Sunday, June 27, 2010

Adaptation Critical to Agriculture in Already Changing Climate

Strategies include breeding sturdier crops, modifying livestock production

By Cheryl L Pellerin - Science Writer

Washington - Ten thousand years ago, as Earth's climate stabilized, people began turning planting into agriculture and animals into livestock. Civilization was transformed. Today, with that critical stability deteriorating as the result of climate change, food security for the world's billions hinges on helping crops and cattle thrive amid rising temperatures and extreme weather.

Climate, greenhouse gases and agriculture are inextricably bound. Agriculture contributes 14 percent of annual greenhouse gas emissions to the atmosphere through energy-intensive farming (carbon dioxide released), rice production and livestock (methane) and fertilizer (nitrous oxide), even as soils, plants and improved farming practices act as carbon sinks to keep carbon dioxide (CO2) out of the atmosphere.

"Agriculture will be mitigating its greenhouse gas emissions at the same time it works to adapt to a changing climate," Cynthia Rosenzweig, senior research scientist at the NASA Goddard Institute for Space Studies in New York, said during a June 16 briefing in Washington.

Meanwhile, according to the International Food and Policy Research Institute (IFPRI), the changing climate will have dramatic consequences for agriculture. Water sources will become more variable, droughts and floods will stress crops, some coastal food-producing areas will be inundated by salty seas and food-production rates will fall in some inland areas.

"These changes have already begun to have documented effects on agriculture production," Rosenzweig said, "in yields, growth stages of crops, management practices, pests and diseases, and livestock production and productivity."

APPLIED EVOLUTION

CO2 is essential for photosynthesis - the process green plants use to turn water and sunlight into food and oxygen. Rising concentrations of CO2 in the atmosphere will increase rates of photosynthesis, speeding up growth and development for many plants. Yields for most crops have risen dramatically over the past 40 years thanks to improvements in cultivation (planting, fertilization) and genetics.

But as CO2 rises so does temperature, César Izaurralde of the Joint Global Change Research Institute at the University of Maryland, said June 16, and temperature increases over the next 50 to 100 years are likely to reduce yields of corn, wheat, sorghum, cotton and peanuts.

Paul Gepts, a geneticist and professor of agronomy at the University of California-Davis, detailed strategies for adapting agriculture to a changing climate. These include switching crops or crop mixtures to match new temperatures, increasing crop biodiversity to strengthen agricultural systems and breeding plants to produce varieties that tolerate drought, heat and other stresses.

Another strategy is to grow crops as usual and let climate change sort them out.

"This is an exercise in applied evolution," he said. "If you provide biodiversity, the climate will automatically start selecting the crops and the varieties within those crops that are better adapted to the changed conditions."

Farmers will also have to test alternative crops, Gepts said, develop ways to transition from one climate state to another, conserve genetic diversity and make sure there is support for plant breeding and breeding research.

Livestock, traditionally raised on open ranges, may have to be sheltered from rising temperatures and extreme weather, and Izaurralde said more research is needed to understand how environmental stresses like heat will affect animals.

CROP RESEARCH

The Consultative Group on International Agricultural Research (CGIAR), established in 1971, is a scientific organization that supports 15 international centers, working with hundreds of government and civil society organizations and private businesses around the world. CGIAR donors, the United States among them, include developing and developed countries, international and regional organizations and private foundations.

CGIAR research tackles agricultural productivity and a range of initiatives related to water, biodiversity, forests, fisheries and land conservation. CGIAR scientists also play major roles in collecting, characterizing and conserving plant genetic resources. Eleven centers maintain more than 650,000 samples of crop, forage and agroforestry (combining trees and shrubs with crops or livestock) genetic resources in the public domain.

The researching is yielding results:

. More than 50 new drought-tolerant maize (corn) varieties developed by the International Maize and Wheat Improvement Center and partners grow on 1 million hectares in Africa, producing average yield gains of 20 percent over the old varieties.

. Most rice varieties can survive complete submergence in water for only three days, but the International Rice Research Institute, working with the University of California-Davis, identified a gene that lets rice plants survive complete submergence for more than two weeks. This trait has been bred into rice varieties grown in several Asian countries.

. New Rice for Africa (NERICA) varieties developed by the Africa Rice Center combine the high productivity of Asian rice with the acclimation of African rice varieties to African drought, weeds and pests. NERICA lines have been tested in 31 countries, with 16 lines released in 15 countries and adopted on 200,000 hectares.

. Biofortified crops, bred to be rich in nutrients, are helping reduce malnutrition, including vitamin A deficiency, which leaves people susceptible to blindness and disease. The International Potato Center developed improved sweet potato varieties high in beta-carotene (the precursor to vitamin A) that are benefiting more than 6 million people in eastern and southern Africa.

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(by the Bureau of International Information Programs, U.S. Department of State)