These chimpanzees manage to cross the jungle road in Guinea unmolested. But for many of their conspecifics, the roads built into the forests in many African countries mean the beginning of the end.
Chimpanzees are our closest relatives, but they have to fight to survive. Especially the populations of the western chimpanzee (Pan troglodytes verus) are shrinking rapidly. “The Western chimpanzees were once common all over West Africa, but in the last 20 years their population has declined by 80 percent,” explains Balint Andrasi of the University of Exeter. One of the reasons is their dwindling living space due to the increasing competition with humans. “The human population in West Africa is growing rapidly and the chimpanzees are exposed to increasing pressure from the expansion of settlements and infrastructure,” said Andrasi.
A decisive factor here are roads that increasingly cut through the last remaining intact forest areas, as Andrasi and his colleagues have determined. “Only 4.3 percent of their area of distribution is not crossed by roads, so the chimpanzees hardly have any chance of escape and migration over longer distances is unusual for these animals,” explains the researcher. In addition: “Western chimpanzees are highly territorial, so that they come into conflict with neighboring groups of chimpanzees when trying to relocate.”
As a result, contrary to what was long thought, roads do not lead to the great apes being displaced and moving to other areas. Instead, they are directly linked to the sharp decline in stocks. As Andrasi and his team discovered, the disruptive effect of a road extends an average of 17 kilometers into the forest on both sides. Even smaller forest paths still have a disturbance radius of a good five kilometers. In addition, roads are often only the beginning of human activity in a region.
“Our great ape cousins are threatened from so many sides – from the disappearance of their habitat to hunting to disease. And infrastructure development also has a greater impact than I would have ever assumed, ”says Andrasi. “But we mustn’t give up. I can’t imagine a world in which we humans are the only remaining hominids. “