Appropriation of potential net primary production by cropland in terrestrial ecoregions

Terrestrial ecoregions of the world have been extensively converted to croplands as a result of human demand for food, fibers, fuels and fodder. Agricultural land cover change has been listed as one of the main drivers of biodiversity loss and change in ecosystem biogeochemical budgets. To provide a quantitative estimate of human impacts on ecosystems, we estimate the amount of net primary production appropriated by the world's croplands from potential natural vegetation cover. Potential net primary production embodied in the 170 crops analyzed was determined using a combination of existing spatial data on crop production and yield statistics, distribution of terrestrial ecoregions and net primary production of potential vegetation. We found that global croplands directly appropriate 9.1 Gt of carbon annually, which is about 14% of potential net primary production. The intensity of human impacts on terrestrial ecoregions differs according to the level of anthropogenic conversion to croplands. Temperate grasslands and savannas have been traditionally converted into croplands and therefore productivity appropriation reaches the highest levels of 34% in aggregate. In addition to the analysis of appropriation of net primary productivity in terrestrial regions, we also report intensity factors describing the embodied amount of productivity lost by conversion of natural regions into croplands. The results of appropriation of original natural net primary production by croplands contribute to discussion of the differences in land use intensity in different countries.