“High in the snowfields atop the Rocky Mountains in Colorado, things are not as pristine as they used to be. Dust from the desert Southwest is sailing into the Rockies in increasing quantities and settling onto the snow that covers the peaks, often streaking the white surface with shades of red and brown.”
~ Jim Robbins
His photo showed a picnic table covered in about 1/2” of red dust, “If you approve that mill, the uranium will blow here and kill us all!” Known to the locals as “red snow”, the dust coats the peaks in the mountains adjacent to the deserts and adds to the early melting of the snowpack.
While reviewing the application for a new uranium mill in southwest Colorado, we had lots of meetings and contact with members of the public. The locals were supportive; however, much of the opposition came from a ski town in a former mining district over fifty miles away. One of their concerns was that the mill and associated mines would contribute dust containing uranium that would blow into the community. Dust storms often swept the area layering a fine red soil over everything, leaving the snow-capped mountains with a reddish hue.
Even though the mines and mill would generate very little dust, we took their concerns seriously. We conducted a study to see where dust from the proposed site would blow, and where dust in that community actually came from. The results showed that the small amount of dust from the site would blow over unpopulated areas and be dispersed. However, most of the dust that reached the community came from deserts in Arizona on the Navajo Reservation about a hundred miles away to the southwest.
I lived down that way for a few years, in Winslow, Arizona, and I can attest to the amount of dust generated in a windstorm. It was a fine red soil, really just silt the consistency of flour. It permeated everything and stained the curtains and carpets. I remember returning home from a day in Flagstaff when there had been a windstorm. We were unable to open the front door of our house — a layer of dust had blown under the door and formed a ridge several inches high on the inside. We were able to enter through the garage to find every surface in the house coated with a quarter inch or more of dust and the inside sill of every window having its own inch-high dust ridge. Having lived in Oklahoma, I was used to the red stain on the towels and other fabrics, but not to the kind of dust that immediately overwhelmed our vacuum cleaner.
Mountain snowpack serves as a reservoir for fresh water, and normally melts gradually over the spring and early summer to provide the flow needed in streams and rivers below. Dust covering the snow changes the albedo, the reflective capability, of the snow and causes earlier melting. This can result in disruption of seasonal streamflow and associated uses, including habitat and ecological functions.
Temperature and precipitation have always varied annually, contributing to the amounts of dust generated each year. However, as reported by Jim Robbins,
“From 2005 to 2008, about five times as much dust fell on the Rockies as during the 1800s, and those years are characterized by researchers as moderately dusty, according to a recent study. In 2009 and 2010, however, the Rockies saw an extreme dust scenario, with the amount of dust blowing onto the mountains mushrooming to five times more than those moderate years. The cause, scientists say, was increasing drought — linked to a warming climate — and human development.”
Human actions directly effect the amount of dust. Farming practices, overgrazing, land development and other activities that eliminate the surface vegetation expose the ground surface to erosion by the wind and water. Timing and conservation practices can mitigate dust generation, but are not always considered. (During the cleanup of an area at the Rocky Flats Weapons Plant in the 1960’s, plutonium-contaminated soils were exposed during the spring and a windstorm spread contaminated dust over a wide area.)
But, dust deposition is a natural mechanism for spreading nutrients, too, including iron (red soils), from one area to others. “Dust is a connector of ecosystems around the world,” said Emma Aronson, a plant pathologist and microbiologist at the University of California at Riverside. Her study found that dust from the Gobi Desert reached the Sierras in California, where it provides an essential source of life-giving phosphorous for the giant sequoias and other trees in the phosphorous-limited ecosystem. Dust is critical in providing nutrients including iron, phosphorous, nitrogen, carbon, and other micronutrients to the oceans.
Dust migration also increases human exposure to dust-borne pathogens and chemically-laden soils, which is a growing health concern in parts of Arizona and California, and around the world, including Japan and Africa. However, with worsening climate – higher winds and less moisture, the impact of practices that remove vegetation will be accelerated. As for the 1930’s dust storms that followed the plowing of the mid-continent prairies, the impacts will not be local, but regional and possibly continental. Locally the productivity of the soil can be damaged, but high levels of dust in the atmosphere can interfere with sunlight reaching the planet’s surface, and the biggest health impacts in many metropolitan areas is from small particulates.
It’s a triple challenge:
- Change people’s attitudes about the looming reality of climate change so that action can be taken.
- Change our agricultural practices to minimize bare ground.
- Plant more trees and vegetation appropriate to the setting.
That doesn’t sound so difficult now, does it?
Jim Robbins, Climate Connection: Unraveling the Surprising Ecology of Dust, November 30, 2017 YaleEnvironment360
Colorado Dust-on-Snow Program, http://www.codos.org/
The Nature Conservancy, Planting Healthy Air, A global analysis of the role of urban trees in addressing particulate matter pollution and extreme heat, August 25, 2016