A widespread farming catastrophe could hit Africa if global temperatures rose by four degrees Celsius or more, according to a study that calls for urgent planning for a much warmer future and investment in technology to avert disaster.
In most of southern Africa the growing season could shrink by as much as a fifth, according to scientists at the International Livestock Research Institute (ILRI) in Kenya, who carried out simulation studies based on existing climate change models.
The 'four degrees plus' scenario is increasingly being contemplated as negotiations, which began again in Cancún, Mexico, today (29 November–10 December), have stalled on measures aimed at limiting the global temperature rise to two degrees.
Drastic changes to farming will be needed under such a scenario, said Carlos Seré, director-general of ILRI.
"The general feeling is that the world is not going to move quickly enough on [confining global warming to] two degrees," he told SciDev.Net: "We are not getting traction.
"The common thinking has been that there will be enough variability in farming today to allow us to cope, but the reality is that in a four degree world the range of options is very narrow."
According to the models, the growing season may increase modestly in eastern Africa. But cropping seasons are likely to decline more quickly everywhere in the region except central Africa.
Much of southern Africa's rain-fed agriculture could fail every other season by the 2090s, says the study.
"It is not difficult to envisage a situation where the adaptive capacity and resilience of hundreds of millions of people in Sub-Saharan Africa could simply be overwhelmed by events."
Simply making crops more drought-tolerant or flood-resistant is just tinkering about the edges, said Seré.
"The changes which will be required in the farming system are quite drastic, pushing farmers beyond the limits of their knowledge and experience. They will be overwhelmed by extreme climate events," he told SciDev.Net.
"We are talking about farmers abandoning cropping and migrating out of those regions. But where are farmers who cannot cope with this level of stress in the system to go?
"Where is the alternative livelihood for 60 per cent of the continent where farming is still a very key part of coping with food security? You cannot escape the fact that for decades many people are going to be in the rural sector. It is a moral imperative to give those people a livelihood.
"We need to understand and find much smarter ways to get knowledge out there. Extension services in Africa have largely collapsed in many countries".
The Intergovernmental Panel on Climate Change Fourth Assessment Report in 2007 assumed that regional shortfalls in food production in Sub-Saharan Africa could be plugged with imports from global markets, says the paper, but it adds that the experience of the 2008 food crisis highlighted the difficulties of such an 'adaptation' strategy.
Instead ILRI scientists are calling for better monitoring, in particular 'back to basics', land-based observation and data collection in Africa, which have been in decline for decades. Information on weather, land use, markets and crop and livestock distribution is critical for an effective response to climate change, they said.
"Africa's data-collection systems could be improved with relatively modest additional effort," the study says.
Philosophical Transactions of the Royal Society, Series A doi: 10.1098/rsta.2010.0246