Technology can boost farming in Africa, but it can also threaten biodiversity. How to balance the two

Cultivating one hectare of maize used to be an arduous task for Precious Banda, a farmer in Zambia. It would take her hundreds of hours to prepare her land before sowing and to keep it weed-free until harvest—equipped with nothing but a small hoe. She says it was backbreaking work: "I can still feel it." For a few years now she has hired a tractor, and a neighbor sprays herbicides for her. "Life has become so easy," she says.