This is a well-known concern in land preservation. There's apparently an offshore island near Maine that's too small and too far out to be of much use to humans, but it's an important migratory bird resting point.
IIRC, it was donated to the state once by conservationists (long ago), sold by the state, and then repurchased and preserved by a non-profit foundation. The state won't be getting it again!
The usual approach in the US is for the land conservation foundations to split up the ownership rights between two different local organizations in a way that prevents developing the land without agreement from both organizations.
As a general rule, most towns are happy with this setup. It provides them with public walking trails, and possibly areas for other outdoor sports. Many towns choose not to tax these lands, within reason.