By John Cannon Orangutans, like most of the world’s great apes, are struggling. Their numbers continue to drop as their habitat disappears, or they’re killed by humans for food, out of fear or for self-defense. And it’s happening despite an estimated $1 billion in spending on concerted orangutan conservation efforts since 2000. The ongoing slide has left biologists flummoxed about how to ensure the survival of the three species of the Pongo genus. Now, the authors of a recent study have posited how two sweeping, global conservation ideas might impact orangutan survival: the Whole Earth and Hal…