Sustainable agriculture for the future - ACS Publications

tinuously for 5000 years. Clearly, that was sustainable agriculture. But can to- day's intensive agriculture survive into ti~ture millennia? Demand fo...
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Planetarv Datriotism: Sustainable agriculture for the future W

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Howard A. Schneidermau Will D. Carpenter Monsanto Company St. Louis,MO 63167 Somewhere on this planet, probably in Mesopotamia in what is now Iraq,lies a plot of land that has been farmed continuously for 5000 years. Clearly, that was sustainable agriculture. But can today’s intensive agriculture survive into ti~turemillennia? Demand for food will be driven by population g r o and ~ the need for an upgraded diet in newly indusaializing countries (1). Future agriculture must meet these burgeoning needs without damaging the environment and must also supply feedstocks-the raw materials for the world’s chemical industries-when conventional petrochemical supplies become exhausted (2). That will require sustainable agriculture.

What is sustainable agriculture? The American Society of Agronomists in 1988 wrote: “A sustainable agriculture is one that over the long term enhances environmental quality and the resource base on which agriculture depends, provides for basic human food and Eber needs, is economically viable, and enhances the quality of life for the farmer and for society as a whole” (emphasis added) (3). The time dimension is critical. It implies the abiity to meet current needs and to endure indefinitely (4) with a p propriate evolution. Sustainable agriculture must evolve as world population doubles and the demand for animal protein increases during the next 40 years. Production of animal protein requires more agriculwal resources than the production of plants: For example, it takes 5 or 6 times as much energy to produce a calorie of pork as a calorie of grain. By 2030, the world must produce more than twice the food it does *Y. 466

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U.S. Depr. ofAgnculnrre b

Lowinput agriculture-agriculture

that employs few outside aids-is not necessarily sustainable agriculture. Some of the greatest damage to U.S. farmland has occurred in low-input cotton farming in the Southeast and lowinput grain fanning in the Great Plains. In both cases inputs were irrelevant to the damage; wind and water erosion and depletion of nutrients were responsible. Low-input sustainable agriculture (LISA) is also not necessarily the same as sustainable agriculture. LISA is shorthand for the strategy of limiting outside materials (particularly chemical pesticides) to promote sustainable agriculture. Yet one can imagine an intensive, productive, and sustainable agriculture that quires environmentally friendly herbicides and fertilizer formulations, genetically modiEed seeds, and other products that can be applied to farmland forever. Sustainable agriculture, as outlined in this article, reduces the use of chemical pesticides and synthetic fertilizers and also provides farmers with a proEtable livelihood. It provides consumers with highquality, abundant food while treating the environment gently. Biotechnology is one key to sustainable agriculture because it allows W13-936x19010924046M02.5010

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farmers to reduce their use of herbicides, insecticides, and fungicides (5) and to control pests that elude present technology. It may take another 20 years for today’s basic advances in biotechnology to be widely used for production of seeds and animal protein enhancers. But it will happen, and the benefits will be enormous. Biotechnology promises lower input costs for farmers, lower pesticide exposure for farm workers, lower pesticide residues for consumers, and reduced chemical load for the planet. During the next 20 years many of today’s chemical pesticides will become

obsolete. Certain environmentally friendly herbicides, Like glyphosate, will still be used, often in combination with biotechnology, to replace less friendly herbicides. New crop chemical formulations will be target-specific, require smaller doses, and protect nontarget organisms. Chemical innovations will enable farmers to use the new products at a fraction of an ounce per acre, instead of a pound per acre (6). Biotechnology may make certain crops more efficient in using soil nutrients, but the big news in fertilizer efficiency will be new controlled-releaseformulations of synthetic fertilizers. In the long

term, soil microbes may be genetically designed to enhance the tilth of soils. Biotechnology will be embraced by farmers in lessdeveloped countries too, because it can sustainably enhance production, productive efficiency, and incomes (7). But wherever farmers practice it, sustainable agriculture must be accompanied by education in the new technologies.

Reasonable assumptions It is reasonable to make the following assumptions about sustainable agriculture. First, world population will reach 10

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billion by 2030. Those people will need more than twice as much f w d as today's 5 billion because newly industrialized countries will be able to afford increasingly better diets (I). Second, society will become more environmentally sensitive, and agricultural practices will become more environmentally friendly. Pesticides that cause unacceptable environmental damage or threaten health will be withdrawn. Biotechnology and environmentally friendly chemicals will help to eliminate weeds, insects, and crop diseases. Synthetic fertilizers will still be widely used, but mostly in controlledrelease formulations, so that nitrate pollution of water will be minimal. Third, fewer people will engage in primary agriculture. In 1930 more than 20% of the American people worked on farms; now only 2% do. This trend is evident worldwide, even in the most populous countries of the less-developed world. Fourth, more land will be brought under cultivation as dams, irrigation, and new roads extend the reach of agriculture. However, gwd farmland will not increase significantly without enormous capital inveshnents. Fifth, mass outdoor agriculture will be practiced for at least another 100 years. When energy from nuclear fusion becomes cheap, in 2030 or 2050, crops may be grown hydroponically under artificial light, but it could take a long time for such systems to be widely used. Today's agricultural systems are certainly inadequate to meet the needs of 5 billion additional human beings and their demands for dietary improve ment. Clearly, the alternative to plowing up the planet and urging more people into labor-intensive primary agriculture is to increase the productivity of existing farms.That is the promise of sustainable agriculture.

The biotechnology revolution The goal of the mcalled Green Revolution was to improve grain production in the lessdeveloped world by plant breeding. It worked. Mexico has enjoyed a fourfold increase in wheat production since 1950. India and Pakistan doubled their wheat production between 1968 and 1972, and China has become almost self-sufficient agriculturally. The Green Revolution has its limitations: New plant varieties some times require more fertilizers, for instance. But overall it has led to a great increase in productivity. Today, farmers worldwide are searching for resource-efficient, costefficient, more profitable production systems (S), and the world is looking for environmentally friendly and sus488

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tainable agriculture. Biotechnology is particularly suited to fill this need through genetic engineering, that is, the transference of genes by nonsexual pmcedures. Scientists can take genes from one organism and insert them into a different organism, such as a bacte rium, producing a bacterium with new genes that carry instructions to manufacture a new protein. For example, the gene for human insulin has been inserted into bacteria, and these genetically transformed bacteria now produce human insulin for diabetics. In other experiments, scientists have inserted various foreign genes into plants and endowed these transgenic plants with desirable new traits (9,10) such as resistance to pests. It is bemming possible to transfer traits that are controlled by many genes, such as drought resistance. By the mid-l99Os, several u s e l l transgenic seeds will be available to farmers, and by the year 2000 dozens should be available. Gene

transfer is just a natural extension and acceleration of plant breeding. Many other applications for gene transfer have been found, as have some serendipitous side effects. For e m ple, gene transfer can help preserve genetic diversity, which makes agriculture less vulnerable to attack from diseases and pests (2). During the next two decades, the plant breeder will be able to introduce important new diversity into key crops and, ultimately, to introduce whole new crops. In certain crops with a narrow germ plasm base (soybeans, for example) gene transfer can create varieties currently unobtainable (IS). Geneticdy modified soil microbes, both bacteria and fungi, may become valuable as substitutes for some pesticides and soil supplements (5, 22, 23). Microbial pesticides are particularly attractive because they are less capitaintensive than many products traditionally used in less-developed countries (241.

Gene transfer technology can be used to design crops that need few chemical insecticides (5,11, 12). Similar techniques also can protect stored cereal crops from insect damage. Scientists have already successfullytransferred into tomatoes and potatoes the genes for resistance to certain viral diseases (Figures 1 and 2) (13-15).Oranges, cassava, wheat, and rice will be next. (Chemicals have been ineffective in combatting agricultural viruses.) Some progress is also being made in genetically modifying crops to resist fungal diseases (16). Use of insect- and disease-tolerant transgenic plants will shift the thrust of plant protection from treatment to prevention. This should lower both the farmer's input costs and the planet's pesticide load (5,6, 12). Important crops are being genetically modified to become tolerant to environmentally friendly herbicides such as glyphosate. Glyphosate will displace less-desirable herbicides and permit low-till agriculture, which limits erosion and conserves water (6, 14, 17-19). Genetic modification will lead to crops that use nutrients more efficiently and therefore require less synthetic fertilizer. There has also been astonishing progress toward making crops, particularly fruits and vegetables, easier to process and store. Present targets include crops such as tomatoes, which go soft rapidly. Atten. tion also will be paid to cassava, which deteriorates so rapidly that farmers sometimes leave it unharvested (20). Higher nutritional value is also an important target of gene transfer technology. For example, a change in a seed.storage protein gene could lead to higher quality seed grains. Crops such as cassava and taro, widely grown in the humid tropics, would be more nutritious if some of their storage carbohydrates were replaced with proteins. Another challenge to plant gene transfer technology is controlled ripening. Plants that mature earlier could mean shorter harvest cycles and better efficiency.Plants that mature later could remain in the fields longer, preventing rain from carrying away fertilizer. Plant molecular biology and novel chemistry are making it possible to hybridize and thus to improve the yields of important crops such as wheat, cotton, and rice. (Hybridization can increase rice yield by 25%.) Efforts to pro. heat, drought, and other duce transgenic plants that resist co stresses are also under way. Biotechnology can also produce tools the early detection of plant pests, which could lead to more efficient use of pesticides. Genes can be transferred to make plants produce therapeutic proteins for humans (6),such as insulin, antibodies (Zl),or peptides. Per-

Making each acre of farmland in lessdeveloped countries more productive will slow the destruction of rain forests (7).a vital source of genetic diversity. The plants, trees, insects, and microbes there contain a huge variety of traits that is essential to help us keep pace with the evolution of diseases and pests. If we continue to destroy our genetic library-a library as yet largely unread-we will be plowing under future human productivity and health.

Animal agrieulhlre Probably the first and most widespread farm application of biotechnology is the use of somatotropins, or growth hormones, to enhance the e%ciency of protein production in livestock. Somatotropins, proteins normally produced by the pituitary glands of domestic animals, can now be produced synthetically by genetically transformed E. coli bacteria. Four-year tests of bovine somatotropin (BST) on 20,000 dairy cows have shown a IO-20% boost in milk production and a 10% reduction in feed consumed (Figure 3). Forty cows treated with BST twice a month can produce as much milk as 50 untreated cows. while using 10% less feed (25). Porcine somatotmpin (PST), a similar protein for hogs, can boost feed efficiencies as much as 20% and produce leaner, protein-rich hogs (Figure 4) (6, 26. 27). In China, where 300 million overfat hogs are the animal-protein mainstay, PST could lead to an upgrading of the Mtional diet. PST significantly reduces the feed grain needed to produce a pound of pork. Animal biotechnology sometimes results in unexpected felicitous effecu. For example, it can slow down the onset of the greenhouse effect. The greenhouse effect is usually associated with the carbon dioxide emitted by vehicles and industry, but methane gas h m the guts of livestock also contributes significantly to planetary warming. Methane is 30 times as potent as carbon dioxide as a trapper of heat. Use of somatotropins can produce more animal protein while slowing the increase in the world's 3.3 billion domesticated cattle, sheep, goats, buffalo, and camels (28). Another important application of biotechnology is the production of powerful vaccines for foot-and-mouth disease, scours, shipping fever, and other animal illnesses. Direct gene transfer to chickens, swine, and cattle is also possible: Domestic animals someday may be born resistant to diseases (24).

Minimum-till agriculture In many parts of the United States a pound of topsoil is permanently lost for every pound of soybeans or corn

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FIGURE 2

FM test (1988) of tomato plants containing TMV coat protein gene

grown. That is a heavy price to pay, and it is certainly not sustainable. This erosion is caused by many factors, including tilling to control weeds. In many places, minimum-till agnCUlNre could reduce soil erosion. For example, if crops could be designed to be tolerant to an environmentally friendly herbicide like glyphosate, farmers could control weeds with less tilling, reduce water loss, and eliminate harsher herbicides. Such an approach is environmentally sensible, saves time and gasoline, and can enhance yields. Crops resistant to glyphosate and to other environmentally friendly herbicides are now in advanced field tests: seeds should be

available commercially by the mid1990s (6. 15.26).

Fertilizer use The pollution of surface water and groundwater by the nitrates in synthetic fertilizers presents an enormous challenge (29). Crops need fertilizers. The recent suggestion that US. farmers go back to using natural fertilizer from cattle raised along with their crops (30) presents some serious problems. First, supplies of manure are limited and cannot satisfy the demand. Second, most farmers are unwilling, for economic and cultural reasons, to return to the more labor-intensive farming required Environ. Sci.Technol..VoI.24. No.4. 1990 408

to combine animal husbandry with crop cultivation. Third, larger herds produce more methane, which contributes to the greenhouse effect.One promising a v e nue for research is the development of controlled-release formulations of synthetic fertilizers (31-34). In addition, biotechnology may pruduce plants or microorganisms that make more efficient use of soil nutrients. Still another strategy is to design crop plants that can 6x atmospheric nitrogen for their own growth. That approach did not advance appreciably in the past, in part because fixing atmospheric nitrogen is so energydemanding that yield suffers. Other approaches also are being tried. Molecular biologists are transferring genes to nodeguminow plants so that the plants will develop root nodules hospitable to symbiotic nitrogen-fixing bacteria such as Rhizobium. Scientists also are improving the strains of Rhizobium added to soybeans and peanuts (35)and designing crop that favor the growth of free-living nitrogen-fixing bacteria such as Arotobacter. Nutritionally important bacteria and fungi that are associated with the roots of many crops can also be g e n e t i d y modified.

ttfect 01 subcutaneous (su) or intramuscular (IM) injection of bovine somatotmpin (EST) on milk yielda

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FIGURE4

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In the humid tropics The lessdeveloped world presents

special problems for sustainable agriculture. Most of the 5 billion additional people on this planet in 2030 will live in the lessdeveloped countries of the humid tropics. Because of food distribution problems, the tropics need sustainable agriculture that is indigenous and highly productive. The slash-and-burn agriculture often used there now cannot support highdensity populations. Most nutrients are stored in vegetation rather than in soil, which leaves the soil infertile within a few years (36). Another obstacle to sustainable a d culture in the humid aopics is nomic development itself. Development tends to generate exploitative forms of pruduction; long-term sustainabiity is often sacrificed for shortterm income. Poor soil requires both skilled Evming and thoughtfd politid and economic action by government if it is to be farmedindehitely. The problem is made even more complex b e cause n a t i d agicultural policies often favor the spread of capitalized, monocultural cash-cropping and extensive ranching. The hue of immdiate economic advantage and short-term s6 curity pmmotes exploitative land use rather than sustainable agriculture (20). Only when people in lessdeveloped countries can feed themselves and enjoy reasonably good health will they join the world’s economy as steady producers and consumers. For both nomic and hnmanitarian reasons, it is in

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the best interests of the developed millet, and cotton to enhance yields and world to help them. reduce input costs. The technology of Improved agricultural practices and plant gene transfer must be developed biotechnology can alleviate some of the where it will be used, to ensure that it more urgent problems (7).In fact,plant will respond to local conditions and be biotechnology was identified by readily awepted by the people. UNESCO and other scientific groups as The foregoing ideas are not a quick a top priority for lessdeveloped coun- technology 6x for the problems of a d tries. For example, agroforestry, in- cultwe in the humid tropics or for tercropping, perennial mp, and mini- world hunger. The less-developed mum tillage will help secure more countries need economic and political durable yields from poor tropical soils reform, education, land reform, debt (36). Genes for increased protein can relief, an agricultural infrasnucture, a be transferred into important root mp strict deforestation policy, realistic govsuch as cassava and taro. Genes for re- ernment food subsidies, family plansistance to viruses, insects, and fungi ning, and many other things. But the can be inserted into cassava, sorghum, new technologies are powerful and

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necessary tools to help ensure a sustainable supply of food.

NAS report on U.S. agriculture The Board on Agriculture of the National Academy of Sciences recently released a report titled “Alternative Agriculture” (30), which mentions some of the issues raised in this article. The report, which has been widely quoted, encourages lower commodity subsidies, more emphasis on “natural farming” techniques, and gradual elimination of pesticides and synthetic fertilizers. It addresses some of the political and economic issues that face U.S. agriculture, but few of the technical issues. The report contains many admirable ideas. Surely it is wrong for the $13.9 billion federal subsidy program to discourage farmers from trying new methods or growing new crops. The commodity-support program certainly demands some rethinking if we expect Europe and Japan eventually to provide a free market for American farm products. Indeed, U.S. trade representative Carla Hills is pushing for a “substantial progressive reduction in all farm subsidies that, we hope, eventually will lead to zero” (37). Certainly the report is right in saying that we must avoid the excessive use of nitrates and pesticides. The U.S. Department of Agriculture should support more research on low-chemical pest management, controlled-release formulations of synthetic fertilizers, minimum-till agriculture, genetically improved crops and microorganisms, new crops, and land reclamation. Certainly, the nation should protect its resource base for agriculture and not focus single-mindedly on a plentiful food supply. Consumers have a right to uncontaminated food; farmers have a right to choose among options rather than having to follow a single prescription (4). However, the report has some deficiencies that readers should bear in mind. For example, it recommends that many of the 2.1 million U.S.farmers give up the agricultural technologies that underlie the intensive agriculture that they have practiced for 40 years. That would mean a return to extremely labor-intensive farming. Production and productive efficiency would suffer greatly. The report also recommends that U.S. farmers give up synthetic fertilizers and instead use manure from livestock. That is not feasible for the reasons presented above. In addition, the report recommends that many U.S. farmers stop relying on chemical pesticides and fertilizers and instead rotate crops to fight weeds, diseases, and insects. Although it is true that crop rotation can help, significant 472

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rotation is already in use today. The recommended crop rotations would seriously disrupt the availability of feed and food grains in the United States. Widespread use of the report’s “alternative methods” would prevent U. S. farmers from maintaining an abundant, moderately priced supply of food. In the 1950s food represented 24% of the consumer’s dollar; today it takes less than 12%, largely as a result of pesticides and fertilizers. “Alternative Agriculture” offers no feasible alternatives. For the past 40 years, grainbelt farmers in the Midwest and the Great Plains have been encouraged by policy makers to convert diverse small farms with livestock into large, specialized farms. Today’s high-yield farming would not be feasible without expensive equipment, synthetic fertilizers, and pesticides. The report mentions favorably such applications of molecular biology as transgenic plants. It also mentions environmentally friendly herbicides favorably. But neither transgenic plants nor environmentally friendly chemicals and formulations are recognized as keys to future agricultural systems. The report emphasizes only traditional agronomic practices, but transgenic plants and environmentally friendly chemicals will be crucial to future agronomic practice in both developed and less-developed countries. The report does not emphasize that pesticides and synthetic fertilizers add economic stability to farming. They allow farmers to stay in business even when their crops are stressed or when soil nutrients are less than optimum. Pestilence, temperature, and rainfall are all unpredictable; farmers are understandably reluctant to give up the reliability of synthetic fertilizers and pesticides. The report focuses mainly on today’s agricultural productivity. It does not look into the future, when there will be twice as many mouths to feed and irresistible pressure for upgraded diets. The report does not explain how to meet these needs. In addition, the report does not acknowledge that the use of synthetic fertilizers and pesticides by the farmer is self-limiting. Synthetic fertilizers and pesticides are expensive, so most farmers use as little as possible. The pest problems that beset certain crops, such as fruits, also were not addressed adequately in the report. For instance, crop rotation will not protect a fruit orchard attacked by insects (37). Despite its shortcomings, “Alternative Agriculture” is useful for those interested in learning how agriculture can simultaneously be made more productive and more environmentally friendly.

But the report does not sufficiently challenge the old agricultural paradigm. It glosses over biotechnology, new chemistry, and new formulations; it makes some recommendations that are impractical; and it fails to address some of the most compelling agricultural needs of the near future. The report falls short of providing a true prescription for sustainable agriculture.

Conclusion A principal problem facing agriculture during the next 40 years is that current techniques cannot provide the food output and diet improvement that the world will need. Unless we choose to plow up the entire planet and to urge more people into labor-intensive primary agriculture, we must squeeze greater yields from existing acres in ways that will remain environmentally friendly indefinitely. A special problem that faces U.S. farmers today is ensuring that their products can compete everywhere, including the United States. Unless American taxpayers plan to support the price of U.S.-grown commodities to a much higher degree, American farmers must increase their productive efficiencies. U.S. agriculture could be permanently crippled by failure to adopt biotechnology, environmentally safe pesticides and fertilizer formulations, and other new technologies that could significantly increase productive efficiency and ensure quality products. These new technologies will inevitably hasten the restructuring of U.S. agriculture, whether or not they are adopted here. They certainly will be adopted in other countries, which will make foreign commodity products more attractive to the U.S. market than high-priced local products (6, 26, 38). American farmers deserve the tools to compete. A country or an industry cannot survive long by erecting barriers to competition or resisting innovation; the American steel and automobile industries, for example, may have waited too long. Sustainable agriculture and the continuous innovations that it demands must become a fact of daily life. Farmers must continue to innovate, as they have for the past 11,OOO years. Sustainable agriculture is possible only with biotechnology and imaginative chemistry; it is simplistic to advocate sustainable agriculture while eschewing biotechnology. Unless the whole world goes back to farming, biotechnology is our best hope for sustainable agriculture. And it seems to have arrived in time to do some good. The technological innovations discussed here will not, by themselves, solve the agricultural problems of the

world. But with supportive innovations in public policy, they can go a long way toward preserving this planet as a livable place for our great-grandchildren and for their great-grandchildren.

Acknowledgment We thank the following people for their useful input to our thinking about sustainable agriculture: Clifton A. Baile. Gary F. Barton, David J. Drahos. Robert T. Fraley, James C. Graham, Robert B. Horsch. Ernest G . Jawonki. Michael J. Montague. Philip Needleman. Melvin L. Rueppel, Audrey M . Schneiderman. Virginia V. Weldon, Milton P: Wilkins, Jan E. Williams, and Kate Williams. Elizabeth Gordon and Antoinene Long typed the manuscript.

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..,. H o w a d A. Schneiderman is senior vice president. research and development, and chief scientisr of Monsonto Company He received his B.A. in marhemarics and M ~ U ral sciencesfrom Sworrhmore College and his Ph.D. inphysiologyfrom Harvard University, In 1975 he was elecred to rhe National Academy of Sciences and 10 rhe American Academy of Arts and Sciences. He has published more than 200 research papers on developmental biology and generics. insect biochemistry. and plant growth, as well as articles on biorechnology and on university-industry inreractions.

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W9 D. GwpenIer, chairman of Mansant a S Corporare Biotechnology Strategy Comminee, is vice president of Monsanto Agriculnrml Company > technology division. He is a member of the b w r d of directors of the Indurrial Biotechnology Association; a member of the Keystone NarioMI Advisory Comminee for Biorechnology; and an adviser on biotechnology to the (1.S. House of Representatives Science and Technology Subcommirtee on Natural Resources. Agriculture. Research and Environmenr. He received a B.S. degree in agronomy from Mississippi Srare University and holds an M.S. and a Ph.D. in plan: physiology from Purdue Universiy. Envlron. Scl. Technol.. Vol. 24, No. 4, 1990 473