In recent years, her one-woman crusade had concentrated on the plight of Lake Naivasha - one of Africa's richest and most imperilled bodies of water. Such was her standing, a section of the lake's shoreline had been named after her.
But in the early hours of yesterday Lake Naivasha may have cost the 69-year-old environmentalist her life.
Shortly after 1am, two assassins broke into the compound of her home on the banks of the lake, where she had lived for more than 30 years. The men breached the electrified fence and crept to the bedroom window of Mrs Root, who was born with British nationality, but had lived in Kenya all her life. On their way they shut off the alarm. They broke the window with an AK-47 Kalashnikov rifle and fired at least seven bullets into her sleeping body.
As the killers fled, Mrs Root used towels to try to staunch the bleeding from two gunshot wounds to her legs and one to her hips. She died from blood loss crawling towards her bathroom.
Kenyan Police hinted that Mrs Root's murder was linked to her fearless campaigning to protect Lake Naivasha's dwindling waters and wildlife.
Last year Mrs Root abandoned an anti-poaching programme after it became politically controversial. The conservationist set up the scheme to protect the lake against illegal fishing and wildlife poaching, but it was shut down amid an outcry from local communities.
Simon Kiragu, the police commander in Naivasha, 59 miles north-west of the Kenyan capital, Nairobi, said Mrs Root had been "very aggressive" in her conservation work. Officers were investigating any link between her activism and her murder.
Mr Kiragu said: "Nothing was stolen. The thugs just shot the deceased and left. We are trying to determine whether this was an assassination."
Last night a local man was under arrest after sniffer dogs examining the crime scene led to his home. A second man was still being sought.
Lake Naivasha has become the focus of Kenya's lucrative fruit, vegetable and flower industry, supplying produce to European supermarkets. In the space of two decades, about a dozen vast commercial farms have sprung up, placing the area at the heart of Kenya's £200m horticultural export business. Although the farms create jobs in the region, increasing the population from 50,000 in 1985 to 300,000, they have been a source of friction between local tribes and the farm owners, many of them white Kenyans, as they fight over how to manage the lake's fragile ecosystem.
The Masai community have been vitriolic in their criticisms of other Kenyan tribes and white settlers, who they claim are polluting the water and denying them access to ancestral lands. The Masai have also criticised the tourist lodges along the shoreline.
Mrs Root's murder is the latest in a series of attacks against white settlers in the region, which became known as Happy Valley after the drink-fuelled antics of the British settlers in the 1940s were immortalised by Evelyn Waugh and the film White Mischief.
Friends of Mrs Root, who became a Kenyan national in the 1970s, insisted she had not believed her life was in danger.
Adrian Luckhurst, a close friend and business associate, said: "Jane has lived on that property for over 30 years and I don't believe she would have left unless she was feeling jeopardised, and she never left."
Violent attacks on white European residents have nonetheless been on the increase.
Tensions between white settlers and villagers came to a head in April last year when Tom Cholmondeley, the heir to the fifth Baron Delamere, shot dead a Masai wildlife warden conducting an undercover investigation on the Delamere farm. Mr Cholmondeley said he had believed he was acting in self-defence.
John Goldson, the British owner of the upmarket Crater Lake Lodge in Naivasha, was killed last July by robbers.
As the police investigation continued, friends and colleagues paid tribute to Mrs Root, who became renowned in the 1960s and 1970s for pioneering wildlife films made alongside her then husband, Alan Root. Mr Luckhurst said: "Joan and Alan were some of the finest wildlife photographers in the world."
Mrs Root, the daughter of a British coffee farmer who moved to the Rift Valley in 1929, had lived alone in Naivasha since the end of her marriage, operating a small animal shelter where she kept waterbuck and dik dik (a breed of small antelope) and raised an orphaned hippo.
Mr Root, who had remained close to his former wife, travelled yesterday to her home from Nairobi to help recover her body.
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