I'm sure a solution could be found to control possum populations without killing them. I just don't get why killing is so often the "obvious" way of solving problems, and I mean problems with humans just as much as I mean problems with animals.
Besides, killing OBVIOUSLY doesn't work. Otherwise there wouldn't be a "possum problem" anymore, right? Without knowing much about these animals, I assume that their populations are self controlling, i.e. if you kill one, there will be a new possum taking its place. If you kill 100, there will be 100 new ones with the next generation. If you kill 1000, then they will make 1000 new babies.