Newswise — To comprehend alterations in wildfire frequency and intensity throughout history, scientists can gain insight into past Earth landscapes and future climate change effects. To reconstruct fire records, scientists heavily depend on sediment records from lake beds, which frequently neglect fire histories from arid regions. However, a recent study reveals that sand dunes can function as repositories of fire history, facilitating an extension of scientific knowledge regarding fire regimes worldwide.
The research, published on May 11 in Quaternary Research, represents the first investigation of sedimentary records preserved in foot-slope deposits of sand dunes. The study was conducted by a team of researchers led by Nicholas Patton, Ph.D., a postdoctoral researcher currently at DRI. The team analyzed four sand dunes located in the Cooloola Sand Mass in Australia. Due to Australia's high susceptibility to fires and its extensive areas lacking lakes or ponds to collect sedimentary records from, the researchers aimed to demonstrate that these sand dune deposits could be used to construct reliable, millennial-scale fire histories. These previously unknown archives have the potential to bridge knowledge gaps in arid regions worldwide where fire is a key factor in shaping the environment.
Patton explains that numerous fire and paleoclimate records are situated in areas with abundant water bodies, such as lakes, peats, and bogs. Consequently, most global models exhibit a bias towards temperate regions.
The Cooloola Sand Mass comprises of massive sand dunes, some of which can reach heights of up to 240 meters. These sand dunes originate from the coast and gradually shift inland due to the wind's force. To determine the age of the dunes, Patton's team utilized a dating method called optically stimulated luminescence (OSL). The researchers discovered that the four dunes encompass the Holocene epoch, representing approximately 12,000 years of history.
After a sand dune becomes stable and stops growing, gravity causes sand and remnants of charcoal from local fires to collect at the base of the dune slopes. Over time, this sediment accumulates, creating layers of charcoal from past fire events that can be accurately identified through radiocarbon dating.
Patton explains that while digging soil pits at the dune's base, the team observed a significant amount of charcoal, more than what they anticipated. Realizing the potential of these deposits, the researchers proposed the idea of utilizing them to reconstruct past local fires in the area.
Patton's study revealed that on the younger dunes, which were 500 and 2,000 years old, individual fire events were represented by distinct charcoal layers since the steep slope of the dunes quickly buried each layer. However, the older dunes, which were 5,000 and 10,000 years old, had more gradual slopes that blended charcoal from various fires over time. This provided the researchers with a better understanding of periods of heightened or reduced fire frequency.
Since the dunes provided fire histories within an approximate 100-meter radius, the fire records varied somewhat amongst the four dunes, which covered a distance of around 2 kilometers. However, Patton's team compared their findings to other fire records from the region found in lake and swamp deposits. Comparing to the regional records, the results showed three significant periods of fire activity over the last 7,000 years, which were similar to the findings of the regional records.
According to the researchers, similar records are likely to be present in sand dunes worldwide, and regions like California and the Southwest U.S. could benefit from a better understanding of regional fire history. The fire records not only provide information about natural wildfires but also offer insights into how humans have influenced fire regimes over time.
Patton highlights the significance of fire histories for understanding how fire was utilized for cultural purposes in the past, such as clearing fields for agriculture or hunting.
Patton plans to continue this line of research by studying other dunes near the Cooloola Sand Mass that are almost one million years old to acquire a long-term fire history for the region. As Australia has had human communities for at least 60-70 thousand years, and possibly even longer, these records could help researchers understand the relationship between humans and historical fire regimes.
Patton highlights the excitement of being able to obtain long-term records from these dune deposits, which may not always be available within lake sediments.
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More information: The full study, Reconstructing Holocene fire records using dune foot-slope deposits at the Cooloola Sand Mass, Australia, is available from Quaternary Research.
DOI: https://doi.org/10.1017/qua.2023.14
Study authors include: Nicholas Patton (DRI/Univ. of Canterbury, NZ/Univ. of Queensland, AUS), James Shulmeister (Univ. of Canterbury, NZ/Univ. of Queensland, AUS), Quan Hua (Australian Nuclear Science and Technology Organization), Peter Almond (Lincoln University, NZ), Tammy Rittenour (Utah State Univ.), Johanna Hanson (Univ. of Canterbury, NZ), Aloysius Grealy (Univ. of Queensland, AUS), Jack Gilroy (Univ. of Queensland, AUS), Daniel Ellerton (Univ. of Queensland, AUS/Stockholm Univ.)
About DRI
The Desert Research Institute (DRI) is a recognized world leader in basic and applied environmental research. Committed to scientific excellence and integrity, DRI faculty, students who work alongside them, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge on topics ranging from humans’ impact on the environment to the environment’s impact on humans. DRI’s impactful science and inspiring solutions support Nevada’s diverse economy, provide science-based educational opportunities, and inform policymakers, business leaders, and community members. With campuses in Las Vegas and Reno, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.
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