>There is a tax loophole where you buy a lot of land and donate 90% of it to the government to be "public parkland". However, in actuality, you're the only person who has convenient access to this land

While I'm sure that's happened once or twice and serves as great fodder to get people of a certain ideological bent riled up, for the most part nobody is giving government land that's worth a shit. They're doing it to land that's effectively unusable due to regulation. Like if you own a strip that's a many acre 30ft wide along a steep river bank plus some space for a house (the lot layout could be the result of an old railroad or industrial thing) you gain literally nothing being on the hook for all that and you can't use it. That sort of thing is the typical case in which these sorts of things are invoked. It's more of a "well if you jerks care so much about what I do with it you can have it" type deal than a tax dodge.

It's actually a pretty common thing: https://www.propublica.org/article/conservation-easements-th...

It even sprouted a cottage industry of REITs selling investors a product built around it, syndicated conservation easements: https://www.propublica.org/article/syndicated-conservation-e...