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Understanding the transient dynamics of interlinked social-ecological systems (SES) is imperative for assessing sustainability in the Anthropocene. However, how to identify critical transitions in real-world SES remains a formidable challenge. In this study, we present an evolutionary framework to characterize these dynamics over an extended historical timeline. Our approach leverages multidecadal rates of change in socioeconomic data, paleoenvironmental, and cutting-edge sedimentary ancient DNA records from China's Yangtze River Delta, one of the most densely populated and intensively modified landscapes on Earth. Our analysis reveals two significant social-ecological transitions characterized by contrasting interactions and feedback spanning several centuries. Initially, the regional SES exhibited a loosely connected and ecologically sustainable regime. Nevertheless, starting in the 1950s, an increasingly interconnected regime emerged, ultimately resulting in the crossing of tipping points and an unprecedented acceleration in soil erosion, water eutrophication, and ecosystem degradation. Remarkably, the second transition occurring around the 2000s, featured a notable decoupling of socioeconomic development from ecoenvironmental degradation. This decoupling phenomenon signifies a more desirable reconfiguration of the regional SES, furnishing essential insights not only for the Yangtze River Basin but also for regions worldwide grappling with similar sustainability challenges. Our extensive multidecadal empirical investigation underscores the value of coevolutionary approaches in understanding and addressing social-ecological system dynamics.

Endorheic lakes, lacking river outflows, are highly sensitive to environmental changes and human interventions. Central Asia (CA) has over 6000 lakes that have experienced substantial water level variability in the past century, yet causes of recent changes in many lakes remain unexplored. Modelling hydrological processes for CA lakes poses challenges in separating climatic change impacts from human management impacts due to limited data and long-term variability in hydrological regimes. This study developed a spatially lumped empirical model to investigate the effects of climate change and human water abstraction, using Shortandy Lake in Burabay National Nature Park (BNNP) as a case study. Modelling results show a significant water volume decline from 231.7x106m3 in 1986 to 172.5x106m3 in 2016, primarily driven by anthropogenic water abstraction, accounting for 92% of the total volume deficit. The highest rates of water abstraction (greater than 25% of annual outflow) occurred from 1989 to 1993, coinciding with the driest period. Since 2013, the water volume has increased due to increased precipitation and, more importantly, reduced water abstraction. Despite limited observational data with which to calibrate the model, it performs well. Our analysis underscores the challenges in modelling lakes in data-sparse regions such as CA, and highlights the importance and benefits of developing lake water balance models for the region.

Nature helps us fight climate change by removing carbon from the atmosphere and storing it underground—a process called carbon sequestration. Some freshwater ecosystems, like lakes, are great at carbon sequestration. Surprisingly, small organisms play a big role here! When tiny algae and bacteria in the water photosynthesize, they take carbon dioxide from the atmosphere and convert it to organic carbon (the carbon that forms all living organisms). The organic carbon moves through the ecosystem as it is eaten by other organisms or as it sinks to the bottom as either poop or the remains of dead organisms. When organic carbon reaches the bottom, it can remain buried for a long time. Aquatic plants and material from land that washes into freshwater can also sink and end up as sequestered carbon. It seems like freshwater ecosystems sequester carbon more efficiently than other environments, but scientists still have more work to do. Because of the huge diversity of water bodies across the world, scientists need to know which are the real carbon sequestration champions.

Inland waters are highways of carbon and nutrient flows between the land and ocean. Aquatic environments integrate multiple sources and processes over space and time that influence ecosystem functionality. The complexity of these systems and their multiple interactions with the surrounding environment are conceptualised, but often lack empirical scrutiny that allows further understanding of how inland waters mobilise, transport, and utilise carbon and nutrients. This is particularly evident in tropical waters. Here, we apply advanced geochemical analyses of dissolved organic matter (DOM) composition in conjunction with algal pigment biomarkers, to determine the seasonal variability of organic matter production, processing and export for a tropical, floodpulse wetland, Tasik Chini (Malaysia). We identify two phases in the hydrological cycle: Phase 1 signifying a transition from the wet season with high suspended sediment and dissolved organic carbon concentrations. DOM is composed of humic substances, building blocks and lower molecular weight compounds. Towards the end this phase then are periods of increased water clarity and algal productivity. This is followed by Phase 2, which has a greater contribution of autochthonous DOM, composed of proteinaceous material, concomitant with lower dissolved nutrient concentrations, increased mixotrophic algae and emergent vegetation. Based on this framework, we highlight the role of such tropical wetland lakes as hydrological “bottlenecks,” through a lentic/lotic switch that shifts aquatic transport of carbon and nutrients from lateral river continuum supply to flood pulses. We highlight the need to consider inherent biases of spatial and temporal scaling when examining freshwater ecosystems along the land-ocean aquatic continuum.