The natural health of planet Earth has declined by about 30 percent since 1970, according to new calculations from the World Wildlife Fund.
It's an impossible -- and dangerous -- trend, the fund's experts say.
Impossible because at current rates, humanity is using up the planet's resources so fast that by 2050 -- when the human population will have grown by an additional half to 9 billion -- we will need two Earths to meet the demand.
Dangerous because even the most essential resources -- clean water, productive land, timber and fiber products -- will be increasingly scarce, fought over by the more desperate nations, and hoarded by the more fortunate … if habits haven't changed.
"People are turning resources into waste faster than nature can turn waste back into resources," the fund's vice president, Richard Mott, said to ABC News.
"Since the early 1980s, we've been drawing down natural capital faster than it can replenish itself," Mott said. "It now takes nature about one year and three months to replace what we use in a year."
In fact, says the fund's latest biennial "Living Planet Report," many large populations of natural food sources, including many commercial fish stocks and major swaths of the world's lumber and arable land, could simply disappear from the "irreversible damage" current usage would inflict on Earth's life systems.
In only 33 years, from 1970 to 2003, populations of 1,300 different species from fish to mammals, surveyed worldwide by the fund, had dropped by a third, with the extinction rates accelerating everywhere.
"The consequences are predictable and dire," said James Leape, director general of WWF International. "We are in serious ecological overshoot."
In 2003, the fund's experts say, people used 25 percent more resources than Earth could replenish.
"And we're using five times too much fossil fuel, which has thrown the whole Earth dangerously out of balance through global warming," said Princeton atmospheric scientist Michael Oppenheimer in response to the WWF report.
The fund's report says the single fastest growing cause of strain on Earth's resources is the rising average planetary temperature created by the burning of fossil fuels, which releases heat-trapping greenhouse gases.
"We have to cut greenhouse gases by 80 percent, starting now, to bring Earth's system back into balance," Oppenheimer said.
"And we have to rebalance the system," Oppenheimer said, "because if we don't, the climate will grow so hot, so fast that not only the ecosystems but civilization just won't be able to cope -- even within this century."
Oppenheimer points to serious effects of global warming already being felt -- rising sea levels that are eating away at the world's many shoreline developments, and gathering drought in many countries including the United States -- and extensive flooding and worsening storms in other areas.
The fund's Mott said, "Ours is the only global study that regularly plots the effects on the world's wild ecological systems against the decline of world's natural resources," which, of course, humans also use.
Mott says in effect that all the species taken together -- the world's overall ecosystem -- are like the proverbial "canary in the coal mine."