About 2,500 years ago, chimpanzees helped regenerate African rainforests by dispersing the seeds of oil palms. Today, those same forests are threatened again, as are the chimpanzees.
Covering nearly three million km2, the Congo Basin forest in Central Africa is the second largest tropical forest after the Amazon rainforest. It’s also one of the oldest. In fact, it was massively fragmented between 2,500 and 3,000 years ago.
Until a few years ago, scientists believed that humans were responsible for this decline. This belief was largely motivated by the presence of oil palm pollen remains preserved in the mud of the surrounding lakes. These trees, now planted on an industrial scale, have always been an important source of nutrition for the inhabitants of the region.
Recently, analyzes carried out in a pollen laboratory in Montpellier focusing on African forest history suggested a different story. “There, my simplified view of fossilized oil palm pollen suggesting the presence of humans was totally overturned,” explains Alex Chepstow-Lusty, now at Cambridge University.
This research has indeed made it possible to clarify the available data, finally ensuring that the virtual decimation of tropical forests had taken place around 2,500 years ago in the Congo Basin and over a vast area extending from modern Senegal to Rwanda. .
However, archaeological evidence suggests that the human presence in these regions was quite small and sparse at that time. In other words, humans, who can be responsible for many ills on Earth, this time had little to do with the destruction of this forest on such a rapid scale and on such a large scale.
So what caused these massifs to collapse? Turns out the answer is just as familiar to us: climate change.
The work of Alex Chepstow-Lusty, accompanied by researchers Pierre Giresse and Jean Maley, has indeed shown that Central and West Africa had suffered a major prolonged drought season around 2,500 years ago. Tropical forests then fragmented, giving way to “savanna” type vegetation made up of scattered grasses and shrubs.
In the centuries that followed, the forests then regenerated rapidly, including with species like the oil palm. The large seeds of these trees being too heavy to be “carried” by the wind, some animals have therefore necessarily disseminated them through their excrement.
For researchers, chimpanzees, who happily revel in the bright orange flesh of these large fruits, have likely played a crucial role in the regeneration of these African rainforests.
Today, these same forests are again facing the risks of climate change. However, there are other dangers. Due to the overexploitation of wood, deforestation is indeed important, which leads to a decrease in biodiversity.
The bushmeat market is also helping to eliminate key species from these regions, such as chimpanzees. At the beginning of the 20th century, there were still a million in these forests. Today, there are only less than 300,000 left in the wild.
The problem is that without animals to move the seeds, especially the larger and heavier ones, the natural makeup and regeneration of these forests is threatened. Therefore, apart from ethical motives, the valuable services provided by these animals should be taken into consideration to better protect them. As a result, we could help to conserve the forests themselves.