Do you feel it's a waste of time trying to prevent climate change? That reducing your carbon footprint is pointless when someone else is happy to increase theirs? That changing lightbulbs is a futile gesture? Well don't, says Michael Pollan, because even small changes in your lifestyle - and your thinking - can help save the world

Why bother? That really is the big question facing us as individuals hoping to do something about climate change, and it's not an easy one to answer. I don't know about you, but for me the most upsetting moment in An Inconvenient Truth came long after Al Gore scared the hell out of me, constructing an utterly convincing case that the very survival of life on earth as we know it is threatened by climate change. No, the really dark moment came during the closing credits, when we are asked to ... change our lightbulbs. That's when it got really depressing. The immense disproportion between the magnitude of the problem Gore had described and the puniness of what he was asking us to do about it was enough to sink your heart.

But the drop-in-the-bucket issue is not the only problem lurking behind the "Why bother?" question. Let's say I do bother, big time. I turn my life upside-down, start biking to work, plant a big garden, turn down the thermostat so low I need the Jimmy Carter signature cardigan, forsake the clothes dryer for a laundry line across the yard, trade in the SUV for a hybrid, get off the beef, go completely local. I could theoretically do all that, but what would be the point when I know full well that halfway around the world there lives my evil twin, some carbon-footprint doppelgänger in Shanghai or Chongqing who has just bought his first car (Chinese car ownership is where America's was back in 1918), is eager to swallow every bite of meat I forswear and who is positively itching to replace every last pound of CO2 I'm struggling no longer to emit. So what exactly would I have to show for all my trouble?

A sense of personal virtue, you might suggest, somewhat sheepishly. But what good is that when virtue itself is quickly becoming a term of derision? And not just on the editorial pages of the Wall Street Journal or on the lips of the American vice-president, Dick Cheney, who famously dismissed energy conservation as a "sign of personal virtue". No, it seems the epithet "virtuous", when applied to an act of personal environmental responsibility, may be used only ironically. Tell me: how did it come to pass that virtue - a quality that for most of history has generally been deemed, well, a virtue - became a mark of liberal softheadedness? How peculiar, that doing the right thing by the environment - buying the hybrid, eating like a locavore - should now set you up for ridicule.

And even if in the face of this derision I decide I am going to bother, there arises the whole vexed question of getting it right. Is eating local or walking to work really going to reduce my carbon footprint? According to one analysis, if walking to work increases your appetite and you consume more meat or milk as a result, walking might actually emit more carbon than driving. A handful of studies have recently suggested that in certain cases under certain conditions, produce from places as far away as New Zealand might account for less carbon than comparable domestic products. True, at least one of these studies was co-written by a representative of agribusiness interests in (surprise!) New Zealand, but even so, they make you wonder. If determining the carbon footprint of food is really this complicated, and I've got to consider not only "food miles" but also whether the food came by ship or truck and how lushly the grass grows in New Zealand, then maybe on second thoughts I'll just buy the imported chops, at least until the experts get their footprints sorted out.

There are so many stories we can tell ourselves to justify doing nothing, but perhaps the most insidious is that, whatever we do manage to do, it will be too little too late. Climate change is upon us, and it has arrived well ahead of schedule. Scientists' projections that seemed dire a decade ago turn out to have been unduly optimistic: the warming and the melting is occurring much faster than the models predicted. Now truly terrifying feedback loops threaten to boost the rate of change exponentially, as the shift from white ice to blue water in the Arctic absorbs more sunlight and warming soils everywhere become more biologically active, causing them to release their vast stores of carbon into the air. Have you looked into the eyes of a climate scientist recently? They look really scared.

So do you still want to talk about planting gardens? I do.

Whatever we can do as individuals to change the way we live at this suddenly very late date does seem utterly inadequate to the challenge. It's hard to argue with Michael Specter, in a recent New Yorker piece on carbon footprints, when he says: "Personal choices, no matter how virtuous [NB!], cannot do enough. It will also take laws and money." So it will. Yet it is no less accurate or hardheaded to say that laws and money cannot do enough, either; that it will also take profound changes in the way we live. Why? Because the climate-change crisis is at its very bottom a crisis of lifestyle - of character, even. The Big Problem is nothing more or less than the sum total of countless little everyday choices, most of them made by us (consumer spending represents 70% of our economy), and most of the rest of them made in the name of our needs and desires and preferences.

For us to wait for legislation or technology to solve the problem of how we're living our lives suggests we're not really serious about changing - something our politicians cannot fail to notice. They will not move until we do. Indeed, to look to leaders and experts, to laws and money and grand schemes, to save us from our predicament represents precisely the sort of thinking - passive, delegated, dependent for solutions on specialists - that helped get us into this mess in the first place. It's hard to believe that the same sort of thinking could now get us out of it.

Thirty years ago, Wendell Berry, the farmer and writer, put forward a blunt analysis of precisely this mentality. He argued that the environmental crisis of the 70s - an era innocent of climate change; what we would give to have back that environmental crisis! - was at its heart a crisis of character and would have to be addressed first at that level: at home, as it were. He was impatient with people who wrote cheques to environmental organisations while thoughtlessly squandering fossil fuel in their everyday lives - the 70s equivalent of people buying carbon offsets to atone for their SUVs. Nothing was likely to change until we healed the "split between what we think and what we do". For Berry, the "Why bother?" question came down to a moral imperative: "Once our personal connection to what is wrong becomes clear, then we have to choose: we can go on as before, recognising our dishonesty and living with it the best we can, or we can begin the effort to change the way we think and live."

For Berry, the deep problem standing behind all the other problems of industrial civilisation is "specialisation", which he regards as the "disease of the modern character". Our society assigns us a tiny number of roles: we're producers (of one thing) at work, consumers of a great many other things the rest of the time, and then once a year or so we vote as citizens. Virtually all of our needs and desires we delegate to specialists of one kind or another - our meals to agribusiness, health to the doctor, education to the teacher, entertainment to the media, care for the environment to the environmentalist, political action to the politician.

As Adam Smith and many others have pointed out, this division of labour has given us many of the blessings of civilisation. Specialisation is what allows me to sit at a computer thinking about climate change. Yet this same division of labour obscures the lines of connection - and responsibility - linking our everyday acts to their real-world consequences, making it easy for me to overlook the coal-fired power plant that is lighting my screen, or the mountaintop in Kentucky that had to be destroyed to provide the coal to that plant, or the streams running crimson with heavy metals as a result.

Of course, what made this sort of specialisation possible in the first place was cheap energy. Cheap fossil fuel allows us to pay distant others to process our food for us, to entertain us and to (try to) solve our problems, with the result that there is very little we know how to accomplish for ourselves. Think for a moment of all the things you suddenly need to do for yourself when the power goes out - up to and including entertaining yourself. Think, too, about how a power failure causes your neighbours - your community - to suddenly loom so much larger in your life. Cheap energy allowed us to leapfrog community by making it possible to sell our speciality over great distances as well as summon into our lives the specialities of countless distant others.

Here's the point: cheap energy, which gives us climate change, fosters precisely the mentality that makes dealing with climate change in our own lives seem impossibly difficult. Specialists ourselves, we can no longer imagine anyone but an expert, or anything but a new technology or law, solving our problems. Gore asks us to change the lightbulbs because he probably can't imagine us doing anything much more challenging, like, say, growing some portion of our own food. We can't imagine it, either, which is probably why we prefer to cross our fingers and talk about the promise of ethanol and nuclear power - new liquids and electrons to power the same old cars and houses and lives.

The "cheap-energy mind", as Berry called it, is the mind that asks, "Why bother?" because it is helpless to imagine - much less attempt - a different sort of life, one less divided, less reliant. Since the cheap-energy mind translates everything into money - its proxy - it prefers to put its faith in market-based solutions: carbon taxes and pollution-trading schemes. If we could just get the incentives right, it believes, the economy will properly value everything that matters and nudge our self-interest down the proper channels. The best we can hope for is a greener version of the old invisible hand. Visible hands it has no use for.

But while some such grand scheme may well be necessary, it is doubtful that it will be sufficient or that it will be politically sustainable before we have demonstrated to ourselves that change is possible. Merely to give, to spend, even to vote, is not to do, and there is so much that needs to be done - without further delay. In the judgment of James Hansen, the Nasa climate scientist who began sounding the alarm on global warming 20 years ago, we have only 10 years left to start cutting - not just slowing - the amount of carbon we're emitting or face a "different planet". Hansen said this more than two years ago, however; two years have gone by, and nothing of consequence has been done. So: eight years left to go - and a great deal left to do.

Which brings us back to the "Why bother?" question and how we might better answer it. The reasons not to bother are many and compelling, at least to the cheap-energy mind. But let me offer a few admittedly tentative reasons that we might put on the other side of the scale:

If you do bother, you will set an example for other people. If enough other people bother, each one influencing yet another in a chain reaction of behavioural change, markets for all manner of green products and alternative technologies will prosper and expand. (Just look at the market for hybrid cars.) Consciousness will be raised, perhaps even changed: new moral imperatives and new taboos might take root in the culture. Driving an SUV or eating a 24oz steak or illuminating your house like an airport runway at night might come to be regarded as outrages to human conscience. Not having things might become cooler than having them. And those who did change the way they live would acquire the moral standing to demand changes in behaviour from others - from other people, other corporations, even other countries.

All of this could, theoretically, happen. What I'm describing (imagining would probably be more accurate) is a process of viral social change, and change of this kind, which is nonlinear, is never something anyone can plan or predict or count on. Who knows, maybe the virus will reach all the way to Chongqing and infect my Chinese evil twin. Or not. Maybe going green will prove a passing fad and will lose steam after a few years, just as it did in the 80s, when Ronald Reagan took down Jimmy Carter's solar panels from the roof of the White House.

Going personally green is a bet, nothing more or less, though it's one we probably all should make, even if the odds of it paying off aren't great. Sometimes you have to act as if acting will make a difference, even when you can't prove that it will. That, after all, was precisely what happened in Communist Czechoslovakia and Poland, when a handful of individuals such as Václav Havel and Adam Michnik resolved that they would simply conduct their lives "as if" they lived in a free society. That improbable bet created a tiny space of liberty that, in time, expanded to take in, and then help take down, the whole of the eastern bloc.

So what would be a comparable bet that the individual might make in the case of the environmental crisis? Havel himself has suggested that people begin to "conduct themselves as if they were to live on this earth for ever and be answerable for its condition one day". Fair enough, but let me propose a slightly less abstract and daunting wager. The idea is to find one thing to do in your life that doesn't involve spending or voting, that may or may not virally rock the world but is real and particular (as well as symbolic) and that, come what may, will offer its own rewards. Maybe you decide to give up meat, an act that would reduce your carbon footprint by as much as a quarter. Or you could try this: determine to observe the Sabbath. For one day a week, abstain completely from economic activity: no shopping, no driving, no electronics.

But the act I want to talk about is growing some - even just a little - of your own food. Rip out your lawn, if you have one, and if you don't - if you live in a high-rise, or have a garden shrouded in shade - look into getting an allotment. Measured against the Problem We Face, planting a garden sounds pretty benign, I know, but in fact it's one of the most powerful things an individual can do - to reduce your carbon footprint, sure, but more important, to reduce your sense of dependence and dividedness: to change the cheap-energy mind.

A great many things happen when you plant a vegetable garden, some of them directly related to climate change, others indirect but related nevertheless. Growing food, we forget, comprises the original solar technology: calories produced by means of photosynthesis. Years ago the cheap-energy mind discovered that more food could be produced with less effort by replacing sunlight with fossil-fuel fertilisers and pesticides, with a result that the typical calorie of food energy in your diet now requires about 10 calories of fossil-fuel energy to produce. It's estimated that the way we feed ourselves (or rather, allow ourselves to be fed) accounts for about a fifth of the greenhouse gas for which each of us is responsible.

Yet the sun still shines down on your garden, and photosynthesis still works so abundantly that in a thoughtfully organised vegetable patch (one planted from seed, nourished by compost from the kitchen and involving not too many drives to the garden centre), you can grow the proverbial free lunch - CO2-free and money-free. This is the most-local food you can possibly eat (not to mention the freshest, tastiest and most nutritious), with a carbon footprint so faint that even the New Zealand lamb council dares not challenge it. And while we're counting carbon, consider too your compost pile, which shrinks the heap of garbage your household needs trucked away even as it feeds your vegetables and sequesters carbon in your soil. What else? Well, you will probably notice that you're getting a pretty good workout there in your garden, burning calories without having to get into the car to drive to the gym. (It is one of the absurdities of the modern division of labour that, having replaced physical labour with fossil fuel, we now have to burn even more fossil fuel to keep our unemployed bodies in shape.) Also, by engaging both body and mind, time spent in the garden is time (and energy) subtracted from electronic forms of entertainment.

You begin to see that growing even a little of your own food is, as Berry pointed out 30 years ago, one of those solutions that, instead of begetting a new set of problems - the way "solutions" such as ethanol or nuclear power inevitably do - actually beget other solutions, and not only of the kind that save carbon. Still more valuable are the habits of mind that growing a little of your own food can yield. You quickly learn that you need not be dependent on specialists to provide for yourself - that your body is still good for something and may actually be enlisted in its own support. If the experts are right, if both oil and time are running out, these are skills and habits of mind we're all very soon going to need. We may also need the food. Could gardens provide it? Well, during the second world war victory gardens supplied as much as 40% of the produce Americans ate.

But there are sweeter reasons to plant that garden, to bother. At least in this one corner of your yard and life, you will have begun to heal the split between what you think and what you do, to commingle your identities as consumer and producer and citizen. Chances are, your garden will re-engage you with your neighbours, for you will have produce to give away and the need to borrow their tools. You will have reduced the power of the cheap-energy mind by personally overcoming its most debilitating weakness: its helplessness and the fact that it can't do much of anything that doesn't involve division or subtraction. The garden's season-long transit from seed to ripe fruit - will you get a load of those courgettes! - suggests that the operations of addition and multiplication still obtain, that the abundance of nature is not exhausted. The single greatest lesson the garden teaches is that our relationship to the planet need not be zero-sum, and that as long as the sun still shines and people still can plan and plant, think and do, we can, if we bother to try, find ways to provide for ourselves without diminishing the world.

· Michael Pollan is the author of In Defence of Food: An Eater's Manifesto.