Alternative energy sources of wind power and solar thermal power don't burn fossil fuels, but both affect populations.

Bird populations

Explanation:

Wind and Solar energy have been hailed as a good thing because they utilize natural forces and reduce pollution however they do pose some threats to wildlife especially birds.

Wind turbines have been shown to be lethal to birds when flocks of birds fly through them and solar panels have been known to attract birds which sometimes fatally crash into them thinking they are bodies of water.