Accra — Climate change could drastically alter the distribution of thousands of plant species across Africa, say scientists.
The researchers, led by Jon Lovett of the University of York in the United Kingdom, looked at 5,197 species of African plants -- about 10-15 per cent of the continent's plant species.
Using computer models that predict future climate, the researchers concluded that by 2085, the habitats in which nearly all of these plants can live would either shrink or shift, often to higher altitudes, as a result of anticipated changes in Africa's climate.
Lovett says the team did not look explicitly at the risk of species extinction, but at the loss of areas with a suitable climate for the plant species studied.
They say that for between one-quarter and one-half of the species they studied, there will be no part of Africa with a suitable climate by 2085.
The study will be published this month in the Annals of the Missouri Botanical Garden, a leading journal for research on African vegetation.
The researchers say changes will be particularly drastic in the forests of West Africa, stretching from Guinea to the Congo basin.
They believe the predicted changes in plant distribution could mirror the large-scale decline in West African forests that occurred 2,500 years ago during the last Ice Age.
Other areas expected to be hard hit are eastern Africa and the continent's south-west coast.
Climate change is a factor that needs to be taken into account when identifying areas in Africa that are important to plant conservation, say the researchers.
Lovett told SciDev.Net that his research suggests climate change could greatly reduce the availability of medicinal plants in Africa. According to the World Health Organization, nearly three-quarters of Africans rely on traditional medicines derived from local plants.
"This is an important piece of work, providing a more comprehensive picture of the threats to African plants from climate change than has previously been available," says Chris Thomas, also at the University of York, though not part of Lovett's team.
He says Lovett's team estimates are based on conservative estimates of future climate change.
Last year, Thomas and colleagues published research in Nature that claimed that a substantial proportion of the world's biodiversity was under threat of extinction from climate change (see Climate change 'threatens one million species').
The study came under fire from researchers at the University of Oxford who doubted the possibility of predicting with accuracy the fate of global biodiversity using a computer model of just 1,103 species, as the authors had done.
They also criticised the press announcement issued to the media, which claimed that a quarter of land animals and plants could eventually go extinct if climate change was left unchecked (see Inaccurate media reports hinder conservation efforts).
The changes predicted by Lovett's team do not necessarily imply that the species will go extinct, but ecologists tend to agree that significant reductions in the area a species can inhabit will reduce their likelihood of survival.
"The percentage of species at risk of extinction is expected to increase with atmospheric carbon dioxide concentrations," says Thomas. "These emissions are changing the climate, and effectively exporting extinction to other parts of the world, including Africa. Therefore, the obvious answer is to take action to minimise atmospheric carbon dioxide levels."
Lovett's team compared the climate in 1975 to future scenarios predicted for 2025, 2055 and 2085 using climate models created by the UK Met Office's Hadley Centre.
They used three distinct computer models to predict which plants would be affected by changing climate. Although the models disagreed on the exact extent of the problem, they each suggested that changes to Africa's vegetation would be profound.