NAIROBI, Kenya — Wangari Maathai, the Kenyan environmentalist who began a movement to reforest her country by paying poor women a few shillings to plant trees and who went on to become the first African woman to win a Nobel Peace Prize, died here on Sunday. She was 71.

The cause was cancer, said her organization, the Green Belt Movement. Kenyan news outlets said that she had been treated for ovarian cancer in the past year and that she had been in a hospital for at least a week before she died.

Dr. Maathai, one of the most widely respected women on the continent, played many roles — environmentalist, feminist, politician, professor, rabble-rouser, human rights advocate and head of the Green Belt Movement, which she founded in 1977. Its mission was to plant trees across Kenya to fight erosion and to create firewood for fuel and jobs for women.