Jim Lovelock, environmentalist, scientist, and celebrated proposer of the Gaia hypothesis, has always taken the long view of Earth's future. So it feels appropriate that he should have retired to a coastguard's cottage perched above Chesil Beach on Dorset's Jurassic Coast – so called because 180 million years of geological history lie exposed along its cliffs and coves.

This shoreline is constantly eroding. In the winter storms of 2013, Lovelock's cottage was cut off for four days when the road leading to it was washed into the sea – not that Lovelock, whose latest book is entitled A Rough Ride to the Future, needed any reminder of the precariousness of our world. A decade ago, he predicted that billions would be wiped out by floods, drought and famine by 2040. He is more circumspect about that date these days, but he has not changed his underlying belief that the consequences of global warming will catch up with us eventually. His conviction that humans are incapable of reversing them – and that it is in any case too late to try – is also unaltered. In the week when the Grantham Research Institute on Climate Change reported that the world is still miles off meeting its 2030 carbon emission targets, Lovelock cannot easily be dismissed.

There are other doomsayers. What makes this one so unusual is his confounding cheerfulness about the approaching apocalypse. His optimism rests on his faith in Gaia – his revolutionary theory, first formulated in the 1970s, that our planet is not just a rock but a complex, self-regulating organism geared to the long-term sustenance of life. This means, among other things, that if there are too many people for the Earth to support, Gaia – Earth – will find a way to get rid of the excess, and carry on.

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Lovelock's concern is less with the survival of humanity than with the continuation of life itself. Against that imperative, the decimation of nations is almost inconsequential to him. "You know, I look with a great deal of equanimity on some sort of happening – not too rapid – that reduces our population down to about a billion," he says, five minutes into our meeting. "I think the Earth would be happier ... A population in England of five or 10 million? Yes, I think that sounds about right." To him, even the prospect of nuclear holocaust has its upside. "The civilisations of the northern hemisphere would be utterly destroyed, no doubt about it," he says, "but it would give life elsewhere a chance to recover. I think actually that Gaia might heave a sigh of relief."

He is driven, at least in part, by a deep affinity for the English countryside. When he warns that sea levels are rising three times faster than the first climatology models predicted, and that this threatens "an awful lot of land north of Cambridge that is one or two meters below sea level", you sense that he really cares about that landscape's fate. No doubt he inherited this affection, along perhaps with a certain independence of spirit and thought, from his father. Born in West Berkshire in 1872, Lovelock senior grew up as a "hunter-gatherer" in support of his impoverished family, until, aged 14, he was caught poaching and imprisoned in Reading for six months. "I am very proud of that first part of my father's life," he says.

Like others of his generation, Lovelock mourns the changes to the countryside wrought by the post-War agricultural revolution. As a young man in the 1930s, he recalls, he cycled from Kent to the West Country, when England was "unbelievably beautiful". "It all looks very green and pleasant around here," he adds, waving at the gentle downland beyond his kitchen window, "but it's nothing compared to what it used to be".

Like Gaia, he has evidently developed certain stratagems for the sustenance of life. One would not guess from his appearance that he will be 96 this year. With his American wife Sandy, who is 20 years his junior, he still walks to the village shops each Saturday, a round-trip of six miles; and his intellectual vigour is so unimpaired that conversing with him soon makes the head spin.

Japan Earthquake and tsunami 2011
While the 2011 Japan earthquake caused devastation, Lovelock observes that "zero" have died of radiation from Fukushima

He contends that the end of the world as we know it began in 1712, the year the Devonshire blacksmith Thomas Newcomen invented the coal-powered steam engine. It was the first time that stored solar energy had been harnessed in any serious way, with effects that now "grip us and our world in a series of unstoppable events. We are like the sorcerer's apprentice, trapped in the consequences of our meddling". Newcomen's discovery set in train more than just the era of industrial development. It also marked the start of a new geological epoch, the "Anthropocene", the most significant characteristic of which, Lovelock believes, has been the emergence of "an entirely new form of evolution" that is one million times faster than the old process of Darwinian natural selection.

He points out that for half a century now, computing power has roughly doubled every two years – a trajectory of growth known as Moore's Law – and that computers are already capable of many actions far beyond what humans can do. In his scariest scenario, which sounds disturbingly close to the premise of the Arnie Schwarzenegger Terminator movies, he warns that computers could morph into an autarkic life form powerful enough to "destroy us, our carbon life forms, and inherit the Earth". Luckily he thinks this outcome unlikely, and in the end has no fear of the Rise of the Machines. "Computers are entirely rational creations. But true intelligence, the ability to create and to invent, is intuitive – and you can't do rational intuition."

On the other hand, his preferred prediction for humanity is scarcely less disturbing. He foresees the evolution of a man-machine hybrid by a process of endosymbiosis that, he argues, has already begun. "I am already endosymbiotic. I'm fitted with a pacemaker. It runs on a 10-year lithium battery, but the next generation will have its own power supply drawn from the body. I'm already worried about being hacked ... Fairly soon, I think, the internet is going to be fully embedded in our bodies."

Looking further still into the future, he says that life on Earth, based as it presently is on carbon, cannot last beyond 100 million years, because by then it will be too hot. The evolution of a different life form based on some more heat-resistant element – such as electronic silicon – could potentially extend life by another 500 million or even a billion years.

But first, of course, mankind has to survive the immediate global warming crisis. Lovelock is a famously outspoken critic of the green energy revolution, especially wind power, which he describes as "an absolute scam. A great big German scam". The purveyors of wind turbines and solar panels, he says, are like 18th-century doctors trying to cure serious diseases with leeches and mercury. Instead he wants us to embrace nuclear fission, a completely clean energy source that he regards as a "gift". The Western world's prejudice against nuclear – underscored earlier this year when the number of reactors in the US dipped below a hundred for the first time in decades – is "tragic".

German windmills, Dessau
Lovelock says wind power is a "great big German scam"

"What gets my goat are the lies peddled about Fukushima [the Japanese nuclear reactor disaster of 2011]. Do you know how many people died of radiation? Zero. Not one – although there were 50-odd suicides among people driven to it by fear. Nuclear energy is actually 10 times safer, per GigaWatt hour of production, than wind power. Yet France and Germany responded to Fukushima by temporarily shutting down their entire nuclear industries. It makes no sense." The reason, he thinks, is public ignorance, combined with a form of green politics that amounts to a "new religion – the same force that drives jihadists in Syria". It is, he agrees, a paradox that the new accessibility of information brought about by the internet revolution has intensified, not diminished, the old battle between science and superstition. "There's a campaign in our village to stop a new mobile phone mast. The electromagnetic radiation it will emit is trivial. It's comparable to a household television. Yet the campaigners say it can give you cancer. This is about fear – not facts."

With one or two exceptions such as Margaret Thatcher and Germany's Angela Merkel, both of whom studied chemistry, he thinks our leaders are just as bad. "If you talk to any politician, American or British or European, they are absolutely blind on matters of science," he says. He reserves special ire for Tony Blair, "the really mad prime minister" who, swayed by green ideology and the Campaign for Nuclear Disarmament, passed legislation subsidising the renewable energy sector, which made fresh investment in the nuclear industry almost impossible. (This, he argues, is one reason why the heating costs of an average house in the UK are up to 10 times greater than in America, which, overall, has a colder climate. For many years, he asserts, the Lovelocks wintered in St Louis, Missouri, purely in order to avoid British heating bills.)

But even a wholesale switch to nuclear power, in his view, would come too late to solve humanity's principal problem, which is overpopulation. The old post-war goal of sustainable development, he says, has become an oxymoron and should be abandoned in favour of a strategy of sustainable retreat. He is scathing about the very idea of "saving the planet", which he calls "the foolish extravagance of romantic Northern ideologues". The vast sums of money being invested in renewable energy would be much better spent on strategies designed to help us survive and adapt, such as flood defences.

Above all, he thinks that we should embrace the ongoing global shift towards urban living. It would, he insists, be far easier and more economic to regulate the climate of cities than our current strategy of attempting to control the temperature of an entire planet. The regions beyond the cities would then be left to Gaia to regulate for herself. It seems a sci-fi fantasy, rather like Mega-City One from the pages of Judge Dredd, a post-apocalypse megalopolis shielded from the "Cursed Earth" beyond by massive boundary walls. But, in fact, the concept is not so futuristic. Noah, arguably, had a similar idea when he built the ark.

It is certainly not a new concept to Lovelock, who wrote a paper for the oil multinational, Shell, as far back as 1966 in which he predicted that the cities of the future would become much denser, and that Shell would be making plenty of money out of "the avoidance of ecological disaster". The fictional Mega-City One held 800 million citizens, and incorporated the entire eastern seaboard of the United States. Lovelock points that the average population density of England is higher than that of greater Boston. His 1966 paper, which was recently reprinted by Shell, no longer looks as fantastical as it once did.

Singapore, he suggests, shows us how a city can succeed in an overheated climate. The trend there for building underground, as well as in places like Japan and even London (albeit for different reasons), might be part of the same process of adaptation. Architectural practices from the past might also offer clues to a sustainable retreat in the future. The streets of the medieval Dalmatian island town of Korcula, for instance, follow a unique herringbone plan designed to capture and channel the prevailing, cooling sea breeze.

Nature offers models for future city architecture, too. Lovelock is much taken at the moment with termites. Their mounds, he says, are built like the cities of the future might be. Like Korcula, they are oriented towards the prevailing wind. They also tend to lean towards the zenith of the sun, to minimise exposure to its rays at the hottest time of the day – a stratagem that perhaps has its analogue in a recent suggestion by the Scottish nationalist politician Rob Gibson, who wants all new housing estates to be orientated towards the south in order to maximise the efficiency of rooftop solar panels.

(In London, meanwhile, the architects NBBJ recently proposed building the world's first "shadowless skyscraper" by building two towers – one to block out the sun, the other to reflect light down into the shadow of the first).

More interesting still, a recent paper in Science magazine has shown that termite mounds, once thought to be a sign of encroaching desertification, may actually have the ability to stabilise or even reverse the effects of climate change by trapping rainfall. "Termites are very Gaian," Lovelock enthuses. "There are these wonderful pictures of little plants growing up between the termite cities. You could look at that as a nice future for humans."

So does Lovelock really think that humanity could end up mimicking social insects? A dumbed-down world inhabited by worker drones might be environmentally efficient, but what about the surrender of privacy that would imply; isn't the sublimation of individuality too high a price to pay? How could such a society ever throw up a Beethoven, a Shakespeare, or an Einstein? "That's true, and of course it depends how far down this track we choose to go," says Lovelock, "but do you think that evolution, as a process, gives two hoots about any of that?"

This is, to be sure, a reductive view of human existence. A man in the twilight of his years, as Lovelock is, might feel a sense of futility. Instead he maintains a steady wonder at what he calls "the ineffable: a lovely word, don't you think?" while apparently seeking no earthly legacy beyond a modest hope that he will be remembered as having been consistent in his arguments.

As a man of science, he remains agnostic on the subject of God. And yet, he says, "I am beginning to swing round, to think more and more, that there's something in Barrow and Tipler's cosmic-anthropic principle – the idea that the universe was set up in such a way that the formation of intelligent life on some planet somewhere was inevitable ... The more you look at the universe, the more puzzling it is that all the figures are just right for the appearance on this planet of people like us."

For the time being our species may be, as he has written, "scared and confused, like a colony of red ants exposed when we lift the garden slab that is the lid of their nest". But he is also content to be one of those ants, because he sees a kind of beauty in that confusion – and perhaps even some sort of grand design. "Humanity may be as important to Earth, to Gaia, as the first photo-synthesisers," he thinks. "We are the first species to harvest information ... that is something very special."

Above all he is convinced that mankind can recover itself – and in this he may be a product of his vanishing generation. Some years ago, at a lecture in Edinburgh, I heard him reminisce how marvellously the British nation had pulled together when threatened by Nazi invasion, but that it had taken that existential threat to make them do so. When the climate crisis finally breaks, he believes, the world's differences will again be put aside – and our species, for all its present idiocies, will pull together in a way that will astonish the cynics among us.