Marlowe Hood Yahoo News 17 Jun 09;
PARIS (AFP) – By mid-century, climate change may have outrun the ability of Africa's farmers to adapt to rising temperatures, threatening the continent's precarious food security, warns a new study.
Growing seasons throughout nearly all of Africa in 2050 will likely be "hotter than any year in historical experience," reports the study, published in the current issue of the British-based journal Global Environmental Change.
Six nations -- Senegal, Chad, Mali, Burkina Faso, Niger and Sierra Leone -- are especially at risk because they will face conditions that are today unknown anywhere in Africa.
As a result, even the hardiest varieties of the continent's three main crops -- maize, millet and sorghum -- currently under cultivation would probably not tolerate the conditions forecast for these countries in four decades.
A trio of researchers led by Marshall Burke, a professor at Stanford University's Program on Food Security and the Environment, said urgent measures must be taken to stock seed banks and develop new varieties to stay a step ahead of Africa's shifting agricultural map.
"When we looked at where temperatures are headed, we found that for the majority of Africa's farmers, global warming will rapidly change conditions beyond the range of what occurs anywhere in their country," he said.
The study is based on a mid-range projection from the UN Intergovernmental Panel for Climate Change (IPCC) that forecasts an increase in average global temperatures by 2100 of 2.8 degrees Celsius (5.0 degrees Fahrenheit) over pre-industrial levels.
More recent research, however, suggests that the impact of global warming could be even worse.
MIT climate modelers, averaging 400 possible scenarios, have calculated that Earth's surface temperatures will jump 5.2 C (9.4 F) by century's end in the absence of rapid and massive measures to slash greenhouse gas emissions.
"This is not a situation like the failure of the banking system where we can move in after the fact and provide something akin to a bailout," said co-author Cary Fowler, head of the Global Crop Diversity Trust.
"If we wait until it?s too hot to grow maize in Chad and Mali, then it will be too late to avoid a disaster that could easily destabilize an entire region and beyond."
Over 40 percent of Africa's population lives on less than a dollar a day, and 70 percent of these poor are located in rural areas and thus largely dependent on agriculture for survival.
The authors note that "adverse shifts in climate can cause devastating declines in human welfare, and have been implicated in everything from famine to slow economic growth to heightened risk of civil conflict."
Burke and colleagues found that while most African nations will face unprecedented climates by 2050, they could anticipate future needs by stockpiling seeds from neighbouring countries with similar conditions today.
By mid-century, for example, local varieties of the staple maize in Lesotho -- which has one of Africa's coolest climates -- will be wilting in the heat.
Varieties that thrive in hotter climes grown in Mali today may well be adapted to Lesotho's future needs, and so should be set aside.
But that still leaves the six most vulnerable countries without any apparent solution.
"For these nations, there is a much smaller potential pool of foreign genetic resources in which to seek heat tolerance, at least within Africa," the authors caution.
African farms becoming too hot to handle
Bob Holmes, New Scientist 17 Jun 09;
African farmers will soon face growing seasons hotter than any in their experience. To cope with this rapid climate change, they – and the plant breeders who supply their crops – will need to make big changes, and soon.
Agricultural experts have predicted for some time that farmers are likely to face problems as climates become hotter and drier than they are today. Indeed, some farmers in South Africa are already reporting difficulties (pdf).
To see how fast, and how broadly, this will strike, Marshall Burke, an agricultural economist at Stanford University, and colleagues, averaged the results from 18 global climate models to forecast likely temperature and rainfall conditions in 2025, 2050 and 2075 in regions of Africa where maize, millet and sorghum are grown today. Then, assuming that year-to-year variability would remain the same as today – perhaps a conservative assumption – they asked how much these future climates would overlap with existing climates.
They found that farmers in Africa will face average temperatures outside the current range of experience in their locality in 42% of years by 2025 – and 97% by 2075. Since temperature strongly affects crop yields, farmers will need to find new varieties adapted to these higher temperatures, Burke says. Future rainfall showed more overlap with current conditions, largely because rainfall already varies more from year to year.
Maize trap
The researchers then looked to see whether the warmer temperatures forecast for 2050 can be found anywhere in Africa today. If so, they reasoned, these analogous conditions might yield crop varieties already adapted for the future conditions. A few lucky countries, such as Tanzania, Ethiopia and South Africa, have diverse enough climates today that they can find climates analogous to the potential conditions of 2050 within their own borders today, Burke's team found.
At the opposite extreme, Sahelian countries such as Chad, Mali and Niger may have nowhere to turn. "By 2050, they're going to be hotter than any current growing season in any maize country in the world," says Burke. Most countries, however, will be able to find analogous climates in other countries today.
That would be good news, except that plant breeders have done very little collecting of locally adapted varieties from some of the most likely analog countries, such as Cameroon, Sudan and Nigeria, Burke's team found. To cope with future climates, genetic prospectors must sample much more of the genetic diversity of crops in these countries – and those nations must then do a better job of sharing these genetic resources, says Burke.
"We've got to do something serious about agriculture and we've got to start now," agrees Gerald Nelson, an agricultural economist who heads research on agriculture and climate change at the International Food Policy Research Institute in Washington DC.
Journal reference: Global Environmental Change, DOI: 10.1016/j.gloenvcha.2009.04.003
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