What is important about rabbits?

They help with overflow of plants, vital for the food web, and are, well, sometimes needed to survive in wilderness areas -when there is no food (they're sometimes good to eat you know).

Also, without them, the whole food chain would get messed up and there would be too much grass and the animals that eat rabbits would then die of. The animal who ate that animal would die off and more animals would become extinct.