Climate and land use are intimately linked
When we convert a forest to cropland, many climate effects come into play: for example, the amount of sunlight absorbed, the way air moves over land, and the way water moves from soil to air.
JB: This is Earth & Sky. Earlier on the show, we spoke with Marc Imhoff at Goddard Space Flight Center . . .
DB: He’s the author of a 2004 study, indicating that humans consume 20% of all new plant matter growing on land each year.
JB: This year, Imhoff and colleagues are investigating where in the global landscape the most plant matter is being harvested.
Marc Imhoff: . . . and we’re going to look at which land areas are being the most heavily conscripted to produce products of food and fiber.
DB: He also talked about ways that our use of plants changes the landscape. When we replace a forest with crops, for example, the amount of sunlight absorbed by the land changes ? air moves differently over the land ? less water is moved from soil to air ? and so on. In other words, when humans change the land, it affects climate.
JB: But as climate changes, there are feedbacks that affect the land in turn.
Marc Imhoff: For example, if you increase rainfall but it’s during the winter time when it’s cool or too cold to carry out photosynthesis, and then it dries out in the summertime, when temperatures are high enough, then it doesn’t do you much good.
JB: Imhoff hopes his work will help improve computer models predicting future climate change. Meanwhile, scientists are beginning to refer to these sorts of feedbacks as a way in which humans and nature are coupled. And that’s our show. We’re Block and Byrd for Earth & Sky.
Read Imhoff’s 2004 paper on human consumption of net primary production.
See our earlier radio reports featuring Marc Imhoff . . .
Humans use 20% of all new plant material
Urban dwellers feast on plant-derived resources
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
Goddard Space Flight Center
National Aeronautics and Space Administration
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 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.
