While not "polluting firing ranges" can only be seen as a good thing, I'm not certain that ranges are greatly polluted anyway. Gallery ranges have backstops that contain fired rounds (barring odd strays that ricochet) and because these backstops "fill up" (sometimes causing the aforementioned ricochets) they are periodically dug out and the spent rounds sifted out for recycling.
Field firing ranges are a bit different because they don't have backstops so there is a clear possibility of pollution. At the same time they are, or certainly can be, wildlife havens with all sorts of species thriving because (odd as it may seem) they are wild open spaces with little to disturb the wildlife.
Counter - intuitive, yes, but still true. IIRC the MoD has Wildlife Officers whose function is to make sure (insofar as is practicable) that nature has a fighting chance. Pun deliberate.