The Elephant nose (trunk) is long because this is the part of their body that determines their survival. The nose is fused with their upper lip. This elongated part of their body determine how much food they can consume. Research proposes that the elongated nose is as a result of evolution, the Elephant has this long nose as a means of adaptation for survival in it's habitat.
It is also believed that the trunk evolved to accommodate the Elephant's tusks. They also have long legs and large head, it would be difficult for such an animal to reach the ground to feed without the long nose. The elongated nose also help them feed on grass while they remain in the same position.