City dwellers feast on plant-derived resources
Satellite Image of New York City in 2002. People in some urban areas need 300 times more plant-derived resources, or net primary production, than the local area produces. (NASA)
DB: This is Earth and Sky. Planet Earth produces over 100 billion metric tons of new plant matter on land each year.
JB: And humans consume about 20% of it as food, fuel and construction materials – according to a 2004 study by Marc Imhoff of Goddard Space Flight Center and his colleagues. Other studies have estimated 50%. Imhoff’s team plotted human consumption of plant materials on a map of the world.
Marc Imhoff: And then what we saw was that many areas of the Earth where you have high populations are of course consuming far, far more than the local landscape could provide.
DB: In some cities, people consume 300 times as much material from plants as local plants can provide. And that puts pressure on ecosystems far from people.
Marc Imhoff: . . . we could look at the interplay between consumption and supply and how dependent we are . . . just as a human culture on this planet, on transportation systems and agricultural production systems that produce a huge amount of food and fiber . . . in other areas and then transport it to the areas where we all live.
JB: And total global consumption of plant material is increasing. Imhoff suggests that technology might help limit the effects of our rising consumption by, for example, making agricultural harvesting more efficient. Special thanks to NASA – explore, discover, understand. We’re Block and Byrd for Earth and Sky.
Read Imhoff’s 2004 paper on human consumption of net primary production.
Read a NASA press release about Imhoff’s study.
We asked David Pimentel, an ecologist at Cornell University, to review this program. With regards to the human consumption of net primary production, he wrote, “In 2001, I estimated the figure to have risen to 50%.” He gave the reference for that work as: Pimentel, D. (2001). The limitations of biomass energy. Encyclopedia on Physical Science and Technology. San Diego, Academic Press: 159-171.
Our thanks to:
Dr. Marc L. Imhoff
ESSP Project Scientist
NASA Goddard Space Flight Center
Greenbelt, MD
Additional Teacher Resources
Science Daily/NASA: NASA Scientists Get Global Fix on Food, Wood and Fiber Use
NASA scientists working with the World Wildlife Fund and others have measured how much of the plant life on Earth humans need for food, fiber, wood and fuel. The study identifies human impact on ecosystems.
NASA: The Human Footprint
Until recently, compiling global maps of human influence simply was not possible, but the 1990s brought substantial technological advances. Satellite data facilitated the production of global land use and land cover maps, and geographic information systems allowed researchers to integrate satellite and population data efficiently. Using these technologies we can now measure human several aspects of human influence: population density, land transformation, human access, and power infrastructure.
