Is Net Primary Production a function of human population density?
Abstract
Terrestrial Net Primary Production (NPP) is typically modeled as a function of biophysical variables and land- use. However, in a recent publication on Anthropogenic Biomes, Ellis and Ramankutty postulated that ecosystem functioning today is under direct control of humans. Indeed, here we show that global patterns of NPP also vary as a function of human population density. In highly productive biomes, NPP declines with both increased population density and cultivated land area, while in less productive biomes the opposite is observed. Thus, humans appear to exert a global leveling effect on terrestrial NPP. Moreover, the relationship between NPP and population density holds across cultivation levels, implying that human influence on NPP is not simply the result of changes in land cover. We believe that previous studies have missed this relationship by failing to stratify analyses of human/NPP relationships within specific biomes. Although causality cannot be established by our empirical analysis alone, the population/NPP relationship merits greater study and inclusion in terrestrial ecosystem modeling.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMGC11A0667R
- Keywords:
-
- 0439 Ecosystems;
- structure and dynamics (4815);
- 1615 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 4805;
- 4912);
- 1622 Earth system modeling (1225);
- 1630 Impacts of global change (1225);
- 1632 Land cover change