Humans use 20% of all new plant material
The Brazilian rainforest. Imhoff's study suggests that humans are now using 20% of all new plant matter created on land each year. Other studies have estimated as high as 50%.
DB: This is Earth and Sky, with another story about our human world.
JB: Marc Imhoff is an Earth scientist at Goddard Space Flight Center in Maryland. He studies human consumption of plant material – what scientists call “net primary production.”
Marc Imhoff: So NPP – net primary production – is essentially all the solar energy that’s been captured by plants, turned into organic matter which then we use for food and fiber. And so it’s sort of like the “bio-engine” of planet Earth.
DB: Imhoff and colleagues used satellites to measure how much plant material is created on land in a year. They compared that to U.N. data on how much food and fiber we humans use in a year – and found that we use 20% of Earth’s net primary production – that’s 20% of all new plant matter created on land each year. Other studies have estimated 50%. Imhoff says that as human population and consumption continue to increase, so does our use of solar energy from plants. He’s concerned about that.
Marc Imhoff: So I think from a biodiversity standpoint, there’s some concern about taking too much of that “biofuel,” as I call it . . . that you’re impoverishing what’s left over for all the other species to survive on.
JB: 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 percent.” 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
NASA: NASA Scientists Get Global Fix on Food, Wood & Fiber Use
NASA scientists working with the World Wildlife Fund and others have measured how much of Earths plant life humans need for food, fiber, wood and fuel. The study identifies human impact on ecosystems.
