ABSTRACT
Once upon a time, when humans existed by hunting and gathering and were themselves prey, there was a “natural” landscape. Since then the Earth’s surface, including the biota, topography, surface and groundwater, has been profoundly and irreversibly altered by the direct and indirect effects of human uses of the land (Sala et al. 2000; Vitousek et al. 1997; Wilson 1992). By some analyses, the transformation of the surface due to human activities approaches in magnitude the land cover transformations that have occurred during the transitions from glacial to interglacial climate (Meyer and Turner 1994; National Research Council 2001; Ramankutty and Foley 1999).
