ScienceDaily (Feb. 12, 2010) — Yields from some of the most important crops begin to decline sharply when average temperatures exceed about 30 degrees Celsius, or 86 Fahrenheit. Projections are that by the end of this century much of the tropics and subtropics will regularly see growing season temperatures above that level, hotter than the hottest summers now on record.
An international panel of scientists writing in the Feb. 12 edition of the journal Science is urging world leaders to dramatically alter their notions about sustainable agriculture to prevent a major starvation catastrophe by the end of this century among the more than 3 billion people who live relatively close to the equator.
Specifically they urge world leaders to "get beyond popular biases against the use of agricultural biotechnology," particularly crops genetically modified to produce greater yields in harsher conditions, and to base the regulations of such crops on the best available science.
"You're looking at a 20 percent to 30 percent decline in production yields in the next 50 years for major crops between the latitudes of southern California or southern Europe to South Africa," said David Battisti, a University of Washington atmospheric sciences professor.
He is a coauthor of a Perspectives article in Science that urges food production experts, scientists and world leaders to begin thinking in dramatically different ways to meet food needs in a significantly warmer world. Lead author is Nina Federoff, science and technology adviser to Secretary of State Hillary Rodham Clinton.
"I grow increasingly concerned that we have not yet understood what it will take to feed a growing population on a warming planet," said Federoff, who also is a biology professor at Pennsylvania State University.
The challenge is becoming more difficult, the scientists said, because the world's population is likely to have increased more than 30 percent, to 9 billion people, by 2050.
Even without climate change, feeding all of these people will require doubling the grain production in the tropics, Battisti said, but a warmer climate will reduce yields because the temperature will be too high to achieve the most efficient photosynthesis. That factor, combined with less rainfall in major food-producing regions and increasing pressure from pests and pathogens, is likely to cut major food crop yields a minimum of 20 percent to 30 percent.
The authors advocate developing systems that have the potential to decrease the land, energy and fresh water needed for agriculture and at the same time reducing the pollution associated with agricultural chemicals and animal waste.
Battisti noted that the so-called green revolution in agriculture produced a 2 percent increase in yields per year for 20 years, primarily through development of new grain varieties and use of fertilizer and irrigation. But there is little, if any, new land available for farming, and such yield increases cannot be sustained without further innovation. In addition, there already are 1 billion people, mostly in the tropics, who do not have enough food for a healthy life.
"We're really asking for yield gains comparable to those at the peak of the green revolution, but sustained for an unprecedented length of time, 40 years, and at a time when climate change is acting against us," he said.
A major obstacle is that many of the institutions involved do not work together closely enough to succeed and, despite years of safe production and consumption, there is continued resistance to crops such as corn and soybeans that have been genetically modified to be insect resistant and tolerant of herbicides.
"There has to be a lot of creative thinking, a greater blending of biotechnology and agriculture and better coordination between private and public research efforts throughout the world for us to keep pace with the increasing demand for food," Battisti said. "We need to be thinking about the long-term demands for food and the environmental and social ramifications of how we will produce it."
The Science article represents the views of the authors and stems from a workshop they presented for the State Department last September in Washington, D.C.
Other authors are Roger Beachy of the U.S. Agriculture Department; Peter Cooper of the India-based International Crops Research Institute for the Semi-Arid Tropics; David Fischhoff of Monsanto Co.; Carl Hodges of The Seawater Foundation; Vic Knauf of Arcadia Biosciences; David Lobell of Stanford University; Barbara Mazur of the DuPont Experimental Station; David Molden of the Sri Lanka-based International Water Management Institute; Matthew Reynolds of the Mexico City-based International Maize and Wheat Improvement Center; Pamela Ronald of the University of California, Davis, and the Joint Bioenergy Institute; Mark Rosegrant of the International Food Policy Research Institute; Pedro Sanchez of Columbia University; Avigad Vonshak of Ben-Gurion University in Israel; and Jian-Kang Zhu of the King Abdullah University of Science and Technology in Saudi Arabia and the University of California, Riverside.
ScienceDaily (Jan. 9, 2009) — Rapidly warming climate is likely to seriously alter crop yields in the tropics and subtropics by the end of this century and, without adaptation, will leave half the world's population facing serious food shortages, new research shows.
To compound matters, the population of this equatorial belt – from about 35 degrees north latitude to 35 degrees south latitude – is among the poorest on Earth and is growing faster than anywhere else.
"The stresses on global food production from temperature alone are going to be huge, and that doesn't take into account water supplies stressed by the higher temperatures," said David Battisti, a University of Washington atmospheric sciences professor.
Battisti is lead author of the study in the Jan. 9 edition of Science. He collaborated with Rosamond Naylor, director of Stanford University's Program on Food Security and the Environment, to examine the impact of climate change on the world's food security.
"This is a compelling reason for us to invest in adaptation, because it is clear that this is the direction we are going in terms of temperature and it will take decades to develop new food crop varieties that can better withstand a warmer climate," Naylor said.
"We are taking the worst of what we've seen historically and saying that in the future it is going to be a lot worse unless there is some kind of adaptation."
By combining direct observations with data from 23 global climate models that contributed to Nobel prize-winning research in 2007, Battisti and Naylor determined there is greater than a 90 percent probability that by 2100 the lowest growing-season temperatures in the tropics and subtropics will be higher than any temperatures recorded there to date.
They used the data as a filter to view historic instances of severe food insecurity, and concluded such instances are likely to become more commonplace. Those include severe episodes in France in 2003 and the Ukraine in 1972. In the case of the Ukraine, a near-record heat wave reduced wheat yields and contributed to disruptions in the global cereal market that lasted two years.
"I think what startled me the most is that when we looked at our historic examples there were ways to address the problem within a given year. People could always turn somewhere else to find food," Naylor said. "But in the future there's not going to be any place to turn unless we rethink our food supplies."
The serious climate issues won't be limited to the tropics, the scientists conclude. As an example, they cite record temperatures that struck Western Europe in June, July and August of 2003, killing an estimated 52,000 people. The summer-long heat wave in France and Italy cut wheat yields and fodder production by one-third. In France alone, temperatures were nearly 6.5 degrees Fahrenheit above the long-term mean, and the scientists say such temperatures could be normal for France by 2100.
In the tropics, the higher temperatures can be expected to cut yields of the primary food crops, maize and rice, by 20 to 40 percent, the researchers said. But rising temperatures also are likely to play havoc with soil moisture, cutting yields even further.
"We have to be rethinking agriculture systems as a whole, not only thinking about new varieties but also recognizing that many people will just move out of agriculture, and even move from the lands where they live now," Naylor said.
Currently 3 billion people live in the tropics and subtropics, and their number is expected to nearly double by the end of the century. The area stretches from the southern United States to northern Argentina and southern Brazil, from northern India and southern China to southern Australia and all of Africa.
The scientists said that many who now live in these areas subsist on less than $2 a day and depend largely on agriculture for their livelihoods.
"When all the signs point in the same direction, and in this case it's a bad direction, you pretty much know what's going to happen," Battisti said. "You are talking about hundreds of millions of additional people looking for food because they won't be able to find it where they find it now."
He said wheat makes up one-quarter of the calories consumed in India, but growth in wheat yields there have been stagnant for the last decade.
Temperature increases from climate change are expected to be less in equatorial regions than at higher latitudes, but because average temperatures in the tropics today are much higher than at midlatitudes, rising temperature will have a greater impact on crop yields in the tropics.
Recent UW research has shown that even with much smaller temperature increases in the tropics, the impacts of warmer climate will be greater there because life in the tropics does not encounter much temperature variation and so is less adaptable. That makes an even stronger case to begin now searching for ways to deal with substantially warmer conditions, Battisti said.
"You can let it happen and painfully adapt, or you can plan for it," he said. "You also could mitigate it and not let it happen in the first place, but we're not doing a very good job of that."
The National Science Foundation and the Tamaki Foundation funded the research.