Kenyan environmental activist Wangari Maathai, the first African woman to be awarded the Nobel Peace Prize, has died of cancer at the age of 71, her family announced Monday.
Tributes flowed in for Maathai, who died on Sunday at a Nairobi hospital while undergoing treatment, lauding her outstanding struggle against environmental degradation.
"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," a statement said.
Achim Steiner, director of the UN Environment Programme, described her as a "force of nature".
"While others deployed their power and life force to damage, degrade and extract short term profit from the environment, she used hers to stand in their way," Steiner said in a statement.
Maathai became a key figure in Kenya since founding the Green Belt Movement in 1977, staunchly campaigning for environmental conservation and good governance.
She won the 2004 Nobel Peace Prize for her reafforestation work in Kenya, the first African woman, the first Kenyan and the first environmentalist to receive this honour.
Her organisation has planted some 40 million trees across Africa.
US President Barack Obama expressed his "great sadness" to Maathai's family and the Kenyan people.
"The world mourns with you and celebrates the extraordinary life of this remarkable woman who devoted her life to peacefully protecting what she called 'our common home and future'," said Obama, whose father was Kenyan.
US Secretary of State Hillary Clinton praised Maathai as "a tireless advocate for the environment, for women and for all those in the developing world who are unable to realize their potential".
The first woman in east and central Africa to earn a doctorate, Maathai also headed the Kenya Red Cross in the 1970s.
Maathai had been diagnosed with ovarian cancer in July 2010, her family added, but never made the illness public.
"We must try our best to find something that will give us a little comfort -- the kind of comfort she herself would have given us," said family spokeswoman Vertistine Mbaya.
Aside from her conservation work, Maathai was elected a member of parliament in 2002 and then named the environment assistant minister, a position she held between 2003 and 2005.
"We mourn a global icon who has left an indelible mark in the world of environmental conservation," said Kenyan President Mwai Kibaki in a statement.
For more than a decade from the 1980s, her movement also joined the struggle against the dictatorial regime of Kenya's former president Daniel Arap Moi, with Maathai repeatedly teargassed and beaten by police.
During that time, she famously campaigned against the construction of a high-rise building in a park in central Nairobi, stopped the grabbing of forest land outside the city and successfully pressed for the release of 51 political prisoners.
Maathai in recent years founded green groups and launched several campaigns against climate change and environmental protection.
Outside Kenya, she was involved in efforts to save central Africa's Congo basin forest, the world's second largest tropical forest. Republic of Congo's Forest Economy Minister Henri Djombo expressed shock Monday at what he called "a great loss for the world environmental community".
Maathai, who was divorced, is survived by three children and a granddaughter.
"Professor Maathai’s departure is untimely and a very great loss to all who knew her as a mother, relative, co-worker, colleague, role model, and heroine, or who admired her determination to make the world a more peaceful, healthier, and better place," her family said.
Kumi Naidoo, the director of Greenpeace International, voiced sorrow at Maathai's death.
"It is a deeply distressing and painful loss, not only to the environmental movement globally but also to the social justice movement," Naidoo told the BBC.
Tanzanian President Jakaya Kikewete, in a Twitter message, said Maathai had been "an inspiration for many women across Africa, a magnificent visionary and embodiment of courage".
South Africa's Desmond Tutu, a fellow Nobel winner, said Maathai had "understood and acted on the inextricable links between poverty, rights and environmental sustainability".
"She was a true African heroine," Tutu added.
Nigerian environmentalist activist and Friends of the Earth International chairman, Nnimmo Bassey, praised her saying "she stood up to political powers and showed a serious commitment to the preservation of tree species in Africa. This is something that her departure should not stop."
In Senegal, the regional head of Femmes Africa Solidarite (FAS -- African Women Solidarity) said the continent has lost "one of its greatest daughters" who was a champion of environmental causes, for rural women and for tackling climate change.
Comments on a Facebook page set up to mourn her death said her "innovativeness and steadfastness will be greatly missed".
"You lived a good life, you fought a tough fight -- we stand on the shoulders of a hero," said Elizabeth Maloba. "Rest in peace, Mama Kenya," wrote Titus Mugo.© ANP/AFP