Reckless consumption comes at a high cost, the report warns
The planet is headed for an ecological "credit crunch", according to a report issued by conservation groups.
The document contends that our demands on natural resources overreach what the Earth can sustain by almost a third.
The Living Planet Report is the work of WWF, the Zoological Society of London and the Global Footprint Network.
It says that more than three quarters of the world's population lives in countries where consumption levels are outstripping environmental renewal.
This makes them "ecological debtors", meaning that they are drawing - and often overdrawing - on the agricultural land, forests, seas and resources of other countries to sustain them.
WWF's David Norman says the world will need two planets by 2030
The report concludes that the reckless consumption of "natural capital" is endangering the world's future prosperity, with clear economic impacts including high costs for food, water and energy.
Dr Dan Barlow, head of policy at the conservation group's Scotland arm, added: "While the media headlines continue to be dominated by the economic turmoil, the world is hurtling further into an ecological credit crunch."
The countries with the biggest impact on the planet are the US and China, together accounting for some 40% of the global footprint.
The report shows the US and United Arab Emirates have the largest ecological footprint per person, while Malawi and Afghanistan have the smallest.
The map shows hectares' worth consumed in goods and services
"If our demands on the planet continue to increase at the same rate, by the mid-2030s we would need the equivalent of two planets to maintain our lifestyles," said WWF International director-general James Leape.
In the UK, the "ecological footprint" - the amount of the Earth's land and sea needed to provide the resources we use and absorb our waste - is 5.3 hectares per person.
This is more than twice the 2.1 hectares per person actually available for the global population.
The UK's national ecological footprint is the 15th biggest in the world, and is the same size as that of 33 African countries put together, WWF said.
"The events in the last few months have served to show us how it's foolish in the extreme to live beyond our means," said WWF's international president, Chief Emeka Anyaoku.
"Devastating though the financial credit crunch has been, it's nothing as compared to the ecological recession that we are facing."
He said the more than $2 trillion (£1.2 trillion) lost on stocks and shares was dwarfed by the up to $4.5 trillion worth of resources destroyed forever each year.
The index tracks population trends in 1,161 populations of 355 mammal species
It shows an average 19% decrease, with the most serious declines in the tropics
The report's Living Planet Index, which is an attempt to measure the health of worldwide biodiversity, showed an average decline of about 30% from 1970 to 2005 in 3,309 populations of 1,235 species.
An index for the tropics shows an average 51% decline over the same period in 1,333 populations of 585 species.
A new index for water consumption showed that for countries such as the UK, the average "water footprint" was far greater than people realised, with thousands of litres used to produce goods such as beef, sugar and cotton shirts.
"In Britain, almost two thirds [62%] of the average water footprint comes from use abroad to produce goods we consume," said Mr Leape.
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