Warming may trigger agricultural collapse

India could lose up to 40 percent of its agricultural output because of global warming even as it becomes the world's most populous country, warns a new study. Global farm productivity faces "serious damage" this century, and poor countries will bear the worst of it, unless emissions of greenhouse gases blamed for climate change are held in check, says veteran climate economist William Cline. He further contradicts analysts who have said that global warming could boost yields. "My work shows that while productivity may increase in a minority of mostly northern countries, the global impact of climate change on agriculture will be negative by the second half of this century," said Cline, who has studied the economic aspects of climate change since the early 1990s. "There might be some initial overall benefit to warming for a decade or two but, because future warming depends on greenhouse gas emissions today, if we delay action it would put global agriculture on an inexorable trajectory to serious damage," he added. Cline sees global agricultural productivity falling by 3-16 percent by the 2080s, with worse damage in the following century because of even greater warming. Separately, the UN Food and Agriculture Organization reports that the world's grain harvest is falling because of severe weather. Increasingly, animals compete with humans at the shrinking trough: Meat production is increasing and most of it is raised on grain. Cline's study was released Wednesday by the Center for Global Development and Peterson Institute for International Economics. A senior fellow at the privately funded Washington think tanks, he based his projections on temperature and rainfall models used by the pre-eminent scientific brain trust on the issue, the Intergovernmental Panel on Climate Change. Could his expectations turn out to be unduly dismal? Some researchers have said that advances in farm science -- from seeds bio-engineered to resist drought to better management systems -- will boost harvests sufficiently to offset any losses from global warming. Cline counters that the so-called green revolution is losing steam, with annual growth in global yields slowing from 2.8 percent a year in the 1960s and 1970s to 1.6 percent since around 1980. "With additional investments in technology and adaptation, the effect of climate change on actual agricultural production could be reduced but, because these inputs raise the cost of production, prices would also rise," he said. Poor countries already have average temperatures near or above crop tolerance levels and, assuming that no significant dent is made in greenhouse gas emissions, seem set to suffer an average 10-25 percent decline in agricultural productivity by the 2080s, Cline said. Rich countries, which typically have lower average temperatures, will experience a much milder or even positive average effect. The fall in food production projected for India -- 29-38 percent -- takes on extra significance because the country is likely to have passed China as the world's most populous nation by mid-century. Countries with smaller numbers of people face outright agricultural collapse, however. Cline says Sudan, wracked by civil war fueled in part by failing rains, could suffer a 56 percent plunge in agricultural production and Senegal, a 52 percent decline. China and the United States stand among the world's worst polluters yet they seem relatively insulated from direct harm. China could escape major damage overall because it is further from the equator than most developing countries. Southern and central parts of the country remain at risk, however. Significantly increased yields in northern parts of the United States are expected to offset projected falls of 25-35 percent in the southeast and the southwestern plains. At best, US planners can expect 8 percent growth in agricultural output; alternatively, they might be in for a 6 percent loss. Among other wealthy countries, Australia stands to lose 16-27 percent of its food production to global warming. The difference in possible outcomes depends in large measure on uncertainty about plant-growth benefits from an atmosphere richer in carbon dioxide. Because plants absorb carbon dioxide from the air, scientists have suggested that as concentrations of the gas in the atmosphere rise, plant growth will increase. This so-called carbon fertilization effect has been shown to take place in laboratory experiments but gains have been smaller in open-air field experiments. Cline's less gloomy projections assume a substantial carbon fertilization effect but he warns that this is far from certain. Conversely, productivity losses could exceed his worst expectations depending on factors likely to accompany climate change but not reflected in the models he used. These include insect pests, severe drought, and scarcity of water for irrigation. In any case, the implications will be global, said Nancy Birdsall, president of the Center for Global Development. "Governments and millions of poor people in developing countries have limited ability to cope with such changes," Birdsall said. "At least a billion people live in the poorest countries that are likely to be worst hit by this slow-moving crisis. This will be a serious problem for us all."