Deforestation
Every day, an area the size of continental Europe is completely stripped of trees. Most of these are used to make toothpicks, telegraph poles and ornamental model trees. What a waste! Without Nature (ie. trees an' shit), our planet will wither and die, and probably crash into the sun or something.
We at Earth Cow don't want to see that happen. That is why we have sent an expedition deep into Fangorn Forest to uncover the lost Treeherders - the Ents. Once they see the destruction humans have wreaked upon the forests of the world, they will be so angry that they will kill our expedition team instantly, then bomb the whole world with lava.
Problem solved.