In September 1989, Guardian editor Peter Preston took me to one side. “Environment? Your idea. You do it,” he said. I was on the arts desk and had quite forgotten that, two years earlier, I had proposed that we cover this fast-emerging issue in more depth and with new pages.

We had a great correspondent in Paul Brown, but no single journalist could keep up with events. This was the height of Thatcherism, the old Soviet Union was collapsing in ecological ruin, and there had been serious nuclear accidents at Three Mile Island and Chernobyl. That year, more than two million people in Britain had voted Green in the European parliament elections.

If that wasn’t enough, the Great Storm had just blown down 15m trees in southern England, the Exxon Valdez had spilt 11m gallons of crude oil off Alaska, and the French government had blown up Greenpeace’s Rainbow Warrior in a New Zealand harbour.

In such tumultuous times, few people paid much attention to Nasa scientist James Hansen when he warned the US Congress, in that same year, about the consequences of something called global warming. Instead, the debate was about nuclear power, population, EU butter mountains, the limits to growth, lead in petrol and the car economy.

I suggested to Preston that I was ill-equipped to cover this vast, contentious area and was quite happy to continue covering the arts. No chance. “Four pages. Starting in two weeks,” he said.

With hindsight, the Guardian had accurately foreseen a shift of the global, social and scientific tectonic plates, and the arrival of an era of ecological politics. The lids on those boxes that had long separated human rights, science, nature, economics, politics and rich and poor countries had been blown off. The debate was now both global and local, personal and corporate, and it questioned the tarnished dreams of both capitalism and socialism. This was theatre on the world stage.

In those early days, two very different women and two giant corporations came to define the frontlines of the battle for the natural world. Melanie Phillips was a senior Guardian editor and in charge of the new environment section when, around 1990, at the paper’s morning conference meeting, she questioned a major scientific report that suggested that mankind was partly responsible for global warming.

Phillips was adamant that warming was neither happening nor possible, and that this study showed the descent of science from the pursuit of truth into politicised propaganda. Most of the journalists present were surprised at her disavowal of science, but the Guardian’s science editor was called in to offer another view. Phillips left soon after that, and became a leading climate sceptic.

It was an early warning that the “culture wars” , or the polarisation of conservative and liberal values, had begun in earnest. Within a decade, the US neocons had identified environmentalism as the leading intellectual opposition to conservatism, and were trashing climate science, Europe, the precautionary principle and anyone they thought stood for regulation or against the free market.

An emissary of the developing world … Kenyan activist Wangari Maathai, photographed in 2007. Photograph: Martin Godwin/The Guardian

The second woman was Wangari Maathai, a young Kenyan scientist and political dissident who, in the early 1990s, was planting trees with some of Africa’s poorest communities. She came to Britain to talk to activists after being arrested for trying to stop the destruction of Nairobi’s largest park. Within half an hour she had probably changed the agenda for a generation of people who, until then, had barely considered human rights or the poor to be part of the environmental debate.

Maathai was an emissary of the developing world, and spoke in horror about how western consumerism was devastating the world’s remotest areas and poorest people. Those at the top of the pyramid, she said, were being blinded “by the need to acquire, accumulate and over-consume”. I remember her saying: “They do not understand the limits to growth and they do not appreciate that they jeopardise the capacity of future generations to meet their own needs.”

The message she brought was that any debate about the natural world should not just be about science and parts-per-billion of obscure gases, or about genes or kilowatts, but must include developing countries and be rooted in justice, equity and the situation of the least advantaged. She went on to win the Nobel peace prize, and the planting of trees became a worldwide symbol of political hope and community regeneration.

Into this febrile 1990s mix came two giant corporations, both of which epitomised the times and which had both greatly benefitted from the globalisation of trade and the “liberalisation” of poor countries’ economies under the World Bank and the World Trade Organisation (WTO).

Representing the old oil age was Shell. This pillar of the global corporate establishment was, for the first time, being held to account by the likes of Ogoni writer Ken Saro-Wiwa, who objected to the devastating human impact of the pollution it caused in places such as Nigeria; and by a new generation of activists angry about oil’s effect on the global atmosphere. Both paid the price of dissent. Saro-Wiwa and others were judicially murdered by the Nigerian government in 1995, and the activists were increasingly hounded and treated as criminals by the US and British authorities.

I breathed teargas in five countries (Italian is the sweetest, American the worst)

Monsanto was different. Representatives from the old American chemical company, which had a dark history of making Agent Orange and polychlorinated biphenyls (PCBs), came to the Guardian offices in 1997 claiming that Monsanto was the leader of the new “biological” age, having re-invented itself as a global seed company and world saviour. Five directors sat down in new editor Alan Rusbridger’s office, and within minutes were literally thumping the table, saying that we had misunderstood their intention to feed the world with GM food.

But we understood very well at that moment that GM farming was not just about science, genes and the promise of greater yields, but also about the intensification of power, the control of food and the gigantic profits that all large corporations could make at the expense of nature. True to form, the British government sided with Monsanto. Most of the rest of the world said: no, thanks.

By the late 1990s, with the prospect of water wars, climate change and pollution all growing, and the global NGO movement in full cry at nature’s losses, governments responded with a slew of conventions and treaties to protect the natural world. The Montreal Protocol slowed the growth of the hole in the ozone layer; the Convention on Biological Diversity tried to put a lid on the mounting loss of nature; the Earth Summit had introduced the idea of sustainable development; the UN Framework Convention on Climate Change aimed to brake greenhouse gas-emissions.

Fat chance. Most were compromises, signed up to by cynical governments after long and bitter rows between rich and poor. Looking back, they had a common theme: the US, backed by its industries and Britain, invariably bullied the rest of the world into watering down any proposal that appeared to compromise the western way of life.

Vidal with protesters at the Newbury bypass in the mid-1990s.

But the worldwide reaction to continuing ecological devastation was sharp. Large anti-globalisation protests led by the left had flared up as trade unionists, environmentalists, debt campaigners and the public united to march against bodies such as the WTO in Seattle, Genoa, Florence and elsewhere. I breathed teargas in five countries (Italian is the sweetest, American the worst).

Tactics were swapped between US and British activists as people took to trees and tunnels in protest at the trashing of the countryside, the laying of pipelines, the growth of the car economy and the loss of forests to roads. I recall going to the Newbury road protests with an Amazonian chief, and trying to explain that hundreds of young people were living up trees to protect them. “Ah, they are crazy!”, he responded, with a smile.

Ten years later I travelled with ice scientists and Greenpeace to the high Arctic. We reached 82.30 N, just a few hundred miles from the pole, and could have continued north but for a fuel shortage. The vast ice cap that regulates the Earth’s temperature had in 2011 retreated further and faster than anyone could have imagined just 20 years before. Satellite images showed the ice had reduced by nearly 50% compared to just 40 years ago.

Climate science was by now pretty conclusive, with UN assessments increasingly pointing the finger at mankind. All over the Arctic, the Andes, the Himalayas and the world’s high places, the effects of accelerating ice loss and a warming atmosphere were being seen. But even at temperate European latitudes, scientists were finding plants moving north, new insects arriving and previously unseen diseases. Nepalese farmers told how raindrops were getting bigger, and in Malawi and Tanzania they spoke of how the seasons were shifting. Empirical scientific research caught up with their observations.

But the political chaos around climate change was growing, too, reaching a peak in Copenhagen at the UN’s 2009 climate summit. With 186 countries present, the US spying on delegations, and with Obama, Arnold Schwarzenegger and various rock stars in town, a secret agreement forged by the US, Britain and others to stem emissions by stitching up poor countries spectacularly blew up after a leak.

In 27 years, the population rose by 2.25 billion, the equivalent of another China and another India, or 10 more Americas

It was clear that climate-change diplomacy had little to do with climate, and everything to do with global power politics and rich countries trying to prevent developing countries growing too much. The meeting fell apart and the Guardian, which received the leak, was accused of near-treason for siding with the poor.

“You can’t have people going around getting leaked stuff from other powers who are more powerful than Britain, and printing them and not thinking that’s not going to have an appalling effect,” fumed one affronted senior British mandarin, his efforts to pull a fast one on developing countries in vain. To this day, the UK government believes China leaked that document. Wrong. It was the political mice.

Today, 27 years after Peter Preston bolstered the Guardian’s environment coverage, the world has inexorably changed. In this blink of a geological eye, the human population had exploded, adding an extra 2.25 billion people, the equivalent of another China and another India, or 10 more Americas. From being a predominantly rural species, human beings had become urban. Since 1990, the number of mega-cities of more than 10 million people has tripled. By 2030, there will be 10 more.

In those years, humans moved around like never before. In 1990, air passengers flew approximately 1bn miles. Today it is 3.5bn. In 1989, there were nearly 700m vehicles on the world’s roads. Today there are 1.25bn, and air pollution has become a bigger killer than Aids and malaria combined. Vehicle numbers are expected to double again in the next 30 years.

The world, too, is undeniably hotter than it was in 1989. Sixteen of the 17 warmest years on record have been since 2000, and in that time, the Arctic summer ice has dramatically declined while carbon-dioxide levels have increased from 375 to more than 400-parts-per-million.

Most worryingly, in a short quarter century we have been in biological meltdown. Since 1990 we have trashed one tenth of the world’s wilderness areas and lost perhaps 40% of the world’s animals. According to some scientists, one third of the world’s arable land has been lost to soil erosion or pollution in the past 40 years.

There may never have been a time when so much has changed so fast. Virtually all of the planet’s ecosystems have continued to be transformed by human actions; extinction rates of organisms are high and increasing; genetic diversity has declined globally; Europe’s common bird populations have declined by 12% since 1990; tropical forests have been falling at a rate of nearly 1% a year; marine fisheries are collapsing.

We have greatly diminished the world, but there has been a fightback. In the rich north, we undoubtedly protect more land and sea than we did; we recycle more; our water, air and beaches are generally cleaner, and our homes and machines are more energy-efficient. There are signs that we are slowly weaning ourselves off fossil fuels. We waste less, we buy more ethically, and we can measure our impact on the natural world far better.

Vidal examining polluted water in the village of Abia in Uganda in 2007. Photograph: Dan Chung/The Guardian

Across the world, the increase in the rate of population growth, forest loss and greenhouse-gas emissions is slowing; there are hundreds of millions fewer hungry people and more people with access to fresh water and sanitation. We have legal agreements to burn less fossil fuel, to pollute the air less, and to protect more animals. We understand ecological problems better. Many environmental issues fought in 1989 are within sight of being solved. We know what needs to be done.

Above all, there has been an energy revolution. In 1989, coal in Britain was in decline after the miners’ strike and gas was taking over. But renewable energy, apart from hydro-power, was considered eccentric and unlikely to grow. In a remarkably short time, it has become mainstream and popular. Wind power is now part of the land and seascape; on one day last week it supplied more than 10,000MW, or 23% of Britain’s entire electricity demand.

More than 1m homes and businesses generate electricity from solar power, and just one nuclear plant, Sizewell B, was commissioned in 27 years. Government has been blind to the fact that this has been a cultural revolution, too, with the old, centralised power sources now largely unloved and seen as relics. People today aspire to renewable energy, electric cars and passive houses. Battery developments might revolutionise power again in the next 20 years.

There have been other upsides. Britain now leads the world in reducing CO2 emissions, albeit largely by outsourcing its manufacturing and closing its coalfields. Last year, emissions fell to 31% below 1990 levels, with UK coal use down 41% in just three years and at its lowest level of use since the industrial revolution.

Sustainable development may be the stated aim of all countries, but looking ahead, it is impossible to be ecologically or socially optimistic. Earth’s inhabitable spaces have dramatically shrunk, its resources have become scarcer, and the intergenerational injustices are mounting. Nature is resilient, but it is clear that, as the natural world is pushed to its limits, we increase chaos, conflict, natural disaster and tensions.

Vidal visiting the experimental solar thermal power plant on the outskirts of Masdar, UAE, in 2011.

And as the neocons, the rightwingers and Brexiteers achieve power, so the environmental protections so laboriously won by NGOs and social activists in the 1980s and 90s are in real danger of being wiped out.

The next 27 years can only be fraught. Human population will, inevitably, grow by a further 2 billion people by 2050, cities will burgeon and developing countries will be stretched to their limits. If the gaining of universal wealth follows the lines countries have taken these past 27 years, then the early destruction of more vast swathes of the natural world and its inhabitants seems certain.

The great fear is that the transformation to a low-carbon world will take too long, that an addiction to oil and fossil fuels will not stop, and that we will undermine that web of life that sustains us all.

The twin hopes must be that we see the end of the oil age and we stop the loss of wildlife. We can see now from space what we have done to forests, soils, and oceans and fresh water in just a few years. We now know the disastrous health effects of air pollution, and of a warming world. We understand that we can grow more food without polluting water, or resorting to gene manipulation. We have proved we can heal nature.

Above all, countries and people now have options to transform the way we live. In the words of Preston: “Environment? Your idea. You do it.”

• This article was amended on 28 December 2016. Carbon-dioxide levels have increased from 375 to more than 400-parts-per-million, not parts-per-billion as an earlier version said. It was further amended on 2 January to make clear that Melanie Phillips edited the Guardian’s environment section when it was introduced in 1989.

