China is not a country where ordinary people have much chance to influence government, and being an activist can be risky. But when it comes to environmental lobbying, there are signs the system may be changing, reports Mukul Devichand.
In the shadow of the Great Wall of China, I watch men in blue overalls hack at the soil of the forest floor and carefully plant new saplings.
Ancient woodland, new politics, in the shadow of the Great Wall
They are trying to restore this depleted ancient woodland to the high international standards of the Forest Stewardship Council.
Sustainable forests like this are a symbol of how things are slowly being changed by the new kids on the political block in China: green activists.
Charismatic campaigner Wen Bo has lobbied against deforestation, which he says has caused violent dust storms and floods - and a host of other effects.
He is not like most Chinese politicos, with a stylish haircut and a fleece jacket rather than a Mao suit. But what really sets him apart is the language he uses.
"We are not passively being governed, being ruled by the government," he told me. "We have our rights."
This is electric stuff in the world's biggest one-party state. Some outsiders hope that movements like his will give birth to a civil society - and even democracy - in repressive China.
They hope that China's reaction to the epic environmental consequences of its growth - with a quarter of drinking water contaminated - will allow people power to break free and put a brake on pollution.
But on a visit to Beijing to meet activists and experts on the environmental movement, I found it hard to gauge the size and effectiveness of this new green political space.
The limits of tolerance
None of the environmentalists I spoke to risk lobbying for democracy or challenging the political system overtly.
Wen Bo: Intelligence agents sometimes pose as green volunteers
"That would be like throwing an egg against a stone," says Wen Bo.
Instead they work together with officials who will listen. The activists say their ideas, such as "public participation," fit into a Communist Party framework.
It seems to be working somewhat on paper, with the central government recently upgrading the main environmental agency to a ministry.
Official statistics say there are now over 2,000 "green" NGOs. One unofficial study says there are up to two million informal groups of students, farmers or other activists. Several campaigns have received positive coverage in the state-controlled media.
But Wen Bo told me intelligence agents sometimes pose as green volunteers to keep an eye on what's going on.
And it's still not unusual to see activists arrested - one was recently charged with subversion. So is green politics making any real difference?
A Chinese Erin Brockovich
Zhang Jingjing, who works at a centre that helps pollution victims get legal aid, has been called the Erin Brockovich of China because of some famous victories in class action cases.
Zhang Jingjing: The main problem is the judiciary
In 2005 she worked with the centre's boss, Wang Canfa, to help residents of a village in Fujian Province successfully sue a factory for compensation.
The factory was poisoning local crops with chromium - the same chemical Ms Brockovich fought in California.
But Ms Zhang sees limits to China's "green political space" because of the clout polluters have with local governments and judges.
In a country focussed on economic growth, factories and developers allow local officials to boost their area's GDP figures. The officials in turn pressurise judges.
"We have no independent judiciary, that is our problem," she says.
Because local officials and judges often side with polluters, the greens see central government as their ally. It's an internal power struggle in China that outsiders rarely see.
So although the activists do challenge the government, they themselves say it would be premature to call them a democracy movement.
Instead they are seeking much more basic mechanisms of accountability, like planning law and public hearings, which still don't exist in China.
What's more, many Chinese green activists don't see their own system as the sole cause of the problem. Instead, they blame the West.
I met Xiao Wei, the popstar whose message of love and green harmony inspired several of the 30-something activists I'd met, back when they were teenagers.
Given his soft style and hippy lyrics, I expected him to rail against the consumerism of today's China, with its 10-lane highways and enormous shopping malls.
Instead he said: "Everybody has the right to pursue a good life, to buy a big house or a car if they want to."
He pointed out that China is still a developing country and that much of the pollution is actually caused by factories which make products for the West. The waste generated by "Made in China" products is left for Chinese people to deal with.
Chinese environmental groups call this "the outsourcing of harm".
The basic dilemma for China is that polluting factories mean cheap exports, and potentially more jobs for the 300 million still living on less than $1 a day.
Chinese green groups often face the taunt that they put nature above the needs of the poor.
But Lo Sze Ping, the young director of Greenpeace's Beijing branch, thinks this very dilemma will force China's ecologists to come up with creative technological solutions.
"Imagine if China could produce solar panels just like China is producing DVD players now," he says.
"It would genuinely kick-start an energy revolution, not just in China but for the world."
Mukul Devichand's report for Analysis on Radio 4 can be heard at 2130 British Summer Time on Sunday 13 April.