Answer:
The difference between a restrictive covenants and a habitat easement is that restrictive covenants usually last about 20 years or so, while habitat easements (especially through an easement in gross) can limit the use given to the land virtually forever.
The problem with a restrictive covenant is that only the parties can enforce the covenant since it is a private agreement. But if the parties change (the land is sold) then the new owners are not required to enforce the covenant, ans in case they can be forced, the restriction can be generally after 20 years or in the best case scenario a decade or two more.
On the other had, since an easement in gross defines the right to use land for a specific purpose, adjacent lots cannot object it and even f the land is sold or transferred, the easement remains.