Making deserts, from the inside out.
DB: This is Earth and Sky, on the global process of desertification – turning useable land to desert.
JB: Previously on our show, we said that global warming isn’t causing big deserts, like the Sahara, to expand in size. Satellite data – extending back more than 25 years – shows that big deserts are not expanding.
DB: But desertification is happening – on every continent except Antarctica. Christopher Potter is with the Ecosystem Modeling Group at Ames Research Center in Moffett Field, California. He said land can turn to desert when ecosystems gradually fall apart from the inside out.
Christopher Potter: The landscape, whether it’s a desert or anything else, is kind of a mosaic of different patches in it, and in a sparse place like a desert…you might see that areas around plants start to clear out more, so that you have a little more space in between plants. So that that way…it fragments from the inside out, rather than maybe along the edges.
JB: Land turns to desert due to an interaction of complicated factors – some natural, like drought – and some human caused, for example, cutting and burning, over-cultivating, overgrazing and expanding human populations. But Potter pointed out that we humans can also use land wisely.
Christopher Potter: I think humans have a remarkable capacity to restore the land, if we choose to do so and have the opportunities and options to do so.
_DB: Special thanks to NASA explore, discover, understand. We’re Block and Byrd for Earth and Sky.
Read a complete transcript of Earth & Sky’s interview with Christopher Potter.
Our thanks to:
Christopher Potter
Ecosystem Science and Technology Branch
NASA Ames Research Center
Moffett Field, CA
Additional Teacher Resources
U.S. Geological Survey: Desertification
The worlds great deserts were formed by natural processes interacting over long intervals of time. During most of these times, deserts have grown and shrunk independent of human activities. Paleodeserts, large sand seas now inactive because they are stabilized by vegetation, extend well beyond the present margins of core deserts, such as the Sahara. In some regions, deserts are separated sharply from surrounding, less arid areas by mountains and other contrasting landforms that reflect basic structural differences in the regional geology. In other areas, desert fringes form a gradual transition from a dry to a more humid environment, making it more difficult to define the desert border.
NASA Earth Observatory: Defining Desertification
Botswana, 1984-Cattle roam over grasslands at the edge of the Kalahari Desert. Destined to become Botswana’s signature commodity, the cattle will feed the southern African nation and contribute to its rapidly expanding exports. A full 77 percent of the countrys 576,000 square kilometers is already used for grazing, but even this isn’t enough to support the cattle. The grasslands are prone to drought, and the government is forced to import food for them.
