Well, since rabbits are hunted by both foxes and wolves, if those populations start to incline, they are going to need more food, hence, eating and killing more rabbits, which would bring their population down. Another reason is that if the grass doesn't grow plentifully, the rabbits won't have enough food to survive, since they eat grass, so their population will decline due to a lack of food.
That would be beneficial to them because they wouldn't lose as many trees to disease or insects, so they are able to sell more. That's what I got from it at least.
