Before WW2 we were a nation of about 100 million people. There are roughly 310 million in the same space today.

For better or worse we are a different nation. To the good this means we have manpower to do a lot of stuff. Not so good more people means our desires to do as we damn well please are going to conflict with other people's desires.

But more people doesn't necessarily mean a loss of wilderness. Japan has a lot of people in a very small nation but they work very hard at maintaining forests, parks, remote areas. There are very tight restrictions on what you can do in them but wild areas are there and the Japanese have made sure they will be there in the future.

The simple fact is that lot of people living in a small area makes most of their activities more efficient. NYC is one of the most efficient places on earth in terms of energy use and productivity.