It's a tough debate. On one hand, bolts are not very visible and no wildlife is going to try to eat and choke on a bolt. On the other hand, it's permanently altering the rock, and bolts don't have an infinite lifespan. There are also cases of landowners disallowing white chalk (or chalk in general) because it visibly stains the rock and doesn't wash off very quickly.

Bolts allow cliffs to be used for recreational climbing, much like how trails alter the landscape, but allow the land to be used for recreational hiking. No human activity is 100% impact free, unfortunately.