When we lose the wild species of the plants we eat, we start running a huge risk that any future disease wipes out that whole cultivated species, and our existing ways to manage this (selective breeding, or transferring genes from the wild plant) lose the material they depend upon.

Coffee is one worrying example. It originates from Ethiopia and Sudan, in the mountains, at particular altitudes (temperatures). As temperatures rise, it grows higher — but we soon run out of soil on the mountain, or run out of mountain altogether.

http://www.kew.org/science-conservation/plants-fungi/environ...

No more coffee?! Now that could start a war.