WHAT A YEAR for parties! Forum for the Future is ten, Resurgence is forty, and I, to my surprise, am sixty. A timely if terrifying moment to be asked for a personal reflection backwards and forwards about the green movement from the perspective of leadership.

It seems only yesterday I was rocking around the 1960s, enjoying Bob Dylan and the Beatles in Harold Macmillan's "you've never had it so good" world. My parents' generation sacrificed their youth to World War II so when they exhorted mine to enjoy ours we took it very seriously. Before long, however, evidence that our generation would face even bigger challenges seeped into our enjoyment of free education, safe streets and sex, and no job or pension worries.

Increasingly, the Cold War shaped the way political leaders ran the world. And it was a very male shape as both sides relaxed into the gang psychology of them and us, recruiting allies, and holding powwows. Meanwhile, people like me stock-piled canned food during the Cuba crisis, took to the streets about American intervention in Vietnam, and watched uneasily as the Berlin Wall went up. We also read about the way global - and local - ecosystems were straining to mop up our waste and pollution (including CO2 even then). The pile of evidence submitted to the first Earth Summit in 1972 was eleven feet high.

By the time that 'blue marble' image of the Earth taken by Apollo 17 appeared and became an iconic image of the global green movement, I had done a wholesale review of my life goals and was a paid-up campaigner for population, anti-poverty and environmental groups. Motivated by compassion for people (I used to be a nurse) I felt I should devote my life to trying to mitigate the pain of the clash between the aspirations of the human species and the clearly finite capacity of the Earth to support them.

So, like Resurgence I am also celebrating forty years of campaigning. The tactics we use may be different, but the direction of travel is the same - which is all that matters - though I remain worried about how much of the green movement forgets how much our campaign is about people. Nature knows how to endure and thrive. It is our species that has lost the plot. For me, sustainable development is about people choosing a path for our progress that is fair and will keep us happy, prosperous and safe for multiple generations. The historical mistake of capitalism and socialism has been to forget that the human story is played out in the natural world. The environment movement is in danger of making the mirror mistake by excluding the wellbeing of people from concerns about the wellbeing of the planet.

POLITICS IS, OF course, about power. And I joined the UK Green Party in 1977 because I wanted to get green ideas into power. In 1990 I gave a Schumacher Lecture: 'Politics Beyond Power'. My thesis was that there is no such thing. Power does not go away if you ignore it. Someone, somewhere, has got it and it can indeed be a force for good or bad. So how power is given, held to account, removed or relinquished deserves not necessarily a lot of pomp, but certainly much more circumstance.

A couple of years ago, the German Green Party hosted, in Washington, an international seminar on the progress of Green parties since 1983 when Die Gr