The Biodiversity That People Made.

• Author: Tuxill, John

The intricate genetic diversity of the world's crops is largely a human invention--and it remains essential for human sustenance. The complex landscape of traditional farmland is also a human invention, and it is now essential natural habitat. Traditional farmers really know what they are doing, and there are good reasons why they aren't doing monoculture.

Snaking along the border of Minnesota and the Dakotas, the Red River Valley has long been one of North America's leading grain-producing regions. Blessed with fertile prairie soils deep enough "to bury a man standing," Red River farmers have intensified their production in recent decades, and planted more and more of their land to just two crops, wheat and barley.

Such specialization is supposed to be the key to success in the brave new world of multinational agribusiness. Yet the last few years have been anything but bountiful for most Red River farmers. In the early 1990s, following several years of abnormally cool, wet weather, their fields were hit with unprecedented outbreaks of a fungal disease called "wheat scab."

But according to Brian DeVore of the Minnesota-based Land Stewardship Project, the fungus is benefiting from more than just the weather. Many of the region's farmers have recently adopted a "no till" cultivation system that is designed to conserve soil. Standard cultivation prepares the soil for planting by plowing, but as the soil is broken up it becomes vulnerable to erosion. "No till" reduces erosion by leaving the previous year's broken stalks in place and planting through them. Unfortunately, however, those crop residues are a perfect home for the fungus in between growing seasons. A few decades ago, one solution would have been to let cattle graze down the residue, but there are few cattle in the region any more. Cattle production has grown increasingly specialized too; few of the valley's farmers can compete with the enormous livestock operations elsewhere. So the fungus has its way with these vast, monotonous expanses of wheat, one field after another, year in and year out: that must be the wheat sca b version of heaven.

The bottom line is that disease and record low grain prices have cost Red River farmers over $4.2 billion since 1992. Nearly half of that loss is directly attributable to the scab. On the Minnesota side of the river, wheat and barley plantings in 1999 were down some 35 percent compared to their levels at the start of the decade. One-fifth of the region's farmers went out of business in 1997 alone.

Such problems are usually debated in economic terms, but they are related just as fundamentally to the loss of biological diversity in agriculture. Biodiversity refers to the variety inherent in life--both the genetic variety within single species and the "species variety" within ecosystems. For most people, the term probably evokes Nature with a capital "N" -- tropical rain forests, coral reefs, mountain wildernesses, and other untrammeled corners of our planet. Not surprisingly, most of our efforts to protect biodiversity have focused on such places.

Yet there is another side to biodiversity, one that is very much a part of human history. As agriculture developed over the past eight millennia, farmers domesticated several hundred different crop species, and developed hundreds of thousands of different varieties within those crops. In the hands of early European farmers, for instance, an inconspicuous herb of coastal Mediterranean hillsides gradually became cabbage, kale, cauliflower, broccoli, and somewhat more recently, kohlrabi and brussels sprouts. Native American farmers took five shrub species with small, bright fruit originally adapted to attract birds, and diversified them into hundreds of eye-catching and tongue-searing varieties of chile pepper. This ancient form of "cooperation" between people and plants has produced a vast wealth of genetic diversity within crop species.

Traditional agriculture fosters diversity in another dimension too, particularly on land used, not for commercial production, but primarily for "subsistence production"--that is, land that farmers cultivate for their own households. In just about any part of the world, subsistence production results in a highly diverse agricultural landscape. You'll find intensively cropped fields for staples such as wheat, corn, rice, or potatoes; fallow fields covered in more unkempt vegetation, where the soil is resting to regenerate its fertility; an orchard or garden plot for fruits, vegetables, and herbs; a woodlot for fuelwood and other forest products. This kind of land use, replicated on farm after farm, creates substantial ecological diversity.

Today, both forms of agricultural biodiversity are receding in the face of commercial production, which usually demands. a high degree of uniformity. The economic and political pressure on farms to grow for the mass market is a pervasive effect of the globalization of agriculture, and in many places, farmers are forsaking the practices that have long fostered biodiversity-- practices that have sustained farming for millennia. But it's becoming increasingly obvious that the current agricultural paradigm will be far less sustainable. Intensive monoculture farming is exacting a heavy ecological toll in the form of pesticide and fertilizer pollution, erosion, freshwater depletion, and the destruction of wildlife habitat. And as farmers in such places as the Red River Valley have found, the social costs can be very steep as well. The message from such places is now very plain: we've no hope of achieving a sustainable agricultural system unless we can find ways to restore what scientists now call "agrodiversity."

Hot Spot Agriculture

During the 1920s, a brilliant young Russian scientist named Nikolai I. Vavilov undertook to answer a question that must at the time have seemed vast in its implications if rather bizarre: what was the origin and significance of genetic variation among crop plants? Vavilov was a firm adherent to the emerging disciplines of evolutionary theory and genetics, and he approached his studies with enormous intellectual energy. From a home base in St. Petersburg at the All-Union Institute of Applied Botany and New Crops (which he headed after 1925), Vavilov organized expeditions not only to the fields and gardens of remote corners of the Soviet Union, but also to Iran, Ethiopia, Mexico, Japan, and some 50 other countries. Tens of thousands of different crop specimens made their way into his collections.

Vavilov's career was tragically cut short in 1939 when he was deported to a Siberian labor camp, where he died the following year. But he had lived long enough to produce the first comprehensive picture of agrodiversity. He realized, in the first place, that the world's crop diversity was not distributed randomly; it was instead concentrated in particular regions. In Afghanistan and northern Pakistan, for instance, Vavilov found farmers growing nearly a hundred varieties of "soft" wheat (the kind best suited for making bread) -- several times more than had been documented in all of Europe. He argued that the region where a crop showed the greatest number of unique and unusual forms was likely also to be where it was first domesticated (see map, pages 28 and 29). These are also regions where the wild plants from which crops descended -- their wild relatives -- can often be found growing in nearby natural habitats.

Most of these regions remain "hotspots" of crop diversity today. In the Andes of Peru, for instance, peasant farmers continue to grow thousands of traditional varieties -- or "landraces" -- of potatoes, corn, and peppers, as well as lesser-known crops such as quinoa (a grain), ulluco (a multihued tuber that thrives at altitudes over 4000 meters), and tarwi (a bean related to the lupine flower).

Vavilov was also one of the first researchers to draw attention to the tremendous environmental and cultural diversity present in traditional small-scale farming. He astutely noted, for instance, that crop genetic diversity was often particularly rich where farmers had to cope with a great deal of variability in local climate, soil conditions, and other environmental factors, as in mountainous regions like the Caucasus and the Andes.

Such regions also contain some of the best examples of agrodiversity on an ecological level. They are ever-changing mosaics of cultivated and fallow fields, hedgerows, orchards, irrigation ponds, windbreaks, woodlots -- along with patches and corridors of native vegetation. That, for example, is what anthropologists Christine Padoch and Wil de Jong found when they studied several Ribereno communities on the edge of the Amazon River floodplain in eastern Peru. Riberenos are a people of mixed indigenous and European ancestry, long established in western Amazonia. In just one village, Padoch and de Jong found a dozen distinct kinds of agriculture. Some farmers cut small fields from mature upland rain forest, then burned and planted them with mixtures of up to 60 different crops, following a classic...