Primary Production - Human Impact and Appropriation

Human Impact and Appropriation

Extensive human land use results in various levels of impact on actual NPP (NPP_act). In some regions, such as the Nile valley, irrigation has resulted in a considerable increase in primary production. However, these regions are exceptions to the rule, and in general there is a NPP reduction due to land changes (ΔNPP_LC) of 9.6% across global land-mass. In addition to this, end consumption by people raises the total human appropriation of net primary production (HANPP) to 23.8% of potential vegetation (NPP₀). It is estimated that, in 2000, 34% of the Earth's ice-free land area (12% cropland; 22% pasture) was devoted to human agriculture. This disproportionate amount reduces the energy available to other species, having a marked impact on biodiversity, flows of carbon, water and energy, and ecosystem services, and scientists have questioned how large this fraction can be before these services begin to break down.