HR: 15:45h
AN: A54B-02    [Abstracts]
TI: Global Patterns in Human Harvests of Net Primary Production
AU: * Darwin, R F
EM: rdarwin@ers.usda.gov
AF: USDA, Economic Research Service, 1800 M Street, NW, Washington, DC 20036 United States
AU: Sullivan, J P
EM: johnp@ers.usda.gov
AF: USDA, Economic Research Service, 1800 M Street, NW, Washington, DC 20036 United States
AU: Ingram, K
AF: USDA, Natural Resources Conservation Service, George Washington Carver Center, Beltsville, MD 20705 United States
AU: Imhoff, M L
EM: Marc.L.Imhoff@nasa.gov
AF: Biospheric Sciences Branch, Code 923, NASA Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: Bounoua, L
EM: bounoua@ltpmail.gsfc.nasa.gov
AF: Biospheric Sciences Branch, Code 923, NASA Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: Breneman, V
EM: breneman@er.usda.gov
AF: USDA, Economic Research Service, 1800 M Street, NW, Washington, DC 20036 United States
AB: Humans have a major impact on Earth's ecosystems. Quantifying this impact often involves measuring the fraction of the planet's net primary production (NPP) that humanity appropriates for its own use. Here we measure NPP harvested (NPPh) or the amount of renewable terrestrial organic carbon directly (or indirectly through domestic animals) removed from the landscape and used by people for food, fuel, or fabrication or directly destroyed by burning in the field during 1997. This measure captures only part of NPP appropriated by humans because it does not include NPP appropriated by changes in land use or cover. Nevertheless, it is an important measure because subtracting it from the amount of NPP actually generated on the landscape (NPPact) yields the amount of NPP remaining for other species (NPPt). This presentation contains global maps at 0.5 degree lat./long. resolution identifying (a) source areas and amounts of NPPh, (b) amounts of NPPact, and (c) amounts of NPPt. Our intermediate value of annual global NPPh is 4.3 Pg C per yr or 7.4 percent of NPPact. These estimates are consistent with earlier estimates of NPPh once differences in time and biomass pools are considered. NPPh's shares of NPPact vary spatially both by region and by NPPact. Based on our intermediate value of NPPh, for example, NPPh's shares of NPPact are, on average, 4.8 percent in tropical zones, but 10.9 percent in temperate zones. Areas where NPPh leaves relatively little NPPt (less than 290 g C per square m per yr on average) for other species include portions of Bangladesh, Belgium, China, Egypt, Germany, India, Myanmar (Burma), Nigeria, Pakistan, Poland, the Netherlands, Thailand, the U.S. (e.g., the Midwest), and Vietnam. We also find that in areas where NPPh > 0, the relationship between NPPh's shares of NPPact and NPPact is inverse. This has some important implications for an important measure of biodiversity, species richness, or the number of species of a defined taxon occurring in a defined area. According to the species-energy hypothesis, species richness is positively related to the amount of energy remaining in an ecosystem, i.e., NPPt. Despite controversy regarding the form and cause of species-energy relationships, reviews of the literature indicate that the relationship between species richness and energy is often monotonically increasing, especially at regional, continental, and global scales. Our results imply that humans leave relatively less NPPt (as a percent share of NPPact) on average for low-productivity ecosystems than for high-productivity ecosystems. This suggests, therefore, that humans have reduced species richness of relatively low-productivity ecosystems in temperate and tropical zones more than relatively high-productivity ecosystems in tropical zones.
DE: 0315 Biosphere/atmosphere interactions
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly