Last Monday, at the Lambeth Conference, Bishop Winston Halapua from Polynesia spoke about a meeting of churches from various Pacific islands where the subject for discussion had been neither social justice nor personal ethics, but the bare fact of rising ocean levels. Within a very few years, the likelihood is that several small islands will simply become uninhabitable.

Nothing could have brought home more directly the issue that the conference discusses this Saturday – the church's responsibility for the environment. While scepticism about climate change is still given astonishing prominence in some western media, the day-to-day reality of rising water levels is not a matter of debate for our colleagues in the Pacific. Part of the importance of the Lambeth Conference to us all in the Anglican Church is that it lets us hear these things in first hand detail.

But this vignette of the global problem offers a potent image of one of the deep underlying issues in the environmental debate. We live in a world of finite space and finite resource. Endless trajectories of growth are not realistic; and our own rising "oceans" of food and fuel prices are a stark reminder that scarcity is not someone else's problem in today's and tomorrow's world.

Somehow, conventional political discourse has not dealt with this very successfully. Time was when part of the wisdom of conservative politics was about limits, realism, adjusting to certain givens in the social and material environment, and moderating expectations. Unfortunately, this proved all too often to be a way of recommending the disadvantaged to accept their fate; and progressive politics was thus frequently allied to a passionate belief in endless possibilities of self-improvement and more sophisticated control of the environment. You have only to think of the utopian aspirations of the French Revolution or of the Soviet Union in the 1920s.

And when a drained and abused environment takes its revenge, we seem often very confused. Rather bizarrely, the environmental family of issues is seen in some quarters as a sort of liberal conspiracy, another turn of the screw for liberal guilt, and therefore to be treated with the same robust scorn as all other fashionable and self-indulgent moralising. But at the same time, a progressive politics still finds it very hard to let go of its legacy. If emancipation and the advance of human capacity don't simply mean economic growth without limit, what do they mean?

This, perhaps, is why so many have come to recognise that the environmental debate is going to be hamstrung and impoverished without some clear spiritual perspectives. Contrary to what some would say, religious belief is in significant measure a way of acknowledging limits that are shared by all human beings – the limits involved in bodily dependence on a friendly environment, and in the fact of death. Faith proposes that finding your way within these limits (including awareness of death) is how we lead lives that have some claim to rationality and – to use the religious word – grace.

For believers, and very clearly for Christian believers, this is connected with the recognition that the world is God's before it is ours – never just a possession – and that we are in God's hands in life and death. But even a person who does not share the basic conviction might think what a politics would like that went beyond conventional "right" and "left" stereotypes to work out how we coped meaningfully with real, non-negotiable limits – not resentfully or in wilful disregard of reality, but meaningfully. The polarised categories simply don't work well here. Something more radical and more traditional is called for.

© Rowan Williams