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.
川が狼への反応で 変わった理由は 再生している森林が 斜面を安定化させたことで 崩落の頻度が減り 川の流れが安定してきたのです