Impact of forest plantation on methane emissions from tropical peatland

Tropical peatlands are a known source of methane (CH4) to the atmosphere, but their contribution to atmospheric CH4 is poorly constrained. Since the 1980s, extensive areas of the peatlands in Southeast Asia have experienced land‐cover change to smallholder agriculture and forest plantations. This land‐cover change generally involves lowering of groundwater level (GWL), as well as modification of vegetation type, both of which potentially influence CH4 emissions. We measured CH4 exchanges at the landscape scale using eddy covariance towers over two land‐cover types in tropical peatland in Sumatra, Indonesia: (a) a natural forest and (b) an Acacia crassicarpa plantation. Annual CH4 exchanges over the natural forest (9.1 ± 0.9 g CH4 m−2 year−1) were around twice as high as those of the Acacia plantation (4.7 ± 1.5 g CH4 m−2 year−1). Results highlight that tropical peatlands are significant CH4 sources, and probably have a greater impact on global atmospheric CH4 concentrations than previously thought. Observations showed a clear diurnal variation in CH4 exchange over the natural forest where the GWL was higher than 40 cm below the ground surface. The diurnal variation in CH4 exchanges was strongly correlated with associated changes in the canopy conductance to water vapor, photosynthetic photon flux density, vapor pressure deficit, and air temperature. The absence of a comparable diurnal pattern in CH4 exchange over the Acacia plantation may be the result of the GWL being consistently below the root zone. Our results, which are among the first eddy covariance CH4 exchange data reported for any tropical peatland, should help to reduce the uncertainty in the estimation of CH4 emissions from a globally important ecosystem, provide a more complete estimate of the impact of land‐cover change on tropical peat, and develop science‐based peatland management practices that help to minimize greenhouse gas emissions

Long-term trajectory and temporal dynamics of tropical peat subsidence in relation to plantation management and climate

Disentangling land-use and climatic influences on peat subsidence, and establishing the long-term trajectory of subsidence, are necessary to determine the future economic and environmental sustainability of managed peatland landscapes. While many peatlands in temperate regions such as Europe have been drained for centuries, those of Southeast Asia have mostly been drained for agriculture and forestry practices within the last 30 years. These areas are subsiding rapidly, but few long-term subsidence records exist, and it is unclear whether currently high subsidence rates will be maintained in future. Furthermore, large-scale climate fluctuations associated with the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) exert a strong year-to-year influence on rainfall rates, affecting water table depth dynamics in both managed and intact peatlands. In this study, we analysed data collected over more than a decade of subsidence measurements from over 400 plantation and forest plots in Sumatra, Indonesia, including a unique set of 62 sites that have been continuously monitored since 2007. We show that spatial and temporal variations in subsidence rates are primarily determined by water table depth. We also find evidence of declining subsidence rates as a function of time since initial drainage, consistent with previous instrumental records from high-latitude peatlands and recent satellite data from tropical peatlands. Subsidence rates over the study period were strongly affected by the large ENSO/IOD-linked drought event in 2015–16, which caused an acceleration of subsidence across all sites. In plantation areas, we estimate that this climate perturbation caused around 14 % of subsidence observed over a twelve year period. At interior forest sites this rose to 32 %, and we found little evidence of ecosystem recovery to the end of 2018. This raises the possibility that repeated extreme droughts in the region could lead to long-term degradation of peat swamp forest ecosystems

Studi Efektivitas Perbaikan Struktur Tanah melalui Bioclogging dan Biocementation Menggunakan Biopolimer Eksopolisakarida dengan Pemanfaatan Limbah Cair Tahu sebagai Media Pertumbuhan,

Struktur tanah memiliki keterkaitan yang sangat erat dengan kestabilan tanah. Dalam beberapa kasus, rendahnya kestabilan tanah dapat mengarah pada kegagalan struktur dan bahaya tanah longsor. Upaya perbaikan struktur tanah dengan metode biogrouting, yaitu dengan penambahan bakteri penghasil eksopolisakarida pada tanah mulai banyak diteliti. Pada umumnya proses ini melibatkan bahan kimia sebagai media pertumbuhan bakteri sehingga meningkatkan biaya yang dibutuhkan. Untuk menyelediki tentang pemanfaatan limbah cair tahu sebagai media pertumbuhan bakteri dalam upaya perbaikan struktur tanah, maka dilakukan penelitian dengan menginokulasikan lima jenis bakteri non-patogenik (Agrobacterium tumefaciens, Bacillus subtilis, Lactobacillus sakei, Nitrobacter sp., dan Pseudomonas sp.) ke dalam sampel tanah. Sebagai perbandingan digunakan media pertumbuhan kimia dan sampel tanah asli sebagai kontrol. Setelah 15 hari dan 30 hari pasca inokulasi bakteri ke dalam sampel tanah, dilakukan pengujian constant head, pengujian direct shear, dan pengujian SEM. Berdasarkan pengujian constant head didapatkan sampel tanah dengan inokulasi bakteri Agrobacterium tumefaciens pada media limbah cair tahu memiliki nilai permeabilitas terendah dengan reduksi sebesar 53,62% terhadap sampel tanah kontrol pasca inokulasi selama 30 hari. Berdasarkan pegujian direct shear didapatkan sampel tanah dengan inokulasi bakteri Lactobacillus sakei pada media pertumbuhan limbah cair tahu memiliki nilai kuat geser tertinggi dengan prosentase kenaikan sebesar 102,74% terhadap sampel tanah kontrol pasca inokulasi 30 hari. Berdasarkan hasil pengujian SEM dapat diketahui bahwa pada sampel tanah yang telah diinokulasikan dengan bakteri terbentuk eksopolisakarida pada partikel tanah sehingga dapat mereduksi nilai permeabilitas tanah dan meningkatkan nilai kuat geser tanah. Berdasarkan hasil tersebut dapat disimpulkan bahwa limbah cair tahu efektif untuk digunakan sebagai media pertumbuhan bakteri dalam proses biogrouting

Fire frequency, intensity, and burn severity in Kalimantan’s threatened Peatland areas over two Decades

Kalimantan, the Indonesian portion of the Island of Borneo, has an estimated 45,000 km2 of tropical peatland and represents one of the largest stocks of tropical peat carbon. However, over the last three decades, the peatlands of Indonesia, and Kalimantan in particular, have been heavily degraded or destroyed by drainage of peatland swamps, deforestation, land cover change for agriculture, and intentional burning. Many studies have examined degradation of peat forests and the associated frequency of fires, often focusing on specific regions of Kalimantan over limited periods. Here, we present our results of a spatially comprehensive, long-term analysis of peatland fires in Kalimantan over more than two decades from early 2001 to the end of 2021. We examined the effects of changing climate conditions, land cover change, and the regulatory framework on the total burned area and frequency and severity of peatland fires over a 21-year period by combining extensive datasets of medium-resolution and high-resolution satellite imagery. Moreover, surface fire intensity was modeled for four dominant land use/land cover types to determine how land use change alters fire behavior. Our results confirm a consistent and strong spatiotemporal correlation between hydro-climatological drivers associated with El Niño conditions on peatland fire frequencies and burned peatland area. Changes in the number of fires and burn severity are visible over time and are caused by a combination of large-scale meteorological patterns and changing regulations. A significant relative increase of the “high” and “very high” severity across all peatland fires in Kalimantan was found for the latest period from 2015 through 2021 by 12.1 and 13.4%, compared to the two previous 7-year periods from 2001 to 2007 period and from 2008 to 2014, respectively, whereas the total peatland area burned decreased in 2015 to 2021 by 28.7% on average compared to the previous periods. The results underline the importance of a comprehensive approach considering physical aspects of overarching climate conditions while improving political and regulatory frameworks to mitigate the negative effects of burning tropical peatlands

Natural climate solutions in Indonesia: wetlands are the key to achieve Indonesia’s national climate commitment

Indonesia offers a dramatic opportunity to contribute to tackling climate change by deploying natural climate solutions (NCS), increasing carbon sequestration and storage through the protection, improved management, and restoration of drylands, peatlands, and mangrove ecosystems. Here, we estimate Indonesia’s NCS mitigation opportunity for the first time using national datasets. We calculated the maximum NCS mitigation potential extent using datasets of annual national land cover, peat soil, and critical lands. We collated a national emissions factor database for each pathway, calculated from a meta-analysis, recent publications from our team, and available literature. The maximum NCS mitigation potential in 2030 is 1.3 ± 0.04 GtCO _2 e yr ^−1 , based on the historical baseline period from 2009–2019. This maximum NCS potential is double Indonesia’s nationally determined contribution (NDC) target from the forestry and other land use sector. Of this potential opportunity, 77% comes from wetland ecosystems. Peatlands have the largest NCS mitigation potential (960 ± 15.4 MtCO _2 e yr ^−1 or 71.5 MgCO _2 e ha ^−1 yr ^−1 ) among all other ecosystems. Mangroves provide a smaller total potential (41.1 ± 1.4 MtCO _2 e yr ^−1 ) but have a much higher mitigation density (12.2 MgCO _2 e ha ^−1 yr ^−1 ) compared to dryland ecosystems (2.9 MgCO _2 e ha ^−1 yr ^−1 ). Therefore, protecting, managing, and restoring Indonesia’s wetlands is key to achieving the country’s emissions reduction target by 2030. The results of this study can be used to inform conservation programs and national climate policy to prioritize wetlands and other land sector initiatives to fulfill Indonesia’s NDC by 2030, while simultaneously providing additional co-benefits and contributing to COVID-19 recovery and economic sustainability

Conservation slows down emission increase from a tropical peatland in Indonesia

Tropical peatlands are threatened by climate change and land-use changes, but there remain substantial uncertainties about their present and future role in the global carbon cycle due to limited measurements. Here, we present measurements of carbon dioxide and methane emissions between mid-2017 and mid-2020 as well as nitrous oxide emissions between 2019 and 2020 at two contrasting sites at a coastal peatland in Sumatra, Indonesia. We find that greenhouse-gas emissions from intact peatland increased substantially due to an extreme drought caused by a positive Indian Ocean Dipole phase combined with El Niño. The emission in the degraded site was two times greater than that at the intact site. The smaller emission from the intact peatland suggests that protecting the remaining intact tropical peatlands from degradation offers important climate benefits, avoiding greenhouse-gas emissions of 24 ± 5 tCO2e ha−1 yr−1 (average ± standard deviation) at our study site in Indonesia