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Abstract Resilience, measured by the distribution of passage times between alternate states, indicates persistence of a state in stochastic dynamic systems such as blooms of cyanobacteria in lakes. We used high‐frequency datasets to compare the resilience of low and high states of phycocyanin, a pigment indicator of cyanobacteria, in Lake Mendota, Wisconsin, USA, for three growing seasons that ranged sevenfold in external phosphorus (P) load. Each year we observed 139–265 passage times across the unstable threshold that separated the low‐ from high‐phycocyanin states. Each sample of passage times is highly skewed with low median, larger mean, much larger SD, and wide tails extending to long lifetimes of a state. About 25% of events, whether low or high phycocyanin, lasted a day or more. Among these 3 years of contrasting external P load, there were no discernible differences in the resilience of either ecosystem state. We attribute this lack of contrast to the sustained recycling of P from sediments and the high stochasticity of phycocyanin in this lake.

Abstract Phytoplankton blooms often follow nutrient enrichment. Differences among lakes in light‐absorbing dissolved organic carbon (DOC) may shift bloom thresholds to higher nutrient loads and thereby increase resilience of lakes to enrichment. To explore this idea, we measured resilience to experimental enrichment of two lakes with contrasting DOC concentrations. We compared bloom thresholds in both lakes using a model of phytoplankton response to DOC and nutrients, a dynamic time series indicator of resilience, and two empirical measures of stochastic resilience, mean exit time and median survival time. For the dynamic indicator and ecosystem model the lake with higher DOC was more resilient to enrichment. However, the distributions overlapped for stochastic indicators of resilience of the two lakes. These analyses show that DOC interacts with mixing depth and zooplankton biomass to affect resilience. Strong contrasts in DOC and many observations are needed to discern effects of DOC on resilience to enrichment.

The Programme on Ecosystem Change and Society (PECS) was established in 2011, and is now one of the major international social-ecological systems (SES) research networks. During this time, SES research has undergone a phase of rapid growth and has grown into an influential branch of sustainability science. In this Perspective, we argue that SES research has also deepened over the past decade, and helped to shed light on key dimensions of SES dynamics (e.g. system feedbacks, aspects of system design, goals and paradigms) that can lead to tangible action for solving the major sustainability challenges of our time. We suggest four ways in which the growth of place-based SES research, fostered by networks such as PECS, has contributed to these developments, namely by: 1) shedding light on transformational change, 2) revealing the social dynamics shaping SES, 3) bringing together diverse types of knowledge, and 4) encouraging reflexive researchers.

Biosphere Futures (https://biospherefutures.net/) is a new online database to collect and discover scenario studies from across the world, with a specific focus on scenarios that explicitly incorporate interdependencies between humans and their supporting ecosystems. It provides access to a globally diverse collection of case studies that includes most ecosystems and regions, enabling exploration of the multifaceted ways in which the future might unfold. Together, the case studies illuminate the diversity and plurality of people’s expectations and aspirations for the future. The objective of Biosphere Futures is to promote the use of scenarios for sustainable development of the biosphere and to foster a community of practice around social-ecological scenarios. We do so by facilitating the assessment, synthesis, and comparative analysis of scenario case studies, pointing to relevant resources, and by helping practitioners and researchers to disseminate and showcase their own work. This article begins by outlining the rationale behind the creation of the database, followed by an introduction to its functionality and the criteria employed for selecting case studies. Subsequently, we present a synthesis of the first 100 case studies included in the scenarios database, highlighting emerging patterns and identifying potential avenues for further research. Finally, given that broader utilization and contributions to the database will enhance the achievement of Biosphere Futures’ objectives, we invite the creators of social-ecological scenarios to contribute additional case studies. By expanding the database’s breadth and depth, we can collectively foster a more nuanced understanding of the possible trajectories of our biosphere and enable better decision making for sustainable development.

Abstract Concentrations of phycocyanin, a pigment of Cyanobacteria, were measured at 1‐min intervals during the ice‐free seasons of 2008–2018 by automated sensors suspended from a buoy at a central station in Lake Mendota, Wisconsin, U.S.A. In each year, stochastic‐dynamic models fitted to time series of log‐transformed phycocyanin concentration revealed two alternative stable states and random factors that were much larger than the difference between the alternate stable states. Transitions between low and high states were abrupt and apparently driven by stochasticity. Variation in annual magnitudes of the alternate states and the stochastic factors were not correlated with annual phosphorus input to the lake. At daily time scales, however, phycocyanin concentration was correlated with phosphorus input, precipitation, and wind velocity for time lags of 1–15 d. Multiple years of high‐frequency data were needed to discern these patterns in the noise‐dominated dynamics of Cyanobacteria.

Abstract Ecosystems are changing in complex and unpredictable ways, and analysis of these changes is facilitated by coordinated, long‐term research. Meeting diverse societal needs requires an understanding of what populations and communities will be dominant in 20, 50, and 100 yr. This paper is a product of a synthesis effort of the U.S. National Science Foundation funded Long‐Term Ecological Research (LTER) network addressing the LTER core research area of populations and communities. This analysis revealed that each LTER site had at least one compelling story about what their site would look like in 50 or 100 yr. As the stories were prepared, themes emerged, and the stories were grouped into papers along five themes for this special issue: state change, connectivity, resilience, time lags, and cascading effects. This paper addresses the resilience theme and includes stories from the Baltimore (urban), Hubbard Brook (northern hardwood forest), Andrews (temperate rain forest), Moorea (coral reef), Cedar Creek (grassland), and North Temperate Lakes (lakes) sites. The concept of resilience (the capacity of a system to maintain structure and processes in the face of disturbance) is an old topic that has seen a resurgence of interest as the nature and extent of global environmental change have intensified. The stories we present here show the power of long‐term manipulation experiments (Cedar Creek), the value of long‐term monitoring of forests in both natural (Andrews, Hubbard Brook) and urban settings (Baltimore), and insights that can be gained from modeling and/or experimental approaches paired with long‐term observations (North Temperate Lakes, Moorea). Three main conclusions emerge from the analysis: (1) Resilience research has matured over the past 40 yr of the LTER program; (2) there are many examples of high resilience among the ecosystems in the LTER network; (3) there are also many warning signs of declining resilience of the ecosystems we study. These stories highlight the need for long‐term studies to address this complex topic and show how the diversity of sites within the LTER network facilitates the emergence of overarching concepts about this important driver of ecosystem structure, function, services, and futures.

Abstract We conducted a 33‐yr series of whole‐lake experiments to measure ecosystem responses to food web structure and nutrient load, compare aquatic and terrestrial carbon flows to consumers, and evaluate indicators of ecosystem resilience. These manipulations showed that chlorophyll responded to nutrient loading and to grazing controlled by a trophic cascade. In this article, we synthesized experimental results using a new analysis of heretofore unrecognized variation in water color, measured as light absorbance at 440 nm. Long‐term data revealed fluctuations in precipitation that drive water color variation. We compared effects of nutrient loading, zooplankton biomass, zooplankton body size, and water color on chlorophyll. Water color was an important factor in the chlorophyll response. This driver of the chlorophyll response to manipulation was not resolved until decades of data were available. A long‐term context enriched insights from ecosystem experiments and exemplified the complementarity of experimental and long‐term approaches in limnology.

Abstract Climate change has generated growing interest in extreme events, and extremes are known to have important consequences for ecosystems. Theoretical mechanisms generating frequent extremes apply to both environmental and biological processes, yet past studies of ecological extremes have focused primarily on the abiotic environment. The rarity or commonness of extremes in biological time series is unknown. We evaluated the statistical tendency to produce extreme events in 595 biological, chemical, physical, and meteorological time series taken from 11 lakes. We found that extreme events were much more likely to occur for biological variables than for other categories. Additional analysis revealed that the tendency to produce extremes was driven primarily by within‐year dynamics, suggesting that processes occurring at short time scales underlie the high frequency of extremes in biological variables. These results should lead us to expect surprises in long‐term observations of biological populations.

Abstract Successful management of natural resources requires local action that adapts to larger‐scale environmental changes in order to maintain populations within the safe operating space (SOS) of acceptable conditions. Here, we identify the boundaries of the SOS for a managed freshwater fishery in the first empirical test of the SOS concept applied to management of harvested resources. Walleye (Sander vitreus) are popular sport fish with declining populations in many North American lakes, and understanding the causes of and responding to these changes is a high priority for fisheries management. We evaluated the role of changing water clarity and temperature in the decline of a high‐profile walleye population in Mille Lacs, Minnesota, USA, and estimated safe harvest under changing conditions from 1987 to 2017. Thermal–optical habitat area (TOHA)—the proportion of lake area in which the optimal thermal and optical conditions for walleye overlap—was estimated using a thermodynamic simulation model of daily water temperatures and light conditions. We then used a SOS model to analyze how walleye carrying capacity and safe harvest relate to walleye thermal–optical habitat. Thermal–optical habitat area varied annually and declined over time due to increased water clarity, and maximum safe harvest estimated by the SOS model varied by nearly an order of magnitude. Maximum safe harvest levels of walleye declined with declining TOHA. Walleye harvest exceeded safe harvest estimated by the SOS model in 16 out of the 30 yr of our dataset, and walleye abundance declined following 14 of those years, suggesting that walleye harvest should be managed to accommodate changing habitat conditions. By quantifying harvest trade‐offs associated with loss of walleye habitat, this study provides a framework for managing walleye in the context of ecosystem change.

There are many calls to use the COVID 19 crisis as an opportunity for transforming to a future trajectory that is more equitable and environmentally sustainable. What is lacking is a cohesive framework for bringing these calls together. We propose that such transitions could be informed by lessons from three decades of scholarship on abrupt and surprising change in systems of humans and nature. Over time, many social-ecological systems exhibit cycles of change consisting of sequential patterns of growth, development, crisis, and reorganization. A critical phase in the cycle is the brief period after crisis when novelty and innovation can change the future trajectory. Without being prepared for this window of opportunity, deep, systemic change may be unachievable. We propose a three-step process to identify the major drivers of the global system that need to be changed: (1) identifying what society values; (2) identifying the determinants of these valued variables; and (3) identifying the underlying drivers of the determinants and how they need to be changed. A tentative list of five such drivers are identified and discussed: (i) the economic system, (ii) homogenization, (iii) human population growth, size, and densities, (iv) consumption patterns, human ethics, and behavior, and (v) governance. They are linked to seven questions relating to how we might proceed in addressing the drivers. If response to the crisis merely reinforces the existing system, its incompatibility with the natural world and its propensity to increase inequity and conflict will likely increase fragility and lead to another version of the present calamity. If it is a deliberately transformed system that emerges its future will depend on the reorganization process, and the way the system is guided into the future. What is needed is a deliberate, fundamental cultivation of emergence to enable transformation toward better futures in order to avoid an inevitable deepening of a system that ultimately is worse for all.