The human species has had a greater impact on the biosphere than any other single species. It is now poised to cause more changes in the future of the biosphere than even photosynthetic bacteria caused when they first filled the atmosphere with oxygen. While human impacts are as old as the human species itself, their pace and extent have grown rapidly, and recent changes have begun to dwarf the consequences of even the most profound change ever brought about by our species, the development of agriculture.

The Coming of Agriculture

Until the development of agriculture, the human species did not affect the biosphere any more significantly than other highly efficient predators. While small nomadic groups could, and did, deplete local game populations, and could, and did, drive some species to the edge of extinction through over-hunting, human impacts were for the most part small, local, and...