Rise in carbon emissions has led to massive increase in trees and plants

From The American Thinker Blog:

If all the extra leaves growing because of increased CO2 in the atmosphere were laid end to end, it would cover a space twice the size of the continental U.S.

That's the conclusion of a new study conducted by 32 scientists and 24 institutions.

Whoops, so all the extra CO2 is causing trees to grow better. This is a bad thing how?