One of Kenya's most beloved figures, Maathai died Sunday after a yearlong battle with cancer. Her illness was not widely known until after her death in a Nairobi hospital.
Maathai won the 2004 Nobel Peace Prize for her work on sustainable development, democracy and peace. She believed that environmental degradation and unbridled development were among the roots of poverty.
"You cannot protect the environment unless you empower people, you inform them, and you help them understand that these resources are their own, that they must protect them," Maathai said on the website of the environmental movement she founded, the Green Belt Movement.
She started the group in 1977, encouraging poor women to collect native tree seeds in the wild, cultivate them and set up tree nurseries for a livelihood, paying them a small sum for any trees they planted. One aim was to ensure that poor families had access to sustainable firewood for cooking and water for drinking.
"I came to understand that when the environment is destroyed, plundered or mismanaged, we undermine our quality of life and that of future generations," she said in a speech accepting the Nobel Peace Prize. "Tree planting became a natural choice to address some of the initial basic needs identified by women. Also, tree planting is simple, attainable and guarantees quick, successful results within a reasonable amount of time."
She soon realized it was useless to struggle for environmental improvements without having democratic, accountable government, and her movement embraced human rights and democratic issues.
All her life, she battled government corruption and corporations that put profits and development ahead of the interests of the population.
She was a thorn in the side of the government of Daniel arap Moi in the 1980s and '90s, and was arrested for treason, harassed and beaten several times.
She also exasperated her husband, who divorced Maathai in 1979, reportedly complaining that she was "too educated, too strong, too successful, too stubborn and too hard to control."
Maathai issued scathing remarks about the Western consumer culture, which she said was unsustainable because it was based on the rich few consuming more and more at the expense of the poorest people in developing countries.
When she accepted the Nobel Peace Prize, Maathai said she drew her inspiration from her childhood in a rural Kenyan village in the central highlands.
"As I was growing up, I witnessed forests being cleared and replaced by commercial plantations, which destroyed local biodiversity and the capacity of the forests to conserve water," she said.
"My fellow Africans, as we embrace this recognition, let us use it to intensify our commitment to our people, to reduce conflicts and poverty, and thereby improve their quality of life. Let us embrace democratic governance, protect human rights and protect our environment," she said, adding that Africa must solve its own problems.
Born April 1, 1940, Maathai grew up in rural Kenya and received a scholarship to study at Mount St. Scholastica College in Atchison, Kan., where she majored in biology, graduating in 1964.
She went on to study for her master's degree at the University of Pittsburgh. She was inspired by a group of environmental activists pushing for clean-air regulations, her first view of environmental activism. She also studied in Germany, returning to the University of Nairobi in 1969 to complete her doctorate, the first Kenyan woman to earn such a degree.
Under Moi's increasingly autocratic government, with corruption rampant, Maathai angered the government from the president down, with protests against unbridled development.
Moi called her "a madwoman" and said she threatened Kenya's security.
In 1989, she successfully led protests against the construction of a 60-story building in Nairobi's Uhuru Park. In 1992, she and other members of a pro-democracy group were arrested and charged with treason. The charges were dropped after intense international pressure.
The same year, she was arrested during a hunger strike demanding the release of political prisoners. She lost consciousness when police beat her on the head, sparking international condemnation. Early the next year, the political prisoners were freed.
In 2002 she was elected to parliament as part of the opposition Rainbow Coalition that defeated the ruling Kenya African National Union party. She served as deputy minister for the environment and natural resources but was defeated in 2007, after one term.
But she continued to press for improvements in democracy, accountability and human rights across Africa.
"Time and again, post-independence African governments have been unprincipled or blatantly corrupt, beholden to only a small set of cronies or elites," she wrote in a commentary for The Times in 2009. "Too many in leadership positions have plundered national resources, persecuted political rivals and citizens who dared to question their actions, and even stoked violence within and across national borders, all the while crushing the hopes of ordinary citizens to make an honest living. Few have consented to share power freely or supported development of a vibrant civil society."
When Kenya's 2010 constitution was being drafted, she and the Green Belt Movement successfully pressed for the inclusion of a clause guaranteeing Kenyans the right to a clean and healthy environment.
She campaigned on climate change and often expressed anger that decades after she began her environmental movement, activities that threatened the environment and the planet's future went on unabated.
"In the course of history, there comes a time when humanity is called to shift to a new level of consciousness, to reach a higher moral ground. A time when we have to shed our fear and give hope to each other," she said in her speech accepting the Nobel Prize.
Survivors include three children and a grandchild.