Studying Soil Erosion from Space




Geologist and geochemist Isaac Larsen at the University of Massachusetts Amherst has a grant from NASA to study soils in a whole new way, from space.

Isaac Larsen is an expert in soil production, erosion, human impact and the evolution of the agricultural landscape, Larsen has been awarded a three-year, $265,000 New Investigator Program grant from NASA’s Earth Science Division.

He says that developing soil loss estimates on large spatial scales is a daunting challenge. “There has been a lot of work on soil erosion on much smaller plots, but taking that information across the landscape is difficult,” he notes. “Using remote sensing as a way to look at the broad scale is promising. We’ll know in very fine detail where soil has been lost.”

Most of this work will use existing images, Larsen says. He and a graduate student will come up with creative ways to use space-based data to study Earth’s soils not only using public NASA data, but also high-resolution commercial images that NASA and the National Geospatial-Intelligence Agency can make available for research by agreement with private companies.

The agricultural landscape south of Clear Lake, Iowa. The light-colored patches in plowed fields are areas where dark-colored, organic-rich topsoil has been lost to erosion. Image courtesy GoogleEarth.

One goal is to estimate how much topsoil has been lost in the former tallgrass prairie since European settlement in the 1800s, from western Illinois to eastern Nebraska and from Missouri and Kansas north to Iowa, Minnesota and the eastern Dakotas. The researchers will create a map and regional analysis that farmers, extension agents and others can use to identify which areas might benefit from changing farm practices.

Larsen proposes to use high-resolution images to map out the presence and absence of topsoil in areas where images are available from the right time of year – either after fall harvest and before it snows, or after the snow melts and before spring planting. “Because of those narrow windows, we don’t have high resolution images everywhere, but we’ve been able to link the extent of soil loss with high-resolution topographic information from Lidar,” another remote-sensing technique, he adds.

Topsoil loss is reversible, as home gardeners know from adding compost and other soil amendments to their plots. Reversing topsoil loss on the farm- to county-scale requires different approaches, Larsen says, but is well worth the effort.

“If we were to restore the organic, carbon-rich part of the topsoil that is the key to soil fertility and productivity, it would represent a large economic advantage to farmers. Something can definitely be done about it. With very aggressive management you can build the soil back up, and studies suggest you can bring topsoil back in less than a decade using such methods as adopting no-till farming, crop rotations, and planting cover crops,” he adds.

Source: University of Massachusetts Amherst



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