# Unprecedented Burning in Tropical Peatlands During the 20th Century Compared to the Previous Two Millennia

## TL;DR

Tropical peatlands saw unprecedented wildfires in the 20th century, mainly in Southeast Asia, due to human activities and climate change.

## Contribution

The study provides the first long-term analysis of tropical peatland burning over two millennia, revealing a sharp 20th-century increase.

## Key findings

- Peatland burning was high between 0 and 850 CE, then low until a 20th-century spike.
- 20th-century fire trends increased in Indomalayan and Australasian regions but decreased in others.
- Human activities, not just climate, now drive peatland burning, especially in recent decades.

## Abstract

Tropical peatland wildfire incidence has risen in recent decades, driven by drainage for land use and intensified by severe droughts with global climate change. These disturbances have altered vegetation structure, disrupted ecosystem functioning, and increased carbon emissions, particularly in Southeast Asia. However, the long‐term history and characteristics of wildfires in tropical peatlands remain largely unknown. Here, we compiled fifty‐eight macro‐charcoal records from peatlands across the tropics, ranging from lowland forested to montane peatlands, to assess millennia‐scale changes and controlling factors of tropical peatland burning. We divided the datasets into four main sub‐regions: Neotropical, Afrotropical, Indomalayan and Australasian ecoregions to explore regional variability. Tropical peatlands had high burning levels between 0 and 850 ce, followed by a relatively low and stable period until a marked increase during the 20th century. The general trend in tropical peatland burning follows changes in global temperature, and climate variables that control the length and severity of drought events have a notable influence on peat burning before 1900 ce. During the 20th century, regional differences were observed, with declining fire trends in the Neotropical and Afrotropical regions and increasing fire trends in the Indomalayan and Australasian regions. This difference is likely attributable to human activities, and such intervention is also evident in palm swamps and hardwood swamps under similar wet, weakly seasonal climates. With the increase in anthropogenic pressures on peatlands and greater climate variability, future wildfires in peatlands are likely to become more frequent and widespread across all tropical ecoregions. Conservation and sustainable land‐use practices could be used to mitigate and control peatland burning and protect these carbon‐rich sinks.

This study reveals unprecedented burning in tropical peatlands during the 20th century, mainly expressed in the Indomalayan and Australasian regions, emphasising regional variability in peatland burning and its links to modern human activities. Before this period, tropical peatland burning largely followed changes in global temperature and was influenced by climate variables that control the duration and severity of droughts over the past two millennia. These findings highlight the importance of conservation and sustainable land‐use practices as key strategies for mitigating future peatland wildfires.