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Human activity has fundamentally altered wildfire on Earth, creating serious consequences for human health, global biodiversity, and climate change. However, it remains difficult to predict fire interactions with land use, management, and climate change, representing a serious knowledge gap and vulnerability. We used expert assessment to combine opinions about past and future fire regimes from 98 wildfire researchers. We asked for quantitative and qualitative assessments of the frequency, type, and implications of fire regime change from the beginning of the Holocene through the year 2300. Respondents indicated that direct human activity was already influencing wildfires locally since at least ~12,000 years BP, though natural climate variability remained the dominant driver of fire regime until around 5000 years BP. Responses showed a ten-fold increase in the rate of wildfire regime change during the last 250 years compared with the rest of the Holocene, corresponding first with the intensification and extensification of land use and later with anthropogenic climate change. Looking to the future, fire regimes were predicted to intensify, with increases in fire frequency, severity, and/or size in all biomes except grassland ecosystems. Fire regime showed quite different climate sensitivities across biomes, but the likelihood of fire regime change increased with higher greenhouse gas emission scenarios for all biomes. Biodiversity, carbon storage, and other ecosystem services were predicted to decrease for most biomes under higher emission scenarios. We present recommendations for adaptation and mitigation under emerging fire regimes, concluding that management options are seriously constrained under higher emission scenarios.Competing Interest StatementThe authors have declared no competing interest. Introduction Methods and materials Results and discussion Timing and type of future fire regime change Consequences of fire regime change Our capacity to prevent, control, or adapt to future fire regimes Charting a course in a world of uncertainty Expert assessment application in fire management

Funding: This work was supported by the Natural Environment Research Council (Grant No. NE/R016860/1 and NE/R000751/1), the German Research Foundation (BE 2116/32-1) for funding KAH; the Newton-Paulet Institutional Links Grant (Grant ref. 220–2018) for part-funding KHR and LESC, and to the Leverhulme Trust for part-funding LESC (Research Grant RPG-2018-306). Tropical peatlands are a globally important carbon store. They host significant biodiversity and provide a range of other important ecosystem services, including food and medicines for local communities. Tropical peatlands are increasingly modified by humans in the rapid and transformative way typical of the “Anthropocene,” with the most significant human—driven changes to date occurring in Southeast Asia. This review synthesizes the dominant changes observed in human interactions with tropical peatlands in the last 200 years, focusing on the tropical lowland peatlands of Southeast Asia. We identify the beginning of transformative anthropogenic processes in these carbon-rich ecosystems, chart the intensification of these processes in the 20th and early 21st centuries, and assess their impacts on key ecosystem services in the present. Where data exist, we compare the tropical peatlands of Central Africa and Amazonia, which have experienced very different scales of disturbance in the recent past. We explore their global importance and how environmental pressures may affect them in the future. Finally, looking to the future, we identify ongoing efforts in peatland conservation, management, restoration, and socio-economic development, as well as areas of fruitful research toward sustainability of tropical peatlands. Publisher PDF

We are grateful to NERC for funding SAT via the Kalimantan Lestari Project which supported the initial writing of this manuscript (NE/T010401/1, awarded to Prof Frank van Veen). ‘Muddy glee’ by Bracken and Mawdsley made an important contribution to highlighting gender discrimination in fieldwork and the heterogeneity of fieldwork experiences. In the past couple of years, the ability of many researchers to engage in fieldwork has also changed dramatically due to the COVID-19 pandemic. Here, we reflect on Bracken and Mawdsley's paper and our own experiences and perspectives of fieldwork in recent years. We discuss a previous paper we co-authored (entitled ‘Pushing the limits’: experiences of women in tropical peatland research), and the benefits that these papers (e.g., ‘Muddy glee’ and ‘Pushing the limits’) may provide. We highlight the value of sharing personal experiences in science (which is often seen as an ‘objective’ space), and how writing for ourselves can be an empowering and community-building act. Publisher PDF

Southeast Asian peatlands, along with their various important ecosystem services, are mainly distributed in the coastal areas of Sumatra and Borneo. These ecosystems are threatened by coastal development, global warming and sea level rise (SLR). Despite receiving growing attention for their biodiversity and as massive carbon stores, there is still a lack of knowledge on how they initiated and evolved over time, and how they responded to past environmental change, that is, precipitation, sea level and early anthropogenic activities. To improve our understanding thereof, we conducted multi-proxy paleoecological studies in the Kampar Peninsula and Katingan peatlands in the coastal area of Riau and Central Kalimantan, Indonesia. The results indicate that the initiation timing and environment of both peatlands are very distinct, suggesting that peat could form under various vegetation as soon as there is sufficient moisture to limit organic matter decomposition. The past dynamics of both peatlands were mainly attributable to natural drivers, while anthropogenic activities were hardly relevant. Changes in precipitation and sea level led to shifts in peat swamp forest vegetation, peat accumulation rates and fire regimes at both sites. We infer that the simultaneous occurrence of El Niño-Southern Oscillation (ENSO) events and SLR resulted in synergistic effects which led to the occurrence of severe fires in a pristine coastal peatland ecosystem; however, it did not interrupt peat accretion. In the future, SLR, combined with the projected increase in frequency and intensity of ENSO, can potentially amplify the negative effects of anthropogenic peatland fires. This prospectively stimulates massive carbon release, thus could, in turn, contribute to worsening the global climate crisis especially once an as yet unknown threshold is crossed and peat accretion is halted, that is, peatlands lose their carbon sink function. Given the current rapid SLR, coastal peatland managements should start develop fire risk reduction or mitigation strategies.

The status of tropical peatlands, one of Earth’s most efficient natural carbon stores, is of increasing international concern as they experience rising threat from deforestation and drainage. Peatlands form over thousands of years, where waterlogged conditions result in accumulation of organic matter. Vast areas of Southeast Asian peatlands have been impacted by land use change and fires, whilst lowland tropical peatlands of Central Africa and South America remain largely hydrologically intact. To predict accurately how these peatlands may respond to potential future disturbances, an understanding of their long-term history is necessary. This paper reviews the palaeoecological literature on tropical peatlands of Southeast Asia, Central Africa and South America. It addresses the following questions: (i) what were the past ecological dynamics of peatlands before human activity?; (ii) how did they respond to anthropogenic and natural disturbances through the palaeoanthropocene, the period from whence evidence for human presence first appeared?; and, (iii) given their past ecological resilience and current exposure to accelerating human impacts, how might the peatlands respond to drivers of change prevalent in the anthropocene? Throughy synthesising palaeoecological records, this review demonstrates how tropical peatland ecosystems have responded dynamically, persisting through fire (both natural and anthropogenic), climatic and human-induced disturbances in the palaeoanthropocene. Ecosystem resilience does, however, appear to be compromised in the past c. 200 years in Southeast Asian peatlands, faced with transformative anthropogenic impacts. In combination, this review’s findings present a pantropical perspective on peatland ecosystem dynamics, providing useful insights for informing conservation and more responsible management. Natural Environment Research Council (NERC): NE/R016860/1 and NE/R000751/1.

Peat fires in Indonesia are predominantly anthropogenic and intensified by El Nino Southern Oscillation (ENSO)-related droughts. In recent decades, peat fires, which typically occurred in degraded areas (partially/entirely deforested peatlands), released massive amounts of carbon by burning the peat swamp vegetation and peat substrate. However, it could also influence atmospheric nutrient deposition, have a fertilizing effect on peatlands, and enhance their productivity. Little is known about how ENSO-related peat fires would affect the vegetation in times of little or no human impact. It is also unclear whether in the past such an ash-fertilization effect also occurred in the long term and how fires affected peatland carbon sequestration, which is one of their important ecosystem services. In order to understand this, we examine the fire regime, vegetation composition, nutrient status and carbon (C) accumulation rates of the Air Hitam and Sungai Buluh peatlands in Jambi, Sumatra, Indonesia during the Holocene. The results suggest that increased ENSO frequency and magnitude in the Late Holocene increased the fire occurrence and severity in both sites. During times of little human influence, those fires had little effect on peatland vegetation composition. The coincidence of more frequent fires, a nutrient enrichment and an increased carbon accumulation rate in the Late Holocene suggest that ash-fertilization might have also played a role in the recent past. Thus, low-severity fires could potentially enhance the peatlands' capacity to accumulate carbon if the water table is sufficiently high.

The identification and quantification of natural carbon (C) sinks is critical to global climate change mitigation efforts. Tropical coastal wetlands are considered important in this context, yet knowledge of their dynamics and quantitative data are still scarce. In order to quantify the C accumulation rate and understand how it is influenced by land use and climate change, a palaeoecological study was conducted in the mangrove-fringed Segara Anakan Lagoon (SAL) in Java, Indonesia. A sediment core was age-dated and analyzed for its pollen and spore, elemental and biogeochemical compositions. The results indicate that environmental dynamics in the SAL and its C accumulation over the past 400 years were controlled mainly by climate oscillations and anthropogenic activities. The interaction of these two factors changed the lagoon's sediment supply and salinity, which consequently altered the organic matter composition and deposition in the lagoon. Four phases with varying climates were identified. While autochthonous mangrove C was a significant contributor to carbon accumulation in SAL sediments throughout all four phases, varying admixtures of terrestrial C from the hinterland also contributed, with natural mixed forest C predominating in the early phases and agriculture soil C predominating in the later phases. In this context, climate-related precipitation changes are an overarching control, as surface water transport through rivers serves as the "delivery agent" for the outcomes of the anthropogenic impact in the catchment area into the lagoon. Amongst mangrove-dominated ecosystems globally, the SAL is one of the most effective C sinks due to high mangrove carbon input in combination with a high allochthonous carbon input from anthropogenically enhanced sediment from the hinterland and increased preservation. Given the substantial C sequestration capacity of the SAL and other mangrove-fringed coastal lagoons, conservation and restoration of these ecosystems is vitally important for climate change mitigation. peerReviewed