Click image for caption and
other photo information.
New Aid for Savvy Stewardship of
Southwestern Rangelands By
December 30, 2002
Wildlands that border Arizona's scenic Upper San Pedro River are
covered with hardy grasses and rugged desert shrubs. But hungry cattle could
easily overgraze these tasty, nutritious plants. In turn, overgrazing can lead
to flooding and erosion.
To prevent that from happening, scientists at the
Southwest Watershed Research Center
at Tucson, Ariz., are readying a new, computer-based aid that the region's
ranchers, wildlife managers and other specialists can use to safeguard this
ecosystem. The researchers' invention converts--into numerical form--details
about the rangelands. This information comes from satellite imagery, weather
records and studies of how rangeland plants grow.
The Tucson center is part of the
Agricultural Research Service.
With mathematical formulas or equations that the ARS scientists
wrote, an ordinary personal computer can process this information into
customized color maps and other helpful printouts. These display projections of
what plants will be available for the animals in coming months, and where those
plants will be found, given expected weather conditions.
The researchers have dubbed their new, computer-driven
mathematical model "SEHEM," short for "Spatially Explicit Hydro-Ecological
Model." M. Susan Moran, hydrologist and research leader at the Tucson center,
and Yann Nouvellon, a NASA-funded ecologist,
led the work.
Computer models that forecast weather and simulate plant growth
aren't new. What makes SEHEM unique is its reliability and validity over a very
large area--hundreds of square miles. Moran, Nouvellon and co-workers tested
SEHEM by asking it to project rangeland plants' growth for specific periods.
For the test, they chose periods of time for which they already had accurate
information. When they compared SEHEM's projections to these records from
earlier years, they found that the SEHEM output was very close to what had
actually occurred on the rangelands.
To further improve SEHEM, Moran and colleagues are now
fine-tuning the equations that drive it. By 2004, she expects to have a
practical, easy-to-use version ready for users to try out. What's more, Moran
will make SEHEM the basis for a similar model for the Great Basin rangelands of
Utah, Idaho, and Nevada.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.