translation.en: The rivers changed in response to the wolves, and the reason was that the regenerating forests stabilized the banks so that they collapsed less often, so that the rivers became more fixed in their course.
translation.zh: 河流因为 狼群的再出现而改变 因为新生长出的大片树林 使河岸稳固，于是滑坡减少 因此河道就更为稳固