The western United States, particularly states such as Arizona, California, New Mexico and Utah, has become drier and dustier over the past 40 years, and has experienced a 240 per cent increase in dust storms over that time as a result. Likewise, these same states have also seen an 800 per cent increase in cases of valley fever, a disease with flu-like symptoms which can occasionally be deadly. Researchers do not think this is a coincidence.
‘Valley fever is not contagious, it is caused by the coccidioides fungus, which lives in the soil,’ says Daniel Tong, atmospheric scientist at the National Oceanic and Atmospheric Administration (NOAA) and lead author of the study. He believes that the dust storms are whipping up the soil and transporting the fungus into populated areas. ‘More dust storms increase the chance of the fungus being inhaled by people,’ he says.
In Arizona, where the majority of all US valley fever cases are reported, dust was more strongly correlated with the disease than any other known factors. Nonetheless, this does not make it the sole cause, as the fungus itself grows in wet soil. This means the outbreaks are also related to factors such as rainfall, heat, wind and soil disturbance. Cautious not to get ahead of the findings, Tong states: ‘We found a positive correlation, but we would like to collect more data to help put the pieces together.’
It is crucial to understand this link, since many climate models indicate that we are in for more dust storms in the future. ‘The dust increase could be indicative of changes in large-scale climate systems,’ says Julian Wang, NOAA meteorologist. Specifically, the recent uptick in dust storms is linked to the warming sea surface temperatures of the North Pacific, which brings cooler and drier northerly winds into the southwestern United States. ‘The winds dry out the soil and kick up more dust storms,’ says Wang.
With drier weather expected to trigger stronger dust activity in the coming decades, all implications are being considered. Dust storms can degrade land, worsen asthma, and increase car accidents. ‘These events can transport the impacts of global climate variations onto local society and environments,’ says Wang.
Some of the most devastating dust storms in US history occurred during the Dust Bowl of the 1930s. For now, though, the team feels it is unlikely the storms could reach that scale. ‘The Dust Bowl was as much a human-caused disaster as a natural one,’ says Tom Gill, an environmental scientist at the University of Texas at El Paso. ‘Misguided land care practices, coupled with the Great Depression, magnified the effects of a major drought.’
Since then, modern soil conservation techniques and wind-reducing land practices have softened the impact of droughts that measure even stronger than those encountered in the 1930s. ‘That being said,’ continues Gill, ‘we know that the Southwest is subject to “megadroughts”, which last for decades, and is possibly overdue for one.’ Such a drought – which would be drier than the Dust Bowl – has not happened since European settlement and agricultural development of the region in the 1500s. ‘If – or when – a megadrought occurs, all bets are off,’ he warns.
This was published in the July 2017 edition of Geographical magazine.