Large wildfires are triggering intense dust storms closer to populated areas, new study finds
Post-fire dust storms may have even greater socioeconomic and health effects than their dryland equivalents.
Intense dust storms followed around half of the large wildfires that occurred between 2003 and 2020, according to a new study published in Nature Geoscience today (Oct .17).
The analysis, which covered more than 150,000 global wildfires, could help develop practical solutions to reduce the adverse effects such catastrophes have on society.
Wildfires cause temporarily damaged landscapes, which are a source of dust emission
Large wildfires destroy soil moisture and vegetation cover, making the temporarily damaged landscapes a developing dust emission source. However, little is known about the global extent of post-fire dust events and the factors influencing them.
To help fill this knowledge gap, Paul Ginoux and Professor Yan Yu of Peking University used worldwide satellite measurements on active fires, aerosol abundance and characteristics, vegetation cover, and soil moisture from 2003 to 2020.
Dust events followed 54% of large wildfires within the subsequent 60 days
The authors found that roughly 90 percent of large wildfires during this period were associated with a considerable drop in vegetation cover. Additionally, 54 percent of these wildfires were followed by dust events in the subsequent 60 days.
In this case, a large wildfire was classified as having more than 20 active fires within a 0.1° pixel (about 10 kilometers) during seven consecutive days.
The study also uncovered that about half of post-fire dust events occurred in savannahs. These occurrences could last for several weeks, depending on the severity of the wildfires, their temporal and spatial scope, and their impact on the vegetation cover.
Furthermore, the frequency and intensity of post-fire dust occurrences were shown to be more frequently and severely affected by pre-fire drought conditions.
Future wildfires and associated dust events may become even more extreme
Throughout the study period, the duration of post-fire dust events increased significantly due to intensified regional wildfires and drought conditions due to climate change. The authors predict that future wildfires and associated dust events may become even more extreme due to climate change.
A study earlier this year lends further support to the findings by demonstrating a 50 percent reduction in soil biocrusts due to wildfires, which may also increase dust emissions. Biocrusts are nature’s safeguard against dust storms- they act as a ‘glue’ to prevent soil from blowing away.
The dust storms are closer to populated areas and may have larger impacts
Due to their proximity to populated regions and potential for mixing with hazardous combustion residuals, post-fire dust storms may have even greater socioeconomic and health effects than dryland dust storms.
The researchers highlight that the emitted soil particles may enter the global dust cycle, altering the radiation budget, cloud, and precipitation patterns, as well as oceanic and terrestrial biogeochemistry.
The recently discovered phytoplankton blooms in the Southern Ocean downwind of Australia from December 2019 to March 2020 serve as an example of this relationship. According to scientists, the bloom may have been caused by post-fire dust emissions from the 2019–2020 Australian bushfires.
Emitted particles entering the global dust cycle have both positive and negative outcomes
On the other hand, high-latitude post-fire dust emissions may be a source of light-absorbing aerosols. This could accelerate the darkening and therefore melting of snow.
The researchers highlight that uncertainty exists mainly from the quality of the currently analyzed satellite data.
Overall, the study calls for mitigation measures considering that these drought-fire-dust hazards are likely to increase in frequency and severity due to continuous environmental change.
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