为应对全球气候变化，实现《巴黎协定》温控目标，我国提出了力争2030年前实现碳达峰、2060年前实现碳中和，碳汇提升和碳减排协同增效成为助力碳中和实现的关键手段。滨海区域湿地碳储功能巨大，但在气候变化和高强度人类活动影响下，碳汇功能严重受损，成为制约区域生态保护与高质量发展的瓶颈。碳代谢是反映碳在系统中流转的关键过程，然而当前研究多集中于增汇固碳或经济减排单一方面效应却往往忽视了生态-经济-社会网络耦合对碳中和的综合影响。因此，统筹协调湿地生态-经济-社会复合系统的碳代谢过程，是实现滨海区域增汇减排的重要保障，“湿地增汇-经济减排-社会发展”协同增效成为助推区域碳中和实现的关键。

       本研究面向湿地碳中和需求，以“碳中和能力评估-碳代谢网络耦合-节点路径识别-网络优化调控”为研究主线，综合运用生态网络分析、社会网络分析、情景模拟等方法，以生态保护与经济发展矛盾突出的黄河三角洲高效生态经济区为例，阐释了1995—2020年（以5年为间隔，增加了2018年禁止围填海实施年）湿地生态-经济-社会碳代谢网络耦合机制，明确了湿地增汇-经济减排-社会发展协同优化的安全操作空间。本研究为促进滨海区域增汇减排和丰富湿地可持续发展研究提供了理论指导。对缓解我国湿地履约压力，助推我国碳中和目标实现，具有重要的战略意义。本研究得到的主要结果如下：

     （1）自然碳汇波动，人为源碳排放总量上升，湿地碳中和能力下降

       1995—2020年间黄河三角洲高效生态经济区生态系统固碳量在19.9~23.5 MtCO₂ yr^-1间波动，呈先下降、再上升、再缓慢下降的趋势。区域人为源碳排放总量呈现先增长后降低的趋势，从1995年的30.7 MtCO₂ yr^-1到2020年的82.6 MtCO₂ yr^-1，25年间整体增加了1.7倍。人均碳排放量（3.4~11.0 tCO₂）高于中国大部分城市。区域碳排放量大于固碳量，净固碳量呈现先快速减少、后缓慢增加的变化趋势。研究期间碳中和能力均小于100%，未达到碳中和。碳中和能力从76.5%下降到最低为18.2%，后恢复到24.1%。湿地碳中和能力由31.7%下降至6.8%，滨海湿地碳中和能力由28.6%下降至5.2%，湿地碳中和能力尤其是滨海湿地碳中和能力亟待提升。湿地碳中和能力降低的主要原因是滩涂沼泽湿地的开发利用造成湿地固碳量下降，与此同时经济活动碳排放量不断增长，导致了碳中和能力下降。

     （2）湿地生态-经济碳代谢网络流量增加，网络稳健性相对较低

       湿地生态-经济网络直接流量的增加主要与大气、互花米草、鱼类、软体动物、原盐、渔业、工业、建筑业、交通业、污水处理相关，其中流量超过0.1 Mt的路径数量超过50条。综合流量变化趋势与直接流量趋势类似，在1995—2015年呈上升趋势，增长了99.7%；2015—2020年呈下降趋势，减少了29.4%。间接流量与直接流量的比值约为12.2。节点间的生态关系相对稳定，均为掠夺/控制＞共生＞竞争，稳定关系占比为88.0%（包含对角线上节点自身的共生关系）。网络共生指数（NMI）均值为1.2，正效用大于负效用，呈现先降低后波动上升的分布趋势。整体网络效率较高，冗余较低，稳健性相对较低。基于碳中和与碳代谢网络评估的关键节点和路径，可确定I类、II类和Ⅲ类关键节点分别有12、1和5个，I类、II类和Ⅲ类关键路径分别有11、9和34条。

     （3）社会网络密度低、中心性高，湿地生态-经济-社会网络耦合协调度降低

       社会网络内部连接稀疏，网络密度相对较低、中心性较高。社会网络关注度较高的生态因子依次为土壤、大气、近海水域、径流和盐地碱蓬等，社会网络关注度较高的经济因子依次为种植业、渔业、林业和交通业等。利益相关群体的参与方式有信息共享（79%）、生产-消费（14%）和行政管理（7%）三种，通过QAP（Quadratic Assignment Procedure）回归分析可知行政管理的效率较低。就黄河三角洲高效生态经济区区域耦合协调度而言，耦合协调度逐渐降低，排序为滨海湿地＞内陆湿地＞人工湿地＞非湿地，同时景观类型及其多样性和社会经济发展是影响网络耦合协调度的重要因素。

     （4）生态系统服务受损，识别了耦合网络9个失稳节点和39条失稳路径

       湿地和非湿地碳综合服务分别为0.53和0.33，生境质量分别为0.60和0.04。1995—2018年碳综合服务和生境质量总体呈下降趋势，2020年较2018年略有回升。滨海湿地分布区有较高的碳综合服务和生境质量，但逐渐被低值区取代，高值功能区呈现离散分布，因此区域生态系统服务有待提升。芦苇和盐地碱蓬两个生态受损节点为网络潜在修复的失稳节点，本研究提出了基于自然的碳中和解决方案（Nature-based Carbon Netural Solutions，NbCNS）理念的滨海湿地水文连通-生物连通联合修复工程范式，包括自然恢复、潮流恢复、潮流恢复-微地形修复、生物格栅修复。能源、工业和废弃物处理三个经济失衡节点为网络潜在修复的失稳节点，失衡节点流量调控主要通过降低单位GDP能源CO₂排放量、提高单位面积GDP及控制城市建设规模。直接相关企业、间接相关企业、居民、游客作为社会短板节点为网络潜在修复的失稳节点，节点关注率调控主要通过控制经济过快增长及提升生态系统服务。

     （5）湿地增汇-经济减排-社会发展协同优化的安全操作空间

       基于“红绿蓝”三线整合的固碳增汇格局显示，滩涂和沼泽湿地面积相对呈增长趋势；互花米草沼泽、养殖池以及盐田面积呈下降趋势。可持续发展情景（sustainable development scenario，SD情景）在2058年实现了碳中和目标，为最优发展情景。基准情景（business as usual scenario，BAU情景）通过湿地增汇和经济减排，净固碳量呈现先升高、后降低的变化趋势，在2060年净固碳量为-32.5 Mt，未能实现碳中和目标。低保护发展情景（low protect and restoration scenario，LP情景）在2046年净固碳量达到极小值（-140.9 Mt），呈现先降低、后增加的变化趋势，2060年净固碳量仍高达-76.7 Mt，未能实现碳中和。SD和BAU两个情景相较2020年，受到湿地生态保护及区域减排的影响，直接流量和综合流量均有所降低，而LP情景却相对升高。基于碳中和达标年和最优情景调整植物、动物、环境相关节点和路径，提出了基于湿地增汇的整体保护、系统修复、协同治理的湿地生态-经济网络安全操作空间；调整能源、产业、废弃物处理相关节点和路径，提出了基于经济减排的能源优化、产业调整、提升封存的湿地生态-经济网络安全操作空间；调整长板节点、短板节点、新板节点，提出了基于社会发展的实施政策、提升关注、优化参与的湿地生态-经济-社会网络安全操作空间；形成了黄河三角洲高效生态经济区应对碳中和目标的湿地生态-经济-社会网络调控模式。

       In order to cope with global climate change and achieve the goals of the Paris Agreement, China has proposed to strive to achieve carbon peak by 2030 and carbon neutrality by 2060. Increasing carbon sink and reducing carbon emission are the two most important means to achieve carbon neutrality. The carbon storage of coastal wetlands is huge, however, under the influence of climate change and high-intensity anthropogenic activities, carbon sink is seriously damaged, which becomes a bottleneck restricting regional ecological protection and high-quality development. Carbon metabolism is the key process reflecting the carbon circulation in the system.The current researches on carbon neutrality mostly focused on a single aspect of carbon sink or economic emission reduction, however, often ignored the coupling wetland ecological-economic-social network on carbon neutrality. Therefore, the overall coordination of the carbon metabolism process of the wetland ecological-economic-social complex system is an important guarantee for the realization of sink increase and emission reduction in the coastal region. The synergistic effect of wetland sink increase, economic emission reduction and social development has become the key to promote the realization of regional carbon neutrality.

       Aiming at carbon neutrality, several contents were conducted out around a main line: assessing carbon neutrality , coupling carbon metabolism network, identifying nodes and paths, and network optimization regulation, by Ecological Network Analysis, Social Network Analysis, scenario simulation etc in the Yellow River Delta High-efficient Eco-Economic Zone (YRDHEZ) during 1995-2020 (5 year intervals, with the addition in 2018, of the reclamation ban implementation). The coupling wetland ecological-economic-social network mechanism was elucidated for carbon metabolism, and the safe operating space of synergistic optimization was explicated for wetland sink increase, economic emission reduction and social coordinated development. It is of great theoretical guidance to promote the improvement of carbon sink and regional carbon emission reduction, as well as enrich the research on wetland sustainable development. It is of great strategic significance to alleviate the pressure of fulfilling the convention on wetlands and promote the realization of carbon neutrality for China. The main results were as follows:

     (1) The total natural carbon sink fluctuated, the total anthropogenic carbon emission increased, and the wetland carbon neutral capacity decreased.

       The total carbon sink fluctuated in the range of 19.9-23.5 MtCO₂ yr^-1, showing a trend of first decreased then increase, and then slowly decreased in the YRDHEZ during 1995-2020. CO₂ emissions showed a trend of first increased and then decreased in the range of 30.7-82.6 MtCO₂ yr^-1, with an overall increase of 1.7 times in 25 years. Carbon emission per capita (3.4-11.0 tCO₂) was higher than that of most Chinese cities. Regional carbon emission was greater than carbon sink, thus the net carbon sink showed a trend of first rapid decrease and then slow increase. During the study period, the carbon neutral capacity was less than 100%, which did not reach carbon neutrality. Carbon neutral capacity decreased from 76.5% to 18.2%, then recovered to 24.1%. The wetland carbon neutral capacity decreased from 31.7% to 6.8%, and the coastal wetland carbon neutral capacity decreased from 28.6% to 5.2%, thus, the wetland carbon neutral capacity, especially the coastal wetland, needed to be improved urgently. The decrease of wetland carbon neutral capacity was mainly due to the development and utilization of tidal flats and marshes, resulting in the carbon sink decrease, as well as the economic activities resulting in the carbon emission increase.

     (2) The increased flows and the low robustness for the wetland ecological-economic carbon metabolism network.

      The increase of the direct flow was mainly related to the atmosphere, Sparsparia alternaria, fish, mollush, crude salt, fishery, industry, construction, transportation, and sewage treatment for the wetland ecological-economic network. More than 50 of paths exceeded 0.1Mt. The integral flows increased by 99.7% during 1995-2015, and decreased by 29.4% during 2015-2020, similar to direct flow. The ratio of indirect to direct flows was around 12.2. The ecological relationships among nodes were relatively stable, and the proportion of stable ecological relations was around 88.0% (including the mutualism of nodes themselves on the diagonal). The exploitation/control relationships accounted for the largest proportion, followed by mutualism relationships, and the competition relationships accounted for the smallest proportion. The mean value of network mutualism index (NMI) was 1.2, showing a distribution trend of decreasing first and then increasing, and the positive utility was greater than the negative. The overall network efficiency was high, the redundancy was low, while the robustness was relatively low. Assessment on both carbon neutrality and metabolism network, the number of Class I, Class II, class III were 12, 1, and 5 for the key nodes; while 11, 9, and 34 for the key paths respectively.

     (3) The low density and high centrality of the social network, as well as the decrease of coupling coordination degree for wetland ecological-economic-social network.

      The social network was a non-cohesive network with low density and high centrality. The ecological factors with strong social network attention were soil, atmosphere, offshore, runoff and Suaeda salsa, while the economic factors were cultivation, fishery, forestry and transportation. The main relationships between different stakeholder groups were concentrated in information sharing (79%), production-consumption (14%), and administrative management (7%) relationships, of which the administrative management relationships have a lower correlation with productivity in the Quadratic Assignment Procedure (QAP) test. In terms of the coupling coordination degree of YRDHEZ, it was gradually decreased as follows, coastal wetlands, inland wetlands, constructed wetlands, and non-wetlands. Landscape types, diversity as well as economic development were important factors affecting the coupling coordination degree.

     (4) Ecosystem services were damaged, as well as 9 unstable nodes and 39 unstable paths of the coupling network were identified.

       The integrated carbon service was 0.53 and 0.33 for wetlands and non-wetlands. The habitat quality index was 0.60 and 0.04 respectively. Integrated carbon service and habitat quality showed a downward trend during 1995-2018, and a slight rebound in 2020. The coastal wetlands had higher integrated carbon services and habitat quality, however, they was gradually replaced by lower values, which needed to be improved. The two damaged nodes, Phragmites communis and S. salsa, were the ecological unstable nodes for potential restoration. A joint restoration engineering paradigm of coastal wetland restoration with hydrological-biological connectivity was put forward including tidal recovery, freshwater input, freshwater input and micro-topography, as well as biological grid. The three economic unbalanced nodes, energy, industry and waste disposal, were unstable nodes for potential restoration. These flows should be controlled mainly through reducing CO₂ emissions per unit GDP, increasing GDP per unit area and controlling the scale of urban construction. The four social unstable nodes, directly-related enterprises, indirectly-related enterprises, residents and tourists were the weak nodes for potential restoration. Node attention rates were regulated mainly by controlling the excessive economic growth and improving the ecosystem service.

     (5) The safe operating space for synergistic optimization for wetland sink increase, economic emission reduction and social coordinated development

       Based on the "Red-Green-Blue" three-line integration patterns of carbon sink, the area of tidal flats and swamps showed an increasing trend, while S. alterniflora marshes, culture ponds and salt pan showed a decreasing trend. In sustainable development (SD) scenario, it achieved carbon neutrality by 2058, as the optimal development scenario. In business as usual (BAU) scenario, through wetland sink increase and economic emission reduction, the net carbon sink showed a trend of first increase and then decrease. In 2060, the net carbon sink was -32.5 MtCO₂ yr^-1, failing to achieve the carbon neutrality. In low protect and restoration (LP) scenario, the net carbon sinks reached the minimum (-140.9 MtCO₂ yr^-1) in 2046, showing a trend of first decrease and then increase. In 2060, the net carbon sink was -76.7 MtCO₂ yr^-1, failing to achieve carbon neutrality as well. Affected by wetland ecological protection and regional emission reduction, direct and integral flow decreased in SD and BAU scenarios, while increased in LP scenarios relatively. Based on the carbon neutrality target year and the optimal scenario, the safe operation space of overall protection, systematic restoration and collaborative governance were proposed, by adjusting the plants, animals, environments and relevant paths for the wetland ecological-economic network; the safe operation space of energy optimization, industrial adjustment, and CCUS improvement were proposed, by adjusting the energy, industry, waste disposal and relevant paths for the wetland ecological-economic network; and the safe operation space of implementing policies, raising attention, and optimizing participation were proposed, by adjusting the strong, weak, new nodes and relevant paths for the wetland ecological-economic-social network. A wetland ecological-economic-social network regulation model was formed for carbon neutrality in YRDHEZ, in order to contribute to the carbon neutrality and sustainable development in China's coastal areas.