Environmentalists progressive? I think environmentalism is right wing and generally in tandem with the idea 'market forces' must dictate economics and political policy. It's why the Greens are such hippie pricks and can only get elected in Islington on Sea.
I know what you mean, although I dont think I'd put it quite like that, especialy as some flavours of environmentalism are certainly not in alignment with market forces.
The Green party is too far from actual power to judge properly. Its kind of easy to assume they are either hippies or a environment-focussed version of the lib dems, but a look at their last election manifesto revealed plenty that was more along the lines of socialist stuff. But I cant sensibly judge them by their words since they can take all sorts of decent-sounding positions, safe in the knowledge that their stance will not be tested by the realities of power.
As for the wide array of people who could be called environmentalists or who are fascinated by subjects such as peak oil, take your pick from a broad palette of stances and motivations such as:
Hippies.
Animal lovers, including those who may hold animals in higher regard than humans.
Haters of empires, corporations, certain ideologies and economic systems, or other related aspects of the status quo. They may see peak oil or other energy/resource/environmental disasters as either a damning indictment of these forces that they hate, or the means by which these forces may end up killing us all, or the weaknesses which will eventually bring these hated enemies to their knees, broken and obsolete, robbed of their life-blood, setting us free.
Those with a great interest in certain industries, sciences, systems, data, who think they have noticed numerous warning signs in the data that will surely impact in a massive way eventually, so lets not kid ourselves eh.
People with either rational or irrational fears about human 'progress', especially on the social, economic and scientific fronts.
Those who reckon the scale of the world is just too bonkers and imagine a simple correction where total population must drop greatly. Depending on their politics they may be fearful of this possibility, or cold and matter-of-fact about it, or may actually relish the prospect, or some uneasy mixture of all these things and other baggage I wont bother going on about now.
Some with more personal fears, whether it be for their childrens future, or NIMBY environmentalism brought about simply by a development that threatens their own neck of the woods. Or those who treat their own bodies like a temple and may be hyper-alert to the risks of various forms of pollution or chemicals in the food chain that may threaten their own personal health.
Fans of certain specific energy technologies, who get excited about the prospects of these things and get driven crazy by the fact it isnt happening on a scale grand enough to feed their hopes and expectations. And given that some of the barriers to progress on these fronts is due to the status-quo, it is easy to maintain faith in the tech of choice, failures can all be blamed on the orrible old hydrocarbon forces getting in the way, or market farces. This enables the avoidance of conclusive testing as to whether any fatal limitations that are not merely caused by the follies of humankind exist, eg ones down to physics, ones that will scupper the dreams of scaling these technologies to the level required.
Those with an interest in the rather extreme sorts of consumption we have built into life in many parts of the world and turned into our baseline expectation, and the equally extreme contrasts between this way of life and the poverty many still live in.