GOD created such a wonderful, balanced eco-system with wide variety of species, plants, organic/inorganic materials, landscapes, minerals, AIR, WATER, LIGHT and an environment that itself tries to maintain the balance.
We speak different languages so do the animals; may be the plants too!
But why do we speak different languages? At least human and animals; I understand the fact that each species has its own role in food-chain. So if they speak a common language- then, maybe, when we decide to kill a chicken it will run away!
Is that the only reason? Assume a world as in cartoons where we can communicate with animals; we can achieve much more in life or ease our life a bit more in that case. Isn't it?!