Mother Nature is a forgiving sort of landlady, which is just as well for us - her vandalistic, irresponsible, stubborn, short-sighted and terminally foolish tenants.

She supplies us with a terrific place to live and we repay her by skipping the rent, evading our responsibilities, leaving the place like a tip and behaving thoughtlessly towards the neighbours.

Prof Norman MyersThe coffers of human knowledge are bulging, yet the sum total of our applied wisdom, environmentally speaking, could be written on the back of a fag packet.

And what makes matters worse is that human beings are not stupid in these matters - just perverse, when it comes to taking care of the world we live in.

Indeed, Prof Norman Myers believes that one of the leading authors of our environmental and ecological chain letter of misery and destruction is what he terms a policy of "perverse subsidies".

Prof Myers is an Honorary Visiting Fellow of Green College, who says he "specialises in being a generalist".

Thus, his areas of professional and personal concern include the environment, agriculture, world poverty, population and the needs of future generations.

It's a big field, but then the issues don't come any bigger than this.

"What we are doing, in effect, is conducting a planet experiment - we chop down forests, extend deserts, get rid of topsoil, make water supplies ineffective, deplete the ozone layer, dislocate climate patterns and most importantly, we eliminate species in large numbers," Prof Myers explains.

"We're poking around with a huge stick without any regard to the consequences - and if a group of scientists had come along and suggested that we do all this, they'd have been regarded as either crackpots or criminals."

Like everything else, it all comes down to money, sooner rather than later.

But, as the professor points out, it doesn't have to be like this.

"Some say that environmental and ecological damage is a shame, but that we must retain strong economies. Well, it doesn't work like that, in fact. Because what is good for the environment is good for the economy.

"Take fishing - most of the fishing grounds have been over-exposed to the brink of extinction, cod being a notable example. But each year it costs $100bn to land 90 million fish, which are then sold for $80bn - with the gap being made up by Government subsidies. And still we think we can plunder the oceans with impunity, when the economy of places like New England in America has already collapsed because of this way of doing things. We need to back off for a few years instead.

" In Germany, the coal mines are so heavily subsidised that the Government there could send the miners home on full pay for the rest of their lives and still the economy would come out ahead - and there'd be no more acid rain or smog," he insists.

"These are perverse subsidies. Now some may talk about what the cost would be in human terms if these subsidies were removed, but I was brought up on a small sheep farm in the Pennines which had been in my family for 200 years.

"We had to sell it and move to the city in 1945. Then, ten per cent of the population worked in farming in this country, now it's 1.5 per cent.

"Whatever social disruption is caused, the money saved can be used to retrain people.

"As an environmental scientist and activist, I believe that people aren't stupid or myopic or selfish but there's enormous political leverage being brought to bear in places like Germany, with its vote-sensitive mining communities.

"The burning of fossil fuels damages the ozone layer. Every time I drive my car or make a cup of coffee, I'm contributing to this."

Norman Myers talks the talk, but he also walks the walk: "I'm aware that preaching to people just turns them off, so I refuse to drive more than 5,000 miles a year in my car.

"I have a new flat in Headington which will have solar panels, triple glazing and as much insulation as I can get in it.

"There will also be light switches which turn themselves off when there's no movement in the room and when I go shopping, I try to buy things which are ecologically sound."

At 66, the professor is a veteran of some 29 marathons and ran his last one in the highly respectable time of three hours and 42 minutes, leaving many younger runners slogging away in his wake.

He's the father of two grown-up daughters, has academic connections to both Cornell and Stanford universities and is a member of the US National Academy of Sciences.

Faced with the problems of the environment, some will shrug and turn away, believing that, for us, payback time will never come.

"Within two decades, the adverse effects of global warming will undermine the quality of life," says the professor.

"People who went to work in Oxford this morning passed through an atmosphere that has changed more recently than it has done in tens of thousands of years and if we allow it to continue, there will be mass extinction of species.

"We're losing about five species of plants every day - plants that may well contain anti-cancer properties.

"One in four pills on a chemist's shelves derived from wild plants.

"The dinosaurs were here for 140 million years and man has been here for just 250,000 years. And we have not been good tenants."

But, the professor points out, there is still hope among the profligate madness. "There's still time for us to do more to redress the balance," he says.

"I think that this is a great time to be a scientist. But we need to get rid of the political road blocks that perverse subsidies represent.

"In New Zealand, for instance, there are 3.5 million people and 65 million sheep but when the Government there phased out sheep-farming subsidies, the farmers became more efficient.

"It costs each taxpayer in this country £1,500 a year to fund these sort of subsidies and a further £600 to repair the environmental damage caused by them."

Mother Nature is a forgiving landlady, but her patience is finite. In the end, we'll evict ourselves from the planet.

For if we and the governments we elect continue to ignore the message of Norman Myers and others like him, and behave towards the environment like there's no tomorrow, well, the equation is simple.

One day soon, tomorrow won't be . . .