a loft-like bedroom looks down over the home’s living room and out upon the forest. Despite its rustic charm, 100 Railroad Ave. isn’t a turn-of-the-century logger’s church anymore.

If you see a forest in Ethiopia, you know there is very likely to be a church in the middle, says Alemayehu Wassie. Wassie, a forest ecologist, has spent the past decade on a mission: preserving ...