A different sort of green literature has developed in the past few years - and it is not the sort the Green Party will happily hand out at its conference this weekend.
This new literature began in 1998 when Bjorn Lomborg, once a deep green, began questioning the assumptions, methodology and statistics of orthodox green positions. Lomborg still claims to be green (as the Business Roundtable found when it brought him here to speak), but a sceptical one.
This emerging breed is not sceptical about pollution, biodiversity, climate change and so on but about alarmist proclamations and using regulation to change behaviour.
One recent apostate is New York Times columnist Nicholas Kristof, who wrote of greens recently: "Some do great work, but others can be the left's equivalents of the neo-cons: brimming with moral clarity and ideological zeal but empty of nuance.
"I was once an environmental groupie and I still share the movement's broad aims, but I'm now sceptical of the movement's 'I have a nightmare' speeches'," he wrote, citing a string of unfulfilled prophesies of disaster, the latest of which is that oil has "peaked".
Alarms are useful, Kristof said. "But environmental alarms have been screeching for so long that, like car alarms, they are now just an irritating background noise."
Worse, he said, greens were in danger of being typecast as "extremist". Nothing is ever enough, the planet is in peril and we humans are a degraded species.
That is something for our Green Party to think about this weekend as it goes into the 12th election that it and its predecessor, the Values Party, will have contested.
Since 1970 the green movement in and out of Parliament has won many battles - the big first victory being to stop a dam destroying the brooding, primeval beauty of Lake Manapouri. It has also influenced much policy, including the current Government's land transport policy. Both major parties, once brown and dirty, are much less so as a result.
But are the Greens reaching the limit of their influence?
Sounds a silly question: the smart money is on a third-term Labour government that needs the Greens for a majority. The Greens are ready and hungry for Cabinet posts, or at least a support agreement that delivers much more than their 1999 and 2002 support agreements.
But the smart money might be misplaced. First, National might beat Labour, and the Greens would not get the time of day from National, even if they felt like asking, which they wouldn't.
More to the point, even if National doesn't beat Labour, it should get much closer than in 1999 and 2002. Indeed, this might be the first election since 1981 in which the two big parties are fairly evenly matched, after seven asymmetrical elections.
If the race is close, the small parties might not gain support during the election campaign, as they have during the previous three elections since the switch to MMP voting. They might even lose support compared with their starting opinion-poll positions.
So it is not safe to assume that the Greens' poll average of a bit over 5 per cent will translate into 6 to 7 per cent in the election. The Greens might conceivably not be in Parliament.
The Greens have assembled a basket of mini-constituencies, which give them a respectable core vote: environmentalism and conservation, of course, but also safe food (including genetic modification), youth, legalisation of cannabis and peace. And they have added "the fairer society", picking up the Alliance's mantle on social services and social welfare.
Moreover, they mostly live their beliefs, which adds attraction.
So they should pull through this election - unless, that is, their environmentalism is beginning to sound to even some greenish voters like Kristof's "irritating background noise".
Three years ago the Greens hand-grenaded Labour's march to power with an intransigent line on GM food that cost both themselves and Labour votes and, paradoxically, cost them real influence. United Future picked up Green-fearing votes and became Labour's choice as primary support partner.
The GM food stance sounded extreme in 2002. It was a hardline regulatory approach. Much of the rest of the Greens' approach is similarly regulatory. They suspect the market and its instruments. Though most Greens are splendid people, you can get the impression from being around them that they also suspect humans.
But if sceptical humans are to be taken along a more environmentally sustainable route, regulation is hardly likely to get them to go willingly. The market and its instruments are proving more effective in other fields because they coax more than goad. Logically the same will increasingly apply in environmental issues.
Labour is slowly learning that lesson, against the grain of its own instinctively regulatory tradition. Maybe it is time for the Greens to do some of the same sort of learning. For all our sakes.