Wangari Maathai (wan-GAH-ree mah-DHEYE) is a woman of many firsts. She has worked tirelessly to improve the environment. Born in Nyeri, Kenya, in 1940, Maathai was the daughter of farmers and grew up with an appreciation of the importance of planting seeds.

For years, Maathai worked as a professor. She was the first woman in East Africa to earn a Ph.D. But she left her career to focus on the environment. In 1976, after recognizing the need to conserve the environment and improve the quality of life of Kenyan women, Maathai introduced the idea of planting trees as a way to accomplish both. A year later, she and other women founded the Green Belt Movement, an organization that plants trees across Kenya and at least 15 other nations in Africa. The group is the largest tree-planting project in Africa. So far, it has planted more than 40 million (per TIME 10/29/07) trees. The group's aim is to curb the destructive effects of deforestation and desertification.

In her years of activism, Maathai has been threatened, arrested and imprisoned. In 2002, Maathai won 98% of the vote to gain a seat in Kenya's National Assembly. The following year, she was appointed assistant minister of environment, natural resources and wildlife in the country's parliament.

Maathai was awarded the Nobel Peace Prize in 2004, making her the first environmental activist and the first African woman to win the prize since it was first given in 1901. The Nobel committee cited her "contribution to sustainable development, democracy and peace."

In 2006, Maathai was awarded France's highest honor, the Legion d'honneur (Legion of Honor), for her work on the environment and her efforts to bring about peace.