A transboundary agenda for nature-based solutions across sectors, scales and disciplines: Insights from carbon projects in Southeast Asia

Nature-based Solutions (NbS) are integral to efforts to keep global warming below 2°C in accordance with the United Nations' 2015 Paris Agreement on Climate Change. Yet the transboundary governance dimensions of NbS remain unclear and largely undocumented. In Southeast Asia, NbS have emphasised the conservation and/ or sustainable commodification of carbon sinks found in terrestrial and mangrove forests, seagrass meadows, peatlands and agricultural soils. Mostly project-driven and fixed-term, these "solutions" have often failed to meet their social and ecological objectives. Increasingly, they have added to cross-border problems of: (1) displaced carbon emissions; and (2) economic migration and societal dispossession. This perspective paper delineates a transboundary governance research agenda to mitigate these trade-offs and enhance the co-benefits of NbS in carbon sinks. Building on NbS literature, it identifies cross-sector, multi-scalar and interdisciplinary pathways to improve transboundary cooperation, inclusion and equity in carbon sink governance in varying Southeast Asian contexts.

Optimizing the ecological network of resource-based cities to enhance the resilience of regional ecological networks

Mineral extraction in resource-based cities has caused serious damage to the original ecology, resulting in poor regional vegetation growth, reduced carbon sequestration capacity, and reduced ecosystem resilience. Especially in resource-based cities with fragile ecology, the overall anti-interference ability of the environment is relatively worse. Seeking ecological network optimization solutions that can improve vegetation growth conditions on a large scale is an effective way to enhance the resilience of regional ecosystems. This paper introduces carbon sequestration indicators and designs a differential ecological networks (ENs) optimization model (FTCC model) to achieve the goal of improving ecosystem resilience. The model identifies the patches that need to be optimized and their optimization directions based on the differences in ecological function-topology-connectivity-carbon sequestration of the patches. Finally, the resilience of the ecological network before and after optimization was compared, proving that the model is effective. The results show that the sources in the Yulin ENs form three main clusters, with connectivity between clusters relying on only a few patches. The patches in the northeastern and southwest clusters are large but their ecological functions need to be improved. After optimization, 16 new stepping stones were added, 38 new corridors were added, and the ecological function of 39 patches was enhanced. The optimized ecological network resilience was improved in terms of structure, function, and carbon sinks, and carbon sinks increased by 6364.5 tons. This study provides a reference for measures to optimize landscape space and manage ecosystem resilience enhancement in resource-based cities.

How to achieve carbon neutrality and low-carbon economic development-evidence from provincial data in China

"Carbon Peaking and Carbon Neutrality" is a major strategy for China to cope with climate change at present. We define the carbon neutrality capability (CNC) to reflect the current situation of regional carbon neutrality, and propose a new coupling model to explore the coupling relationship between regional economic development and carbon neutrality capability (CNC). Finally, the influence mechanism of the energy consumption structure on CNC was further discussed by using STRIPAT model. The results show that: during we study period, the national average carbon sink was about 77.89 Mt, and the carbon sinks in Inner Mongolia, Heilongjiang, Sichuan and Yunnan were as high as 164 Mt, mainly concentrated in the western region. The national average carbon source is 222.12 Mt, which is about three times that of carbon sink. The carbon source in Shandong, Hebei and Jiangsu are as high as 400 Mt or more, mainly concentrated in the eastern region. In addition, the growth rate of carbon source is much faster than that of carbon sink, especially the carbon emission caused by energy consumption, which leads to a general decline in CNC, and the development of CNC in various provinces is not optimistic. CNC and economic development level of most provinces are in a state of recession decoupling, and the coupling state of the provinces studied in certain years is significantly different. The spatial distribution of CNC and GDP has shown a northeast-southwest pattern. In addition, the influence of coal consumption structure on CNC is significantly negative, so we should optimize the energy consumption structure and increase the proportion of clean energy consumption. This study can make clear the current carbon neutrality capability of provinces in China, facilitate the formulation and adjustment of emission reduction strategies of provinces and cities, and help China to achieve carbon neutrality as soon as possible.

The political economy of net-zero transitions: Policy drivers, barriers, and justice benefits to decarbonization in eight carbon-neutral countries

This study examines the political economy of decarbonization in eight countries over the period 2000 to 2021/2022 that have already achieved a national net-zero transition. These countries are Bhutan, Suriname, Panama, Guyana, Comoros, Gabon, Madagascar, and Niue. It utilizes an analytical method of a rich, interdisciplinary and systematized literature review integrated with thematic analysis. For each of these countries, the study examines the drivers and political motivation behind net-zero progress, including the timeline of events; the barriers and challenges that had to be overcome; and the benefits of decarbonization and its impacts on equity and justice. The main objectives of the study are to broaden the evidence base on low-carbon transitions beyond often and even overstudied countries that are Western, Educated, Industrialized, Rich, Democracies, or WEIRD countries, and to offer new empirical data on the strategy of energy policies in the real world, examining the first eight countries to achieve net-zero success in the modern era. It finds that all eight countries used a similar mix of nine policy interventions involving land use, renewable energy, and waste management. Common barriers included vulnerability to the effects of extreme climate events either in the form of natural disasters (i.e. landslides and floodings) or ecosystems degradation (i.e. ocean acidification, coastal erosion and forests loss). Despite these barriers, achieving net-zero emissions positively impacted marginalized communities by providing a more equitable distribution of climate benefits, mitigating adverse health effects and reducing social inequalities, particularly in low-income areas.

Measurement and factor analysis of carbon neutrality development level in eastern China

The Chinese government has officially announced that China's carbon dioxide emissions will reach to peak before 2030 and achieve carbon neutrality before 2060. Based on the carbon neutrality development of 12 provinces and cities in eastern China from 2010 to 2019, this paper constructs an evaluation index system, and it uses the entropy weight method and coefficient of variation method to measure the carbon neutrality development level in the eastern China. The results show that from 2010 to 2019, the changes of carbon source level in 12 provinces and cities in the eastern China are lower than the changes in carbon sink level, and the changes of carbon source and sink level in most provinces and cities show the increasing trend. Spatially, the carbon neutral development level shows the differentiation characteristics of "low in the middle, high in the north and south." The main factors affecting the carbon neutrality level of eastern provinces and cities include policy, economic development and industrial structure, energy intensity and structure, urban development, and population size ecological environment. High-value areas are mainly distributed in Heilongjiang Province, Jilin Province and Fujian Province. Low-value areas are mainly distributed in Jiangsu Province and Shandong Province. Eastern China still needs to strengthen its emphasis on low-carbon policies. For Shandong Province, Jiangsu Province, and Hebei Province, policies should be introduced to reduce carbon sources, accelerate their industrial upgrading, and optimize their energy use structure. For Beijing City, Shanghai City, Heilongjiang Province, and Jilin Province, policies should be introduced to develop carbon sinks while maintaining their low carbon source levels. For Beijing City and Shanghai City, policies related to green and low-carbon technologies should be introduced to promote the development of carbon sink capacity through low-carbon technologies in limited urban areas.

The role of forests in the EU climate policy: are we on the right track?

BACKGROUND

The European Union (EU) has committed to achieve climate neutrality by 2050. This requires a rapid reduction of greenhouse gas (GHG) emissions and ensuring that any remaining emissions are balanced through CO₂ removals. Forests play a crucial role in this plan: they are currently the main option for removing CO₂ from the atmosphere and additionally, wood use can store carbon durably and help reduce fossil emissions. To stop and reverse the decline of the forest carbon sink, the EU has recently revised the regulation on land use, land-use change and forestry (LULUCF), and set a target of - 310 Mt CO₂e net removals for the LULUCF sector in 2030.

RESULTS

In this study, we clarify the role of common concepts in forest management - net annual increment, harvest and mortality - in determining the forest sink. We then evaluate to what extent the forest sink is on track to meet the climate goals of the EU. For this assessment we use data from the latest national GHG inventories and a forest model (Carbon Budget Model). Our findings indicate that on the EU level, the recent decrease in increment and the increase in harvest and mortality are causing a rapid drop in the forest sink. Furthermore, continuing the past forest management practices is projected to further decrease the sink. Finally, we discuss options for enhancing the sinks through forest management while taking into account adaptation and resilience.

CONCLUSIONS

Our findings show that the EU forest sink is quickly developing away from the EU climate targets. Stopping and reversing this trend requires rapid implementation of climate-smart forest management, with improved and more timely monitoring of GHG fluxes. This enhancement is crucial for tracking progress towards the EU's climate targets, where the role of forests has become - and is expected to remain - more prominent than ever before.

How does heterogeneous environmental regulation affect net carbon emissions: Spatial and threshold analysis for China

The Chinese government has made great efforts in air pollutant reduction and carried out strict regulation policies. Since numerous air pollutants and CO₂ tend to have the same root, source, and process, recent studies argue that environmental regulation may also contribute to reducing carbon emissions. To investigate how various types of environmental regulations affect carbon emissions reduction, this paper constructs the spatial Durbin model and panel threshold model based on provincial panel data in China during 2003-2019. The main findings are as follows: First, China's net carbon emissions show a decreasing trend from east to west, displaying significant spatial agglomeration characteristics. Then, formal and informal environmental regulations have inverted U-shaped impacts on net carbon emissions. The "green paradox" and "reverse emission reduction" effects come into play at different stages. Finally, the threshold model reveals that with the improvement of regional technological innovation levels, the carbon-reducing effect of environmental regulation will increasingly come to the fore. These research findings are conducive to providing theoretical guidance for government to formulate and implement environmental regulation policies rationally.

Estimation of the relative contributions of forest areal expansion and growth to China's forest stand biomass carbon sequestration from 1977 to 2018

As a prominent part of global and regional terrestrial carbon (C) pools, increases in forest biomass C sinks can be attributed to either forest areal expansion (FAE) or increased biomass C density (IBCD). Accurate estimates of the relative contributions of FAE and IBCD to forest C sequestration can improve our understanding of forest C cycling processes and will help to formulate rational afforestation policies to cope with global warming. In this study, the Continuous Biomass Expansion Factor (CBEF) model and Forest Identity concept were used to map the spatiotemporal variation of the relative contribution of FAE and IBCD to the C sequestration of forest (natural and planted forests) in China and seven regions during the past 40 years. Our results suggest that: (1) total forest biomass C density and stocks of forest increased from 35.41 Mg C ha^-1 and 4128.50 Tg C to 43.95 Mg C ha^-1 and 7906.23 Tg C in China from 1977 to 2018, respectively; (2) for all forests, the IBCD has been a smaller contributor to C sinks than FAE in China from 1977 to 2018 (33.27 vs. 66.73%); (3) the contribution of FAE to C sinks is greater than that of IBCD in planted forests (63.99 vs. 36.01%), while in natural forests, IBCD has a larger contribution than FAE (57.82 vs. 42.18%) from 1977 to 2018 and the relative contribution of FAE has exceeded IBCD in the last decade; and (4) these patterns varied at the regional level such that the relative contribution of FAE increased for planted forests in most regions but for natural forests, IBCD gradually reached saturation and C stocks declined in northern regions in the last decade. The results from this study suggest that total biomass C sinks will keep increasing because of the increased forest area contributed by afforestation and the relatively young trees in planted forests. This study facilitates a more comprehensive assessment of forest C budgets and improves our understanding of ecological mechanisms of forest biomass carbon stock and dynamics.

Changes of lake organic carbon sinks from closed basins since the Last Glacial Maximum and quantitative evaluation of human impacts

BACKGROUND

Closed basins occupy 21% of the world's land area and can substantially affect global carbon budgets. Conventional understanding suggests that the terminal areas of closed basins collect water and carbon from throughout the entire basin, and changes in lake organic carbon sinks are indicative of basin-wide organic carbon storages. However, this hypothesis lacks regional and global validation. Here, we first validate the depositional process of organic carbon in a typical closed-basin region of northwest China using organic geochemical proxies of both soil and lake sediments. Then we estimate the organic carbon sinks and human impacts in extant closed-basin lakes since the Last Glacial Maximum (LGM).

RESULTS

Results show that 80.56 Pg organic carbon is stored in extant closed-basin lakes mainly found in the northern mid-latitudes. Carbon accumulation rates vary from 17.54 g C m^-2 yr^-1 during modern times, 6.36 g C m^-2 yr^-1 during the mid-Holocene and 2.25 g C m^-2 yr^-1 during the LGM. Then, we evaluated the influence by human activities during the late Holocene (in the past three thousand years). The ratio of human impacts on lake organic carbon storage in above closed basins is estimated to be 22.79%, and human-induced soil organic carbon emissions in the past three thousand years amounted to 207 Pg.

CONCLUSIONS

While the magnitude of carbon storage is not comparable to those in peatland, vegetation and soil, lake organic carbon sinks from closed basins are significant to long-term terrestrial carbon budget and contain information of climate change and human impact from the whole basins. These observations improve our understanding of carbon sinks in closed basins at various time scales, and provide a basis for the future mitigation policies to global climate change.

Data for: Terrain units, land use/cover, and gross primary productivity of the largest fluvial basin in the Brazilian Amazonia/Cerrado ecotone: The Araguaia River Basin

Integrity of most of tropical wetlands is threatened because they are often considered freely available resources of land and water. The Araguaia River Basin is one of the Brazilian basins most influenced by tropical seasonal floods, in addition to being rich in biodiversity and providing diverse ecosystem services. Here, we propose the analysis of the landscape of Araguaia Basin in terms of terrain units, rainfall, land use/cover and gross primary productivity (GPP). For this, the integration of different databases was made, including the topographic domains, protected areas and indigenous lands; land use/cover map (year 2016); time series of GPP derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor (period of 2000-2015); Shuttle Radar Topography Mission (SRTM) digital elevation models (DEM); and precipitation data produced by the WorldClim version 2 dataset. GPP time serie were processed using statistical methods of decomposition throughout R software. The proposed methodology can assist in new studies aimed at land use changes and carbon cycles.

Terrestrial organic carbon storage modes based on relationship between soil and lake carbon, China

Terrestrial ecosystems have received considerable attention as a significant sink for organic carbon at regional to global scales. Previous studies were focused on assessment and quantification of carbon sinks for one ecotype, and few have worked on the interconnection of terrestrial sinks. In this paper, we synthesized the data from China's second national soil survey and direct measurements from 54 lakes. Meanwhile, we investigated the controlling factors of carbon accumulation dynamics in soils and lakes. Results showed varied spatial distribution of soil and lake organic carbon in different regions, and three storage modes were found. The storage mode of watershed collection was observed in the region of the Qinghai-Tibetan Plateau, while the northeast China and Yunnan-Guizhou Plateau revealed another storage mode of autochthonous deposition, and the mode of human activities affection was represented by the East Plain and Mongolia-Xinjiang Plateau. The spatial difference throughout China was regulated by various climate patterns, geological conditions and anthropogenic interference. Our results provide insights into carbon storage modes in various regions, and also inform strategies for enhancing global carbon sequestration and future mitigation policies towards global climate change.

Territorial Rights and Carbon Sinks

Scholars concerned with abuses of the "resource privilege" by the governments of developing states sometimes call for national sovereignty over the natural resources that lie within its borders. While such claims may resist a key driver of the "resource curse" when applied to mineral resources in the ground, and are often recognized as among a people's territorial rights, their implications differ in the context of climate change, where they are invoked on behalf of a right to extract and combust fossil fuels that is set in opposition to global climate change mitigation imperatives. Moreover, granting full national sovereignty over territorial carbon sinks may conflict with commitments to equity in the sharing of national mitigation burdens, since much of the planet's carbon sink capacity lies within territorial borders to which peoples have widely disparate access. In this paper, I shall explore this tension between a global justice principle that is often applied to mineral resources and its tension with contrary principles that are often applied to carbon sink access, developing an analysis that seeks to reconcile what would otherwise appear to be fundamentally incompatible aims.

Carbon accumulation rates recorded in the last 150years in tropical high mountain peatlands of the Atlantic Rainforest, SE - Brazil

Peatlands are environmental matrices that store large amounts of organic carbon (TOC) and work as records of environmental changes. Recent record of organic carbon accumulated were assessed in two Forest National Parks, Itatiaia and Serra dos Órgãos in the Southeastern of Brazil. Based on organic and inorganic characterization, the cores from peatlands presented a predominance of organic material in an advanced stage of decomposition and those soils were classified as typical Haplosaprists Histosols. The combination of favorable topographic and climatic conditions led to rapid C accumulation across coastal mountain in the tropical peatlands studied, presenting an average accumulation rate of C, in the last century, of 194gCm^-2yr^-1 about 7 higher times than the rate found in boreal and subarctic peatlands, those higher values may be related to changes in the hydrological cycle occurred since 1950s.