Long-Term Research Project Shows Livestock Grazing Is Beneficial To Eastern Colorado's Grasslands Ecosystem
Thursday, November 13, 1997
FORT COLLINS--Bison trampling across Colorado's grasslands
for the past 10,000 years helped condition an entire ecosystem
for livestock grazing today, a Colorado State University research
team discovered in a long-term study.
Results from a 15-year study on 200,000 acres of grassland
in eastern Colorado suggests livestock grazing has little or no
effect on the shortgrass steppe ecosystem. The study shows that
plants adapted to grazing by developing extensive root systems
and short, bushy features above ground. Even some animal species,
such as prairie dogs and mountain plover, rely on grazed portions
of the shortgrass steppe for habitat.
"Through our experiments we consistently find that, contrary
to widespread belief, this particular ecosystem is well-suited
for livestock grazing," said Associate Professor Ingrid Burke,
the project's lead researcher. "Both plants and animals have
adapted survival strategies in light of a long-term presence of
bison in the ecosystem."
Colorado State's Shortgrass Steppe Long Term Ecological
Research (LTER) project is one of 20 funded by the National
Science Foundation. The study, which began in 1982, involves the
Central Plains Experimental Range and Pawnee National Grasslands.
The LTER project involves more than a dozen Colorado State and
international scientists and 45 scientific studies worth about
$12 million.
Researchers focused on the semiarid Great Plains because it
is a major wheat-producing region that also sustains livestock
grazing. Scientists also are interested in the region because
current atmospheric models indicate that climate changes caused
by increased greenhouse gases will be greater in the grasslands
than in most other parts of temperate North America.
By reconstructing eastern Colorado's climate over the past
10,000 years through in-depth studies of the soil, the LTER
project sheds light on how human activities and different land
uses alter the atmosphere and ecosystem.
For example, LTER experiments proved that key plant species
serve as the "glue" that holds the grassland ecosystem together.
Blue grama grass comprises as much as 80 percent of shortgrass
steppe vegetation; without it, the soil becomes infertile and
susceptible to erosion. While blue grama grass is resistant to
drought and livestock grazing, it does not withstand cultivation
agriculture so easily. It was once thought blue grama grass did
not return to an area where it had been disturbed, but LTER
scientists showed that blue grama grass recovers over many
decades.
"We now know how this plant reacts when it is disrupted by
human activities and the critical role it plays in the
sustainability of shortgrass ecosystems," said Bill Lauenroth,
another lead LTER researcher. "These kinds of findings, generated
from long-term observations of the ecosystem, have important
consequences for managing areas disturbed by human activity."
Using techniques to date C-14 and stable isotopes of carbon
left by plants, scientists also determined the region was cooler
and wetter 10,000 years ago than it is today--resulting in a
landscape dominated by cooler-climate cottonwood trees, western
wheatgrass and similar plants. About 8,000 years ago, eastern
Colorado shifted dramatically to warmer and drier conditions that
ushered in grasses and other plants suitable to a warmer
environment. A second climate shift occurred 3,000 years ago,
which caused the formation of widespread sand dunes in
northeastern Colorado.
"We've tried to piece the history of this land together by
studying what's right beneath our feet," said Gene Kelly, a soil
scientist leading this area of research. "The whole idea is to be
able to better understand what happened in the past as a window
to what may happen in the future."
Human activities also affect the region's climate. LTER
studies conducted by atmospheric scientist Roger Pielke Sr. show
that land use patterns change the atmosphere. Pielke's research
shows that irrigation causes more evaporation into the
atmosphere, ultimately triggering more rain-producing clouds and
thunderstorms. Pielke also uses computer models to study how land
surfaces affect weather and climate, and at the same time how
weather and climate alter vegetation and soil dynamics.
"We're not just looking at how these ecosystems work, but
how human behavior has affected them in the past and may affect
them in the future," Burke said. "A great deal of the Earth is in
semi-arid regions like the one we are studying, so much of what
we are able to find is applicable to those areas as well."
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