Exploring global patterns of net primary production carbon supply and demand using satellite observations and statistical data

Abstract

A unique combination of satellite and socioeconomic data were used to explore the relationship between human consumption and the carbon cycle. The amount of Earth's net primary production (NPP) required to support human activities is a powerful measure of the aggregate impact on the biosphere and indicator of societal vulnerability to climate change. Biophysical models were applied to consumption data to estimate the annual amount of Earth's terrestrial net primary production humans require for food, fiber (including fabrication) and fuel using the same modeling architecture as satellite-supported NPP measurements. The amount of NPP required was calculated on a per capita basis and projected onto a global map of population to create a spatially explicit map of NPP-carbon "demand" in units of elemental carbon. NPP demand was compared to a map of Earth's average annual net primary production or "supply" created using 17 years (1982-1998) of AVHRR vegetation index to produce a geographically accurate balance sheet of NPP-carbon "supply" and "demand" for the globe. Globally, humans consume 20% of Earth's total net primary production on land. Regionally, the NPP-carbon balance percentage varies from 6% to over 70% and locally from near 0% to over 30,000% in major urban areas. Scenarios modeling the impact of per capita consumption, population growth, and technology suggest that NPP demand is likely to increase substantially in the next 40 years despite better harvesting and processing efficiencies.