A new study has shown that deforestation in the rainforests of West Africa reduces the amount of rain that falls over the rest of remaining forest.
The study, conducted by researchers from the University of Leeds and published in the journal Geophysical Research Letters, is based on the results of simulations run on a Met Office computer that showed rainfall under different land-use conditions.
The result showed that by planting crop land in place of the rainforest reduces the rainfall over the remaining forest by approximately 50%.
This is due to changes in the surface temperature which affects the formation of rain clouds above.
“We already know from satellite observations that changes in land use can have a big impact on local weather patterns. Here we have been able to show why this happens,” said lead author of the study Dr Luis Garcia-Carreras, from the University of Leeds School of Earth and Environment. “Our findings suggest that it’s not just the number of trees removed that threatens the stability of the world’s rainforests, the pattern of deforestation is also important.”
The total amount of precipitation was relatively unaffected, but rain over the new croplands was increased by four to six times, whereas rainfall over the remaining forest cut by half or even more.
“African rainforests already have the lowest rainfall of any rainforest ecosystem on Earth, which could make them particularly sensitive to changes in local weather patterns,” said Dr Garcia-Carreras.
“Therefore if rainfall is reduced even further as a result of deforestation, it could threaten the survival of the remaining forest by increasing the trees’ sensitivity to drought.”
Study co-author Professor Doug Parker, also from the University of Leeds, added: “While our study only focussed on a small region in Africa, it’s reasonable to suggest that this mechanism could be common in other global forests based on similar observations of rainfall in Amazonia.”
“This has implications for planners in terms of how deforestation is managed. If forest must be removed to create cropland, we need to think about what are the shapes and distributions of deforestation that will be least damaging to the adjacent forests and national parks.”