Tropical peatlands contain around one-sixth of the global peat carbon stock. Decomposition is a key determinant of tropical peat persistence, but there is a scarcity of data on decomposition in tropical peatlands. To further understand decomposition in tropical peatlands, we conducted an 8-year field experiment in a primary peat swamp forest in Brunei. We tracked mass loss and the organic matter composition of Shorea albida wood buried at multiple depths over 8 years, including blocks buried with and without termite exclusion mesh. The proportion of time wood blocks spent above the water table explained the majority of the variation in wood decomposition over time. Carbon loss from wood that spent <1% of the time under the water table was 32.1%-86.5% higher on average than from wood that spent 30%-100% of the time under the water table. We estimate that termites enhanced wood decomposition by similar to 2% per year. Despite significant decomposition, we did not observe a strong shift in wood organic matter composition. To contextualize our results, we synthesized past work on wood decomposition across tropical peatlands. We found that burial in waterlogged peat soils slows decomposition across tropical peatlands and that decomposition is also strongly influenced by peatland trophic status. Overall, our results affirm that waterlogging is the key to tropical peat persistence. Our study highlights the vulnerability of tropical peat carbon stocks to lowered water tables by either drainage or prolonged dry spells, as well as the promise of peatland rewetting to mitigate carbon losses from disturbed peatlands. Plain Language Summary Tropical peatlands store over 100 gigatonnes of carbon in their organic-rich peat soils. This soil carbon persists due to waterlogged conditions that discourage the decomposition (or breakdown) of organic plant material in peat soils. Wood is a large component of organic matter in tropical peat soils, but to date few studies have investigated the controls on wood decomposition in these ecosystems. We used an 8-year field experiment in which we buried wood from a native tree at many depths in a peat swamp in northem Borneo to assess how the proportion of time wood spends in waterlogged conditions impacts decomposition rates. We found that wood that spent at least part of the year under water decomposed >30% less than wood that was never under water. By compiling previous studies, we found that while decomposition is impacted by site-specific factors such as pH, burial in waterlogged peat soils reduces wood decomposition across the tropics. Our results underscore the vulnerability of tropical peat carbon to drainage and drought and support that efforts to restore degraded tropical peatlands by raising the groundwater level have the potential to reduce carbon emissions from peat decomposition.

Abstract Peatlands are among Earth’s largest terrestrial carbon stores and are crucial for climate regulation, biodiversity conservation, and water security. Yet peatlands worldwide are deteriorating under pressures from climate change and human disturbance. Strategic, globally coordinated research is urgently needed to protect, restore and manage peatlands so they can continue to deliver essential ecosystem services. To meet this challenge, here we present a global research prioritisation for peatland science, based on a two-stage online survey and expert voting exercise involving 467 participants from 54 countries. We identify 50 priority research questions spanning carbon dynamics, climate impacts, restoration and management, technological innovation, and community and policy engagement. These questions provide a community-informed agenda to guide peatland research over the next decade. Addressing them will help close critical knowledge gaps, strengthen evidence-based decision making, and support the role of peatlands in achieving global climate and biodiversity goals.

Aims Tropical peatlands have a globally important role as carbon sinks. How their waterlogged conditions and low nutrient status impact plant litter decomposition is not well-understood, despite decomposition processes underpinning carbon sequestration. Our study explored leaf litter decomposition between adjacent paired patches of intact tropical peat forests and kerangas (free-draining heath) forests in Brunei Darussalam and tested the ‘home-field advantage’ effect, which predicts that litter decomposes fastest in the environment it was sourced from due to pre-adaption of the decomposer community. Methods A litter reciprocal transplantation decomposition experiment was conducted across paired peat and kerangas plots using litter from five tree families (Euphorbiaceae, Fabaceae, Lauraceae, Dipterocarpaceae, and Myrtaceae), common to both forest types. Results Contrary to expectations, we found no significant difference in rates of mass or nutrient loss from decomposing litter between peat and kerangas forests irrespective of the litter’s origin, despite differences in environmental conditions between the two environments. We also found no evidence for home-field advantage in either forest. Litter nutrient concentration operated as a key predictor of decomposition, but this effect was independent of forest type. Conclusions The study suggests that differences in surface leaf litter decomposition are unlikely to greatly contribute to the high organic matter accumulation observed in peat forests relative to kerangas forests, indicating that other factors, such as woody debris, branches and tree trunks are more likely to be contributing to their belowground carbon sequestration. This emphasizes the need for further research to explore factors driving organic matter accumulation in tropical peatlands.

Accurate topographic mapping of tropical peatlands is critical for hydrological modeling, carbon stock estimation, and restoration activities. Yet large-scale landscape mapping remains challenging due to limited site access, dense canopy cover and high cost of airborne lidar operations. Here we derived high-resolution digital terrain models (DTMs) over the largest intact peatland complex in Brunei Darussalam using two spaceborne lidar systems, Global Ecosystem Dynamics Investigation (GEDI) and Ice, Cloud, and land Elevation Satellite-2 (ICESat-2). We first refined GEDI and ICESat-2 footprint level elevation estimates by developing an iterative approach constrained by peatland geomorphology, and then explored optimal configurations and interpolation methods to generate 20 m resolution DTM maps. Instead of using highly aggressive noise removal, our approach retained the majority of data after applying standard quality flag (i.e., 87% of GEDI footprints). Comparisons against airborne lidar data show that our iterative filtering procedures could reduce footprint or segment level elevation measurement error by 32.85% for GEDI (RMSE from 4.14 m to 2.78 m) and 63.73% for ICESat-2 (RMSE from 3.64 m to 1.32 m). Removing systematic difference between airborne and satellite DTM further reduced the RMSE to 1.90 m and 0.94 m respectively, underscoring the importance of additional refinement process for measuring tropic peatland topography from lidar satellites. Our interpolation experiments also highlight the trade-offs between data quality and quantity: While the combined use of GEDI and ICESat-2 can improve spatial coverage and better reveal morphological features than either product alone, it only slightly improves estimation accuracy due to both the inherent peatland morphology and limited contributions from relatively low-quality data. In sum, this study provides a framework that uses natural physical constraints to optimize spaceborne DTM generation in tropical peatlands and demonstrates the benefits of combining GEDI and ICESat-2 for peatland terrain mapping, achieving higher data retention and greater terrain extraction accuracy than conventional approaches.

The remineralization of terrestrial dissolved organic carbon (tDOC) plays an important role in coastal carbon and nutrient cycling, and can affect primary productivity and seawater pH. However, the fate of tDOC in the ocean remains poorly understood. Southeast Asia’s Sunda Shelf Sea receives around 10

Peat hydraulic properties play a crucial role in regulating tropical peatland hydrology and are therefore critical parameters in peatland-specific hydrological models. Peat hydraulic and discharge parameters can be estimated by analysing time series of in situ water levels and precipitation, along with topographic data. However, in situ precipitation data are typically not available near water level measurements in densely vegetated and remote tropical peatlands. Gridded satellite precipitation products provide an alternative, but are coarse and highly uncertain. Here, we present a method for the hydrological parameterisation of water level dynamics using satellite-based precipitation, while accounting for representativeness errors in the precipitation data. First, we adapt the water level rise and recession analysis from Cobb and Harvey (Water Resources Research, 55 (11), 9351-9377; 2019) for use with Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) precipitation estimates. Applied to a tropical peatland in Brunei, the adapted rise and recession analysis reduces: (i) the average error in water level rise in response to rainfall and (ii) the average daily recession overestimation. In addition, we quantify the sensitivity of our adapted rise analysis to precipitation errors using an ensemble of precipitation time series with multiplicative errors. Second, the adapted master rise and recession curves are used to fit soil hydraulic and discharge function parameters within the peatland-specific module of the NASA Catchment Land Surface Model. Our analysis enables the retrieval of accurate hydrological parameters for our case study using IMERG data, and can be transferred to other peatlands and satellite-based precipitation products. It also highlights the importance in tropical peatland hydrology of cloud-scale forcing that is not resolved in existing satellite-based precipitation products.

Raised peatlands, or bogs, are recognized as exceptionally carbon-dense terrestrial ecosystems in which peat accumulates into convex shapes that rise above their boundaries. Because of this convexity, bogs are vulnerable to artificial drainage, and mapping them is important to evaluate whether and how to protect or restore their carbon stocks. Recently, we showed that hydrological constraints create a pattern in the morphology of bogs that holds under a broad range of conditions, as illustrated by eight examples of bogs from northern, through tropical and further to southern latitudes. Specifically, we found that if bog surface elevation, mean water table elevation and transmissivity are related to one another in similar ways across a bog, the relationships among these variables define a bog-specific monotonic function that generates the bog morphology from a solution to Poisson’s equation. This pattern is like a signature for raised bog morphology, and could be used to help identify the boundaries of raised bogs. In addition, the pattern can be used to infer the full morphology of bogs from limited data, which in turn enables estimation of a bog’s stock of vulnerable carbon. We discuss how these findings can be combined with field and remote sensing data to better map the extent and vulnerable carbon stocks of raised peatlands around the world.

Tropical peatlands are important global carbon sinks, and the ways they differ from adjacent forest ecosystems in environmental functions have not been well characterized. Our study investigated family-level floristic and soil differences between adjacent paired patches of intact waterlogged peat forests and kerangas (free-draining heath) forests in Brunei Darussalam. For each patch, we examined total and labile nutrient concentrations in soils, tree stand diversity and structural characteristics, functional traits of live leaves and leaf litter, and nutrient resorption during leaf senescence. We found that total nutrients were more abundant in peat and kerangas humus than in kerangas sand, while available nutrients were highest in kerangas humus, suggesting that anoxic conditions in peat soils impair mineralization of nutrients to available forms but do not lead to losses of nutrient capital. We also found significant compositional differences among those families that occur frequently in both peat and kerangas plots. Despite this, family-level measures of tree diversity and structural characteristics, including tree abundance and stand basal area, did not differ between forest types. Similarly, leaf and litter functional traits and nutrient resorption were invariant across forest types, indicating low plasticity of leaf characteristics associated with plant nutrition. This suggests that belowground carbon accumulation in peatlands is disconnected from aboveground plant community characteristics and is likely driven by belowground processes.

This article presents data on ash content and selected nutrients from peat samples collected in the Badas peat swamp forest, located within the largest peat dome in Brunei Darussalam, northwest Borneo. Since the late 1990s, the Badas peat swamp forest has been affected by recurring forest fires near a drainage canal constructed in the 1950s. In 2019, two transects (Transect 1 and Transect 2) were set up perpendicular to the Badas canal, spaced 500 m apart. Peat drives were collected from these transects to quantify ash content and the elemental compositions of aluminium, calcium, iron, and magnesium. A total of 25 sampling points, each with 12 peat drives sampled to a depth of 150 cm, were collected from the two transects using a Russian peat corer. Ash contents were measured to evaluate the applicability of the residual ash method in tropical peatlands. The datasets provide insights into the alteration of the physical and chemical properties of peat caused by fire and are relevant to peatland management and climate change mitigation efforts. Additionally, this dataset can support future studies on the impacts of fire in Borneo peatlands. While the residual ash method has limitations in reliably estimating carbon loss in degraded tropical peatlands, the ash content and elemental composition data presented here provide a valuable baseline for understanding fire-induced changes in peat soil chemistry. These datasets can also support broader ecological assessments, restoration planning, and comparative analyses across tropical peat systems. The Metadata is available in MetaCat in JaLTER at https://jalter.diasjp.net/data/ERDP-2025-05.

Southeast Asia is a global hotspot of peatland degradation and related greenhouse gas emissions. Anthropogenic impacts, mainly associated with agricultural conversion, shift Southeast Asian peatlands from carbon sinks to significant carbon sources. Here we first describe the impacts of anthropogenic drainage on landscape-scale carbon dynamics of individual peatlands and then use an impulse‐response model of radiative forcing to quantify the climate impacts of peat-carbon losses. Whereas water-table elevation (i.e. drainage depth) determines the magnitude of CO2 emissions at the site-scale, the geometric arrangement of artificial drainage networks determines carbon losses on the landscape-scale. Among all peatland greenhouse gas fluxes, the rapid release of large quantities of CO2 with lowered water tables has the greatest impact on atmospheric radiative forcing. While peat accumulation in undisturbed peatlands produces a slowly increasing net radiative cooling, drainage, within decades, causes a shift in radiative forcing to a positive atmospheric perturbation (i.e. net warming), which can persist for centuries to millennia. The pace of this shift in radiative forcing and the magnitude and duration of the warming effect depend on the age and carbon pools of peatlands.

Patchy global data on belowground litter decomposition dynamics limit our capacity to discern the drivers of carbon preservation and storage across inland and coastal wetlands. We performed a global, multiyear study in over 180 wetlands across 28 countries and 8 macroclimates using standardized litter as measures of "recalcitrant" (rooibos tea) and "labile" (green tea) organic matter (OM) decomposition. Freshwater wetlands and tidal marshes had the highest tea mass remaining, indicating a greater potential for carbon preservation in these ecosystems. Recalcitrant OM decomposition increased with elevated temperatures throughout the decay period, e.g., increase from 10 to 20 degrees C corresponded to a 1.46-fold increase in the recalcitrant OM decay rate constant. The effect of elevated temperature on labile OM breakdown was ecosystem-dependent, with tidally influenced wetlands showing limited effects of temperature compared with freshwater wetlands. Based on climatic projections, by 2050 wetland decay constants will increase by 1.8% for labile and 3.1% for recalcitrant OM. Our study highlights the potential for reduction in belowground OM in coastal and inland wetlands under increased warming, but the extent and direction of this effect at a large scale is dependent on ecosystem and OM characteristics. Understanding local versus global drivers is necessary to resolve ecosystem influences on carbon preservation in wetlands.

While a few tropical peatlands remain in pristine condition, many of them, especially in Southeast Asia, have been degraded and have been subjected to drainage, deforestation or fires. At the largest peat deposit in Brunei Darussalam, the Badas peat dome, anthropogenic disturbances arising from urbanisation and land use changes in the past decades have resulted in deforestation, peat subsidence and groundwater drainage. We investigated these disturbances along two transects established at the Badas peat dome via a combination of approaches: (1) topographic survey, (2) seismic refraction survey, (3) rain gauge monitoring and (4) groundwater monitoring via piezometers and slug testing. In addition, groundwater samples were taken from piezometers for water chemistry analysis. This research demonstrated how excavations have led to the creation of lagoons, resulting in changes to the structure of the peat dome, leading to groundwater drainage. The drainage has caused 15 cm to 45 cm of peat thickness to dry out. In addition, with the removal of the peat layer and the establishment of artificial lagoons, surface water can now directly infiltrate into the sand layer, causing the second transect to have a lower groundwater level. Finally, groundwater drainage, evapotranspiration from the lagoons, and possibly tidal influence as the peatland is draining towards the South China Sea less than 3 km away, caused changes to the groundwater chemistry, causing increased salinity and Dissolved Organic Carbon (DOC), showing that peat degradation has been occurring in both transects.

Most peat domes in Southeast Asia are crisscrossed by networks of drainage canals. These canals are a potentially important source of methane to the atmosphere because the groundwater that discharges into them carries high concentrations of dissolved methane that is produced within peat. In this study, we present an isotope‐enabled numerical model that simulates transport, degassing, and oxidation of methane and dissolved inorganic carbon (DIC) along a drainage canal. We then estimate methane fluxes through a 5‐km canal that crosses a disturbed, forested, but undeveloped, peat dome in Brunei Darussalam by applying this model to field data: concentrations and stable carbon isotopic ratios of both methane and dissolved inorganic carbon from both peat porewater and canal water. We estimate that approximately 70% of the methane entering the canal is oxidized within the canal, 26% is degassed to the atmosphere, and 4% is transported toward the ocean, under low to moderate flow conditions. The flux of methane to the atmosphere is lowest at the maximum elevation of the canal, where flow is stagnant and methane concentrations are highest. Downstream, as flow velocity increases, methane emissions plateau even as methane concentrations decrease. The resulting methane emissions from the canal are large compared to emissions from the peat surface and vegetation on a per‐area basis. However, since the canal covers only a small portion of the catchment area, the canal may be a substantial but not dominant source of methane from the peatland.

The 16.8 million ha of peatlands in the Cuvette Centrale wetland complex in the Congo Basin is one of the largest peatland regions on Earth but still highly understudied. Understanding the hydrological functioning of these peatlands and the effects of external disturbances thereon remains a major challenge. Recent research suggested fundamental hydrological differences between the Congo peatlands and the well-studied Southeast Asian peatlands. The Congo peatlands have a doming gradient that is up to ten times smaller, and they are influenced by river hydrology to some extent.In this study, we explore the Congo peatland hydrology through land surface modeling and data assimilation. We build upon our recently developed tropical PEATCLSM module (Apers et al., 2022) that was parameterized based on data from Southeast Asian peatlands due to the lack of field data from other tropical peatland regions. In a first step, we derive Congo-specific peat hydraulic and discharge function parameters from a scalar parametrization of water level dynamics in the Congo peatlands, using observed water level data at two locations. These Congo-specific parameters differ considerably from the original literature-based parameters from Southeast Asian peatlands. In a second step, we apply our original and Congo-specific parameters in an assimilation scheme for L-band brightness temperature (Tb) data from the Soil Moisture and Ocean Salinity (SMOS) mission. The data assimilation results are used in two ways. First, the effect of these parameters on the simulated peatland hydrology and the observation-minus-forecast Tb residuals is evaluated. It is hypothesized that the new parameters reduce the previously reported modeling errors over the Congo peatlands and reduce the residuals in Tb as well. Second, we analyze the data assimilation diagnostics to learn about other model improvement possibilities. In preliminary results, we found long periods of temporally autocorrelated total water storage increments (difference of pre- and post-update) that coincided with anomalies in river stages measured upstream of the peatlands. Since PEATLCSM neglects possible river influence, this concurrence suggests that the typically used grid-based approach of land surface models should be combined with a river routing scheme over the Congo peatlands.Apers, S., De Lannoy, G. J. M., Baird, A. J., Cobb, A. R., Dargie, G. C., del Aguila Pasquel, J., ... & Bechtold, M. (2022). Tropical peatland hydrology simulated with a global land surface model. Journal of advances in modeling earth systems, 14(3), e2021MS002784.

Southeast Asia supports high biodiversity, in a mosaic of forest types formed by the expansion and contraction of habitats through past climate changes. Among the region's forest types, the geographical distribution of peat swamp forests has fluctuated intensely over the past 120,000 years. Most peat swamp forests in Southeast Asia are found in coastal regions and formed within the last 7,000 years after a decline in sea level. However, some peat swamps were initiated earlier on substrates of slightly higher elevation, and these peat swamps might have been refugia for peat swamp species in the last glacial period and the high sea level period. We assessed genetic diversity, genetic structure and divergence time of current genetic groups for Shorea albida in Brunei, an endemic tree species of Bornean peat swamp forests, using 18 microsatellite markers. Genetic diversity was not lower than has been found in other Shorea species, possibly because of the high density of S. albida in Brunei. Although overall genetic divergence between populations was low, two populations (Ingei and Labi Road 3) were distinct from the other populations. Analysis using DIYABC estimated that three genetic groups (Ingei, Labi Road 3 and others) diverged simultaneously from their ancestral population, whose effective size was very small, about 7,500 years ago, corresponding to a recent sea level peak in the Belait-Baram river basin. In that high sea level period, some higher-elevation lands remained, and peat formation had already started in this region. We propose that the current genetic structure of S. albida in Brunei was formed from small refugial populations that survived the period of higher sea level in these higher-elevation areas. Because of their relatively high genetic diversity, Brunei's S. albida populations should become an important genetic resource for the recovery of genetically healthy populations in other parts of northwest Borneo.

Tropical peatlands are estimated to hold carbon stocks of 70 Pg C or more as partly decomposed organic matter, or peat. Peat may accumulate over thousands of years into gently mounded deposits called peat domes with a relief of several meters over distances of kilometers. The mounded shapes of tropical peat domes account for much of the carbon storage in these landscapes, but their subtle topographic relief is difficult to measure. As many of the world's tropical peatlands are remote and inaccessible, spaceborne laser altimetry data from missions such as NASA's Global Ecosystem Dynamics Investigation (GEDI) on the International Space Station (ISS) and the Advanced Topographic Laser Altimeter System (ATLAS) instrument on the Ice, Cloud and land Elevation Satellite-2 (ICESat-2) observatory could help to describe these deposits. We evaluate retrieval of ground elevations derived from GEDI waveform data, as well as single-photon data from ATLAS, with reference to an airborne lidar dataset covering an area of over 300 km2 in the Belait District of Brunei Darussalam on the island of Borneo. Spatial filtering of GEDI L2A version 2, algorithm 1 quality data reduced mean absolute deviations from airborne-lidar-derived ground elevations from 8.35 m to 1.83 m, root-mean-squared error from 15.98 m to 1.97 m, and unbiased root-mean-squared error from 13.62 m to 0.72 m. Similarly, spatial filtering of ATLAS ATL08 version 3 ground photons from strong beams at night reduced mean absolute deviations from 1.51 m to 0.64 m, root-mean-squared error from 3.85 m to 0.77 m, and unbiased root-mean-squared error from 3.54 m to 0.44 m. We conclude that despite sparse ground retrievals, these spaceborne platforms can provide useful data for tropical peatland surface altimetry if postprocessed with a spatial filter.

Tropical peatlands cycle and store globally significant amounts of carbon in their soil and biomass. Climate and land-use change alter greenhouse gas (GHG) fluxes of tropical peatlands, but the magnitude of these changes remains highly uncertain owing to limited measurements. We measured net ecosystem exchanges of carbon dioxide (CO2) and methane (CH4) as well as soil nitrous oxide (N2O) fluxes between mid-2016 and mid-2022 from Acacia crassicarpa plantation, degraded forest and intact forest within the same peat landscape to represent land-cover change trajectories in Sumatra, Indonesia. Here we report the first full plantation rotation GHG balance investigation undertaken in any fiber wood plantation on peatland globally. The Acacia plantation was found to have lower GHG emissions than the degraded peatland, which had a similar mean groundwater level, despite more intensive land-use. The GHG emissions from the Acacia plantation over a full plantation rotation (38.3 ± 4.8 tCO2-eq ha−1 yr−1, average ± standard deviation) were two times higher than those from the intact forest (20.1 ± 3.7 tCO2-eq ha−1 yr−1), but only around half of the current IPCC Tier 1 emission factor for this land-use. Our results should help to reduce the uncertainty in the estimation of GHG emissions from globally important ecosystems, provide a complete estimate of the impact of land-use change on tropical peat, and develop science-based peatland management practices that help to minimize GHG emissions.

Raised peatlands, or bogs, are gently mounded landforms that are composed entirely of organic matter1-4 and store the most carbon per area of any terrestrial ecosystem5. The shapes of bogs are critically important because their domed morphology4,6,7 accounts for much of the carbon that bogs store and determines how they will respond to interventions8,9 to stop greenhouse gas emissions and fires after anthropogenic drainage10-13. However, a general theory to infer the morphology of bogs is still lacking4,6,7. Here we show that an equation based on the processes universal to bogs explains their morphology across biomes, from Alaska, through the tropics, to New Zealand. In contrast to earlier models of bog morphology that attempted to describe only long-term equilibrium shapes4,6,7 and were, therefore, inapplicable to most bogs14-16, our approach makes no such assumption and makes it possible to infer full shapes of bogs from a sample of elevations, such as a single elevation transect. Our findings provide a foundation for quantitative inference about the morphology, hydrology and carbon storage of bogs through Earth's history, as well as a basis for planning natural climate solutions by rewetting damaged bogs around the world.