NASA scientists working with the World Wildlife Fund and others have measured how much of Earth's plant life humans need for food, fiber, wood and fuel. The study identifies human impact on ecosystems.
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.
By understanding patterns of consumption, and how the planetary supply of plant life relates to the demand for it, these results may enable better management of Earth's rich biological heritage. Understanding the patterns of supply and demand is critical for identifying areas of severe human impact on ecosystems and planning for future growth.
Consumption varies greatly by region, and this study pinpoints areas where human populations require imported basic food, fiber and fuel. Regions with greater demands than available plant-derived resources may be more vulnerable to climate change and other socio-economic impacts. Imports may put greater pressure on ecosystems elsewhere.
Three factors determine human regional ecological impact, population, per capita consumption and technology.
Population plays an important role. Americans consume more than individuals in developing countries, yet U.S. population density is generally lower. Technology helps reduce waste. For example, due to better technology, one ton of milled lumber requires 1.3 tons of trees in industrialized countries but more than 2 tons of trees in developing countries. As a technologically advanced country, U.S. use of NPP is close to the global average.
East and South Central Asia contain almost half the world's population and appropriate 72 percent of regional NPP, despite consuming less per person than any region. If developing nations raised consumption to match the developed world's use per person, humans would consume more than 35 percent of the total annual land NPP.
The research appears in this week's Nature Magazine. For information and images about this research on the Internet, visit: http://www.gsfc.nasa.gov/topstory/2004/0624hanpp.html
For information about NASA and agency programs on the Internet, visit: http://www.nasa.gov
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