Some argue that the US is already overpopulated in terms of ecology and consumption;
''The United States is already overpopulated in the sense that we are consuming our national ecological resources at an unsustainable rate. Our growing dependence on foreign energy supplies is a prime example. We now depend on foreign imports for 28.8 percent of our energy consumption: two-thirds of our petroleum products and about one-sixth of our natural gas consumption.1Because of the abundance of our nation's resources, we have long been careless about our level of consumption, but it is the precipitous rise in the U.S. population over the last four decades that has resulted in our outstripping of our national resources. We are living beyond our means and are doing so increasingly as our population expands. This is a serious problem with major implications for future generations.''
''Nations with high consumption levels generally have large ecological footprints, i.e. environmental impact. Add to the equation a large population with a high level of consumption — as is the case with the United States — and the situation becomes unsustainable. Population growth is steadily diluting the U.S. biocapacity, leaving only about 5 hectares [about 12.4 acres] of productive land available per person. Meanwhile, the steady rise in consumption has increased Americans’ per capita ecological footprint — in part because of our growing dependence on imported energy resources — to more than 9.4 hectares [about 23.3 acres].3 In the last four decades, the U.S. has gone from a positive net ecological surplus of 2.1 hectares per capita to a deficit of -4.4 hectares per capita.4 Another aspect of this same trend into unsustainable consumption is that the U.S. per capita ecological footprint has increased gradually — six percent since 1980 — while per capita biocapacity has decreased rapidly — 26 percent — due to a 30 percent increase in the U.S. population.5''