Developing countries may lose 334 million acres of prime farm land to climate change in the next 50 years, scientists estimate. After mid-century, continuing temperature rises, expected to be nine degrees Fahrenheit or more by then, are expected to start adversely affecting northern crops as well, tipping the whole world into a danger zone, the authors say.
'Many people assume that we will never have a problem with food production on a global scale. But there is a strong potential for negative surprises,' said Francesco Tubiello, a physicist and agricultural expert at NASA's Goddard Institute of Space Studies who coauthored all three papers. Goddard is a member of Columbia University's Earth Institute.
The three studies were coauthored by researchers from prestigious organizations in North America, Europe and Australia.
Timed to coincide with the United Nations climate conference which opened today in Bali, Indonesia, the studies appear in this week's issue of the 'Proceedings of the National Academy of Sciences' published from Washington, DC.
Nebraska corn shrivels in the scorching sun. Summer 2002. (Photo courtesy U. Nebraska-Lincoln)
The authors say that existing research fails to account for seasonal extremes of heat, drought or rain, multiplier effects of spreading diseases or weeds, and other ecological upsets. All are believed to be more likely in the future due to climate change.
In order to keep pace with population growth, current production of grain will probably have to double, to four billion tons a years before 2100, the authors say.
Studies in the past 10 years suggest that mounting levels of the greenhouse gas carbon dioxide in the air may at first bolster the rate at which many plants convert sunlight to leaves, stalks, roots and fruits, and, along with new farming techniques, may add to some crop yields.
Between now and mid-century, higher temperatures in northern latitudes may expand lands available for farming, and bring longer growing seasons, the research shows.
But the studies published today demonstrate that these gains likely will be canceled by agricultural declines in the tropics, where even modest one to two degree rises are expected to evaporate rainfall and push staple crops over their survival thresholds.
The authors of the PNAS studies say that much previous research work is oversimplified, and as a consequence, the potential for bigger, more rapid problems remains unexplored.
'The projections show a smooth curve, but a smooth curve has never happened in human history,' said Tubiello. 'Things happen suddenly, and then you can't respond to them.'
Extreme weather events such as heat waves or sudden big storms could wipe out crops on vast scales if they occur for even a few days during critical germination or flowering times.
Tubiello says this is already happening on smaller scales.
The authors say that farmers may temporarily mitigate some effects of the warming climate by moving toward adaptations now.
One of t he regions most vulnerable to drought is Sub-Saharan Africa. Here, an African farmer examines a new variety of drought tolerant sorghum. (Photo courtesyICRISAT)
Adaptations already being set up or considered include regional climate forecasting systems that enable farmers to switch to different crops or change the timing of plantings; introduction of new varieties or species that can withstand anticipated conditions; and improved flood-mitigation and water-storage facilities.
This would buy a few decades of time for nations to agree on ways to slow or reverse the warming itself.
'After that,' says Tubiello, 'all the bets are off.'
The vast majority of scientists agree the Earth's climate is being directly affected by human activity. Records show that 11 of the last 12 years were among the 12 warmest on record worldwide.
The Intergovernmental Panel on Climate Change, composed of more than 2,500 scientists from across the United States and around the world, states with more than 90 percent confidence that human industrial activity is driving global temperature rises.
Levels of the greenhouse gas carbon dioxide today are nearly 30 percent higher than they were before the start of the Industrial Revolution, based on records extending back 650,000 years. Carbon dioxide is emitted by the burning of coal, oil and gas.
According to NASA, the polar ice cap is now melting at the rate of nine percent per decade. Arctic ice thickness has decreased 40 percent since the 1960s. The current pace of sea-level rise is three times the historical rate and appears to be accelerating.
The two week UN climate conference that opened today in Bali is expected to result in negotiations on an agreement to curb human emissions of greenhouse gases. The agreement would begin after 2012 when the first phase of the Kyoto Protocol expires.
While the United States has not ratified the Kyoto Protocol, U.S. negotiators in Bali say they 'seek a 'Bali Road Map' that will advance negotiations under the UN Framework Convention on Climate Change to be in place by 2009.'
The other authors of the three studies published by the National Academy of Sciences are based at Pennsylvania State University; Arizona State University, the UN Food and Agriculture Organization in Rome; Austria's International Institute for Applied Systems Analysis; France's National Agronomy Research Institute; Australia's Commonwealth Scientific and Industrial Research Organization; and Wageningen University in the Netherlands.