After describing how Chevron has gone out of its way to ensure the minimum environmental impact possible in the Kutubu Oil Fields of New Guinea by stringent regulation and partnership with environmental agencies and local government, Jared Diamond, in the book Collapse discovers another side effect of this environmental consideration:

... I discovered to my astonishment that these species are much more numerous inside the Chevron area than anywhere else that I have visited on the island of New Guinea except for a few uninhabited areas. The only place I have seen tree kangaroos in the wild in Papua New Guinea, in my 40 years there, is within a few miles of the Chevron camps; elsewhere, they are the first mammal to become shot by hunters, and those few surviving learn to be active onlt at night, but I saw them active during the day in the Kutubu area ... That's because there is an absolute prohibition against Chevron employees and contractors hunting any animal or fishing by any means in the project area, and because the forest is [still] intact.

I never would have thought of an old field as a nature preserve.