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jueves, 11 de junio de 2009

Food of the Future to Be More Diverse?

Farmers (such as this Iowa man harvesting corn in an undated picture) may return to a more diversified "portfolio" of crop species to cope with threats posed by global warming.Photograph by John Stanmeyer

From the perspective of the plate, the foods we'll eat in the future will likely look and taste a lot like what we eat today. But take a closer peek, and tomorrow's dinner becomes very different indeed.

Agricultural scientists shaping the future of food say that, as global waming alters patterns of temperature, rainfall, and carbon dioxide concentrations in the air, farms must evolve.

Global warming will affect agriculture in a variety of ways: Some regions and farms will get a boost; others will suffer.

To cope with changing growing conditions, farmers will need to reverse decades of crop homogenization and diversify plant strains, agriculture scientists say.

Stephen Jones, a plant geneticist and wheat breeder at Washington State University in Pullman, notes that since the mid-20th century, farming has undergone radical homogenization.

"It's not just about monoculture of farms, where one farm grows only one crop, it's also monoculture within those crops and within fields," he said.

Jones notes, for example, that just three varieties of wheat comprise 60 to 70 percent of all wheat grown in the Pacific Northwest, a situation he says is similar with other crops in other regions.

While homogenization has made it easier to grow huge amounts of food on ever larger plots of land, adapting to global warming-induced changes becomes more difficult, particularly if those changes vary from farm to farm and plant to plant.

"There has to be some variation available for the environment to work on. If not, there will be big trouble," he said.

Jones and other researchers say global warming could suppress crop yields, increasing food costs in Western countries and worsening food shortages in many developing areas.

Natural Selection

Agricultural scientists say there are a variety of possible solutions to avoid low crop yields or failures.

Lewis Ziska, a USDA plant physiologist based in Beltsville, Maryland, is in the early stages of creating more resilient varieties of food crops by breeding them with certain weeds.

"Many weeds seem to do better, in general, under a wide range of environments," he said. "Can we take these genes and exploit these abilities by crossing the weeds with cultivated lines? Absolutely."

Ziska notes, for example, that domesticated rice can't produce seed if the temperature creeps above about 90° Fahrenheit (32° Celsius) when the plant is trying to fertilize.

Some weeds related to rice avoid the problem, however, by undergoing fertilization in the early morning or at night, when temperatures are generally cooler. That trait could be passed to the domesticated rice, Ziska says.

Scientists are also looking to breed modern crops with ancestral plant lines.

Global warming forecasts predict higher concentrations of atmospheric carbon dioxide. Ziska has found that under such conditions an early 20th-century strain of wheat actually performs better than a common modern strain.

Jones, of Washington State University, is working on this, as well. His team made test plots of every strain of wheat grown in the Pacific Northwest since the 1850s, looking for traits that could be useful under global warming conditions.

The plant geneticist said he is especially interested in characteristics that haven't been selected for since modern farmers started relying heavily on herbicides, pesticides, and fertilizers—such as the ability to compete with weeds or grow well in poor soil.

Plants with those traits could help farmers reduce the need for chemical inputs and lower their carbon footprint.

Genetic Modification

In a changing climate, farmers will need to experiment with many plant varieties to find the mix that works best on their farms, Jones says.

"Nature does a better job of selecting the plants that work than we do," Jones said.

Other crop scientists say there are situations where nature could benefit from a helping hand.

L. Curtis Hannah, a plant molecular biology researcher at the University of Florida in Gainesville, is using modern gene-transfer techniques to engineer strains of corn that could help farmers in tropical areas.

Global warming may bring relatively fast temperature increases such areas.

Focusing on the naturally occurring genes in corn that produce an enzyme called AGPases, Hannah has been able to produce lab-modified corn that thrives at high temperatures.

"When the temperature is above 90 [32° Celsius] during the early stages of seed development, we've seen increases in the yield as high as 68 percent," Hannah said.

While environmentalists generally oppose the introduction of genetically engineered organisms as too risky, Hannah and other crop scientists say such techniques aren't inherently dangerous and can be effective tools—used alongside traditional breeding—to adapt crops to global warming.

The USDA's Ziska said, "It's not a simple good vs. evil scenario."

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