The world's third most populous country behind China and India, the United States has five percent of the world's population. But it consumes -- alone -- more than a quarter of the world's natural resources, more than any other country, according to the National Report on Population and Environment, put out by the US-based Center for Environment and Population.

"The nation's relatively high rates of population growth, natural resource consumption and pollution combine to create the largest environmental impact, felt both within the nation and around the world," the report read.

"The US population has the largest ecological footprint in the world," it adds.

The United States emits almost one quarter of carbon dioxide (CO2) and greenhouse gases -- emissions that are expected to soar 43 percent by 2020.

With more than 237 million vehicles in 2006 (up from 98 million 40 years ago when the population was 200 million) the transport sector alone accounts for a third of CO2 emissions.

The average US driver spends some 47 hours every year in rush hour traffic jams compared to 16 hours 20 years ago, according to the CEP.

And the size of typical American homes has ballooned even as the number of people living in each home has declined from 3.1 per household in 1970 to 2.6 in 2000.

"At the same time, the average size of new single-family homes increased by more than 700 square feet," the report says.

The taste for super-sizing homes has driven up the amount of natural resources used in home construction as well as the amount of energy used to heat them in the winter and cool them in the summer.

Overall, taking into account the space given to housing, schools, roads and commercial areas, each American uses 20 percent more land than in the mid-1980s.

Americans also use an average of three times more water than the average planet resident. Pollution has left roughly 40 percent of US rivers off-limits to fishing and bathing.

Every day, US consumers toss out 2.3 kilos (five pounds) of trash -- an average of five times more than people in developing countries.

Their food consumption, one third of which is animal origin, tops the scales at an average 136 kilos of meat per person compared to 72 kilos for a European and 27 kilos for a resident of a developing country.

With a growing population and a mushrooming demand for resources the country's infrastructure is vulnerable, said Carlos Restrepo, a research scientist at the Wagner School's Institute for Civil Infrastructure Systems (ICIS).

One sign of straining infrastructure is that there have been some 400 blackouts between 1990 and 2004.

Given the interdependence of production and electric distribution systems, and water supplying and oil or gas supplies, breakdowns are taking longer to fix, Restrepo said.

"Those levels of energy consumption are probably not sustainable," he said.

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