Helga Hissa used to get soaked to promote better water management. In presentations to groups of Brazilian small farmers, she’d stand tall as her boss dumped a cup of water on her head, pointing as her wild, curly hair soaked it up. He’d then pour some on a bald volunteer, watching it roll off the man’s scalp and down his back.

The same happens when rain hits deforested land, Hissa’s team at the state agriculture ministry argues. Without vegetation to absorb it, more rain rolls off soil, speeding erosion, polluting water with sediments, and preventing the speedy recharge of reservoirs that supply Brazil’s biggest cities. Hissa and her colleagues want farmers to plant trees to prevent that.

Across