Source: Geophysical Research Letters

With wildfires growing more frequent and more intense in many parts of the world, scientists are looking to the past to better understand where and when fires have burned. Lakes and wetlands, which capture airborne charcoal particles when they fall from the atmosphere, have provided most records of ancient fires, or paleofires. Now, researchers have found a new tool to help reconstruct fire history: bat poop.

Bats can collect charcoal on their fur as they fly and by brushing up against plants on which charcoal has settled. As they roost in caves and groom themselves, which they do for at least an hour per day, they can ingest—and then poop out—charcoal. Other charcoal particles also may fall to the cave floor, where guano accumulates. Though some previous research has used pollen and nitrogen preserved in bat guano to reconstruct vegetation records and learn more about past climates, no one had used guano records to examine fire histories.

To test whether bat guano accurately recorded fires, Tsalickis et al. collected a 2-meter core of guano buildup from a limestone cave in central Tennessee. Radiocarbon dating revealed that the guano mound started building up around 1952. They analyzed the core centimeter by centimeter, dated the tiny pieces of charcoal they found, and compared that charcoal record to data from historical wildfires and prescribed burns in the area.

The dates from charcoal in the bat poop core matched up with those from the historical fire data, providing the first evidence that guano can be used for paleofire reconstructions. However, because bats hibernate in winter, the records are reliable only for nonwinter fires.

In addition, bat poop charcoal dates correlated more strongly with dates of prescribed burns than of wildfires. That could be because bats flee wildfires (and thus are not in the area to poop out records of the fires) or intentionally seek out prescribed burn areas for foraging (as has been found in previous studies) or a combination of both.

The study gives scientists a new tool for reconstructing paleofire histories where lakes are absent and for distinguishing between human-caused fires and wildfires. (Geophysical Research Letters, https://doi.org/10.1029/2024GL112045, 2024)

—Rebecca Dzombak (@bdzombak), Science Writer

Citation: Dzombak, R. (2024), Bat poop records fire history, Eos, 105, https://doi.org/10.1029/2024EO240480. Published on 31 October 2024.
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