Many bats are killed by the wind turbines.
Bat's resparatory ability can't cope with the sudden drop in air pressure created by the turbine brades. If many bats die, many insects increase. 
If there are many insects around the world, we can't live in a very good environment.
The wind turbines could have a destabilizing effect on eco system . Wind turbines are very nice for human beings but they are bad for bats and insects.
Moderate is very important. the nice thing for a something means bad for the other thing.