Carbon offset credits, and associated projects, are acclaimed to address economic, environmental and social issues simultaneously. However, critics argue that carbon offset mechanisms are ill equipped to assist developing countries in achieving sustainable development. Social standards now exist to provide robust methods for assessing the social and biodiversity performance of carbon offset projects and credible impact assessments to help ensure positive outcomes for local people and biodiversity. Following such a standard, and simultaneously applying the Sustainable Livelihoods Approach, we develop the Coastal Carbon Impacts Framework (CCIF) as a conceptual framework to document the potential positive and negative impacts of coastal carbon offset projects on local livelihoods. We apply the CCIF to four case studies and derive its main livelihood outcomes as well as describe potential long-term impacts. By using the capitals approach, the CCIF is able to dismantle the different impact areas into smaller entities. This allows a more detailed analysis on the positive and negative impacts a project has on communities – across the natural, financial, social, human, physical, cultural and political capital. While the case studies analysed show mainly positive outcomes, certainly no project is without risk of negatively impacting the community. The CCIF is however able to demonstrate potential social risk areas. If applied to additional coastal carbon offset projects, best practice documents, community engagement and the monitoring and evaluation process of such projects can be improved.
Blue Carbon & Sequestration
The restoration and protection of “blue carbon” ecosystems – mangroves, seagrasses, and tidal marshes – has potential to offset greenhouse gas emissions and improve coastal livelihoods. However, realisation of this potential relies on global investment in restoration and protection, which in turn relies on appropriate funding mechanisms that are currently impeded by multiple constraints. Constraints include commercial considerations by private investors (including reliable estimates of financial returns, risk quantification and management, and supply chain impacts), regulatory and legal uncertainty (such as the complexity of property rights in coastal areas, policy coordination across jurisdictions, and stable policy consistent with the duration of blue carbon projects). There are, however, opportunities to improve on current practices, including better stakeholder engagement (including social license to operate, and knowledge transfer to promote best practices), and targeted use of public and philanthropic funding (to subsidise demonstration projects, reduce financial risk through collaterals, and promote low-profit but high co-benefit projects). In this paper, a strategy for the realisation of potential benefits through commercially viable and scientifically robust blue carbon initiatives is presented alongside insights and guidance for the policy, research, civil society, and private sectors to achieve these important long-term outcomes.
The drastic land cover change and its impacts in the Yellow Sea have long been significant issues in terms of coastal vulnerabilities, but holistic data analysis is limited. The present study first reports 40 years long geographical changes of the Yellow Sea coasts including all three neighboring countries of China, North Korea, and South Korea. We delineated tidal flats by analysis of Landsat series satellite imageries (662 scenes) between 1981 and 2016. A total area of the Yellow Sea tidal flats has been considerably reducing for the past 36 years, from ∼10,500 km2 (1980s) to ∼6700 km2(2010s), say ∼1% annual loss. A majority loss of tidal flats was mainly due to the grand reclamations that conducted in almost entire coast of the Yellow Sea, particularly concentrated in the 1990s-2000s. Coastal reclaimed area during the past four decades reached ∼9700 km2, including ongoing and planned projects, which corresponds to over half the area of precedent natural tidal flats of the Yellow Sea. The potential carbon stocks in the eight representative regions with large scale reclamation indicated significant loss in carbon sink capacity in the South Korea's coast (∼99%), while evidenced a lesser loss from the China's coast (∼31%). It was noteworthy that the progradation of tidal flats after the reclamation in China's coast significantly reduced the loss of carbon sequestration. According to the ecosystem services valuation for the Yellow Sea, a total loss was estimated as ∼8 billion USD yr−1 with relatively high proportional loss (up to 25%) of climate regulating services (viz., carbon sequestration). Overall, huge losses in ecosystem services being provided by the Yellow Sea natural tidal flats need immediate action to prevent or at least alleviate accelerating ecological deteriorations. Finally, future conservative policy direction on coastal wetlands management has been proposed towards enhancement of marine ecosystem services.
Marine plant communities such as kelp forests produce significant amounts of detritus, most of which is exported to areas where it can constitute an important trophic subsidy or potentially be sequestered in marine sediments. Knowing the vertical transport speed of detrital particles is critical to understanding the potential magnitude and spatial extent of these linkages. We measured sinking speeds for Laminaria hyperborea detritus ranging from whole plants to small fragments and sea urchin faecal pellets, capturing the entire range of particulate organic matter produced by kelp forests. Under typical current conditions, we determined that this organic material can be transported 10 s of m to 10 s of km. We show how the conversion of kelp fragments to sea urchin faeces, one of the most pervasive processes in kelp forests globally, increases the dispersal potential of detritus by 1 to 2 orders of magnitude. Kelp detritus sinking speeds were also faster than equivalent phytoplankton, highlighting its potential for rapid delivery of carbon to deep areas. Our findings support arguments for a significant contribution from kelp forests to subsidizing deep sea communities and the global carbon sink.
Emission of greenhouse gases, including carbon dioxide (CO2), has been the main cause of climate change and global warming since the mid-20th century. Blue carbon (BC) ecosystems, which include tidal marshes, mangroves, and seagrass meadows, play a key role in climate change mitigation and adaptation. Despite occupying only 0.2% of the ocean surface, they contribute 50% of carbon burial in marine sediments, equivalent to the sequestration of 1%–2% of current global CO2 emissions from fossil fuel combustion. Conversely, damage to these ecosystems risks the release of that carbon back to the atmosphere. Conserving and restoring BC ecosystems not only maintains CO2 sequestration capacity but also services essential for climate change adaptation along coasts, including prevention of shoreline erosion. However, BC ecosystems rank among the most threatened ecosystems on earth. Urgent action is needed to prevent further degradation, to avoid additional greenhouse emissions, as well as restoring degraded habitats to recover their climate change mitigation potential.
Because mangroves store greater amounts of carbon (C) per area than any other terrestrial ecosystem, conservation of mangrove forests on a global scale represents a potentially meaningful strategy for mitigating atmospheric greenhouse‐gas (GHG) emissions. However, analyses of how coastal ecosystems influence the global C cycle also require the mapping of ecosystem area across the Earth's surface to estimate C storage and flux (movement) in order to compare how different ecosystem types may mitigate GHG enrichment in the atmosphere. In this paper, we propose a new framework based on diverse coastal morphology (that is, different coastal environmental settings resulting from how rivers, tides, waves, and climate have shaped coastal landforms) to explain global variations in mangrove C storage, using soil organic carbon (SOC) as a model to more accurately determine mangrove contributions to global C dynamics. We present, to the best of our knowledge, the first global mangrove area estimate occupying distinct coastal environmental settings, comparing the role of terrigenous and carbonate settings as global “blue carbon” hotspots. C storage in deltaic settings has been overestimated, while SOC stocks in carbonate settings have been underestimated by up to 50%. We encourage the scientific community, which has largely focused on blue carbon estimates, to incorporate coastal environmental settings into their evaluations of C stocks, to obtain more robust estimates of global C stocks.
Blue carbon policy supports carbon sequestration whilst also conserving our remaining seagrass meadows. The complex biogeochemical processes within the sediment of seagrass meadows are responsible for the longevity of the stored carbon. Carbon stock and accumulation rates are controlled by the interaction of hydrodynamic, geochemical and biotic processes unique to each meadow. Carbon content (stock and flux) of a meadow must be quantified for inclusion in carbon accounting, whether for market trading or national greenhouse gas accounting. Management of seagrass blue carbon also requires estimates of additionality, leakage, permanence, conversion and emission factors.
Highly productive coastal wetlands play an essential role in storing blue carbon as one of their ecosystem services, but they are increasingly jeopardized by intensive reclamation activities to facilitate rapid population growth and urbanization. Coastal reclamation causes the destruction and severe degradation of wetland ecosystems, which may affect their abilities to store blue carbon. To assist with international accords on blue carbon, we evaluated the dynamics of blue carbon storage in coastal wetlands under coastal reclamation in China. By integrating carbon density data collected from field measurement experiments and from the literature, an InVEST model, Carbon Storage and Sequestration was used to estimate carbon storage across the reclamation area between 1990 and 2015. The result is the first map capable of informing about blue carbon storage in coastal reclamation areas on a national scale. We found that more than 380,000 hectares of coastal wetlands were affected by reclamation, which resulted in the release of ca. 20.7 Tg of blue carbon. The carbon loss from natural wetlands to artificial wetlands accounted for 72.5% of total carbon loss, which highlights the major task in managing coastal sustainability. In addition, the top 20% of coastal wetlands in carbon storage loss covered 4.2% of the total reclamation area, which can be applied as critical information for coastal redline planning. We conclude that the release of blue carbon due to the conversion of natural wetlands exceeded the total carbon emission from energy consumption within the reclamation area. Implementing the Redline policy could guide the management of coastal areas resulting in greater resiliency regarding carbon emission and sustained ecosystem services.
Macroalgae form the most extensive and productive benthic marine vegetated habitats globally but their inclusion in Blue Carbon (BC) strategies remains controversial. We review the arguments offered to reject or include macroalgae in the BC framework, and identify the challenges that have precluded macroalgae from being incorporated so far. Evidence that macroalgae support significant carbon burial is compelling. The carbon they supply to sediment stocks in angiosperm BC habitats is already included in current assessments, so that macroalgae are de facto recognized as important donors of BC. The key challenges are (i) documenting macroalgal carbon sequestered beyond BC habitat, (ii) tracing it back to source habitats, and (iii) showing that management actions at the habitat lead to increased sequestration at the sink site. These challenges apply equally to carbon exported from BC coastal habitats. Because of the large carbon sink they support, incorporation of macroalgae into BC accounting and actions is an imperative. This requires a paradigm shift in accounting procedures as well as developing methods to enable the capacity to trace carbon from donor to sink habitats in the ocean.
Seagrass ecosystems contain globally significant organic carbon (C) stocks. However, climate change and increasing frequency of extreme events threaten their preservation. Shark Bay, Western Australia, has the largest C stock reported for a seagrass ecosystem, containing up to 1.3% of the total C stored within the top metre of seagrass sediments worldwide. On the basis of field studies and satellite imagery, we estimate that 36% of Shark Bay’s seagrass meadows were damaged following a marine heatwave in 2010/2011. Assuming that 10 to 50% of the seagrass sediment C stock was exposed to oxic conditions after disturbance, between 2 and 9 Tg CO2 could have been released to the atmosphere during the following three years, increasing emissions from land-use change in Australia by 4–21% per annum. With heatwaves predicted to increase with further climate warming, conservation of seagrass ecosystems is essential to avoid adverse feedbacks on the climate system.