Wangari Maathai, the first African woman to receive the Nobel Peace Prize and the founder of the Green Belt movement, died on Sunday in a Nairobi hospital after a long bout with cancer.

She received the Nobel Prize for encouraging poor Kenyan women to plant trees. During her acceptance speech in 2004, Maathai said she was inspired to get the women to plant trees after witnessing forests being cleared in her neighborhood as a child.

"The values she had for justice and civil liberties and what she believed were the obligations of civil society and government," Vertistine Mbaya, a peer and friend of Maathai’s, said to the New York Times. "She also demonstrated the importance of recognizing the contributions that women can make and allowing them the open space to do so."

Along with the Nobel Prize, Maathai was also the first East African woman to receive her doctorate. She earned the degree at the University of Nairobi in 1971, where she later became an associate professor.

According to a statement by the Green Belt Movement’s website, Maathai’s death was a loss to those who "admired her determination to make the world a more peaceful, healthier and better place.” Funeral arrangements are pending.

Maathai leaves behind three children.