Social-ecological systems (SES) are complex, dynamic systems with interdependencies between their ecological components and social actors. Studying the transient (e.g., nonlinear) dynamics of interlinked SES can provide valuable insights into achieving the UN Sustainable Development Goals for a more desirable future. 
　　However, identifying critical transitions in real-world SES remains a major challenge. A significant knowledge gap exists in index framework for characterizing dynamic behaviors within SES changes. This issue is also compounded by the scarcity of long-term datasets spanning entire transition periods, which together limits our comprehension of the Anthropocene landscape changes. 
　　Recently, an international research team led by Dr. LIN Qi and Prof. ZHANG Ke from the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences made some progresses by advancing an evolutionary framework that utilizes a dynamic metric based on Rate of Change (RoC) derived from multidecadal socioeconomic and geobiophysical (lake sediment) records. These researchers from China, France, Netherlands, Sweden, Italy, United Kingdom, and South Africa worked together, and applied the co-evolutionary framework to Lake Taihu watershed from China’s Yangtze River Delta region. 
　　The study was published in Proceedings of the National Academy of Sciences of the United States of America. 
　　By integrating sedimentary ancient DNA (sedaDNA) metabarcoding, multi-proxy paleoenvironmental analyses, and socioeconomic data, the researchers elucidated the temporal dynamics of regional SES over several centuries. Starting in the 1950s, the SES underwent a shift towards an interconnected and ecologically unsustainable state, driven by a series of deleterious positive feedbacks. These process exacerbated water eutrophication, soil erosion, air pollution, and ecosystem resilience loss under human stressors. More interestingly, the study revealed a decoupling of socioeconomic development from eco-environmental degradation since the early 2000s, signifying a potentially more sustainable reconfiguration of the regional SES. 
　　“Thanks to the wide-ranging environmental laws and policies, conservation and ecological engineering projects, and institutional innovations, the recent decoupling signal discloses a sustainable development pattern not observed over the past millennium in this iconic region”, said Dr. LIN Qi, first author of the study. The signal highlights the crucial role of adaptive management and policy intervention in fostering positive transformations. 
　　This case study also provides insights into the resilience and adaptability of regional SES facing similar ecological and environmental stressors. It demonstrates potential strategies for transformative action as outlined under the UN Sustainable Development Goals. “Adopting the co-evolutionary framework to address the complexities of SES dynamics, just like in Lake Taihu case, can offer a blueprint for where and how transformative steps can be taken to achieve a good Anthropocene”, said Prof. ZHANG Ke, corresponding author of the study.
　　 
　　IMAGE: Dynamic changes of intertwined SES from a historical evolutionary perspective. 
　　CREDIT by ZHANG KE  
　　Website linkage: https://www.pnas.org/doi/10.1073/pnas.2321303121 
　　Contact Information 
　　Ke Zhang at the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences
　　Email: kzhang@niglas.ac.cn

　　Iron (Fe), a crucial component of the Earth's biogeochemical cycle, has a significant impact on global ecology and carbon cycling. Understanding the effect of Fe on the carbon cycle is essential for comprehending biogeochemical processes of carbon and climate change. 
　　The traditional view suggests that dissimilatory iron reduction (DIR) can drive the release of organic carbon (OC) as carbon dioxide (CO2) by mediating electron transfer between organic compounds and microbes. However, it is important to note that this view may be subjective and requires further investigation to confirm its validity. 
　　A recent study led by Prof. XING Peng from the Nanjing Institute of Geography and Limnology, Chinese Academy Sciences, found that dissolved inorganic carbon (DIC) was crucial for carbon sequestration. DIC affected inorganic-carbon redistribution via iron abiotic-phase transformation. The study was published in Global Change Biology on 18 March. 
　　The study discovered that the abiotic and biotic processes at the organic carbon-microbe-mineral interface facilitated CO2 sequestration and reduced its emission by half. The redistribution of inorganic carbon within or among the atmosphere, lithosphere, and hydrosphere is critical for the fate of elevated CO2. 
　　Additionally, researchers found that high porosity promoted electron transport and DIR bacteria activity, which can increase the rate of iron reduction. The presence of iron, calcium, and organic carbon in the environment can create a porous sediment structure that facilitates rapid DIR. This environment is conducive to the formation and growth of iron minerals that contain carbonate (ICFe), which can sequester inorganic carbon. The researchers also found that a minimum DIR threshold of 6.65 μmol g-1 dw day-1 was necessary for ICFe formation. 
　　 The 'OC-microbe-mineral reactions' involved both biotic and abiotic reactions, which improve our understanding of the processes that mediate CO2 sequestration in anoxic subsurface environments such as soils, wetlands, and sediments. Furthermore, modelling studies suggested that microbial iron reduction was more thermodynamically favorable under elevated CO2, which could mitigate the negative impact of elevated CO2 on global warming. 
　　 "The information can help assess the sequestration of DIC resulting from both abiotic and biotic processes working together. It is also useful for monitoring and managing CO2 sequestration, as well as developing appropriate engineering strategies to remediate CO2 sequestration in these environments," said Prof. XING Peng, corresponding author of the study.
　　http://doi.org/10.1111/gcb.17239
　　 
　　 Contact TAN Lei Nanjing Institute of Geography and Limnology E-mail: ltan@niglas.ac.cn

　　Dissolved organic matter (DOM) is the main form and active component of natural organic matter in lakes. DOM acts as a large reservoir of carbon. Furthermore, the processing of different organic compounds in DOM by aquatic organisms can be impacted by changes in temperature, which represents a potential climate feedback loop as the rate of carbon dioxide released into the atmosphere may be slowed or accelerated under higher temperatures. 
　　Previous study simplified this complex issue in computational models by classifying different types of DOM into a few categories based on its response (or lack of response) to changing environmental conditions. 
　　However, researchers led by Prof. WANG Jianjun from the Nanjing Institute of Geography and Limnology, Chinese Academy Sciences, recently developed an indicator that can be used to quantify the response of individual DOM constituents to changing environmental conditions. The indicator could allow for a more realistic and nuanced representation of DOM environmental responses, as opposed to a simple classification. 
　　The study was published in Nature Communications on 17 January. 
　　The researchers conducted field experiments on mountainsides of three distinct climate zones in Eurasian continent to assess how temperature affects the composition of DOM. The mountainsides ranged from a subtropical wet environment on the southeastern edge of the Tibetan Plateau, through a temperate arid environment in the northern Tibetan Plateau, to a subarctic environment in Northern Europe. 
　　They discovered that individual DOM constituents showed a wide range of temperature responses. The thermal responses of DOM were further found to increase towards warmer conditions such as at low elevations. 
　　Also, this warming effect could be strengthened by nutrient enrichment. The warming effect was strengthened by eutrophication, with increased sensitivity of up to 22% for each additional 1 mg L-1 of nitrogen loading. This suggests that the temperature responses of organic matter can be affected by other global change drivers, especially nutrient enrichment in complex ways. 
　　Moreover, the research indicated that the thermal responses of individual organic molecules were associated with their chemical properties. Additionally, despite the differences in climate zones, the thermal responses of these molecules showed a remarkable level of consistency. Organic carbon molecules with lower thermodynamic favorability for microbial decomposition exhibited a higher positive response to temperature. Each organic carbon molecule exhibited similar thermal response across the three highly divergent mountain environments. The findings revealed that the responses of molecules to temperature were transferable and generalizable across regional and continental scales. 
　　This is the very first application of molecular-level methods to assess the responses of organic matter to global change. The role of DOM in climate feedbacks and the earth system can be properly understood by this work, which will allow us to better prepare for an uncertain future.
　　https://doi.org/10.1038/s41467-024-44813-2
　　Contact TAN Lei Nanjing Institute of Geography and Limnology E-mail: ltan@niglas.ac.cn