Sand dunes hold a record of fire history

Since scientists have usually relied on sediment records from lake beds to reconstruct fire records, fire histories from dryland regions have often been overlooked. 

Now, a team of researchers led by the University of Queensland (UQ) in Australia has found that sedimentary “archives” in sand dunes could also serve as repositories of fire records and help expand the scientific understanding of fire regions around the world in various historical periods. The study is published in the journal Quaternary Research.

“Knowing how the frequency and intensity of wildfires has changed over time offers scientists a glimpse into Earth’s past landscapes, as well as an understanding of future climate change impacts,” said lead author Nicholas Patton, an expert in Landscape Evolution at the Desert Research Institute (DRI), who conducted this study during his doctoral degree at UQ.

Patton and his colleagues systematically examined sedimentary records preserved in foot-slope deposits of four sand dunes at the Cooloola Sand Mass in Queensland, Australia in order to prove that these sand dune deposits can be used to reconstruct reliable, multi-millennial fire histories, spanning over 12,000 years. 

“The Cooloola Sand Mass consists of large sand dunes that were created off the coast and moved inland from the power of the wind. We were digging soil pits at the base of the dunes and were seeing a lot of charcoal – more charcoal than we expected. And we thought maybe we could utilize these deposits to reconstruct local fires within the area,” Patton explained.

The analyses revealed that, while on the younger dunes (500 and 2,000 years old), charcoal layers represented individual fires – since the steep slope of the dunes quickly buried each layer – the older dunes (5,000 and 10,000 years old) had more gradual slopes which blended charcoal from various fires over time, thus providing a better understanding of periods of increased or decreased fire frequency. 

Moreover, since the dunes offered localized fire histories from within an approximate 100-meter radius, fire records varied slightly among the four dunes, which spanned nearly two kilometers.

“Similar records are likely held in sand dunes around the world, and regions like California and the Southwest U.S. could benefit from a better understanding of regional fire history. Embedded within the fire records is not only information about natural wildfires, but also the way that humans influenced fire regimes,” said Patton.

“Fire histories are important for understanding how fire was used in the past for cultural purposes, whether that was to clear fields for agriculture or for hunting. These records have the potential to unlock the role climate and/or Indigenous peoples had on the landscape from regions where they are rare or absent,” he concluded.

Interesting facts about sand dunes

Dynamic Landscapes

Sand dunes are dynamic natural landscapes that are constantly shifting and changing shape due to wind and water. This is why no two dunes are exactly the same.

Different Types

There are several different types of sand dunes, including barchan, transverse, star, parabolic, and longitudinal, each with its unique shape and formation process.

Wind Direction

The shape and type of a sand dune can often tell you about the predominant wind direction in the area. The windward side of the dune is typically a gentle slope, while the leeward side is steeper.

Living Ecosystems

Though they may seem inhospitable, sand dunes often host a variety of plant and animal life. These organisms have special adaptations to survive the harsh conditions.

Sand Dune Migration

Sand dunes can “migrate” over time. As wind blows sand up the dune, it falls down the other side, causing the whole dune to slowly move.

Importance to the Environment

Dunes play a crucial role in protecting the land against potential ravages by storm waves from the sea. They serve as a natural barrier between the ocean and inland areas.

Human Impact

Human activities can greatly affect the health and stability of dunes. Walking or driving on dunes can damage vegetation and cause erosion, while development can disrupt the natural processes that shape dunes.

Largest Sand Dunes

The world’s tallest sand dunes are the Dunes of Badain Jaran Desert in China. Some of these dunes reach heights of 500 meters (1,640 feet).

Singing Sand

Some sand dunes are known to produce a phenomenon called “singing sand” or “booming dunes.” This happens when the conditions are right, and the sand grains slide down the slopes, creating a deep, humming sound.

Global Distribution

Sand dunes are found on every continent on Earth, including Antarctica where they are made from tiny particles of the rocks and minerals of the Antarctic continent rather than desert sand.

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By Andrei Ionescu, Earth.com Staff Writer

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