If the dire predictions of Gaia Hypothesis inventor James Lovelock are to be believed, then human-induced climate change has already gone past the point of no return. He paints an apocalyptic picture of the near-total collapse of civilisation by the end of the twenty-first century, with billions of people dead and only scattered bands of survivors in the remaining habitable areas of the Arctic. In short, it's the sort of thing that a single generation ago would have been predicted in the aftermath of the global nuclear war some then thought inevitable.

Lovelock is certainly going out on a limb here: the only other major figure I can think of who has said anything like that was Martin Rees, the Astronomer Royal, who said in 2003 that he thought humanity had only a 50/50 chance of making it through the next century. So it would be unfair to say that Lovelock's recent predictions of doom are shared by the wider scientific community. However, the evidence in favour of, at the very least, serious problems is piling up. One point amongst many is the fairly recent discovery that trees emit so much methane that simply planting huge forests may be useless - if not actively counterproductive - in combating carbon dioxide emissions.

Now the gloomy bit on my part. I'm 31 years old, and given a little luck and reasonable health would hope to be about a third of the way through my life. Except that I'm starting to wonder, quite seriously, whether in some decades' time I might in fact be the architect of my own death - taking some high-tech equivalent of a cyanide capsule because the planet has become so unbearably hostile to ordinary human life. It's true that the Earth has been as warm before as even the high-end predictions for the end of the century - but that was 100 million years ago, and there weren't six billion humans to support.

I think that our best hope for the future is the one course of action that we - governments, corporations, communities, individuals; all of us - don't seem to be willing to undertake: a drastic cutting back of polluting activity, even at the cost of a shrinking economy. There's no point in having a thriving economy in a dying world. So... are you prepared to stop flying abroad on holiday? To give up your second homes in the country? To stop driving cars for pleasure or in city centres? To use public transport whenever you possibly can, even if you have to wait half an hour at the bus stop? To stop buying out-of-season fruit jetted in from the other side of the world? To turn off your TVs rather than leaving them on standby? And are you prepared to do all of that now?

Didn't think so. Me neither. I don't think most of us really have the determination to do what, in our hearts, many of us know is necessary. I envy and admire those who do. Of course governments and other such bodies are most culpable - building a new runway anywhere, Heathrow or otherwise, is an utterly barking idea when the projected growth in air travel by 2030 would totally wipe out the few gains we have made in the UK - and somehow we need to get across to developing countries such as China and India that just because we wrecked our environment doesn't give them the right to do the same. And yes, maybe there'll be some wonderful technological breakthrough - a working cold fusion reactor, say.

However, we can't go on pretending that other people, other countries, the government, big business - everyone but us - are the problem. We all are. We only have one planet, and we stand or fall together. It can't really support six billion people anyway, but we have those now and even less insane policies on contraception from the Vatican (some hope) wouldn't change that. Much of the world's wheat, for example, comes from areas that are fairly marginal for good harvests as it is - now imagine a world in which Canada's and Russia's wheat harvests failed year after year and you'll see one very possible future.

I realise that many people - perhaps most - reading this piece will think me wildly pessimistic, even though I am in fact less so than Lovelock. I hope, most fervently, that they are right. But I fear that we've become so used to the "I want it, therefore I will have it" consumer society that the necessary change in the necessary time-frame will be almost impossible unless we let the scales fall from our eyes. We have two choices: change the way we live and accept a slight reduction in our standard of living, or risk not being able to live at all. The status quo may well be our death warrant.