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2 November 2011

sustainability

Making Sense of 7 Billion People

Ants and krill and bacteria occupy an entirely different ecological level. A more appropriate comparison can be made between humans and other apex predators, which is precisely the ecological role humans evolved to play, and which — beneath our civilized veneer — we still are.

According to a back-of-the-envelope calculation, there are about 1.7 million other top-level, land-dwelling, mammalian predators on Earth. Put another way: For every non-human mammal sharing our niche, there are more than 4,000 of us.

In short, humans are Earth’s great omnivore, and our omnivorous nature can only be understood at global scales. Scientists estimate that 83 percent of the terrestrial biosphere is under direct human influence. Crops cover some 12 percent of Earth’s land surface, and account for more than one-third of terrestrial biomass. One-third of all available fresh water is diverted to human use.