WORLD VIEW/PAUL GILLESPIE:"CONTEMPORARY capitalism and a habitable planet cannot coexist." So runs the editorial summary of a book by James Gustave Speth, dean of the Yale School of Forestry and Environmental Studies.

"Today's system of political economy, referred to here as modern capitalism, is destructive of the environment, and not in a minor way but in a way that threatens the planet," he writes in The Bridge at the Edge of the World: Capitalism, the Environment, and Crossing from Crisis to Sustainability(Yale 2008).

It is an important message from such an influential and mainstream figure in the environmental movement, who served with the Carter and Clinton administrations and was head of the United Nations Development Programme from 1993 to 1999. He believes we must change the very nature of corporations so that they become legally accountable to society at large and not just to themselves and their shareholders - striking a blow against the embedded "externalities" sacred to orthodox economics which allows firms to pass on environmental costs.

The current obsession with GDP growth at all costs must be abandoned, shifting the emphasis to human welfare in a post-growth strategy where jobs, communities and environments are no longer sacrificed. Likewise, a shift to a post-consumer society is needed. So is a shift to much more participative and popular forms of democracy, capable of joining up environmental and social issues to tackle climate change coherently and urgently.

Yale says Speth is no Marxist, since he is not attacking capitalism in its ideal and theoretic form. But he has concluded that faced with overwhelming evidence of the planet's degradation - a process that the most recent scientific research shows is happening much faster than is popularly realised - it is necessary to transform the system of consumer-style growth capitalism. The end of the cold war has made it easier to contemplate that prospect in the US. And he is confident that the international social movement for change will grow stronger by coalescing peace, social justice, community, ecology and feminist campaigns into an international "movement of movements".

In a week in which the Guardianreported two of the UK government's chief scientific advisers saying it needs to plan for a four degree rise in global temperatures compared to pre-industrial times, rather than the three degree increase factored into the Kyoto negotiations, or the two degrees preferred by most climatologists (and the EU), Speth's message is timely indeed.

Globally, a four degree rise would be catastrophic. The 2007 Stern Review for the UK government concluded it would involve a huge rise in coastal and inland flooding as sea levels rise and winter rainfall increases, requiring urgent investment in coastal defences and depopulating vulnerable areas.

Ireland is equally exposed to such eventualities. It is interesting to contemplate Speth's critique of growth/consumer capitalism as we struggle with the impact of recession on the Celtic Tiger, since just such an adjustment would be needed in the developed economies if global warming is to be kept to two degrees by 2050.

Nicholas Stern, a former chief economist for the World Bank, argued in his report on The Economics of Climate Changethat a two degree objective would in fact not be viable for existing growth-oriented capitalism. He concluded that the three degree objective is more realistic if that system is to be maintained, despite the manifest ecological risks. It is cheaper to take action sooner than later; this would reduce global GDP by only 1 per cent and because of technological innovation "tackling climate change is the pro-growth strategy for the longer term".

Speth may be no Marxist, but his work is taken seriously by the Monthly Review, the principal Marxist journal in the US, an excellent publication which takes the ecological crisis very seriously - unusually so compared to other such periodicals. Its current issue is devoted to it (www.mrzine.org). Its editor John Bellamy Foster is the author of a brilliant study of Marx's ecology, showing how he took full account of the relations between man and nature in theorising capitalism. Foster develops the idea of a metabolic rift between them under capitalism, because of the system's inherently expansionary, accumulatory character. He argues that this has now reached ecological limits as a worldwide system after the cold war.

Foster dismisses Stern's optimism about technology because innovation is harnessed to a deeper logic of expansion, which the world ecology can no longer sustain. Thus capitalism cannot solve climate change, but must be transformed if human civilisation is to be preserved.

These are big ideas, rightly so given the threats involved. It is interesting to see them being developed most forcefully in the US, as its population becomes disenchanted with consumerism. Such speculation has led certain people to conclude that environmentalism "is profoundly hostile to capitalism and the market economy", as Nigel Lawson put it in a paper published in 2006. He disputes the scientific evidence for global warming, along with a host of other ideological deniers. Stern's significance was to invert such arguments by showing a reformist way forward.

Speth's importance is to bring the relationship between capitalism and climate change into mainstream debate, where it should stay. As the Monthly Reviewpoints out, what we call "the environmental problem is in the end primarily a problem of political economy". If that is so we are in for a rocky ride indeed.