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Background: Global climate change is one of the major challenges facing the world today, and forests play a crucial role as significant carbon sinks and providers of ecosystem services in mitigating climate change and protecting the environment. China, as one of the largest developing countries globally, owns 60% of its forest resources collectively. Evaluating the carbon sequestration cost of collective forests not only helps assess the contribution of China's forest resources to global climate change mitigation but also provides important evidence for formulating relevant policies and measures. Results: Over the past 30 years, the carbon sequestration cost of collective forests in China has shown an overall upward trend. Except for coastal provinces, southern collective forest areas, as well as some southwestern and northeastern regions, have the advantage of lower carbon sequestration costs. Furthermore, LSTM network predictions indicate that the carbon sequestration cost of collective forests in China will continue to rise. By 2030, the average carbon sequestration cost of collective forests is projected to reach 125 CNY per ton(= 16.06 Euros/t). Additionally, there is spatial correlation in the carbon sequestration cost of collective forests. Timber production, labor costs, and labor prices have negative spatial spillover effects on carbon sequestration costs, while land opportunity costs, forest accumulation, and rural resident consumption have positive spatial spillover effects. Conclusion: The results of this study indicate regional disparities in the spatial distribution of carbon sequestration costs of collective forests, with an undeniable upward trend in future cost growth. It is essential to focus on areas with lower carbon sequestration costs and formulate targeted carbon sink economic policies and management measures to maximize the carbon sequestration potential of collective forests and promote the sustainable development of forestry. [ABSTRACT FROM AUTHOR]

The conservation, restoration, and improved management of terrestrial forests significantly contributes to mitigate climate change and its impacts, as well as providing numerous co‐benefits. The pressing need to reduce emissions and increase carbon removal from the atmosphere is now also leading to the development of natural climate solutions in the ocean. Interest in the carbon sequestration potential of underwater macroalgal forests is growing rapidly among policy, conservation, and corporate sectors. Yet, our understanding of whether carbon sequestration from macroalgal forests can lead to tangible climate change mitigation remains severely limited, hampering their inclusion in international policy or carbon finance frameworks. Here, we examine the results of over 180 publications to synthesise evidence regarding macroalgal forest carbon sequestration potential. We show that research efforts on macroalgae carbon sequestration are heavily skewed towards particulate organic carbon (POC) pathways (77% of data publications), and that carbon fixation is the most studied flux (55%). Fluxes leading directly to carbon sequestration (e.g. carbon export or burial in marine sediments) remain poorly resolved, likely hindering regional or country‐level assessments of carbon sequestration potential, which are only available from 17 of the 150 countries where macroalgal forests occur. To solve this issue, we present a framework to categorize coastlines according to their carbon sequestration potential. Finally, we review the multiple avenues through which this sequestration can translate into climate change mitigation capacity, which largely depends on whether management interventions can increase carbon removal above a natural baseline or avoid further carbon emissions. We find that conservation, restoration and afforestation interventions on macroalgal forests can potentially lead to carbon removal in the order of 10's of Tg C globally. Although this is lower than current estimates of natural sequestration value of all macroalgal habitats (61–268 Tg C year−1), it suggests that macroalgal forests could add to the total mitigation potential of coastal blue carbon ecosystems, and offer valuable mitigation opportunities in polar and temperate areas where blue carbon mitigation is currently low. Operationalizing that potential will necessitate the development of models that reliably estimate the proportion of production sequestered, improvements in macroalgae carbon fingerprinting techniques, and a rethinking of carbon accounting methodologies. The ocean provides major opportunities to mitigate and adapt to climate change, and the largest coastal vegetated habitat on Earth should not be ignored simply because it does not fit into existing frameworks. [ABSTRACT FROM AUTHOR]

Countries have pledged to different national and international environmental agreements, most prominently the climate change mitigation targets of the Paris Agreement. Accounting for carbon stocks and flows (fluxes) is essential for countries that have recently adopted the United Nations System of Environmental-Economic Accounting - ecosystem accounting framework (UNSEEA) as a global statistical standard. In this paper, we analyze how spatial carbon fluxes can be used in support of the UNSEEA carbon accounts in five case countries with available in-situ data. Using global multi-date biomass map products and other remotely sensed data, we mapped the 2010–2018 carbon fluxes in Brazil, the Netherlands, the Philippines, Sweden and the USA using National Forest Inventory (NFI) and local biomass maps from airborne LiDAR as reference data. We identified areas that are unsupported by the reference data within environmental feature space (6–47% of vegetated country area); cross-validated an ensemble machine learning (RMSE=9–39 Mg C ha - 1 and R 2 =0.16–0.71) used to map carbon fluxes with prediction intervals; and assessed spatially correlated residuals (<5 km) before aggregating carbon fluxes from 1-ha pixels to UNSEEA forest classes. The resulting carbon accounting tables revealed the net carbon sequestration in natural broadleaved forests. Both in plantations and in other woody vegetation ecosystems, emissions exceeded sequestration. Overall, our estimates align with FAO-Forest Resource Assessment and national studies with the largest deviations in Brazil and USA. These two countries used highly clustered reference data, where clustering caused uncertainty given the need to extrapolate to under-sampled areas. We finally provide recommendations to mitigate the effect of under-sampling and to better account for the uncertainties once carbon stocks and flows need to be aggregated in relatively smaller countries. These actions are timely given the global initiatives that aim to upscale UNSEEA carbon accounting. [ABSTRACT FROM AUTHOR]

The current study emphasizes the inherent shortcomings of laws and policy approaches that are based on the premise that by increasing wood production, much more emission credits can be achieved by using wood in alternative uses. The article aims to exploit the financing of emission reductions, discuss how carbon sinks held in forest resources can be activated, traded, and financed, and explain how Turkiye's forest carbon potential can be exploited. To make a comparative analysis of the situation of Turkiye at global level, Russian's potential for carbon sequestration and its trade have been dealt with as a comparison by following quantitative research methodology. In this research, the calculation method has been used to determine the number of houses that are likely to be built in rural areas using wood materials, e.g., the construction of 100,000 houses with a construction area of 100 m² per year. Consequently, the forest carbon generated by alternative scenarios contributes positively to the emission balance sheet, as well as climate change mitigation through carbon emission trade despite all legal and technical constraints. Although both countries have similar shortcomings of obtaining carbon credits and its trade, of course Russia has a promising situation in comparison with Turkiye with respect to the amount of carbon sequestered and the likelihood of its trade potential at global level. [ABSTRACT FROM AUTHOR]

Countries have pledged to different national and international environmental agreements, most prominently the climate change mitigation targets of the Paris Agreement. Accounting for carbon stocks and flows (fluxes) is essential for countries that have recently adopted the United Nations System of Environmental-Economic Accounting - ecosystem accounting framework (UNSEEA) as a global statistical standard. In this paper, we analyze how spatial carbon fluxes can be used in support of the UNSEEA carbon accounts in five case countries with available in-situ data. Using global multi-date biomass map products and other remotely sensed data, we mapped the 2010–2018 carbon fluxes in Brazil, the Netherlands, the Philippines, Sweden and the USA using National Forest Inventory (NFI) and local biomass maps from airborne LiDAR as reference data. We identified areas that are unsupported by the reference data within environmental feature space (6–47% of vegetated country area); cross-validated an ensemble machine learning (RMSE=9–39 Mg C ha - 1 and R 2 =0.16–0.71) used to map carbon fluxes with prediction intervals; and assessed spatially correlated residuals (<5 km) before aggregating carbon fluxes from 1-ha pixels to UNSEEA forest classes. The resulting carbon accounting tables revealed the net carbon sequestration in natural broadleaved forests. Both in plantations and in other woody vegetation ecosystems, emissions exceeded sequestration. Overall, our estimates align with FAO-Forest Resource Assessment and national studies with the largest deviations in Brazil and USA. These two countries used highly clustered reference data, where clustering caused uncertainty given the need to extrapolate to under-sampled areas. We finally provide recommendations to mitigate the effect of under-sampling and to better account for the uncertainties once carbon stocks and flows need to be aggregated in relatively smaller countries. These actions are timely given the global initiatives that aim to upscale UNSEEA carbon accounting. [ABSTRACT FROM AUTHOR]

The global climate warming caused by greenhouse gases poses a great threat to human living and biological ecosystems. To mitigate climate change, many measures have been taken to reduce carbon dioxide emissions. Among them, the forest carbon sink (FCS) is considered as one of the most economical and effective carbon sequestration methods to realize carbon emission reductions in next 30 to 50 years. FCS projects are being implemented in many countries to increase their carbon sequestration and thereby to realize carbon emission reductions. However, there are some issues associated with implementation with such policies. Firstly, these projects mainly have focused only on carbon sequestration and have ignored the comprehensive ecological effects to obtain their best economical benefits. Secondly, implementing these projects fails to establish a sustainable and healthy forest industry because they place too much reliance on preferential policies from governments. Finally, the projects lack systematic technological standards and legislation to guarantee their smooth implementation. This editorial briefly discusses these issues for the suitable implementation of the FCS projects. [ABSTRACT FROM AUTHOR]

Mangroves have been identified as blue carbon ecosystems that are natural carbon sinks. In Bangladesh, the establishment of mangrove plantations for coastal protection has occurred since the 1960s, but the plantations may also be a sustainable pathway to enhance carbon sequestration, which can help Bangladesh meet its greenhouse gas (GHG) emission reduction targets, contributing to climate change mitigation. As a part of its Nationally Determined Contribution (NDC) under the Paris Agreement 2016, Bangladesh is committed to limiting the GHG emissions through the expansion of mangrove plantations, but the level of carbon removal that could be achieved through the establishment of plantations has not yet been estimated. The mean ecosystem carbon stock of 5–42 years aged (average age: 25.5 years) mangrove plantations was 190.1 (±30.3) Mg C ha−1, with ecosystem carbon stocks varying regionally. The biomass carbon stock was 60.3 (±5.6) Mg C ha−1 and the soil carbon stock was 129.8 (±24.8) Mg C ha−1 in the top 1 m of which 43.9 Mg C ha−1 was added to the soil after plantation establishment. Plantations at age 5 to 42 years achieved 52% of the mean ecosystem carbon stock calculated for the reference site (Sundarbans natural mangroves). Since 1966, the 28,000 ha of established plantations to the east of the Sundarbans have accumulated approximately 76,607 Mg C year−1 sequestration in biomass and 37,542 Mg C year−1 sequestration in soils, totaling 114,149 Mg C year−1. Continuation of the current plantation success rate would sequester an additional 664,850 Mg C by 2030, which is 4.4% of Bangladesh's 2030 GHG reduction target from all sectors described in its NDC, however, plantations for climate change mitigation would be most effective 20 years after establishment. Higher levels of investment in mangrove plantations and higher plantation establishment success could contribute up to 2,098,093 Mg C to blue carbon sequestration and climate change mitigation in Bangladesh by 2030. [ABSTRACT FROM AUTHOR]

Wetlands are strategic areas for carbon uptake, but accurate assessments of their sequestration ability are limited by the uncertainty and variability in their carbon balances. Based on 2385 observations of annual net ecosystem production from global wetlands, we show that the mean net carbon sinks of inland wetlands, peatlands and coastal wetlands are 0.57, 0.29 and 1.88 tons of carbon per hectare per year, respectively, with a mean value of 0.57 tons of carbon per hectare per year weighted by the distribution area of different wetland types. Carbon sinks are mainly in Asia and North America. Within and across wetland types, we find that water table depth (WTD) exerts greater control than climate‐ and ecosystem‐related variables, and an increase in WTD results in a stronger carbon sink. Our results highlight an urgent need to sustain wetland hydrology under global change; otherwise, wetlands are at high risk of becoming carbon sources to the atmosphere. [ABSTRACT FROM AUTHOR]

The stocking and sequestering of increasing atmospheric carbon dioxide (CO2) and the reduction of greenhouse gas (GHG) emissions that result from improving the carbon sink are two important ways that forested land contributes to the fight against global warming. The purpose of the study is to estimate the rate of carbon sequestration (CS) in Edo State, Nigeria, as well as the volume of deforestation and its impact on CS. To gauge the changes in carbon stock, stock-difference and gain-loss methods were employed. The gain-loss method predicts gains and losses based on off-take and growth rates, while the stock-difference approach uses actual measurements of carbon stocks over a given period of time. These two methods presuppose that changes in carbon stock and CO2 flows to or from the atmosphere are equal. To quantify the decline of the forest, geographical studies and satellite imagery were used. Comparing the area covered by forest in the same region at two distinct eras allowed researchers to determine the annual rate of change. The outcome showed that tree cover loss (TCL, kg/ha) was decreased in 18 local government regions (LGAs). As a result, throughout the baseline consideration period of 2010 to 2022, Etasko East (EE) and Estako West (ES), Ovia South East (OSW), and Ovia North have had the least loss in tree cover. The increased demand on human survival brought on by the expanding population may provide an explanation for this observation and discovery. As a result of this development, forests underwent transformation and were used to produce food, build cities and homes, and generate energy. The region with the highest rates of tree cover loss and deforestation was associated with the highest CS, which was calculated at 2700 tC/ha at OSW, and the lowest CS value point at 22.2 tC/ha at Oredo Edo (OE). As a result, OSW showed that dense forests had higher biomass carbon storage than grazing land and open forests. In conclusion, the study showed that Edo State has a significant potential for raising the level of carbon sequestration in order for the state to generate a profit from the sale of carbon stock and enhance climate change mitigation efforts. [ABSTRACT FROM AUTHOR]

Climate change mitigation requires, besides reductions in greenhouse gas emissions, actions to increase carbon sinks in terrestrial ecosystems. A key measurement method for quantifying such sinks and calibrating models is the eddy covariance technique, but it requires imputation, or gap-filling, of missing data for determination of annual carbon balances of ecosystems. Previous comparisons of gap-filling methods have concluded that commonly used methods, such as marginal distribution sampling (MDS), do not have a significant impact on the carbon balance estimate. By analyzing an extensive, global data set, we show that MDS causes significant carbon balance errors for northern (latitude > 60 ∘ ) sites. MDS systematically overestimates the carbon dioxide (CO 2 ) emissions of carbon sources and underestimates the CO 2 sequestration of carbon sinks. We also reveal reasons for these biases and show how a machine learning method called extreme gradient boosting or a modified implementation of MDS can be used to substantially reduce the northern site bias. [ABSTRACT FROM AUTHOR]

Climate change mitigation requires, besides reductions in greenhouse gas emissions, actions to increase carbon sinks in terrestrial ecosystems. A key measurement method for quantifying such sinks and calibrating models is the eddy covariance technique, but it requires imputation, or gap-filling, of missing data for determination of annual carbon balances of ecosystems. Previous comparisons of gap-filling methods have concluded that commonly used methods, such as marginal distribution sampling (MDS), do not have a significant impact on the carbon balance estimate. By analyzing an extensive, global data set, we show that MDS causes significant carbon balance errors for northern (latitude > 60 ∘ ) sites. MDS systematically overestimates the carbon dioxide (CO 2 ) emissions of carbon sources and underestimates the CO 2 sequestration of carbon sinks. We also reveal reasons for these biases and show how a machine learning method called extreme gradient boosting or a modified implementation of MDS can be used to substantially reduce the northern site bias. [ABSTRACT FROM AUTHOR]

Carbon sequestration can also occur as alkalinity, dissolved inorganic and organic carbon (DIC and DOC) as well as detritus export beyond the habitat where carbon is fixed. Aquatic carbon sequestration refers to the long-term (century-scale) storage of atmospheric carbon in sediments, biomass and/or water. GLO:4D9/02nov22:lno12268-fig-0001.jpg PHOTO (COLOR): 1 Blue carbon ecosystems (mangroves, saltmarshes, seagrass meadows, and kelp forests) are carbon sequestration hotspots. A faster turnover of contemporary autochthonous organic carbon ("fast carbon") than old allochthonous organic carbon ("slow carbon") revealed a decoupling between carbon burial and anthropogenic CO SB 2 sb emissions. [Extracted from the article]

Mangrove forests are important carbon sinks, and this is especially true for Indonesia where about 24% of the world's mangroves exist. Unfortunately, vast expanses of these mangroves have been deforested, degraded or converted to other uses resulting in significant greenhouse gas emissions. The objective of this study was to quantify the climate change mitigation potential of mangrove conservation and restoration in Indonesia. We calculated the emission factors from the dominant land uses in mangroves, determined mangrove deforestation rates and quantified the total emissions and the potential emission reductions that could be achieved from mangrove conservation and restoration. Based on our analysis of the carbon stocks and emissions from land use in mangroves we found: (1) Indonesia's mangrove ecosystem carbon stocks are among the highest of any tropical forest type; (2) mangrove deforestation results in greenhouse gas emissions that far exceed that of upland tropical deforestation; (3) in the last decade the rates of deforestation in Indonesian mangroves have remained high; and (4) conservation and restoration of mangroves promise to sequester significant quantities of carbon. While mangroves comprise only ≈2.6% of Indonesia's total forest area, their degradation and deforestation accounted for ≈10% of total greenhouse gas emissions arising from the forestry sector. The large source of greenhouse gas emissions from a relatively small proportion of the forest area underscores the value for inclusion of mangroves as a natural climate solution. Mangrove conservation is far more effective than mangrove restoration in carbon emissions reductions and an efficient pathway to achieve Indonesia's nationally determined contribution (NDC) targets. The potential emission reduction from halting deforestation of primary and secondary mangroves coupled with restoration activities could result in an emission reduction equivalent to 8% of Indonesia's 2030 NDC emission reduction targets from the forestry sector. [ABSTRACT FROM AUTHOR]

• The 57.00% of the Yangtze River Economic Belt area exhibited a significant increase in annual NPP. • The response of NPP on climate factors was nonlinear, with greater sensitivity to temperature. • The impact of topographic factors on NPP changes had a threshold effect. Net primary productivity (NPP) of terrestrial ecosystems serves as a crucial carbon sink, playing a significant role in mitigating climate change. This study, focusing on the Yangtze River Economic Belt (YREB), a key area for both economic development and ecological conservation in China, evaluates the temporal and spatial changes in regional NPP and its responses to climatic factors against the backdrop of global change. Utilizing long-term NPP and meteorological grid data from 1981 to 2017, we analyzed the annual change patterns of NPP and its linear and nonlinear responses to climatic factors using copula functions. Our findings indicate that 57.00 % of the YREB has experienced a significant increase in NPP, with the most substantial decreases observed in Shanghai and its surrounding areas (P < 0.05). Temperature emerged as the primary climatic driver, positively correlating with NPP changes in over half of the study area (P < 0.05). Moreover, the nonlinear response of NPP to temperature and precipitation underscores the complex interactions between these factors, revealing a sensitivity to temperature variations that surpasses that to precipitation. The study also highlights the influence of solar radiation and topographic factors, with a significant positive correlation between NPP and solar radiation observed in 15.85 % of the area (P < 0.05). The practical significance of these findings lies in their implications for regional ecological management and climate resilience strategies. The positive correlation between temperature and NPP underscores the potential for targeted temperature management to optimize carbon sequestration across the YREB. Furthermore, the identified nonlinear responses and the role of solar radiation and topography in influencing NPP offer valuable insights for the formulation of adaptive strategies that enhance ecosystem productivity and contribute to achieving carbon neutrality goals. By elucidating the dynamics of NPP in response to a range of environmental factors, this study provides a foundation for informed decision-making in ecological conservation and climate change mitigation efforts within the YREB and similar regions globally. [ABSTRACT FROM AUTHOR]

The atmospheric concentration of CO2 is steadily increasing and causing climate change. To achieve the Paris 1.5 or 2°C target, negative emission technologies must be deployed in addition to reducing carbon emissions. The ocean is a large carbon sink but the potential of marine primary producers to contribute to carbon neutrality remains unclear.Here we review the alterations to carbon capture and sequestration of marine primary producers (including traditional 'blue carbon' plants, microalgae and macroalgae) in the Anthropocene, and, for the first time, assess and compare the potential of various marine primary producers to carbon neutrality and climate change mitigation via biogeoengineering approaches.The contributions of marine primary producers to carbon sequestration have been decreasing in the Anthropocene due to the decrease in biomass driven by direct anthropogenic activities and climate change. The potential of blue carbon plants (mangroves, saltmarshes and seagrasses) is limited by the available areas for their revegetation. Microalgae appear to have a large potential due to their ubiquity but how to enhance their carbon sequestration efficiency is very complex and uncertain. On the other hand, macroalgae can play an essential role in mitigating climate change through extensive offshore cultivation due to higher carbon sequestration capacity and substantial available areas. This approach seems both technically and economically feasible due to the development of offshore aquaculture and a well‐established market for macroalgal products.Synthesis and applications. This paper provides new insights and suggests promising directions for utilizing marine primary producers to achieve the Paris temperature target. We propose that macroalgae cultivation can play an essential role in attaining carbon neutrality and climate change mitigation, although its ecological impacts need to be assessed further. [ABSTRACT FROM AUTHOR]

Terrestrial ecosystems play a critical role in the global carbon cycle and climate change mitigation. Studying the temporal and spatial dynamics of carbon sink and the driving mechanisms at the regional scale provides an important basis for ecological restoration and ecosystem management. Taking the Dongting Lake Basin as an example, we assessed the carbon sinks of forest and shrub from 2000 to 2020 based on the maps of biomass that were obtained by remote sensing, and analyzed the dynamics of carbon sinks that were contributed by different biomass carbon density levels of constant forest and shrub and new afforestation over the past two decades. The results showed that the carbon sink of forest and shrub in the Dongting Lake Basin grew rapidly from 2000 to 2020: carbon sink increased from 64.64 TgC between 2000 and 2010, to 382.56 TgC between 2010 and 2020. The continuous improvement of biomass carbon density has made a major contribution to carbon sink, especially the carbon density increase in low carbon density forests and shrubs. Carbon-dense forests and shrubs realized their contribution to carbon sink in the second decade after displaying negative carbon sink in the first decade. Carbon sink from new afforestation increased 61.16% from the first decade to the second decade, but the contribution proportion decreased. The overall low carbon density of forest and shrub in the Dongting Lake Basin and their carbon sink dynamics indicated their huge carbon sequestration potential in the future. In addition to continuously implementing forest protection and restoration projects to promote afforestation, the improvement of ecosystem quality should be paid more attention in ecosystem management for areas like Dongting Lake Basin, where ecosystems, though severely degraded, are important and fragile, to realize their huge carbon sequestration potential. [ABSTRACT FROM AUTHOR]

The cultivation of deep-rooted vegetation greatly alters the tradeoffs between water and carbon dynamics, yet their impact on microbial carbon sequestration (MCS) remains inadequately documented, particularly in thick vadose zones. This information is crucial for global climate mitigation and ecosystem service enhancement. As such, we collected triplicate samples for each land use type, exploring the abundance and structure of cbbL -harboring microbial communities within 10-m deep profiles under cultivated farmland and two apple orchards of varying ages (n = 72). Our findings indicated a shift from water-dominated (improved water retention at the expense of reduced carbon sequestration) to carbon-dominated benefits (enhanced carbon sequestration at the expense of decreased water retention) in deep soil layers (2–10 m) after the transformation from farmland to apple orchards. Despite the lack of significant differences among the three land use types, the gene abundances and microbial diversity indices reduced with soil depths because of variations in substrates, resources, and microenvironments. The cbbL -harboring microorganisms consisted of 5 phyla, 7 classes, 19 orders, 30 families, and 55 genera, with Proteobacteria as the predominant bacterial phylum. The relative contributions of different genera varied with soil depths, reflecting their distinct survival strategies. The microbial network was positively connected in various soil layers under farmland and apple orchards. Furthermore, the results of correlation, redundancy analysis, and structural equation modeling jointly indicated that plant roots and soil properties, including total nitrogen and organic carbon, governed MCS processes in deep unsaturated zones. Specifically, the low microbial variation between farmland and apple orchards can be attributed to the predominant effects of climatic and pedogenic factors on soil properties, the restricted contribution of plant roots to soil nutrient levels per unit depth, and the adverse effects of plant-induced ecohydrological consequences on root systems and microbial populations. This study offers new insights within thick vadose zones containing deep-rooted plants, thereby contributing to a better understanding of global terrestrial carbon cycle processes. [Display omitted] • Microbial carbon sequestration processes were explored in 10-m deep profiles. • The farmland-to-apple orchards conversion led to water-carbon tradeoffs. • Microbial carbon sequestration differed with depths rather than land use types. • Depth-dependent plant roots and soil nutrients affects carbon sequestration. [ABSTRACT FROM AUTHOR]

Non-native species are expanding globally and can alter ecosystem functions, including food web dynamics, community structure and carbon storage. Seagrass are foundation species that contribute a variety of ecosystem services in near-shore coastal ecosystems, including a significant sink of carbon. In the Caribbean, the rapidly expanding non-native Halophila stipulacea has unknown impacts on carbon storage. To investigate the impacts on carbon storage, we quantified organic carbon (C org) content in sediment and seagrass tissues from monotypic H. stipulacea beds, mixed native seagrass beds dominated by Thalassia testudinum and Syringodium filiforme, and unvegetated substrate in St. John, USVI. We found native seagrass-vegetated sediment contained 1.3 times more C org than sediment covered by H. stipulacea , and 1.6 times more C org than unvegetated areas on average. Whereas, H. stipulacea -dominated substrate stored 1.2 times more C org than unvegetated substrate. Likewise, native species contained 2.2 times more aboveground biomass and 6.0 times more belowground biomass than H. stipulacea. Since seagrasses are critical sources of carbon sequestration, our results suggest that invading H. stipulacea is associated with lower carbon stocks which has potential implications for conservation activities and climate change mitigation. [Display omitted] • Non-native species are expanding globally and can alter ecosystem functions. • Our results suggest that invading H. stipulacea is associated with lower carbon stocks. • In the Caribbean, rapidly expanding Halophila stipulacea may reduce carbon storage. [ABSTRACT FROM AUTHOR]

Bioenergy has been identified as a key component of climate change mitigation. Therefore, quantifying the net carbon balance of bioenergy feedstocks is crucial for accurate projections of climate mitigation benefits. Switchgrass (Panicum virgatum) has many characteristics of an ideal bioenergy crop with high yields, low maintenance, and deep roots with potential for belowground carbon sequestration. However, the assessments of net annual carbon exchange between switchgrass fields and the atmosphere are rare. Here we present observations of net carbon fluxes in a minimally managed switchgrass field in Virginia (Ameriflux site US‐SB2) over 5 years (3–7 years since establishment). Average annual net ecosystem exchange (NEE) of carbon was near zero (60 g C m−2 year−1) but the net ecosystem carbon balance that includes harvested carbon (HC) was a net source of carbon to the atmosphere (313 g C m−2 year−1). The field alternated between a large and small source of carbon annually, with the interannual variability most strongly correlated with the day of the last frost and the interaction of temperature and precipitation. Overall, the consistent source of carbon to the atmosphere at US‐SB2 differs substantially from other eddy covariance studies that report switchgrass fields to be either neutral or a sink of carbon when accounting for both NEE and HC. This study illustrates that predictions of net carbon climate benefits from bioenergy crops cannot assume that the ecosystem will be a net sink of carbon from the atmosphere. Background climate, management, and land‐use history may determine whether widespread deployment of switchgrass as a bioenergy feedstock results in realized climate change mitigation. [ABSTRACT FROM AUTHOR]

Carbon (C) cycling is being influenced by global climate change, which is altering the primary productivity and the rate at which carbon is fixed, released and stored in vegetation systems on Earth. Carbon sequestration is recognised as the storing of carbon dioxide (CO2) and other kinds of carbon for a long time. A selective atmospheric carbon-based anthropic enrichment causes an environmental catastrophe, which necessitates methods of mitigation. Algal primary production (which includes cyanobacterial algae, microalgal, and macroalgal) is a key pathway for C biosequestration in the ocean. Many scientists and environmental professionals are concerned about the rise in global temperatures and climate change. Increased quantity of carbon that can be absorbed from the atmosphere by exploiting the ability of plants, particularly seaweed, to use CO2 in process of photosynthesis is one of the key solutions being given to prevent the earth's rising temperature at a faster rate. The ability of ocean plants to act as a carbon sink from anthropogenic sources (also recognised as "Blue Carbon") has piqued people's interest. Marine primary producers are responsible for at least half of the earth's carbon uptake and up to 71 percent of all C storing. Seaweeds have important roles in the elemental cycles of coastal ecosystems, mostly through the export of organic matter to neighbouring communities and the accumulation of carbon and nutrients in the sediment. [ABSTRACT FROM AUTHOR]

Scenarios avoiding global warming greater than 1.5 or 2 ∘ C, as stipulated in the Paris Agreement, may require the combined mitigation of anthropogenic greenhouse gas emissions alongside enhancing negative emissions through approaches such as afforestation–reforestation (AR) and biomass energy with carbon capture and storage (BECCS). We use the JULES land surface model coupled to an inverted form of the IMOGEN climate emulator to investigate mitigation scenarios that achieve the 1.5 or 2 ∘ C warming targets of the Paris Agreement. Specifically, within this IMOGEN-JULES framework, we focus on and characterise the global and regional effectiveness of land-based (BECCS and/or AR) and anthropogenic methane (CH4) emission mitigation, separately and in combination, on the anthropogenic fossil fuel carbon dioxide (CO2) emission budgets (AFFEBs) to 2100. We use consistent data and socio-economic assumptions from the IMAGE integrated assessment model for the second Shared Socioeconomic Pathway (SSP2). The analysis includes the effects of the methane and carbon–climate feedbacks from wetlands and permafrost thaw, which we have shown previously to be significant constraints on the AFFEBs. Globally, mitigation of anthropogenic CH4 emissions has large impacts on the anthropogenic fossil fuel emission budgets, potentially offsetting (i.e. allowing extra) carbon dioxide emissions of 188–212 Gt C. This is because of (a) the reduction in the direct and indirect radiative forcing of methane in response to the lower emissions and hence atmospheric concentration of methane and (b) carbon-cycle changes leading to increased uptake by the land and ocean by CO2 -based fertilisation. Methane mitigation is beneficial everywhere, particularly for the major CH4 -emitting regions of India, the USA, and China. Land-based mitigation has the potential to offset 51–100 Gt C globally, the large range reflecting assumptions and uncertainties associated with BECCS. The ranges for CH4 reduction and BECCS implementation are valid for both the 1.5 and 2 ∘ C warming targets. That is the mitigation potential of the CH4 and of the land-based scenarios is similar for regardless of which of the final stabilised warming levels society aims for. Further, both the effectiveness and the preferred land management strategy (i.e. AR or BECCS) have strong regional dependencies. Additional analysis shows extensive BECCS could adversely affect water security for several regions. Although the primary requirement remains mitigation of fossil fuel emissions, our results highlight the potential for the mitigation of CH4 emissions to make the Paris climate targets more achievable. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is the largest carbon sink in terrestrial ecosystems and plays a critical role in mitigating climate change. Increasing reactive nitrogen (N) in ecosystems caused by anthropogenic N input substantially affects SOC dynamics. However, uncertainties remain concerning the effects of N addition on SOC in both organic and mineral soil layers over time at the global scale. Here, we analysed a large empirical data set spanning 60 years across 369 sites worldwide to explore the temporal dynamics of SOC to N addition. We found that N addition significantly increased SOC across the globe by 4.2% (2.7%–5.8%). SOC increases were amplified from short‐ to long‐term N addition durations in both organic and mineral soil layers. The positive effects of N addition on SOC were independent of ecosystem types, mean annual temperature and precipitation. Our findings suggest that SOC increases largely resulted from the enhanced plant C input to soils coupled with reduced C loss from decomposition and amplification was associated with reduced microbial biomass and respiration under long‐term N addition. Our study suggests that N addition will enhance SOC sequestration over time and contribute to future climate change mitigation. [ABSTRACT FROM AUTHOR]

This research aimed to understand how Protected Areas act for the adaptation and mitigation of climate change. The state of Mato Grosso, located in the center-west of Brazil, was analysed as it is a state of large dimensions and with different biomes in its composition. A case study was carried out in order to dimension the importance of PAs in dealing with the sequestration of Greenhouse Gases (GHG), using the state of Mato Grosso. From the literature review, it was identified that the Protected Areas are a mitigating instrument for climate change, since conservation maintains ecosystem services and helps in the capture and storage of carbon dioxide, called carbon sinks. Through a legal analysis, it was found that the environmental policies of Protected Areas do not materially establish climate change as a basis. The data obtained showed that 4.73% of the state area under study fits into this legal instrument. Despite corresponding to a small territorial parcel, the Protected Areas are spread over the three biomes that make up the state, in the search to protect the three different biodiversity. From the analysis of the data, it is concluded that the Protected Areas have a mitigating role for climate change in the state of Mato Grosso, due to Land Use Change, a factor of great incidence in the state. For further research, it is suggested to analyse the relevance of indigenous areas in this same scenario. [ABSTRACT FROM AUTHOR]

Marine vegetated ecosystems such as seagrass meadows are increasingly acknowledged as important carbon sinks based on their ability to capture and store atmospheric carbon dioxide, thereby contributing to climate change mitigation. Most studies on carbon storage in marine ecosystems have focused on organic carbon, leaving inorganic carbon processes such as calcification unaccounted for, despite of their critical role in the global carbon budget. This is probably because of uncertainties regarding the role of calcification in marine carbon budgets as either atmospheric CO2 source or sink. Here, we conducted a laboratory experiment to investigate the influence of a calcifying alga (Corallina officinalis L.) on seawater carbon content, using a non-calcifying alga (Ulva lactuca L.) as a control. In a first part, algae were incubated separately while measuring changes in seawater pH, total alkalinity (TA) and total dissolved inorganic carbon (DIC). The amount of carbon used in photosynthetic uptake and production of CaCO3 was then calculated. In a second, directly following, part the algae were removed and DIC levels were allowed to equilibrate with air until the pH stabilized and the loss of CO2 to air was calculated as the difference in total DIC from the start of part one, to the end of the second part. The results showed that C. officinalis caused a significant and persistent reduction in total dissolved inorganic carbon (DIC), TA and seawater pH, while no such permanent changes were caused by U. lactuca. These findings indicate that calcification can release a significant amount of CO2 to the atmosphere and thereby possibly counteract the carbon sequestration in marine vegetated ecosystems if this CO2 is not re-fixed in the system. Our research emphasises the importance of considering algal calcification in future assessments on carbon storage in coastal areas. [ABSTRACT FROM AUTHOR]

Annual carbon estimation of the most diverse ecosystems is a recurring theme in meetings that address climate change mitigation, as it is essential to have a realistic inventory of carbon stock in the biosphere and the ability to assimilate atmospheric carbon. Measurements of CO2 flux over ecosystems after being taken undergo rigorous post-processing to remove spurious and unrealistic data. In addition, a correction for low turbulence situations, where the eddy-covariance technique may be underestimated, is to take the friction velocity (u *) as a threshold to establish valid measurements, especially at night. This method, although widely used by the scientific community, is not unanimous. Especially since u * is itself a flow and consequently its value correlates with the time scale used for the analysis. This paper presents the annual carbon estimate of a natural pasture ecosystem, Pampa biome, in an experimental site established in Santa Maria - RS. We evaluated three distinct situations in the annual carbon estimate (NEP): i) without au * filter; ii) with a fixed filter u * for all evaluated years and; iii) with the filter u * varying seasonally. The methodology used to estimate u * is the same as that used by Papale et al. (2006). The results show a total annual carbon sequestration variability of up to 10% depending on the methodology employed. The ecosystem in question, regardless of the method used, proved to be a carbon sink. However, the use of one methodology or another in ecosystem situations that are close to carbon assimaltion neutral should be closely scrutinized for an accurate annual balance. Pampa biome, in an experimental site established in Santa Maria - RS. We evaluated three distinct situations in the annual carbon estimate (NEP): i) without au * filter; ii) with a fixed filter u * for all evaluated years and; iii) with the filter u * varying seasonally. The methodology used to estimate u * is the same as that used by Papale et al. (2006). The results show a total annual carbon sequestration variability of up to 10% depending on the methodology employed. The ecosystem in question, regardless of the method used, proved to be a carbon sink. However, the use of one methodology or another in ecosystem situations that are close to carbon assimaltion neutral should be closely scrutinized for an accurate annual balance. Pampa biome, in an experimental site established in Santa Maria - RS. We evaluated three distinct situations in the annual carbon estimate (NEP): i) without au * filter; ii) with a fixed filter u * for all evaluated years and; iii) with the filter u * varying seasonally. The methodology used to estimate u * is the same as that used by Papale et al. (2006). The results show a total annual carbon sequestration variability of up to 10% depending on the methodology employed. The ecosystem in question, regardless of the method used, proved to be a carbon sink. However, the use of one methodology or another in ecosystem situations that are close to carbon assimaltion neutral should be closely scrutinized for an accurate annual balance. We evaluated three distinct situations in the annual carbon estimate (NEP): i) without au * filter; ii) with a fixed filter u * for all evaluated years and; iii) with the filter u * varying seasonally. The methodology used to estimate u * is the same as that used by Papale et al. (2006). The results show a total annual carbon sequestration variability of up to 10% depending on the methodology employed. The ecosystem in question, regardless of the method used, proved to be a carbon sink. However, the use of one methodology or another in ecosystem situations that are close to carbon assimaltion neutral should be closely scrutinized for an accurate annual balance. We evaluated three distinct situations in the annual carbon estimate (NEP): i) without au * filter; ii) with a fixed filter u * for all evaluated years and; iii) with the filter u * varying seasonally. The methodology used to estimate u * is the same as that used by Papale et al. (2006). The results show a total annual carbon sequestration variability of up to 10% depending on the methodology employed. The ecosystem in question, regardless of the method used, proved to be a carbon sink. However, the use of one methodology or another in ecosystem situations that are close to carbon assimaltion neutral should be closely scrutinized for an accurate annual balance. The methodology used to estimate u * is the same as that used by Papale et al. (2006). The results show a total annual carbon sequestration variability of up to 10% depending on the methodology employed. The ecosystem in question, regardless of the method used, proved to be a carbon sink. However, the use of one methodology or another in ecosystem situations that are close to carbon assimaltion neutral should be closely scrutinized for an accurate annual balance. The methodology used to estimate u * is the same as that used by Papale et al. (2006). The results show a total annual carbon sequestration variability of up to 10% depending on the methodology employed. The ecosystem in question, regardless of the method used, proved to be a carbon sink. However, the use of one methodology or another in ecosystem situations that are close to carbon assimaltion neutral should be closely scrutinized for an accurate annual balance. [ABSTRACT FROM AUTHOR]

Terrestrial ecosystems store more carbon (C) than the atmosphere and provide ecosystem services (ES) such as global climate regulation, by sequestering carbon within biomass and soil. Land use land cover (LULC) change is considered a key factor, playing an important role in the dynamic variations of carbon storage. The aim of this paper is to assess the effects that LULC has had on carbon stocks and consequently on climate change regulation in north-western Morocco over 21 years. To achieve this aim, the Integrated Valuation of ES and Trade-offs (InVEST) model is used to assess status and variation in the net amount of carbon stored by the different types of LULC, and the economic value of the carbon sequestered in the remaining stock. The results show that the total carbon stock increased from 4.81TgC in 1996 to 4.98TgC in 2017. Over the 21 years, the LULC changes had the greatest effect on carbon storage - an increase of 6.87% with 0.17TgC of carbon sequestered, since the majority of unused land was changed to forest and cultivated land. Based on the global costs of atmospheric carbon, we estimate the economic value of carbon storage services to be between US$1,800,000 and US$3,570,000 for the whole period, with an average yearly increment of between US$86,000 and US$170,000. The results show that the ecosystem management has had a substantial climate mitigation effect. Also, the possibility of paying for ES could inform policy on the adoption of LULC to support livelihood and management choices. [ABSTRACT FROM AUTHOR]

Knowledge on relationship and determinants of water and carbon dioxide (CO 2) exchange is crucial to land managers and policy makers especially for the desertified land restoration. However, there remains highly uncertain in terms of water use and carbon sequestration for artificial plantation in desert. Here, continuous water and carbon fluxes were measured using eddy covariance (EC) in conjunction with hydrometeorological measurements over an artificial C4 shrub, Haloxylon ammodendron (C. A. Mey.) Bunge, from July 2020 to 2021 in Tengger Desert, China. Throughout 2021, evapotranspiration (ET) was 189.5 mm, of which 85% (150 mm) occurred during growing season, that was comparable with the summation of precipitation (132.2 mm), dew (33.5 mm) and potential other sources (e.g. deep subsoil water). This ecosystem was a strong carbon sink with net ecosystem production (NEP) up to 446.4 g C m−2 yr−1, much higher than surrounding sites. Gross primary production (GPP, 598.7 g C m−2 yr−1) in this shrubland was comparable with that of other shrublands, whereas ecosystem respiration (Re, 152.3 g C m−2 yr−1) was lower. Random Forest showed that environmental factors can explain 71.56% and 80.07% variation of GPP and ET, respectively. Interestingly, environmental factors have divergent effect on water and carbon exchange, i.e., soil hydrothermic factors (soil moisture content and soil temperature) determine the magnitude and seasonal pattern of ET and Re, while aerodynamics factors (net radiation, atmospheric temperature and wind speed) determine GPP and NEP. As such, divergent response of abiotic factors resulted in the decoupling of water and carbon exchange. Our results suggest that H. ammodendron is a suitable species for large-scale afforestation in dryland given its low water use but high carbon sequestration. Therefore, we infer that artificial planting H. ammodendron in dryland could provide an opportunity for climate change mitigation, and the long-term time series data is needed to confirm its sustainable role of carbon sequestration in the future. • Water and carbon exchange over an artificial C4 shrub in desert were determined. • Evapotranspiration (ET) was comparable with precipitation plus dew. • Positive and high net ecosystem production (NEP) suggest the strong carbon sink for it. • Gross primary production (GPP) was comparable with other shrubs but ecosystem respiration lower. • Abiotic factors have divergent effects on water (ET) and carbon fluxes (NEP and GPP). [ABSTRACT FROM AUTHOR]

Abstract Assessing the status of important carbon sinks such as seagrass meadows is of primary importance when dealing with potential climate change mitigation strategies. This study examined plant and sediment properties in seagrass meadows (Cymodocea nodosa (Ucria) Asch.) from two high p CO 2 –low pH Mediterranean vent systems, located at Milos (Greece) and Vulcano (Italy) Islands, providing insights on carbon storage potential in future acidified oceans. Contrary to what has been suggested, carbon content (both inorganic and organic) and its surficial accumulation decreased at high p CO 2 –low pH in comparison with controls. The decrease in inorganic carbon may result from the higher solubility of carbonates due to the more acidic conditions. At Vulcano, the seagrass properties (e.g. , leaf area, biomass) appeared negatively affected by environmental conditions at high p CO 2 –low pH conditions and this may have had a detrimental effect on the organic carbon content and accumulation. At Milos, organic carbon decreased at high p CO 2 –low pH conditions, despite the increase in seagrass aboveground biomass, leaf length and area, probably as a consequence of site-specific features, which need further investigation and may include both biotic and abiotic factors (e.g., oligotrophic conditions, decreased sedimentation rate and input of allochthonous material). Results suggest that, in contrast to previous predictions based exclusively on the expected positive response of seagrasses to ocean acidification, carbon storage capacity of the seagrass C. nodosa may not increase at high p CO 2 -low pH conditions. This study emphasizes the need to investigate further the potential alteration in the climate mitigation service delivered by seagrass meadows in acidified oceans. Highlights • Seagrass features differed between control and low pH stations inconsistently in the two vents. • Carbon content and its surficial accumulation decreased at high p CO 2 –low pH conditions. • Carbon storage capacity of the seagrass may not increase at high p CO 2 -low pH conditions. [ABSTRACT FROM AUTHOR]

Seagrass meadows are 'blue carbon' ecosystems widely recognised for their potential role in climate change mitigation. Previous studies have focused mainly on carbon storage within meadows and sediments. However, little is known about contribution of outwelling (i.e., lateral transport) to seagrass carbon budgets. Here, radium isotopes (223Ra and 224Ra) were used to assess dissolved inorganic carbon (DIC) and total alkalinity (TA) outwelling from a Mediterranean Posidonia oceanica meadow during early autumn. DIC outwelling was 114 ± 61 mmol m−2 day−1 and exceeded above-meadow CO 2 outgassing (3 ± 1 mmol m−2 day−1). Production of DIC was uncoupled from TA and fuelled by net heterotrophy and aerobic processes within the meadow. The small export of TA (5 ± 6 mmol m−2 day−1) implied that ∼90% of outwelled DIC may return to the atmosphere as CO 2 in offshore waters. Combining these fluxes with above-meadow outgassing suggested a total carbon loss that exceeded long term burial in sediments. Overall, the meadow acted as a carbon source to the atmosphere during the early autumn season. Further studies quantifying outwelling at multiple spatial and temporal scales are required to better resolve seagrass carbon budgets and their contribution to carbon sequestration. • Radium isotopes enabled calculation of mixing rates and outwelling fluxes. • Dissolved inorganic carbon outwelling exceeded above-meadow CO 2 outgassing. • Production of dissolved inorganic carbon and alkalinity was uncoupled. • Most of the outwelled dissolved inorganic carbon may return to the atmosphere offshore. • Dissolved inorganic carbon may be a significant component of seagrass carbon budgets. [ABSTRACT FROM AUTHOR]

Rational allocation of carbon quotas is the fundamental premise for the orderly operation of carbon markets. To achieve the set target of carbon peak by 2030, there is an urgent need to establish China's 2030 provincial carbon quota allocation scheme. Although some proposed schemes have been formulated, there are problems with the methods used for carbon emission forecasting and evaluating the rationality of a proposed allocation scheme. This study aimed to optimize carbon emission forecast by incorporating terrestrial carbon sinks into the mechanism for building China's 2030 provincial carbon emission quota allocation schemes. Aquila Optimizer's Double Support Vector Regression (AO-based TWSVR) that has the advantages in solving problems associated with small sample size, nonlinear and high-dimensional pattern recognition with fast training speed and insensitivity to noise was adopted to predict the net carbon emission. The results show that the application of AO-based TWSVR model allows satisfactory forecast of the net carbon emission in China for the period from 2021 to 2035. This allowed terrestrial carbon sequestration being incorporated into the mechanism to formulate China's 2030 provincial carbon quota allocation schemes. Comparison of the three provincial carbon quota allocation schemes using social network analysis suggests that the equity-based carbon quota allocation scheme is more suitable for China's national conditions compared to the efficiency-based scheme and the combined principle-based scheme. The findings obtained from this study have implications for optimizing the scheme of China's 2030 provincial carbon quota allocation. [Display omitted] • AO-based TWSVR model was used to optimize carbon emission forecasting in China. • This allows satisfactory forecast of the net carbon emission from 2021 to 2035. • Three schemes were formulated for China's 2030 provincial carbon quota allocation. • Social network analysis was used to evaluate the rationality of these schemes. • The equity-based scheme is more suitable for China's national conditions. [ABSTRACT FROM AUTHOR]

• Large uncertainties are associated with the future magnitude and stability of the forest carbon sink. • Business-as-usual management practices might already be close-to-optimum for supporting forest carbon uptake and storage. • Increases in management intensity have the potential to lower forest carbon sequestration and stocking capacity. • Forest management practices are as important as climate change to regulatethe carbon sink and stock size. Forest management practices might act as nature-based methods to remove CO 2 from the atmosphere and slow anthropogenic climate change and thus support an EU forest-based climate change mitigation strategy. However, the extent to which diversified management actions could lead to quantitatively important changes in carbon sequestration and stocking capacity at the tree level remains to be thoroughly assessed. To that end, we used a state-of-the-science bio-geochemically based forest growth model to simulate effects of multiple forest management scenarios on net primary productivity (NPP) and potential carbon woody stocks (pCWS) under twenty scenarios of climate change in a suite of observed and virtual forest stands in temperate and boreal European forests. Previous modelling experiments indicated that the capacity of forests to assimilate and store atmospheric CO 2 in woody biomass is already being attained under business-as-usual forest management practices across a range of climate change scenarios. Nevertheless, we find that on the long-term, with increasing atmospheric CO 2 concentration and warming, managed forests show both higher productivity capacity and a larger potential pool size of stored carbon than unmanaged forests as long as thinning and tree harvesting are of moderate intensity. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A 500 MW e oxy-coal power plant (PP) with CO 2 capture and storage (CCS) was considered. • 5% CO 2 emitted from the PP can be methanized using surplus electricity from renewables. • 80 % replacement by the PP with CCS contributed to lower 0.09 °C of global temperature. • Realistic implementation of coal PPs with CCS using renewable energy was provided. CO 2 -free power plants (PPs) with renewable electricity have promising sustainability implications, but the impact of their widespread use is yet to be determined. Here, the effect of an oxy-coal PP equipped with CO 2 capture, water electrolysis, and CO 2 methanation on electricity efficiency, CO 2 emission rate, CO 2 capture cost, and global surface temperatures (T g) was investigated. By exploiting surplus electricity from renewable sources for electrolysis, we estimated that 5 % of the CO 2 emitted from the coal PP was methanized. The process flow diagram of a 500 MW e decarbonized oxy-coal PP was constructed and its impact on energetic, economic, and environmental values was evaluated. The results were applied to a model of the global carbon cycle to predict T g considering the prospective global population and carbon emission rate (r ff) of fossil fuels by 2050. An 80 % replacement of conventional coal PPs worldwide by decarbonized oxy-coal PPs contributed to reducing r ff by 6.1 Gt CO2 /y in 2050 and lowering T g by 0.09 °C. The additional capital cost to replace 80 % of conventional coal PPs with decarbonized oxy-coal PPs, including associated geological storage costs, was estimated to be $43/t CO2. This study elucidates the promise and limitations of coal PPs designed for CO 2 capture, utilization, and storage (CCUS). Combining CCUS technologies with global warming estimates can be extended to examine the economic and climatic impact of CCUS under various CO 2 emission sources. [ABSTRACT FROM AUTHOR]

Globally, 15.5 million km of land are currently identified as protected areas, which provide society with many ecosystem services including climate-change mitigation. Combining a global database of protected areas, a reconstruction of global land-use history, and a global biogeochemistry model, we estimate that protected areas currently sequester 0.5 Pg C annually, which is about one fifth of the carbon sequestered by all land ecosystems annually. Using an integrated earth systems model to generate climate and land-use scenarios for the twenty-first century, we project that rapid climate change, similar to high-end projections in IPCC's Fifth Assessment Report, would cause the annual carbon sequestration rate in protected areas to drop to about 0.3 Pg C by 2100. For the scenario with both rapid climate change and extensive land-use change driven by population and economic pressures, 5.6 million km of protected areas would be converted to other uses, and carbon sequestration in the remaining protected areas would drop to near zero by 2100. [ABSTRACT FROM AUTHOR]

Biomass combustion is considered to be carbon neutral, but intensive biomass harvesting may negatively impact carbon stocks in forest soil and vegetation, which can offset the benefits of substituting fossil fuels with biomass. Here we evaluated conventional stem-only harvesting, whole-tree harvesting (WTH), and WTH excluding needles in terms of timber yield, biomass harvests, and forest carbon sequestration. We simulated harvest scenarios in current and changed climates with a process-based growth model (PipeQual) that was integrated with models describing soil decomposition (ROMUL) and soil water dynamics. Furthermore, we compared gains and losses of forest carbon with reductions in fossil-fuel emissions that result from using harvested biomass for energy production. WTH negatively affected stand growth, biomass, and soil carbon stock; negative effects on growth and biomass can be reduced by leaving nitrogen-rich needles behind during WTH. In a changed climate, organic-matter decomposition and nitrogen mineralization accelerated and tree growth was enhanced, increasing the carbon stock of trees and slightly decreasing the soil carbon stock. In the changed climate, WTH had less influence on forest growth and a similar influence on soil carbon sequestration than in the current climate. In the current climate, the WTH decreased the forest carbon stock by, on average, 26.8 Mg C·ha−1 over the rotation period. If harvested forest residues are used for energy production instead of fossil fuels, emissions decline by 19 Mg C·ha−1 (when WTH is applied over a rotation period). Thus, our analysis suggests that using forest residues for energy production leads to a net increase in carbon emissions. [ABSTRACT FROM AUTHOR]

When assessing soil organic carbon (SOC) sequestration and its climate change (CC) mitigation potential at global scale, the dynamic nature of soil carbon storage and interventions to foster it should be taken into account. Firstly, adoption of SOC-sequestration measures will take time, and reasonably such schemes could only be implemented gradually at large-scale. Secondly, if soils are managed as carbon sinks, then SOC will increase only over a limited time, up to the point when a new SOC equilibrium is reached. This paper combines these two processes and predicts potential SOC sequestration dynamics in agricultural land at global scale and the corresponding CC mitigation potential. Assuming that global governments would agree on a worldwide effort to gradually change land use practices towards turning agricultural soils into carbon sinks starting 2014, the projected 87-year (2014-2100) global SOC sequestration potential of agricultural land ranged between 31 and 64 Gt. This is equal to 1.9-3.9% of the SRES-A2 projected 87-year anthropogenic emissions. SOC sequestration would peak 2032-33, at that time reaching 4.3-8.9% of the projected annual SRES-A2 emission. About 30 years later the sequestration rate would have reduced by half. Thus, SOC sequestration is not a C wedge that could contribute increasingly to mitigating CC. Rather, the mitigation potential is limited, contributing very little to solving the climate problem of the coming decades. However, we deliberately did not elaborate on the importance of maintaining or increasing SOC for sustaining soil health, agro-ecosystem functioning and productivity; an issue of global significance that deserves proper consideration irrespectively of any potential additional sequestration of SOC. [ABSTRACT FROM AUTHOR]

The Sloping Land Conversion Program (SLCP), preferentially initiated to reduce water loss and soil erosion in the Loess Plateau of China in 1999, is the largest eco-restoration project in the world in recent decades. This massive effort improved the vegetation conditions markedly and was expected to have a great potential to enhance terrestrial carbon (C) sequestration. However, the spatially-explicit C consequences of the SLCP remain largely unknown at the regional scale. Using Ansai County in the Loess Plateau as a case study, we assessed the impacts of the SLCP on ecosystem C dynamics based on the General Ensemble Biogeochemical Modeling System (GEMS). The results showed that ecosystem C stock (including C stored in biomass and soil) decreased slightly in the first five years after the implementation of the SLCP (i.e., 1999-2003) due to the low production of the newly forested land, and increased evidently (mostly in biomass) thereafter thanks primarily to the growth of young plantations. Overall, the study area functioned as a net C sink in the past three decades, yet the magnitude was greatly amplified by the SLCP, indicated by a C sink in 2004-2010 nearly twelve times that in 1978-1998 (41.5 vs. 3.5 g C m-2 yr-1). These results highlight the importance of the SLCP in promoting terrestrial C sequestration which may help mitigate climate change. Nevertheless, there were time-lags between the impact of the SLCP and the associated C dynamics in the eco-restored areas, particularly in the soil, calling for future efforts toward addressing long-term C consequences of the SLCP. [ABSTRACT FROM AUTHOR]

The carbon cycle is one of the fundamental climate change issues. Its long-term evolution largely affects the amplitude and trend of human-induced climate change, as well as the formulation and implementation of emission reduction policy and technology for stabilizing the atmospheric CO concentration. Two earth system models incorporating the global carbon cycle, the Community Earth System Model and the Beijing Normal University-Earth System Model, were used to investigate the effect of the carbon cycle on the attribution of the historical responsibility for climate change. The simulations show that when compared with the criterion based on cumulative emissions, the developed (developing) countries' responsibility is reduced (increased) by 6 %-10 % using atmospheric CO concentration as the criterion. This discrepancy is attributed to the fact that the developed world contributed approximately 61 %-68 % (61 %-64 %) to the change in global oceanic (terrestrial) carbon sequestration for the period from 1850 to 2005, whereas the developing world contributed approximately 32 %-49 % (36 %-39 %). Under a developed world emissions scenario, the relatively larger uptake of global carbon sinks reduced the developed countries' responsibility for carbon emissions but increased their responsibility for global ocean acidification (68 %). In addition, the large emissions from the developed world reduced the efficiency of the global carbon sinks, which may affect the long-term carbon sequestration and exacerbate global warming in the future. Therefore, it is necessary to further consider the interaction between carbon emissions and the carbon cycle when formulating emission reduction policy. [ABSTRACT FROM AUTHOR]

The transformation of the natural landscape into an impervious surface due to urbanization has often been considered an important driver of environmental change, affecting essential urban ecological processes and ecosystem services. Continuous forest degradation and deforestation due to urbanization have led to an increase in atmospheric carbon emissions, risks, and impacts associated with climate change within urban landscapes and beyond them. Hence, urban reforestation has become a reliable long-term alternative for carbon sink and climate change mitigation. However, there is an urgent need for spatially accurate and concise quantification of these forest carbon stocks in order to understand and effectively monitor the accumulation and progress on such ecosystem services. Hence, this study sought to examine the prospect of Sentinel-2 spectral data in quantifying carbon stock in a reforested urban landscape using the random forest ensemble. Results show that Sentinel-2 spectral data estimated reforested forest carbon stock to an RMSE between 0.378 and 0.466 t·ha−1 and R2 of 79.82 and 77.96% using calibration and validation datasets. Based on random forest variable selection and backward elimination approaches, the red-edge normalized difference vegetation index, enhanced vegetation index, modified simple ratio index, and normalized difference vegetation index were the best subset of predictor variables of carbon stock. These findings demonstrate the value and prospects of Sentinel-2 spectral data for predicting carbon stock in reforested urban landscapes. This information is critical for adopting informed management policies and plans for optimizing urban reforested landscapes carbon sequestration capacity and improving their climate change mitigation potential. [ABSTRACT FROM AUTHOR]

[Display omitted] • We compared two valuation approaches to assess carbon sequestration ecosystem service. • The retired lands in the "Grain for Green" project was used as an illustration. • The dynamic method obtained high economic value from carbon sequestration. • The dynamic method decreased the possibility of biomass harvesting. Carbon sequestration plays an essential role in climate regulation, and its monetary value is critical for decision-making. To encourage carbon sequestration and avoid expensing the ecosystem services for future generations, a dynamic monetary valuation perspective was developed by integrating a carbon dynamics model of ecosystems and an atmospheric carbon cycle model. A case study of biomass utilization in Northern Shaanxi was conducted to illustrative the performance of this approach by comparing with the conventional approach. The carbon dynamics in the available lands were simulated by the CENTURY model under the RCP4.5 climate change scenario. The results suggested that the carbon storage was doubled without biomass utilization in the projected 25 years. When biomass was harvested, carbon storage decreased slightly. The monetary value without biomass harvesting in the dynamic approach was higher than that in the conventional approach. After analogizing the monetary values of carbon sequestration and biomass utilization, there was a lower likelihood of biomass harvesting in the dynamic approach than in the conventional approach. [ABSTRACT FROM AUTHOR]

The African Sahel-Sudano-Guinean region is one of the largest water limited environments in the world, thus making it highly vulnerable to climate change. Recent studies have shown vegetation greening in the region, but few have investigated the impact of this greening on carbon and water cycles. We used a combination of earth observation (EO) data and a diagnostic model to evaluate the extent of the vegetation greening and its impacts on carbon sequestration potential (i.e., Gross Primary Productivity-GPP) and the water cycle (i.e., Evapotranspiration-ET and Water Use Efficiency-WUE) from 1982 to 2015. Additionally, we evaluated the influence of key climatic variables (i.e., precipitation, temperature, and solar radiation) on vegetation greening, carbon sequestration potential and the water cycle. Our results showed widespread vegetation greening during the first half of the study period (1982–2000), driven mainly by increase in precipitation. However, the rate of greening reduced or became stagnant during the latter half of the study (2000–2015), but did not revert to pre-greening levels of 1980s, implying a persistent ecosystem change. The vegetation greening and increased precipitation resulted in a ~ 17.95% increase in GPP (from ~3.9 PgC/year in 1982 to ~4.6 PgC/year in 2000) and a ~ 21.28% increase in ET (from ~47 mm/year in 1982 to ~57 mm/year in 2015). The WUE showed an overall reduction, mainly attributed to large increases in ET not matched by similar magnitude of increases in GPP. Currently, there is lack of consensus on the magnitude of the contribution of drylands to the global carbon and water cycle. This study shows that drylands undergoing ecosystem change, coupled with climate change, may in future become important contributors to the global carbon and water cycle. Therefore, they could play a key role in future global warming and climate change mitigation strategies. • Widespread vegetation greening from 1982 to 2000, which stagnates from 2000 to 2015 • Precipitation dynamics was the key driver to vegetation greening. • Greening led to increases in gross primary productivity and evapotranspiration. • Overall reduction in water use efficiency was observed in the region. • Potential changes in future role of drylands in the global carbon and water cycle. [ABSTRACT FROM AUTHOR]

Coastal marine vegetation has been recently highlighted for its highly efficient carbon storage capacity. Among the sixty-four species of seagrass, Posidonia oceanica , a Mediterranean endemic species, appears to be the most effective in carbon fixation and storage. Based on new data from the study of one of the largest P. oceanica meadows in the Mediterranean Sea (100 km of coastline, 20 425 ha), and a synthesis of available data from the whole of the Mediterranean basin, the aim of this work is to evaluate the amount of carbon fixed each year by P. oceanica and sequestered in the matte, in relation with the mitigation of the impact of climate change (carbon sink). The mean total carbon fixation (blades, sheaths and rhizomes) per year varies between 33.5 and 426.6 g C.m−2 and the mean carbon sequestration (long-term sink in the matte), corresponding to the sheath and rhizome tissues, varies between 7.7 and 84.4 g C.m−2, with a clear decreasing trend according to depth because of the meadow density decrease. The synthesis of a hundred measurements made throughout the Mediterranean Sea and at depths between 0.5 and 32.0 m provides a basis for estimating the average annual carbon fixation and sequestration rate throughout the Mediterranean basin. The fixation of the blades is estimated at 1 024 t C.ha−1.yr−1, that of the sheaths at 220 t C ha−1.yr−1 and that of the rhizomes at 58 t C ha−1.yr−1; i.e. a total fixation rate of 1 302 t C ha−1.yr−1 and sequestration rate (dead sheaths and rhizomes) of 278 t C ha−1.yr−1. This annual carbon fixation represents only 0.61% on average of CO 2 emissions/releases for all Mediterranean countries but in the large Mediterranean islands this fixation is on average 3.1% and can reach almost 14.4% for Corsica. Moreover, the major advantage of the P. oceanica meadow lies in its capacity to store carbon from annual carbon sequestration for centuries to millennia and can be compared to several terrestrial ecosystems considered to be efficient in carbon storage (peatlands). • First assessment of carbon fixation and sequestration by Mediterranean seagrass. • 5 681 206 tons of CO 2 emissions, are fixed annually by Posidonia oceanica. • 21% of this carbon is sequestered, annually, by the Posidonia oceanica soil (matte). • For Mediterranean islands, carbon fixation can reach up to 14.5% of carbon emissions. [ABSTRACT FROM AUTHOR]

• C org burial was evaluated in seagrass sediments at the northern Mexican Caribbean. • Thalassia testudinum seagrass meadows showed C org storage within ~ 40 to ~ 100 years. • C org stock increments were related with increasing sediment accumulation rates. • Seagrasses might be gradually impacted by population growth and land use changes. Carbon sequestration in seagrass meadows mitigates the currently rising CO 2 atmospheric levels, as these ecosystems are highly productive and preserve sediment organic carbon over long periods. Five 210Pb dated sediment cores, collected from seagrass meadows dominated by Thalassia testudinum in the northern Mexican Caribbean touristic corridor Cancun-Riviera Maya, were used to establish temporal trends of organic carbon (C org) content, burial rates and stock variation over the past 100 years. C org contents (0.17–1.94%) and burial rates (2.0–252 g m−2 yr−1) were generally within the lower end range reported for seagrass meadow sediments worldwide. C org stock gradually increased over the past decades, associated with increasing sediment accumulation, possibly caused by inland erosion promoted by agricultural and forestry activities and, in the recent decades, by a rapid increase of urban development due to a fast growth of the tourist industry and population, likely causing fertilization of coastal waters. Seagrass meadow sediments in the northern Mexican Caribbean coastline showed long-term C org storage and preservation, since ~ 40 to ~ 100 years depending on the core, which emphasizes the need to protect these ecosystems against impacts of global change, and their incorporation into climate change mitigation strategies should be considered. [ABSTRACT FROM AUTHOR]

Carbon capture and storage sites in Barents Sea shelf are currently in progress as part of climate change mitigation activities. However environmental impacts of a possible CO 2 seepage on bacterial community are lacking knowledge. This work addressed potential consequences on bacterial communities from Snøvit region in Barents Sea sediments. Long-term experiment (92 days) was carried out mimicking realistic conditions of pressure (∼30 bars) using the unique hyperbaric chamber (Karl Erik TiTank). The experiment was divided in three stages: i) 21 days of no CO 2 , ii) 50 days of simulation of carbon dioxide leakage (depletion of pH to 7.0) and iii) 14 days emulating a leakage cessation. Results suggested that bacterial communities can adapt to a CO 2 leakage in short term. However, bacteria showed negative effects in terms of activity, community structure, and number of cells after long term CO 2 exposure. After CO 2 leakage cessation, bacterial communities did not show a significant recovery. These findings highlighted that, even though marine bacteria showed adaptation to the new conditions (acidified environment), in case of a small but continuous CO 2 leakage marine bacteria might not be recovered upon pre-exposure status. • Simulation of real conditions of a CCS site are essentials for environmental risk assessments. • Marine bacteria may adapt to a new situation in case of acidification event for a short time. • Marine bacteria community is altered in case of a CO 2 leakage after 3 weeks in long-term simulation. • Results did not show a potential recovery of marine bacteria when CO 2 was stopped within the monitored period. [ABSTRACT FROM AUTHOR]

Poplar (Populus L. spp.) Short Rotation Coppice systems (SRCs) for bioenergy production are being converted back to arable land. Transitioning to Alley Cropping Systems (ACSs) could be a suitable strategy for integrating former tree rows and arable crops. A field trial (Pisa, Central Italy) was set up with the aim of assessing the C storage of an ACS system based on hybrid poplar and sorghum (Sorghum bicolor L. Moench) and comparing it with that of an SRC cultivation system. The carbon budget at the agroecosystem scale was assessed in the first year of the transition using the net biome production (NBP) approach with a simplified method. The overall NBP for the SRC was positive (96 ± 40 g C m−2 year−1), highlighting that the system was a net carbon sink (i.e., NBP > 0). However, the ACS registered a net C loss (i.e., NBP < 0), since the NBP was −93 ± 56 g C m−2 year−1. In the first year of the transition, converting the SRC into an ACS counteracted the potential beneficial effect of C storage in tree belowground biomass due to the high heterotrophic respiration rate recorded in the ACS, which was fostered by the incorporation of residues and tillage disturbance in the alley. Additional years of heterotrophic respiration measurements could allow for an estimate of the speed and extent of C losses. [ABSTRACT FROM AUTHOR]