Their dams cause floods, and that gets them in trouble with humans. But in the right place, more water can be a big help.

© Kim Raff for The New York Times

Although nature is sometimes very fragile, decades of conservation rhetoric have perhaps overstated that fragility.

Farmers in Northwest China confront their drying landscape by planting trees as coal burns relentlessly nearby. This film tells a human story behind an element from the periodic table: carbon.