COLUMN ONE : In Search of Genetic Diversity : Nature’s storehouse of genes has been exploited for many advances in agriculture and medicine. Is the storehouse being depleted?

High atop Sierra de Manantlan, near Guadalajara, Mexico, jaguars and ocelots stealthily roam and crested wild game birds scrabble through a landscape splashed with delicate orchids and giant magnolias. These and 10,000 other kinds of living things on the mountain are safe now from the onrush of development, people and destruction--protected in one of Mexico’s newest and most celebrated preserves.

But when the Sierra de Manantlan Biosphere Reserve was created in 1987, it wasn’t because of the wildlife or even the exotic flowers. Instead, the centerpiece of this ruggedly beautiful reserve is a scruffy, weedy plant, named teosinte , that if noticed at all would seem more like a blight than a natural treasure.

Teosinte is a wild relative of corn and this particular variety grows on 15 acres on Sierra de Manantlan and no where else in the world. It has genetic traits found in no other plants--traits that could prove vital to corn fields across the world. It has resistance to diseases that commonly afflict other varieties, and it’s a perennial plant that--unlike most domesticated varieties--does not have to be replanted year in and year out.

The discovery of teosinte and the creation of the 350,000-acre reserve to protect it offer a prime illustration of the pivotal role genetic science is playing in efforts to uncover nature’s secrets and preserve its bounty.

Increasingly, decisions about conservation, management and use of natural resources are being shaped by an understanding of genes and their role in adaptation and survival. Genes are tiny chemical instructions in the cells of all living things that serve as the building plans of life. Genes determine whether the tomato has a thick, bright red skin or a thin, green one; whether a giraffe will be slow or fleet of foot; and whether a child will have brown or green eyes.

Each species needs genetic diversity--that is, a wide variety of genes among its members--and the more diversity of species, the better for all. Left alone, nature controls the pools of genes a species has for coping with diseases, fending off pests and responding to changes in their environment. Family members with genes best suited to the environment will survive to pass along their genes to future generations.

If all family members are genetically alike, all will respond to changes in their environment in the same way. If one can’t survive, all will perish.

Humans have been able to exploit nature’s storehouse of genes to recover from pestilence and bad crop years, improve food production and develop “wonder� drugs. But human beings are depleting nature’s storehouse at a devastating rate. Already, 95% of all the species that ever lived on Earth have become extinct. While much of the loss is part of nature, biologists and other scientists record with alarm the loss of tens of thousands more species each year. And millions of other species--from micro-organisms to insects to mammals--become endangered daily as man further encroaches on their natural habitats.

There’s no time to waste, say most genetic conservationists. By the end of this century, at the current rate of habitat destruction and narrowing of the genetic pool, another million species of plants, animals, insects, fish and birds will have become extinct. As the global genetic pool becomes more shallow, the paths to adaptation, evolution and survival become more precarious.

Loss of biological diversity jeopardizes the world’s ability to feed itself, deprives us of potentially life-saving or -enhancing materials and can upset the social, economic, political and cultural structures that rule the relationships between nations and peoples. It closes the door on choices.

“My guess is we’ve got another decade to collect genetic diversity, or the game’s over,� said Cary Fowler, director of the Rural Advancement Fund International, a Pittsboro, N.C.-based organization concerned with the worldwide loss of genetic resources in plants and animals.

But collecting and protecting genetic diversity is an enormous task, and yet it is often left to the under-funded, often divided efforts of a loose network of environmentalists, philanthropists and biological and social scientists. Even in highly developed countries such as the United States, genetic conservation is seldom a national priority.

Worldwide, genetic conservation efforts have been fragmented by international squabbling, primarily between the developed nations and the Third World, site of the greatest natural diversity. Critics contend that many of the industrialized world’s policies toward lesser-developed nations actually speed the destruction and loss of diversity.

A gene overlooked today, however, could be the basis of tomorrow’s wonder drug, fiber or food.

For the pharmaceutical industry, the genes of wild, exotic plants, and even animals, have been a surprise treasure trove. In recent years, two anti-cancer drugs have been developed from the periwinkle native to Madagascar. And only now is modern science beginning to prove the validity of many ancient folk remedies brewed, distilled, or pounded from native and often wild plants.

“What kind of trouble do we get in when we start making decisions that we do or do not need certain characteristics? We’re not smart enough to know what we (will) need and that’s been proven so many times,� said Fowler.

Though many see biotechnology, or genetic engineering, as a fallback position to genetic conservation, it just isn’t so, say the experts. Biotech companies that create new drugs, or even develop new varieties of plants and animals, do not create brand new genes, as such, but manipulate existing genetic materials.

“If the periwinkle had been obliterated,� said Ronald Cape, founder and chairman of Cetus, a biotechnology company in Emeryville, Calif., “those two cancer drugs wouldn’t be available. To invent those molecules out of whole cloth--well, it wouldn’t happen.�

Cape sees what already is in nature as “a treasure house of existing complicated molecules, developed by nature over many years, with therapeutic qualities. . . a fantastic shortcut� to biotechnology’s work of creating improved products.

So far, the bulk of genetic conservation has been in so-called hot-house approaches: zoos for animals and seed “banks� for plants. Such off-site preservation methods often rely on current and usually incomplete assessments of genetic value.

Banks and zoos also often ignore the interdependency of plants, animals and insects on each other for survival. The Sierra de Manantlan Biosphere Reserve is a frontispiece in the genetic conservation movement because the teosinte isn’t being saved in isolation: The reserve was deliberately created to save the habitat along with a rare species.

The Mexican teosinte is special because, while others in its family of wild maize relatives are also perennial, only this teosinte has genetic characteristics that allow it to be crossed with domestic corn to produce a perennial offspring. It may take another five to 10 years to breed a viable, commercial strain of domestic corn with the teosinte’s valuable genes, yet the discovery of the wild plant has brought the dream of a perennial corn into the realm of possibility.

Hopes for perennial corn aside, the preservation of teosinte is another bit of insurance for the survival of all corn by keeping its genes available in the species’ gene pool.

For just as genetic diversity is key to survival, genetic uniformity is tantamount to vulnerability to the unexpected.

In Ireland in the 1840s, the unexpected was a fungus that was transported by ship from North America--an invasion as deadly as it was surreptitious. The fungus found an easy target in the potato fields that were the backbone of Irish agriculture; all the potatoes were nearly identical genetically, and all susceptible to the fungus. It swept through the fields, laying waste to billions of potatoes.

As many as 2 1/2 million people died in the Irish potato famine--perhaps the most devastating example in modern history of the dangers of genetic uniformity.

Since then, farmers, plant breeders, pesticide makers and scientists have learned a great deal about protecting crops. Now, farmers know how to control the fungus that devasted the Irish potato fields, as well as many other diseases, parasites and environmental conditions that endanger food crops. Using biotechnology techniques of isolating and transfering specific genes, scientists and plant breeders are even learning to engineer plants that “manufacture� their own resistance to pests and disease.

But the most important lesson of the Irish potato famine is that without genetic diversity, there can be no real protection of food crops.

Of all the efforts in conservation of genetic diversity, those involving food crops are the most sophisticated. In part, that’s because an adequate food supply is so vital, but also, through the centuries, farmers and gardeners have been using and perfecting plant-breeding techniques that have relied on some form of conservation.

These techniques, ever being tested in the fields and in the laboratories, have resulted in vast increases in the quantity and quality of food being grown the world over. The new varieties of high-yielding, disease-resistant wonder crops are best suited to mass agriculture techniques that dominate U.S. farming, for example. In the Western world, there are now fewer farmers raising more crops than ever.

The heart of agribusiness is the proliferation of the best. But that, too, has its downside.

“We keep demanding the very best available (and that will) have a tendency over time to narrow the genetic bank,� Dr. Major M. Goodman, a statistical geneticist at North Carolina State University, said.

That was the case in the fields of America’s Corn Belt in 1970, when the best farmers in the world had planted the very best available seed on prime land, using plentiful water, the latest equipment and techniques.

The best seeds were hybrid varieties--yielding more than 80 bushels of corn per acre, four times the average of just 40 years before. And, they were vulnerable: The very genetic qualities that made the corn seed so desirable also made the corn susceptible to a fungus, called Southern Corn Leaf Blight.

In 1970, the blight wiped out about 15% of the U.S. corn harvest, costing American farmers more than $1 billion. The farmers, livestock ranchers and consumers around the world who rely on U.S. corn harvests were lucky. A turn in the weather stopped the leaf blight before it got to the rest of the crop.

It could have been devastating, because so few varieties, only a dozen or so, accounted for 80% to 90% of all the corn planted in the Corn Belt. The scare was enough to rivet national and worldwide attention on the dangers of genetic uniformity.

After the corn leaf blight, a study by the National Academy of Sciences reported that many major food crops were “impressively uniform genetically and impressively vulnerable.� The problem was not just in corn, but in vital crops such as hard red winter wheat, soybeans and potatoes.

The shock waves from the corn blight registered throughout the international agricultural community. A new agency to support worldwide collection and preservation of agricultural diversity was formed in 1974 by the internationally supported Consultative Group on International Agricultural Research.

The Consultative Group’s worldwide network of research centers is primarily devoted to plant breeding; ironically, its work in introducing new high-yielding, disease-resistant crops to agriculture-poor nations in the 1960s and 1970s that sparked the phenomenal increases in food production, called the “Green Revolution,� has also been criticized by some genetic conservationists as having contributed to loss of genetic diversity.

Most plant breeding and research around the world is concentrated on a few dozen species of crops--out of the thousands and thousands of food crops raised and eaten around the world--that are of major economic significance. In many cases, the research is further specialized because the aim is to develop higher-yielding varieties of these crops. This results in collecting practices and policies that focus on the genetic materials of the most modern, already highly bred or cultivated varieties, called cultivars.

For plant genetic information, it is the equivalent of having a “world history� library that had books about only a handful of countries, and then, only those volumes that had been written in the last few decades.

So, like many collections, the research center seed banks are not safes of genetic diversity, but reflections of their more pragmatic goals, said Dr. Calvin O. Qualset, director of California’s Genetic Resources Conservation Program.

Neglected at these banks are seeds of lesser known crops, that while less globally significant still may be very important to a particular region or culture. Also under-represented at seed banks are the primitive varieties, wild relatives and land races of the major crops, whose genetic properties are less understood or more difficult to use in breeding programs. Land races are varieties cultivated and bred through traditional techniques by peasant farmers, often over hundreds of thousands of years.

Third World development projects and increased environmental woes--reaching further and further into the native habitats of such crops--have put at highest risk the very crops that are least represented in seed banks. The countries poorest in commercial agriculture, whose people may subsist on a few local crops that aren’t protected in major collections, remain the most vulnerable to irretrievable crop losses.

In the meantime, more and more farmers around the world are planting new and often hybrid crop varieties--a trend helped along by a consolidated and globalized seed industry. Instead of the old ways of saving seeds from the best of one year’s crop for planting the next, peasant farmers now must buy seeds for each planting.

When they turned to modern farming techniques and new hybrid varieties, Third World farmers often abandoned their historical food crops. In many countries, this process was often encouraged by foreign and local government aid policies that subsidize farming only if the farmers plant the new varieties.

Garrison Wilkes, a professor of biology at the University of Massachusetts, said: “Literally, the genetic heritage of a millennium in a particular valley can disappear in a single bowl of porridge if the seeds are cooked and eaten instead of saved as seed stock.�

In some cases, the hybrids are unsuited to the tropical conditions, or the peasant farmers lack the necessary skill, equipment and additives, such as fertilizers, required for successful growing of the modern cultivars.

The result is that the new crops die in the fields and the land races are lost forever.

Fowler, of the Rural Advancement Fund, recalled a visit to Ethiopia in 1985, during the height of the famine there. “We drove past mile after mile of (what looked to be) onion fields, and I wondered what they were doing growing onions. But I was told they weren’t onions. We were in corn fields,� he said.

“The stalks were about a foot tall, when they should have been five to seven feet tall. (The farmers) had been given high-yielding corn. But it was no-yielding in Ethiopia. That decision,� he said, “cost lives.�

In the Philippines, rice farmers had been growing increasingly dissatisfied with the new varieties of rice they had been encouraged to plant instead of the land races their families had grown for many generations. In 1986, a large group demonstrated outside the International Rice Institute, a Consultative Group center that houses one of the world’s richest collections of rice genetic materials. The rice farmers wanted their old varieties back, and yet didn’t want to lose the government and foreign support that came with the newer varieties.

Wilkes and other genetic conservationists are now urging farmers in rural areas of the Third World to keep one field planted in the old land races, even if the majority of the crops are new hybrids. And, they are lobbying aid and development programs, such as those sponsored by the World Bank, to modify subsidy plans and other policies that encourage wholesale conversion to modern cultivars and with it, loss of diversity.

“I worry about the guy in the Andes who threw out his old seeds to plant DeKalb’s latest corn variety,� said John H. Barton, a Stanford University law professor who is active in international issues. “I’m worried that by a farmer in the developing world giving up the seeds his ancestors saved (in order to plant) a new variety, we lose our insurance.�