Risking corn, risking culture.

• Author: Cummings, Claire Hope

If genetically modified corn spreads around the planet, one of humanity's greatest creations--a highly diversified and reliable food source--could be severely weakened or even destroyed. So could many of the human communities that depend on it.

Here in the remote mountains of Oaxaca, one of the oldest stories on earth--the vital relationship between people and plants--is taking a dramatic turn. Corn was first domesticated here and in nearby areas of Mesoamerica, from wild grasses about 8,000 years ago. Native varieties of corn are still grown here by the descendants of those first farmers. Now, this place, the center of origin of corn, and the center of its genetic heritage and diversity, has also become the center of a welling controversy over the finding of genetically modified organisms (GMOs) in the native corn.

The land itself helps tell the story. The road from the valley city of Oaxaca to the small mountain village of Capulalpam weaves through a rich mosaic of ecosystems. It climbs through evergreen pine-oak forests, crosses the Continental Divide as it transects the Sierra Juarez, drops down through a semi-arid zone of manzanita and shrub, and overlooks the Mexican Rio Grande, which winds along a sandy riverbed studded with agave and nopal. The profuse flora, the abundant wildlife, and the clear water that flows through these mountains, known locally as the Sierra Norte, support some of the world's most treasured biodiversity.

As the road turns towards the mountain range, small towns carved out of the deep green forest glisten in the sun like jewels strung along the mountainsides. Most of the people who live here are Zapotec. They place a high value on cleanliness and beauty. Their villages fit harmoniously into the topography and feature colonial-style churches and scattered houses made of wood from their forests. Household gardens and milpa growing corn, beans, and squash are nearby. Each town is surrounded by communal fields, which are in turn surrounded by communal forests. These concentric circles of resource use and cultivation are collectively managed. The Zapotec call themselves the "people of the clouds," and for the entire day, even under a bright blue sky, a thick mantle of white fog clings to the wooded ridge tops.

Dr. Ignacio Chapela is one of two scientists from the University of California, Berkeley who documented the discovery of transgenes in the Mexican native, or criollo, corn grown here. Chapela and his colleague, David Quist, took their samples from Capulalpam, so this remote village is getting more than its fair share of visitors these days. Chapela has worked with the communities in the Sierra Norte for years, but he had not returned to Capulalpam since November 2001, when his report was published in the prestigious journal Nature. I went back to Capulalpam with Dr. Chapela, to talk with farmers and village officials about the impact that transgenic corn is having on their lives, and to explore what it might mean for the rich biodiversity and indigenous cultures of the region.

The Chapela/Quist discovery is the first report of GMO contamination of a major crop at its center of origin. A center of origin contains the early forms of a crop and its wild relatives. It is the gene bank the world depends on to improve and refresh a crop's genetics. Mexico's native corn varieties are a treasure chest of genes useful for breeding plants that can adjust to changing climate, agricultural, and nutritional needs. Scientists worry that if these plants become infected with GMOs, and if the artificial genes persist, they could dangerously contaminate, and possibly wipe out, the natural genetic basis of the world's most important crops. Although they are manufactured, GMOs are living organisms, capable of reproduction. Once released, they are beyond human control. They are a new form of pollution, one that is difficult to detect and completely invisible. Because so little is known, their release is an uncontrolled experiment, which the biochemist Erwin Chargaff, known as the father of molecular bi ology, has said would constitute "an irreversible attack on the biosphere."

For years, scientists and environmental activists have been warning the Mexican government that GMOs in imported corn could harm Mexico's exceptionally rich biological and cultural diversity. The known risks of GMOs include the creation of hard-to-control weedy relatives of crops through "crop-to-wild hybridization, the development of insect pests or weeds that are resistant to the chemicals used with GMO crops, and the unintentional poisoning of beneficial insects and non-target species (see 1).

No one knows how GMOs got to Capulalpam. It's suspected that they arrived, courtesy of the Mexican government and the North American Free Trade Agreement (NAFTA), in shipments of imported corn sold here for human consumption. Corn samples taken from the government-subsidized Diconsa store in Capulalpam tested positive for GMOs. A few local farmers, who were not aware that the imported corn contained GMOs, may have used the store-bought corn for seed.

Mexico, which banned the commercial planting of transgenic corn in 1998, imports about 6.2 million tons of corn a year, mostly from the United States. About a quarter of the U.S. commercial corn crop is GMO, and after harvest it is mixed with conventional corn. As a result, all conventional U.S. corn is now considered to contain at least a low level of "background" GMOs. And unlike Japan, Mexico does not require that GMO corn from the United States be segregated and labeled.

It was entirely predictable that GMOs in imported corn would find their way into Mexico's own cornfields. Corn is, after all, practically promiscuous in the way it spreads its pollen around, and corn farmers love to experiment with corn seed. What we call corn today owes its very existence to the intentional and accidental recombination of varieties by corn farmers. So it was only a matter of time before the foreign genes in the imported corn would get out and mix with the locals. If there was any surprise in this finding, it was how rapidly the GMOs had traveled to such a remote region. What is most alarming about this finding is that such rapid dissemination is occurring at a time when so little is known about how these transgenes will affect the ancestral ecosystems and the genetic heritage of the world's major crops.

Corn is the world's second most important food crop, after rice. It is practically miraculous in the way it converts sunlight into food. Corn plants can grow 1.1 centimeters or more a day, which may explain why Midwest farmers claim to be able to hear their corn growing (see 2). But corn's productive and adaptable nature also makes it particularly susceptible to GMO contamination. The corn plant reproduces through "open pollination" and it is in constant communication with its surroundings. As it grows, it evaluates its environment, senses the available light, moisture, nutrients, and competition, and then adjusts its height, length of cob, and time of ripening accordingly. Boone Hallberg, one of the world's experts on corn varieties, says that because of corn's adaptability, the Oaxaca region alone boasts up to 85,000 unique strains, or "sub-varieties" of criollo corn, that have conformed to specific local conditions.

Hallberg is a deeply tanned, and still spry, transplanted Californian, who has lived near Capulalpam for over 50 years. He teaches and conducts research on native corn varieties at the Instituto Technologica in Oaxaca. Sitting behind a desk piled deep with papers that are weighed down with colorful ears of corn, he talks at length about how these local "landraces" developed as corn fine-tuned itself to the diverse "agro-ecological niches" of the Sierra Norte. These landraces have developed dozens of useful characteristics. Some have improved nutritional qualities or agronomic values such as tolerance to acid, alkaline, or saline soils. Some are drought or frost resistant; others are able to withstand strong winds, or resist pests and plant diseases. One remarkable variety can even fix its own nitrogen.

How GMOs will affect these specialized landraces, and thereby impact the world's agricultural genetic diversity, can only be understood in the context of how perilous the state of the world's crop diversity currently is. As the late University of Illinois botanist and plant geneticist Jack Harlan (author of Crops and Man) famously said, the world's genetic diversity is all that "stands between us and catastrophic starvation on a scale we cannot imagine. In a very real sense, the future of the human race rides on these materials." Modern plant breeding programs focus on only a very few improved crops. The patenting of seeds and...