“What is new in this study is that we have used an alternative approach to demonstrate the impact of high-temperature wildfire events on terrestrial ecosystems,” said Jiao, who is a graduate student at the Chinese Academy of Sciences’ Nanjing Institute of Geology and Palaeontology.
In analysing the content of biomarker compounds from a terrestrial site, Jiao and his colleagues were able to conclude that intense wildfire combustion events could have led to the collapse of terrestrial ecosystems and changes in vegetation during the transition from the Permian to the Triassic period about 250 million years ago.
“Poisonous gases and carbon dioxide – released by volcanic activities and wildfire combustion events – increased the global temperature and resulted in the collapse of the ecosystem,” Jiao said.
“The terrestrial ecosystem collapsed at first, and then the organic compounds on the land entered the ocean, causing ocean deoxygenation and acidity, and leading to a deterioration of the ocean environment.”
According to the authors, the terrestrial ecosystem changed from tropical rainforests in the late Permian period to a barren landscape with low-growing vegetation in the early Triassic era.
Aridification and extreme global warming also played important roles in increasing the frequency and intensity of wildfire events.
The late Permian period (around 251.9 million years ago) had tropical rainforests, but they were not to last. Image: The Chinese Academy of Sciences
This led to the barren landscape and low vegitation of the Early Triassic era. Image: the Chinese Academy of Sciences
For their study, the scientists analysed biomarker compounds called polycyclic aromatic hydrocarbons (PAHs) in 40 samples collected from the Lengqinggou section in Guizhou province of southern China.
The Lengqinggou section is a terrestrial-marine transitional area with deposits from both, and regarded as an important reference point for research of ecosystem evolution in southwestern China during the Permian-Triassic transition period, according to the study.
PAHs in ancient sediments are formed under high temperatures and mainly produced by the incomplete combustion of fuels and plants. Thus they reflect sources related to combustion and are widely used to investigate wildfire activities in geological history.
The study found enriched PAHs in the samples, which suggested a high frequency and intensity of wildfires.
Another geological record-keeping organic matter is charcoal, which is derived from biomass burning. A study by the same research group in 2021 found abundant charcoal in China’s western Xinjiang region as well as Guizhou that also supported the theory of frequent wildfire events and vegetation changeover.
“The enrichment of PAHs in the Permian-Triassic transitional interval … indicates that the frequent and intense wildfire events that occurred during this period may have contributed to deforestation and soil collapse of the terrestrial ecosystem in southwestern China,” the authors said in the study.
Zhang Hua, corresponding author and a researcher with the Chinese Academy of Sciences, said their study showed wildfire events could damage entire regional ecosystems, as their impact on terrestrial vegetation was immediate and often widespread.
“We should increase awareness of the prevention of wildfire events in forests under hot and dry climate conditions,” Zhang was quoted as saying by the state-run Guanming Daily on Wednesday.
“The Earth is getting warmer and wildfires occur in both the northern and southern hemispheres. The current warming may not yet have a significant impact on humans, but it does have a critical impact on the ecosystem,” Jiao warned.
