Using ‘higher-tier’ emission factors in National Greenhouse Gas Inventories is essential to improve quality and accuracy when reporting carbon emissions and removals. Here we systematically reviewed 736 data across 249 sites (published 2003–2020) to derive emission factors associated with land-use change in Indonesian mangroves blue carbon ecosystems. Four management regimes—aquaculture, degraded mangrove, regenerated mangrove and undisturbed mangrove—gave mean total ecosystem carbon stocks of 579, 717, 890, and 1061 Mg C ha−1 respectively. The largest biomass carbon stocks were found in undisturbed mangrove; followed by regenerated mangrove, degraded mangrove, and aquaculture. Top 100-cm soil carbon stocks were similar across regimes, ranging between 216 and 296 Mg C ha−1. Carbon stocks between 0 and 300 cm varied significantly; the highest values were found in undisturbed mangrove (916 Mg C ha−1), followed by regenerated mangrove (803 Mg C ha−1), degraded mangrove 666 Mg C ha−1), and aquaculture (562 Mg C ha−1). Using deep layer (e.g., 300 cm) soil carbon stocks would compensate for the underestimation of surface soil carbon removed from areas where aquaculture is widely practised. From a project perspective, deep layer data could secure permanence or buffer potential leakages. From a national GHG accounting perspective, it also provides a safeguard in the MRV system.
Tag: carbon sinks
Modeling the Spatial Distribution of Soil Organic Carbon and Carbon Stocks in the Casanare Flooded Savannas of the Colombian Llanos
Flooded savannas are valuable and extensive ecosystems in South America, but not widely studied. In this study, we quantify the spatial distribution of soil organic carbon (SOC) content and stocks in the Casanare flooded savannas. We sampled 80 sites at two soil-depth intervals (0-10 and 10-30 cm), where SOC values ranged from 0.41% in the surface and 0.23% in the sub-surface of drier soils to over 14.50% and 7.51%, in soils that experienced seasonal flooding. Spatial predictions of SOC were done through two digital soil mapping (DSM) approaches: Expert-Knowledge (EK) and Random-Forest (RF). Although both approaches performed well, EK was slightly superior at predicting SOC. Covariates derived from vegetation cover, topography, and soil properties were identified as key drivers in controlling its distribution. Total SOC stocks were 55.07 Mt with a mean density of 83.1±24.3 t·ha-1 in the first 30 cm of soil, with 12.3% of this located in areas that experience long periods of flooding (semi-seasonal savannas) , which represented only 7.9% of the study area (664,752 ha). Although the study area represents only 15% of the total area of the Casanare department, the intensive pressure of human development could result in the reduction of its SOC stocks and the release of important amounts of greenhouse gases into the atmosphere. At regional level, the impact of a large-scale land use conversions of the flooded Llanos del Orinoco ecosystem area (15 Mha) could transform this area in a future source of important global emissions if correct decisions are not taken regarding the land management of the region.
Soils as Carbon Stores and Sinks: Expectations, Patterns, Processes, and Prospects of Transitions
The few percent of soil organic carbon (SOC) among mineral components form the interface of climate, plant growth, soil biological processes, physical transport infrastructure, and chemical transformations. We explore maps, models, myths, motivation, means of implementation, and modalities for transformation. Theories of place relate geographic variation in SOC to climate, soil types, land cover, and profile depth. Process-level theories of biophysical change and socioeconomic theories of induced change explain SOC transitions that follow from land use change when a declining curve is bent and recovery toward SOC saturation starts. While the desirability of recovering from SOC deficits has been mainstreamed into climate policy, the effectiveness of proposed measures taken remains contested. Process-level requirements for transitions at plot and landscape scales remain uncertain. Expectations of policy-induced SOC transitions have to align with national cross-sectoral C accounting and be managed realistically with land users (farmers) and commodity supply chains (private sector, consumers).
Tree diversity and social–ecological resilience of agroforestry after volcanic ash deposition in Indonesia
Smallholder farmers and their agroecosystems in active volcanic landscapes need to deal with and recover from eruptions. Resilience to extreme shocks may increase with system diversity, enhancing food and income security and ecosystem services provision; however, the longer term effects of volcanic ash are rarely assessed. To test the hypothesis that tree diversity contributes to the social–ecological resilience of coffee-based agroforestry, we quantified (1) the immediate effects of deposition of a 15-cm ash layer on tree survival, (2) the effect of volcanic ash on aboveground C stocks, tree diversity and wood density frequencies, (3) litter layer dynamics, and (4) farming system and income recovery 3 years after. Observations in four land-use systems before and after ash deposition (remnant forest, coffee-based complex and simple agroforestry, annual crops) were complemented by 46 farmer interviews on tree species’ survival, system, and financial recovery. Based on farmer interviews, low-wood-density trees were most affected by volcanic ash deposition. Ash deposition did not, after 3 years and across land-use systems, significantly change tree density, basal area, or C stocks. In contrast, species richness in coffee-based agroforestry increased significantly. Standing litter stocks in agroforestry decreased, but slower decomposition partially compensated for reduced litter input. Farmers stated that diversity and flexibility in coffee-based agroforestry support a system recovery that is faster than that for annual crops, suppressing income fluctuation. Farmer’s adaptive responses to enhance species diversity contributed to the resilience of farms, by retaining basic system structure and functions of agroforestry, and increasing product diversity and income.
Mapping and monitoring peatland conditions from global to field scale
Peatlands cover only 3–4% of the Earth’s surface, but they store nearly 30% of global soil carbon stock. This significant carbon store is under threat as peatlands continue to be degraded at alarming rates around the world. It has prompted countries worldwide to establish regulations to conserve and reduce emissions from this carbon rich ecosystem. For example, the EU has implemented new rules that mandate sustainable management of peatlands, critical to reaching the goal of carbon neutrality by 2050. However, a lack of information on the extent and condition of peatlands has hindered the development of national policies and restoration efforts. This paper reviews the current state of knowledge on mapping and monitoring peatlands from field sites to the globe and identifies areas where further research is needed. It presents an overview of the different methodologies used to map peatlands in nine countries, which vary in definition of peat soil and peatland, mapping coverage, and mapping detail. Whereas mapping peatlands across the world with only one approach is hardly possible, the paper highlights the need for more consistent approaches within regions having comparable peatland types and climates to inform their protection and urgent restoration. The review further summarises various approaches used for monitoring peatland conditions and functions. These include monitoring at the plot scale for degree of humification and stoichiometric ratio, and proximal sensing such as gamma radiometrics and electromagnetic induction at the field to landscape scale for mapping peat thickness and identifying hotspots for greenhouse gas (GHG) emissions. Remote sensing techniques with passive and active sensors at regional to national scale can help in monitoring subsidence rate, water table, peat moisture, landslides, and GHG emissions. Although the use of water table depth as a proxy for interannual GHG emissions from peatlands has been well established, there is no single remote sensing method or data product yet that has been verified beyond local or regional scales. Broader land-use change and fire monitoring at a global scale may further assist national GHG inventory reporting. Monitoring of peatland conditions to evaluate the success of individual restoration schemes still requires field work to assess local proxies combined with remote sensing and modeling. Long-term monitoring is necessary to draw valid conclusions on revegetation outcomes and associated GHG emissions in rewetted peatlands, as their dynamics are not fully understood at the site level. Monitoring vegetation development and hydrology of restored peatlands is needed as a proxy to assess the return of water and changes in nutrient cycling and biodiversity.
Biomass and soil carbon stocks in different forest types, Northwestern Ethiopia
Attempts to mitigate global climate change have brought forestry into focus. Forests absorb carbondioxide from the atmosphere, alleviate global warming and contribute for rural livelihoods. To realize these benefits, there is a need to conserve the existing forests and establish new forests by using different restoration techniques. Information is scarce in Ethiopia on the carbon stock efficiency of the different forest types. Therefore, this study focused on comparing biomass and soil carbon stock potential of a natural forest, exclosure and Eucalyptus plantation. Primary and secondary data were collected and analysed using allometric equations. The results of this study stated that the total mean carbon stock for exclosure was 131.6 ± 45.5 t ha−1, for plantation 160.1 ± 35.8 t ha−1 and for natural forest 195.3 ± 58.3 t ha−1. The carbon stocks in each pool exhibited distinct patterns between the forest types. The above ground, below ground and soil organic carbon stock, increased in the natural forests and plantation, while the litter carbon stock showed decreasing towards the exclosure. Generally, the total natural forests store high amount of carbon and can play an important role in climate change mitigation. The carbon pool variation between different forest types was significant at (P < .05); however, there was no significance difference between forest types by aboveground and belowground biomass. From the main findings of this study, it is possible to conclude that climate change mitigation measures should consider expanding exclosure with the same priority as conserving natural forest and increasing plantation forests.
The Grain-for-Green project offsets warming-induced soil organic carbon loss and increases soil carbon stock in Chinese Loess Plateau
The dynamics of soil organic carbon (SOC) stock is a vital element affecting the climate, and ecological restoration is potentially an effective measure to mitigate climate change by enhancing vegetation and soil carbon stocks and thereby offsetting greenhouse gas emissions. The Grain-for-Green project (GFGP) implemented in Chinese Loess Plateau (LP) since 1999 is one of the largest ecological restoration projects in the world. However, the contributions of ecological restoration and climate change to ecosystem soil carbon sequestration are still unclear. In this study, we improved a soil carbon decomposition framework by optimizing the initial SOC stock based on full spatial simulation of SOC and incorporating the priming effect to investigate the SOC dynamics across the LP GFGP region from 1982 through 2017. Our results indicated that SOC stock in the GFGP region increased by 20.18 Tg C from 1982 through 2017. Most portion (15.83 Tg C) of the SOC increase was accumulated when the GFGP was initiated, with a SOC sink of 16.12 Tg C owing to revegetation restoration and a carbon loss of 0.29 Tg C due to warming during this period. The relationships between SOC and forest canopy height and investigations on the SOC dynamics after afforestation revealed that the accumulation rate of SOC could be as high as 24.68 g C m−2 yr−1 during the 70 years following afforestation, and that SOC could decline thereafter (−8.89 g C m−2 yr−1), which was mainly caused by warming. This study provides a new method for quantifying the contribution of ecological restoration to SOC changes, and also cautions the potential risk of LP SOC loss in the mature forest soil under future warming.
Modeling the spatial distribution of soil organic carbon and carbon stocks for the Casanare flooded Savannas, Colombia
Flooded savannas are extensive in South America and this study was conducted to assess two digital soil mapping (DSM) approaches to predict the spatial distribution of soil organic carbon (SOC) content and stocks in the Orinoco flooded savannas of Casanare department, located in the eastern plains of Colombia. SOC was estimated using a total of 80 sites sampled at two soil depth intervals (0-10 cm and 10-30 cm). SOC ranged from 0.41% at 0-10 cm and 0.23% at 10-30 cm in drier soils found in continental dunes with sandy textures and low vegetation cover (steppe) to over 14.50% and 7.51% in soils that experienced seasonal flooding located in depressions with loamy textures and flooded savanna vegetation. Predictions of the spatial distribution of SOC were done through Expert Knowledge (EK) and Random Forest (RF) approaches across the study area at 0-10 cm and 10-30 cm soil depth. Both DSM approaches were assessed through root mean square errors, mean absolute errors, and coefficients of determination. Although both DSM approaches performed very well, EK was considered slightly superior to predict SOC in the Casanare flooded savannas. Covariates derived from vegetation coverage, topography, and soil texture properties were identified as key drivers in controlling its distribution at the study area. We found total SOC stocks of 55.07 Mt with a mean density of 83.13 ± 24.32 t ha-1 stored in the first 30 cm soil depth, with 12.3% of this being located in the flooded parts of the savanna landscape, which represented only 7.9% of the study area (664,752 ha). This study provides the first effort to systematically quantify SOC stocks in the Casanare flooded savannas and shows the importance of conserving this ecosystem with the aim of avoiding SOC losses and consequent increased CO2 emissions to the atmosphere. We estimate that the department of Casanare would release an average of 2,42 Mton of CO2 emissions per year over 30 years if there were large scale conversion of the flooded savannas to intensive agriculture, which corresponds to 62% of the current emissions of the department. At regional level, the impact of a large-scale land use conversion of the flooded Llanos del Orinoco ecosystem area (15 Mha) would represent 1/3 of the current net Colombian CO2 emission (AFOLU), which makes this region a potentially important source of emissions if correct decisions are not taken regarding the land management.
The role of social forestry in achieving NDC targets: Study cases of Lampung and DI Yogyakarta
Social Forestry (SF) in Indonesia has emerged as a keystone strategy for Sustainable Forest Management. By allocating 12.7 million ha of forest to be managed by local communities, the government has set in motion an ambitious plan for SF to reduce poverty, empower local people, and improve forest conditions. More recently, SF is framed for its opportunity to contribute to climate change mitigation and adaptation. This study focused on examining the contribution of SF to the Nationally Determined Contribution (NDC) goals in Yogyakarta and Lampung. By analyzing spatial data of SF areas and land cover changes using ArcView 10.8, the study assessed the carbon stock potential in SF areas. Carbon stock calculations were based on the 2022 National Forest Reference Level (FRL) for the periods before and after SF implementation. The finding of the study indicated that the carbon stock of SF areas in Yogyakarta and Lampung ranged from 9,214,381 to 9,923,420 ton CO2eq prior to SF, while the current carbon stock ranges from 8,703,489 to 9,393,706 ton CO2eq, representing a decrease (around 5.4%) rather than an increase. Overall, the changes in carbon stock were relatively small and localized, and the magnitude of the increase was insufficient to offset the overall decrease. To achieve the objectives of SF, such as meeting emission targets and achieving sustainable land use, it is crucial to carefully manage forest edges and fragmented forests, as they can contribute to carbon stock losses. Additionally, further studies and research are needed to improve the accuracy of carbon stock calculations, particularly for non-forest categories, which have higher uncertainty in the reference levels.
Risks to carbon storage from land-use change revealed by peat thickness maps of Peru
Tropical peatlands are among the most carbon-dense ecosystems but land-use change has led to the loss of large peatland areas, associated with substantial greenhouse gas emissions. To design effective conservation and restoration policies, maps of the location and carbon storage of tropical peatlands are vital. This is especially so in countries such as Peru where the distribution of its large, hydrologically intact peatlands is poorly known. Here field and remote sensing data support the model development of peatland extent and thickness for lowland Peruvian Amazonia. We estimate a peatland area of 62,714 km2 (5th and 95th confidence interval percentiles of 58,325 and 67,102 km2, respectively) and carbon stock of 5.4 (2.6–10.6) PgC, a value approaching the entire above-ground carbon stock of Peru but contained within just 5% of its land area. Combining the map of peatland extent with national land-cover data we reveal small but growing areas of deforestation and associated CO2 emissions from peat decomposition due to conversion to mining, urban areas and agriculture. The emissions from peatland areas classified as forest in 2000 represent 1–4% of Peruvian CO2 forest emissions between 2000 and 2016. We suggest that bespoke monitoring, protection and sustainable management of tropical peatlands are required to avoid further degradation and CO2 emissions.