A research project headed by a joint team of UK and Ghanaian scientists has led to the discovery that the carbon storage capacity of protected forests in West Africa has increased, despite the region suffering from a 40-year drought. University of Leeds professor Dr. Sophie Faust, who co-authored the paper, said that the initial aim of the project was to capitalize on the unique dataset available from Ghanaian forests in order to investigate potential global threats to the carbon sink stored in tropical forests.
Tropical forests are known to be a crucial component of the global carbon cycle, containing around 40% of terrestrial biomass. The team noted that any changes to this system would have crucial consequences for the global carbon balance. What they also found was that despite the drought that has gripped the area for the past several decades, the tree composition in the country had changed to favor species that were able to cope with drier conditions.
It has flown in the face of all previous studies that have suggested that as drought conditions increase, less carbon is able to be stored due to vegetation dying. Speaking to BBC News, Sophie Fauset said: “Despite the long-term drought, there was no biomass loss in the forests. In fact, the biomass actually increased during that period.”
The findings have been published in the journal Ecology Letters and note that the increase in biomass has meant that carbon still remains locked away in the vegetation.
“We think it is the result of a shift in species composition,” Dr Fauset said. “Because you have got this long-term environmental shift, it is possible for the species composition of the forests to reshuffle slightly, so the species that can survive under those conditions are favoured. This means you are getting less negative impacts of the drought.”
Due to the region’s 40 year drought, rainfall has fallen by up to 23% compared with pre-1970 levels. The team found their results ran counter to what they thought would have occurred during such conditions.
“It is generally thought that if you have droughts then you are going to see a decrease in biomass,” she added. “Certainly, studies that have looked at short-term, quite extreme droughts do seem to show biomass loss.
“It could be that the increase in biomass (recorded in this study) could be the result of something else, but we think that the maintenance of the forest structure, despite the drought conditions, is a result of a change in species composition. This basically means that you cannot take those short-term studies of extreme droughts and extrapolate the findings to a long-term event with different kinds of precipitation changes. It is very important for the global carbon cycle that these forests are maintained.”
+ Ecology Letters
Images: chrisinwales and chadskeers