Today is a bleak day for the environment, the day of the year when mankind over-exploits the world's resources - the day when we start living beyond our ecological means.
Evidence is mounting that rapid population growth and rising living standards among the Earth's six billion inhabitants are putting an intolerable strain on nature. For the first time an organisation a British think-tank has sought to pinpoint how quickly man is using the global resources of farming land, forests, fish, air and energy.
The new economics foundation has calculated from research by a US academic group, Global Footprint Network, that the day when we use more than our fair share of the Earth when "humanity starts eating the planet" is October 9.
In other words, assuming that the world has a certain quantity of natural resources that can sustainably be used up each year, today is the date at which this annual capacity is reached. And environmentalists warn that just as a company bound for bankruptcy plunging into the red or a borrower " maxing out" on credit cards must face the consequences, so must man.
The biggest problem relating to the over-consumption of resources is climate change, but its other effects include deforestation, falling agricultural yields and overfishing.
Overfishing is one of the most easily understood examples of the abuse of nature. Catching too many fish has left species that were once common, such as cod in the North Sea and bluefin tuna in the Mediterranean, struggling to survive.
Although it is possible to make ever-increasing catches for a while, eventually only small, juvenile fish are left, and stocks become unviable. Similarly, emissions of greenhouse gases are rising, exacerbated by the growth of China and India, but the climate is poised to wreak its revenge. Already polar ice caps are melting at a rate that is startling scientists, and examples of extreme weather, such as Hurricane Katrina, which devastated New Orleans in August last year, are being attributed to global climate change. In February, when he was Defence Secretary, John Reid revealed that British military planners were already preparing for conflicts arising from the scramble for resources in 20 to 30 years' time.
Outlining the impact of global warming, he said: "Impacts such as flooding, melting permafrost and desertification could lead to loss of agricultural land, poisoning of water supplies and destruction of economic infrastructure."
Global Footprint estimates that the human race is over-using the Earth's resources by 23 per cent. While each individual should use up no more than the equivalent of 1.8 hectares of the Earth's surface, the actual area we use is 2.2 hectares per person.
Mathis Wackernagel, executive director of Global Footprint Network, which analyses 6,000 pieces of data from such sources as the United Nations, warned that the limit of the Earth's endurance had already been reached.
He said: "Humanity is living off its ecological credit card and can only do this by liquidating the planet's natural resources."
According to nef's analysis, the unsustainability of human behaviour has speeded up markedly. Humanity started living beyond its means on a global level in 1987, when the limit of sustainability was reached on 19 December. By 1995, the day was arriving by 21 November and began arriving in October shortly after the millennium.
Consumption is particularly profligate in the West, where individuals consume air-freighted food, buy hardwood furniture, enjoy foreign holidays and own cars. Global Footprint estimates the world would need five planet Earths to sustain a global materialistic society such as that in the US while almost three would be needed for the UK.
By contrast, developing countries such as Kenya use a fraction of the resources. Nef highlighted the energy wasted in trade. In 2004, for example, Britain exported 1,500 tons of potatoes to Germany and imported the same amount. We sent 10,200 tons of milk and cream to France and imported 9,900 tons.
Andrew Simms, policy director of nef, warned the world was living far beyond our environmental means.
Professor Tim Jackson, head of sustainable development at Surrey University, one of Britain's leading experts in sustainability, said the research was broadly right and that we are using resources faster than they can be replaced by the planet.
He said: "We are clearly drawing natural capital and the point about collapse is that we don't know when some of the systems in the global atmosphere and fish will collapse but we do know that collapse is a very real possibility."
Our dwindling natural assets
Degradation of the marine ecosystem is one of the world's biggest problems after climate change. Many fish population have shrunk by 90 per cent in 50 years. Species in particular danger are bluefin tuna in the Mediterranean and Atlantic and cod in the North Sea.
Oil reserves are fast running out: "peak oil" - the point from which oil reserves start to decline - is imminent, with world consumption of oil at 84 million barrels a day. In turn, the burning of fossil fuels is the largest source of emissions of CO2.
Some 13 million hectares of forest are lost every year, says the UN Food and Agriculture Organisation. Almost 20 per cent of The Amazon - the world's "lung" - has been felled. In 2004 the rate of forest clearance in the Amazon was the second highest on record, caused by the boom in growing soya beans. Deforestation of tropical rainforests may account for the loss of as many as 100 species a day.
Population growth, pollution and climate change are making water a scarce resource. Only 2 per cent of water on Earth is fresh, the rest is salt or trapped in glaciers and snow. By 2050, 7 billion people in 60 countries could be short of drinking water.
Overfarming drains the soil of nutrients, while the chemicals used in the process pollute waterways. Farming uses 70 per cent of the world's water supply: to provide 2,700 calories a day requires 4,300 litres (more than seven bathtubs) of water.