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.
Os rios mudaram em resposta aos lobos, e a razão é que as florestas regeneradas estabilizaram as margens de maneira  que elas sucumbiam menos, assim os rios ficavam  mais fixados no percurso.