when the insect experiences lower levels of exposure. Another is the use of “pyramiding” where two Bt genes which are lethal in totally different ways are inserted into the plant. It is highly improbable that an insect would develop resistance to both.
As well as dealing with a host of weeds and pests, crops also have to contend with the elements. The weather can be too dry, wet, hot or cold, and the soil can be poor.
Droughts and Flooding Rains
Lack of water is a major constraint on crop yields in many areas and can destroy a crop in severe cases.
Crossing with drought resistant wild relatives is one approach. For example, CIMMYT (Centro Internacional de Mejoramiento de Maíz y Trigo or International Maize and Wheat Improvement Center) is currently developing drought-resistant wheat varieties descended from crosses that included goat grass, one of wheat’s wild relatives.
Progress is being made by CIMMYT in mapping genes for drought tolerance in wheat and researchers at the University of Queensland are endeavoring to do the same for rice.
Transferring to crops draught tolerance genes from other plants is another promising approach. It is believed that once the genes responsible for superior drought tolerance in sorghum are identified that these genes could be activated in maize because the two plants are likely to share the same basic drought tolerance pathways. Scientists at the University of Bonn have identified a gene in the resurrection plant from South Africa which helps it to survive droughts. The plant can lose up to 95 per cent of its moisture without being harmed by slowing down its metabolism to almost zero during a dry period. It then springs back to life in a few hours once it receives water. In Texas, US Department of Agriculture (USDA) researchers have identified the genes that help a type of grass from South Africa and a type of moss native to the High Plains of the United States to survive extended dryness.
Plant varieties can be bred with physiological traits conferring drought tolerance. Molecular biologists in Oklahoma are developing a drought resistant wheat by adding genes to synthesize a naturally occurring sugar alcohol called mannitol which accumulate in leaf tissues. Other helpful physiological features include larger seed size that improves crop establishment, early ground cover and pre-anthesis biomass that reduces evaporation of soil moisture, and roots that are able to extract water deep in the soil.
Another strategy which might be more aptly called drought avoidance rather than drought tolerance involves breeding plants that match their development cycle with the availability of water. This has been used in the past and still offers much promise. In some cases this could mean that the periods of maximum water requirement match the periods of maximum availability. In other cases it could mean ensuring maturity prior to the arrival of a dry period at the end of the growing season. This could be achieved through faster maturity or through allowing earlier planting by developing varieties that can cope with shorter daylight hours.
Where plants are not being deprived of water there is a good chance they are being drowned in it. A widespread problem in irrigated and high rainfall wheat-growing regions is water logging due to poor drainage. The prospects for developing water logging tolerant wheat are considered good because of genetic variability for this trait. Breeders have found that “synthetic” wheat, bred from grass species that are the wild relatives of wheat, are exceptionally good sources of tolerance.
Heavy rain on maturing wheat crops can cause the grain to start germinating before it is harvested. This degrades end-use quality due to the undesirable proteins produced during germination. CIMMYT has identified high rainfall wheat lines with high levels of sprouting tolerance which could be employed in breeding programs to rectify this problem.
Hot and Cold
Just as it can be too wet or too dry, it can also be too hot or too cold. Agricultural research bodies in developing countries consider heat stress as one of their top research priorities. CIMMYT has already had some success in identifying wheat varieties in their seed banks that have various traits generally associated with tolerance to heat stress. This includes leaf traits such as evapotranspiration, rolling, greater thickness or uprightness. They expect genetic markers to facilitate the process. Similar efforts are also being made in the case of tropical maize. And on the genomic front, researchers have identified a protein that acts as a master regulator of the tomato heat stress response.
Cold tolerance can bestow a range of benefits. It can ensure that the crop won’t be destroyed by a cold snap at the beginning of growing season. It can allow crops to be grown in climates too cold to support them currently or permit an extra crop by earlier planting and/or later harvesting.
The Chinese claim to have inserted cold tolerance genes from fish into beets, while British researchers are achieving similar results by incorporating a gene from carrots into various crops. Researchers in Canada, have isolated a powerful gene from larvae of the yellow mealworm beetle that keeps the worms from freezing to death during the winter. They believe it is far more powerful than ‘antifreeze genes’ found in flounder, a fish which is no slouch when it comes to protecting itself in cold waters.
Where the cold cannot be dealt with head on, it can be avoided by making plants grow faster. Researchers at Cambridge University’s Institute of Biotechnology in England put a gene from a flowering weed into tobacco plants, making the tobacco grow much more quickly. The gene produces a protein that causes the plant cells to divide much faster at the tips of roots and shoots.
Plants can find the soil far from friendly for a range of reasons ‑ in particular, salinity, poor structure and acidity.
Some crops have genetic variation for salt tolerance which can be exploited in breeding programs, particularly with the help of molecular markers. Chinese researchers claim to have developed salt-tolerant varieties of rice and Australian researchers announced that they have successfully bred salt-tolerant durum wheat by crossing an ancient salt-tolerant durum wheat variety with modern commercial ones.
Genetic engineering can take traits from plants and organisms that thrive in a high salt environment. Scientists have genetically modified a tomato plant that thrives in salty irrigation water. The tolerance comes from a protein known as a ‘sodium/proton antiporter,’ which uses energy available in the plant cells to move salts into compartments within the cells. Once the salt is stashed inside these compartments – called vacuoles – it is isolated from the rest of the cell and unable to interfere with the plant’s normal biochemical activity. Not only does the tomato tolerate salt, it also removes salt from the soil. Work is being done to extend this technology to other crops. Chinese scientists have cultivated salt-resistant tomatoes, soybeans, rice and a fast-growing poplar using a gene cloned from a salt-resistant plant called Suaeda Salsa. Another possible approach is to take genes from a bacteria that lives in places like the Dead Sea and splice it into crops.  This bacteria can thrive in salt levels ten times higher than ocean water.
Plants often have difficulty accessing the micro-nutrients in the soil because of its structure or composition. Improving the take up ability of the root system may help, possibly through better root system geometry. So would increasing the nutrient reserves in seeds. These would sustain life until the root system is well developed. Another approach might be to reduce the plants needs for certain nutrients. Improving their distribution within the plant would be one way of achieving this. Little effort has gone into breeding crops adapted to these kinds of soil conditions despite the genetic potential. Molecular markers will greatly facilitate the selection of micronutrient efficient genotypes. Genetic engineering also offers promise. A gene for copper efficiency has been transferred from rye to wheat. The transferred gene confers on plants a much greater ability to mobilize and absorb copper ions tightly bound to the soil. Major crops such as corn, wheat and rice have a lot of trouble absorbing iron from alkaline soils which make up a significant proportion of arable land. However, some crops including barley have no trouble. So researchers at the University of Tokyo took two genes from barley and introduced them into rice plants. The result was a four-fold yield increase in the same soil.
Soil acidity is a major constraint on crop production. This is mainly because it releases aluminum ions which are highly toxic to plant roots. Vast areas either have their yields seriously reduced by it or are made unsuitable for cultivation. The problem is particularly serious in tropical regions. While, improving acid soils is part of the answer, its role is limited by the expense and by the fact that disturbing the soil can lead to erosion. Developing aluminum tolerant plants is often a feasible solution either on its own or as a complement to soil improvement.
There are good prospects for wheat given that there is considerable genetic diversity in aluminum tolerance. In Brazil local low yield aluminum tolerant wheat varieties have been interbred with high yielding varieties to provide the benefits of both. A Portuguese landrace also has a high aluminum tolerance and has yet to be exploited in breeding programs. Another strategy is to transfer rye’s greater aluminum tolerance to wheat. Triticale (a cross between rye and wheat) could serve as a bridging parent to achieve this transfer.
In the case of maize, researchers are confident that molecular markers and genomics will lead to the development of aluminum tolerant suitable maize cultivars. Genetic engineering is also making some progress in the area. There has been some preliminary work on transferring a gene from an aluminum tolerant plant to maize. Another strategy being pursued is to insert into plants a bacterial gene that codes for citric acid secretion. This allows them to emulate aluminum tolerant plants the roots of which secrete the acid into the surrounding soil in order to ‘capture’ the toxic aluminum ions which would otherwise attack the plant roots. This approach has been trialed on tobacco, papaya, and rice plants.
There are many cases where yields would be increased significantly by the plant having more than one form of improved stress tolerance. For example, a crop may confront dry weather, acid soil and regular insect plagues. Genetic engineering ought to be able to contribute a great deal in this area by “stacking on” genetic changes appropriate for each of the stresses. A genetically modified maize that combines both herbicide tolerance and insect resistance has already been released; and there are already plans to extend this combination to other varieties, notably sugar beet, rice, potatoes and wheat.
As well as increasing the size of the crop, plant improvements can also increase the proportion that actually reaches the consumer. Ultimately this is what matters – yield net of post-harvest waste. A lot of food is lost through post-harvest spoilage, so anything that can make the harvested crop more robust will increase the effective food supply. This is particularly so in developing countries with poorer harvesting methods and a lack of refrigeration, storage and transport.
The delayed ripening of fruit and vegetables would improve shelf life and reduce spoilage. Genetic engineering is being used to control the amount and timing of the production of the hormone ethylene that regulates ripening in fruits and vegetables. Research has reached an advanced stage with tomatoes, raspberries, melons, strawberries, cauliflower and broccoli. And in the Philippines, scientists have developed a papaya that instead of rotting in one week, can stay fresh for three months. Researchers in England have found a “freshness gene” in petunias which shows promise.
In the case of grain, greater resistance to storage pests would make a big difference. CIMMYT has discovered a source of such resistance and is incorporating this trait into maize breeding stocks.
Just as crops have to deliver up more from every hectare of land and kiloliter of water, so do livestock and poultry. These resources are used directly in the case of grazing and indirectly where the animals consume feed crops. About 3.3 billion hectares are under permanent pasture – more than twice the area under arable and permanent crops. And as already mentioned domestic animals consume about half of world grain production. This ranges from around 60 per cent in Europe and the US down to quite low levels in India and Sub-Saharan Africa.
Improving livestock and poultry productivity becomes even more important as people in the developing countries increase their per capita consumption of meat and dairy products in step with rising income levels. For most of these countries increases in meat consumption have so far been fairly slight if not stagnant, as in the case of Sub-Saharan Africa. However, if middle income countries such as China and Brazil are anything to go by meat consumption can rise dramatically over a number of decades. In the case of China, meat consumption has quadrupled over the past 20 years.
Increased productivity comes down mainly to improvements in feed and forage, disease control and livestock breeding. As with grain production for human consumption, this is in part a matter of developing countries catching up with the practices of developed ones and in part a matter of pushing out the technology frontier. The former is exemplified by the fact that in 1997-98 beef yield per animal was less than 60 per cent and milk yield per cow was less than 20 per cent of those achieved in the developed countries.
There are many ways in which we can improve what livestock have to eat. Feed and fodder can be made more nutritious, the diet can be enhanced with additives and supplements and nutrients in food can be made more accessible by improving digestibility.
In developing countries simply catching up with the world’s best feed practices can bring large gains. Feed can be harvested at the right time to maximize nutrient recovery, processed to retain more nutrition and improve digestibility, and stored properly to avoid nutrition loss. Animals can also benefit from being fed well balanced mixtures and provided with food supplements.
Smil (2000) points out that the overwhelming majority of China’s pigs (which account for 90 percent of the country’s meat output) is still not fed well-balanced mixtures but just about any available edible matter and hence it is commonly lacking in protein. As a result feeding rates are well above the norms prevailing in Western countries and pigs take at least twice as long to reach slaughter weight as a typical North American animal – and its carcass is still lighter and fattier. He tells a similar story for chickens. The hundreds of millions of chickens roaming China’s farmyards take three times as long to reach a lower slaughter weight as North American broilers. China is far from being the most backward when it comes to animal raising.
Conway mentions a number of possible ways that genetic engineering could transfer greater nutrition to feed and forage. Cereals are low in lysine compared with legumes such as peas and lupins. A gene transfer from legumes to cereals would benefit pigs and chicken. On the other hand legumes are deficient in a number of sulphur amino acids required by cattle and sheep. These would benefit from transferring genes from sunflower seeds and chicken egg protein to forage legumes such as lucerne and clover.
The wider use of growth hormones could considerably improve productivity. Those in cattle (BST) increase milk production efficiency by up to 40 per cent per cow and increase feed to beef conversion by about 9 per cent. According to Avery the potential of pig growth hormone (PST) is even greater than for cattle. He claims that PST will produce hogs with up to 60 percent less fat and 15 percent more lean, using one-third less feed grain.
Reducing methane production in livestock could save up to 10 percent of feed because of the energy loss avoided. Smil refers to an additive, produced from a fungus, which reduces methane production by altering the metabolism of ruminant bacteria, and scientists are developing a vaccine that will discourage the production of these methanogenic micro-organisms.
Much can be done to improve the digestibility and nutrient absorption of feed. Better processing is one approach. For example, straw can be made more digestible by a range of chemical treatments, and lignin and cellulose in crop residue can be broken down using a range of methods including fermentation. Plants can be bred to remove or neutralize substances that interfere with digestibility and nutrient absorption. Soybeans and wheat are being genetically engineered to express the phytase enzyme. This neutralizes phytate, a substance that “is widely distributed in cereals and legumes and reduces the absorption of iron, zinc, phosphorus and other minerals in humans and other animals.” Researchers have genetically modified lupin so that sheep absorb more sulphur amino acids required for wool and muscle growth. Presently, a large proportion of the acids are broken down in the rumen before reaching the small intestine where they would otherwise be absorbed. The lupin has been modified to contain a sunflower gene that produces a protein that is both rich in sulfur amino acids and stable in the sheep’s rumen. And Conway refers to research aimed at inserting genes from crops like sorghum, maize, millet into forage legumes to reduce lignin content and increase their digestibility by 10-30 per cent.
Disease significantly affects livestock productivity. Alexandratos refers to estimates showing that at least 5 percent of cattle, 10 percent of sheep and goats and 15 percent of pigs die annually due to diseases. And in the case of animals that survive, productivity is less than that for healthy animals.
Farmers in developing countries will benefit from access to better veterinarian services and disease control measures as they modernize and farmers worldwide will benefit from the forward march of medical and veterinary science which will improve our ability to prevent, diagnose and control disease.
As with human health, biotechnology will play an important part in disease control. Some progress has already been made in the development of genetically engineered vaccines. For example, researchers at the School of Veterinary Medicine at the University of California, Davis have been developing such a vaccine for rinderpest, a devastating viral disease that is responsible for millions of deaths among cattle herds each year throughout Africa and Asia. The vaccine is produced by transferring two genes from the rinderpest virus into the virus used to make the smallpox vaccine. It is particularly suited to the backward areas affected because it requires no refrigeration and is simply scratched onto an animal’s neck or abdomen. Furthermore, a cattle herder can produce thousands of doses by scratching the skin of a calf, applying the seed vaccine, and a week later harvesting the scab in saline solution.
In central Africa sleeping sickness (trypanosomiasis) poses an enormous obstacle to human health and cattle production. A range of measures offer the hope of recovering infested areas for agriculture. These include trypanocidal drugs, aerial spraying, adhesive insecticides, impregnated screens and traps and the use of sterile insects.
Breeding programs can improve livestock and poultry in a range of ways that ensure that they make the most of what they are fed. This can mean more meat as a proportion of body weight, taking less time to reach slaughter age, greater disease resistance, better ability to process food, less nutrient needs, more milk or eggs for a given level of feed, improved reproductive efficiency and the ability to consume a wider range of foods.
As with plants, biotechnology will play a major role in future breeding programs. With rapid advances in understanding the genetic make-up of animals, genes that are important for economic performance, such as those for disease resistance or for adaptation to adverse environmental conditions, can be identified and transferred into animals, either through marker-assisted selection or through genetic engineering.
Conway reports on the development of genetically engineer livestock that produce greater quantities of bovine growth hormone. This would enable them to reach optimal slaughter age more quickly, meaning that less of the feed and water consumed would go into just standing around breathing rather than growing.
Another strategy is to reduce the nutrient needs of the animal. Conway suggests the possibility of introducing genes for sulphur amino acid biosynthesis, present in the bacterium E. coli, directly into sheep, bypassing the need for improved fodder.
Given the high losses from disease, the transfer of genes encoding for resistance from other animal species and even from plants could bring significant benefits. For example, a genetically modified cow is being developed with a mouse gene that makes them resistant to mastitis of the udder. Currently, antibiotics are used to treat the disease, and the milk cannot be used while the cows are on the drugs.
Smil sees much to be gained in devoting more resources to breeding animals suited to the tropics, a region that has not received anywhere near the attention of the temperate zones. He gives the example of how the water buffalo might be transformed from a working animal into a valuable meat and milk specie. It is particularly suited to tropical and sub-tropical climates. Because of the higher count of cellulose-breaking bacteria and protozoa in their guts, they use low-grade roughages more efficiently than normal cattle and have overall lower feed/gain ratios. In addition, buffalo milk is richer in protein and fat than cow’s milk. However, a breeding program would be needed to raise their average milk and meat yields which are far behind those for temperate-climate cattle.
While genetic engineering promises to contribute much to the challenge of increasing food production, its opponents have managed to whip up considerable opposition. We are told that it is ‘unnatural’, tinkering with nature, playing God; that it poses fearful food safety risks and threatens the environment with ‘super weeds’ and ‘genetic pollution’. We are like the master’s apprentice tinkering with forces we do not really understand and which can get out of our control.
A host of inquiries have given genetically modified food the nod of approval and firmly rebutted the claims of opponents. They consider the risks are mostly identical to the risks associated with conventional foods and that those that are different are well covered by the regulatory regimes in place. The only real concern is that as changes made by genetic engineering become more varied and complex that the science and technology needed to assess them keeps pace.
A range of regulatory bodies are involved assessing and regulating transgenic crops. In the US there is the Food and Drug Administration (FDA), the Department of Agriculture (USDA) and the Environmental Protection Agency (EPA). At the international level there is the World Health Organization (WHO) and the Food and Agricultural Organization (FAO). Genetically engineered crops have been grown and tested for 20 years and eaten by millions of people on a daily basis since 1996 without any disastrous consequences.
There is no credible evidence that GM foods are less safe to consume than other food. The risks are not of a different nature than those that are already familiar to toxicologists and can be created by conventional breeding. In fact some transgenic food currently on the market are identical to the conventional product because the gene change is not in the final product. Where there is a change to the final product, it will be easier to evaluate for safety compared to those developed through traditional breeding because the new method is more precise. Instead of randomly combining all the traits of the two parent organisms, as happens with conventional breeding, genetic engineering permits identification and transfer of only desirable traits. Scientists know what has been changed and therefore what to look for when evaluating possible risks.
In its short history, transgenic food has had three main food safety claims against it. These were the study which claimed that laboratory rats were being poisoned by GM potatoes; concerns about the use of antibiotic resistance genes in the gene transfer process; and the introduction of allergens. We examine these in turn.
A preliminary study performed at the Rowett Research Institute in Scotland by Dr Arpad Pusztai reported that rats developed intestinal problems after being fed raw transgenic potatoes containing a lectin with known insecticidal properties. The study was heavily criticized by independent experts and by the Rowett Institute itself, which discredited the study entirely after performing an audit of the research.
The British medical journal Lancet made the unwise decision to publish the study. In an editorial disowning it, they conceded that they were caving into pressure from GM opponents who were running the line that failure to publish was suppression. This flies in the face of the normal practice of academic journals of only publishing papers that have successfully run the gauntlet of peer review. With laboratory studies the emphasis is on ensuring that the usual rules of evidence are being applied. This study failed that test totally.
There has been some objection to the incorporation of antibiotic-resistant marker genes in transgenic crops together with the gene conferring the desired trait. The antibiotic kills seedlings to which the genes have not been properly transferred. There has been a worry that if these genes were present in transgenic food or feed, they could confer resistance to disease-causing micro-organisms in the stomachs of any human or farm animal eating it. There is even a concern that antibiotic resistance could be passed on to people who consume livestock products.
There are a number of answers to these fears: (1) The resistance gene protects against an antibiotic which is not used on humans and animals; (2) The antibiotic resistance may not necessarily be transferred to the final plant variety distributed to farmers because it is the product of a cross between the original transgenic plant and a commercial one; (3) if it is transferred, the chance of it being incorporated into the genetic make-up of micro-organisms is zero, and this is even if we didn’t allow for the effect of digestion which tends to totally destroy genes and DNA; and (4) recent attempts to get microbes to pick up the trait confirmed the impossibility. Even if the worry had some grounds to it, it is becoming a thing of the past as researchers develop other methods to determine whether a gene has “taken.”
Another potential risk posed by GM foods is the introduction of genes from organisms that cause allergic reactions in some people. This would pose a problem if people with allergies are unaware of the danger. This is most likely if the GM food is a widely used ingredient. Outside a relatively small number of genes associated with a limited number of foods, allergic reactions are fairly rare. Most food allergies occur in response to specific proteins in only eight foods: peanuts, tree nuts, milk, eggs, soybeans, shell fish, fish and wheat. Furthermore, the small risk is totally under control. Any additional components added to a GM crop are clearly defined and easy to detect and can be tested for any allergic reaction or other toxic effect. These would be picked up in mandatory tests that are much the same as those for pesticides and food additives. This is what happened in the case of an experimental soybean with an added Brazil-nut protein. It was abandoned once the problem was recognized.
A long list of relevant bodies have concluded that genetically modified food is as safe as any other food. These include: the WHO, the FAO, the United Nations Food Program, the International Society of Toxicology, the French Academy of Science and Medicine, the American College of Nutrition, the American Medical Association, the General Accounting Office (the investigative arm of the US Congress), the National Academy of Sciences (NAS), the Royal Society and the British Medical Association.
GM foods are not only safe, they have the potential to make food even safer and healthier.
Removing allergens Eliminating or reducing the allergenic properties of food would be a major service to that significant proportion of people who suffer from allergies. Using gene silencing techniques which reduce or shut off the production of the offending protein, researchers have already grown low allergy rice, wheat and soybean while progress is being made with peanuts and prawns.
Healthier oils In an effort to create healthier fats, researchers have modified the fatty acid composition of soy and canola in several ways. This includes oils with reduced or zero levels of saturates and trans-fatty acids and with high levels of oleic acid. Plans are also afoot to introduce fish type omega-3 into oil-seed crops. This could be achieved by introducing genes from algae and marine micro-organisms.
Better frying potatoes A transgenic potato has been developed which contains a gene for an enzyme which greatly increases starch synthesis. The increased starch content makes the potatoes take up less fat during frying, resulting in a lower-fat product.
More protein In India, a gene was added to ordinary potatoes giving them a third more protein than normal, including substantial amounts of the essential amino acids lysine and methionine. The new gene comes from the amaranth plant which grows in South America. Protein enriched maize and soybeans have also been produced and researchers are seeking to improve the protein content of vegetable staples such as cassava and plantain.
Antioxidants Scientists have produced tomatoes with two and half times the normal level of lycopene. Lycopene is thought to reduce the risk of several types of cancer and some forms of heart disease. However, it is normally difficult to increase the amount in one’s diet and taking it as a supplement does not work.
Another antioxidant that genetic engineering can help with is vitamin E. Studies show that vitamin E lowers the risk of cardiovascular disease, cataracts and some cancers, and it may slow the progression of some degenerative diseases such as Alzheimer’s. However, to achieve its results it needs to be taken in levels that are not practical to receive from our diet because of the quantities involved, e.g., four pounds of spinach per day or 3,000 calories of soybean oil. Researchers are hoping to increase our intake by tinkering with a gene that converts the less potent gamma form of vitamin E to the more potent alpha form in soybean, corn and canola oils.
Vitamin A Every year some 500,000 children in the developing world go blind because of vitamin A deficiency. Researchers are hoping to reduce this appalling statistic with the help of a gene from daffodils. This produces elevated levels of beta-carotene which are then converted to Vitamin A in the human body. Rice with this gene (called golden rice because of its color) has been crossed with local varieties of rice which are undergoing field trials and will hopefully be available to subsistence farmers in the near future. Work is also progressing on developing a similarly enhanced mustard which is grown widely in developing countries for its oil.
Access to iron Most people get too little iron, with almost one third of the world’s population believed to be anemic, and possibly around one fifth of all malnutrition deaths caused by a lack of iron. Scientist are working on a variety of rice that has a higher level of iron in the grain and also makes it more accessible. The amount of iron is doubled with the aid of a gene from the French bean, while accessibility is aided by two mechanisms. The first one involves a gene from fungus which counteracts a molecule called phytate that locks up about 95 percent of the iron in the plant. The second involves a gene from basmati rice which makes a protein that aids iron absorption in the human digestive system.
Food tolerance The vast majority of east Asians and blacks, and many whites are intolerant of cow’s milk. That’s because their bodies do not produce enough of the enzyme lactase, which is needed to digest the milk protein lactose. In France researchers are working to eliminate the problem by giving cows a gene that will cause them to manufacture their own lactase, which will be present in their milk.
Many people cannot eat wheat, oat, rye or barley products because the gluten makes them ill. Consequently, British researchers are working on a process to remove from gluten the part which causes illness while leaving the part that is important for baking.
As well as the nutritional benefits of genetically modified organisms, there are the medicinal.
Vaccines in food offer considerable promise for developing countries. Because they would be administered orally it would avoid the horrendous number of HIV and hepatitis B infections that are presently caused by unsafe injection. They would also be inexpensive and require no refrigeration. Potatoes, tomatoes, carrots, bananas and rice are being developed containing vaccines for a range of diseases including food borne E. Coli, cholera and hepatitis B.
A plant could possibly provide an edible form of immunotherapy for asthma. Tests with mice are promising. Consumption of engineered lupin plants that contained an asthma allergen from sunflower seeds protected the mice from a large otherwise asthma-inducing dose of the allergen in the air.
Genetically modified plants, bacteria and animals are being turned into little factories churning out cheap ingredients such as proteins, enzymes and hormones for the pharmaceutical industry. The diseases being treated so far include hemophilia, cystic fibrosis and multiple sclerosis.
Menaces can be neutralized. For example a ryegrass is being develop with less hay fever allergens in its pollen and work has been done that may lead one day to a malaria resistant mosquito. Also, new friends can be made, such as a gene-altered microbe that when applied to the mouth elbows out bacteria that cause tooth decay, animals with tissue and organs suitable for human use and plants that change color in the presence of landmines.
GM crops are accused of posing a number of environmental risks. There is said to be a danger from gene flows which can create “super weeds” in the wild and “genetic contamination” of other crops. Also US Bt crops have been accused of endangering the monarch butterfly.
Critics raise the specter of genetically enhanced crops breeding with wild relatives to create a ‘super weed’ that could overwhelm the natural environment and curtail genetic diversity both among plants in general and among the existing wild varieties that provide the ‘gene pool’ for breeding better commercial varieties.
The first question to ask is how likely is such inter-breeding? To begin with, there needs to be wild relatives in the region. This rules out wheat, corn, soybean, cotton and potato in most places where they are grown. The main possible concerns would be rice in Asia and Africa, corn and potatoes in Mexico and Central America, wheat in the Middle East and soybean in Korea and China
The proximity of related species does not necessarily mean that they will inter-breed. They need to flower at the same time, share the same insect pollinator (if insect-pollinated) and be close enough for the transfer of viable pollen. The latter can easily be thwarted by creating a buffer zone planted with traditional crop varieties to minimize any possible effects of pollen flow to a neighboring farmer’s field or to a wild plant relative.
Would a trait provide a selective advantage? Some traits are obviously not a risk. For example, tolerance to a particular herbicide is not likely to confer an advantage to a plant in the wild because the herbicide is not encountered there. If the weed becomes a problem on farms or areas of human settlement, it can be controlled with some other herbicide. Other traits – such as resistance to pests or disease, or tolerance of hostile growing conditions such as drought or poor soil – could theoretically give a weedy relative an advantage. However, the likelihood is diminished when we keep in mind that wild plants by their nature are already stress tolerant. If they were not they would simply die out. Domesticated plants on the other hand have lost much of the hardiness of their ancestors. Farmers select for edible yield while making up for any drop in stress tolerance by a range of farm practices such as irrigation, soil improvement and pest control. Any reintroduced stress tolerance would have to be quite strong to compete with the wild varieties. One example is sunflower which has been given a gene from wheat to resist white mould. If this genetically modified variety were introduced, gene flow would be inevitable because the crop is grown in the same regions as the wild varieties. However, it would have very little effect because the latter already have resistance to white mould.
It should also be kept in mind that the risk faced is identical to the risk from domestic plants bred conventionally for stress tolerance. Ironically, genetic engineering opens up a number of ways of ruling out gene flow. One approach is to incorporate what has been called a ‘terminator’ gene into the plant which renders it sterile while another approach involves passing on the attribute on the maternal side and hence not transmitted through the pollen.
Similar to the ‘super weed’ ruckus was the one made over the claimed appearance of genes from genetically modified maize in Mexican landraces. This was dubbed ‘genetic contamination’. Landraces are the varieties developed by small-scale farmers over the centuries and have evolved through selection to thrive under particular environmental conditions and to meet local food preferences.
It was finally determined that the claim was unfounded. However, if indeed there had been a gene transfer it would have been no different in nature from those involving conventional modern varieties. These have been occurring for may decades without causing any problems. If plants are superior from the farmers point of view, their seeds will be retained. If they are inferior they will not be.
Opponents of GM crops have made a big deal out of a supposed threat to monarch butterflies from Bt crops. It is something of an enviro icon, and no anti GM rally is complete without the presence a number of eco-bubble-brains dressed up as butterflies. The kafuffle started when the journal Nature in 1999 published a paper by Dr. John Losey of Cornell University showing the toxic effects when monarch butterfly larvae in a laboratory study were fed their favorite food, milkweed, covered with pollen from Bt corn.
A number of objections have been raised to the study. To begin with, only one type of Bt corn pollen was tested from among the many types of Bt corn in use. Recent studies indicate that a few types of Bt corn pollen may kill or slow the growth of monarch caterpillars, while other types of Bt pollen have no harmful effect.
More importantly, the laboratory results were in no way indicative of the real world risks to the butterfly. In the field, the risks to the larvae are minimal for a range of reasons: corn pollen is produced for only a short time during the growing season; farmers control milkweed in and around their fields, just as they control other weeds; corn pollen is heavy and is not blown far from corn fields by the wind; and even if milkweed were within a few meters of cornfields, pollen density on the leaves would not be high enough to pose a danger
The EPA, a body that is more often than not the greeny’s friend has given Bt crops a clean bill of health. After evaluating the evidence, the EPA concluded that the scientific evidence demonstrates that Bt corn does not impact on monarch butterfly populations and that a hazard in the laboratory does not translate into a risk in nature. Finally, if there had been a problem with Bt corn it would be resolved by varieties currently being developed that only express Bt in the stalk. Only insects that actually attack the plant would have any possibility of being affected.
Often ignored are the environmental benefits of GM crops. These include reducing impacts on the environment and providing remedies for past damage.
The insect resistance of Bt crops has lead to a greatly reduced use of pesticide. US corn growers, for example, have reduced pesticide treatment for the European corn borer by about a third and according to one projection the use of pesticide in the corn crop will drop by 70 per cent once resistance to corn rootworm is also incorporated into seeds. It has been reported that Chinese farmers of Bt cotton have slashed their use of pesticides by about 80 percent. In Australia, pesticide use on Bt cotton crops was about half that on conventional crops, and with a newly released version, trials suggest a 75 per cent reduction. In India the use of Bt cotton has cut pesticide spraying by two thirds. The recently announced blight resistant potato promises large reductions in the use of fungicide and insecticide, given the high levels currently used to control the disease.
The adoption of herbicide resistant crops is also leading to a more environmentally friendly herbicide regime. Because the crop is resistant to it, a post-emergent herbicide can be sprayed over the crop killing any weeds that may have sprouted. The herbicide used – glyphosate with the trade name Roundup – is required in lower quantities because it kills such a wide range of weeds replacing the need to use a multitude of herbicides. It is also environmentally quite benign. It has extremely low toxicity to people and animals. It also binds well to the soil until it completely deteriorates, so there is very little that can run off into water supplies.
Because herbicide resistance allows for crops to be sprayed after they have been planted, herbicides can more effectively control weeds so reducing the need to till the soil for that purpose.
Reduced tillage has a range of benefits in terms of conserving agricultural resources and the environment generally. It dramatically reduces soil erosion which affects fertility and clogs up rivers and streams, carrying pesticides and fertilizer with it. The crop mulch shades the ground and slows evaporation and the improved soil structure resulting from less plowing actually increases the movement of water into the soil following rain or irrigation and holds it there, which means less irrigation is necessary. Low tillage also means less tractor passes and less fuel consumption. According to one study no-till saves on average about 3.9 gallons of fuel per acre. Studies by groups such as the Conservation Technology Information Center and the American Soybean Association all attest to the fact that herbicide resistant crops have significantly encouraged the use of low till methods.
A primary objective of GM crops is to increase yields, and to the extent that they succeed they lessen the demand for resources such as land, water and energy and leave more land for wildlife. In the case of the crops that have been used to date, the gains have been through significantly reducing the losses caused by weeds and pests.
Genetic engineering is about to bring a revolution in bioremediation. This is the use of organisms to remove contaminants from water and soil. University of Georgia researchers have modified a poplar tree which can suck mercury from the soil with the help of a bacteria gene which bestows a tenfold increase in mercury tolerance. Another group of researchers have added a gene from the E. Coli bacteria and another from soybeans to make a distant relative of cabbage into a connoisseur of arsenic. The plant pumps arsenic from the soil and stores it in its leaves, where it can be easily harvested and disposed of. Biologists at the University of California at San Diego modified a relative of the mustard plant so that it sucks up various heavy metals into its stems and leaves. These include lead, arsenic, mercury and cadmium. At the University of Washington researchers have inserted a mammalian liver enzyme into a tobacco plant enabling it to absorb and degrade a variety of chemicals including the most widespread ground water contaminants called chlorinated solvents And researchers at Ohio State University have engineered a form of algae to make it extract copper, zinc, lead, nickel, cadmium and mercury, and other metals from contaminated water.
While the prospects are good for more productive plants and livestock, will achievements in these areas simply be compensating for a decline in the land resource base rather than actually increasing output? This will mainly depend on the following factors which we will discuss in turn:
· the amount of extra land that can be brought into crop growing;
· the encroachment of the built environment onto cropland; and
· the extent of soil degradation which either makes land unusable or seriously reduces yields.
How much extra land could be opened up to crop production? It has been estimated that the 1.5 billion hectares currently used for crop land represents about 36 per cent of the land that is to some degree suitable for that purpose.  In other words, there is an extra 2.7 billion hectares. This gives a total of 4.2 billion hectares which is about a third of the non-ice-covered land area. The remaining 9 billion hectares or so is excluded mainly because of unsuitable soil and/or climate.
Of course, most of this extra 2.7 billion hectares would never become available. Some of it is covered in human settlement or is too inaccessible, while a large part is taken up with forests and other natural areas that are (or should be) mainly committed to uses in their existing state such as conservation, water catchment and timber.
However, it only requires a relatively small proportion of this area to be available and of reasonable quality for it to represent a significant addition to crop area. According to Buningh and Dudal (1987), out of a total forest land of 4.1 billion hectares, 100 million had high crop potential and 300 million had medium potential. While out of 3 billion hectares of grasslands, 200 million have high crop potential and 300 million have medium potential. With current crop land at around 1.5 billion hectares, a few hundred million would be a significant addition. This includes some of the old cropland in places such as North America, Europe and Argentina which could be returned to use if costs were lower or prices higher. Of course, in the case of land currently used for grazing, one would have to take into account the loss of livestock production.
Then we have large areas which are presently not used because of degradation or natural infertility but which could be brought into use with improved soil management methods and new crops that can tolerate the poor soil. These include the large areas with acid soils, particularly in South America and central Africa and also some of the land that is very saline either naturally or through human mismanagement.
Next we have good land which up till now has been unus-able because of the lack of fresh water. This could be brought into use by the desalination of sea water and brackish groundwater. This process, which is discussed in more detail in the section on water resources, is getting cheaper by the day with new innovations and industry maturity.
So overall, there seem to be good reasons to conclude that, while there are not the vast virgin lands of yesteryear, the extra land still available will nevertheless provide a sizeable cushion against the impact of increased human settlement and soil degradation. In fact these would have to be quite large in order to actually reduce the land resource base.
Encroachment on crop land by the built environment is primarily an issue for developing countries and the US. Developing countries will house 90 per cent of the population increase expected over the next half century and at the same time will undergo a great deal of space consuming economic development. The US is the only major developed region expected to undergo a population increase in the foreseeable future, due mainly to high immigration and high fertility rates among immigrants.
Europe is expected to shrink from its present 726 million to 632 million in 2050, opening up the prospect that the area under built environment may actually decline and the availability of cropland increase.
The FAO estimates that on average people in developing countries use about 0.04 hectares of built environment per head. With the population expanding by two billion or so by 2025, an extra 80 million hectares would be required by then. If this were all cropland it would represent 5 per cent of the total. By the time the population reaches 9-10 billion mid century the increase between now and then would be 120-160 million hectares. This would be 8-10 per cent of total cropland.
Of course not all of this will in fact be suitable for crops or be premium grade if it is. Nevertheless, it is probably correct to assume that a significant proportion would be, given that urban centers are often sited on fertile agricultural land in coastal plains or river valleys. Alexandratos surmises that about 60 per cent of any increase would be on potentially arable land. This would include both actual cropland and land that could be useable. So this would mean 3 per cent being taken out by 2025 and around 5 or 6 per cent by 2050.
With the rate of urbanization increasing during this period, a growing proportion of the expansion in the built environment will take the form of urban expansion. According to one study, for all developing countries, the annual loss of arable land transformed to urban uses due to expanding urban populations is estimated at 476,000 hectares. This is 12 million hectares over 25 years and 24 million over 50 years.
When looking at urban expansion in developing countries, it needs to be kept in mind that a significant proportion of urban land is still used for agriculture by households, for example, 28 per cent of Beijing and 60 per cent of Bangkok. These urban activities can take many forms:
Horticulture takes place in home sites, parks, rights- of- way, roof tops, containers, wet lands, and green houses. Live stock are produced in zero-grazing systems, rights-of-way, hill sides, coops, peri-urban areas, and open spaces. Agro forestry is practiced using street trees, home sites, steep slopes, within vine yards, green belts, wet lands, orchards, forest parks, and hedge rows. Aquaculture is practiced in ponds, streams, cages, estuaries, sewerage tanks, lagoons, and wet lands. Food crops are grown in home sites, vacant building lots, rights-of-way for electric lines, schoolyards, churchyards, and the unbuilt land around factories, ports, airports, and hospitals.
Another thing to keep in mind is that in many places there is going to be an absolute drop in the rural population, and the corresponding decline in rural settlement will free up some land for crops.
In the US, the total developed area, including non-urban infrastructure, was estimated at 5.2 per cent of the total in 1997. That is 48.4 million hectares or 0.17 hectares per head. With the US population expected (on the most likely assumptions) to increase by another 100 million over the next half century that would mean another 17.2 million hectares assuming the average area per head remains the same.
US cropland covers 455 million acres (182 million hectares). If all of the increase in developed area were on cropland, it would represent a 9 per cent reduction in the latter. However, that is not likely to be the case given that many fast growing areas such as Florida and Arizona are not areas with high concentrations of prime crop land.
Curiously the rural population in the US takes up a lot of residential land. In 1997 this was estimated to be 73 million acres (30 million hectares), typically 8 hectares or larger for each household. Presumably a significant proportion of this could be placed under crops if costs were lower or prices higher.
So, to sum up, while the encroachments by human settlement are bound to be significant, they will not be on a scale that will make them a threat to food security. This is particularly so when we keep in mind that the process is gradual and that much of the increase will be a generation or two away, at a time when agriculture should be much more productive than it is now.
The next question is whether continuing soil degradation is going to seriously undermine agriculture’s resource base. Farming practices can harm the soil in a range of ways. Water and wind erosion cover the biggest areas, and is the main problem for rain-fed cropland. For irrigated land, the main concern is increasing soil salinity. Other significant forms of degradation include loss of organic matter and nutrient depletion.
Erosion occurs where soil is dislodged and removed by water or wind. The impact of any level of erosion on productivity will depend on the depth of the topsoil. Salinity is caused by excessive irrigation and poor drainage leading to the build up in the soil of salt left there by evaporating water. Nutrient depletion is due to insufficient application of fertilizer or to applications in the wrong proportion. Low levels of organic matter lead to a degradation of physical properties of the soil so that it loses the ability to hold water, and to retain and release nutrients.
The extent of degradation is not well understood. There is a serious lack of detailed studies and conflicting interpretations of what is known. For example, in the case of India, estimates by different public authorities vary from 53 million up to 239 million hectares.
Notwithstanding this uncertainty, there is general agreement that while soil degradation is a major problem most land is not seriously affected. Studies reviewed by Scherr suggest that soil quality on three-quarters of the world’s agricultural land has been relatively stable since the middle of the twentieth century. Also, at least to this stage soil degradation has not had a serious overall impact on crop productivity.
Of particular importance is the fact that degradation is not a serious constraint on food production in the temperate regions of the world. These include most of North America and Europe. Their soils are the result of glaciation in the last Ice Age, are deep and fertile and are fairly resistant to degradation. And they are better managed by modern agriculture.
Furthermore, a lot of soil degradation is on lands that while extensive in area are not major contributors to total food production because of inherently poor growing conditions. The climate or terrain is unsuitable and the soil is inherently of low fertility.
Soil degradation has also had its share of alarmism. During the 1970s and 1980s, so-called desertification received a great deal of attention. It was believed that deserts such as the Sahara were spreading irreversibly. However, since then remote sensing has established that desert margins ebb and flow with changes in the climate and studies have revealed the resilience of crop and livestock systems and the adaptability of farmers and herders. In the case of wind erosion in North America, past concerns showed insufficient recognition of the fact that erosion usually involves soil being blown from one field or farm to another and hence no loss to agriculture. According to Crosson and Anderson, US studies have found very small long-term yield effects due to erosion. They indicate that if erosion rates were to continue at the same rate as in 1982 for 100 years, national average yields in the US would only be reduced by be 3-10 percent. 
Arguably the main soil problems are (1) salinity and the excessive use of nitrogen relative to other nutrients in a lot of irrigated farming in Asia and (2) the grossly inadequate use of fertilizer of any kind in Sub-Saharan Africa.
There are a range of countermeasures that can be taken against degradation. In some cases problems can be remedied and in others preventive measures adopted to avert or retard further damage.
To a considerable extent the ability to take effective preventive and remedial action depends on technical capacity which in turn is a function of the level of modernization and the stage reached by science and technology. Where agriculture is backward, many soil and land management measures are not possible because there is not the access to the knowledge, infrastructure, inputs and equipment made possible by modern science and industrial development. Backwardness limits knowledge of the soil and its vulnerabilities and the ability to keep track of and analyze any changes in its condition. There are not the resources to carry out measures such as earth movement to prevent erosion and better irrigation systems to reduce salinity.
A change of institutional or political conditions will in many cases also make a major difference. Land management and agriculture generally will benefit if there is a government that is willing and able to progressively increase infrastructure, extension services and research and does not simply see agriculture as something to be taxed for the benefit of the ruling elite and its urban support base. A change in the incentives facing farmers in developing countries would also improve how they respond to the problem. Greater land ownership among farmers would mean a greater willingness to invest in measures to conserve land because their future rights to use it are more secure. And ending the common policy of subsidizing water and nitrogen would also assist in the battle with salinity and nutrient problems. Funding of research is critical in soil management as with other aspects of agriculture.
Below we look at the main forms of degradation and the measures that can be adopted to deal with them.
Wind and water erosion can be prevented by a range of measures. The movement of wind and water can be impeded or diverted by planting trees, hedgerows and grass strips and the construction of terraces and storm water drains. And, as we mentioned above, the soil can be protected by conservation tillage which minimizes disruption of the soil surface and maintains a cover of plants or plant litter.
Estimates of the rate at which land is being seriously impaired by salinity vary considerably. One claims that 0.5 million hectares per year are being affected while another claims 2 million hectares.
Measures to prevent the problem include additional drainage, better canal lining or use of pipes, and more judicious water applications. Remedial action can also be taken where the problem has emerged. Planting salt tolerant trees and grasses, which “suck up” the salt, is one approach, and plants are being bred that are particularly suited to this job. Another approach which can be applied in some cases is to lower the water-table below the root zone and flush the salts away to newly constructed subsurface drainage systems. According to Conway writing in the mid 1990s, the cost of doing this in India was of the order of $325-$500/ha.
For loss of organic matter, the answer often lies in leaving more of the crop residue in the field and making greater use of livestock dung. However, in many parts of the developing world these are used for fuel, so improvement may have to await ready access to modern energy sources such as electricity and fossil fuel.
In some particularly backward regions, especially Sub-Saharan Africa, only further economic developed and higher incomes will end what is often referred to as nutrient mining, where nutrients taken from the soil either by plants or leaching are not replaced by adequate applications of fertilizer. In this region fertilizer use per hectare is only about 10 per cent of the global average and will have to increase about four times to meet nutrient needs at the current level of production. Generally more nitrogen is required than potassium, and more potassium than phosphorus. Prices for fertilizer are high because of inefficient local production, high shipping costs for imports and poor transport. Where transport is particularly poor fertilizer is simply not available. And most farmers could not afford it even if it were delivered to their door at world prices.
In other areas such as China and India nutrient mining occurs even though relatively high amounts of fertilizer are used. This is because the mix is not in the right proportions for the plants’ needs. Given that plants use nutrients in a certain proportion to each other, the increase in the external supply of one nutrient, enables plants to extract more of the natural supply of the other nutrients in the soil. The main problem is the overuse of nitrogen relative to the other macronutrients, phosphorous and potassium and to micronutrients such as sulfur and zinc.
Farmers needs a change in incentives so that they are less drawn to the short term gains from nitrogen use and are more heedful of the longer term effects of nutrient depletion. This requires reduced poverty so that they are not living hand to mouth, changes in property rights so that they have more of a stake in the future productivity of the land and an end to the common practice of subsidizing nitrogen. Better knowledge would also assist. This requires a greater general appreciation of the problem by farmers and the means to carry out necessary soil testing and plant analysis.
So to sum up on the state of the land resource, the evidence indicates firstly, that there is still a significant amount of extra new land available; and secondly, that recent degradation has not been enough to significantly slow down average crop yield increases and large areas are not seriously affected. While this does not rule out the presence of a real and increasing problem, it does suggest that the resource as a whole is not in imminent, grave danger. Whether the situation improves or deteriorates in the future will depend on the extent that remedial and preventive measures are applied, and this in turn depends mainly on the pace of economic and social progress.
The other major resource required by agriculture is water. As with land, there are concerns about whether the resource will be sufficient to meet our food needs. This will depend on the following factors:
· how far we can increase our use of rain, rivers, lakes and groundwater;
· how well we can stem or reverse the depletion or degradation of presently exploited resources;
· the extent that we can become more efficient in our use of water, both in food production and in other activities that compete with agriculture for water; and
· the prospects for tapping into the non-conventional resources, namely salty water and polar ice.
Some regions get all the water they need from the rain that falls on the field (green water). For others rain water is insufficient or at the wrong time. They have to rely on water brought in from elsewhere (usually by rivers) or local rainwater which has been stored in aquifers, dams and lakes (blue water). This is drawn off and distributed by irrigation systems.
Presently around 280 million hectares are under irrigation. Over 70 per cent of this area is in developing countries, which are often in regions that are either arid or have monsoons that bring the rain all at once. China and India have about 20 per cent each.
There is scope to expand this area significantly, although by how much is open to some dispute. Presently about 10 per cent of blue water is diverted or pumped for human use. Much of the remainder is unavailable for a range of reasons. For example, rivers run through regions unsuited to farming or the local farmland has all the water it needs, and some water is required for navigation and environmental flows. The FAO has published what some consider an upbeat estimate of 200 million hectares of extra irrigated land in developing countries. What we cannot possibly expect to achieve is the kind of expansion that occurred over the last 50 years when withdrawals were doubled and the area of irrigation increased two and a half fold.
Part of any expansion, will have to make up for some deterioration in existing systems. Each year infrastructure becomes more dilapidated, more silt builds up in reservoirs, and aquifers become more depleted and in some cases mined out.
Turning these problems around will be one of the objectives of political and economic development over coming decades. The level of infrastructure investment in both rejuvenation and expansion will need to increase considerably from what it is at present. Ensuring that schemes are properly maintained will also require a revolution in management which is generally incompetent and corrupt.
Moves are afoot in many countries to reform their systems. This includes greater accountability for performance and participation by farmers in various aspects of management, separation of service delivery from regulatory functions, and contracting out of operations and maintenance tasks to the private sector or non-government organizations.
The depletion of aquifers is a serious problem in some areas including many parts of India, China and the United States. How important are they? It has been claimed that 10 per cent of the world’s food production is dependent on aquifers that are being depleted. Over-drawing of groundwater was estimated to have been 200 cubic kilometers in 1995, 8 per cent of withdrawals by agriculture. On the assumption of equal water productivity this over-drawing would provide about 4 per cent of food given that irrigated land as a whole provides 40 per cent. However, because groundwater irrigation is more reliable than surface irrigation its contribution will be higher than that.
The main problem with most aquifers is that there is no regulation of their use. They are a common pool resource and any individual farmer can drill a hole and install a cheap pump. This is compounded by the fact that in many countries farmers have managed to obtain large subsidies for electricity and diesel fuel, the biggest recurrent pumping costs. Governments will have to bite the bullet and take on the politically difficult task of removing these subsidies. Access to the resource also has to be regulated. One approach is to provide farmers with a right to a certain quota which would be assigned once a study had determined what was a sustainable level of total use or acceptable level of depletion. Farmers who pump more than their quota would then be either charged very high prices or forced to buy pumping rights on an open market from others not using their full entitlement.
On the supply side, depletion can be addressed by taking measures to increase the rate of aquifer recharging by various ‘water harvesting’ techniques which capture some of the rainwater which presently evaporates. These include containing the water behind dams, or in ponds so that much of it can be absorbed into the ground or digging recharge wells or cisterns that drain water from surrounding higher ground. The water captured would include floodwaters that do not flow into streams and rainwater that falls on areas other than cropland such as pasture and wasteland. One particular proposal is to encourage, through subsidies if necessary, flooded paddy rice cultivation in lands above the most threatened aquifers in the wet season. At this stage it is not known how far artificial recharge measures could go in countering large scale depletion.
An alternative to increased water supply is increased efficiency in use. Doubling the output from a given amount of water is just as good as doubling the amount of water. There are many ways that farmers can get more crop from each drop of water applied to the field. These can be divided into measures that increase the efficiency of water application in the field and measures that increase the plants response to water.
The two traditional methods of water distribution that still dominate irrigation in most countries are flood irrigation which covers the whole field with a layer of water and furrow irrigation which channels water from ditches to crops along slightly inclined parallel rows. With these methods significant amounts of water are lost to evaporation, leaching or runoff. Better methods from this point of view are sprinklers, and drip irrigation where the water is delivered by pipes running along the surface or underground near the roots. To date these new methods have not been widely adopted. Although where they have, the results have been dramatic. Cyprus and Israel are leading examples and show that they can be put to widespread use.
Field management measures can ensure that both irrigation and rain water are better used. Increased crop residues or ground cover, made possible with low till techniques, helps retain water or melting snow that would otherwise runoff or evaporate. Increased level of organic matter in the soil increases its ability to absorb and retain moisture. Land leveling, with the help of cheap laser technology, can benefit both irrigated and rain-fed agriculture by reducing run-off and ensuring that water is distributed evenly. It has been reported that field leveling in a region of Arizona lead to a water use decline of between 20 and 32 percent and yield increases from 12 to 22 percent.
Water efficiency can also be improved by increasing our knowledge of the plant’s water requirements at various stages in its growth. This knowledge can be combined with equipment monitoring the field for information about soil moisture and the condition of the crop. This can even be used to trigger water applications. Measuring soil moisture can be performed by fairly simple and inexpensive devices such as gypsum blocks containing two electrodes which are buried at several locations and depths in root zones. A pocket-size impedance meter can then measure changes in moisture content.
Of course, harnessing the water and applying it to the land as efficiently as possible is only half the story. The ultimate measure of efficiency is the final harvest achieved. This will also depend on the choice of plant varieties and measures taken by the farmer to maintain soil quality and to protect the crop from various stresses.
The development of plant varieties that put more of their effort into producing grain rather than stalks or leaves, or that speed up or bring forward the grain growing phase will mean more final output for a given amount of water. Likewise, having plants that cope better under stress means less water is wasted on plants that end up dying or underperforming.
Water efficiency can also be improved by using plants that require less water. We can switch to less thirsty crops. For example, growing sorghum instead of corn as stock feed would lower water needs by 10-15 percent and sunflowers instead of soybeans as an oil crop would reduce water by 20-25 percent. Or we can breed plant varieties that require less water. This includes plants that can grow in drier areas where nothing of interest could grow before. Another approach is to develop plant varieties that are more tolerant of saline water hence creating a water resource out of what was otherwise unusable.
These methods of increased efficiency in water use should take us a long way to ensuring that the water supply is sufficient for our needs. An important impetus to greater efficiency would be an end to the heavy subsidizing of water through under-pricing. At the moment prices are generally nominal and collection rates low.
Agriculture can expect to face increasing competition for water from non-agricultural uses. At the moment they make up about 30 per cent of withdrawals – about 20 per cent for industry and 10 per cent for municipal use. This demand will increase in developing countries as their populations and economies grow. However, there is much that can be done to keep non-agricultural uses of water in check.
Having a water system that does not leak is a good start. In many cities in developing countries a large proportion of water is lost to leaks in the system because of poor maintenance.
Another part of the solution is to achieve most outcomes using less or even no water. For cooling in electricity generation, water-free technologies can be used such as dry cooling towers. In production, innovation can bring forth new water saving technologies. For example, at the Oberti olive plant in Madera, California, where water is used in the curing process, they almost halved water use by reducing curing time from seven days to three. Consumers can have the same need met with a less water intensive product. For example, reading the news on the Net requires no water whereas producing the paper used in the traditional tabloid or broadsheet requires a considerable amount.
It is not hard to imagine a whole range of innovations that could reduce water consumption in the home. Water-saving shower heads could be more widely used. Toilets that use little or no water could significantly reduce domestic consumption. A waterless, electrically powered toilet has been developed which has no odors or insect problems, and safely and effectively biodegrades human wastes into water, carbon dioxide and a soil-like residue. Fumento cites the case of a new train toilet which sanitizes the waste and returns water for flushing and hand washing:
Something called a macerator chews up waste and feeds it into an aerated tank containing membranes coated with muck munching bacteria. The solids are broken down primarily into carbon dioxide and water, while the gas is pumped off and bacteria free water passes across the membrane. Some of the water is sterilized with ultraviolet light and returned to the flushing tank. The rest goes through a reverse osmosis device that filters out the remaining chemicals, such as proteins and urea, so that the water is entirely microbe free and can be used for hand washing. This way the system needs servicing only once a month to remove built up sludge.
No doubt the computerized and automated kitchens of the future will be able to make more efficient use of water both in cooking and dishwashing. Future washing machines may work with less water or have their own recycling systems. There is even talk of waterless washing using nano-machinery that imitates the behavior of enzymes. It is also possible to imagine the development of fabrics that repel dirt and grease.
Reuse is another way of saving water. In some cases no treatment is required, e.g., washing or cooking water diverted to the garden or to the toilet cistern. In other cases various levels of treatment would be needed. For example, sewage and industrial effluent can be cleaned up using technologies that are now getting cheaper and more effective. This can be fed back into the municipal water supply or made available for specific uses.
San Diego is looking at a proposal to mix recycled sewage water with the city’s drinking water. The sewage water will undergo conventional tertiary and advanced treatment steps. Advanced treatment will include micro-filtration pretreatment, reverse osmosis, disinfection and nitrate removal. The re-purified water will then be blended with other local supplies. Upon withdrawal, the water undergoes final treatment including conventional coagulation, mixing, clarification, filtration and disinfection before introduction to the city’s pipelines.
Waste water can also be made available to agriculture. In water starved Israel, for example, well over half of waste water is used for irrigation after treatment and it makes up about 20 per cent of the irrigation total.
In many industrial activities, there is a great deal of scope for internal recycling. New water would only be needed as a top up where there are losses from evaporation or leakages, or the scale of operation is increased. A major user of water is the power industry for cooling. This is an area where far more recycling can be applied. Even in the sensitive area of food processing recycling seems to be an increasing option. The Californian olive processing plant previously mentioned reuses 80 per cent of its processing water with the aid of a membrane filtration system.
Households, municipalities and industry can also do more to harvest their own rain water. Rain water runoff that goes down drains can be better used. Rain can be collected from the roofs of houses, factories and other large buildings, and stored in tanks. The Frankfurt Airport terminal, for example, collects water from its vast roof for such low-grade water needs as cleaning, gardening, and flushing toilets.
So in a nutshell, households and industry can reduce their competition with agriculture by finding less water intensive ways of meeting their needs, by making more discarded water available to agriculture and by harvesting their own rain. All these approaches can be encouraged by having water charges that reflect the true cost of water and encourage more frugal use and the development of more water efficient technologies.
There are two non-conventional sources of fresh water that we need to consider: (1) desalinated sea water and briny groundwater; and (2) polar ice. They are non-conventional in the sense that they have only been tapped on a small scale and would require a considerable amount of technical development before they could play a bigger role. They would also require a lot more capital and energy than the conventional resources.
Seawater covers 70 per cent of the planet and comprises 95.5 per cent of all water. Brackish groundwater is found in vast underground aquifers throughout the world and often far inland in otherwise dry climates. It includes the vast supplies that accompany fossil fuel extraction.
So far desalination has only been put to limited use, because of the cost. Desalting capacity is about 32.4 million cubic meters (or 8.6 billion gallons) per day. This is a tiny fraction of our present fresh water consumption. About half of this capacity is installed in Persian Gulf countries where water from other sources is very limited and cheap energy to run the process is available. Desalination plants can also be found at specific locations, including island resorts, where there are no alternatives and the demand is sufficient at the high price to economically justify a facility. They are also sometimes used to bring slightly brackish water up to a standard where it can top up conventional supplies. Investment in new capacity appears to be quite healthy. In the US, for example, there are new large-scale facilities being built or planned in Southern Florida, Southern California and El Paso, Texas. The facility in Tampa Bay Florida is the largest desalination facility so far in that country, while San Diego hopes that planned facilities will provide 15 per cent of its water from the ocean by 2020.
Virtually all desalination capacity is provided either by thermal or membrane units. Each provides roughly half of capacity, although membrane technology is edging ahead. In the distillation process salt water is heated to boiling point to produce water vapor which is then condensed to form fresh water. In the membrane process the salt and water are physically separated. Electrodialysis (ED) uses voltage to separate the salts, whereas reverse osmosis (RO) uses water pressure. Most membrane facilities use RO while significantly less use ED. Generally, distillation and RO are used for seawater desalting, while low pressure RO and electrodialysis are used to desalt brackish water. Treating brackish water is far cheaper than treating seawater.
Costs have fallen significantly over the last decade and this is expected to continue. Like other industries, desalination has benefited from a range of advances such as better materials to choose from and improved computerized management of operations. Membranes are achieving faster flow rates, longer lifespan, less fouling and greater energy efficiency. At the same time their cost of manufacture is declining with increased automation. It is believed that a better understanding at the molecular level of the RO process will lead to faster flow rates and better salt rejection.
Completely new technologies may offer possibilities for much greater cost reductions. A number are already in view and expectations are that, with a greater research effort, others could be around the corner.
One at the early commercial stage is called the Rapid Spray Evaporation process which ejects water through a nozzle into a stream of heated air. Because the water is a fine mist it creates a vast surface area which allows the water to evaporate quickly, leaving behind salt in a dry form or as a supersaturated solution easily converted to sea salt. The company developing the technology, AquaSonic International, has at the time of writing started producing small portable units and is in the throws of developing the technology for large-scale plants.
A modified reverse osmosis process is being developed at New Mexico Tech. It uses cheap clay membranes that do not require the usual water pretreatment, operate under lower hydraulic pressure, produce a solid salt waste and yield 100 per cent water recovery.
Reassessing some of the many past failures in the light of subsequent advances in scientific and technical knowledge could prove fruitful. For example, knotty design problems may be sorted out with new computational modeling techniques and the technology made feasible with new materials and production processes.
Then there are totally new concepts. One that looks promising is a nanotube-based membrane. This is being developed by researchers at the Lawrence Livermore National Laboratory. A field of nanotubes functions as an array of pores which allows water molecules through, while keeping salt and other unwanted molecules at bay. And, despite their diminutive dimensions, these pores allow water to flow at faster rates for a given pressure compared with reverse osmosis membranes. This will mean that less energy will be required.
While desalination can expand the water resource, it does so by placing greater demands on other resources, particularly energy which it would use in large quantities even with considerable improvements. Our ability to meet our increasing energy and raw material needs is discussed in the next chapter.
Three quarters of the world’s fresh water is polar ice. It starts out either as snow or as seawater which loses its salt when it freezes. The quantities are enormous. There are tens of millions of cubic kilometers of ice. In comparison the 2500 cubic kilometers of water we withdraw for irrigation is miniscule.
At the moment ice exploitation is just a ’boutique’ industry catering to the bottled water and spirits market. Its appeal is that it is extremely pure and does not require the normal extensive range of treatments. A specially equipped ship comes along side of an Arctic iceberg located in a quiet cove and cuts off chunks which are then thawed. However, to ship quantities that make a significant contribution to our irrigation needs would require a massive fleet of supertankers. Just supplying 5 per cent of current levels would require over 700 deliveries per day by 500,000 tonne super tankers. Tankers moving the equivalent in water of our current oil consumption (i.e., 4.5 km3) would move less than 0.2 per cent of our present irrigation withdrawals.
Towing or nudging icebergs with the help of ocean currents is another option which has been discussed. These would have to come from the Antarctic because those from the Arctic are insufficient to make a big difference. Of course if you simply tried to tow an iceberg to Saudi Arabia or California, it would have melted away before it arrived. A number of solutions have been proposed to deal with this. One is to cut a bow into the front end and cover it with kevlar. This would reduce melting to acceptable levels. The iceberg would then be cut up and melted down, and the water piped to irrigation systems and reservoirs. Another approach which has been trialed is to seal the iceberg in reinforced plastic so that melting is no longer an issue.
Moving icebergs into unfamiliar territory could raise a range of environmental issues that would have to be taken into account. There may be an increased risk of oil spills in polar regions, however, these should be countered by better ship design and more effective clean-up methods. There may be some destinations or routes where icebergs would be unwelcome because of an excessive intrusion on the environment. Moving through shallow seas, an iceberg could cool down the surrounding waters or scrape the bottom, damaging marine life. Ice cold fresh water runoff would also reduce the salinity of the surrounding sea water and could precipitate a sudden change in temperature. The plastic bag solution is less likely to cause these problems because they would be smaller and the ice perhaps already melted before it arrived at problem spots, and no freshwater is released. However, given that the size of icebergs is typically no bigger than a tanker, one would be looking at a similar number of icebergs as tanker trips.
What about transporting thawed ice by pipeline? They would need to stretch for thousands of kilometers to the more arid regions and in the case of the Antarctic much of it would have to be underwater. There would also need to be many of them. The Baku-Tbilisi-Ceyhan pipeline from oil fields in the Caspian Sea to the Mediterranean Sea can carry one million barrels of oil per day. That is a lot of oil. However, that much water is nothing. It is 0.06 km3 per year, a minute fraction of total irrigation withdrawals. Even under pressure, a pipeline is only the equivalent of a small stream. It can never compare to a river.
So, in sum, at this stage it is difficult to foresee polar ice being an important contributor to our water supply.
There is a concern that modern agriculture is narrowing the genetic diversity of crops by replacing a large number of local varieties (landraces) with a small number of widely used modern high yield varieties (HYVs). It is claimed that this “genetic erosion” is eliminating much of the gene pool required for breeding various favorable traits and is making us more vulnerable in the face of new stresses. However, the evidence does not back up these claims.
Despite the popular belief to the contrary, HYVs retain a considerable amount of diversity. There are many varieties in use at any one time adapted to a range of conditions. Furthermore, the level of diversity has been increasing continuously over the past few decades as adaptations to specific stresses have been fine tuned. In the case of wheat there is actually a more diverse range of varieties in the field than at the beginning of the 20th century.
A considerable number of the traditional landraces are still in use, particularly in the areas from which the crops originated. In some regions they are still dominant, for example, rice in Sub-Saharan Africa and maize in West Asia/North Africa, Asia (excluding China), Sub-Saharan Africa, and Latin America. In the case of wheat, landraces are still grown extensively in parts of West Asia, North Africa, and Sub-Saharan Africa (Ethiopia and Sudan). West Asia, where much of agriculture originated is still home to a vast array of traditional varieties of the lesser crops such as lentils, oats, barley, rye, almonds, apricots, cherries, figs, grapes, olives and plums.
Arguably more important than landraces, particularly with improved breeding techniques, are the original wild varieties of domesticated plants. Because they survive without human care and protection they are generally more resistant to biotic and abiotic stresses. These will not be found in farmers fields but out in the wild.
If you include in diversity not only what is in the fields of farmers but also what is in the fields and greenhouses of research stations and in gene banks, there has been an improvement over time for both rice and wheat. This adds a number of other dimensions to diversity all of which have been increasing.
They include temporal diversity (average age and rate of replacement of cultivars); polygenic diversity (the pyramiding of multiple genes for resistance to provide longer-lasting protection from pathogens); and pedigree complexity (the number of landraces, pureline selections, and mutants that are ancestors of a released variety).
Something else to consider is effective diversity. Traditionally the diversity available to a farmer was confined to whatever was in the local region and what they could do with that was limited in the absence of modern plant breeding. Now we have breeding institutions that can pull germ plasm from anywhere in the world when breeding a new plant. They have speedier and more effective ways of screening for desirable traits and using them to create new commercial varieties. The greater effective diversity is evidenced by two facts. Firstly, traditional methods took millennia to greatly increase yields, while modern breeding methods have tripled them within a number of decades. Secondly, yields are far more stable from year to year than they used to be because modern varieties are more stress tolerant than their landrace predecessors. Finally with genetic engineering we have a further extension to diversity because it allows scientists to draw on the characteristics of totally unrelated life forms.
While not a major supplier of food energy, fish provide about one-sixth of all animal protein, and in developing countries the harvest nearly equals the combined local production of cattle, sheep, pigs and poultry. About 70 per cent of fish are caught while the rest are cultivated. About 30 per cent of caught fish are used for non-food purposes, mainly animal feed.
The catch has increased fivefold over the last 50 years. However, there does not seem to be much if any room for the fish catch to continue growing. The FAO anticipates a small increase if fisheries are better managed and a decline if they are not. They believe that between 70 and 80 per cent of fish stocks are fully exploited, overexploited, depleted or recovering from depletion.
Remedial measures include reducing the capacity of fishing fleets, setting up marine reserves, removing government subsidies and assigning property rights to individuals or groups of fishermen to provide an incentive for good stock-management practices. Other threats to coastal fisheries that have to be dealt with are pollution and degradation of coral reef and mangrove habitats.
Fish cultivation or aquaculture has prospects for significant expansion. At the moment output is concentrated on crustaceans and mollusks, freshwater carp in China and salmon. Around 80 per cent of mollusks are cultured, around 20 per cent of shrimps/prawns and around 33 per cent of salmon.
Growing fish in captivity instead of catching them is comparable to the move on the land from hunter-gathering to farming. This allows the development of better breeds and the adoption of management practices such as protection from other predators, provision of better feed and optimal timing of slaughter. While they have a long way to go to catch up with the changes that we have made on land, the industry has made some progress.
Tilapia, a freshwater, plant-eating fish popular in America, has been bred to be hardier and grow 60 per cent faster than the wild variety. Genetically modified salmon are being developed which possess a gene that protects them from freezing when raised in icy waters and a gene that expresses a growth hormone so they reach maturity more quickly, while requiring less food. Other areas of improvement being investigated by breeders include disease resistance and increased fertility. Feed suppliers have also had some success in improving feed efficiency. For example, the amount of feed used for growing salmon is 44 per cent of what it was 30 years ago.
As with any other human endeavor, aquaculture can have impacts on the environment that need to be checked. Chemicals, uneaten feed, dead fish and fish feces from inland and shoreline aquaculture has contaminated drinking and irrigation water, seeped into aquifers, and affected coastal fisheries. Where there is limited water exchange, the decomposition of organic waste can contribute to local eutrophication and all the environmental problems that can cause.
In intensive shrimp production about a third of the water has to be changed daily, and about half of it is fresh water needed to obtain the optimum salinity level. This call on freshwater can lead to a drop in groundwater levels; and large volume pumping of freshwater and seawater also affects the biodiversity of affected areas. Shrimp production has also caused extensive damage to wetlands and mangroves and the creation of infertile land through salinity.
Much of the remedy lies in improvements to the poor regulatory and institutional arrangements to be found in the developing countries involved. This is similar to logging where the government fails to properly protect land supposedly under its control.
Improved technologies and practices can make a difference. One area of success has been in the development of more digestible feed formulations that leach less waste into the environment. For example, nitrogen waste for a given quantity of salmon is one sixth of what it was thirty years ago. A shrimp farm in the US uses other fish to mop up shrimp waste. The use of antibiotics in Norwegian aquaculture is less than 0.5 per cent of what it was ten years ago. Vaccines have brought about great reductions in the use of antibiotics and other chemicals.
We can expect to see the greatest growth in fisheries out at sea where there is not the same competition for resources found on land or near the sea shore. This will take time to develop if only because of the lack of knowledge and new investment involved. The technology to pen, cage or otherwise control the fish still has to be designed and built; and to domesticate a new specie, knowledge is required of such matters as stocking densities, water quality, breeding conditions, animal behavior and precise nutritional requirements. For aquaculture to make a major impact on the food supply, there would have to be large scale investment in facilities such as pens or other means of controlling the fish.
Future cultured fisheries out at sea will face environmental problems similar to some of those above plus a range of new ones. One concern relates to ‘genetic pollution’ from domestic varieties breeding with wild ones. Like any environmental concern it would need to be assessed on the evidence on a case by case basis. However, given the option of breeding fish that cannot breed in the wild this will never be an overriding problem. Then we have the effect on wild species and ecosystems generally of building large pens and cages and concentrating large numbers of domesticated fish in a relatively small area. These are similar to the issues that we have faced and continue to face in land based food production.
One of the reasons modern agriculture is often slammed for being unsustainable is its use of non-renewable resources particularly inorganic fertilizer and fossil fuels. Inorganic fertilizer refers to the three macronutrients when obtained from outside agriculture, in other words, not from the recycling of organic matter. Nitrogen is the most important followed by phosphorous and potassium. Fossil fuels are important mainly in the production of nitrogen and as fuel for farm machinery.
Inorganic nitrogen fertilizer is produced primarily from synthetic ammonia which is obtained by combining nitrogen and hydrogen. The ammonia is then used to produce various synthetic nitrogen fertilizers including the most common one, urea. Nitrogen makes up almost 80 per cent of the atmosphere (and much of the nitrogen not in the atmosphere eventually returns to it) while hydrogen is the most abundant element in the universe.
Natural gas is presently the most commonly used fossil resource input, both as the source of hydrogen and for the energy in the production process. According to estimates from the late 1990s, if natural gas had provided all the feedstock for hydrogen and all the fuel, its total consumption would have been just under 7 per cent of the world’s natural gas extraction.
Nitrogen fertilizer production is certainly very energy intensive, however, as discussed in the next chapter, a diverse range of options will allow us to meet our energy needs. The next chapter also examines the prospects for using water as a hydrogen feedstock instead of hydrocarbons. (Hydrogen is the H in H2O.)
Phosphate fertilizer is made from phosphate rock treated with sulfuric acid. Commercially viable reserves of phosphate rock are estimated to be 18 billion tonnes. This would last 60 years if we consumed at twice our present annual level of 148 million tonnes. The reserve base is estimated to be 50 billion tonnes. This also includes explored resources which are presently non-economic or would require at least some use of unproven technology. Assuming the same rate of consumption these would last 170 years.
With further exploration we should expect discoveries of extensive new deposits in the future. Furthermore, large phosphate resources have been identified on the continental shelves and on seamounts in the Atlantic Ocean and the Pacific Ocean. These cannot be recovered economically at the moment but this could change with new technologies.
The sulfur in evaporite and volcanic deposits, and that associated with natural gas, petroleum, tar sands, and metal sulfides amount to about 5 billion tons. At double current usage rates of 59 million tons a year, these would last 65 years. The sulfur in gypsum and anhydrite is almost limitless, and some 600 billion tons is contained in coal, oil shale, and shale rich in organic matter.
Commercially viable reserves of potash or potassium oxide are estimated to be 8.3 billion tonnes and the total reserve base 17 billion tonnes. At double current usage rates of 31 million tons a year, these would last 170 and 350 years respectively. The estimate for the total known resource is 250 billion tonnes.
Farm machinery takes a very small share of fuel consumption. US agricultural field machinery consumes annually no more than 1 percent of the country’s liquid fuels. In terms of resource use it is a vast improvement on draft animals. Using grass as a fuel is extremely land intensive. In the US, the shift from draft animals to internal combustion engines released 30 million acres of prime arable land for crops. To match the 1995 mechanical power of American tractors with horses would require at least 250 million of these animals and 300 million hectares, or twice the total of US arable land, to feed them.
While we can be optimistic about everybody being fed as a result of advances in the agricultural sciences and the modernization of Third World agriculture, we cannot be the same about the ‘alternative’ agriculture espoused by the greens. With their alternative we would not be able to feed ourselves and we would trash all remaining natural habitats in the futile attempt. This alternative would have us do without ‘unnatural’ things such as inorganic fertilizer, chemical pesticides and genetic engineering.
Instead of getting nitrogen from the air as we mainly do now, we would have to confine ourselves to getting it in ‘natural’ ways such as from animal manure, human sewage and ‘green manure’ legumes. At the moment inorganic nitrogen provides the bulk of our needs so there would be a big shortfall to fill.
Organic enthusiasts reassure us that there is lots of potential organic fertilizer that we could be using. According to them there is lots of animal manure, crop residue, urban sewage and compostable landfill going to waste. However, experts at the USDA have calculated that the available animal manure and sustainable biomass resources in the US would provide only about one-third of the plant nutrients needed to support current food production. What about using urban sewage sludge more broadly on crops? In the US, all of the urban sewage equals only 2 percent of the nitrogen currently being applied in commercial fertilizers and a significant proportion is already being used for agricultural fertilizer. What about compostable materials from current urban landfill waste? Any urban waste would only be a small addition to the manure and other farm waste already being used by farmers in the US and elsewhere.
The only ‘unlimited’ source of nitrogen for organic farmers is ‘green manure’ legumes grown in a crop rotation to provide nitrogen for subsequent crops. However, land put aside for this purpose is not available for crop production. So the land taken up both directly and indirectly for a given quantity of crop output is increased. In any year a significant proportion of the land is not taken up with growing final crops but rather with growing manure! So even if the yields in the fields growing the final crop were the same as for modern sensible agriculture, the average for cropland as a whole is going to be far less.
There is a similar story with chemical pesticides. If you let insects eat part of your crop rather than use pesticide, you need more land for a given crop. Pesticide is not always the only remedy for pests and in some cases if wrongly or over used can make the pest problem worse. However, this does not negate the fact that in most cases there is no substitute for chemical pest control. Furthermore, other measures tend to be adjuncts to pesticide use rather than substitutes. A study by Texas A&M University indicates that U. S. field crop yields would decline drastically if farmers in that country substituted the currently available organic pest controls for synthetic pesticides. Soybean yields would drop by 37 percent, wheat by 38 percent, cotton by 62 percent, rice by 63 percent, peanuts by 78 percent, and field corn by 53 percent.
Other productivity reducing and resource wasting practices of organic farmers include foregoing the use of antibiotics and growth hormones for livestock and the use of genetic engineering.
The exponents of ‘alternative’ agriculture also tend to have a strong, low-tech streak to them. Machines are seen as unnatural and dehumanizing, and their use is destroying the planet. In a similar vein, the small farmer is the hero and agribusiness the demon. Once again this is at odds with efforts to economize on the use of land and water. Two examples should make the point, namely, the present move to precision farming and the prospect some time in the future of factory farming.
The first of these technologies will allow farmers to micro-manage each separate patch of ground. Its particular stresses can be detected and specific solutions applied. Photography from satellites or aircraft can tell a considerable about how the crop is performing in each field particularly in the infrared and near infrared range. Farm vehicles can assess soil conditions with corers and electromagnetic induction (EMI) equipment while recording their position with the use of GPS. This information can then be fed into a computer with geographical information system (GIS) software which can present the data as maps, tables graphs, charts or reports. A tractor can be directed by a computer to dispense variable amounts of pesticide, fertilizer and water on the basis of location information provided by the GPS and field condition data provided by the GIS. The process can also be put in reverse. Different inputs, plant varieties and cultivation methods can be tried in different fields and their performance easily compared. So far this technology has only been adopted on a small scale. However, it will no doubt become more widespread once the technology matures, costs come down and farmers get used to the idea.
In the longer term crop growing may actually become factory production carried out in multi-level buildings. This would allow for massive increases in output per hectare. A 20 story farm factory on one hectare of land would not just grow the equivalent of 20 hectares. Output would be even higher than that because crops would be grown under optimal conditions in terms of growing medium, lighting, climate and water supply.
A population of 10 billion people with grain output of 550 kilograms per capita each per year (double the present average) and achieving a yield potential of 10 tonnes per hectare requires an area of 550 million hectares. Assuming 20 story facilities that is a land area of 27.5 million hectares or 275,000 km2. That is slightly larger than New Zealand or Colorado, and slightly smaller than Italy.
Per person the land area is 27.5 m3, the size of a living room. The building floor space per person of 550 m3 (23.5 x 23.5) is half the area of a quarter acre suburban block. If each floor only needs to be about a meter or two high, you are looking at a cubic area comparable to a typical bungalow. The construction investment required to accommodate our food production would then be no greater than that required to accommodate ourselves. So, it is unlikely to be a daunting task for the economy of the 22nd century.
There would also be greater water efficiency. The water would be delivered precisely as required, and none of it wasted on underperforming plants. The energy consumption of such food production methods would probably be greater than present methods. Pumping water to each floor, lighting, heating, cooling and building construction would require a lot of energy. However, at the same time, activities such as plowing, planting and harvesting would either no longer be necessary or be done with greater energy efficiency.