Kagerou Osajima
I understand how you feel. Every house I've lived always had yards backing up to untouched patches of woodland... and I loved playing there with friends as a child. Whenever I've gone back... I never fail to find that while the houses are still there, the forest have disappeared only to have more development in its place.
Unfortunately, there's not a lot you can do... especially if its private property. You might try finding our whom owns the land, and make an appeal to them. (But developers pay a lot of money for land... it would be hard to persuade them out of their cash..) If the land is public, you might try petitioning.... will take some research either way.
If they're building houses, it's likely been sold to a developer, were it public in the first place...
Sadly, in these cases there isn't too much anyone can do.