more than doubled, corn and potato yields increased four- .... At the time of the Irish potato famine of the 1840s, virtually ... of Europe's potatoes were at risk.
Book Review
The Last Harvest: The Genetic Gamble that Threatens to Destroy American Agriculture Paul Raeburn. Lincoln: Bison Books, University of Nebraska Press, 1995. Hardcover $21.60, paperback $10.80. Reviewed by Jon K. Piper, The Land Institute, Salina, Kansas.
"One Kansas Farmer feeds 101 people and you," proclaims a billboard alongside Interstate 135, on the road from Salina to Wichita, Kansas. Indeed, modern industrialized agriculture is enormously successful in terms of output per acre farmed or hour worked. In 1991, American farmers grew 66 percent of the world's export corn and soybeans and 32 percent of its export wheat. By all accounts, this does not sound like an enterprise facing the possibility of a catastrophic collapse. But, as Paul Raeburn points out in The Last Harvest, American farmers are in fact waging a genetic gamble; they are "betting the farm" in a way they never intended. Worse, the U.S. government seems little inclined to do anything about the risk facing our agricultural security. Raeburn, science editor at the Associated Press, argues in a clear, journalistic style that a worldwide "genetic erosion" threatens the future of agriculture in ways that are unexpected and unpredictable. For several years, biodiversity has been the main buzzword among conservation biologists alarmed about the loss of wild species and the collapse of natural ecosystems. What is rarely appreciated is that the future of the world's food supply, and agriculture's ability to adapt to a changing global environment, is also threatened by this impending loss of biodiversity. In Chapter 1, the author establishes the importance of wild germplasm to agricultural improvement by citing the value of teosinte and wild tomato to corn and tomato improvement. Teosinte, a wild grass, carries genes for pest and disease resistance that can be bred into cultivated corn. For a time, the discovery of a tetraploid teosinte (Zea perennis) even offered the promise of a perennial corn. A handful of wild tomato seeds collected in Peru eventually transformed the U.S. tomato industry. By increasing the soluble solid content of tomatoes, this germplasm increased the value of the California tomato crop by $21 million a year. Whatever we may think of the kind of tomato and the scale of agriculture that resulted, the examples illustrate the importance of access to genetic diversity. A farmer clearing a field could have Culture & Agriculture
57
unwittingly destroyed these plants before they were found by botanists. American farmers can trace much of their success to one of the least appreciated advances of the 20th century: the emergence of scientific crop breeding. Prior to the rise of modem genetics, crop varieties developed through the intelligent selection of seeds produced by chance crossbreeding in farmers' fields. Over the centuries, such traditional varieties accumulated by the tens of thousands. Once researchers understood how genetic traits were passed on, however, they were able to select crops with desirable characteristics and breed them in ways that would enhance those characteristics. Such tailor-made cultivars were the foundation for the giant productivity increases that have characterized the American agricultural miracle. From 1930 to 1980, U.S. wheat yield more than doubled, corn and potato yields increased fourfold, and yield of canning tomatoes increased six-fold. Roughly half of these increases were due to the development and widespread adoption of improved crop varieties. The rest, of course, were due to increased use of fertilizers, pesticides, and mechanization. By the early part of this century, botanists knew how to breed crops; what they needed were sources of raw materials, that is, plants with useful genes that could be bred into cultivated plants to improve them. One of Nikolai Vavilov's central contributions to botany in the 1920s was his identification of the centers of origin of cultivated plants, the places in the world where crop relatives with the most valuable genes were likely to be found. The plant institute he founded grew into a network of 400 laboratories with 20,000 employees. Scientists at the institute understood the critical importance of this germplasm to the future of Soviet agriculture. During the Nazis' siege of Leningrad in 1942, many researchers chose to starve to death rather than eat the precious seeds in Vavilov's collection. Ironically, the geneticist who laid the foundation for the spectacular crop improvements of the 20th century died of malnutrition in a Saratov prison in T->43, a victim of a conspiracy to abolish the science of genetics. To this day, Vavilov's seed collection remains one of the world's greatest. Chapter 2, provocatively entitled "Seed Banks and Seed Morgues," traces the history of germplasm collection in the United States. The story begins with the likes of Ben Franklin and Thomas Jefferson, and their early work in germplasm collection. Franklin's diplomatic sojourns abroad typically doubled as seed collecting trips. Jefferson was also an avid Vol. 19, Nos. 1/2 Spring/Summer 1997
value until a new problem appears. With the appearance of a new pest or disease, the collection suddenly becomes a uniquely valuable resource. The overwhelming success of the Green Revolution had its downside for biodiversity, however. The widespread introduction of high-yielding varieties led to the demise of local landraces in many areas. It also increased farmers' dependence on external inputs and narrowed broad-based farming systems to ones dependent upon a single cash crop. In India, 40,000 traditional rice varieties have been almost completely replaced by only 10 modern varieties that together supply 75 percent of India's rice crop. If American agriculture is to remain productive, it will need a continued infusion of germplasm for crop improvement. Unfortunately, according to Raeburn, the U.S. government currently does almost nothing to guarantee the preservation of landraces or wild crop relatives. The natural areas where new botanical treasures await discovery are rapidly disappearing, succumbing to the pressures of urbanization and development. Few if any American environmental groups have made the connection between conservation of wild places and food security. The motivation to preserve wilderness is often primarily recreational. When the boundaries of national parks are being drawn, crop scientists are rarely consulted. Of the 1.2 billion acres set aside in 4,500 parks and reserves around the world, very few help preserve threatened wild crop relatives. Chapter 4, "As Alike as Identical Twins," exposes the danger posed by extensive genetic uniformity in major crops. At the time of the Irish potato famine of the 1840s, virtually all the potatoes grown across Ireland were genetically identical, having been primarily derived from two samples that had been brought back from the New World in the 16th century. Unfortunately, because both samples were susceptible to infection with the fungus that causes potato blight, all of Europe's potatoes were at risk. During the ensuing suffering and political upheaval as many as 1 million people starved to death. Twenty-seven years ago, a similar tale occurred in this country when southern corn leaf blight devastated the U.S. corn crop. In the Midwest, corn plays the role that the potato played in 19th century Ireland. The first commercial hybrid corn was introduced in 1929. By the end of World War II, hybrids had almost completely replaced the traditional, openpollinated varieties that had preceded them. The widespread adoption of hybrid corn encouraged a dangerous genetic uniformity in the U.S. grain belt that ultimately led to a disastrous epidemic. Most American corn varieties had something in common: a single gene that made the plants male-sterile by preventing the formation of pollen. This trait was bred into corn varieties because it simplified the production of hybrids. By 1970, 85
seed collector, and his botanical gardens at Monticello are legendary. Their contributions to agriculture helped transform the economy of the New World. Abraham Lincoln established the U.S. Department of Agriculture in 1862, in part to continue and expand the seed exchange. In 1878, seed collecting was the Agriculture Department's highest priority; fully one-third of its budget that year was devoted to germplasm acquisition. The National Plant Germplasm System (NPGS) began in 1946 with the passage of legislation authorizing the establishment of regional plant introduction stations. By the 1970s, these stations and the National Seed Storage Laboratory (NSSL)— the world's premier seed bank in Ft. Collins, Colorado—had become a cooperative network of nearly three dozen collections housed in state and federal research facilities. Unfortunately, according to many scientists, the U.S. seed bank system, despite its promises, has failed to maintain these vital seed collections, which require ongoing evaluation and regeneration to remain viable. Years of chronic underfunding, combined with little federal appreciation of germplasm's importance, have raised serious questions about the condition of the nation's seed bank. Moreover, each plant species is part of an ecosystem that a seed bank cannot preserve. If the species were to disappear in the wild, the survivors in the seed bank would be stripped of their pollinators, root fungi, and the other symbiotic partners that cannot be placed in cold storage. Hence, because seed banks cannot substitute for preservation of plants in the wild, they do not guarantee the survival of critical crop germplasm. Fifty years of neglect have taken a toll. Recently, a sobering study concluded that nearly two-thirds of the collection had not even been tested for viability. Moreover, nearly half of the samples at the NSSL were perilously close to extinction. For example, 90 percent of the tropical corn samples collected before 1950 have probably been lost through ignorance and lack of suitable storage facilities. Chapter 3 explains how hitherto obscure varieties of wheat and rice were the basis for the Green Revolution, which is credited with saving hundreds of millions of people from starvation. Genes from dwarf wheat varieties were at the core of a spectacular research effort which led to an explosion in farmers' harvests. After World War II, the dwarf wheats became vitally important around the world, particularly in the developing countries. The story was repeated withrice,which began with the discovery of a dwarf landrace in a farmer's field in Taiwan. Green Revolution breeders used two kinds of genetic resources: genes from landraces and from the crops' wild relatives. Wheat, corn, rice, and barley, which together make up 90 percent of the world's grain, have all been improved by the use of wild germplasm. The work with dwarf varieties shows that germplasm stored in a collection is of no apparent Culture & Agriculture
58
Vol. 19, Nos. 1/2 Spring/Summer 1997
Pimentel and his colleagues have estimated that this squandering of essential ecological capital costs the U.S. economy $44 billion per year. In addition, modern agriculture's demand for water is staggering. For example, it requires 1,500 pounds of water to produce 1 pound of corn. The area of the world's farmland under irrigation is now 5 times what it was in 1900. Excessive use of irrigation, too, has taken a toll on the landscape, especially in arid environments. In the United States, crop yields are declining on more than 25 percent of the nation's irrigated acres because of salt buildup. As with soil, aquifer water is being consumed faster than it can be replenished. Third, Americans consume an enormous amount of nonrenewable energy in the production of food. The use of fossil fuels in some parts of the U.S. economy is 1,000 times what it was a generation ago. We are poor global energy stewards. To maintain ourselves in the manner to which we have become accustomed, each American uses annually as much energy as 2 Swedes, 33 Indians, or 295 Tanzanians! Thus, American farmers will face pressure to boost productivity while treading more lightly on the environment. Chemical contamination, global warming, and ozone depletion are environmental threats that represent something new in human history. Agriculture's ability to respond to novel conditions depends upon access to a rich array of plant genetic resources. Thus, any reduction in the genetic diversity of those resources limits society's options for responding to new problems and opportunities. The pace of finding and evaluating new germplasm has already fallen off. But this will not become apparent until the end of the 1990s because varieties now released for commercial use are the result of work begun a decade ago. The final chapter cites several examples of how better utilization of crop germplasm can assist efforts to develop a more environmentally friendly agriculture. Fungicide applications to some orchards have been eliminated by turning to varieties of apples bred to resist fungal attacks. Similarly, the development of wheat varieties resistant to the Russian wheat aphid can replace massive insecticide use. Without the huge germplasm collections housed in seed banks, growers would have no option but to continue to rely on expensive, dangerous pesticides. Raeburn has strong words for those who blithely assume that we can simply genetically engineer ourselves out of this crisis. No breakthrough in biotechnology can compensate for the loss of the genetic material plant breeders depend on. Germplasm provides our lifeline into the future. It is foolhardy to invest so heavily in biotechnology while allowing our rich genetic heritage to pass into oblivion. The Last Harvest is notable in establishing a clear link between the loss of wild ecosystems and reduced resilience and adaptability of agriculture. It contains a good, nontechnical
percent of U.S. corn acreage carried this trait. It turned out to be a costly oversight. That year, a new fungus spread wildly through Americas corn crop, especially in the southeast. The disease it caused, southern corn leaf blight, destroyed 15 percent of the U.S. crop and cost farmers $1 billion. The outbreak was one of the most serious epidemics ever to strike American agriculture. Unfortunately, this tragedy threatens to repeat wherever genetically similar plants cover thousands of acres. For example, 90 percent of the sunflower hybrids grown in the United States share the same cytoplasm. If a pest or disease finds a way to exploit that uniformity, virtually the entire annual crop of $200 million could be wiped out. Industrialization has forced breeders to abandon genetic diversity and rely on pest and disease control experts to protect the crop. Chapter 5, "One Planet, One Experiment," highlights the global loss of genetic and species diversity. Fifteen percent of the 250 threatened or endangered plants in the United States are potential sources of germplasm for agriculture. The Food and Agriculture Organization of the United Nations predicts a loss of 40,000 plant species worldwide by the middle of the 21st century. This extinction will take with it many of the important wild relatives of the bean, potato, pepper, tomato, com, squash, and peanut. In addition to the loss of important crop relatives, the destruction of wild areas in the tropics will lead to the disappearance of countless plants with crop potential. Conservation biologists urge that preservation of the world's biodiversity be accorded top scientific priority. Beyond the inability to maintain adequately diverse and viable genetic stock, seed banks are also vulnerable during political upheavals. For example, Nicaragua lost many of its valuable com samples during the Sandanista Revolution and workers at a gene bank—protesting low wages—ate Peru's national collection of potato varieties. Most recently, during the civil strife in Somalia, both of its seed banks were looted and the seeds were eaten. As a result, hundreds of crop varieties adapted to the Somali environment were destroyed. Chapter 6, gloomily entitled "The Last Harvest," contains a list of impending global environmental catastrophes and their implications for agriculture's future. For the United States to achieve and maintain its position as the world's leading food exporter, soil, water, and energy are being consumed at prodigious rates. Add to that the damaging effects of agrochemical contamination, global warming, and ozone depletion in the stratosphere, and you have a recipe for an agricultural disaster of unprecedented scope. Of all the natural wealth upon which agriculture depends, soil ranks first. Yet, because of agriculture's dependence on extensive monocultures of annual crops, this precious topsoil is eroding away faster than it is being formed. In fact, about 2.5 million acres of U.S. crop land are abandoned each year because of soil degradation. Cornell's David Culture & Agriculture
59
Vol. 19, Nos. 1/2 Spring/Summer 1997
treatment of the history of American plant breeding, germplasm acquisition and evaluation, and the role of seed banks. Important scientific concepts are interspersed with entertaining vignettes of the principal players, making this a very engaging book. Nevertheless, I would have liked to have seen more critique of modern agriculture's drive for ever higher yields. For instance, Raeburn could have explored whether the use of genetic diversity in the Green Revolution was in
Culture & Agriculture
fact a misuse of that resource—part of a larger pattern of squandering resources rather than safeguarding and using them judiciously. The loss of biodiversity worldwide is tragic not only for moral, aesthetic, or scientific reasons. It also carries a dire practical consequence. If we lose too much of that biological wealth, we will face the ultimate environmental crisis. We will be unable to feed ourselves.
60
Vol. 19, Nos. 1/2 Spring/Summer 1997
