HUMAN DOMINATION OF EARTHS ECOSYSTEMS

Human alteration of Earth is substantial and growing. Between one-thir d and one-half of the land surface has been transformed by human actio n; the carbon dioxide concentration in the atmosphere has increased by nearly 30 percent since the beginning of the Industrial Revolution; m ore atmospheric nitrogen is fixed by humanity than by all natural terr estrial sources combined; more than half of all accessible surface fre sh water is put to use by humanity; and about one-quarter of the bird species on Earth have been driven to extinction. By these and other st andards, it is clear that we live on a human-dominated planet.