Kenya\'s Wangari Maathai, who won the 2004 Nobel Peace Prize for her environmental work, has died of cancer, the campaigning movement she founded announced Monday. \"It is with great sadness that the family of professor Wangari Maathai announces her passing away on 25th September 2011 at the Nairobi hospital after a prolonged and bravely borne struggle with cancer,\" the Green Belt Movement said in a statement. Born in 1940, Maathai became a key figure in Kenya since founding the movement in 1977, staunchly campaigning for environmental conservation and good governance. Since its founding, her organisation has planted some 40 million trees across Africa. In the 1970s, she also headed the Kenya Red Cross. Maathai won the 2004 Nobel Peace Prize for her environmental work and reforestation in her native Kenya. She was the first woman in east and central Africa to earn a PhD, and also the first African woman and Kenyan to receive the Nobel Peace prize. Aside from her conservation work, Maathai was in 2002 elected an MP then named the environment assistant minister, a position which she held between 2003 and 2005. Outside Kenya, Maathai was involved in efforts to save central Africa\'s Congo basin forest, the world\'s second largest tropical forest. Maathai, who was divorced, leaves behind three children and a grandchild.