A legacy of deforestation has left Ethiopia struggling with more intense flooding and drought. The country is trying to restore its native forests through one of the world’s most ambitious and well-funded tree-planting campaigns, but such projects in other nations have often fallen short.

Niku Argane’s farm sits on a steep hillside in central Ethiopia’s semi-mountainous Gurage Zone, where years of flooding have carved deep gullies through the land. Soil that once produced enough barley and potatoes to feed his wife and four children — and left a surplus to sell in the market — has eroded, while drought has made what land remains harder to cultivate.

“We have never stopped farming, but our production declined because of land degradation,” the 32-year-old said from his farm in Ambele Kebele.

Over the last century, Ethiopia nearly eradicated its forests as trees were cleared for farming, grazing, and fuel.…