The report, by the United Nations Environment Programme (Unep), warns that the vital natural resources which support life on Earth have suffered significantly since the first such report, published in 1987. However, this gradual depletion of the world's natural "capital" has coincided with unprecedented economic gains for developed nations, which, for many people, have masked the growing crisis.
Nearly 400 experts from around the world contributed to the report, which warns that humanity itself could be at risk if nothing is done to address the three major environmental problems of a growing human population, climate change and the mass extinction of animals and plants.
The report is the fruit of five years' work by leading scientists and is the fourth in a series since the publication in 1987 of Our Common Future by an international commission into the state of the global environment chaired by the former Norwegian prime minister Gro Harlem Brundtland.
Achim Steiner, the executive director of Unep, said that the objective of the latest report was not to present a "dark and gloomy scenario" but to make the case for an urgent call to action. However, the dire state of almost every aspect of the planet's wellbeing points to 20 years of missed opportunities.
Mr Steiner said yesterday at the launch of the report that it was illuminating how over the past 20 years the financial wealth of the planet has soared by around a third. "But at the same time it is sobering: much of the 'natural' capital upon which so much of human well-being and economic activity depends – water, land, the air and atmosphere, biodiversity and marine resources – continue their seemingly inexorable decline," he said.
Meanwhile, the political response to the growing emergency has been limited. "Without an accelerated effort to reform the way we collectively do business on planet Earth, we will shortly be in trouble if indeed we are not already," Mr Steiner said.
"There have been enough wake-up calls. I sincerely hope this is the final one. The systematic destruction of the Earth's natural and nature-based resources has reached a point where the economic viability of economies is being challenged – and the bill we hand on to our children may prove impossible to pay," he said.
The fourth Unep report since the seminal 1987 report of the Brundtland Commission reveals a stark continuation in the environment's decline. The environmental "footprint" of humanity has increased dramatically in 20 years, with a rising population and increased use of energy, land and other natural resources.
Unep's Global Environment Outlook (GEO-4) states that the human demand on the planet now means we are living beyond our means. The present footprint is equivalent to 22 hectares per person, whereas the natural carrying capacity of the Earth is less than 16 hectares per person, the report says.
The world economy has at the same time boomed, with the global GDP per capita rising from about $6,000 (£2,920) to just over $8,000. But this increased wealth has been geared towards the developed world and has come at an enormous cost to the environment. Available freshwater stocks have declined dramatically since the 1980s, in west Asia, for instance, from 1,700 cubic metres per person per year, to 907 cubic metres today. By the middle of the century, this is likely to fall still further to 420 cubic metres per person per year. Over the past 20 years, the proportion of fish stocks in the world that have collapsed has doubled from 15 per cent to 30 per cent. At the same time the proportion of fish stocks that are deemed to be overexploited has risen from 20 per cent to 40 per cent.
The intensity with which agricultural land is farmed has also increased, and with it the burden of soil erosion, water scarcity, nutrient depletion and pollution. In 1987, a hectare of cropland yielded 1.8 tons of produce, but due to intensification this has now risen to 2.5 tons.
Energy consumption in developed nations has risen significantly. In Canada and the US, for instance, the demand for energy has grown by 19 per cent since 1987. Concentrations of carbon dioxide, a principal greenhouse gas, are about a third higher than they were 20 years ago.
Species of animals and plants are estimated to be going extinct at a rate that is about 100 times faster than the historical record, largely as a result of human activities. Biologists have now classified 30 per cent of amphibians, 23 per cent of mammals and 12 per cent of birds as threatened.
A growing human population, which is expected to reach nine billion by the mid-century, will place increasing pressure on land, water and biodiversity. Land will have to be more intensively farmed, or more land will have be cultivated. "Either way, biodiversity suffers," the report says.
Against a background of continued degradation of the land and oceans, of population increases and of species extinctions, lies the spectre of climate change – one the biggest threats facing humanity in the 21st century. There is now "visible and unequivocal" evidence that global warming is causing further impacts on the global environment, the GEO-4 report says.
Mike Childs, the campaigns director at Friends of the Earth, said the report made it clear we need concerted international political action to reduce greenhouse gas emissions and halt the loss of wildlife and ecosystems. "This report clearly demonstrates that we also need a step change in understanding that the steady degradation of the world's environment threatens the well-being of everybody on the planet," he said.
"Our response to this planetary emergency must be to harness humankind's amazing ingenuity to make the next two decades a time of innovation and determination to create a fairer and greener world."
Twenty years of environmental failure
Since 1987, when the landmark UN report Our Common Future (overseen by Gro Harlem Brundtland, right) warned of the need for concerted action to secure humanity's future, the state of the global environment has declined in numerous ways.
* The availability of fresh water had declined dramatically. In west Asia, for instance, available fresh water has fallen from 1,700 cubic metres per person per year to 907 cubic metres, largely due to pollution and demand.
* Levels of carbon dioxide have risen by a third and energy demands of countries such as the United States and Canada are nearly a fifth higher than in 1987.
* In 1987, about 15 per cent of global fish stocks were classified as collapsed, and 20 per cent were overexploited. Now 30 per cent have collapsed and a further 40 per cent are overexploited.
* The number of species which is threatened with extinction has increased. Since 1987, there has been a 50 per cent decline in the populations of some freshwater animals and a 30 per cent fall among terrestrial and marine species.
* The agricultural intensification of cultivated land has risen, with greater impact on pollution, nutrient depletion and water use. A hectare of farmland in 1987 produced an average yield of 1.8 tons, but now it produces 2.5 tons.
* Human population has increased by a third since 1987. At the same time there has been a threefold increase in global trade and average income per head has increased by a third, with global GDP per capita rising from $6,000 in 1987 to a total of $8,000 today.
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