Linehog,
Acid rain and many other things contribute to the habitat equation. If a farmer grows 100 acres of corn each year and acid rain kills off 50% of that corn he still can only support he can't raise more cattle than he can feed with a 50% return on his corn. Same with deer. If acid rain is damaging the habitat then there needs to be less deer for the habitat.
http://en.wikipedia.org/wiki/Carrying_capacity
Carrying capacity usually refers to the
biological carrying capacity of a
population level that can be supported for an
organism, given the quantity of food,
habitat, water and other life infrastructure present.