What is biodiversity?

Loss of biodiversity in modern agriculture

When we lose biodiversity?

Preservation of the overall biodiversity

(modified from: Nina V. Fedoroff and Nancy Marie Brown - Mendel in the kitchen - The National Academies Press, 2004)

The Mexican maize scandal

In October and November 2000, a study of Ignacio Chapela and David Quist, working at the Mycological Facility in Oaxaca (Mexico), founded the CaMV 35S promoter and a Bt gene in native varieties of maize—in spite of the fact that growing genetically modified corn has been banned in Mexico since 1998. Subsequent and more in-depth studies questioned these results but their work started the debate on the gene flow between GM plants and landraces (for further details: EN1, EN2, EN3, EN4; see also: Cartagena Protocol on Biosafety to the Convention on Biological Diversity [EN5], [ES1], [F1]). In a report about the case, in 2001, Nature Biotechnology stated that “the major point of divergence in the current discussion” about gene flow was not whether a transgene from a genetically modified variety had moved into the Mexican landraces, but how the so-called contamination would affect biodiversity. The journal wrote: “The […] researchers have claimed that appearance of DNA from GM crops into criollo maize compromises biodiversity. ‘If the transgene makes the carrier any more fit,’ says Chapela, ‘you would expect to see the crowding out of landraces that do not carry the trait.’” A few paragraphs later, the journal gave the opinion of Val Giddings, who is a spokesperson for the industry group called BIO, headquartered in Washington, D.C. Giddings was quoted as saying, “We know what threatens biodiversity, and it is not the substitution of one variety for another in an agricultural field. It is the conversion of native and wild land to agriculture in the first place.”

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What is biodiversity?

The journal failed to point out that the two sides in this debate were talking at cross purposes. Although each was responding to a question about biodiversity, they defined that term—as their answers make clear—in rather different ways. Chapela is concerned about the diversity of traditional varieties of corn, about the number of genetically different maize landraces planted by farmers in Oaxaca, Mexico. If a genetically modified Bt corn, for example, proved to give a higher yield, it might become more popular than the landraces, and farmers might stop planting these old-fashioned varieties. Whether this change from old to new varieties is bad or good might well depend on the point of view. If the Bt gene were truly introgressed into a landrace, as Quist and Chapela originally suggested (but there is no certainty that this fact appened), then a landrace would still have all its original genes and it would still grow and produce corn as did the original landrace—but it would give a higher yield because of its new gene for insect resistance.

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Loss of biodiversity in modern agriculture

Yet Chapela’s fear—that genetically modified varieties of agricultural crops could push landraces to extinction—is a valid one, though not in the way he is concerned about. According to a United Nations report, the success of commercial varieties of all kinds—not just those created using molecular techniques—has led to the disappearance from farms of more than 80 percent of old-fashioned apples, maize, tomatoes, wheat, and cabbages worldwide. The introduction of the improved varieties has had the positive effect of increasing yields. But the widespread use of just a few different varieties leads to genetic sameness in crops and this genetic uniformity can make them vulnerable to new pathogens or unusual environmental conditions on a very large scale.

Preserving crop gene pools is increasingly the function of organizations specifically devoted to the task. In America more than 400,000 crop varieties are maintained in the USDA’s National Plant Germplasm System. IRRI in the Philippines has more than 80,000 varieties of rice alone. CIMMYT [ES2] has collected and preserved hundreds of landraces of maize, periodically growing and harvesting them to preserve their viability. In response to the publicity generated by Quist and Chapela’s report, CIMMYT researchers sampled 42 of the landrace populations in its seed bank, finding no evidence that the Bt gene was present in any of the plants tested.

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When we lose biodiversity?

But perhaps this sudden concern with genetic purity is misplaced. In their work with small-scale farmers, CIMMYT’s researchers have found that landraces are far from being museum pieces. Population geneticist Julien Berthaud argues that in Oaxaca, where Chapela and Quist gathered their corn, the landraces do not even meet the standard definition of a crop variety. They are not distinct or uniform or stable. Trying to maintain one in a static form could doom it. As a CIMMYT press release explains, “Small-scale farmers select their own seed. Often they choose the best ears at harvest and save seed from only a few cobs—a logical approach but one that increases deleterious mutations. As defects accumulate, the variety loses its genetic value.” Rather than preserving a landrace, Berthaud says, what needs to be preserved is “the active flow of genes.” If the Bt gene is useful for insect control in landraces, the Mexican farmer who succeeds in introgressing the gene into a landrace will hardly obliterate that landrace but on the contrary will increase its chances of survival.

The idea that transgenic maize will displace landraces is nonsense, says Major Goodman of North Carolina State University. Despite the availability of improved corn varieties since the 1930s and the intensive maize breeding that has been conducted in Mexico, Goodman said, there has been little impact on the indigenous landraces grown by 80 percent of Mexican farmers. The new varieties designed for the U.S. Corn Belt are far from well adapted to the subtropics, where they are disease-prone and stress-sensitive. Even though such transgenic varieties have undoubtedly been introduced in Oaxaca, Goodman doubts that it will matter much—they will fare so poorly next to the landraces (see also the comment of Peter H. Raven).

It is the hard struggle for survival faced by the small-scale Mexican farmers who grow and consume the native varieties that is the greatest threat to preservation of the landraces. Said Goodman, “Their economic survival (and hence maize diversity’s survival) prospects are bleak, and transgenic maize is probably one of the least of their problems.” Adds CIMMYT director general Iwanaga, “The perception that transgenic maize is reducing diversity must not obscure the very real need for research to mitigate the many confirmed threats to maize diversity. Every day, diversity is eroded by habitat destruction, human migration from rural to urban areas, and the irreparable loss of traditional maize seed and knowledge as the farming population ages. The present concern about transgenic maize may only add to these threats. If farmers and consumers are convinced that landraces are ‘contaminated’ by transgenes and therefore unsafe to grow or eat, farmers will have even fewer incentives to preserve landraces in their fields.”

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Preservation of the overall biodiversity

Even if one variety of maize did crowd out another in a Mexican farmer’s field, as Chapela fears, it wouldn’t have any effect on biodiversity as Val Giddings of BIO was using the term. Giddings was speaking about biodiversity in the much larger sense of the diversity lost when acres of forest are cut down, plowed, planted, and turned into farmers’ fields. Rather than thinking about the diversity within a single species—maize—he is thinking about the estimated 10 to 30 million species (not counting bacteria) that inhabit the earth today. In his closing remarks at the Mexico City conference on gene flow, Peter Raven spoke of both meanings of the term. Raven, as director of the Missouri Botanical Garden, is a tireless crusader for biodiversity. He noted that the historical rate of extinction climbed from about 10 per year in 1600 to roughly 100 per year in 1950. It now stands at several thousand extinctions per year.

Biodiversity in Mexico, as elsewhere, says Raven, “can be preserved only in the context of a sustainable nation.” Maintaining biodiversity is not as simple as keeping genetically modified maize out of the country. The most serious threats to both maize biodiversity and to biodiversity overall, concludes Raven, are not from GM maize, but from “habitat destruction, urbanization and the abandonment of cultures, alien invasive weeds and pests, and insufficient attention to indigenous peoples and to agriculture in general.” In today’s world, with its still-growing human population, preserving natural biodiversity requires raising agricultural yields to reduce the demand for new acres to plant. The best modern techniques are needed to increase the nutritional content of crops, while decreasing the impact of agricultural chemicals on wildlife. To Raven, preserving biodiversity also means “increasing the productivity of selected landraces” using contemporary molecular techniques. Far from being a dire threat, the introgression of selected genes that enhance insect and disease resistance might ensure the survival of maize landraces and preserve biodiversity—in the larger sense—by improving small-scale farmers’ yields and lives.

And similar remarks seems to be right for the European countries too.

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