Bird watching has convinced Doctor Science of the necessity of hunting:
[B]irders notice problems of wild animal overpopulation, as well as rarity. In many parts of the U.S., including New Jersey, there are serious overpopulation problems with Canada Geese and especially with White-Tailed Deer[pdf]. Deer don't just strip gardens of almost everything except daffodils and peonies, they can devastate all the natural undergrowth in an area, with terrible effects on native plants and animals.
This is in addition to the direct risk to humans of deer-car collisions and of Lyme Disease. Every experienced driver I know in my area has hit a deer at one point or another, and everyone who spends a lot of time outdoors has had Lyme Disease.