> completely owning natural resources like lakes and forests

They wouldn't completely own them, they'd have property rights in them. Depending on how the property rights are structured you could have many owners of say a lake or a river.

> Those private entities would rationally take a long term vision

If there's anything we know about politicians up for re-election in two years or unable to run for another term it's that they take a long-term approach to problems. /s