Older people are better known for protesting about pensions and council tax, but a growing number are setting their sights on protecting the planet.
Irene Willis reckons she has been arrested up to 25 times
This month saw the launch of a new transatlantic website, linking a growing number of grey-haired greens who are making the environment their cause.
One such campaigner is 61-year-old Irene Willis, who knew she was not cut out for the stereotypical pensioner's life when she retired.
So instead of crosswords and Countdown, she found another way to pass the time: as a direct-action environmental activist, chaining herself to fences and breaking in to nuclear bases.
In the four years since she discovered non-violent protest she estimates she has been arrested up to 25 times, and believes her age and appearance make her an asset to the movement.
"On demos, I can get away with murder," she laughs. "The police are much more lenient with grey-haired old ladies than with younger protesters."
Irene is typical of a new breed of ecology-conscious older people on a mission to save the world.
This month saw the launch of a GreenSeniors.org, a web-based network for older people set up by activists in the UK and US which hails Irene as a "green hero".
A poll for the UN World Environment Day last year found pensioners are the most eco-friendly age group in the UK: over 90% recycle their litter, four out of five take showers rather than baths and 79% use low-energy light bulbs.
This is because getting older makes you more concerned about what you will leave behind, Irene believes.
Her passion for fighting climate change, pollution and global injustice has seen her landed with £800 outstanding in court fines, which she refuses to pay. In 2004 her refusal to pay an earlier fine saw her jailed for 10 days in Edmonds Hill Prison, Suffolk.
A former infant school teacher with three grown-up children, she became hooked on direct action after joining the protest against nuclear weapons at RAF Lakenheath.
She went on to campaign against climate change and local developments near her home in Canvey Island, Essex, and has stood twice for parliament as a Green candidate.
Her militancy is a reaction to ageism, she believes: "When you get old, suddenly no-one listens to you anymore. Direct action makes me feel empowered.
"I've still got the energy to do all this and that won't last forever. I know I'm in the final years of my life and I want to make the most of it.
"I can afford to go to prison - I'm not going to lose my job, I'm not going to lose my house."
Time on their hands
The view that older people have more time and energy to devote to the cause is shared by Joyce Emery, 63, co-founder of GreenSeniors.org, a mother of one and grandmother of six from Ames, Iowa, in the US.
After retiring from her civil service job last year she threw herself into activism, setting up her own blog, GreenGranny.org, and bombarding her elected representatives with e-mails.
She says: "Younger people are so focused on getting ahead financially, on keeping up with expectations of what it is to be successful. Older people realise there is more to life.
At the age of 85, Amyan MacFadyen swapped his car for a bike
"When I was working, a daughter still at school and my elderly mother to care for, I had no time for anything else.
"But now I've got all this free time I want to use it productively. As you get older you become more concerned about the future of the planet, about what it will be like for your grandchildren."
Another activist who believes it is never too late to make your lifestyle more eco-friendly is Amyan MacFadyen from Sheffield, south Yorkshire.
Last year he decided it was environmentally irresponsible to drive a car. So he traded his own one in for a bicycle - at the age of 85.
"Sheffield is very hilly, so it's not all that good for bikes," he says.
"But I am very concerned about climate change and the catastrophic effect it's going to have on the Earth's population."
A former professor of Ecology and Environmental Science at the University of Ulster, he only turned to campaigning after retiring in 1986.
For 10 years he was convenor of his local branch of Friends of the Earth in Bannside, Northern Ireland. A keen gardener, he was popular for bringing his home-grown organic vegetables to meetings.
Last year he moved to Sheffield, where he joined local activists clearing parks and green spaces of litter and debris.
He adds: "I have four children and seven grandchildren, and it does make you worry about what sort of world they will live in."
With advocates like Amyan, Irene and Joyce on their side, green activists will hope that our ageing population will also be an increasingly eco-friendly one too.