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Warmer Temperatures Could Bring More Dust to the Southwest

Three Things You Should Know:

1) Scientists predict decreasing amounts of annual rainfall in the Southwest in coming years as the concentration of greenhouse gases in the atmosphere increases. This means drought conditions in the region may become more frequent and severe over the next century.

2) As the conditions in the Southwest, and along the Colorado Plateau in particular, become drier, many plants will have a tough time surviving. There could be less vegetation covering the land than there has been in the past several decades.

The beginnings of a dust storm in southern Utah. New research suggests a warmer and drier climate in the Southwest could increase dust production. Credit: Casey Myers/flickr.

3) With fewer plants and grasses growing, scientists now say that long-term drought in the Southwest could cause more dust to develop in region, which could affect everything from human health to the local weather and climate.

What the New Science Says:

For the past decade, a nearly unrelenting drought has gripped the Southwest and depleted a water system of rivers, underground aquifers and canals. Water resources in this region were already stressed by population growth. But the worst of the recent drought is also a harbinger of the warmer and drier conditions that climate scientists say are likely to become more frequent and severe during the rest of this century.

Now, with the help of 20 years of records showing how past climate variability in the Southwest has influenced plant growth in parts of the area, researchers have a better idea of how future warm years could cause an increase in the dustiness of the region.

Scientists from the U.S. Geological Survey (USGS) and the University of California, Los Angeles, recently analyzed records spanning 1989 - 2008 of how much plant cover changed in sections of Arches and Canyonlands National Parks in Utah — both of which are located within the Southwest’s Colorado Plateau — depending on how wet or dry, warm or cool a year had been. They discovered that, unsurprisingly, after extremely dry and warm years, which left the land with barely any moisture to spare, there was less vegetation covering the ground. More importantly, however, they found that the same years with little plant growth were also years when the wind more easily wore away at the land and produced immense quantities of dust. The results of the study were published in a March issue of the the Proceedings of the National Academy of Sciences.

"Vegetation on the ground helps keep the soil intact and creates a buffer against the wind that blows through an area," says USGS ecologist Seth Munson, who led the study. "So in years where there was a big decrease in the amount of plant cover, there was an exponential increase in wind erosion and dust production."

In addition to looking back at years with lots of dust, Munson and his coworkers also estimated how dusty things could get in the region in the near future using models of what future plant cover could be depending on changing climate conditions. Several scientific studies have already forecast warmer and drier conditions across much of the Southwest, and cited dust depositied on Rocky Mountain snowcover for melting the snowpack earlier in the spring than normal.

"An important lesson is that increasing temperatures are going to strain water availability," says Munson, explaining that the warmer temperatures cause more water to evaporate out of the soil into the atmosphere. Having less moisture in the ground will hamper plant growth.

How many grasses and plants grow on the land aren’t the only factors determining how much dust is whipped up by the wind, however. A biological soil crust, in which lichens, mosses and certain types of bacteria live in a top layer of undisturbed ground in arid landscapes, can help keep the soil in place and the dust at bay. Munson and his collaborators observed this in the more pristine parts of the parks.

On the other hand, he says, outside the protected area of the national parks, where more land is regularly plowed over, driven across, or trampled on, the soil crust is destroyed and is bound to produce a lot more dust.

Why This Science is Important:

With average temperatures expected to rise across the Southwest in the coming decades, an increasing amount of dust in the air could be an important, and particularly visible, symptom of the changing climate.

"Thinking about dust in terms of climate change is interesting not only because the warmer temperatures can increase dust," says Munson, "but also because the dust, in turn, can have a strong influence on the climate."

This Texas dust storm, in 1935, was a typical sight during the "Dustbowl" drought of the 1930s. Credit: Wikimedia Commons.

He says that clouds of dust swept up into the air can affect how much sunlight gets scattered in the atmosphere, and dust particles can also influence cloud formation. In some cases, more dust could cause local air temperatures to cool. And overall, having more dust in the air could make the dry conditions even worse, just like it is thought to have done during the Dust Bowl of the 1930s.

But the amount of dust kicked up into the air isn’t just problematic for the climate; it can also have health and air quality impacts. As reported earlier this week in the Salt Lake City Tribune, there have already been instances where dust coming from some of Utah’s drier regions has exceeded Salt Lake City's air quality restrictions.

Although the changing climate is undoubtedly going to influence how dry and dusty the Southwest gets (not to mention several other places around the globe, including parts of Africa, China, and Australia), Munson says there are ways to limit dust production. "We have a role in this," he says, "and certainly we can take responsible land management practices into our hands that will help reduce the dust storm activity."

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