"Climate change models suggest the Sahel should be getting drier but observations suggest it is currently getting wetter," Jon Lovett of the University of York in Britain said on the sidelines of a conference on climate change in Johannesburg.

"This could lead to an increase in food production and population, but this will be bad if it suddenly goes into another cycle of drought which cannot support all of the additional people and livestock," he said on Monday.

"It has cycles of boom and bust." Lovett said the Sahel was relatively green during the 1940s through to the 1960s, but since then it has gone into a dry phase that seems to be ending.

Intriguingly, he said research done more than a decade ago linked a wetter Sahel to increased hurricane activity in the Gulf of Mexico - and this appeared to be occurring in the wake of the devastation wrought by hurricanes Katrina and Rita.

Global effect

"This shows that what is happening in Africa can have an affect on the Gulf of Mexico," he said.

The Sahel is a transition zone between the arid Sahara to the north and the wetter more tropical areas in Africa to the south.

It includes Senegal, Mauritania, Mali, Burkina Faso, Niger, Nigeria and Chad.

Niger is experiencing a famine this year brought on by poor rains and locust swarms, underscoring the region's vulnerability.