Politics isn’t the only thing kicking up dust in Colorado.Human activity in the West over the past 200 years has made the region 500 percent dustier than presettlement days, according to a new study by University of Colorado-Boulder researchers.
The paper looks at dust deposition in Colorado’s San Juan Mountains going back 5,000 years.
“From about 1860 to 1900, the dust deposition rates shot up so high that we initially thought there was a mistake in our data,” said the lead author, geologist Jason Neff. “But the evidence clearly shows the western U.S. had its own Dust Bowl beginning in the 1800s when the railroads went in and cattle and sheep were introduced into the rangelands.”
Windblown dust near Utah’s Canyonlands National Park. Photo by Jason Neff
The report says that drought is unlikely to be the cause of the increased dust. Although there have been droughts in the West over the last 200 years, “these droughts have been considerably shorter and less severe than several drought events that have occurred over the 2,000 years in the region, making it unlikely that drought is the primary cause for the increased dust loading observed in this study.”
Instead, the “intensification of western U.S. land use, and particularly livestock grazing activities” is the likely culprit, the paper, published in the journal Nature Geoscience, concludes.
“Overall, nearly 70 percent of the natural ecosystems of the western United States have been affected by livestock grazing, resulting in loss of soil stability and increases in wind erosion of soil. The extensive degradation of western U.S. rangelands led to the Taylor Grazing Act of 1934, which imposed regulations and restrictions on grazing activities in these rangelands. At about this time, the mass accumulation rates of the lake sediments begin a moderate decline, which persists through the second half of the 20th century.”
Dust accumulation has been shown to have important impacts on several levels. For instance, in a paper published last summer, research scientist Tom Painter of the University of Colorado’s Snow and Ice Data Center found that snow in the San Juans was melting 18 to 35 days earlier than usual because of dust cover. All of the global climate models, Painter says, “show that there will a drying and warming in the southwest United States. This leads us to think that we may get greater dust emissions.”
Neff and colleagues say that the increased dust loads may also affect nutrient transport and biogeochemical recycling.