How to spend $50 million

A man plans to give away $50 million of his inheritance, according to the freakonomics blog. Here are his wishes:

1) I want to give it all away in ten years.
2) I want to give it away only in the U.S. — I can’t stand these people who give money overseas when we need it at home.
3) I won’t give a penny to schools. I think its unconscionable that Gates is paying for schools; that’s the government’s job.
4) I don’t want to give anything less than $1 million at a time. Meaning, no small grants.

Assuming that Mr. Wealthy also has the unstated goal of trying to help regular people in the US and he's willing to work on goals with a long-term payoff, here is the plan he needs:

Plan: Use all the money to buy large pieces of unpopulated land, to be owned and maintained by a foundation. The foundation's mission is to ensure that the land is never used by humans except, possibly, for light camping or other low-impact recreation.

Why spend the money this way?

• We must slow the spread of suburbia. Suburbia keeps people away from the cities, where it is possible to walk to work instead of burning gas to get there. Suburbia keeps people apart, preventing the formation of communities. Suburbia destroys wildlife, and messes up the countryside.
• Although the US is not densely populated compared to most other industrialized nations, our collective carbon footprint far exceeds a sustainable level. Taking land out of circulation will make people feel more crowded, and speed along the environmentalist movement by pushing people to make sacrifices sooner rather than later.
  
• Taking land out of circulation gives modern industrialization a much-needed margin of error. It is too early for us to understand the long-term consequences of our modern use of land and resources (it has only been in the last 20 years that global warming has come into our everyday language). If we wake up one day to realize that our farms can no longer produce thanks to our abuse, $50 million of extra land for a second try would sure come in handy.