A new study on climate change warns that hotter weather and shifting rainfall patterns could ruin as many as one million square kilometers of marginal farmlands in sub-Saharan Africa by 2050.  Scientists say poor subsistence farmers may have to depend much more on livestock to act as a source for food and income. 

The study, conducted by researchers from the Nairobi-based International Livestock Research Institute, looked at climate change models and projections to determine what could be the worst-case scenario for subsistence farmers in semi-arid regions of West, East and southern Africa.

Senior scientist Phil Thorton tells VOA that while it is impossible to predict accurately how rapidly or severely climate change will affect those areas in the next 40 years, higher temperatures and unpredictable rainfall patterns are being observed on a wide scale.

"The area we have come up with is a very huge area, something like three percent of the land area in sub-Saharan Africa.  These are areas that are not heavily populated, likely to dry up somewhat in the future and where cropping may currently be possible even though it may be quite risky and variable.   What the results suggest is that, in some of these areas, cropping may become essentially impossible by the middle of the century," he said.

High levels of man-made carbon emissions are thought to be creating a greenhouse effect, trapping sunlight and heating the planet.

Not being able to cultivate staples such as maize, millet, and sorghum because of deteriorating growing conditions could mean a devastating loss of food and income for millions of poor subsistence farmers in Africa.  

The study says that farmers could avoid being wiped out by adding more livestock to their agriculture systems.   Animals, such as cows and goats, are much more tolerant of heat and drought than crops, and an increasing demand for meat and dairy products in Africa could make livestock production profitable as well.

The study does not say how much livestock a household should have in order to act as a sufficient buffer against the risk of climate change.  Thorton says scientists need to study that question in more detail.

"The next step is to maybe take a few case study locations and then really look at the household impact, so that we can say something about what kinds of changes these households might be facing and what they may do about it,  We certainly have some of the tools that could help us answer those questions," Thorton said.

Thorton says researchers are also hoping to pinpoint specific areas in Africa, where it may be appropriate to promote livestock ownership in a sustainable manner.