Study: Human activity had a larger impact on Southwestern dust than previously thought

A new study has found that human activity, starting in 1880, has had a much more profound impact on dust in the Southwest than previously thought. 

Researchers at Northern Arizona University and the University of Michigan initially set out to determine if there was any correlation with long drought periods and dust, according to lead researcher Cody Routson.

Specifically Routson, a research professor at NAU, was curious how much of the dust seen across the Southwest was part of a natural occurring phenomenon and how much was created by the effect humans have on the land. 

What he and his colleagues found was that human settlements, spurred on by railroads reaching further than before, reversed a 4,500-year-long process of dust reduction in the southern Rocky Mountains. 

“There was a fair bit of natural change in dustiness,” Routson told the Arizona Mirror, adding that dramatic changes were seen around 1880. “That correlates with when the railroads came into the Southwest that brought in livestock and people.”

The researchers used a variety of techniques, including using X-ray technology to study soil and gather their data. 

Initially, it wasn’t entirely determined in the scientific community what effect human development had on the creation of dust. 

“If we look in the past, there were these big droughts and dust increased a little, but not at the same rate as when industrialized humans came in,” Routson said. 

Dust and water

Dust does more than just create a dangerous nuisance for drivers. It can also impact water supplies, specifically snow melt. 

Snow melt can have a significant impact on water supply in Arizona. Earlier this year, late winter storms caused extra melt, and runoff reached Painted Rock for the first time since 2005. 

But dust can change how and when the snow melts. 

“It changes the surface of the snow from bright and reflective to this dark color,” Routson said. This can cause the snow to melt faster as it reflects less light and even can cause it to sublimate less, leading to less water being released into the atmosphere. 

“Because dust has such a big impact on the water cycle…..understanding what controls dust will have a big influence on that,” Routson said. 

‘We have control over the biggest lever on dust emissions’

Scientists and state employees have already been trying to find ways to combat dust-related issues in the state. 

Researchers at the University of Arizona are currently looking at natural ways to improve poor soil conditions and the state is planning on spending millions to address road conditions on land it owns to prevent excess dust. 

Routson and his colleagues found, however, that those living on the land are the ones who have the most control over future dust issues. 

“As people on the landscape, we have control over the biggest lever on dust emissions,” Routson said. “It gives us more power than I thought we had.”

Identifying the major sources of dust creation is key, Routson said. 

One major source that is already known is livestock. 

Reducing livestock in sensitive areas that are found to be dustier would be a good first step, according to Routson. 

In 2016, a farmer’s land had to be sprayed with a special substance after his land created multiple dust storms that shuttered Interstate 10. The farmer was later fined for practices that were found to have created the excess dust. 

“There are a bunch of questions I’m still really curious about,” Routson said. 

Specifically Routson wants to examine a period of time about 4,000 to 5,000 years ago. Across North America, dry conditions persisted and the monsoons were much stronger, and Routson is curious what those conditions meant for dust across the continent.