Mangroves are one of the most efficient organic carbon sink ecosystems which occur along intertidal coastal areas of tropical and subtropical regions. Together with other coastal wetlands such as saltmarsh and seagrass, mangroves have been termed ‘blue carbon’ ecosystems due to their substantial capacity for carbon storage and sequestration. Consequently, policymakers and stakeholders promote mangroves for natural-based climate change mitigation. However, many mangroves across the world are being altered by anthropogenic disturbances including land-use and land-cover change (LULCC). Large-scale LULCC will inevitably affect the magnitude and direction (loss or gain) of the carbon cycle in mangroves.
Tag: Carbon sequestration
Low-emissions and profitable cocoa through moderate-shade agroforestry: Insights from Ghana
Cocoa production is a leading driver of deforestation in the humid-tropics of West Africa. Reconciling climate change mitigation with livelihoods of farmers requires identification of production strategies to concurrently improve yield and profit while curtailing emissions of greenhouse gases (GHG). Using a 2021 plot-survey conducted in Ghana’s Eastern region, we evaluated yields, GHG emissions, and value of production (VOP) (a profit indicator) across a typology representing the diversity of systems at plot-level. The typology was constructed by first stratifying plots according to shade levels and variety (hybrid vs. Amazonia) which resulted in three systems: Hybrid sun, hybrid variety under full-sun (little to no shade); Hybrid shade, hybrid and moderate shade (13–25 shade trees ha−1); and Amazonia, Amazonia under predominantly moderate shade. Next, factor analysis and clustering were used to group plots within each system according to cocoa yield, vegetation, management, and (local) climate conditions. Cluster analysis showed that fertiliser, weeding, pruning, hand pollination, cocoa tree density, and shade tree densities of differing heights were most influential for determination across systems. Hybrid shade had the highest net GHG removal rate at −6.8 ± 1.7 (± 95% CI) Mg CO2eq ha−1 yr−1: 48% and 127% higher (emissions more negative) respectively over Amazonia and Hybrid sun. Hybrid shade additionally had the highest average and least variable VOP among production systems at 669 ± 564 USD ha−1 yr−1, compared to Hybrid sun and Amazonia at 404 ± 442 and 213 ± 280 USD ha−1 yr−1 respectively. These results point to hybrid cocoa grown under moderate shade of 13–25 shade trees ha−1 as optimal for reconciling climate change mitigation with development in West African cocoa.
All tidal wetlands are blue carbon ecosystems
Managing coastal wetlands is one of the most promising activities to reduce atmospheric greenhouse gases, and it also contributes to meeting the United Nations Sustainable Development Goals. One of the options is through blue carbon projects, in which mangroves, saltmarshes, and seagrass are managed to increase carbon sequestration and reduce greenhouse gas emissions. However, other tidal wetlands align with the characteristics of blue carbon. These wetlands are called tidal freshwater wetlands in the United States, supratidal wetlands in Australia, transitional forests in Southeast Asia, and estuarine forests in South Africa. They have similar or larger potential for atmospheric carbon sequestration and emission reductions than the currently considered blue carbon ecosystems and have been highly exploited. In the present article, we suggest that all wetlands directly or indirectly influenced by tides should be considered blue carbon. Their protection and restoration through carbon offsets could reduce emissions while providing multiple cobenefits, including biodiversity.
Imperata economics and policy
Should policymakers — or anyone else — care about millions of ha of Imperata grasslands The answer depends on the balance between costs of conversion to other uses and the net benefits produced in economic growth, poverty alleviation, and protection of the environment. The first section on Imperata economics sets up the analytical framework to address this question and draws on the wider development economics literature to consider whether growth and poverty alleviation are conflicting or complementary objectives. Although evidence is limited, it suggests smallholder-based agroforestry could provide the same economic growth with greater poverty alleviation than large-scale forestry estates. There is, however, no substitute for project appraisal for specific settings. The second section on Imperata policy reviews whether policy distortions and market failures provide a sufficient rationale for direct policy intervention to promote tree planting on Imperata grasslands. Estimates of imputed values of carbon sequestration to alleviate global warming are presented for Acacia mangium and rubber agroforestry. The conclusion summarizes the policy research agenda and examines the desirability and feasibility of policy intervention to promote carbon sequestration through Imperata grassland conversion to tree-based systems.
Peatland restoration, rewetting and greenhouse gas balances
While peatlands have been utilized for thousands of years (e.g., 7th-century law texts contain references to turf cutting in Ireland, large-scale drainage for agriculture, afforestation, and peat extraction commenced earnestly in the 17th century in Europe. More and more areas were drained in Europe and North America until the second half of the 20th century, contemporaneously with the start of large- scale drainage of tropical peatlands in South-East Asia, for example, while tropical peatlands in other regions in Africa and Central and South America are still exposed to increasing anthropogenic impacts.
Four decades of data indicate that planted mangroves stored up to 75% of the carbon stocks found in intact mature stands
Mangroves’ ability to store carbon (C) has long been recognized, but little is known about whether planted mangroves can store C as efficiently as naturally established (i.e., intact) stands and in which time frame. Through Bayesian logistic models compiled from 40 years of data and built from 684 planted mangrove stands worldwide, we found that biomass C stock culminated at 71 to 73% to that of intact stands ~20 years after planting. Furthermore, prioritizing mixed-species planting including Rhizophora spp. would maximize C accumulation within the biomass compared to monospecific planting. Despite a 25% increase in the first 5 years following planting, no notable change was observed in the soil C stocks thereafter, which remains at a constant value of 75% to that of intact soil C stock, suggesting that planting effectively prevents further C losses due to land use change. These results have strong implications for mangrove restoration planning and serve as a baseline for future C buildup assessments.
The enduring world forest carbon sink
The uptake of carbon dioxide (CO2) by terrestrial ecosystems is critical for moderating climate change. To provide a ground-based long-term assessment of the contribution of forests to terrestrial CO2 uptake, we synthesized in situ forest data from boreal, temperate and tropical biomes spanning three decades. We found that the carbon sink in global forests was steady, at 3.6 ± 0.4 Pg C yr−1 in the 1990s and 2000s, and 3.5 ± 0.4 Pg C yr−1 in the 2010s. Despite this global stability, our analysis revealed some major biome-level changes. Carbon sinks have increased in temperate (+30 ± 5%) and tropical regrowth (+29 ± 8%) forests owing to increases in forest area, but they decreased in boreal (−36 ± 6%) and tropical intact (−31 ± 7%) forests, as a result of intensified disturbances and losses in intact forest area, respectively. Mass-balance studies indicate that the global land carbon sink has increased, implying an increase in the non-forest-land carbon sink. The global forest sink is equivalent to almost half of fossil-fuel emissions (7.8 ± 0.4 Pg C yr−1 in 1990–2019). However, two-thirds of the benefit from the sink has been negated by tropical deforestation (2.2 ± 0.5 Pg C yr−1 in 1990–2019). Although the global forest sink has endured undiminished for three decades, despite regional variations, it could be weakened by ageing forests, continuing deforestation and further intensification of disturbance regimes. To protect the carbon sink, land management policies are needed to limit deforestation, promote forest restoration and improve timber-harvesting practices.
Allometric Equations for the Biomass Estimation of Calophyllum inophyllum L. in Java, Indonesia
Reliable data on CO2 quantification is increasingly important to quantify the climate benefits of forest landscape restoration and international commitments, such as the Warsaw REDD+ Framework and Nationally Determined Contributions under the Paris Agreement. Calophyllum inophyllum L. (nyamplung as a local name or tamanu tree for the commercial name) is an increasingly popular tree species in forest landscape restoration and bioenergy production for a variety of reasons. In this paper, we present allometric equations for aboveground biomass (AGB), belowground biomass (BGB), and total above- and belowground biomass (TABGB) predictions of C. inophyllum L. Data collection was carried out twice (2017 and 2021) from 40 trees in Java, Indonesia. Allometric equations using the natural logarithm of diameter at breast height (lnDBH) and ln height (lnH) for biomass prediction qualified the model’s fit with statistical significance at 95% of the confidence interval for AGB, BGB, and TABGB predictions. The results showed that the linear models using both lnDBH and lnH were well fit and accurate. However, the model with lnDBH is more precise than the model using lnH. Using lnDBH as a predictor, the R2 values were 0.923, 0.945, and 0.932, and MAPE were 24.7, 37.0, and 25.8 for AGB, BGB, and TABGB, respectively. Using lnH as a predictor, the R2 values were 0.887, 0.918, and 0.898 and MAPE were 37.4, 49.0, and 39.8 for AGB, BGB, and TABGB, respectively. Consequently, the driven allometric equations can help accurate biomass quantification for carbon-trading schemes of C. inophyllum L.
Global carbon sequestration potential of agroforestry and increased tree cover on agricultural land
Biomass is fundamental to circular agricultural systems. Estimates of above- and below-ground biomass on agricultural land based upon IPCC Tier 1 estimates are compared with an updated carbon density map based on remote sensing, with results indicating the methodology and initial estimations are robust. Two scenarios are evaluated to estimate carbon sequestration potential of increasing tree cover on agricultural land: 1) incremental change and 2) a systemic change to agroforestry. Estimates of above- and below ground biomass carbon were combined with a tree cover analysis to estimate the increase in biomass. Global increases (4−6 PgC for incremental change; 12−19 PgC for systemic change) highlight substantial mitigation potential. Increasing global tree cover on agricultural land by 10% would sequester more than 18 PgC. South America has the highest potential, followed by Southeast Asia, West and Central Africa, and North America. Brazil, Indonesia, Philippines, India, the United States and China are among the top countries with the highest carbon sequestration potential on agricultural land with increased tree cover.
Sustaining local livelihoods through carbon sequestration activities: a search for practical and strategic approach
In many parts of the developing world carbon sequestration projects have been implemented in association with community development. This is a practical way to demonstrate environmental as well as social benefits of the projects. To some extent the projects are in line with the dual objectives of the Kyoto Protocol’s Clean Development Mechanism (CDM). Knowing the immaturity of CDM market and the dynamics of the negotiations in the Conferences of Parties (COPs) to the United Nations Framework Convention on Climate Change (UNFCCC), it is timely to explore strategic and long-term approaches. This paper attempts to synthesize the lessons learned from Mexico, Colombia, Costa Rica, Philippines, Indonesia, and Timor Leste presented and discussed in the workshop to mark the entry into force of the Kyoto Protocol. Most of the projects do not necessarily comply with the strict rules of CDM partly due to the fact that the current agreement only allows afforestation and reforestation activities. Conservation of carbon storage (e.g. in peatlands) is not eligible for funding under the existing rules. Strategic approaches, such as inclusion of deforestation avoidance in the next round of negotiations and subsequent commitment period, were critically reviewed. A number of loopholes that require scientifically sound justification were identified. In addition, issues related to methodologies to determine the baseline, monitor additionality, leakage and permanence remain challenging. It is generally demonstrated that local participation is very strong in all of the projects examined. It was learned that large-scale plantation projects offer few benefits for the community, whereas small-scale projects that allow the community to participate offer the possibility to earn carbon credits as well as socio-economic and cultural benefits. However, many of these projects are so small in size that they generate high transaction costs. Otherwise the projects could demonstrate financial additionality from the point of view of the hosts. It was strongly suggested that in order to sustain livelihoods the projects have to be recognized by and linked with donor and policy communities. In addition, engagement of the private sector has to be further explored.