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Differences in carbon sink potential between urban agglomerations are decreasing: Evidence from China
... Studies on urban agglomerations also emphasize the critical role of policy initiatives and technological advancements in boosting carbon sink potential. For example, Zeng et al. (2024a) found that urban areas benefiting from policy support in China exhibit significantly higher carbon sink potential compared to regions dominated by regenerating forests. By applying the Dagum Gini coefficient and CRITIC methodology, their research revealed that urban clusters are gradually enhancing their carbon sink capacity, with medium-and high-level regions showing remarkable improvements. ...
As the global climate crisis intensifies, understanding the evolution of carbon budgets at fine spatial scales is crucial for developing targeted mitigation strategies. This study examines the spatiotemporal dynamics, regional disparities, and convergence patterns of carbon budgets across 112 counties in Hunan Province, China, from 2000 to 2020. By employing a combination of spatiotemporal analysis, Dagum Gini coefficients, and LISA spatial autocorrelation, the study reveals a persistent and widening imbalance between carbon emissions and sequestration. The findings indicate that carbon emissions increased by 87.25%, particularly in economically developed regions like the Chang-Zhu-Tan urban agglomeration, while carbon sequestration decreased by 5%, exacerbating the carbon budget deficit. Although regional disparities in carbon budgets have gradually narrowed (with the Gini coefficient falling from 0.441 to 0.373), the convergence process remains slow and uneven. High-emission clusters continue to dominate eastern Hunan, while western counties, with strong carbon sinks, still face significant ecological conservation pressures. LISA analysis further confirms the presence of significant spatial dependence and path dependency in the evolution of carbon budgets, suggesting that short-term policy interventions may encounter substantial inertia. These findings emphasize the urgent need for differentiated low-carbon policies. Stricter carbon control measures and the adoption of green technologies are essential for high-emission urban clusters, while regions with substantial sequestration potential must enhance ecological protection to strengthen their carbon sink capacity. This study provides a detailed, data-driven perspective on carbon budget dynamics and offers valuable insights for regional carbon management and sustainable development policies in rapidly urbanizing regions.
... Urban areas are pivotal in driving interannual variations and subsequent trends in terrestrial carbon sinks (Zeng et al. 2024). Enhancing the development of urban carbon sinks is crucial for achieving regional carbon neutrality objectives. ...
Assessing the changes in carbon sink disturbances is crucial for understanding urban ecosystem stability under climate change and human activities. This study proposed a novel assessment framework for carbon sink disturbance risk (CSDR), integrating the carbon sink loss with disturbance probability and applying Tapio model with Mann–Kendall trend test methods, to reveal the intrinsic driving mechanisms and external evolutionary trends of CSDR in the Ordos during 2002–2022. The results indicated that loss and disturbance probability of carbon sink initially increased, followed by a subsequent decrease. From 2002 to 2012, the proportion of high-value CSDR areas increased from 7.69%, and weak decoupling between carbon sink loss and disturbance probability made up 57.77%. During 2002–2022, the CSDR declined mainly in the eastern and northern regions of Ordos. The results show that multiple factors influence the changes in carbon sinks in the Ordos region, and the carbon sink loss due to human disturbances has been improved. The findings enhance the understanding of human-carbon interactions and contribute to research on carbon sinks and urban sustainable development.
... In general, economically developed regions are often areas with concentrated carbon emissions, manifested as carbon deficits (Tao et al., 2024). In contrast, less developed regions, which are rich in ecological resources, have more carbon sink resources and can generate more carbon absorption, manifested as carbon surpluses (Zeng et al., 2024). Carbon ecological compensation enables economically developed regions to support ecological protection and the construction of carbon sink areas through compensation methods such as funds and technology . ...
Introduction: In order to improve ecological and environmental governance capacities, this study explores the creation and efficacy of a horizontal carbon ecological compensation, aiming to enhance ecological and environmental governance capabilities. The research addresses the critical need for innovative solutions to balance carbon emissions and ecological preservation in river basins, with the YRB serving as a primary case study.
Methods: Net carbon emissions were computed for each YRB province using data from 2013 to 2022, 13 differentiating between carbon surplus and deficit locations. An evolutionary game model that examined dynamic interactions under incentive and punishment mechanisms was built using these computations as the foundation. Important elements affecting the ecological compensatory process for horizontal carbon were found. The viability of the system was demonstrated by the use of machine learning techniques to forecast net carbon 17 emissions under a voluntary trade scenario.
Results: The findings show that the YRB’s carbon emission management and conservation may be greatly enhanced by market-based incentives and appropriate advice. The evolutionary game model revealed that integrating incentive and penalty mechanisms effectively promotes cooperation among provinces, leading to enhanced carbon management. Machine learning predictions further validated the potential of voluntary carbon trading to reduce net emissions, highlighting the practicality of the proposed compensation mechanism.
Discussion: The results offer a theoretical framework for the YRB’s implementation of horizontal carbon ecological compensation. The proposed mechanism, founded on the trade of carbon emissions and backed by confirmation from machine learning, offers a novel approach to ecological protection. This model not only addresses the unique challenges of the YRB but moreover acts as a model for ecological management in other river basins., contributing to broader efforts in sustainable environmental management.
China has implemented a series of ecological engineering projects to help achieve the 2060 carbon neutrality target. However, the lack of quantitative research on ecological engineering and the contribution of climate change to terrestrial carbon sinks limits this goal. This study uses robust statistical models combined with multiple terrestrial biosphere models to quantify the impact of China's ecological engineering on terrestrial ecosystem carbon sink trends and their differences according to the difference between reality and nonpractice assumptions. The main conclusions include the following: (1) since 1901, 84% of terrestrial ecosystem carbon sinks in China have shown an increasing trend, and approximately 45% of regional carbon sinks have increased by more than 0.1 g C/m2 every 10 years. (2) Considering the impact of human activities and the implementation of ecological engineering in China, approximately 56% of carbon sinks have improved, and approximately 10% of the regions whose carbon sink growth exceeds 50 g C m−2 yr−1 are mainly in the southeast coastal of China. (3) The carbon sequestration potential and effect of the Sanjiangyuan ecological protection and construction project are better than others, at 1.26 g C m−2 yr−1 and 14.13%, respectively. The Beijing–Tianjin sandstorm source comprehensive control project helps alleviate the reduction in carbon sinks, while the southwest karst rocky desertification comprehensive control project may aggravate the reduction in carbon sinks. This study clarifies the potential of China's different ecological engineering to increase carbon sink potential, and distinguishes and quantifies the contribution of climate and human activity factors to it, which is of great significance to the system management optimization scheme of terrestrial ecosystems and can effectively serve the national carbon neutral strategy.
Deforestation and forest degradation lead to an increase in the level of carbon in the atmosphere and disrupted the global carbon cycle. The tropical forest has received a lot of interest since it contributes around 60% of the total global forest carbon. By enhancing carbon sink, tropical forests have a great potential in mitigating climate change. Assessing aboveground biomass (AGB) and carbon stock through field inventories is crucial for this purpose as it provides the most accurate result. The research was conducted at Danum Valley Conservation Area and INFAPRO in Sabah, Malaysia. An earlier study over 35 years ago at this site suggests that restored forests accrue AGB at twice the rate of regenerating forests, though the cause of this difference between treatments is unclear. Thus, this study will focus on three principal study sites which are restored, naturally regenerating and old-growth forests to determine the forest’s potential to sequester and store carbon in the forest ecosystem. These three sites were chosen because it is a well-established plot from the earlier inventory over the last seven years. The field measuring method is a non-destructive methodology. Tree parameters such as diameter at breast height (DBH), tree height and tree species diversity were collected for calculating AGB using a species-specific allometric equation. Results showed a positive correlation between tree species, diameter at breast height, and biomass/carbon stock across three different forest treatments. The active restoration increases up to 151% carbon stock whilst the old-growth forest increased by 34% and natural regeneration increased by 73%, which active restoration can be the best solution for forest treatment. The outcome of this study will increase the ability of forest authorities and the Malaysian government to effective monitoring of carbon stock for establishing reliable standard guidelines in measuring deforestation and forest degradation toward achieving sustainable forest management.
To achieve carbon peaking and neutrality goals, China is establishing a national unified carbon emission trading market, especially including forest carbon sequestration market. This study assesses the potential of China’s forest carbon sinks and mitigation potential. We use the Global Forest Products Model to simulate the dynamic changes in China's forest resources from 2018 to 2060, under different carbon sequestration prices scenarios. The projection results indicate that China's forest carbon sinks will be 1.26 Pg (peta-grams) in 2021–2030 and 6.78 Pg in 2021–2060, giving an offset ratio of 4.9–7.0 % and 13.2–18.2 % of China's projected carbon emission in the same period, respectively. Therefore, China's forest carbon sinks will play an important role in carbon peaking and neutrality goals. Meanwhile, forest carbon trading has the potential to increase China's forest carbon sequestration, although the impact may not be immediately apparent. The additional increase in forest carbon sinks from carbon sequestration trading scenarios will not exceed 1.6 % of China’s total carbon emissions between 2021 and 2030. At the current carbon trading price in China (25/t), 4.1 % to 5.6 % ($54/t). China should therefore hasten the integration of forest carbon sinks into the national carbon emission unified market and boost the carbon trading price by policy design and market adjustment, or government directly compensate for the forest carbon sequestration function. For forest carbon sinks to play their role in reducing the carbon neutral cost of society, China should raise the amount of forest carbon sink CCERs (Chinese Certified Emission Reductions) used to offset carbon emission allowances in key emission units.
The original variables were 14 statistics in 31 provinces and cities in mainland China (excluding Hong Kong, Macao and Taiwan) in 2019, including forest area, forest tending area, afforestation area and timber production. Factor analysis was used to study the factors affecting development potential of forest carbon sinks in mainland China. The results show that the total forest resources factor extracted from the variables related to forest stock and forest land use area was the most important affecting this potential, followed by the forest climate and output value factor extracted from variables related to climate and output. Third was the forest ecological construction factor, which was extracted from forestry afforestation area related variables and fire-damaged areas. In last place was the forest disaster prevention factor extracted from forest nurturing and pest and rodent control area variables. According to systematic clustering of the comprehensive score, development potential of forest carbon sinks in 31 provinces and municipalities across the country was divided into five categories and, based on this, targeted suggestions were put forward for improvement of the above potential in various regions.
The implementation of carbon peaking and carbon neutrality is an essential measure to reduce greenhouse gas emissions and actively respond to climate change. The net carbon sink efficiency (NCSE), as an effective tool to measure the carbon budget capacity, is important in guiding the carbon emission reduction among cities and the maintenance of sustainable economic development. In this paper, NCSE values are used as a measure of the carbon budget capacity to measure the spatiotemporal evolution of the carbon neutral capacity of three major urban agglomerations (UAs) in China during 2007–2019. The clustering characteristics of the NCSE of these three major UAs, and various influencing factors such as carbon emissions, are analyzed using a spatiotemporal cube model and spatial and temporal series clustering. The results reveal the following. (1) From the overall perspective, the carbon emissions of the three major UAs mostly exhibited a fluctuating increasing trend and a general deficit during the study period. Moreover, the carbon sequestration showed a slightly decreasing trend, but not much fluctuation in general. (2) From the perspective of UAs, the cities in the Beijing–Tianjin–Hebei UA are dominated by low–low clustering in space and time; this clustering pattern is mainly concentrated in Beijing, Xingtai, Handan, and Langfang. The NCSE values in the Yangtze River Delta UA centered on Shanghai, Nanjing, and the surrounding cities exhibited high–high clustering in 2019, while Changzhou, Ningbo, and the surrounding cities exhibited low–high clustering. The NCSE values of the remaining cities in the Pearl River Delta UA, namely Guangzhou, Shenzhen, and Zhuhai, exhibited multi-cluster patterns that were not spatially and temporally significant, and the spatiotemporal clusters were found to be scattered. (3) In terms of the influencing factors, the NCSE of the Beijing–Tianjin–Hebei UA was found to be significantly influenced by the industrial structure and GDP per capita, that of the Yangtze River Delta UA was found to be significantly influenced by the industrial structure, and that of the Pearl River Delta UA was found to be significantly influenced by the population density and technology level. These findings can provide a reference and suggestions for the governments of different UAs to formulate differentiated carbon-neutral policies.
Nowadays the complex international political situation has caused the shortage of coal supply in the European region. Scholars have done a lot of research on supplier evaluation. However, these studies don’t reflect the variability of the indicators, such as interruption caused by recent war. Coal-electricity-integrated companies have a large demand for thermal coal and high requirements for stable supply, so they need to conduct timely and effective short-term evaluation of suppliers. This paper improves the CRITIC method and uses short-term transaction data for a coal-electricity-integrated firm to evaluate its coal suppliers. The results show that the improved CRITIC method effectively avoids the problem of weight changes caused by conflicting value ranges of indicators, and its evaluation results are more consistent with the actual situation, which can meet the requirements of large coal enterprises for evaluating suppliers.
Cycling of organic carbon in the ocean has the potential to mitigate or exacerbate global climate change, but major questions remain about the environmental controls on organic carbon flux in the coastal zone. Here, we used a field experiment distributed across 28° of latitude, and the entire range of 2 dominant kelp species in the northern hemisphere, to measure decomposition rates of kelp detritus on the seafloor in relation to local environmental factors. Detritus decomposition in both species were strongly related to ocean temperature and initial carbon content, with higher rates of biomass loss at lower latitudes with warmer temperatures. Our experiment showed slow overall decomposition and turnover of kelp detritus and modeling of coastal residence times at our study sites revealed that a significant portion of this production can remain intact long enough to reach deep marine sinks. The results suggest that decomposition of these kelp species could accelerate with ocean warming and that low-latitude kelp forests could experience the greatest increase in remineralization with a 9% to 42% reduced potential for transport to long-term ocean sinks under short-term (RCP4.5) and long-term (RCP8.5) warming scenarios. However, slow decomposition at high latitudes, where kelp abundance is predicted to expand, indicates potential for increasing kelp-carbon sinks in cooler (northern) regions. Our findings reveal an important latitudinal gradient in coastal ecosystem function that provides an improved capacity to predict the implications of ocean warming on carbon cycling. Broad-scale patterns in organic carbon decomposition revealed here can be used to identify hotspots of carbon sequestration potential and resolve relationships between carbon cycling processes and ocean climate at a global scale.
Cities are hotspots of anthropogenic activity and consumption. Thus, the consumption-based carbon footprints of their residents are pronounced. However, the beneficial climate impacts attributable to individual residents, such as carbon sequestration and storage (CSS) provided by residential green spaces and housing, have received less attention in the scientific literature. This review article presents an overview of the current research on the urban residential environment's CSS potential and argues for its inclusion in the so-called carbon handprint potential of individual consumers. The focus of existing research is on developed countries, and in empirical studies the absence of compiling literature presents a clear research gap. Most current potential is estimated to lie within the carbon pools of residential vegetation, soils and wooden construction, with biochar and other biogenic construction materials presenting key future development pathways. The underlying background variables guiding the formation of a residential carbon pool were identified as extremely complex and interconnected, broadly classified into spatial, temporal and socioeconomic factor categories. Our findings suggest that there is significant potential for growth in the residential CSS capacity, but substantial efforts from the scientific community, urban planners and policy-makers, and individual residents themselves are needed to realise this.
The accumulation of nutrients (eutrophication) in water bodies generally produces increased concentrations of organic matter that eventually are deposited in sediment, and partially mineralized, generating greenhouse carbon gases (GHCG). The application of eutrophication control methods includes the application of phosphate adsorbing materials such as Phoslock (PHOS), and hypolimnetic oxygenation systems (HOS). We evaluated the generation of GHCG in sediment subject to these eutrophication control methods. Combined water and sediment samples from the Valle de Bravo reservoir in Mexico, were incubated in reactors, where the following eutrophication control methods were applied: HOS, PHOS, HOS + PHOS, and compared to a reactor without treatment (CONTROL). Redox potential (Eh), pH, redox-sensitive ions, and GHCG emissions were monitored, observing the following rates: CONTROL (15.6 mmol m⁻² d⁻¹) > HOS (12.8) > HOS + PHOS (11.0) > PHOS (9.7 mmol m⁻² d⁻¹), with the CONTROL rate within values determined from published sediment core data. The GHCG emissions increased with time as Eh decreased, and sulfate reduction increased. Application of eutrophication control methods in the Valle de Bravo reservoir, would most probably result in lower GHCG generation and emission rates. This is due to the repression of sulfate-reduction in water-sediment systems where HOS and PHOS were applied both individually and combined.
Forests play an important role in the global carbon cycle, and the growth of forest trees is essential to forest carbon sinks. It is necessary to explore the diameter at breast height (DBH) growth of trees and to quantify the effects of different factors on their growth to predict forest development. This study constructed an individual-tree annual growth-rate model of 41 dominant tree species in China to explore the effects of genetic characteristics and the environment on tree growth and the relationship between forest carbon sink capacity and the geographical environment. The model was estimated and evaluated based on 492,555 samples of 7801 permanent plots (covering 31 provinces in mainland China) and then decomposed into a general annual growth-rate component and an environmental modifier component. The results showed that tree species and size were the dominant factors that affected the growth rate, showing an inverse J-curve trend, and temperature was the most important of all environmental factors. In addition, there was a significant correlation between the potential aboveground carbon sink (PACS) and the geographic growth pattern index (GPI) (Spearman’s = 0.445, p-value < 0.001) and a significant correlation between the geographic growth structure index PACS and the geographic growth structure index (GSI) (Spearman’s = 0.014, p-value < 0.001). Areas with high GPI and GSI may have better environmental conditions for tree growth, leading to higher PACS. In China, the GPI was higher in the southeastern regions than in the northwestern regions and was also higher in the more humid regions than in the dry regions, resulting in a higher PACS. In conclusion, in forest resource management and future afforestation planning, we should first consider the suitability of the geographical environment, and then take the topographical structure into consideration to determine the proportion of suitable tree species and forest structure.
Enhancing the terrestrial ecosystem carbon sink (referred to as terrestrial C sink) is an important way to slow down the continuous increase in atmospheric carbon dioxide (CO2) concentration and to achieve carbon neutrality target. To better understand the characteristics of terrestrial C sinks and their contribution to carbon neutrality, this review summarizes major progress in terrestrial C budget researches during the past decades, clarifies spatial patterns and drivers of terrestrial C sources and sinks in China and around the world, and examines the role of terrestrial C sinks in achieving carbon neutrality target. According to recent studies, the global terrestrial C sink has been increasing from a source of (-0.2±0.9) Pg C yr-1 (1 Pg=1015 g) in the 1960s to a sink of (1.9±1.1) Pg C yr-1 in the 2010s. By synthesizing the published data, we estimate terrestrial C sink of 0.20-0.25 Pg C yr-1 in China during the past decades, and predict it to be 0.15-0.52 Pg C yr-1 by 2060. The terrestrial C sinks are mainly located in the mid- and high latitudes of the Northern Hemisphere, while tropical regions act as a weak C sink or source. The C balance differs much among ecosystem types: forest is the major C sink; shrubland, wetland and farmland soil act as C sinks; and whether the grassland functions as C sink or source remains unclear. Desert might be a C sink, but the magnitude and the associated mechanisms are still controversial. Elevated atmospheric CO2 concentration, nitrogen deposition, climate change, and land cover change are the main drivers of terrestrial C sinks, while other factors such as fires and aerosols would also affect ecosystem C balance. The driving factors of terrestrial C sink differ among regions. Elevated CO2 concentration and climate change are major drivers of the C sinks in North America and Europe, while afforestation and ecological restoration are additionally important forcing factors of terrestrial C sinks in China. For future studies, we recommend the necessity for intensive and long term ecosystem C monitoring over broad geographic scale to improve terrestrial biosphere models for accurately evaluating terrestrial C budget and its dynamics under various climate change and policy scenarios.
China has experienced unprecedented urbanization and associated rural depopulation during recent decades alongside a massive increase in the total population. By using satellite and demographical datasets, we here test the hypothesis that urbanization and carbon neutrality are not mutually exclusive and that sustainably managed urbanization may even be an integral part of the pathway to reduce atmospheric CO2. We show that, although urban expansion caused an initial aboveground carbon loss of −0.02 PgC during 2002–2010, urban greening compensates these original losses with an overall balance of +0.03 PgC in urban areas during 2002–2019. We further show that a maximum increase in aboveground carbon stocks was observed at intermediate distances to rural settlements (2–4 km), reflecting the decreased pressure on natural resources. Consequently, rural areas experiencing depopulation (−14 million people yr−1) coincided with an extensive aboveground carbon sink of 0.28 ± 0.05 PgC yr−1 during 2002–2019, while at the same time only a slight decline in cropland areas (4%) was observed. However, tree cover growth saturation limits the carbon removal capacity of forests and only a decrease in CO2 emissions from fossil fuel burning will make the aim of carbon neutrality achievable. China has pledged to achieve carbon neutrality by 2060 but policies favouring urbanization could slow down progress. This study tests the hypothesis that urbanization and carbon neutrality are not mutually exclusive and that sustainably managed urbanization could increase carbon sequestration, especially in rural areas.
Excessive emissions of greenhouse gases — of which carbon dioxide is the most significant component, are regarded as the primary reason for increased concentration of atmospheric carbon dioxide and global warming. Terrestrial vegetation sequesters 112–169 PgC (1PgC = 10¹⁵g carbon) each year, which plays a vital role in global carbon recycling. Vegetation carbon sequestration varies under different land management practices. Here we propose an integrated method to assess how much more carbon can be sequestered by vegetation if optimal land management practices get implemented. The proposed method combines remotely sensed time-series of net primary productivity datasets, segmented landscape-vegetation-soil zones, and distance-constrained zonal analysis. We find that the global land vegetation can sequester an extra of 13.74 PgC per year if location-specific optimal land management practices are taken and half of the extra clusters in ~15% of vegetated areas. The finding suggests optimizing land management is a promising way to mitigate climate changes.
Industrial green technology innovation has become an important content in achieving high-quality economic growth and comprehensively practicing the new development concept in the new era. This paper measures the efficiency of industrial green technology innovation and regional differences based on Chinese provincial panel data from 2005 to 2018, using a combination of the super efficiency slacks-based measure (SBM) model for considering undesirable outputs and the Dagum Gini coefficient method, and discusses and analyses the factors influencing industrial green technology innovation efficiency by constructing a spatial econometric model. The results show that: firstly, industrial green technology innovation efficiency in China shows a relatively stable development trend, going through three stages: “stationary period”, “recession period” and “growth period”. However, the efficiency gap between different regions is obvious, specifically in the eastern > central > western regions of China, and the industrial green technology efficiency innovation in the central and western regions is lower than the national average. Secondly, regional differences in the efficiency of industrial green technology innovation in China are evident but tend to narrow overall, with the main reason for the overall difference being regional differences. In terms of intra-regional variation, variation within the eastern region is relatively stable, variation within the central region is relatively low and shows an inverted ‘U’ shaped trend, and variation within the western region is high and shows a fluctuating downward trend. Thirdly, the firm size, government support, openness to the outside world, environmental regulations and education levels contribute to the efficiency of industrial green technology innovation. In addition, the industrial structure hinders the efficiency of industrial green technology innovation, and each influencing factor has different degrees of spatial spillover effects.
Carbon neutrality is a strategic choice for the sustainable development of global cities. Quantitatively assessing the spatio-temporal patterns of urban vegetation carbon sink and the impact of human activities has become an essential basis for adjusting urban carbon balance. We used Huaibei, a typical city with vigorous human coal resource mining activities, as the case study area. We regarded the net ecosystem productivity (NEP) as an indicator parameter of vegetation carbon sink and calculated it based on the improved Carnegie-Ames-Stanford approach (CASA). We then revealed the spatial–temporal evolution of vegetation carbon sink through trend analysis, coefficient of variation, and standard direction. Finally, we used geographic detectors to evaluate the impact of human activities on NEP. We found that net primary productivity (NPP) accuracy was good, and the R2 value was 0.755 compared with MODIS NPP products. NEP was characterized by the first decrease and then increase, showing a slow increase overall, with an average trend coefficient of 0.15 gC·m−2·a−1. The average value in 2010 was the lowest at 18.30 gC·m−2·a−1. In terms of spatial characteristics, NEP showed a gradual decrease from north to south. High and severe fluctuations were distributed along the southeast, mainly concentrated in Duji District, Xiangshan District, and Lieshan District. The driving factors with reliable explanatory power for NEP were population density, GDP, and road density, while land use type, soil erosion intensity, and mining and collapse area had weak explanatory power. Meanwhile, factors of cooperative interaction enhanced the explanatory power of the results.
Achieving carbon neutrality is a necessary effort to rid humanity of a catastrophic climate and is a goal for China in the future. Ecological space plays an important role in the realization of carbon neutrality, but the relationship between the structure of vegetation ecological space and vegetation carbon sequestration capacity has been the focus of research. In this study, we extracted the base data from MODIS products and other remote sensing products, and then combined them with the MCR model to construct a vegetation ecospatial network in the Yellow River Basin in 2018. Afterward, we calculated the topological indicators of ecological nodes in the network and analyzed the relationship between the carbon sequestration capacity (net biome productivity) of ecological nodes and these topological indicators in combination with the Biome-BGC model. The results showed that there was a negative linear correlation between the betweenness centrality of forest nodes and their carbon sequestration capacity in the Yellow River Basin (p < 0.05, R 2 = 0.59). On the other hand, there was a positive linear correlation between the clustering coefficient of grassland nodes and their carbon sequestration capacity (p < 0.01, R 2 = 0.49). In addition, we briefly evaluated the vegetation ecospatial network in the Yellow River BASIN and suggested its optimization direction under the background of carbon neutrality in the future. Increasing the carbon sequestration capacity of vegetation through the construction of national ecological projects is one of the ways to achieve carbon neutrality, and this study provides a reference for the planning of future national ecological projects in the Yellow River Basin. Furthermore, this is also a case study of the application of remote sensing in vegetation carbon budgeting.
Remotely sensed vegetation indices (VIs) have been widely used to estimate the aboveground biomass (AGB) carbon stock of coastal wetlands by establishing Vis-related linear models. However, these models always have high uncertainties due to the large spatial variation and fragmentation of coastal wetlands. In this paper, an efficient coastal wetland AGB model for the Bohami Rim coastal wetlands was presented based on multiple data sets. The model was developed statistically with 7 independent variables from 23 metrics derived from remote sensing, topography, and climate data. Compared to previous models, it had better performance, with a root mean square error and r value of 188.32 g m−2 and 0.74, respectively. Using the model, we firstly generated a regional coastal wetland AGB map with a 10 m spatial resolution. Based on the AGB map, the AGB carbon stock of the Bohai Rim coastal wetland was 2.11 Tg C in 2019. The study demonstrated that integrating emerging high spatial resolution multi-remote sensing data and several auxiliary metrics can effectively improve VIs-based coastal wetland AGB models. Such models with emerging freely available data sets will allow for the rapid monitoring and better understanding of the special role that “blue carbon” plays in global carbon cycle.
Malaysia has a large extent of forest cover that plays a crucial role in storing biomass carbon and enhancing carbon sink (carbon sequestration) and reducing atmospheric greenhouse gas emissions, which helps to reduce the negative impacts of global climate change. This article estimates the economic value of forest carbon stock and carbon value per hectare of forested area based on the price of removing per ton CO2eq in USD from 1990 to 2050. The economic value of biomass carbon stored in the forests is estimated at nearly USD 51 billion in 2020 and approximately USD 41 billion in 2050, whereas carbon value per hectare forest area is estimated at USD 2885 in 2020 and USD 2388 in 2050. If the BAU scenario of forest loss (converting forests to other land use) continues, the projected estimation of carbon stock and its economic value might fall until 2050 unless further initiatives on proper planning of forest management and ambitious policy implementation are taken. Instead, Malaysia’s CO2 emission growth started to fall after 2010 due to rising forest carbon sink of 282 million tons between 2011 and 2016, indicating a huge potential of Malaysian forests for future climate change mitigation. The estimated and projected value of carbon stock in Malaysian forest biomass, annual growth of forest carbon, forest carbon density and carbon sink would be useful for the better understanding of enhancing carbon sink by avoiding deforestation, sustainable forest management, forest conservation and protection, accurate reporting of national carbon inventories and policy-making decisions. The findings of this study could also be useful in meeting emission reduction targets and policy implementation related to climate change mitigation in Malaysia.
Global climate change caused by geological processes is one of the main causes of the 5 global mass extinctions in geological history. Human industrialization activities have caused serious damage to the ecosystem, the greenhouse effect of atmospheric CO2 has intensified, and the living environment is facing threats and challenges. Carbon neutrality is the active action and common goal of mankind in the face of the climate change crisis, therefore, probing into its theoretical and technological connotation, scientific and technological innovation system has far-reaching significance and broad prospects. Studies indicate that (1) Carbon neutrality reflects the theoretical connotations of “energy science” and “carbon neutrality science”, including technical connotations of carbon emission reduction, zero carbon emission, negative carbon emission, and carbon trading. (2) Carbon neutrality spawns new industries such as carbon industry centering on CO2 capture, utilization, and storage (CCUS, or CO2 capture and storage CCS), and hydrogen industry centering on green hydrogen. “Gray carbon” and “black carbon” are the two application attributes of CO2. “Carbon+”, “Carbon−”, and “Carbon=” are three carbon-neutral products and technologies. (3) China faces three major challenges in achieving the goal of carbon neutrality: first, energy transition is large in scale and the cycle is short; Second, there are many problems in the process of energy transition, such as security uncertainties, economic utilization, and unpredictable disruptive technologies; Third, after transition, we may face new key techno-logical “bottlenecks” and “broken chain” of key mineral resources. (4) Based on current knowledge to predict the top 10 disruptive technologies and industries in the energy field: underground coal gasification, in-situ conversion process of medium and low-mature shale oil, CCUS/CCS, hydrogen energy and fuel cells, bio-photovoltaic power generation, space-based solar power generation, optical storage smart micro-grid, super energy storage, controllable nuclear fusion, wisdom energy Internet. Five strategic projects will be implemented, including energy conservation and efficiency improvement, carbon reduction and sequestration, scientific and technological innovation, emergency reserve and policy support. (5) In the future, different types of energy will have different orientations. Coal will play the role of ensuring the national energy strategy “reserve” and “guarantee the bottom line”. Petroleum will play the role of ensuring national energy security “urgent need” and the “cornerstone” of raw materials in people's livelihood. Natural gas will play the role in ensuring national energy “safety” and “best partner” of new energy. New energy will play the role in ensuring the “replacement” and “main force” of the national energy strategy. (6) Carbon neutrality is a major practice of the green industrial revolution, carbon reduction energy revolution, and ecological technology revolution, which will bring new and profound changes to human society, the environment and the economy. (7) Carbon neutrality needs to follow the four principles of “disruptive breakthroughs in technology, guarantee of energy security, realization of economic feasibility, and controllable social stability”. We should rely on technological innovation and management changes to ensure the realization of national energy “independence” and carbon neutrality goal, and make China's contribution to the construction of a livable earth, green development, and ecological civilization.
Significance
Only 22 states in the United States have climate action plans, and of these, only six consider carbon mitigation, negative emissions, and equity issues. In the absence of robust federal or state policy action, there is a need for subnational carbon abatement planning. However, many of the most robust frameworks for carbon abatement are at a global or national scale. We provide a framework for localizing an existing global roadmap of climate solutions for Georgia, a state located in the southeastern United States. We thereby provide a replicable model that documents how subnational actors can evaluate high-potential emission reduction and carbon removal solutions while considering systems of solutions and taking into account social, ecological, and technological issues and priorities.
The literature examining the importance of industrial agglomeration in innovation performance has expanded greatly in recent years, but the impact of industrial agglomeration, especially high-tech industrial agglomeration on regional innovation convergence, has been neglected. Using quantitative data from 30 provinces in China pertaining to the period 2005–2016, in this article, we analyze regional innovation convergence by focusing on three different types of convergence: σ-convergence, absolute σ-convergence, and conditional β-convergence. On the basis of the spatial effects, this article empirically investigates the impact of high-tech industrial agglomeration on regional innovation convergence in China by using spatial econometric models. The empirical results show that there is significant spatial autocorrelation in regional innovation. Thus, in the assessment of regional innovation convergence, the spatial effects should not be neglected. Moreover, our results demonstrate that regional innovation exists three different types of convergence (i.e., σ-convergence, absolute β-convergence, and conditional β-convergence). In addition, high-tech industrial agglomeration can promote regional innovation convergence. Finally, the grouping of high-tech industries into five subindustries shows that industrial agglomeration has different effects on regional innovation convergence. Overall, our findings provide convincing empirical evidence of the relationship between the high-tech industrial agglomeration and regional innovation convergence and valuable insights into how to realize regional innovation convergence.
Tropical secondary forests sequester carbon up to 20 times faster than old-growth forests. This rate does not capture spatial regrowth patterns due to environmental and disturbance drivers. Here we quantify the influence of such drivers on the rate and spatial patterns of regrowth in the Brazilian Amazon using satellite data. Carbon sequestration rates of young secondary forests (<20 years) in the west are ~60% higher (3.0 ± 1.0 Mg C ha−1 yr−1) compared to those in the east (1.3 ± 0.3 Mg C ha−1 yr−1). Disturbances reduce regrowth rates by 8–55%. The 2017 secondary forest carbon stock, of 294 Tg C, could be 8% higher by avoiding fires and repeated deforestation. Maintaining the 2017 secondary forest area has the potential to accumulate ~19.0 Tg C yr−1 until 2030, contributing ~5.5% to Brazil’s 2030 net emissions reduction target. Implementing legal mechanisms to protect and expand secondary forests whilst supporting old-growth conservation is, therefore, key to realising their potential as a nature-based climate solution.
Limiting the rise in global mean temperatures relies on reducing carbon dioxide (CO2) emissions and on the removal of CO2 by land carbon sinks. China is currently the single largest emitter of CO2, responsible for approximately 27 per cent (2.67 petagrams of carbon per year) of global fossil fuel emissions in 2017¹. Understanding of Chinese land biosphere fluxes has been hampered by sparse data coverage2–4, which has resulted in a wide range of a posteriori estimates of flux. Here we present recently available data on the atmospheric mole fraction of CO2, measured from six sites across China during 2009 to 2016. Using these data, we estimate a mean Chinese land biosphere sink of −1.11 ± 0.38 petagrams of carbon per year during 2010 to 2016, equivalent to about 45 per cent of our estimate of annual Chinese anthropogenic emissions over that period. Our estimate reflects a previously underestimated land carbon sink over southwest China (Yunnan, Guizhou and Guangxi provinces) throughout the year, and over northeast China (especially Heilongjiang and Jilin provinces) during summer months. These provinces have established a pattern of rapid afforestation of progressively larger regions5,6, with provincial forest areas increasing by between 0.04 million and 0.44 million hectares per year over the past 10 to 15 years. These large-scale changes reflect the expansion of fast-growing plantation forests that contribute to timber exports and the domestic production of paper⁷. Space-borne observations of vegetation greenness show a large increase with time over this study period, supporting the timing and increase in the land carbon sink over these afforestation regions.
With economic growth in many developing countries, not all are making similar progress with regard to material and environmental efficiencies. This study examines material use and CO2 emission patterns and intensities from 1971 to 2015 in a typical developing country, Pakistan, and investigates national‐level and multi‐country‐level efficiency improvements using data envelopment analysis. The results are used to derive key policy insights for a sustainable economic transition with higher resource and carbon efficiencies. Results show that material intensity has reduced by 39.1% while CO2 intensity has risen by 21.5% in the country. Pakistan, when compared with its top 10 export countries, was relatively more material and CO2 intensive. National‐level efficiency was found to be low in most of the periods due to material/energy intensive agriculture and industries, low value‐added exports, etc. Insights from the national‐level efficiency analysis indicate that surging CO2 intensities have started to decline since 2010 and the economy has greatly stabilized. Multi‐country analysis revealed that the efficiency gap between Pakistan and its developed export countries (such as the United Kingdom and France) has widened during the study period. Insights from the multi‐country analysis suggest that the economic growth and industrialization improves material and environmental efficiencies to some extent, yet these improvements are not equally distributed among all countries. As a way forward, integrated policies on sustainable resource consumption, carbon mitigation, and economic growth are necessary for accruing higher benefits from rising global trade and resource connectedness.
Atmospheric carbon dioxide concentration ([CO2]) is increasing, which increases leaf‐scale photosynthesis and intrinsic water‐use efficiency. These direct responses have the potential to increase plant growth, vegetation biomass, and soil organic matter; transferring carbon from the atmosphere into terrestrial ecosystems (a carbon sink). A substantial global terrestrial carbon sink would slow the rate of [CO2] increase and thus climate change. However, ecosystem CO2 responses are complex or confounded by concurrent changes in multiple agents of global change and evidence for a [CO2]‐driven terrestrial carbon sink can appear contradictory. Here we synthesize theory and broad, multidisciplinary evidence for the effects of increasing [CO2] (iCO2) on the global terrestrial carbon sink. Evidence suggests a substantial increase in global photosynthesis since pre‐industrial times. Established theory, supported by experiments, indicates that iCO2 is likely responsible for about half of the increase. Global carbon budgeting, atmospheric data, and forest inventories indicate a historical carbon sink, and these apparent iCO2 responses are high in comparison to experiments and predictions from theory. Plant mortality and soil carbon iCO2 responses are highly uncertain. In conclusion, a range of evidence supports a positive terrestrial carbon sink in response to iCO2, albeit with uncertain magnitude and strong suggestion of a role for additional agents of global change.
Carbon sequestration through tropical reforestation and natural regeneration could make an important contribution to climate change mitigation, given that forest cover in many tropical regions increased during the early part of the 21st century. The size of this carbon sink will depend on the degree to which second-growth forests are permanent and protected from re-clearing. Yet few studies have assessed permanence of reforestation, especially not at a large spatial scale. Here, we analyzed a 14-year time series (2001–2014) of remotely sensed land-cover data, covering all tropical Latin America and the Caribbean, to quantify the extent of second-growth forest permanence. Our results show that in many cases, reforestation in Latin America and the Caribbean during the early 21st century reversed by 2014, limiting carbon sequestration. In fact, reversals of reforestation, in which some or all gains in forest cover in the early 2000s were subsequently lost, were ten times more common than sustained increases in forest cover. Had reversals of reforestation been avoided, forests could have sequestered 0.58 Pg C, over four times more carbon than we estimate was sequestered after accounting for impermanence (0.14 Pg), representing a loss of 75% of carbon sequestration potential. Differences in the prevalence of reforestation reversals across countries suggest an important role for socio-economic, political, and ecological context, with political transitions and instability increasing the likelihood of reversals. These findings suggest that national commitments to reforestation may fall short of their carbon sequestration goals without provisions to ensure long-term permanence of new forests.
The climate has changed significantly under the influence of human behavior. And first of all, this is due to the change in the proportionality and concentration of greenhouse gases in the atmosphere (water vapor, carbon dioxide, methane, ozone, PFC (perfluorocarbons). This paper analyzes the dynamics of greenhouse gas emissions. Climate change has many consequences on human health throughout the world, especially in African countries. The growth of greenhouse gas emissions is viewed as a cause of infectious and non-infectious diseases, negative effects on nutrition, water security and other social disruptions. The global average temperature gradually increases, and the atmospheric CO2 concentration has exceeded 400 ppm due to the intensification of greenhouse effect. The method of energy balance was featured to simulate the trends in Greenhouse Gas Emission Forecast in different sectors until 2030. Through sensitivity analysis, we found that the reduction of anthropogenic CO2 emissions from people (cars and households) would deescalate the consequences of the above trends. Emissions are mostly associated with industries, which can be reduced if local Government will want to achieve the Paris Agreement goal. © 2020 by author(s) and VsI Entrepreneurship and Sustainability Center.
The development of appropriate tools to quantify long‐term carbon (C) budgets following forest transitions, that is, shifts from deforestation to afforestation, and to identify their drivers are key issues for forging sustainable land‐based climate‐change mitigation strategies. Here, we develop a new modeling approach, CRAFT (CaRbon Accumulation in ForesTs) based on widely available input data to study the C dynamics in French forests at the regional scale from 1850 to 2015. The model is composed of two interconnected modules which integrate biomass stocks and flows (Module 1) with litter and soil organic C (Module 2) and build upon previously established coupled climate‐vegetation models. Our model allows to develop a comprehensive understanding of forest C dynamics by systematically depicting the integrated impact of environmental changes and land use. Model outputs were compared to empirical data of C stocks in forest biomass and soils, available for recent decades from inventories, and to a long‐term simulation using a bookkeeping model. The CRAFT model reliably simulates the C dynamics during France's forest transition and reproduces C‐fluxes and stocks reported in the forest and soil inventories, in contrast to a widely used bookkeeping model which strictly only depicts C‐fluxes due to wood extraction. Model results show that like in several other industrialized countries, a sharp increase in forest biomass and SOC stocks resulted from forest area expansion and, especially after 1960, from tree growth resulting in vegetation thickening (on average 7.8 Mt C/year over the whole period). The difference between the bookkeeping model, 0.3 Mt C/year in 1850 and 21 Mt C/year in 2015, can be attributed to environmental and land management changes. The CRAFT model opens new grounds for better quantifying long‐term forest C dynamics and investigating the relative effects of land use, land management, and environmental change.
In recent years, climate change and carbon sinks have been widely studied by the academic community, and relevant research results have emerged in abundance. In this paper, a scientometric analysis of 747 academic works published between 1991 and 2018 related to climate change and carbon sinks is presented to characterize the intellectual landscape by identifying and revealing the basic characteristics, research power, intellectual base, research topic evolution, and research hotspots in this field. The results show that ① the number of publications in this field has increased rapidly and the field has become increasingly interdisciplinary; ② the most productive authors and institutions in this subject area are in the USA, China, Canada, Australia, and European countries, and the cooperation between these researchers is closer than other researchers in the field; ③ 11 of the 747 papers analyzed in this study have played a key role in the evolution of the field; and ④ in this paper, we divide research hotspots into three decade-long phases (1991-1999, 2000-2010, and 2011-present). Drought problems have attracted more and more attention from scholars. In the end, given the current trend of the studies, we conclude a list of research potentials of climate change and carbon sinks in the future. This paper presents an in-depth analysis of climate change and carbon sink research to better understand the global trends and directions that have emerged in this field over the past 28 years, which can also provide reference for future research in this field.
The monitoring of particulate organic carbon (POC) flux at the bottom of the euphotic layer in global ocean using remote sensing satellite data plays an important role in clarifying and evaluating the ocean carbon cycle. Based on the in situ POC flux data, this paper evaluated various estimation models. The global ocean POC flux from 2003 to 2018 was calculated using the optimal model, and its temporal and spatial variation characteristics were analyzed. In general, the annual average of global ocean POC flux is about 8.5–14.3 Gt C yr − 1 for period of 2003–2018. In the spatial dimension, the POC flux in the mid-latitude ocean (30–60°) is higher than that in the low-latitude (0–30°). The POC flux in Continental Margins with water depth less than 2000 m accounted for 30% of global ocean, which should receive more attention in global carbon cycle research. In the time dimension, the global POC flux decreases year by year generally, but the POC flux abnormally decreases during El Niño and increases during La Niña. In addition, due to global warming, sea ice melting, and bipolar sea area expansion, POC flux in high-latitude oceans (60–90°) is increasing year by year.
Air quality in small urban parks improves rapidly with distance from surrounding streets. This arises because air pollutants disperse within parks where there are few sources. This was traditionally thought to arise from pollutant uptake by trees, but they can also reduce wind speed and potentially trap pollutants. It is increasingly evident that relatively little pollution is absorbed by trees over short distances typical of small urban parks. Nevertheless, trees and park infrastructure, also constrain the distribution of park users and thus lower their exposure. In this paper, we explore the exposure to traffic-derived air pollutants in the Hong Kong parks (Sha Tin and Sham Shui Po) and examine the way in which PM 2.5 concentration and user distribution is affected by the spatial layout of park features. The modelled pollutant distribution was validated against measurements made in Sha Tin Park. Population-weighted exposure to traffic-derived pollution was quantified by overlapping pollutant and park user distribution. The results reveal how different design features (i.e. vegetation, earth berms and recreation areas) affect exposure during individual time period; most positively in Sha Tin Park where the design leads to a > 50% reduction in exposure, early morning. In Sham Shui Po Park, exposure increases as park users are often attracted to facilities near a busy trunk road. This study reveals the heterogeneity of park user exposure to traffic-derived air pollution, which leads to uncertainty in health benefits provided by urban parks and suggests fine-scale exposure considered in thoughtful park design.
Forests are the potential source for managing carbon sequestration, regulating climate variations and balancing universal carbon equilibrium between sources and sinks. Further, assessment of biomass, carbon stock, and its spatial distribution is prerequisite for monitoring the health of forest ecosystem. Moreover, vegetation field inventories are valuable source of data for estimating aboveground biomass (AGB), density, and the carbon stored in biomass of forest vegetation. In view of the importance of biomass, the present study makes an attempt to estimate temporal AGB of Tripura State, India, using Moderate Resolution Imaging Spectroradiometer (MODIS), normalized difference vegetation index (NDVI), leaf area index (LAI) and the field inventory data through geospatial techniques. A model was developed for establishing the relationship between biomass, LAI, and NDVI in the selected study site. The study also aimed to improve method for quantifying and verifying inventory-based biomass stock estimation. The results demonstrate the correlation value obtained between LAI and NDVI were 0.87 and 0.53 for the years 2011 and 2014, respectively. The correlation value between estimated AGB with LAI were found as 0.66 and 0.69, while with NDVI, the values were obtained as 0.64 and 0.94 for the years 2011 and 2014, respectively. The regression model of measured biomass with MODIS NDVI and LAI was developed for the data obtained during the period 2011–2014. The developed model was used to estimate the spatial distribution of biomass and its relationship between LAI and NDVI. The R² values obtained were 0.832 for estimated and the measured AGB during the training and 0.826 for the validation. The results indicate that the methodology adopted in this study can help in selecting best fit model for analyzing relationship between AGB and NDVI/LAI and for estimating biomass using allometric equation at various spatial scales. The developed output thematic map showed an average biomass distribution of 32–94 Mg ha⁻¹. The highest biomass values (72–95 Mg ha ⁻¹) was confined to the dense region of the forest while the lowest biomass values (32–46 Mg ha⁻¹) was identified in the outer regions of the study site.
Terrestrial and oceanic carbon sinks together sequester >50% of the anthropogenic emissions, and the major uncertainty in the global carbon budget is related to the terrestrial carbon cycle. Hence, it is important to understand the major drivers of the land carbon uptake to make informed decisions on climate change mitigation policies. In this paper, we assess the major drivers of the land carbon uptake—CO 2 fertilization, nitrogen deposition, climate change, and land use/land cover changes (LULCC)—from existing literature for the historical period and future scenarios, focusing on the results from fifth Coupled Models Intercomparison Project (CMIP5). The existing literature shows that the LULCC fluxes have led to a decline in the terrestrial carbon stocks during the historical period, despite positive contributions from CO 2 fertilization and nitrogen deposition. However, several studies find increases in the land carbon sink in recent decades and suggest that CO 2 fertilization is the primary driver (up to 85%) of this increase followed by nitrogen deposition (∼10%–20%). For the 21st century, terrestrial carbon stocks are projected to increase in the majority of CMIP5 simulations under the representative concentration pathway 2.6 (RCP2.6), RCP4.5, and RCP8.5 scenarios, mainly due to CO 2 fertilization. These projections indicate that the effects of nitrogen deposition in future scenarios are small (∼2%–10%), and climate warming would lead to a loss of land carbon. The vast majority of the studies consider the effects of only one or two of the drivers, impairing comprehensive assessments of the relative contributions of the drivers. Further, the broad range in magnitudes and scenario/model dependence of the sensitivity factors pose challenges in unambiguous projections of land carbon uptake. Improved representation of processes such as LULCC, fires, nutrient limitation and permafrost thawing in the models are necessary to constrain the present-day carbon cycle and for more accurate future projections.
Achieving carbon neutrality is an urgent, complex and arduous task in China. How to effectively exert carbon sequestration and improve carbon sequestration capacity of urban ecosystems should be solved. Compared with other terrestrial ecosystem types, frequent anthropogenic activities lead to more abundant carbon sink elements of urban ecosystems and more complex factors affecting their carbon sequestration capacity. Based on researches at multiple spatial and temporal scales, we analyzed key factors affecting the carbon sequestration capacity of urban ecosystems from different perspectives. We illuminated the composition and characteristics of carbon sinks of urban ecosystems, summarized the methods and characteristics of carbon sequestration capacity of urban ecosystems, and revealed the impact factors of carbon sequestration capacity of different carbon sink elements and the comprehensive impact factors of carbon sinks of urban ecosystems under the influence of human activities. With the continuous improved understanding of carbon sinks of urban ecosystems, it is necessary to further improve the accounting method of carbon sequestration capacity of artificial carbon sink systems, explore the key impact factors of comprehensive carbon sequestration capacity, change the research method from global to spatially weighted, discover the spatial coupling relationship between artificial and natural carbon sink systems, find out the optimal artificial-natural spatial configuration to achieve carbon sequestration capacity enhancement, break the limitations of increasing carbon sink of urban ecosystems, and finally contribute to the achievement of the urban carbon neutrality goal.
Urban flood is one of the most frequent and deadly natural disasters in the world, seriously affecting urban sustainability and people's well-being in China. As the largest developing country in the world, China urgently needs to improve its urban flood resilience. Previous studies related to urban flood resilience are mostly focused on its assessment method and simulation. However, few studies directly aim to reveal the influencing factors of urban flood resilience and their inner relationships. In order to make a significant contribution to the long-term improvement of urban flood resilience in the context of global climate change and urbanization, it is crucial to explore the influencing mechanisms of urban flood resilience. This study aims to identify key influencing factors and their interactions on urban flood resilience in China. To this end, a conceptual framework based on Pressure-State-Response model and Social-Economic-Natural Complex Ecosystem theory (PSR-SENCE model) are established and 24 factors are identified within three dimensions. The relationships between the factors are tested using a fuzzy-DEMATEL method. The results reveal that factors in pressure and response dimensions have a greater impact on the whole system, while the factors in the state dimension are more influenced by the other two dimensions. The results identify 14 critical factors, with four detailed influence paths discussed among the different dimensions. Accordingly, the implications for improving urban flood resilience are discussed within the context of the key influencing paths. The study provides a theoretical basis and approach to directly explore how the factors influencing urban flood resilience and proposes specific impact paths and improvement implications.
In the social context of mitigating climate change and achieving carbon neutrality, the improvement of carbon emissions efficiency and the protection of biological carbon sequestration have emerged as hot topics recently due to their prospects in carbon dioxide emissions reductions. A large volume of studies has identified the spatial distribution characteristics and influencing factors of carbon emissions efficiency. The contributions of our study lied in constructing a system to measure net carbon sink efficiency. Secondly, this study discussed the carbon neutrality performance of Chinese cities from three different aspects of carbon dioxide emissions, carbon sequestration of vegetation and net carbon sink efficiency. Thirdly, this paper identified the influencing factors of net carbon sink efficiency, and examined the direct and indirect effect of different factors. For this purpose, we evaluated the net carbon sink efficiency of 285 cities in China from 2012 to 2017 using a slacks-based measure model, and explored its spatial distribution characteristics, then employed a spatial Durbin model to explore the influencing factors of net carbon sink efficiency. Our main findings indicate that the net carbon sink efficiency steadily increased during the study period, whereas their spatial characteristics were “high at both ends and low in the middle” from the south to the north. There is a significant spatial autocorrelation in the net carbon sink efficiency of Chinese cities. Several kinds of measures can be applied to promote net carbon sink efficiency, such as increasing the proportion of tertiary industry, promoting economic growth, attracting foreign direct investment, increasing road area, promoting technological progress and strengthening environmental regulation. However, the increase of urban population may decrease efficiency. Nevertheless, an obvious spatial spillover effect exists in the net carbon sink efficiency of Chinese cities. The results can provide policy recommendations for the government to formulate differentiated carbon neutralization policies.
The Chinese government has made a strategic decision to reach ‘carbon neutrality’ before 2060. China’s terrestrial ecosystem carbon sink is currently offsetting 7–15% of national anthropogenic emissions and has received widespread attention regarding its role in the ‘carbon neutrality’ strategy. We provide perspectives on this question by inferring from the fundamental principles of terrestrial ecosystem carbon cycles. We first elucidate the basic ecological theory that, over the long-term succession of ecosystem without regenerative disturbances, the carbon sink of a given ecosystem will inevitably approach zero as the ecosystem reaches its equilibrium state or climax. In this sense, we argue that the currently observed global terrestrial carbon sink largely emerges from the processes of carbon uptake and release of ecosystem responding to environmental changes and, as such, the carbon sink is never an intrinsic ecosystem function. We further elaborate on the long-term effects of atmospheric CO2 changes and afforestation on China’s terrestrial carbon sink: the enhancement of the terrestrial carbon sink by the CO2 fertilization effect will diminish as the growth of the atmospheric CO2 slows down, or completely stops, depending on international efforts to combat climate change, and carbon sinks induced by ecological engineering, such as afforestation, will also decline as forest ecosystems become mature and reach their late-successional stage. We conclude that terrestrial ecosystems have nonetheless an important role to play to gain time for industrial emission reduction during the implementation of the ‘carbon neutrality’ strategy. In addition, science-based ecological engineering measures including afforestation and forest management could be used to elongate the time of ecosystem carbon sink service. We propose that the terrestrial carbon sink pathway should be optimized, by addressing the questions of ‘when’ and ‘where’ to plan afforestation projects, in order to effectively strengthen the terrestrial ecosystem carbon sink and maximize its contribution to the realization of the ‘carbon neutrality’ strategy.
China announced its national goal to reach the peak of carbon emission by 2030 and achieve carbon neutrality by 2060, during the General Assembly of the United Nations in September 2020. In this context, the potential of the carbon sink in China’s terrestrial ecosystems to mitigate anthropogenic carbon emissions has attracted unprecedented attention from scientific communities, policy makers and the public. Here, we reviewed the assessments on China’s terrestrial ecosystem carbon sink, with focus on the principles, frameworks and methods of terrestrial ecosystem carbon sink estimates, as well as the recent progress and existing problems. Looking forward, we identified critical issues for improving the accuracy and precision of China’s terrestrial ecosystem carbon sink, in order to serve the more realistic policy making in pathways to achieve carbon neutrality for China.
Forest plays an important role in reducing pressure on the natural environment, weaking the influence of greenhouse effects, and sequestrating atmospheric carbon dioxide. So far, due to the lack of complete understanding of forest ecosystem processes and the limitations on the scope of application of evaluation methods, there are still great uncertainties in the researches on carbon fluxes of forest ecosystems in China at the national level. In this study, an individual tree species FORCCHN model, which could flexibly use the inventory data as the initial field (more accurately) or use the remote sensing information to inverse initial field was applied. The dynamics of key carbon cycle fluxes (net primary productivity (NPP) and net ecosystem productivity (NEP)) and carbon sequestration of forest ecosystems in China from 1982 to 2019 were simulated based on remote sensing data and FORCCHN model. The results showed that forest ecosystems in China had great carbon sequestration potential over the past 39 years. From 1982 to 2019, the NPP of Chinese forests presented a fluctuated increase. Total NPP from 2011 to 2019 ranged from 0.91 PgC·a⁻¹ to 1.14 PgC·a⁻¹. Annual average NEP of forest ecosystems in China from 2011 to 2019 was 0.199 PgC·a⁻¹ (1Pg = 10¹⁵ g). Influenced by climate, soil and vegetation, carbon sequestration potential in Chinese forest ecosystems presented obvious regional differences in space. The spatial distribution of NEP gradually increased from Northwest to Southeast China. From 2011 to 2019, forests in Yunnan Province had the strongest carbon storage capacity (72.79 TgC·a⁻¹, 1Tg = 10¹² g), followed by forests in Guangxi (18.49 TgC·a⁻¹) and forests in Guangdong (10.01 TgC·a⁻¹). Our results not only address concerns about carbon sequestration but also reflect the importance of Chinese forest resources in the development of the national economy and society.
To explore available methods for assessing the orientation, magnitude, and role of urban forests in abating climate change, i-Tree Eco and Kriging interpolation were employed to quantify and map the carbon storage and sequestration capability of trees in urban forests. Specifically, urban tree field data were collected from 981 sample plots throughout five types of urban forests in the built-up area of Beijing, China, and used to estimate carbon storage and sequestration within each individual plot and the area as a whole. These data were subsequently subjected to Kriging interpolation to map carbon storage and sequestration within the study area. The results showed that the carbon storage and sequestration patterns in the urban forests in Beijing exhibit noticeable spatial heterogeneity, and that there is a clear, statistically significant distribution of high and low value areas. Furthermore, urban planning, the degree of urbanization, and the urban forest structure effect the carbon spatial distribution. This work provides a reference for prudent planning and construction of urban forests and will aid decision-makers in designing eco-friendly urban environments.
Mangrove forests are among the highest carbon (C) sinks in the tropics and subtropics worldwide. Net primary productivity (NPP) is estimated by the permanent plot method with litterfall plus incremental growth (LG) and has great significance for the evaluation of the carbon sequestration capacity of forests. Here, we developed a new high-resolution method, sap flow investigation (SF), for the evaluation of carbon sequestration capacity. We also compared the forest carbon sequestration capacity estimated using two NPP estimation methods, stand water use using SF and light attenuation/gas exchange (LA), with traditional permanent plots using the LG method in four typical mangrove forests in the Futian Mangrove Reserve of Shenzhen City, China. The LG results showed that mangrove forests had NPPs ranging from 7.67 to 11.87 Mg C ha⁻¹ yr⁻¹, with species-specific differences. Among the three methods, the LG method is the most widely used, although it is costly and difficult to implement in the field. The LA results showed seasonal variation of NPP, with 4.69 g C m⁻² d⁻¹ in summer and 2.02 g C m⁻² d⁻¹ in winter. The LA method is relatively simple, but it requires a homogeneous canopy structure with a simple canopy extinction coefficient, which is suitable for mangroves with homogenous canopy structures. Although costly, the most convenient and efficient method is the SF method, which can realize continuous and high-precision dynamic NPP monitoring at the stand scale. After standardization by the LG method, the two high-resolution NPP methods could be used in mangrove forests with different time scales. For the global scale, after modification by the correction method provided in our study, the error caused by the determination method could be eliminated, which could make the global database more plentiful and accurate.
The spatial characteristics of carbon emissions form the basis for exploring carbon neutrality measures for different regions. As the second largest carbon emission source globally, agricultural carbon emissions should not be ignored. This paper used panel data from 2009 to 2019 to calculate the agricultural carbon emissions of 30 provinces in China, and used the ML index, spatial Morans’I index and three convergence indices to analyze the dynamic changes and spatial pattern of China’s agricultural carbon emission performance (ACEP). The results showed that: (i), China's ACEP has increased by 1.5% from 2009 to 2019, following a spatial pattern of eastern (1.041) > western (1.020) > central (0.974);(ii) the contribution of technological progress to China's ACEP was 1.035, exceeding 1, and thus indicating that technological progress can improve ACEP, while the contribution of efficiency changes was only 0.991; (iii) China’s ACEP has exhibited a spatial aggregation effect over the last 10 years (P < 0.05), but the value of Moran’s I index dropped from 0.265 in 2009 to 0.202 in 2019, which indicates that the spatial aggregation of ACEP is weakening; and (iv) the ML index for 30 provinces in China showed σ convergence, which indicates that the ACEP is improving, while there is absolute β convergence and conditional β convergence, which indicates a “catch-up effect” among regions. The results indicate that China’s ACEP is likely to increase further in terms of spatial scope and temporal trends.
Spatial weights matrices used in quantitative geography furnish maps with their individual latent eigenvectors, whose geographic distributions portray distinct spatial autocorrelation (SA) components. These polygon patterns on maps have specific meaning, partially in terms of geographic scale, which this article describes. The goal of this description is to enable spatial analysts to better understand and interpret these maps individually, as well as mixtures of them, when accounting for SA in a spatial analysis. Linear combinations of Moran eigenvector maps supply a powerful and relatively simple tool that can explain SA in regression residuals, with an ability to render reasonably accurate reproductions of empirical geographic distributions with or without the aid of substantive covariates. The focus of this article is positive SA, the most commonly encountered nature of autocorrelation in georeferenced data. The principal innovative contribution of this article is establishing a better clarification of what the synthetic SA variates extracted from spatial weights matrices epitomize with regard to global, regional, and local clusters of similar values on a map. This article shows that the Getis-Ord Gi* statistic provides a useful tool for classifying Moran eigenvector maps into these three qualitative categories, illustrating findings with a range of specimen geographic landscapes.
Soil aggregate stability is an important index for predicting soil water loss and soil erosion resistance. Plant roots effectively control soil erosion and stabilize soil structure, which has a crucial influence on the formation of aggregates and soil organic carbon (SOC) sequestration. We examined how rhizosphere effects influence soil aggregate stability and its associated SOC contents and δ¹³C values, following a proposed extended model of carbon (C) flows between the aggregate size classes in the root systems based on ¹³C fractionation in each step of SOC formation. The results show that the rhizosphere effects significantly improved the stability of aggregates. The mean weight diameter (MWD) and geometric mean diameter (GMD) of rhizosphere soil aggregates were significantly higher than those of non-rhizosphere soil aggregates associated with plants with fibrous roots. SOC levels of all size aggregates in the rhizosphere soil of both fibrous and tap root plants were higher than those of non-rhizosphere soil. Moreover, SOC contents increased in the order of silt-clay particles (SCP, <0.05 mm), microaggregates (MIA, 0.05-0.25 mm) and small macroaggregates (SMA, 0.25-1 mm), and then decreased from SMA to large macroaggregates (LMA,> 1 mm). The δ¹³C values in non-rhizosphere soil were generally higher than those in rhizosphere soil in aggregates of the same size class, especially in the tap root plants. Except for the rhizosphere soil of fibrous root plants, the other three soil types (rhizosphere and non-rhizosphere soil of tap root plants, and non-rhizosphere soil of fibrous root plants) were shown to have aggregate δ¹³C values that decreased with increasing soil aggregate size. Δ¹³C enrichment of the SOC fractions showed that the general flow direction of SOC was from rhizosphere to non-rhizosphere, and from large aggregates to small aggregates. The C flow in the aggregates of rhizosphere soil was clearly greater than that in the non-rhizosphere soil, especially with the fibrous root plants. These findings suggest that plant roots have the potential to regulate soil structural stability, and enhance soil erosion resistance and SOC sequestration.
The terrestrial ecosystem carbon cycle is a major contributing factor in the rise in global average temperature. Based on the net ecosystem production (NEP) calculation model and classifications, the spatial distribution patterns of carbon sources and sinks for vegetation in Central Asia are analyzed. The results show obvious vertical zonal characteristics in the distribution of carbon sources and sinks. Carbon source areas form the majority and are mainly located in south-central Kazakhstan and parts of Uzbekistan and Turkmenistan, while most carbon sink areas are located in northern Kazakhstan, Kyrghyzstan and Tajikistan. NEP shows a downward trend during 2000-2015, indicating decreasing capacities of low and high carbon sinks in forest land, sparse vegetation, and bare areas. Even a weakening in the carbon sink capacity resulted in no significant decrease, indicating instead a decline in grassland quality. The change in NEP matches the change in terrestrial net primary productivity (NPP). Water is the limiting factor for ecological attributes in arid and semi-arid areas, with drought influencing both the carbon budget and balance. These conclusions are critical for maintaining ecological stability and sustainable economic development in the Silk Road Economic Belt.
Risks to mitigation potential of forests
Much recent attention has focused on the potential of trees and forests to mitigate ongoing climate change by acting as sinks for carbon. Anderegg et al. review the growing evidence that forests' climate mitigation potential is increasingly at risk from a range of adversities that limit forest growth and health. These include physical factors such as drought and fire and biotic factors, including the depredations of insect herbivores and fungal pathogens. Full assessment and quantification of these risks, which themselves are influenced by climate, is key to achieving science-based policy outcomes for effective land and forest management.
Science , this issue p. eaaz7005
The Beijing-Tianjin-Hebei (BTH) urban agglomeration is the most polluted area of smog in China. The latest studies have been focusing on the influencing factors on the BTH's PM2.5 concentration in terms of industrial, social, and climatic conditions. However, the role of the urban forest system has not been thoroughly studied in air pollution control. This study focuses on the impact of forest city construction on BTH's PM2.5 concentration. According to the theoretical framework of the STIRPAT model, we used the spatial Durbin model of bidirectional fixed effect to empirically test the correlation between the BTH's PM2.5 concentration and the characteristic variables of forest cities. The research results show that improving urban green space, park green space, and investment of urban sanitation and environment facilities can reduce the PM2.5 concentration in the local and adjacent areas. This study proposes that the construction of forest cities should be further strengthened to alleviate urban air pollution in the BTH's coordinated development and thus improve regional air quality.
In the face of the intensifying process of urbanization and the increased incidence of pollen allergies among urban residents, there is still a need to continuously monitor the airborne concentration of allergenic plant pollen. Urban green spaces (UGS) are a desirable element of the urban fabric and necessary for the proper functioning of cities, but they are a rich source of allergenic pollen that may pose a certain risk to people visiting them. The main aim of this study was to analyse the airborne allergenic pollen content in parks of different types relative to a reference point located on the roof of a building. Moreover, this study investigated the relationship between tree canopy volume and the number of recorded airborne pollen grains (SPIn- Seasonal Pollen Integral), and these parameters were compared with the potential impact of vegetation in the parks studied through the Index of Urban Green Zones Allergenicity (IUGZA). Aerobiological monitoring was carried out in Rzeszów, SE Poland in 2016. A volumetric Hirst-type device was used. The pollen seasons of many taxa largely overlapped at each site where the monitoring was carried out, but the concentration values clearly differed. Tree pollen concentration values were not dependent on total canopy volume, and the greatest disproportions were found for Acer, Betula, Quercus, and Tilia pollen. This may be due to the fact that a solitary tree produces more pollen than a tree growing near others of the same species. The downtown park, surrounded by densely built-up areas, exhibited the highest allergenic potential, and the concentration of pollen, in particular tree pollen, was highest there. It is undesirable to plant hedges of allergenic plants, as they are a rich local source of pollen. Aerobiological monitoring carried out in urban parks provides information about the real threat of allergenic pollen to park visitors.