Article

Page SE, Rieley JO, and Banks CJ. Global and regional importance of the tropical peatland carbon pool. Glob Change Biol

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Abstract

Accurate inventory of tropical peatland is important in order to (a) determine the magnitude of the carbon pool; (b) estimate the scale of transfers of peat-derived greenhouse gases to the atmosphere resulting from land use change; and (c) support carbon emissions reduction policies. We review available information on tropical peatland area and thickness and calculate peat volume and carbon content in order to determine their best estimates and ranges of variation. Our best estimate of tropical peatland area is 441 025 km2 (∼11% of global peatland area) of which 247 778 km2 (56%) is in Southeast Asia. We estimate the volume of tropical peat to be 1758 Gm3 (∼18–25% of global peat volume) with 1359 Gm3 in Southeast Asia (77% of all tropical peat). This new assessment reveals a larger tropical peatland carbon pool than previous estimates, with a best estimate of 88.6 Gt (range 81.7–91.9 Gt) equal to 15–19% of the global peat carbon pool. Of this, 68.5 Gt (77%) is in Southeast Asia, equal to 11–14% of global peat carbon. A single country, Indonesia, has the largest share of tropical peat carbon (57.4 Gt, 65%), followed by Malaysia (9.1 Gt, 10%). These data are used to provide revised estimates for Indonesian and Malaysian forest soil carbon pools of 77 and 15 Gt, respectively, and total forest carbon pools (biomass plus soil) of 97 and 19 Gt. Peat carbon contributes 60% to the total forest soil carbon pool in Malaysia and 74% in Indonesia. These results emphasize the prominent global and regional roles played by the tropical peat carbon pool and the importance of including this pool in national and regional assessments of terrestrial carbon stocks and the prediction of peat-derived greenhouse gas emissions.

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... A key component to changing fire regimes in the tropics is to identify the sources of fire and the main land use/land cover classes associated with fire (Cattau et al. 2016 Establishing who is responsible for a fire remains highly contested (Dennis et al. 2005;Page et al. 2011). It often results in a chain of finger-pointing, with no clarity as to the cause of the fire, including those in rainforest (Goldammer 1991). ...
... Later, however, it claimed that wildfires were more likely caused by large companies using fire to open up land for commercial oil palm, pulpwood and timber plantations. Some of these practices were supported by government policies and incentives (Brown 1998;Page et al. 2011). ...
... The scale of land cleared by fire has expanded, with increased use of burning by both smallholders and by larger-scale rubber and oil palm concessions (Stolle and Lambin 2003). Both smallholders and large-scale farmers have been seen as responsible for causing wildfires (Stolle and Lambin 2003; Page et al. 2011). Increasingly, the clearing of land for plantations is considered the main cause of wildfires, such as the 1997-98 blazes that were the worst in Indonesia's history. ...
Article
In Indonesia, the use of fire as a land management practice is regulated by law to counteract its illegal and excessive use, which is often the cause of unwanted wildfires. However, it is often difficult to determine the exact origin of ignition. Perpetrators usually cover their tracks carefully, and judiciary processes by the police and other agencies take considerable time. This article shows how law enforcement has benefitted from the evolution of methods for monitoring fire incidents, using satellite imagery supported by field verification. This has helped to reveal the culprits behind fire incidents, who can then be sentenced to pay fines and compensate for the environmental losses they have caused.
... Peatlands occupy up to 3% of the Earth's land surface but store around 25% of the world's soil carbon (Yu 2012). Peat formation occurs in ecosystems that are either often flooded by water, as in the case of tropical peatlands, or in cold climate conditions as in boreal and Arctic peatlands (Page et al. 2011;Yu 2012;Turetsky et al. 2015). However, peat can be flammable when dry or thawed and wildfires can be ignited by natural events such as lightning (Mickler et al. 2017) and self-heating (Restuccia et al. 2017), or anthropogenic activities such as land clearing, accidental burning, and arson (Page et al. 2002(Page et al. , 2011. ...
... Peat formation occurs in ecosystems that are either often flooded by water, as in the case of tropical peatlands, or in cold climate conditions as in boreal and Arctic peatlands (Page et al. 2011;Yu 2012;Turetsky et al. 2015). However, peat can be flammable when dry or thawed and wildfires can be ignited by natural events such as lightning (Mickler et al. 2017) and self-heating (Restuccia et al. 2017), or anthropogenic activities such as land clearing, accidental burning, and arson (Page et al. 2002(Page et al. , 2011. Their spread is governed by smouldering combustion, and fires can last for weeks or months despite rainfall or firefighting (Page et al. 2002;Huijnen et al. 2016;Rein and Huang 2021) (see Fig. 1). ...
... Slash-and-burn ignition was attempted in P1N, P2N, and P3N by burning dried tree branches, sedges, and litters put together in a pile with dimensions of 8 m in length, 1 m wide, and 0.5 m high (Fig. 7). This ignition mode was chosen because most occurrences of smouldering fires in peatland start with the burning of agricultural waste (Page et al. 2011). During the conversion of peatland into a plantation site, the native surface vegetation is slashed and burned, hence the name slash-and-burn, which is the cheapest way to convert the land. ...
Chapter
O período entre 2018 e 2022 mostrou-nos que o problema dos incêndios à escala global não está a diminuir, antes pelo contrário. Parece que as consequências das alterações climáticas já estão a afectar a ocorrência de incêndios florestais em várias partes do Mundo, de uma forma que só esperaríamos que acontecesse vários anos mais tarde. Em muitos países do Sul da Europa, bem como em algumas regiões dos EUA, Canadá e Austrália, onde estamos habituados a enfrentar a presença de incêndios muito grandes e devastadores, continuamos a ter eventos que quebram recordes. Alguns países, como os da Europa Central e do Norte, que não estavam habituados a ter grandes incêndios, experimentaram-nos durante estes anos. Os anos anteriores foram muito exigentes para todo o Mundo, também noutros aspectos que nos afectaram a todos. Referimo-nos às restrições impostas pela pandemia que limitaram as nossas reuniões e viagens, afectando em muitos casos a saúde dos membros da Comunidade Científica Wildfire. Felizmente, conseguimos encontrar novas formas de comunicação, ultrapassar essas limitações e manter-nos em contacto uns com os outros. Durante semanas e meses, para muitos de nós, as reuniões pessoais e o trabalho de grupo foram substituídos por ligações em linha. Apesar da economia de dinheiro e tempo, e da facilidade de reunir uma grande variedade de pessoas que estas reuniões desde que nos apercebêssemos de que não substituem as reuniões presenciais, que trazem consigo outras dimensões inestimáveis, que fazem parte da comunicação pessoal e ajudam a construir uma comunidade científica.
... Peatland swamp forests (PSF) are grown on waterlogged and nutrient poor peat soil and considered as one of the highly significant natural ecosystems found in temperate, boreal, and tropical region (Yule, 2010;Dommain et al., 2011;Page et al., 2011). These forests play an important role in continuing global ecological stability through climate regulation of carbon sequestration and storage (Page et al., 2011;Kurnianto et al., 2015), hydrological functions of flood prevention and water storage (Harrison, 2013;Lennartz and Liu, 2019), and critical habitat of a wide variety of rare, threatened and declining endemic and unique flora and fauna such as Sumatran orangutan (Pongo abelii), and leopards (Neofelis diardi) (Yule, 2010;Tata et al., 2014;, and providing numerous socio-economic benefits for peoples' livelihoods Kimmel and Mander, 2010;Tata et al., 2014;Nath et al., 2017;Harrison et al., 2020aHarrison et al., , 2020b. ...
... Peatland swamp forests (PSF) are grown on waterlogged and nutrient poor peat soil and considered as one of the highly significant natural ecosystems found in temperate, boreal, and tropical region (Yule, 2010;Dommain et al., 2011;Page et al., 2011). These forests play an important role in continuing global ecological stability through climate regulation of carbon sequestration and storage (Page et al., 2011;Kurnianto et al., 2015), hydrological functions of flood prevention and water storage (Harrison, 2013;Lennartz and Liu, 2019), and critical habitat of a wide variety of rare, threatened and declining endemic and unique flora and fauna such as Sumatran orangutan (Pongo abelii), and leopards (Neofelis diardi) (Yule, 2010;Tata et al., 2014;, and providing numerous socio-economic benefits for peoples' livelihoods Kimmel and Mander, 2010;Tata et al., 2014;Nath et al., 2017;Harrison et al., 2020aHarrison et al., , 2020b. ...
... However, Mohd Azmi et al. (2009) reported that most of the PSF within PFR were categorized as production forests where logging was permitted, and the State land forests could be converted into other land uses (e. g. infrastructure development, agriculture). Studies suggest that PSF deforestation, conversion, and degradation poses major socioeconomic, cultural, and environmental threats (Page et al., 2011;Schrier-Uijl et al., 2013;Hirano et al., 2014;Turetsky et al., 2015). ...
Article
Restoration of degraded forest lands is a global priority that aims to restore ecosystems and their functions in ways that provide multiple socio-economic benefits. The Selangor State Forestry Department (SSFD) of peninsular Malaysia in collaboration with an NGO, local people and other stakeholders had been implemented a community-based restoration of degraded peat swamp forest (1000 hectare) programme in Raja Musa Forest Reserve, North Selangor since 2008. However, socio-economic and ecological impacts of this restoration programme are yet to study fully. In this pioneer study, we followed 5Rs approach to peatland restoration and assessed rewetting status (R1), reduction of fire incidences (R2), revegetation (R3), revitalization (R4) and reporting and monitoring (R5) to understand socio-economic and ecological outcomes of the programme. Data on R1, R2, R3 (restoration approach), R4 (qualitative data on socio-economic outcomes) and R5 (management actions and stakeholders’ participation) were collected through four focus group discussions, five key informant interviews, review of NGO’s documents and a stakeholders’ workshop. Quantitative data on R4 (local peoples’ willingness to contribute (WTC) and socio-economic impact (e. g. benefits, education, awareness) were collected through structured interviews of 200 randomly selected households in four surrounding villages. Data on R3 (ecological outcomes- survival rate and growth of planted trees, status of natural regeneration) were gathered through a series of vegetation survey. Restoration project created jobs (e. g. patrolling) and small business (e. g. forest nursery) opportunities for local people, and enhanced tourism, nature education and research in RMFR thus contributed to locals’ socio-economic development (R4). Local people were WTC to tree planting and maintenance (69 %), canal blocking and maintenance (26 %), forest vigilance (34 %), fire control (35 %), trail construction (27 %), and education and awareness creation (40%) voluntarily without remuneration (R1, R2, R3). The SSFD and NGO adopted an innovative approach of PSF restoration where volunteers (local people and other stakeholders) participated in canals blocking to keep PSF wetted, monthly tree planting events, and education and awareness creation campaigns (R1, R3). Canal blockings helped to maintain a mean ground water level of − 24.96 cm. Due to continuous motivation and awareness creation among surrounding villagers, fire incidents in RMFR were reduced (R2). Between 2008 and 2019, 323.72- hectare plantations were developed mainly with Euodia redlevi tree species and few trees of Shorea leprosula, Myristica lowiana and M. pruinose (R3). Selection of species was done by the SSFD and NGO without input from local people (R5). The mean survival percentage of planted trees was 65%. Mean annual increment (MAI) of diameter and height of E. redlevi decreased from younger plantations (3-year) toward older ones (5-, 7-year) (R3). Overall, MAI (dbh and height) across four tree species between age groups was found significantly different (p = 0.001). Regeneration study identified 16 tree species with an average density of 17,798. E. redlevi was dominant, but only 10.6 % of its regeneration attained young tree stage (R3). Suggestions are made to expedite restoration with diverse tree species (R3) with effective participation of local people (R5) and to ensure post-planting maintenance for greater survival of planted trees (R1, R2, R3).
... Peatlands occupy only 3% of the global terrestrial surface (Vitt and Short, 2020) and are characterised by the accumulation of organic matter from dead and decaying plant debris under water-saturated conditions. Of the world's total peatland area of around 441 Mha (Rieley and Page, 2016), as much as 36-44 Mha or 8-11% is located in tropical regions (Page et al., 2011), and more than half (24.8 Mha or 56%) of this is in Southeast Asia, mostly in Indonesia and Malaysia. Due to the considerable thickness (mean >5 m) of peatlands in these two countries, they contain 77% of the carbon stored in tropical peat globally (Page et al., 2011). ...
... Of the world's total peatland area of around 441 Mha (Rieley and Page, 2016), as much as 36-44 Mha or 8-11% is located in tropical regions (Page et al., 2011), and more than half (24.8 Mha or 56%) of this is in Southeast Asia, mostly in Indonesia and Malaysia. Due to the considerable thickness (mean >5 m) of peatlands in these two countries, they contain 77% of the carbon stored in tropical peat globally (Page et al., 2011). ...
... Amongst these countries, Indonesia contains the largest area (around 13.43 Mha) of tropical peatland (Page et al., 2011;Anda et al., 2021), located mainly on the islands of Sumatra, Kalimantan (Borneo) and Papua (Purnomo et al., 2019). These peatlands contain as much as 57 Gt of carbon, or about 65% of the world's peat carbon (Page et al., 2011) and 7% of the 861 GtC of global forest-based carbon stocks (Pan et al., 2013). ...
Article
Full-text available
Tropical peat swamp forest becomes degraded through forest removal and drainage, usually followed by land use change and fire. Restoration of the degraded peatland requires rewetting, which involves canal blocking and water level management. The purpose of canal blocking is to rewet the peat so that peat-forming trees can re-establish or crops be grown with minimal greenhouse gas emissions and peat subsidence. In addition, wet peat is more fire resistant than degraded dry peat. Canal construction faces several technical problems, including stress that causes bending, water seepage under the dam, and erosion of peat by water forcing its way around the sides when the water level upstream exceeds the dam height. This research examined the behaviour of water flows in canals in peatland in Central Kalimantan after blocking with dams of different designs. This study used a survey method and hydraulic physical model test with a horizontal scale of 1:30 and a vertical scale of 1:10. Field measurements were carried out on the primary canal of the former Mega Rice Project (MRP) Block C to build a physical model test prototype for laboratory research, includes measurement of cross-sections, canal length and water flow for a distance of 100 metres upstream and downstream of the construction. The test included three types of the physical model, reviewed for the effect of flow patterns caused by flood discharge frequencies of 5, 25, 50 and 100 years. The effects of flow patterns on canal dam construction in peatland were obtained from the physical model test.
... Tropical peatlands cover an area of approximately 44 Mha ( ̴ 11% of known peatlands area globally), of which about 25 Mha (56%) are located in Southeast Asia (Page et al. 2011). The important role of tropical peatlands in the global carbon balance and provision of many valuable ecosystem services is widely acknowledged (Page et al. 2011;Uda et al. 2017;Van Eijk and Leenman 2004). ...
... Tropical peatlands cover an area of approximately 44 Mha ( ̴ 11% of known peatlands area globally), of which about 25 Mha (56%) are located in Southeast Asia (Page et al. 2011). The important role of tropical peatlands in the global carbon balance and provision of many valuable ecosystem services is widely acknowledged (Page et al. 2011;Uda et al. 2017;Van Eijk and Leenman 2004). However, rapid human population growth in Southeast Asia has led to increasing demands for food and fibre, resulting in drainage of natural peatland ecosystems for conversion to agricultural use (Koh et al. 2011;Miettinen et al. 2011;Nurulita et al. 2015;Page et al. 2002). ...
... Tropical peatlands are formed by an accumulation of partially decayed woody vegetation under waterlogged conditions, where oxygen deficiency limits decomposition of organic materials (Page and Baird 2016;Page et al. 2011). Under undisturbed conditions, peatlands are characterised by high organic matter with high acidity, low nutrient content and dominance of macropores that facilitate water movement (Cole et al. 2022;Kurnianto et al. 2019;Mustamo et al. 2016). ...
Article
Full-text available
Drainage and conversion of natural peatlands, which increases fire frequency, haze air pollution and carbon emissions, also affects the physical and chemical properties of peat soils. Although there has been continued interest in research on tropical peat soil properties, no attempt has yet been made to synthesise these results. We conducted a systematic literature review and meta-analysis of sixty-six papers published in English language academic literature to explore the current state of knowledge of peat soil properties of Southeast Asia and to compare physical and chemical peat properties (e.g. bulk density, carbon content, pH) under different land uses and depths. Most of these studies were undertaken in Indonesia (56.1%) and Malaysia (28.8%), where substantial tracts of peat soils occur. We extracted data from these papers to calculate the mean of each peat property and compare results between land uses and depths. Linear mixed-effects models were used to test the significance of land use and depth on each peat property. We found that bulk density (44 papers), carbon (C) content (43 papers), pH (42 papers) and nitrogen (N) content (39 papers) were the most widely reported, while other properties remain less studied. Bulk density, pH, phosphorus (P) and calcium (Ca) showed significant differences between land uses and depths. Fibre fraction, potassium (K), iron (Fe) and zinc (Zn) levels showed a significant difference between land uses only, while N differed significantly only between soil depths. Other physical properties such as hydraulic conductivity, porosity, woody fraction, amorphic fraction and chemical properties such as electrical conductivity (EC), C, ammonium (NH 4 ⁺ ), nitrate (NO 3 ⁻ ), available nitrogen (available N), magnesium (Mg), aluminium (Al), copper (Cu), manganese (Mn), sulphur (S) and silicon (Si) showed no significant differences between land uses or depths. This review identifies key research gaps, including underrepresented geographic areas and peat properties and highlights the need for standardised methodologies for measuring peat soil properties.
... Peatlands occupy up to 3% of the Earth's land surface but store around 25% of the world's soil carbon (Yu 2012). Peat formation occurs in ecosystems that are either often flooded by water, as in the case of tropical peatlands, or in cold climate conditions as in boreal and Arctic peatlands (Page et al. 2011;Yu 2012;Turetsky et al. 2015). However, peat can be flammable when dry or thawed and wildfires can be ignited by natural events such as lightning (Mickler et al. 2017) and self-heating (Restuccia et al. 2017), or anthropogenic activities such as land clearing, accidental burning, and arson (Page et al. 2002(Page et al. , 2011. ...
... Peat formation occurs in ecosystems that are either often flooded by water, as in the case of tropical peatlands, or in cold climate conditions as in boreal and Arctic peatlands (Page et al. 2011;Yu 2012;Turetsky et al. 2015). However, peat can be flammable when dry or thawed and wildfires can be ignited by natural events such as lightning (Mickler et al. 2017) and self-heating (Restuccia et al. 2017), or anthropogenic activities such as land clearing, accidental burning, and arson (Page et al. 2002(Page et al. , 2011. Their spread is governed by smouldering combustion, and fires can last for weeks or months despite rainfall or firefighting (Page et al. 2002;Huijnen et al. 2016;Rein and Huang 2021) (see Fig. 1). ...
... Slash-and-burn ignition was attempted in P1N, P2N, and P3N by burning dried tree branches, sedges, and litters put together in a pile with dimensions of 8 m in length, 1 m wide, and 0.5 m high (Fig. 7). This ignition mode was chosen because most occurrences of smouldering fires in peatland start with the burning of agricultural waste (Page et al. 2011). During the conversion of peatland into a plantation site, the native surface vegetation is slashed and burned, hence the name slash-and-burn, which is the cheapest way to convert the land. ...
Article
Full-text available
Peat wildfires can burn over large areas of peatland, releasing ancient carbon and toxic gases into the atmosphere over prolonged periods. These emissions cause haze episodes of pollution and accelerate climate change. Peat wildfires are characterised by smouldering – the flameless, most persistent type of combustion. Mitigation strategies are needed in arctic, boreal, and tropical areas but are hindered by incomplete scientific understanding of smouldering. Here, we present GAMBUT, the largest and longest to-date field experiment of peat wildfires, conducted in a degraded peatland of Sumatra. Temperature, emission and spread of peat fire were continuously measured over 4–10 days and nights, and three major rainfalls. Measurements of temperature in the soil provide field experimental evidence of lethal fire severity to the biological system of the peat up to 30 cm depth. We report that the temperature of the deep smouldering is ~13% hotter than shallow layer during daytime. During night-time, both deep and shallow smouldering had the same level of temperature. The experiment was terminated by suppression with water. Comparison of rainfall with suppression confirms the existence of a critical water column height below which extinction is not possible. GAMBUT provides a unique understanding of peat wildfires at field conditions that can contribute to mitigation strategies.
... These ecosystems are an important carbon sink maintaining abundant decomposed organic matter accumulated over centuries. Peatlands cover about 2.83% (423 Mha) of the earth's land surface (Xu et al., 2018) and are mainly found in temperate and boreal regions, whereas tropics contribute to approximately 10e16% of the total global peatland area (Page et al., 2011). More than half of tropical peatlands (56%) are located in Southeast Asia, most of which are in Indonesia (i.e., 47% of global tropical peatlands) (Hooijer et al., 2006(Hooijer et al., , 2012Page et al., 2011). ...
... Peatlands cover about 2.83% (423 Mha) of the earth's land surface (Xu et al., 2018) and are mainly found in temperate and boreal regions, whereas tropics contribute to approximately 10e16% of the total global peatland area (Page et al., 2011). More than half of tropical peatlands (56%) are located in Southeast Asia, most of which are in Indonesia (i.e., 47% of global tropical peatlands) (Hooijer et al., 2006(Hooijer et al., , 2012Page et al., 2011). Despite their smaller extent, tropical peatlands store 18%e25% of global peat volume and therefore represent a critical role specifically for the carbon cycle and more broadly greenhouse gas emissions (Leifeld and Menichetti, 2018;Page et al., 2011). ...
... More than half of tropical peatlands (56%) are located in Southeast Asia, most of which are in Indonesia (i.e., 47% of global tropical peatlands) (Hooijer et al., 2006(Hooijer et al., , 2012Page et al., 2011). Despite their smaller extent, tropical peatlands store 18%e25% of global peat volume and therefore represent a critical role specifically for the carbon cycle and more broadly greenhouse gas emissions (Leifeld and Menichetti, 2018;Page et al., 2011). Tropical peatlands are at an accelerated rate of degradation owing to the drained condition resulted from drainage canal construction, particularly in Southeast Asian tropical peatlands, which has exponentially increased for plantations and agricultural purposes (Dadap et al., 2021). ...
Chapter
Owing to its large spatial and periodic temporal coverage, satellite remote sensing has emerged for formulating and implementing strategies for natural resources management. This study focuses on an appraisal of satellite sensors and artificial intelligence techniques such as kernels-based support vector machines (SVMs) and artificial neural networks (ANNs). These methods are used for land cover classification on multispectral and microwave satellite images acquired from Landsat-8 and Advanced Land Observing Satellite (ALOS-2) Phased Array type L-band Synthetic Aperture Radar (PALSAR) over Varanasi, India. The analysis shows comparable the performance of the microwave-classified image compared with the multispectral Landsat-8 image. ANNs and SVMs performed best with an overall accuracy of 97.3% and kappa coefficient of 0.97 for the Landsat-8 image, whereas SVM radial basis function was the best classifier for the ALOS PALSAR image with 94% overall accuracy. Other statistical indices such as kappa total disagreement and allocation disagreement scores revealed similar performances. The analysis demonstrated the ability of microwave data in land cover classification studies with satisfactory performance. These data can be used in nearly all weather and environmental conditions for broad image classification purposes when optical and infrared imagery such as Landsat are unavailable.
... Natural wetlands (including coastal wetlands, riparian wetlands and peatlands) are widely considered to be effective for accumulation of carbon (C) and nitrogen (N) into their soils, and therefore to mitigate global climate change (Bernal & Mitsch, 2012;DeLaune et al., 2018;Mcleod et al., 2011;Page et al., 2011). High levels of plant productivity and burial of organic matter into anaerobic soils (e.g., through inputs of undecomposed plant litter and root exudates) are factors contributing to high C and N accumulation rates in wetland soils (Mcleod et al., 2011;Mitsch et al., 2013;Tan et al., 2020). ...
... Peatlands store significant amounts of soil C and N, with much higher C and N stocks than coastal wetlands and riparian wetlands (Table S4). Peatlands contain abundant plant detritus accumulated in the surface soil owing to incomplete decomposition in watersaturated and anaerobic conditions (Page et al., 2011;Scharlemann et al., 2014;Xu, Morris, et al., 2018). However, the conversion of peatlands results in a significant loss of S OC and S TN across all the LULCC types, with the highest annual potential CO 2 emission ( Figure 2; Table 1). ...
Article
Full-text available
Natural wetlands are widely considered important for mitigation of climate change, but they have been impacted by land use and land cover change (LULCC), often resulting in ecosystem degradation and significant changes in soil carbon (C) and nitrogen (N) dynamics. However, the impact of various LULCC types on wetland soil C and N dynamics remains unclear. Global. 1982–2021. Wetland. We present a global meta‐analysis using a database of 487 sites compiled from the literature, demonstrating the response of soil C and N concentrations and stocks in coastal wetlands, riparian wetlands and peatlands to various types of LULCCs, including agricultural lands, drained wetlands, aquaculture ponds, pastures and constructed wetlands. The conversion of coastal wetlands, riparian wetlands and peatlands to most LULCC types decreased the mean soil C and N concentrations and stocks by 17.8 ± 10.3, 25.3 ± 13.4 and 23.2 ± 6.3%, respectively. The loss of wetland soil C owing to LULCC is estimated to cause a potential CO2 emission of 1.8–22.8 Mg CO2 equivalent emission/ha/year, except for conversion to constructed wetlands. The soil C and N contents were more sensitive to LULCCs, relative to the stocks. We also found that the patterns of soil C and N variations were closely related to the conversion time since completion of LULCC. After LULCC, the response of soil C and N variables was sensitive to changes in plant biomass, soil water conditions, bulk density, pH and NH4+‐N concentration, with the major controlling factors varying with the conversion age. Our results highlight the important role of LULCC in triggering soil C and N loss in natural wetlands, which enhances the greenhouse effect. As such, our study calls for sustainable land management strategies aiming at wetland conservation as a powerful tool to mitigate climate warming.
... The corresponding organic soils, Histosols, are important soil organic carbon (SOC) stores that accumulated 600 Pg SOC during the Holocene (Yu et al., 2010). Organic soils spread over almost 500 Mha worldwide, of which the majority, around 400 Mha, is situated in boreal and temperate regions, and 40-70 Mha is located in the tropics (Frolking et al., 2011;Leifeld and Menichetti, 2018;Page et al., 2011). Correspondingly, these soils have high SOC densities of often 1000-2000 t SOC ha −1 (Leifeld and Menichetti, 2018;Page et al., 2011). ...
... Organic soils spread over almost 500 Mha worldwide, of which the majority, around 400 Mha, is situated in boreal and temperate regions, and 40-70 Mha is located in the tropics (Frolking et al., 2011;Leifeld and Menichetti, 2018;Page et al., 2011). Correspondingly, these soils have high SOC densities of often 1000-2000 t SOC ha −1 (Leifeld and Menichetti, 2018;Page et al., 2011). The quasi-continuous SOC accumulation rate of intact peatlands is estimated at 0.22 (northern) and 0.45 (tropical) t C ha −1 yr −1 Loisel et al., 2014), resulting in a net accumulation of annually 0.41-0.51 ...
Chapter
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Organic soils of intact peatlands store 1/4 of the global soil organic carbon (SOC). Despite being an important source of methane (CH4), they are climate coolers because they continuously accumulate new organic carbon. However, when these organic soils are drained for agriculture, the resulting aerobic conditions lead to fast decomposition of the peat and the release of carbon dioxide (CO2) and nitrous oxide (N2O), turning them into net greenhouse gas (GHG) sources. Reducing the environmental footprint of managing these soils requires a good understanding of the processes during drainage of formerly anoxic soil horizons and eventual subsequent rewetting. We describe changes in soil properties and carbon dynamics following drainage of peatlands and discuss management strategies to reduce carbon loss from drained peatlands by raising the water table to either restore the peatland ecosystem, or to cultivate water-tolerant crops. In addition to rewetting, engineering approaches with continuous management at deeper water tables are evaluated in terms of SOC loss.
... Despite occupying only 0.3% of the global land area (Graham et al., 2017), peatlands store about 89 Gt carbon and serve as a large terrestrial CO 2 sink (Wu et al., 2019). It is estimated that southeast Asian tropical peat swamp forests store about 68.5 Gt of carbon (Jauhiainen et al., 2005;Kiew et al., 2018), accounting for 11-14% of the global peat carbon stock (Verwer & Meer, 2010;Page et al., 2011), primarily in huge peat deposits in Sumatra and Borneo. ...
Article
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Tropical peat swamps are essential ecosystems, which provide numerous services, and also serve as a rich source of dissolved organic carbon (DOC), hydrogen ions and trace elements to peat draining rivers. However, not much is known about trace element export from tropical peat swamps. We investigated trace element dynamics in rivers and estuaries draining tropical peat swamps on Borneo, and examined the influence of estuarine processes as well as dissolved organic carbon (DOC) on the distribution and concentration of trace elements. Our results indicate acidic conditions (pH = 3.3) and high DOC concentration (3500 µmol L −1) at salinities<1. We observed an initial release of trace elements at low salinity (0.05<S< 0.5), followed by scavenging to particles at intermediate salinities (0.5<S<10) due to an increasing ionic strength and pH. Peak concentrations (µmol kg −1) of Al (24.9), Si (96.2), Mn (4.9), Cu (0.035) and Ni (0.047) were observed during the dry season (July), and Fe concentrations (43.2) were highest during the wet season (December). We used the NICA-Donnan model to investigate the combined impact of DOC and pH on the formation of solid iron hydroxide (Fe(OH) 3 (s)). The Maludam river was predicted to be supersaturated for Fe hydroxides and the results affirmed our model prediction. The output showed Fe and Cu had a strong affinity for DOC and to a lesser extent Al and Ni in the conditions prevailing at the study sites. Statistical analyses also indicated strong correlation between Cu and Ni (r 2 = 0.97, 0.94 and 0.82) in Maludam, Sebuyau and Belait rivers and estuaries, respectively. The results obtained in this study are comparable to values published for southeast Asia and other continents for pristine peat draining rivers.
... It covers approximately 4 million km 2 and spans 180 countries worldwide. Southeast Asian peatlands constitute 6% of the world's 24.8 million hectares of peatland [1]. Peat swamp forests are crucial to the global carbon (C) cycle and comprise one-third of soil carbon [2]. ...
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: Soil ecosystems are home to a diverse range of microorganisms, but they are only partially understood because no single-cell sequencing or whole-community sequencing provides a complete picture of these complex communities. Using one of such metagenomics approaches, we succeeded in monitoring the microbial diversity and stress-response gene in the soil samples. This study aims to test whether known differences in taxonomic diversity and composition are reflected in functional gene profiles by implementing whole gene sequencing (WGS) metagenomic analysis of geographically dispersed soils from two distinct pristine forests. The study was commenced by sequencing three rainforest soil samples and three peat swamp soil samples. Soil richness effects were assessed by exploring the changes in specific functional gene abundances to elucidate physiological constraints acting on different soil systems and identify variance in functional pathways relevant to soil biogeochemical cycling. Proteobacteria shows abundances of microbial diversity for 52.15% in Royal Belum Reserved Forest and 48.28% in Raja Musa; 177 out of 1,391,841 and 449 out of 3,586,577 protein coding represent acidic stress-response genes for Royal Belum and Raja Musa, respectively. Raja Musa indicates pH 2.5, which is extremely acidic. The analysis of the taxonomic community showed that Royal Belum soils are dominated by bacteria (98% in Sungai Kooi (SK), 98% in Sungai Papan (SP), and 98% in Sungai Ruok (SR), Archaea (0.9% in SK, 0.9% in SP, and 1% in SR), and the remaining were classed under Eukaryota and viruses. Likewise, the soils of Raja Muda Musa are also dominated by bacteria (95% in Raja Musa 1 (RM1), 98% in Raja Musa 2 (RM2), and 96% in Raja Musa 3 (RM3)), followed by Archaea (4% in RM1, 1% in RM2, and 3% in RM3), and the remaining were classed under Eukaryota and viruses. This study revealed that RBFR (Royal Belum Foresr Reserve) and RMFR (Raja Musa Forest Reserve) metagenomes contained abundant stress-related genes assigned to various stress-response pathways, many of which did not show any difference among samples from both sites. Our findings indicate that the structure and functional potential of the microbial community will be altered by future environmental potential as the first glimpse of both the taxonomic and functional composition of soil microbial communities.
... Peatland ecosystems are regarded as highly important by both ecologists and climate scientists due to their essential role in the regulation of the local and regional water balance and their high capacity for carbon storage [1]. Recent studies indicate that tropical peatlands cover 23-30% of the total peatland area in the world, i.e., 90 to 170 Mha [2][3][4], which is much greater than the previous estimates of 36-44 Mha [5][6][7]. This substantial increase in the tropical peatland area is related to new discoveries of large peatlands in remote ...
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Paleoecological reconstructions of hydrological regimes in tropical peatlands during the Holocene are important for the estimation of their responses to changing environments. However, the application of some widely used proxies, such as testate amoebae, is hampered by poor knowledge of their morphology and ecological preferences in the region. The aim of this study is to describe the morphospecies composition of sub-fossil testate amoebae in deposits of a tropical peatland in Central Sumatra (Indonesia) during the Holocene and reconstruct the hydrological regime using morphospecies- and functional-trait-based approaches. In total, 48 testate amoeba morphospecies were observed. Based on morphospecies composition, we distinguished three main periods of peatland development (13,400–8000, 8000–2000, 2000 cal yr BP–present). The application of the morphospecies-based transfer function provided a more reliable reconstruction of the water regime in comparison to the functional trait-based one. The weak performance of the latter might be related to the poor preservation of shells and the greater variation in the functional traits in sub-fossil communities as compared to the training set and linear modeling approach. These results call for future studies on the functional and morphospecies composition of testate amoebae in a wider range of tropical peatlands to improve the quality of hydrological reconstructions.
... It is recognised that Indonesia has one of the largest portions of terrestrial carbon storage, with approximately 57.4 Gigatons or roughly 65% of tropical peat carbon (Page et al., 2011). Equally important, peatlands are a habitat for a variety of flora and fauna. ...
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Indonesian peatlands are facing severe environmental challenges due to unsustainable peatlands management. The Indonesian government has established various regulations in response to international and regional agreements on zero carbon and climate change mitigation and adaptation. The study reviews the chronological impact of peatland regulations on land use/land cover (LULC) conditions in Indonesia, in particular four major peatland areas in Sumatra and Kalimantan. Remote sensing data from 1990 to 2020 is used to generate LULC maps, recorded every 5 years, which were compared within the corresponding year in which regulations were established. The results show that the establishment of Indonesian peatland regulations coincided with the ongoing development of international climate change agreements. Historically, temporal image analysis shows massive land-use change between the years 1995-2010. Since 2010 the deforestation rate has slowed and continues to remain low. Improved peatland maps - identifying high carbon stocks with the minimum required accuracy to take action - remain a priority and can also be used to support sustainable development in Indonesia with more effective planning. The lack of detailed mapping of the capability and condition of peatlands is one of the factors that hinder effective policy development, therefore the implementation of digital soil mapping is recommended to support ongoing peatland security through codification.
... Tropical peatlands contain approximately one sixth of the global soil carbon pool (Page et al., 2022(Page et al., , 2011Xu et al., 2018). ...
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Drainage in tropical peatlands increases CO2 emissions, the rate of subsidence, and the risk of forest fires, among other negative environmental impacts. These effects can be mitigated by raising the water table depth (WTD) using canal or ditch blocks. The performance of canal blocks in raising WTD is, however, poorly understood, because the WTD monitoring data is limited and spatially concentrated around canals and canal blocks. This raises the following question: how effective are canal blocks in raising the WTD over large areas? In this work we composed a process-based hydrological model to assess the rewetting performance of 168 canal blocks in a 22000 ha peatland area in Sumatra, Indonesia. We simulated daily WTD over one year using an existing canal block setup and compared it to the situation without blocks. The study was performed across two El-Niño Southern Oscillation (ENSO) scenarios, and four different peat hydraulic properties. Our simulations revealed that while canal blocks had a net positive impact on WTD rise, they lowered WTD in some areas, and the extent of their effect over one year was limited to a distance of about 600 m around the canals. We also show that canal blocks are most effective during dry periods and in peatlands with high hydraulic conductivity. Averaging over all modelled scenarios, blocks raised the annual mean WTD by only 0.9 cm. This value was 2.78 times larger in the dry year than in the wet year (1.39cm versus 0.50 cm), and there was a 2.76 fold difference between the scenarios with the maximum and minimum hydraulic conductivity (1.50 cm versus 0.54 cm). Using a linear relationship between WTD and CO2 emissions, we estimated that, averaging over peat hydraulic properties, canal blocks prevented the emission of 1.03 Mg ha-1 CO2 in the dry year and 0.37 Mg ha-1 CO2 in the wet year.
... Peat fires may cause prolonged and extreme periods of smoke pollution (haze) that is damaging to human health (Marlier et al., 2013;Page et al., 2002). The role of fire and related peat degradation is well documented in the tropical peat deposits of South-East Asia and South and Central America (Page & Hooijer, 2016;Page et al., 2002Page et al., , 2007Page et al., , 2011Rieley & Page, 2016). The Angolan Highlands landscape and peat deposits are threatened by anthropogenic practices such as extensive fires, slash and burn agriculture, wood and peat fuel extraction, tree clearing, and wetland drainage and overgrazing (Conradie et al., 2016;Taylor et al., 2018). ...
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The Angolan Highlands region includes the Angolan miombo woodland ecoregion which supports miombo woodland, grasslands, subsistence agricultural land, and peatland deposits. Extensive fires, slash and burn agriculture, peat fuel extraction, and peatland drainage are among the anthropogenic practices that threaten these peatland deposits. Peat fires cause peatland degradation, release significant amounts of greenhouse gases, deteriorate air quality, and contribute towards climate change and biodiversity loss. This study presents an analysis of the fire regimes over the period 2001 to 2020 in an under-studied area of the Angolan Highlands. Moderate Resolution Imaging Spectroradiometer (MODIS) fire and vegetation data were used in combination with a land use/land cover (LULC) classification map to calculate fire frequency, burn area, and fire regimes. The fire patterns within the study site are comparable to those found in African woodland savannas. Across the study site, 6976 km² (11.31%) of the land surface area burned at least nine times from 2001 to 2020, occurring largely within in the river valley environment. Considering the different LULC classes, peatlands were calculated to (a) burn more frequently (average fire frequency from 2001 to 2020 = 9.12), (b) have the smallest proportion (4.11%) of area which remained unburnt over the fire archive, and (c) have the largest average proportion (45.65% or 746 km²) of burnt area per year. Peatland burning occurred predominantly during drier months from May to September. The results of this study highlight the strong influence of LULC on the fire frequency and distribution in the study area, requiring unique fire management strategies. As has been documented for boreal and tropical peatlands across the globe, we stress the importance of peatland conservation and protection; continued unsustainable management practices may lead to the loss of these important peatland deposits.
... From 1990 to 2019, for example, the area of drained organic soils steadily increased across Africa and Asia. Southeast Asia, in particular, experienced an acceleration in these trends, driven largely by palm oil cultivation across tropical peatlands(Conchedda and Tubiello 2020), and Indonesia and Malaysia, which collectively hold the vast majority of the region's peatlands(Page et al. 2011;Xu et al. 2018), lost peat swamp forest cover across an area roughly the size of Costa Rica (5.4 Mha) from 1990 to 2010(Miettinen et al. 2012). The conversion and degradation of these two ecosystems risk releasing large soil carbon stocks accumulated over centuries to millennia into the atmosphere.Once disturbed (e.g., construction of aquaculture ponds or drainage for agriculture), both can continue emitting GHGs for decades to centuries, with mangroves emitting a relatively high proportion of their carbon stores rapidly after land-use change and peatlands releasing their significantly larger carbon stores over a much longer time period(Temmink et al. 2022).Although protecting forests, peatlands, and mangroves should be prioritized (Cook-Patton et al. 2021), achieving the Paris Agreement's 1.5°C temperature goal also will require large-scale restoration (IPCC 2022b). ...
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The State of Climate Action 2022 provides a comprehensive assessment of the global gap in climate action across the world’s highest-emitting systems, highlighting where recent progress made in reducing GHG emissions, scaling up carbon removal, and increasing climate finance must accelerate over the next decade to keep the Paris Agreement’s goal to limit warming to 1.5°C within reach.
... A significant proportion of the world's terrestrial carbon stores are within globally important wilderness areas in both the tropics and northern regions (Houghton et al., 2015;Pan et al., 2011), where wilderness loss will result in increased CO 2 releases. Intact forest landscapes constitute up to 20 % of global tropical forest area and store as much as 40 % of the total aboveground tropical forest carbon, while some of the world's largest carbon stores are in boreal peatland wilderness (Potapov et al., 2017;Page et al., 2011). Third, the emergence and spread of zoonoses and infectious diseases are strongly driven by anthropogenic land use and land cover change (LUCC) (Plowright et al., 2021;Morse et al., 2012;Jones et al., 2013), while wilderness conservation could help avoid transmission of zoonotic diseases by reducing wildlife interactions with humans and livestock. ...
Article
Wilderness loss is one of the main threats to biodiversity conservation and sustainable development. The post-2020 Global Biodiversity Framework of the Convention on Biological Diversity proposes "retaining wilderness areas" in the first target of the 21 action-oriented targets for 2030. We conducted a global analysis of projected loss of wilderness area (PLWA) due to land use and land cover change (LUCC) by 2100. This analysis has a spatial resolution of 1 km*1 km and emphasizes the impact of cropland and urban expansion considering multiple SSP-RCP scenarios. We found that a total of 4.6 million km 2 of wilderness is susceptible to cropland and urban expansion (1.3 times larger than India) by 2100. Alarmingly, >51 % of PLWA is concentrated in just ten countries. We call for urgent conservation actions to prevent further wilderness loss.
... Rapid large-scale degradation of tropical peatlands in Southeast Asia (SEA) has occurred in recent times due to economic pressures to convert these ecosystems to plantation, agriculture and human settlement, logging disturbance, and associated drainage and fire (Murdiyarso et al. 2019;Green and Page 2017;Page et al. 2011;Dommain et al. 2011). In Malaysia, Sumatra and Borneo, land use changes, which have involved deforestation and drainage, have resulted in swamp forest cover on peatlands (15.7 Mha) dropping from 76 to 29% between 1990 and 2015 (Miettinen et al. 2016). ...
Article
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Tropical peatlands in Southeast Asia (SEA) have undergone large-scale degradation in recent times due to extensive land use changes and drainage associated with their conversion for economic gains, and resulting fires during dry periods. This has had detrimental impacts on key peatland ecosystem processes and services such as hydrology, peat formation, carbon storage, fire prevention and biodiversity. Palaeoecological and geochemical proxies have been increasingly used in tropical peatland studies to extend contemporary instrumental records of peat conditions. Despite not yet being used to actively inform tropical peatland degradation and restoration interventions, these proxies are able to provide long-term trends in responses, resilience (threshold) and feedback processes of vegetation dynamics, groundwater level, peat pH, peat decomposition and accumulation rates, and degradation history. In this review, through the assessment of relevant tropical peatland studies in SEA, the palaeoecological and geochemical proxies were evaluated for their potential to reconstruct long-term peatland responses to climatically and anthropogenically-driven degradation. This information can potentially be utilised to provide better understanding of the extent of degradation and assist with the development of restoration management plans in SEA through its application in peat-hydrology restoration models.
... This analysis has become routine in the study of peatlands [1][2][3][4]. This is intuitive, as the soil carbon pool of peatlands is immense [5][6][7]. ...
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The carbon pool of Amazonian peatlands is immense and mediates critical ecological functions. As peatlands are dynamic, similar to other wetland systems, modeling of the relationship between organic matter and dry bulk density allows the estimation of the accumulation and/or decomposition of peats. We tested several models: the generalized linear mixed logarithmic, to test depth, and the non-linear logarithmic and power-law models. There is a negative power-law relationship between organic percentage and dry bulk density using peat samples collected in Amazonian peatlands (n = 80). This model is supported by the coefficient of determination (R2) estimates garnered from model fitting, while Akaike Information Criterion (AIC) values further support parsimonious models. We also ran trials of the ideal mixing model with two parameters: k1 representing organic density and k2 representing mineral. The mixture of organic and inorganic components generally falls in accordance with the theory that decreasing k1 trends with increasing k2, although k2 values for these peat samples are negative. The organic k1 coefficient allows us to identify two sites out of the nine investigated, which can be prioritized for their carbon dynamics. The presence of high-density samples, which were not related to depth, indicates clay intrusion in these peatlands. We hope the modeling can explain processes significant to these globally important carbon-rich ecosystems
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Soil moisture deficits and water table dynamics are major biophysical controls on peat and non-peat fires in Indonesia. Development of modern fire forecasting models in Indonesia is hampered by the lack of scalable hydrologic datasets or scalable hydrology models that can inform the fire forecasting models on soil hydrologic behaviour. Existing fire forecasting models in Indonesia use weather data-derived fire probability indices, which often do not adequately proxy the sub-surface hydrologic dynamics. Here we demonstrate that soil moisture and water table dynamics can be simulated successfully across tropical peatlands and non-peatland areas by using a process-based eco-hydrology model (ecosys) and publicly available data for weather, soil, and management. Inclusion of these modelled water table depth and soil moisture contents significantly improves the accuracy of a neural network model in predicting active fires at two-weekly time scale. This constitutes an important step towards devising an operational fire early warning system for Indonesia.
Chapter
Tropical peatland in Indonesia especially in Central Kalimantan has been degraded due to various factors including repeating fires, illegal logging, and conversion into other land use and inappropriate drainage such as the ex-Mega Rice Project. Efforts to revegetate this area have encountered many obstacles due to nutrient poor peat soil characteristic. Arbuscular mycorrhiza is one of potential soil microbes that can be utilized as plant growth-booster in bio-rehabilitation technology particularly in degraded land. However, this bio-rehabilitation-technology has not been utilized intensively to support revegetation of degraded tropical peatland. This paper aimed to summarize the recent progress on the utilization of arbuscular mycorrhiza fungi in supporting the plant’s growth of the peatland revegetation efforts. The result showed that arbuscular mycorrhiza application significantly increased plant’s growth and survival rates especially in the nursery stage. However, compatibility between arbuscular mycorrhiza fungal species and host plants was an important factor that determines the success of colonization and its contribution to plant’s growth performance. Appropriate combination of indigenous mycorrhizal fungal species and native peatland plant species needs to be considered for the success of this bio-rehabilitation technology in revegetating degraded tropical peatland.
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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.
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Manganese (Mn) is an essential plant micronutrient that plays a critical role in the litter decomposition by oxidizing and degrading complex organic molecules. Previous studies report a negative correlation between Mn concentrations and carbon (C) storage in organic horizons and suggest that high Mn concentrations in leaf litter reduce soil C storage in forest ecosystems, presumably by stimulating the oxidation of lignin by fungal enzymes. Yet, the relationship between Mn and C in the litter layer and organic soil remains poorly understood and restricted to a few biomes, hampering our ability to improve mechanistic understanding of soil C accumulation. To examine plant‐soil interactions that underlie observed relationships between Mn and C across a wide range of biomes, we extracted biogeochemical data reported for plants and soils from the National Ecological Observatory Network (NEON) database. We found that increased C and nitrogen (N) storage in organic horizons were associated with declines in Mn concentrations across diverse ecosystems at the continental scale, and this relationship was associated with the degree of organic matter decomposition (i.e., Oi, Oe, and Oa). Carbon and N stocks were more strongly correlated with Mn than with climatic variables (i.e., temperature and precipitation). Foliar Mn was strongly correlated with foliar lignin, and both these parameters increased with a decrease in soil pH, indicating links between soil pH, foliar chemistry, and litter decomposability. Our observations suggest that increased Mn bioavailability and accumulation in foliage under moderately acidic soil conditions support fungal decomposition of lignin‐rich litter and contributes to lower soil C stocks.
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Tropical peatlands in Indonesia are severely degraded due to unsustainable logging, conversion to plantations, poor drainage, and repeated fires. Traditional communities in Central Kalimantan used to build “beje” ponds for fishing and paludikulur farming system (agrosilvo fishery) in deep peatlands area that are frequently flooded. However, hardly reached spot in peat swamp makes areas suitable for beje difficult to find. This study aims to map the location suitable for beje using Normalized Difference Water Index (NDWI) from Landsat 8 OLI imagery. Canopy results from the NDWI were used as a reference for field investigations at nine sites from each NDWI class. The classification test results show that NDWI is able to distinguish dry and wet areas in tropical peatlands, with a manufacturer accuracy of 83.3% and user accuracy of 84.9%. As a result, the area suitable for beje ponds development is ±9,616 ha, or 6.2% of the total area studied.
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Tropical peatlands are one of the largest carbon-storing ecosystems in the world. Draining tropical peatland causes environmental damage including greenhouse gas emissions. Drained peat is highly susceptible to fires that increase carbon emissions into the air. Rewetting is one way to solve the problem because, to achieve a zero or negative carbon balance, the water level should be close to or above the surface to maintain the water saturation of peat. The government of Indonesia has thoughtfully restored the peatland by implementing the 3R approach (rewetting, revegetation, and revitalizing local livelihood). After rewetting, paludiculture (wetland cultivation) is a promising land-use option for peatland. Through paludiculture, the peatland ecosystem will be improved which has already undergone drainage and will re-encourage carbon accumulative in peatland. This paper aims to determine the potential of paludiculture to support climate change adaptation including presenting challenges and opportunities in its implementation. Paludiculture has been shown to reduce greenhouse gas emissions by keeping peat moist. Besides having an ecological function, paludiculture also functions economically because it can be an alternative source of livelihood for people living around peat.
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Tropical peatland in Indonesia experiences massive degradation due to the high pressures of anthropogenic ventures that triggered the disaster, which calls for peatland restoration. This restoration requires comprehensive knowledge in designing and transforming appropriate policy and has become a challenging part of peatland restoration. This research discusses the insights from stakeholders concerning knowledge management to support the policy and strategy of Indonesia’s peatland restoration. The survey was conducted on 72 respondents. Most of the respondents (95.8%) know about the existing tropical peatland in Indonesia. Respondents also elaborated on various sources of peatland knowledge through (1) online scientific search engine; (2) discussion and interview; (3) workshop and conference; (4) observation and experience. We found that 81.9% of respondents have a basic understanding of knowledge management, and 94.4% of respondents agree on the role of social media in knowledge management. Respondents highlighted some points for building knowledge management, including sharing knowledge mechanisms, exploring local knowledge, organizing knowledge, and building an informative platform. Collaboration work is the key in the digital era for this context. Utilizing social media would be an attractive package to shape the policy and strategy in raising public awareness, building networks, and improving sharing knowledge mechanisms.
Article
Wetlands that develop peat are a globally significant pool of soil carbon. While some wetland types such as bogs and fens are well characterized by the consistent development of carbon-rich peat, swamps soils are more variable both in terms of their carbon densities and accretion rates. Subcategorizing swamps by forest type may be a useful way of understanding this variability. Here we provide a case study of carbon accumulation in two distinct forest stands of Greenock Swamp located in the Great Lakes – St Lawrence mixed forest region in Bruce County, Ontario, Canada: Acer-Fraxinus (maple-ash) swamp (i.e., broad-leaf swamp) prevalent across the site, and a Thuja occidentalis (cedar) swamp stand (i.e., needle-leaf swamp). Organic matter and organic carbon contents were analyzed among seven broad-leaf swamp soil cores and one needle-leaf swamp core collected from Greenock Swamp. The broad-leaf swamp cores had peat depths ranging from 18–60 cm with a mean organic matter content of 54% and an organic carbon content of 34% of dry mass. The needle-leaf swamp core had at least 4 m of almost homogeneous peat with a mean organic matter content of 89%. Radiocarbon dating indicates that the broad-leaf swamp accumulates peat episodically, but can contain organic matter thousands of years old; the needle-leaf swamp shows continuous peat accumulation since the Middle Holocene. While broad-leaf swamp soils contain lower carbon stocks than needle-leaf swamp soils, they extend over large areal extents at Greenock Swamp and elsewhere in the temperate zone and contain important pools of recalcitrant organic matter, in some cases thousands of years old. Thus, both swamp types need to be considered to fully represent the carbon pools and potential sink of temperate wetlands.
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The tropical area has a large area of peatland, which is an important ecosystem that is regarded as home by millions of people, plants and animals. However, the dried-up and degraded peatland becomes extremely easy to burn, and in case of fire, it will further release transboundary haze. In order to protect the peatland, an improved tropical peatland fire weather index (FWI) system is proposed by combining the ground water level (GWL) with the drought code (DC). In this paper, LoRa based IoT system for peatland management and detection was deployed in Raja Musa Forest Reserve (RMFR) in Kuala Selangor, Malaysia. Then, feasibility of data collection by the IoT system was verified by comparing the correlation between the data obtained by the IoT system and the data from Malaysian Meteorological Department (METMalaysia). An improved model was proposed to apply the ground water level (GWL) for Fire Weather Index (FWI) formulation in Fire Danger Rating System (FDRS). Specifically, Drought Code (DC) is formulated using GWL, instead of temperature and rain in the existing model. From the GWL aggregated from the IoT system, the parameter is predicted using machine learning based on a neural network. The results show that the data monitored by the IoT system has a high correlation of 0.8 with the data released by METMalaysia, and the Mean Squared Error (MSE) between the predicted and real values of the ground water level of the two sensor nodes deployed through neural network machine learning are 0.43 and 12.7 respectively. This finding reveals the importance and feasibility of the ground water level used in the prediction of the tropical peatland fire weather index system, which can be used to the maximum extent to help predict and reduce the fire risk of tropical peatland.
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Tropical forests are pivotal to global climate and biogeochemical cycles, yet the geographic distribution of nutrient limitation to plants and microbes across the biome is unresolved. One long-standing generalization is that tropical montane forests are nitrogen (N)-limited whereas lowland forests tend to be N-rich. However, empirical tests of this hypothesis have yielded equivocal results. Here we evaluate the topographic signature of the ecosystem-level tropical N cycle by examining climatic and geophysical controls of surface soil N content and stable isotopes (δ¹⁵N) from elevational gradients distributed across tropical mountains globally. We document steep increases in soil N concentration and declining δ¹⁵N with increasing elevation, consistent with decreased microbial N processing and lower gaseous N losses. Temperature explained much of the change in N, with an apparent temperature sensitivity (Q10) of ~1.9. Although montane forests make up 11% of forested tropical land area, we estimate they account for >17% of the global tropical forest soil N pool. Our findings support the existence of widespread microbial N limitation across tropical montane forest ecosystems and high sensitivity to climate warming.
Chapter
Biological carbon sequestration technologies use the ability of living organisms like plants and microorganism to absorb carbon dioxide from atmosphere and store it as carbon in vegetation, soils, woody products and the aquatic environment. These processes play a major role in reducing the anthropogenic emitted greenhouse gas emissions and give therefore, possible mitigation options to diminish global warming and its negative impacts on our planet. The article presents terrestrial and ocean based solutions for carbon sequestration, their global potential as well as co-benefits and the challenges for implementing them.
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Peatlands account for 15 to 30% of the world's soil carbon (C) stock and are important controls over global nitrogen (N) cycles. However, C and N concentrations are known to vary among peatlands contributing to the uncertainty of global C inventories, but there are few global studies that relate peatland classification to peat chemistry. We analyzed 436 peat cores sampled in 24 countries across six continents and measured C, N, and organic matter (OM) content at three depths down to 70 cm. Sites were distinguished between northern (387) and tropical (49) peatlands and assigned to one of six distinct broadly recognized peatland categories that vary primarily along a pH gradient. Peat C and N concentrations, OM content, and C:N ratios differed significantly among peatland categories, but few differences in chemistry with depth were found within each category. Across all peatlands C and N concentrations in the 10-20 cm layer, were 440 ± 85.1 g kg-1 and 13.9 ± 7.4 g kg-1, with an average C:N ratio of 30.1 ± 20.8. Among peatland categories, median C concentrations were highest in bogs, poor fens and tropical swamps (446-532 g kg-1) and lowest in intermediate and extremely rich fens (375-414 g kg-1). The C:OM ratio in peat was similar across most peatland categories, except in deeper samples from ombrotrophic tropical peat swamps that were higher than other peatlands categories. Peat N concentrations and C:N ratios varied approximately two-fold among peatland categories and N concentrations tended to be higher (and C:N lower) in intermediate fens compared with other peatland types. This study reports on a unique data set and demonstrates that differences in peat C and OM concentrations among broadly classified peatland categories are predictable, which can aid future studies that use land cover assessments to refine global peatland C and N stocks.
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In fire emission models, the spatial resolution of both the modelling framework and the satellite data used to quantify burned area can have considerable impact on emission estimates. Consideration of this sensitivity is especially important in areas with heterogeneous land cover and fire regimes and when constraining model output with field measurements. We developed a global fire emissions model with a spatial resolution of 500 m using MODerate resolution Imaging Spectroradiometer (MODIS) data. To accommodate this spatial resolution, our model is based on a simplified version of the Global Fire Emissions Database (GFED) modelling framework. Tree mortality as a result of fire, i.e. fire-related forest loss, was modelled based on the overlap between 30 m forest loss data and MODIS burned area and active fire detections. Using this new 500 m model, we calculated global average carbon emissions from fire of 2.1±0.2 (±1σ interannual variability, IAV) Pg C yr−1 during 2002–2020. Fire-related forest loss accounted for 2.6±0.7 % (uncertainty range =1.9 %–3.3 %) of global burned area and 24±6 % (uncertainty range =16 %–31 %) of emissions, indicating that fuel consumption in forest fires is an order of magnitude higher than the global average. Emissions from the combustion of soil organic carbon (SOC) in the boreal region and tropical peatlands accounted for 13±4 % of global emissions. Our global fire emissions estimate was higher than the 1.5 Pg C yr−1 from GFED4 and similar to 2.1 Pg C yr−1 from GFED4s. Even though GFED4s included more burned area by accounting for small fires undetected by the MODIS burned area mapping algorithm, our emissions were similar to GFED4s due to higher average fuel consumption. The global difference in fuel consumption could mainly be explained by higher SOC emissions from the boreal region as constrained by additional measurements. The higher resolution of the 500 m model also contributed to the difference by improving the simulation of landscape heterogeneity and reducing the scale mismatch in comparing field measurements to model grid cell averages during model calibration. Furthermore, the fire-related forest loss algorithm introduced in our model led to more accurate and widespread estimation of high-fuel-consumption burned area. Recent advances in burned area detection at resolutions of 30 m and finer show a substantial amount of burned area that remains undetected with 500 m sensors, suggesting that global carbon emissions from fire are likely higher than our 500 m estimates. The ability to model fire emissions at 500 m resolution provides a framework for further improvements with the development of new satellite-based estimates of fuels, burned area, and fire behaviour, for use in the next generation of GFED.
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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.
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Information on temporal and spatial variations in soil greenhouse gas (GHG) fluxes from tropical peat forests is essential to predict the influence of climate change and estimate the effects of land use on global warming and the carbon (C) cycle. To obtain such basic information, soil carbon dioxide (CO2) and methane (CH4) fluxes, together with soil physicochemical properties and environmental variables, were measured at three major forest types in the Maludam National Park, Sarawak, Malaysia, for eight years, and their relationships were analyzed. Annual soil CO2 fluxes ranged from 860 to 1450 g C m⁻2 yr⁻1 without overall significant differences between the three forest sites, while soil CH4 fluxes, 1.2–10.8 g C m⁻2 yr⁻1, differed. Differences in GHG fluxes between dry and rainy seasons were not necessarily significant, corresponding to the extent of seasonal variation in groundwater level (GWL). The lack of significant differences in soil CO2 fluxes between the three sites could be attributed to set-off between the negative and positive effects of the decomposability of soil organic matter as estimated by pyrophosphate solubility index (PSI) and GWL. The impact of El-Niño on annual CO2 flux also varied between the sites. The variation in soil CH4 fluxes from the three sites was enhanced by variations in temperature, GWL, PSI, and soil iron (Fe) content. A positive correlation was observed between the annual CH4 flux and GWL at only one site, and the influence of soil properties was more pronounced at the site with the lowest GWL and the highest PSI. Variation in annual CH4 fluxes was controlled more strongly by temperature where GWL was the highest and GWL and plant growth fluctuations were the least. Inter-annual variations in soil CO2 and CH4 fluxes confirmed the importance of long-term monitoring of these at multiple sites supporting different forest types.
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Tropical peatlands play a vital role in the global carbon cycle as large carbon reservoirs and substantial carbon sinks. Indonesia possesses the largest share (65 %) of tropical peat carbon, equal to 57.4 Gt C. Human perturbations such as extensive logging, deforestation and canalization exacerbate water losses, especially during dry seasons, when low precipitation and high evapotranspiration rates combine with the increased drainage to lower groundwater levels. Drying and increasing temperatures of the surface peat exacerbate ignition and wildfire risks within the peat soils. As such, it is critically important to know how groundwater levels in peatlands are changing over space and time. In this study, a multilinear regression model as well as two machine learning algorithms, random forest and extreme gradient boosting, were used to model groundwater level over the study period (2010−12) within a peat dome impacted by drainage canals and multiple wildfires in Central Kalimantan, Indonesia. Although all three models performed well, based on overall fit, spatial modeling of groundwater level results revealed that extreme gradient boosting (R² = 0.998, RMSE = 0.048 m) outperformed random forest (R² = 0.997, RMSE = 0.054 m) and multilinear regression (R² = 0.970, RMSE = 0.221 m) near drainage canals, which are key fire ignition risk locations in the peatlands. Our study also shows that, on average, elevation and precipitation are the most important parameters influencing groundwater level spatiotemporally.
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Climate change has become a global concern. Coastal wetlands play an important role in the global carbon cycle and significantly contribute to the emission and absorption of the greenhouse gases CO2 and CH4. In this study, the temporal and spatial variations of soil CO2 and CH4 emission fluxes, soil total carbon, total organic carbon, and carbon and nitrogen stable isotopes of four vegetation areas (Suaeda salsa, Phragmites australis, Tamarix chinensis, and farmland) and a bare beach in the Yellow River Delta wetland were observed in the spring of 2011–2013. Soil organic carbon δ¹³C ranged from −25.43–-23.69‰ and soil organic carbon content from 0.311 to 1.42%, and the two were significantly negatively correlated, indicating a low decomposition degree of soil organic matter. The soil CO2 emission fluxes in the study period were carbon emissions. In the area with mainly Tamarix chinensis, the 3-year average CO2 emission flux was the highest, in the area with predominantly Phragmites australisthe lowest. The soil CH4 emission flux in the spring of 2011 was a carbon absorption, whereas it was a carbon emission in the spring of 2012 and 2013. Its 3-year average was the highest in the bare beach area and the lowest in the Tamarix ramosissima area. Based on Pearson correlation analysis combined with RDA and multiple linear regression analysis, we found that the main factors affecting soil CO2 and CH4 emission fluxes may be the fast decomposition rate of soil organic matter, the content of soil carbon and organic carbon, and the low degree of soil organic matter decomposition.
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In northern peatlands, near‐saturated surface conditions promote valuable ecosystem services such as carbon storage and drinking water provision. Peat saturated hydraulic conductivity (Ksat) plays an important role in maintaining wet surface conditions by moderating drainage and evapotranspiration. Peat Ksat can exhibit intense spatial variability in three dimensions and can change rapidly in response to disturbance. The development of skillful predictive equations for peat Ksat and other hydraulic properties, akin to mineral soil pedotransfer functions, remains a subject of ongoing research. We report a meta‐analysis of 2,507 northern peat samples, from which we developed linear models that predict peat Ksat from other variables, including depth, dry bulk density, von Post score (degree of humification), and categorical information such as surface microform type and peatland trophic type (e.g., bog and fen). Peat Ksat decreases strongly with increasing depth, dry bulk density, and humification; and increases along the trophic gradient from bog to fen peat. Dry bulk density and humification are particularly important predictors and increase model skill greatly; our best model, which includes these variables, has a cross‐validated r² of 0.75 and little bias. A second model that includes humification but omits dry bulk density, intended for rapid field estimations of Ksat, also performs well (cross‐validated r² = 0.64). Two additional models that omit several predictors perform less well (cross‐validated r² ∼ 0.5), and exhibit greater bias, but allow Ksat to be estimated from less comprehensive data. Our models allow improved estimation of peat Ksat from simpler, cheaper measurements.
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While existing moratoria in Indonesia and Malaysia should preclude continued large-scale expansion of palm oil production into new areas of South-East Asian tropical peatland, existing plantations in the region remain a globally significant source of atmospheric carbon due to drainage driven decomposition of peatland soils. Previous studies have made clear the direct link between drainage depth and peat carbon decomposition and significant reductions in the emission rate of CO2 can be made by raising water tables nearer to the soil surface. However, the impact of such changes on palm fruit yield is not well understood and will be a critical consideration for plantation managers. Here we take advantage of very high frequency, long-term monitoring of canopy-scale carbon exchange at a mature oil palm plantation in Malaysian Borneo to investigate the relationship between drainage level and photosynthetic uptake and consider the confounding effects of light quality and atmospheric vapour pressure deficit. Canopy modelling from our dataset demonstrated that palms were exerting significantly greater stomatal control at deeper water table depths (WTD) and the optimum WTD for photosynthesis was found to be between 0.3 and 0.4 m below the soil surface. Raising WTD to this level, from the industry typical drainage level of 0.6 m, could increase photosynthetic uptake by 3.6 % and reduce soil surface emission of CO2 by 11 %. Our study site further showed that despite being poorly drained compared to other planting blocks at the same plantation, monthly fruit bunch yield was, on average, 14 % greater. While these results are encouraging, and at least suggest that raising WTD closer to the soil surface to reduce emissions is unlikely to produce significant yield penalties, our results are limited to a single study site and more work is urgently needed to confirm these results at other plantations.
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Peatlands are carbon-rich ecosystems that comprise the largest terrestrial carbon store. Peatland preservation has been acknowledged on the global scale as a key nature-based component in addressing climate change. Despite their importance, there is no globally recognised definitions for peat or peatland, which influences efforts in quantifying global peat carbon stocks. We present a critical review on peatland definitions, including peat nomenclature and changing criteria for peatland classification through time. We focus on two important criteria: the minimum depth of the surface organic layer and the minimum percentage of organic carbon. We highlight the disparity between definitions, peatland nomenclature and peatland classifications. It is challenging to determine whether one definition should take precedence over another, even when considering the most common criteria. We propose that future peatland definitions focus on carbon storage and potential greenhouse gas emissions. This involves four physical and chemical characteristics of the peatland deposit: (1) Peatland extent, (2) peat thickness, (3) peat carbon content and (4) peat bulk density (volumetric carbon content). The growth dynamics and carbon flux of the peatland deposit should also become a routine part of inventories. In future, international technical agencies and experts can advise on the standardisation of concept definitions and methods, these must focus on the preservation of peatlands from the perspective of climate science.
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The monitoring of flood and wetland dynamics at global scale is hampered by several limitations, including a reduced data availability in tropical areas due to the presence of clouds affecting visible and infrared imagery, or low spatial and/or temporal resolutions affecting passive and active microwave Earth Observation (EO) data. As a consequence, surface water extent estimates and their temporal variations remain challenging especially in equatorial river basins. Global Navigation Satellite System Reflectometry (GNSS-R) L-band signals recorded onboard Cyclone GNSS (CYGNSS) mission, composed of 8 Low Elevation Orbit (LEO) satellites, provide information on surface properties at high temporal resolution from 2017 up to now. CYGNSS bistatic observations were analyzed for detecting permanent water and seasonal floodplains over the full coverage of the mission, from 40°S to 40°N. We computed CYGNSS reflectivity associated to the coherent component of the received power, that was gridded at 0.1° spatial resolution with a 7-day time sampling afterwards. Several statistical metrics were derived from CYGNSS reflectivity, including the weighted mean and standard deviation, the median and the 90th percentile (respectively Γmean,Γstd,Γmedian and Γ90%) in each pixel. These parameters were clustered using the K-means algorithm with an implementation of the Dynamic Time Warping (DTW) similarity measure. They were compared to static inundation maps, and to dynamic estimations of surface water extent both at the global and regional scales, using the Global Inundation Extent from Multi-Satellites (GIEMS) and MODIS-based products. The difference between Γ90% and Γmedian shows the best sensitivity to the presence of water. The river streams and lakes are correctly detected, and a strong seasonality is identified in CYGNSS reflectivity over the largest floodplains, with the exception of the Cuvette Centrale of Congo which is covered by dense vegetation. This seasonal reflectivity signal correlates well with inundation maps: Pearson’s correlation coefficient between Γmedian and surface water extent from both GIEMS and MODIS is over 0.8 in the largest floodplains. The spatial patterns of reflectivity are consistent with static inundation maps: at the time of maximum flooding extent, a spatial correlation coefficient around 0.75 with Γmedian is obtained for several basins. We also evaluated the dependence of CYGNSS-derived clusters and reflectivity on the dominant land cover type and on the density of Above Groud Biomass (AGB) in the pixel. On the one hand, misclassifications of flooded pixels were observed over vegetated regions, probably due to uncertainties related to the attenuation by the vegetation in both CYGNSS and reference datasets. On the other hand, flooded pixels with a mean AGB up to ∼300 Mg/ha were correctly detected with the clustering. High reflectivity values are also observed over rocky soils in arid regions and create false alarms. Finally, strong winds on large lakes cause surface roughness, and lower reflectivity values are observed in this case which weaken the detection of open water. While these constraints are to be taken in account and corrected in a future model, a pan-tropical mapping of surface water extent dynamics using CYGNSS can be envisaged.
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Presentation of three peatlands in Slowinski National Park (N Poland) targeted by LIFE project "Reduction of CO2 emissions by reducing degraded peatlands in Northern European Lowland". Results of research on peatlands hydrology, structure (stratygraphy), vegetation. Implemented restoration measures as well as first monitoring results.
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Enhanced weathering is a carbon dioxide (CO2) removal strategy that accelerates the CO2 uptake and removal from the atmosphere by weathering via the dispersion of rock powder. Warm and humid conditions enhance weathering and among the suggested target areas for enhanced weathering are tropical peatlands. However, the effect of enhanced weathering on peatland carbon stocks is poorly understood. Here, we present estimates for the response of CO2 emissions from tropical peat soils, rivers and coastal waters to changing soil acidity induced by enhanced weathering application. We estimate that the potential carbon uptake associated with enhanced weathering is reduced by 18–60% by land-based re-emission of CO2 and is potentially offset completely by emissions from coastal waters. Our findings suggest that in contrast to the desired impact, enhanced weathering may destabilize the natural carbon cycle in tropical peatlands that act as important carbon sinks and protect against coastal erosion. Enhanced weathering in tropical peatlands may be an ineffective carbon dioxide removal strategy due to pH-induced increases in soil carbon leaching which lead to increased re-emission of carbon, according to model calculations constrained by observations from Sumatra, Indonesia.
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Underwater light availability is a crucial aspect for the ecological functioning of shallow water bodies. Light extinction from terrestrial inputs is a growing threat to these coastal habitats. The blended quasi-analytical algorithm (QAA) was extended for the derivation of colored dissolved organic matter (CDOM) absorption coefficient along with other inherent optical properties (IOPs) from satellite observations for Southeast Asian waters. The contribution of these IOPs to diffuse attenuation of light (K d ) and penetration depth (Z d ) was investigated. A vulnerability assessment was performed to identify locations potentially threatened by poor light quality in Southeast Asian waters. Advection of peatland-influenced Sumatran coastal waters rich in organic matter (a g (400nm): 1.0-2.0m ⁻¹ ) and sediments (b bp (400nm): 0.5-1m ⁻¹ ) drive the spatial heterogeneity of Sunda shelf seawater. Photic zone depth, Z d (490nm), is year-round restricted to ≤5m for critically vulnerable Sumatran coastal waters (vulnerability index, VI>0.8). This critically vulnerable state is further extended towards the southern Malacca Strait, influencing the eastern Singapore Strait from June to September. The areas harbouring marine ecosystems in the shelf waters attain a higher threshold (VI=0.6-0.8), constraining the photosynthesis to depths ≤10m. A transformation of central Malacca Strait from not vulnerable (VI<0.2) to highly vulnerable (VI=0.6-0.8) state from June to September indicates poor light conditions. Further increases in CDOM and sediment inputs into these water columns, therefore, constitute a clear risk of reducing light availability, which may have damaging effects on the functioning of coastal habitats. This study underscores the need for a complete ecological risk assessment for Southeast Asia to aid in the effective management of marine ecosystems.
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Mangroves are critical to maintaining human well-being and global biodiversity. Eastern and western African shores present major environmental contrasts that reflect on mangrove forests’ structure and the ecosystem services they provide to human communities. This study compares the mangrove forest structure and condition, ecosystem services, and uses of resources in Maputo Bay (Mozambique in eastern Africa) and Príncipe Island (São Tomé and Príncipe in western Africa). Five mangrove species were identified in Maputo Bay, Avicennia marina, Bruguiera gymnorhiza, Ceriops tagal, Rhizophora mucronata, and Xylocarpus granatum, and the importance value index was higher for A. marina. Mangroves in Príncipe were exclusively dominated by Rhizophora harrisonii. In Maputo Bay, a weak regeneration characterized by a low quantity of seedlings was observed, although in Príncipe the sites were characterized by a low regeneration rate but well-established forests. The comparison of the mangrove structure between Maputo Bay and Príncipe Island presented statistically significant differences for mean DBH and height, whereas the trees in Príncipe presented higher values for both parameters. Strong human disturbance (through cutting) was identified in almost all sites in Maputo Bay but was rarely observed on Príncipe Island. In Maputo Bay, more than 90% of the coastal human community is involved in activities related to the surrounding mangroves, with a diversified exploitation of forest resources. On Príncipe Island, the exploitation of mangroves targets only tannin from the mangrove bark to dye fishing nets and small boats. The economic value of mangroves in Maputo Bay has subsistence and commercial importance, in contrast to Príncipe, which revealed no major economic value to the community.
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Indonesian peatlands and their large carbon stores are under threat from recurrent large-scale fires driven by anthropogenic ecosystem degradation. Although the key drivers of peatland fires are known, a holistic methodology for assessing the potential of fire mitigation strategies is lacking. Here, we use machine learning (convolutional neural network) to develop a model capable of recreating historic fire observations based on pre-fire season parameters. Using this model, we test multiple land management and peatland restoration scenarios and quantify the associated potential for fire reduction. We estimate that converting heavily degraded swamp shrubland areas to swamp forest or plantations can reduce fires occurrence by approximately 40% or 55%, respectively. Blocking all but major canals to restore these degraded areas to swamp forest may reduce fire occurrence by 70%. Our findings suggest that effective land management strategies can influence fire regimes and substantially reduce carbon emissions associated with peatland fires, in addition to enabling sustainable management of these important ecosystems.
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Smoke aerosol emissions from Indonesian fires frequently cause adverse environmental consequences across southeast Asia. Satellite observations provide us with a great opportunity to monitor such emissions at large scales. However, existing satellite-based estimates of Indonesian fire emissions vary considerably in magnitude, differing by a factor of four. Here, we aim to improve Indonesian fire emissions estimates through improved calculations of fire radiative energy (FRE: time-integrated fire radiative power (FRP)) and smoke aerosol emission coefficients (Ce) using multiple new-generation satellite observations. Specifically, peatland and non-peatland Ce values were derived from FRP and emission rates of smoke aerosols based on Visible Infrared Imaging Radiometer Suite (VIIRS) active fire and aerosol products. FRE was calculated from the diurnal FRP cycle that was reconstructed by fusing cloud-corrected FRP retrievals from the high temporal-resolution Himawari-8 Advanced Himawari Imager (AHI) with those from high spatial-resolution VIIRS. Then, fuel type-specific Ce values and fused AHI-VIIRS FRE were used to produce hourly and daily fire emission data from 2015 to 2020 across Indonesia. To evaluate AHI-VIIRS estimates, we generated a reference dataset of total particulate matter (TPM) by computing Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol observation differences from successive Terra and Aqua satellites overpasses over a set of manually-selected smoke plumes. AHI-VIIRS-based fire emissions correlated significantly with the MODIS reference data (r = 0.84; p < 0.001). The interannual time series analysis of AHI-VIIRS emissions showed extreme variability (~26 fold), with the greatest amount in 2015 (6.09 Tg) and the least in 2020 (0.23 Tg), during the study period. Mean annual fire emissions distributed across Indonesia's islands were primarily from Kalimantan (43.8%) and Sumatra (41.7%), followed by Sulawesi (5.6%), Java (4.5%), and Papua (4.4%). Additionally, contributions of Indonesian fire emissions from peatland, forest, cropland, and savanna/grassland fuel types were 51.4%, 37.8%, 7.0%, and 3.8%, respectively, during the fire season of the strong 2015 El Niño event. The analysis suggests that the majority of Indonesian fire emissions are very likely associated with large-scale land use conversion from peatland to agriculture, as well as prolonged droughts induced by El Niño events.
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The soil is important in sequestering atmospheric CO2 and in emitting trace gases (e.g. CO2, CH4 and N2O) that are radiatively active and enhance the ‘greenhouse’ effect. Land use changes and predicted global warming, through their effects on net primary productivity, the plant community and soil conditions, may have important effects on the size of the organic matter pool in the soil and directly affect the atmospheric concentration of these trace gases. A discrepancy of approximately 350 × 1015 g (or Pg) of C in two recent estimates of soil carbon reserves worldwide is evaluated using the geo-referenced database developed for the World Inventory of Soil Emission Potentials (WISE) project. This database holds 4353 soil profiles distributed globally which are considered to represent the soil units shown on a 1/2° latitude by 1/2° longitude version of the corrected and digitized 1:5 M FAO–UNESCO Soil Map of the World. Total soil carbon pools for the entire land area of the world, excluding carbon held in the litter layer and charcoal, amounts to 2157–2293 Pg of C in the upper 100 cm. Soil organic carbon is estimated to be 684–724 Pg of C in the upper 30 cm, 1462–1548 Pg of C in the upper 100 cm, and 2376–2456 Pg of C in the upper 200 cm. Although deforestation, changes in land use and predicted climate change can alter the amount of organic carbon held in the superficial soil layers rapidly, this is less so for the soil carbonate carbon. An estimated 695–748 Pg of carbonate-C is held in the upper 100 cm of the world's soils. Mean C: N ratios of soil organic matter range from 9.9 for arid Yermosols to 25.8 for Histosols. Global amounts of soil nitrogen are estimated to be 133–140 Pg of N for the upper 100 cm. Possible changes in soil organic carbon and nitrogen dynamics caused by increased concentrations of atmospheric CO2 and the predicted associated rise in temperature are discussed.
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Carbon ( C) in tropical peatlands over Southeast Asia and Amazonia, if released to the atmosphere, can substantially increase the growth rate of atmospheric carbon dioxide. Over Southeast Asia, where the most extensive tropical peatlands in the world occur, 11 climate models for the IPCC Fourth Assessment show an overall decrease of rainfall in future dry seasons. Over Amazonia, future rainfall changes in dry seasons are highly uncertain; five models predict increased rainfall, and the remaining models predict the opposite. We have further examined the UKMO-HadCM3, GISS-ER, and GFDL-CM2.1 models. Over Southeast Asia, all three models predict similar decreases of rainfall and evaporative fraction, implying an increase of water table depth and surface dryness during the dry season south of the equator. Such changes would potentially switch peat ecosystems from acting as C sinks to C sources. Over Amazonia, the two models with the best simulations of current rainfall produce conflicting results for the future of peat stability.
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The extent and function of coastal mangrove ecosystems are likely to be influenced by future changes in sea level. Multiple proxies of past mangrove ecosystems preserved in a 780 cm long peat core (TCC2) taken from Twin Cays, Belize, record palaeoecological changes since ~8000 cal. yr BP. The proxies included pollen and the stable-isotope (C, N and O) compositions of mangrove leaf fragments. Rhizophora mangle (red mangrove) has been dominant at this site on Twin Cays for over ~8000 years. Variations in δ13 C and δ15N suggest past changes in stand structure between dwarf, transition and tall R. mangle through the Holocene. Marked changes in the δ18O (up to ~4‰) of mangrove leaf fragments throughout TCC2 most likely record variations in the proportion of seawater versus precipitation taken up by past mangroves, reflecting the degree of inundation of the site with seawater resulting from changes in the rate of Holocene sea-level rise. Notably, a decline in peat accumulation rate at ~7200 cal. yr BP correlates with a decrease in the rate of rise in sea level. This was not accompanied by a marked change in the pollen assemblages. However, changes in assemblage composition began to occur ~6300 cal. yr BP, with an increase in Myrsine-type and Avicennia germinans (black mangrove) pollen. An increase in the δ18O between 6100 and 5300 cal. yr BP, which correlates with other records from Central America, indicates a significant increase in the rate of rise in sea level.
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Estimates of geographically referenced carbon densities and pools in forest soils and vegetation of tropical Asia were modeled using a geographic information system. Spatial data bases of climatic, edaphic, and geomorphologic indices, and vegetation were first used to estimate the potential carbon densities (without human impacts) in above‐ and below‐ground biomass of forests in 1980. The resulting map was then modified to actual carbon density estimates as a function of population density and three climatic regimes. Soil organic carbon estimates were generated by calculating mean carbon densities, to 100 cm depth, from pedon data for tropical forests, stratified by soil texture classes and climatic regimes. The means for each class were assigned to a texture/climate map for all of tropical Asia. The average carbon density for the tropical forests of Asia was 255 Mg ha in potential biomass, 144 Mg ha in actual biomass and 148 Mg ha in soils, which correspond to total carbon estimates of 74, 42, and 43 Pg, respectively. Three out of the 14 countries considered (Indonesia, India, and Myanmar) accounted for about 70% of the total carbon pools in tropical Asian forests. Carbon densities and pools in vegetation and soil varied widely by ecofloristic zone and country.
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Boreal and subarctic peatlands comprise a carbon pool of 455 Pg that has accumulated during the postglacial period at an average net rate of 0.096 Pg/yr (1 Pg = 10(15) g). Using Clymo's (1984) model, the current rate is estimated at 0.076 Pg/yr. Long-term drainage of these peatlands is estimated to be causing the oxidation to CO2 of a little more than 0.0085 Pg/yr, with combustion of fuel peat adding almost-equal-to 0.026 Pg/yr. Emissions of CH4 are estimated to release almost-equal-to 0.046 Pg of carbon annually. Uncertainties beset estimates of both stocks and fluxes, particularly with regard to Soviet peatlands. The influence of water table alterations upon fluxes of both CO2 and CH4 is in great need of investigation over a wide range of peatland environments, especially in regions where permafrost melting, thermokarst erosion, and the development of thaw lakes are likely results of climatic warming. The role of fire in the carbon cycle of peatlands also deserves increased attention. Finally, satellite-monitoring of the abundance of open water in the peatlands of the West Siberian Plain and the Hudson/James Bay Lowland is suggested as a likely method of detecting early effects of climatic warming upon boreal and subarctic peatlands.
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EVIDENCE from ice cores1 indicates that concentrations of atmospheric carbon dioxide were lower by about 75 p.p.m. during the Last Glacial Maximum (LGM; ~18,000 years ago) than during the present interglacial (10,000 years ago to the present). The causes of such large changes in atmospheric CO2 remain uncertain. Using a climate model, Prentice and Fung2 have estimated that there was approximately the same amount of carbon in vegetation and soils during the LGM as there was during the present (pre-industrial) interglacial. In contrast, we present here results based on palynological, pedological and sedimentological evidence which indicate that in fact the amount of carbon in vegetation, soils and peatlands may have been smaller during the LGM by ~1.3x 1012 tonnes. Thus, organic carbon in vegetation and soils has more than doubled (from 0.96 to 2.3 x 1012 tonnes) since the LGM. Oceanic CO2 reservoirs seem to be the only possible source of this large quantity of carbon that has entered the terrestrial biosphere since the LGM (in addition to that which has entered the atmosphere to give the higher interglacial CO2 levels).
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Peatlands are terrestrial wetland ecosystems in which the production of organic matter exceeds its decomposition and a net accumulation results. Several factors influence peat formation and preservation, including a positive climatic moisture balance (precipitation minus evaporation), high-relative humidity, topographic and geological conditions that favor water retention, and low substrate pH and nutrient availability. The majority of the world's peatlands occur in boreal and temperate zones where they have formed under high-precipitation, low-temperature climatic regimes. In the humid tropics, however, regional environmental and topographic conditions have enabled peat to form under a high-precipitation, high-temperature regime and, as a consequence, extensive peatlands occur in Southeast Asia, mainland East Asia, the Caribbean and Central America, South America and southern Africa. Most of these are located at low altitudes where rain forest vegetation grows on a thick mass of organic matter accumulated over thousands or tens of thousands of years, to form deposits up to 20m thick.
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SUMMARY The approximately 20% of CO2 emissions that are lost as a result of forest and peatland degradation have been neglected in the purview of climate change mechanisms. This paper gives an estimate of CO2 emissions from different land use systems and the corresponding opportunity costs for avoided deforestation of Indonesian peatlands. Increase in CO2 emission from peatland is usually preceded by deforestation and peatland fires. Subsequent land management systems determine the rate of emission. Oil palm requires drainage to about one metre depth and this leads to below ground CO2 emission of about 91 t ha-1 yr-1. Some practices, for example, the 'sonor' system, which involve burning of surface peat for rice cultivation can lead to CO2 emissions as high that those from oil palm plantations. Several other farming systems tolerate shallow or no drainage and thus have lower emissions. In preparation for the Climate Change Conference of Parties in Bali in December 2007 an overview has been made of the 'opportunity costs' of avoided emissions from peatland degradation. The 'opportunity cost' of avoided emissions from peatland degradation is about $0.08 t-1 CO2e in the sonor rice system but as high as $3.4 t-1 CO2e in oil palm plantation. These are below the emission reduction credits range of $4 to $18.
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Recent field and laboratory studies have established the presence of numerous extensive peat deposits in Costa Rica. Three of these were selected for initial investigation: (1) the cloud-forest histosols of the Talamanca Mountain Range; (2) the Rio Medio Queso flood plain deposits near the northern Costa Rican border; and (3) a tropical jungle swamp deposit on the northeastern coastal plain. In the Talamanca area, 29 samples were collected from eight sites. Due to the high moisture and cool temperatures of the cloud forest, the peats in this area form blanket-like deposits (generally 150 km/sup 2/). These peats are all highly decomposed (avg. 28% fiber), high in ash (avg. 21%), and extensively bioturbated. Relative to all other sites visited, these peats are lowest in moisture (avg. 84%), pH (avg. 4.4), fixed carbon (avg. 23%), and sulfur (avg. 0.2%). However, they have the highest bulk densities (avg. 0.22 g/cc), volatile matter contents (avg. 55%), and nitrogen. Their heating value averaged 7700 BTUs/lb., dry. In the Rio Medio Queso area, 28 samples were collected, representing one transect of the 70 km/sup 2/ flood plain. The peats here occurred in several layers (each
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Present tropical peat deposits are the outcome of net carbon removal from the atmosphere and form one of the largest terrestrial organic carbon stores on the Earth. Reclamation of pristine tropical peatland areas in Southeast Asia increased strikingly during the last half of the 20th century. Drainage due to land-use change is one of the main driving factors accelerating carbon loss from the ecosystem. Dams were built in drainage-affected peatland area canals in Central Kalimantan, Indonesia, in order to evaluate major patterns in gaseous carbon dioxide and methane fluxes and in peat hydrology immediately before and after hydrologic restoration. The sites included peat swamp forest and deforested burned area, both affected by drainage for nearly 10 years. Higher annual minimum soil water table levels prevailed on both sites after restoration; the deforested site water table level prevailed considerably longer near the peat surface, and the forest water table level remained for a longer period in the topmost 30 cm peat profile after restoration. Forest soil gas fluxes were clearly higher in comparison to the deforested area. Cumulative forest floor CO2 emissions (7305-7444 g m-2 yr -1; 166.0-169.2 mol CO2 m-2 yr-1) and the deforested site CO2 emissions (2781-2608 g m -2-yr-1; 63.2-59.3 mol CO2-m -2-yr-1) did not markedly reflect the notably differing hydrological conditions the year before and after restoration. The forest floor was a weak CH4 sink (-0.208 to -0.368 g m-2 yr -1; -13.0 to -22.9 mmol CH4 m-2 yr -1) and the deforested site a comparable CH4 source (0.197-0.275 g m2-yr-1; 12.3-17.1 mmol CH4 m-2 yr-1) in the study period. In general, higher soil water table levels had a relatively small effect on the annual CH4 emission budgets. In the two site types the gas flux response into hydrological conditions in degraded tropical peat can be attributed to differing CO 2 and CH4 dynamics, peat physical characteristics, and vegetation.
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