Satellite measurements were fed into computer models to calculate the annual net primary production (NPP) of plant growth on land. NASA developed models were used to estimate the annual percentage of NPP humans consume. Calculations of domesticated animal consumption were made based on plant-life required to support them.
Marc Imhoff and Lahouari Bounoua, researchers at NASA's Goddard Space Flight Center (GSFC), Greenbelt, Md., and colleagues, found humans annually require 20 percent of NPP generated on land. Regionally, the amount of plant-based material used varied greatly compared to how much was locally grown.
Humans in sparsely populated areas, like the Amazon, consumed a very small percentage of locally generated NPP. Large urban areas consumed 300 times more than the local area produced. North Americans needed almost 24 percent of the region's NPP.
The study did not take into account NPP from the ocean. It also did not include how trade between regions impacted equations. To map land NPP, researchers entered into a model a global satellite derived vegetation index and climate data from 1982 to 1998. The data came from the Advanced Very High Resolution Radiometer on the National Oceanic and Atmospheric Administration Polar Orbiting Environmental Satellites. The multi-year data set was processed at GSFC.
"This study uses the considerable technological assets of NASA's Earth Science Enterprise to better understand how we can maintain the highest possible production of food and fiber while still preserving our biological assets in the face of global change," Imhoff said.