Wildfire-enhanced Plio-Pleistocene CO2 drawdown through terrestrial organic carbon burial

• Published in: Quaternary science reviews 2024-08, Vol.338, p.108825, Article 108825
• Main Authors: Sakthivel, Thamizharasan, Ghosh, Prosenjit, Nair, Nisha, Da, Jiawei
• Format: Article
• Language: English
• Subjects: C4 plants expansion; Cosmic ray spallation; Lightning activity; NH4+ fixation; Plio-Pleistocene transition
• ISSN: 0277-3791
• DOI: 10.1016/j.quascirev.2024.108825

The Plio-Pleistocene transition (1.5–3 million years ago, Ma) is marked by a ⁓140 ppm drop in atmospheric CO2 levels, leading to a long-term global cooling. Excess production of organic carbon (OC) from terrestrial vegetation, followed by transport and burial, is responsible for the CO2 decline. The role of wildfire triggering uptake of atmospheric CO2 is proposed for the first time as a viable mechanism to explain vegetational shift, erosion, and burial of OC. Here, we quantified the impact of Fire-Induced Effects (FIE) on the OC burial rates both in the regional and global scales during the interval 4 to 1.5 Ma. A survey of record from Nicobar Fan serves as an ideal burial ground for terrestrial carbon storage due to the deposition of OC derived from wildfire events occurring over the South Asian region. The multi-proxy approach reveals a notable intensification of wildfire activity during the Plio-Pleistocene transition, accompanied by respective 2.9 and 2.4-fold rises in the rate of continental erosion and OC burial fluxes compared to the early Pliocene. On a global scale, we constructed a global wildfire stack using 19 wildfire proxy records sourced from continental and marine sediments. We calculated the global OC burial rate using sediment OC content and Mass Accumulation Rate data from 23 ODP/IODP sites worldwide. Our global data also indicate a 4.8-fold surge in wildfire activity and a 1.5-fold increase in global OC burial rates, from 2.29 ± 0.48 Mt C a−1 in the early Pliocene to 3.52 ± 0.80 Mt C a−1 at the Plio-Pleistocene transition. Our research underscores the pivotal role of FIE in atmospheric CO2 drawdown, which has been seldom discussed in previous studies. •Enhanced wildfire activity over South Asia during the Plio-Pleistocene transition.•Intensified wildfires and organic carbon burial occurred on a global scale.•Fire-Induced Effect (FIE) played a key role in the drawdown of atmospheric CO2.