Primary production
In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain. In terrestrial ecoregions, these are mainly plants, while in aquatic ecoregions algae predominate in this role. Ecologists distinguish primary production as either net or gross, the former accounting for losses to processes such as cellular respiration, the latter not.
For other uses, see Primary production (economics).Human impact and appropriation[edit]
Human societies are part of the Earth's NPP cycle, but exert a disproportionate influence in it.[30] In 1996, Josep Garí designed a new indicator of sustainable development based precisely on the estimation of the human appropriation of NPP: he coined it "HANPP" (Human Appropriation of Net Primary Production) and introduced it at the inaugural conference of the European Society for Ecological Economics.[31] HANPP has since been further developed and widely applied in research on ecological economics as well as in policy analysis for sustainability. HANPP represents a proxy of the human impact on Nature and can be applied to different geographical scales and also globally.
The extensive degree of human use of the Planet's resources, mostly via land use, results in various levels of impact on actual NPP (NPPact). Although in some regions, such as the Nile valley, irrigation has resulted in a considerable increase in primary production, in most of the Planet there is a notable trend of NPP reduction due to land changes (ΔNPPLC) of 9.6% across global land-mass.[32] In addition to this, end consumption by people raises the total HANPP [30] to 23.8% of potential vegetation (NPP0).[32] It is estimated that, in 2000, 34% of the Earth's ice-free land area (12% cropland; 22% pasture) was devoted to human agriculture.[33] 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,[32] and scientists have questioned how large this fraction can be before these services begin to break down.[34] Reductions in NPP are also expected in the ocean as a result of ongoing climate change, potentially impacting marine ecosystems (~10% of global biodiversity) and goods and services (1-5% of global total) that the oceans provide.[6]