Climate change could devastate South Asia, Africa crops: study

Mira Oberman Yahoo News 31 Jan 08;

Climate change will cause severe crop losses in Africa and Asia within the next 20 years unless farming practices are changed, a study released Thursday has found.

Those crop losses could lead to food shortages and a loss of livelihood among the world's poorest people, the authors warned.

And since it typically takes 15 to 30 years to for major agricultural investments to be fully realized, work must start soon to help subsistence farmers increase their yields and switch crops, the study published in Science magazine said.

"The majority of the world's one billion poor depend on agriculture for their livelihoods," said lead author David Lobell of Stanford University's Program on Food Security and the Environment.

"Unfortunately, agriculture is also the human enterprise most vulnerable to changes in climate," he said.

"Understanding where these climate threats will be greatest, for what crops and on what time scales, will be central to our efforts at fighting hunger and poverty over the coming decades."

Lobell and his colleagues used 20 different climate change models to determine the most likely impact of global warming on agriculture in 12 regions where the bulk of the world's malnourished people live. This included much of Asia, sub-Saharan Africa, the Caribbean and Central and South America.

"To identify which crops in which regions are most under threat by 2030, we combined projections of climate change with data on what poor people eat, as well as past relationships between crop harvests and climate variability," Lobell explained.

They found that southern Africa could lose more than 30 percent of its main crop maize, while South Asia's production of regional staples including millet, maize and rice was projected to drop by 10 percent or more.

"We were surprised by how much and how soon these regions could suffer if we don't adapt," said co-author Marshall Burke, also of Stanford University.

"For poor farmers on the margin of survival, these losses could really be crushing."

The picture is less certain in other areas such as parts of West Africa where it is unclear how global warming will impact the local climate.

"For these regions, you get half of the climate models telling you it's going to get wetter and the other half giving you the opposite," Burke said.

"As a result, our study raises the potential for very bad impacts in these regions but with much less certainty than in other regions."

A few developing regions, such as the temperate wheat-growing areas of China, could actually benefit in the short run from climate change, he added.

While relatively inexpensive changes, such as switching crops or altering planting seasons, could trim the losses, "the biggest benefits will likely result from more costly measures, including the development of new crop varieties and expansion of irrigation," the authors wrote.

"Consideration of other social and technological aspects of vulnerability, such as the existing adaptive capacity in a region or the difficulty of making adaptations for specific cropping systems, should also be integrated into prioritization efforts," they concluded.

Warming May Cause Crop Failures, Food Shortages by 2030
Mason Inman, National Geographic News 31 Jan 08;

Impoverished farmers in South Asia and southern Africa could face growing food shortages due to climate change within just 20 years, a new study says.

Increasing levels of greenhouse gases, including carbon dioxide, are heating up the planet, with droughts and shifting rainfall patterns predicted for many parts of the world.

"The majority of the world's one billion poor depend on agriculture for their livelihoods," said the lead author of the new study, David Lobell of Stanford University.

"Unfortunately, agriculture is also the human enterprise most vulnerable to changes in climate."

Climate change will affect some places more than others, so Lobell and colleagues focused on 12 regions where most of the world's impoverished live and the crops that the poor tend to grow and eat in those places.

They identified two hot spots—South Asia and southern Africa—where higher temperatures and drops in rainfall could cut yields of the main crops people grow there.

"We were surprised by how much, and how soon, these regions could suffer if we don't adapt," said study co-author Marshall Burke, also at Stanford.

Corn, Wheat at Risk

The researchers used computer models to predict changes in temperature and rainfall as the planet warms.

Most of the 12 regions were predicted to warm up about 1.8 degrees Fahrenheit (1 degree Celsius) by 2030—about the same amount of warming that Earth as a whole experienced over the 20th century.

"To identify which crops in which regions are most under threat by 2030, we combined projections of climate change with data on what poor people eat, as well as past relationships between crop harvests and climate variability," Lobell said.

The predictions from the various climate models often didn't agree on rainfall changes, he noted. But the overall analysis did suggest that southern Africa and South Asia were two spots where hotter temperatures and lack of water are most likely to stress crops.

"By looking systematically across regions and at a wide range of crops of importance to the poor, we hope to provide a way to prioritize investments in adaptation," Lobell said.

In southern Africa, corn (also known as maize) is a major crop, but it will suffer especially, the study suggests.

Lobell and colleagues predict about a 30 percent drop in corn yields there, along with a 15 percent drop in wheat yields, and smaller drops for soybeans and sugarcane.

They predict a small increase in rice yields for the southern Africa, and little change for sorghum or cassava.

In South Asia, on the other hand, almost every major crop would suffer a decline of about 5 to 10 percent, with only soybeans experiencing a slight gain in yields, the study predicts.

Changing which crops are cultivated in these areas could help populations cope with climate change, the authors argue.

They report their findings in this week's issue of the journal Science.

A Global Impact

Taking a global view of crop yields could be important because the markets are globalized, and worldwide decreases in yields could drive up food costs, argues a commentary also published in Science.

Molly Brown of the NASA Goddard Space Flight Center in Greenbelt, Maryland, and Christopher Funk of the University of California, Santa Barbara wrote the commentary.

By making fundamental changes, these regions could cope much better with today's problems and those to come with climate change, they say.

"Transform these agricultural systems through improved seed, fertilizer, land use, and governance, and food security may be attained by all," Brown and Funk write.

Tom Sinclair, an agronomist at the University of Florida in Gainesville who was not involved in the study, said, "The big unknown is water."

Climate models, including those used in the new study, don't agree on how rainfall will change in the coming decades, Sinclair says.

In addition, he says, the new study's approach of looking at average rainfall and temperatures misses what's most important for plants.

"What gets them is extremes [of] hot or cold," Sinclair said. "Or if you have episodes where the rainfall is spread apart, where the crops are more vulnerable to drought, then that's a real problem."

Like Brown and Funk, Sinclair also calls for more spending on improved crops, especially breeding drought-resistant produce.

"If I had a stack of money, that's where I'd put it," Sinclair says.

Climate 'could devastate crops'
BBC News 31 Jan 08;

Climate change could cause severe crop losses in South Asia and southern Africa over the next twenty years, a study in the journal Science says.

The findings suggest southern Africa could lose more than 30% of its main crop, maize, by 2030.

In South Asia losses of many regional staples, such as rice, millet and maize could top 10%, the report says.

The effects in these two regions could be catastrophic without effective measures to adapt to climate change.

The majority of the world's one billion poor depend on agriculture for their livelihoods. Yet, said lead author David Lobell, it is also "the human enterprise most vulnerable to climate change".

The researcher, from Stanford University in California, added: "Understanding where these climate threats will be greatest, for what crops and on what time scales, will be central to our efforts at fighting hunger and poverty over the coming decades."

'Crushing' losses

The study used computer models to assess the impact of climate change on farming in 12 world regions where the bulk of the world's malnourished people live. This included much of Asia, sub-Saharan Africa, the Caribbean and Central and South America.

"To identify which crops in which regions are most under threat by 2030, we combined projections of climate change with data on what poor people eat, as well as past relationships between crop harvests and climate variability," Dr Lobell explained.

The scale and speed of the effects on agriculture surprised the scientists.

"For poor farmers on the margin of survival, these losses could really be crushing," said co-author Marshall Burke, also of Stanford University.

All the models agree that there will be adverse effects on maize in southern Africa and rice in South-East Asia, but the picture is less certain in other areas such as parts of West Africa where it is unclear how global warming will impact the local climate.

Early investment

"For these regions, you get half of the climate models telling you it's going to get wetter and the other half giving you the opposite," said Dr Burke.

"As a result, our study raises the potential for very bad impacts in these regions but with much less certainty than in other regions."

A few developing regions, such as the temperate wheat-growing areas of China, could actually benefit in the short run from climate change, he added.

Since it typically takes 15 to 30 years for major agricultural investments to be fully realised, work must start soon to help subsistence farmers increase their yields or switch crops, the study says.

While relatively inexpensive changes, such as switching crops or altering planting seasons, could trim the losses, "the biggest benefits will likely result from more costly measures, including the development of new crop varieties and expansion of irrigation," the authors wrote.