The planet's 6.8 billion people were living 50% beyond Earth's sustainable means in 2007, the latest year for which figures are available, according to the biannual "Living Planet" report by WWF.
"Even with modest U.N. projections for population growth, consumption and climate change, by 2030 humanity will need the capacity of two Earths to absorb CO2 waste and keep up with natural resource consumption," the report says, adding that four and a half planets would be needed if everyone used as many resources as the average American.
Its index of biodiversity health showed a loss of almost 30% worldwide and an even loss of 60% in the tropics between 1970 and 2007.
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