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Background: China has made great progress in ecological restoration. However, there have been no analyses on ecological restoration for specific terrestrial ecosystems. This study identified the important knowledge gaps and advances related to terrestrial ecological restoration in China. Results: 7973 papers published between 1978 and 2020 were investigated and about 962 articles were used in this analysis after manually screening. Since the first large national ecological restoration project in 1978, the most frequently studied ecosystem has shifted from farmland ecosystems in 1978–2000 to forest ecosystems after 2000. Forests were the most common ecosystem type investigated, while less attention was paid to wetlands and riparian systems. Meanwhile, the most common ecological issue shifted from environmental pollution in 1978–2000 to the declining resource-carrying capacity of ecosystems after 2000. Studies of ecoregions on the Loess Plateau catchment accounted for more than 40% of papers reviewed in this study, with predominant emphasis on soil and water conservation functionality. Besides, revegetation and afforestation characterized most ecological restoration projects in China, but the natural restoration was relatively less adopted. Additionally, the important tool of reference ecosystem was only used in four studies. Conclusions: Ecological restoration has made significant progress in China. We investigated how the ecological restoration can be implemented more effectively. More projects should be implemented for restorative work in wetlands and riparian systems in future. The tradeoff between restorative activities, water resources, and carbon sink needs further research efforts. More emphasis on biodiversity conservation is warranted. Newly developed theory (e.g., stepwise ecological restoration) and the recently issued Chinese National Guidelines for Ecological Restoration Projects should be more effectively implemented in future restorative works. This study provides essential information for future restorative work in China. It also provides insights into the development of policy relevant to restoration and adaptive management during the U.N. restoration decade. [ABSTRACT FROM AUTHOR]

Global climate change caused by greenhouse gas emissions has a direct impact on the sustainable development of human society and has gained widespread concern globally. Biological carbon sequestration measures, mainly forests, are conducive to improving the ecological carbon sink capacity and play an important role in mitigating global climate change. Therefore, assessing the efficiency of forest carbon storage (FCS) is key. In view of the lack of evaluation methods for forest carbon storage efficiency (FCSE) on a large spatial scale and long time series, a method based on Data Envelopment Analysis (DEA) was proposed in this paper. The FCS was calculated using the forest storage expansion method, and the FCSE was calculated using the DEA-Malmquist index to solve the dynamic balance between regional forestry economic input and carbon storage output efficiency. The FCSE in Chinese provinces was analyzed. The results showed that from 1999 to 2018, China's FCS increased annually, from 7558.34 million tons to 9476.73 million tons, and the spatial distribution pattern of total FCS was always different among regions. The average TFP value of FCSE was 1.089, which proves that the FCSE in China has been on the rise in the past 20 years, but the efficiency growth differed between provinces and was affected by different factors such as technical efficiency and technological progress. [ABSTRACT FROM AUTHOR]

With rapid economic growth and urbanization, self-sufficiency in crop production has become central to China's agriculture policy. Accurate crop production statistics are essential for research, monitoring, and planning. Although researchers agree that China's statistical authority has considerably modernized over time, China's economic statistics have still been viewed as unreliable and often overstated to meet growth targets at different administrative levels. Recent increases in crop production reported by national statistics have also come under increasing scrutiny. This paper investigates crop production data quality from a planetary boundary perspective--comparing net primary production (NPP) harvested obtained from national statistics with satellite-driven NPP estimates that are supported by detailed observation of land cover, combined with observations on physical factors that limit plant growth. This approach provides a powerful means to check the plausibility of China's grain production statistics at different administrative levels that can generate insights about their discrepancies and can contribute to improved crop production measurements. We find some evidence of potential misreporting problems from the lower administration level where the risk of manipulation of statistics is higher. We also find problems from provincial-level major grain producers. These values can also affect the national totals. Although the numbers are affected by large uncertainties, we find that improving the spatial resolution of key agricultural parameters can greatly improve the reliability of the indicator that in turn can help improve data quality. More reliable production data will be vital for relevant research and provide better insights into food security problems, the carbon cycle, and sustainable development. [ABSTRACT FROM AUTHOR]

Carbon emissions pose a significant challenge to sustainable development, particularly for China, which is the world's largest emerging economy and is under pressure to achieve carbon neutrality and reduce emissions amid escalating human activities. The variation in economic development levels and carbon sequestration capacities among its provinces poses a significant hurdle. However, previous research has not adequately examined this dual discrepancy from the perspective of spatial heterogeneity, resulting in a lack of differentiated management of forest carbon sinks across diverse regions. Therefore, to mitigate this discrepancy, this study presents an assessment methodology that analyzes over 100 types of natural and plantation forests using forest age and biomass expansion factors. This study presents a model that can significantly support the efforts of both China and the whole world to achieve carbon neutrality through the improved management of forest carbon sinks. This approach facilitates the assessment of carbon offsets required to meet reduction targets, the development of a provincial framework for carbon intensity and sequestration, and the exploration of their potential for trading markets. Analysis is conducted using MATLAB. Key achievements of this study include the following: (1) The collection of a comprehensive carbon stock dataset for 50 natural and 57 plantation forest types in 31 provinces from 2009 to 2018, highlighting the significant role of new forests in carbon sequestration. (2) The development of a provincial carbon status scoring system that categorizes provinces as carbon-negative, carbon-balancing, or carbon-positive based on local forest sink data and carbon credit demand. (3) The formulation of the carbon intensity–carbon sink assessment (CISA) model, which suggests that provinces with middle- to upper-middle-level economies may have a prolonged need for carbon sink credits during their peak carbon phase. Furthermore, the results show that carbon trading may benefit Guangxi and Yunnan, but may also bring opportunities and risks to Hunan and Hubei. To address regional imbalances, this study advocates tailored policies: carbon-negative and carbon-balancing provinces should enhance carbon sink management, while carbon-positive provinces must focus on energy structure transformation to achieve sustainable development goals. [ABSTRACT FROM AUTHOR]

As the largest terrestrial organic carbon pool, soil organic carbon (SOC) plays an important role in the global carbon cycle, but it is easily affected by land use and climate change. The Huang-Huai-Hai Plain (HHHP) in China, which is dominated by dry farming, is experiencing rapid farmland loss and gain (farmland use transition), which may cause drastic changes in SOC storage. To clarify the effects of farmland use transition on SOC in dry farming areas, this study adopted a land use transition matrix and spatial analyst tool to explore the characteristics of farmland use transition and its effects on SOC content and stocks in the 200 cm soil layer in the HHHP from 2000 to 2020. The results showed that the farmland use transition in this area during that time period resulted in a net decrease of 16.06 × 103 km2 of farmland, of which urban built-up land and rural settlements led to a net reduction of farmland by 9.74 × 103 km2 and 6.43 × 103 km2, respectively, which was mainly affected by climate, topography, and economic factors. In addition, the farmland use transition resulted in a net increase in SOC storage of 6.13 Tg C, contributing 44.32% of the net increase. This is likely because the change in land use type led to a change in soil bulk density and soil gravel content while altering the SOC content, which in turn affected the SOC stock. This study has important implications for addressing global climate change and maintaining sustainable agricultural resources. [ABSTRACT FROM AUTHOR]

The ocean is a key component of the global carbon cycle. As climate change becomes increasingly severe, enhancing the ocean's carbon sink capacity is of great significance to achieving the "dual carbon" goal for China. As a major maritime province, Shandong is in an advantageous position to utilize the ocean to respond to climate change and achieve the national goals of carbon peaking and carbon neutrality. Focusing on consolidating and enhancing ocean carbon sink capabilities, Shandong needs to formulate a clear timetable and roadmap to promote blue carbon technology research and development, actively cultivate a blue carbon trading market, and tap the inner potential of ocean carbon sink. Shandong should also strengthen international cooperation to jointly construct a carbon-neutral global community. [ABSTRACT FROM AUTHOR]

Anthropogenic nitrogen (N) emissions to atmosphere have increased dramatically in China since 1980s, and this increase has aroused great concerns on its ecological impacts on terrestrial ecosystems. Previous studies have showed that terrestrial ecosystems in China are acting as a large carbon (C) sink, but its potential in the future remains largely uncertain. So far little work on the impacts of the N deposition on C sequestration in China’s terrestrial ecosystems has been assessed at a national scale. Aiming to assess and predict how ecological processes especially the C cycling respond to the increasing N deposition in China’s forests, recently researchers from Peking University and their partners have established a manipulation experimental network on the ecological effects of the N deposition: Nutrient Enrichment Experiments in China’s Forests Project (NEECF). The NEECF comprises 10 experiments at 7 sites located from north to south China, covering major zonal forest vegetation in eastern China from boreal forest in Greater Khingan Mountains to tropical forests in Hainan Island. This paper introduces the framework of the NEECF project and its potential policy implications. [ABSTRACT FROM AUTHOR]

To explore the role of forest carbon sinks in achieving carbon neutrality, the cointegration regression method and scenario analysis are utilized to forecast the long-term development trend of China's forest carbon sinks up to the year 2100 and their impact on carbon neutrality. The results show that: (1) Under routine, accelerated, and strengthened ecological civilization scenarios (or RECS, AECS, and SECS, respectively), China's forests are projected to absorb 531–645 million tons of carbon by 2050 and 2.32–4.69 billion tons of carbon by 2100, respectively, and the value of the strengthened scenario will be markedly higher than that of the routine scenario. (2) Driven by slower growth in forestry investment, China's forest carbon sinks growth in all three scenarios peak by 2050 and then slow in a U-trend, with the growth rate in the SECS 0.45 percentage points higher than that of AECS, and the growth rate in the AECS 0.44 percentage points higher than that of RECS. (3) Under SECS, forest carbon sinks can help China achieve its carbon neutrality goal in 2054 (before the target date of 2060) with cumulative forestry investment of 53.3 trillion yuan and an annual investment growth rate of about 6.3%. Therefore, this study provides a deeper understanding than previous works of the important role of forest carbon sinks in achieving carbon neutrality. [ABSTRACT FROM AUTHOR]

Under the threat of global climate change, China has proposed a dual carbon goal of peak carbon and carbon neutrality. As the vital carrier for territorial spatial planning, production–living–ecological (PLE) spaces drive carbon emissions and are important to the dual carbon goals. In this study, carbon emissions and sinks of PLE spaces in cities in Heilongjiang Province from 2005 to 2020 were calculated and spatial–temporal changes were analyzed. The carbon emission structure was analyzed in segmentation sectors. The land use changes and socioeconomic factors on carbon emissions were analyzed, and emission reduction strategies were implemented. The results show the following: (1) Carbon emissions from production and living spaces increased yearly. Carbon sinks were smaller than emissions, but capacity was stable. (2) Higher-emission cities were concentrated in southwest Heilongjiang, and carbon emission differences between regions gradually increased. (3) Among carbon emission sectors, agricultural and household made up smaller proportions, while animal husbandry, industrial, transportation, and traffic travel contributed most. Carbon emission structures were transformed by adjusting urban development and industrial structure. (4) For most cities, industrial space was the main emission space, but agricultural production and urban–rural living spaces dominated in some cities. (5) GDP, urbanization rate, and area of city paved roads suppressed emissions in cities with decreased carbon emission grades. The industrial structure and coal consumption inhibited emissions in cities with maintaining and increasing carbon emissions grades. [ABSTRACT FROM AUTHOR]

Changes in net ecosystem productivity (NEP) in terrestrial ecosystems in response to climate warming and land cover changes have been of great concern. In this study, we applied the normalized difference vegetation index (NDVI), average temperature, and sunshine hours to drive the C-FIX model and to simulate the regional NEP in China from 2000 to 2019. We also analyzed the spatial patterns and the spatiotemporal variation characteristics of the NEP of terrestrial ecosystems and discussed their main influencing factors. The results showed that (1) the annual average NEP of terrestrial ecosystems in China from 2000 to 2019 was 1.08 PgC, exhibiting a highly significant increasing trend with a rate of change of 0.83 PgC/10 y. The terrestrial ecosystems in China remained as carbon sinks from 2000 to 2019, and the carbon sink capacity increased significantly. The NEP of the terrestrial ecosystem increased by 65% during 2015-2019 compared to 2000-2004 (2) There was spatial differences in the NEP distribution of the terrestrial ecosystems in China from 2000-2019. Taking the line along the Daxinganling-Yin Mountains-Helan Mountains-Transverse Range as the boundary, the NEP was significantly higher in the eastern part than in the western part. Among them, the NEP was positive (carbon sink) in northeastern, central, and southern China, and negative (carbon source) in parts of northwestern China and the Tibet Autonomous Region. The spatial variation of NEP in terrestrial ecosystems increased from 2000 to 2009. The areas with a significant increase accounted for 45.85% and were mainly located in the central and southwestern regions. (3) The simulation results revealed that vegetation changes and CO2 concentration changes both contributed to the increase in the NEP in China, contributing 85.96% and 36.84%, respectively. The vegetation changes were the main factor causing the increase in the NEP. The main contribution of this study is to further quantify the NEP of terrestrial ecosystems in China and identify the influencing factors that caused these changes. [ABSTRACT FROM AUTHOR]

With the implementation of carbon neutrality strategies in China, both carbon emissions reduction and carbon sequestration should be considered. In order to exert the carbon neutrality potential of forest carbon sinks, it is necessary to calculate the cost of them in China. Based on the basic principles of land use opportunity cost and net present value from previous research, this paper constructs a forest carbon sink cost estimation model based on the afforestation cost method. Empirical analysis of the carbon sequestration cost is explored at the city level in China. According to the results, the regional distribution of carbon sink costs varies greatly. On the whole, Southwest China is suitable for afforestation to create carbon sinks since its cost is relatively low. It can obtain carbon benefits from forest carbon sinks projects, while there are higher carbon sink costs in the eastern coastal areas. Furthermore, it dynamically analyzes the impact of the rotation period, timber price, discount rate and afforestation cost on the cost of carbon sinks. The rotation period and afforestation cost have more sensitivity for the forest carbon sink cost. Therefore, it should implement different low-carbon policies in different regions, and encourage forest management to create carbon sinks in areas rich in forest resources. In addition, an inter-regional carbon sink trading mechanism can play the economic value of forest carbon sinks effectively and achieve win-win cooperation between regions. • Analysis of the carbon sink cost is explored at the city level in China. • The regional distribution of carbon costs varies greatly. • Southwest China is suitable for afforestation to make carbon sequestration. • Rotation period, discount rate and afforestation cost have higher sensitivity. [ABSTRACT FROM AUTHOR]

Climate change has emerged as one of the most important environmental issues worldwide. As the world's biggest developing country, China is participating in combating climate change by promoting a low carbon economy within the context of global warming. This paper summarizes the pathways of China's low carbon economy including the aspects of energy, industry, low carbon cities, circular economy and low carbon technology, afforestation and carbon sink, the carbon emission trading market and carbon emission reduction targets. There are many achievements in the implementation of low carbon policies. For example, carbon emission intensity has been reduced drastically along with the optimizing of energy and industry structure and a nationwide carbon trading market for electricity industry has been established. However, some problems remain, such as the weakness of public participation, the ineffectiveness of unified policies for certain regions and the absence of long-term planning for low carbon cities development. Therefore, we propose some policy recommendations for the future low carbon economy development in China. Firstly, comprehensive and long-term planning should be involved in all the low carbon economy pathways. Secondly, to coordinate the relationship between central and local governments and narrow the gap between poor and rich regions, different strategies of carbon emission performance assessment should be applied for different regions. Thirdly, enterprises should cooperate with scientific research institutions to explored low carbon technologies. Finally, relevant institutions should be regulated to realize comprehensive low carbon transition through reasonable and feasible low carbon pathways in China. These policy recommendations will provide new perspectives for China's future low carbon economy development and guide practices for combating climate change. [ABSTRACT FROM AUTHOR]

• We propose a new forest prediction model and use actual deforestation data for optimization and verification. • Use the XGBoost method to reconstruct deforestation intensity data. • Deforestation hotspots in China are mainly concentrated in the southern and southeastern regions. • Our model provides certain reference information for forest disaster prevention and forest management. Forests are important for the global carbon cycle, hydrothermal balance, and climate change. Human activities can exert a significant impact on forest ecosystems, thereby having the potential to alter their physical and chemical properties and thus affecting carbon, water, and heat budgets, and climate change. The historical reconstruction of the disturbance of global forests can help us understand the processes and patterns of human activities and global change. In this paper, we construct a deforestation prediction model using a Spearman correlation coefficient and implement the XGBoost method, using Python 3.6, for the reconstruction of deforestation intensity data from 2000 to 2019. Secondly, the selection of the driver indicators is done by using extreme difference regularization to unify the magnitude, and the potential deforestation area risk index is calculated in the form of equal weights. Finally, the actual deforestation data were used for optimization and validation. The model shows that the deforestation hotspots are mainly concentrated in the southern and southeastern regions of China and that there are large differences in deforestation in different provinces. In the future, the fine spatial and temporal patterns of deforestation in China during the historical period can be quantitatively reconstructed, which can provide some reference information for forest disaster prevention and forest management in China. [ABSTRACT FROM AUTHOR]

Frequency and severity of droughts were projected to increase in many regions. However, their effects of temporal dynamics on the terrestrial carbon cycle remain uncertain, and hence deserve further investigation. In this paper, the droughts that occurred in China during 2001–2010 were identified by using the standardized precipitation index (SPI). Standardized anomaly index (SAI), which has been widely employed in reflecting precipitation, was extended to evaluate the anomalies of net primary productivity (NPP). In addition, influences of the droughts on vegetation were explored by examining the temporal dynamics of SAI–NPP along with area-weighted drought intensity at different time scales (1, 3, 6, 9 and 12 months). Year-to-year variability of NPP with several factors, including droughts, NDVI, radiation and temperature, was analyzed as well. Consequently, the droughts in the years 2001, 2006 and 2009 were well reconstructed. This indicates that SPI could be applied to the monitoring of the droughts in China during the past decade (2001–2010) effectively. Moreover, strongest correlations between droughts and NPP anomalies were found during or after the drought intensities reached their peak values. In addition, some droughts substantially reduced the countrywide NPP, whereas the others did not. These phenomena can be explained by the regional diversities of drought intensity, drought duration, areal extents of the droughts, as well as the cumulative and lag responses of vegetation to the precipitation deficits. Besides the drought conditions, normalized difference vegetation index (NDVI), radiation and temperature also contribute to the interannual variability of NPP. [Copyright &y& Elsevier]

This paper reports the annual carbon (C) balance of China''s forests during 1901–2001 estimated using the Integrated Terrestrial Ecosystem C-budget model (InTEC). Annual carbon source and sink distributions are simulated for the same period using various spatial datasets including land cover and leaf area index (LAI) obtained from remote sensing, soil texture, climate, forest age, and nitrogen deposition. During 1901–1949, China''s forests were a source of 21.0±7.8TgCyr−1 due to disturbances (human activities). Its size increased to 122.3±25.3TgCyr−1 during 1950–1987 due to intensified human activities in the late 1950s, early 1960s, 1970s and early 1980s. The forests became large sinks of 176.7±44.8TgCyr−1 during 1988–2001, owing to large-scale plantation and forest regrowth in previously disturbed areas as well as growth stimulation by nondisturbance factors such as climatic warming, atmospheric CO2 fertilization, and N deposition. From 1901 to 2001, China''s forests were a small carbon source of 3.32PgC, about 32.9±22.3TgCyr−1. The overall C balance in biomass from InTEC generally agrees with previous results derived from forest inventories of China''s forests. InTEC results also include C stock variation in soils and are therefore more comprehensive than previous results. The uncertainty in InTEC results is still large, but it can be reduced if a detailed forest age map becomes available. [Copyright &y& Elsevier]

Coastal wetlands play an increasingly important role in regulating greenhouse gas (GHG) fluxes and thus affecting climate change. However, the overall magnitude, trend, and environmental drivers of GHG fluxes in these wetlands of China remain uncertain. Herein, we synthesized data from 70 publications involving 187 field observations to identify patterns and drivers of GHG fluxes across coastal wetlands in China. Average methane (CH 4), nitrous oxide (N 2 O) fluxes, and carbon dioxide (CO 2) emissions (ecosystem respiration) across coastal wetlands were estimated as 2.20±0.31 mg·m-2·h-1, 16.44±2.96 μg·m-2·h-1, and 388.76±42.28 mg·m-2·h-1, respectively. GHG emissions varied with tidal inundation, where CH 4 and CO 2 emissions during tidal inundation were lower than during ebbing. CH 4 and CO 2 emissions from wetlands decreased linearly with increasing latitude, while N 2 O did not. CH 4 fluxes were positively related to air temperature and aboveground biomass, and CO 2 emissions were positively related to soil organic carbon. N 2 O fluxes were lower with increasing soil pH, and CH 4 and CO 2 emissions were greater with increasing soil moisture. Based on the results of sustained-flux global warming potential and sustained-flux global cooling potential models, our paper indicate that the fluxes of CH 4 and N 2 O in coastal wetlands have a positive feedback to global warming, which is mainly driven by the CH 4 emission. Our synthesis improved understanding of the roles of coastal wetlands in the ecosystem C cycle under global change. We suggest that long-term field observations of GHG fluxes across a wider range of spatiotemporal scales are urgently required to improve the prediction accuracy in GHG fluxes and the assessment of net GHG balance and its contribution to the GWP of coastal wetlands. [ABSTRACT FROM AUTHOR]