A grove of huarango trees sits amid the sand dunes at the edge of Ica, Peru. The trees help balance the arid valley, capturing moisture coming from the west. Tomas Munita for The New York Times

Peruvians pose what might be a final challenge to the fragile ecosystem supported by the huarango near the southwestern coast of Peru. Villagers are cutting down the remnants of these once vast forests. They covet the tree as a source of charcoal and firewood.