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Charcoal stored in preserved guano helps recreate region’s fire history

A view from below of a swarm of bats hanging from the ceiling of a rocky cave. One of them is yawning with its mouth wide open. Credit: R. Andrew King/USFWS, Public Domain

As wildfires increase in frequency and intensity in many parts of the world, scientists are looking to the past to better understand when and where fires occurred. Lakes and wetlands provide most of the records of ancient, or paleofires, because they capture suspended charcoal particles as they fall from the atmosphere. Now, researchers have discovered a new tool that can help reconstruct fire history: bat droppings.

Bats can collect charcoal in their fur while flying or by brushing against charcoal-coated plants. They use caves to roost and groom themselves, which they do for at least an hour a day, allowing them to ingest charcoal and then defecate. Other charcoal particles may also fall to the cave floor, where guano can accumulate.

Several previous studies have used pollen and nitrogen stored in bat guano to reconstruct vegetation records to learn more about past climate, while guano records have been used to investigate fire history. No one used it.

To test whether bat guano accurately recorded fires, Alexandra Tsarikis and colleagues collected two meters of guano cores that had accumulated from a limestone cave in central Tennessee. Radiocarbon dating revealed that the guano mounds began to be deposited around 1952. They analyzed every centimeter of the core, determined the age of the small pieces of charcoal they found, compared the charcoal records to data from past wildfires, and prescribed burns for the area.

The findings will be published in the journal Geophysical Research Letters.

Bat droppings record fire history

(a) Cripps Mill Cave is located in the southeastern United States. (b) Cripps Mill Caverns, located in central Tennessee, is located in an area of ​​both wildfire and prescribed fire. (c) Historically, the annual area burned within 200 km of Cripps Mill Caverns, as well as the relative area burned by wildfires (red), prescribed fires (orange), and unexplained fires (gray). , has fluctuated greatly. In this paper, we focus on the period AD 1998-2018 (green box) and calibrate charcoal preserved in Cripps Mill Cave guano as a proxy for paleofires. Credit: Geophysical Research Letters (2024). DOI: 10.1029/2024GL112045

The ages of the charcoal in the bat fecal cores matched those of past fire data, providing the first evidence that guano can be used to reconstruct old fires. However, because bats hibernate in the winter, records are reliable only for fires outside of the winter.

Additionally, bat fecal charcoal dates were more strongly correlated with prescribed burn dates than with wildfires. This is because bats flee from wildfires (and therefore are not in areas that would give away fire records) and because they intentionally seek out designated burn areas to feed (previous research has shown ), or a combination of both.

This study provides scientists with new tools to reconstruct the history of paleofires in the absence of lakes and to distinguish between human-caused fires and wildfires.

Further information: Alexandra Tsalickis et al, Fire in Feces: Bats Reliably Record Fire History in Their Guano, Geophysical Research Letters (2024). DOI: 10.1029/2024GL112045

This article is republished courtesy of Eos, sponsored by the American Geophysical Union. Read the original story here.

Citation: Charcoal stored in preserved guano helps reconstruct local fire history (October 31, 2024) https://phys.org/news/2024-10-charcoal-guano-reconstruct Retrieved October 31, 2024 from -regional-histories.html

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