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Ecological communities can be stable over multiple generations, or rapidly shift into structurally and functionally different configurations. In kelp forest ecosystems, overgrazing by sea urchins can abruptly shift forests into alternative states that are void of macroalgae and primarily dominated by actively grazing sea urchins. Beginning in 2014, a sea urchin outbreak along the central coast of California resulted in a patchy mosaic of remnant forests interspersed with sea urchin barrens. In this study, we used a 14-year subtidal monitoring dataset of invertebrates, algae, and fishes to explore changes in community structure associated with the loss of forests. We found that the spatial mosaic of barrens and forests resulted in a region-wide shift in community structure. However, the magnitude of kelp forest loss and taxonomic-level consequences were spatially heterogeneous. Taxonomic diversity declined across the region, but there were no declines in richness for any group, suggesting compositional redistribution. Baseline ecological and environmental conditions, and sea urchin behaviour, explained the persistence of forests through multiple stressors. These results indicate that spatial heterogeneity in preexisting ecological and environmental conditions can explain patterns of community change.

The rural transformation driven by regime shift is obvious around the world, and there is still insufficient research exploring related effective analytical frameworks and ideas. Transformation adaptation is widely used in the field of disaster research as a concept of dynamic systems' evolutionary development, emphasizing fundamental changes in the structure or function of systems and promoting equity and justice for communities in social–ecological systems. This paper critically reviews and synthesizes the literature on adaptation to construct an evaluation framework of transformative adaptation of social–ecological systems. This framework is applied to the analysis of the adaptive process, capacity, and outcomes of rural tourism transformation in different cases of Shaanxi Province, China. The results were as follows: (1) The shift of regime state in the process of rural transformation adaptation has diversified, while the tourism regime shift with active adaptation has better adaptive capacity and outcomes; (2) a strong community foundation and benefit-sharing tourism development model can promote adaptation in the rural system; and (3) social relationship networks, farmers' collective interests and discourse power, and rural economic and material conditions are the key factors affecting the adaptation of rural tourism transformation. This study provides practical analytical tools and opportunities for improving adaptation of the rural tourism transformation at the global level. [ABSTRACT FROM AUTHOR]

Deep lakes are critical for freshwater storage, yet they are struggling against major ecological issues from climate change and nutrient pollution. A comprehensive understanding of internal feedback mechanisms is crucial for regulating nutrients in these lakes. A five‐year study was conducted on the diatom community and environment in Lake Fuxian, China's largest deep freshwater lake, which is becoming eutrophic. The results indicate a shift in the diatom community from a stable state dominated by a single species to a rapid seasonal fluctuation, and there is a significant increase in diatom biomass. Specifically, stable stratification and low nutrient concentrations are limiting the growth of diatom biomass and maintaining the dominance of Cyclotella. Nutrients in the hypolimnion were replenished in the epilimnion during the extreme cold of winter, triggering a shift in the diatom community. This shift may imply that future climate change will exacerbate the positive feedback of hypoxia‐nutrient release of algal blooms, potentially triggering a regime shift in the ecosystem of the entire lake. This study underscores the fact that climate change alters the internal feedback mechanisms of deep lakes, reducing ecosystem stability, and provides a scientific basis for further clarification of protection measures for deep lakes. [ABSTRACT FROM AUTHOR]

The Paraguayan Chaco is increasingly known for the extreme rates of forest loss caused by the rapid expansion of cattle ranching and crop farming over the last few decades. Knowledge of its twentieth-century land-use history, however, remains limited. In this article, I address that gap by discussing land-use dynamics since the 1900s in the Pilcomayo River basin, a part of the Chaco that borders Argentina and Bolivia, and hosts a great diversity of actors and land uses. Using the concept of land-use regimes, I show that the area, once characterized by what can be called an Indigenous mixed-use regime, transitioned to a land-use regime dominated by livestock herding by Argentine Criollo settlers after the Chaco War (1932–35), and then again to one of large cattle ranches managed by absentee owners toward the end of the twentieth century. No land-use regime ever completely dominated the area, however, and I use this fact as a starting point to then discuss how using the concept of land regimes can help direct attention to the coexistence of regimes in space and to their relationships in a way that helps refine our understanding of land-use transitions. [ABSTRACT FROM AUTHOR]

Abstract Systems theory and complex science, especially knowledge of social–ecological interdependencies, are urgently needed in planning and decision-making on sustainable urban development due to the intensification of the contradiction between human development and nature conservation. Here, we present an analytical framework, the “social–ecological coupling trajectory”, that integrates the social–ecological coupling, multi-stability, causal feedbacks and sustainable management through understanding the evolution of the urban social–ecological system (SES). This framework is applied to a typical urban SES, i.e., China’s rapidly prosperous Pearl River Delta (PRD). Our results indicate that the SES evolution in the PRD is a phased process, which is accompanied by a continuous decline in major ecosystem services (ESs) and the disproportionate decline of ecological management performance. Further analysis shows that social and economic policies have a decisive role in driving the evolution of SES and the cumulative effect of sustained human interference is directly linked to the disproportionate increase in sustainability challenges. The findings of critical slowing down and evolution patterns of SES in the PRD may provide evidence for the threshold recognition and regime shift prediction in SES. In sum, this study expands the theoretical framework and empirical knowledge of SES evolution and provides a pathway for sustainable development of regions seeking prosperity from the social–ecological coupling perspective.

Early Warning Signals (EWS) have generated much excitement for their potential to anticipate transitions in various systems, ranging from climate change in ecology to disease staging in medicine. EWS hold particular promise for bifurcations, a transition mechanism in which a smooth, gradual change in a control parameter of the system results in a rapid change in system dynamics. The predominant reason to expect EWS is because many bifurcations are preceded by Critical Slowing Down (CSD): if assuming the system is subject to continuous, small, Gaussian noise, the system is slower to recover from perturbations closer to the transition. However, this focus on warning signs generated by stochasticity has overshadowed warning signs which may already be found in deterministic dynamics. This is especially true for higher-dimensional systems, where more complex attractors with intrinsic dynamics such as oscillations not only become possible—they are increasingly more likely. The present study focuses on univariate and multivariate EWS in deterministic dynamics to anticipate complex critical transitions, including the period-doubling cascade to chaos, chaos-chaos transitions, and the extinction of a chaotic attractor. In a four-dimensional continuous-time Lotka–Volterra model, EWS perform well for most bifurcations, even with lower data quality. The present study highlights three reasons why EWS may still work in the absence of CSD: changing attractor morphology (size, shape, and location in phase space), shifting power spectra (amplitude and frequency), and chaotic transitional characteristics (density across attractor). More complex attractors call for different warning detection methods to utilise warning signs already contained within purely deterministic dynamics. [ABSTRACT FROM AUTHOR]

Abstract Many tropical landscapes have experienced the loss of traditional cultivation practices as they have transitioned to other land use systems. The Tanintharyi Region of southern Myanmar is a landscape experiencing a rapid land use regime shift from traditional subsistence farming to permanent cash crop agriculture. Despite previous research in this region on the expansion of large‐scale agribusiness, such as oil palm and rubber plantations, little is known about how the small‐scale shifting cultivation system practiced by the local Karen ethnic people in Tanintharyi has changed over recent decades or the underlying reasons for this transition. Our study explores this transition process and its drivers from a social and land system change perspective in four villages of Bokpyin Township in Tanintharyi. We investigated the drivers of land cover and land use change by collecting information through focus groups and individual interviews with community members who previously practised shifting cultivation. We also quantified the overall change in land cover and land use through remote sensing analysis of Landsat 8 (2020) and declassified KH‐9 satellite imagery (1976). Prior to a period of civil war in the 1980s, cultivators used a traditional ‘slash‐and‐burn’ agricultural system for subsistence use. The present land use system is dominated by permanent betel nut cultivation, which represents the primary income source for farming households. The reported drivers of the transition to cash crop farming are greater income potential and livelihood security, risk of losing fallow land due to the needs for new cultivation areas for in‐migration and new centralized land use policies and administration after the national ceasefire agreement in 2012. The documented change in land use systems has been paired with a concurrent net loss of forest that, given the conflicted governance within the landscape, seems likely to continue without additional land use planning efforts. Our study contributes to an increased understanding of changes in shifting cultivation systems that are being documented globally. Furthermore, our example of combining qualitative interviews with analysis of historical satellite imagery to detect and explain land use regime shifts can serve as a model for future work in different landscapes. Read the free Plain Language Summary for this article on the Journal blog.

This study aimed at testing the hypothesis that free-floating plants may facilitate the growth of submerged plants under hypertrophic conditions and intermediate plant density. The effects of Lemna presence on the growth of two submerged plants (Elodea nuttallii and Ceratophyllum demersum) over a nitrogen gradient were experimentally investigated. This was complemented with analysing the presence of C. demersum and E. nuttallii in Hungary and in Germany in relation to the density of free-floating plants. Results showed a negative exponential pattern between underwater light intensity and Lemna cover. Ceratophyllum and Elodea relative growth rate decreased with increasing nitrogen concentrations and additional low Lemna density stimulated Ceratophyllum and suppressed Elodea. Elodea decreased linearly with Lemna density while Ceratophyllum showed a unimodal response. Total algal biomass (epiphytic and planktonic) was higher in Ceratophyllum than in Elodea treatments and decreased rapidly with increasing Lemna density. The field studies showed a positive relationship between Ceratophyllum and a negative one between Elodea and free-floating plant cover. This study clearly showed that free-floating plants can have either facilitating or inhibiting impact on the growth of submerged plants depending on cover density and macrophyte species. The facilitating effect on Ceratophyllum is most likely due to suppressing epiphytic algal growth. [ABSTRACT FROM AUTHOR]

Strengthening aquatic resilience to prevent adverse shifts is critical for preserving global freshwater biodiversity and advancing Sustainable Development Goals. Nonetheless, understanding the long‐term trends and underlying causes of lake ecosystem resilience at a global scale remains elusive. Here, we employ an innovative framework, integrating satellite‐derived water quality indices with early warning signals and machine learning techniques, to investigate the dynamics of resilience in 1,049 lakes worldwide during 2000–2018. Our results indicate that 46.7% of lakes are experiencing a significant decline in resilience, particularly since the early 2010s, closely associated with higher human population density and anthropogenic eutrophication. In contrast, most lakes situated in alpine regions exhibit an increase in resilience, probably benefiting from climate warming and wetting. Together, this study provides a novel way to monitor lake resilience and predict undesired transitions, and reveals a widespread erosion in the ability of lakes to withstand stressors associated with global change. Plain Language Summary: Based on water quality data from satellite observation and generic indicators of ecological resilience, we found 46.7% of lakes worldwide are experiencing a significant decline in the ability to resist and recover from environmental disturbances. This issue is exacerbated in Northern Europe and Eastern North America, closely related to local human impacts, such as anthropogenic eutrophication. As the regional wealth grows, like in central North America, the negative impact of human activity on aquatic ecosystems may decrease. In contrast, in regions like the Tibetan Plateau and Andes Mountains, lakes are actually showing an increase in resilience, indicating that ecosystems may adapt to or even benefit from climate change. Our analysis' global scope allows us to better understand lake ecosystem dynamics and the socioeconomic drivers associated with them. This knowledge will help manage lakes' response to global change. Key Points: Over the last two decades (2000–2018), nearly half of global lakes experienced resilience lossLake resilience decline is closely linked to human activities in the catchmentsSatellite data effectively track early warning signals of lake resilience loss [ABSTRACT FROM AUTHOR]

Many tropical landscapes have experienced the loss of traditional cultivation practices as they have transitioned to other land use systems.The Tanintharyi Region of southern Myanmar is a landscape experiencing a rapid land use regime shift from traditional subsistence farming to permanent cash crop agriculture. Despite previous research in this region on the expansion of large‐scale agribusiness, such as oil palm and rubber plantations, little is known about how the small‐scale shifting cultivation system practiced by the local Karen ethnic people in Tanintharyi has changed over recent decades or the underlying reasons for this transition.Our study explores this transition process and its drivers from a social and land system change perspective in four villages of Bokpyin Township in Tanintharyi. We investigated the drivers of land cover and land use change by collecting information through focus groups and individual interviews with community members who previously practised shifting cultivation. We also quantified the overall change in land cover and land use through remote sensing analysis of Landsat 8 (2020) and declassified KH‐9 satellite imagery (1976).Prior to a period of civil war in the 1980s, cultivators used a traditional 'slash‐and‐burn' agricultural system for subsistence use. The present land use system is dominated by permanent betel nut cultivation, which represents the primary income source for farming households. The reported drivers of the transition to cash crop farming are greater income potential and livelihood security, risk of losing fallow land due to the needs for new cultivation areas for in‐migration and new centralized land use policies and administration after the national ceasefire agreement in 2012. The documented change in land use systems has been paired with a concurrent net loss of forest that, given the conflicted governance within the landscape, seems likely to continue without additional land use planning efforts.Our study contributes to an increased understanding of changes in shifting cultivation systems that are being documented globally. Furthermore, our example of combining qualitative interviews with analysis of historical satellite imagery to detect and explain land use regime shifts can serve as a model for future work in different landscapes. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Thermal pollution from the cooling system of the nuclear power plants greatly changes the environmental and the ecological conditions of the receiving marine water body, but we know little about their impact on the steady-state transition of marine bacterioplankton communities. In this study, we used highthroughput sequencing based on the 16S rRNA gene to investigate the impact of the thermal pollution on the bacterioplankton communities in a subtropical bay (the Daya Bay). We observed that thermal pollution from the cooling system of the nuclear power plant caused a pronounced thermal gradient ranging from 19.6 °C to 24.12 °C over the whole Daya Bay. A temperature difference of 4.5 °C between the northern and southern parts of the bay led to a regime shift in the bacterioplankton community structure. In the three typical scenarios of regime shifts, the steady-state transition of bacterioplankton community structure in response to temperature increasing was more likely consistent with an abrupt regime shift rather than a smooth regime or a discontinuous regime model. Water temperature was a decisive factor on the regime shift of bacterioplankton community structure. High temperature significantly decreased bacterioplankton diversity and shifted its community compositions. Cyanobium and Synechococcus of Cyanobacteria, NS5 marine group of Bacteroidota, and Vibrio of Gammaproteobacteria were found that favored high temperature environments. Furthermore, the increased water temperature significantly altered the community assembly of bacterioplankton in Daya Bay, with a substantial decrease in the proportion of drift and others, and a marked increase in the proportion of homogeneous selection. In summary, we proposed that seawater temperature increasing induced by the thermal pollution resulted in an abrupt regime shift of bacterioplankton community in winter subtropical bay. Our research might broad our understanding of marine microbial ecology under future conditions of global warming. [ABSTRACT FROM AUTHOR]

The functioning of Mediterranean coastal waters is deeply affected not only by global environmental changes (e.g., global warming, climate change) but also by improvements in sewage treatment as required by the European Water Framework Directive. These changes affect nutrient concentrations and cycling, and primary production. The present paper presents the time series analysis (2005–2020) of stable isotope ratios (hereafter δ13C and δ15N), elemental (C and N), and biochemical compositions (proteins, lipids, carbohydrates) within the 300–500 µm zooplankton size fraction from bimonthly monitoring samples (0–55 m) collected in the Bay of Marseille (NW-Mediterranean Sea). The zooplankton seasonality was mostly related with the dynamic of proxies of phytoplankton biomass and nutrients in the system. In spring, protein content and energy increased and δ15N of zooplankton decreased; in late spring, lipid and carbohydrate content peaked; and in late summer, δ13C increased. At the interannual scale, major changes in the zooplankton biochemical and isotopic composition have occurred since 2009. Lipid content decreased while protein and stable isotope ratios increased. These shifts were concomitant with changes in the nutrient concentrations, nutrient stoichiometry, and particulate organic matter concentrations. The changes in biochemical composition led to an increase of energy content from 2011, but the total quantity of energy available to higher trophic positions remained stable because of a reduction in biomass. The variations of the zooplankton stable isotopes and biochemical compositions can be indicative of changes in individual biochemistry (energy allocation) and/or in the zooplankton community (changes in relative abundance of lipid-rich vs protein-rich species). [ABSTRACT FROM AUTHOR]

The global movement for ecosystem restoration has gained momentum in response to the Bonn Challenge (2010) and the UN Decade on Ecosystem Restoration (UNDER, 2021–2030). While several science‐based guidelines exist to aid in achieving successful restoration outcomes, significant variation remains in the outcomes of restoration projects. Some of this disparity can be attributed to unexpected responses of ecosystem components to planned interventions.Given the complex nature of ecosystems, we propose that concepts from Complex Systems Science (CSS) that are linked to non‐linearity, such as regime shifts, ecological resilience and ecological feedbacks, should be employed to help explain this variation in restoration outcomes from an ecological perspective.Our framework, Explore Before You Restore, illustrates how these concepts impact restoration outcomes by influencing degradation and recovery trajectories. Additionally, we propose incorporating CSS concepts into the typical restoration project cycle through a CSS assessment phase and suggest that the need for such assessment is explicitly included in the guidelines to improve restoration outcomes.To facilitate this inclusion and make it workable by practitioners, we describe indicators and methods available for restoration teams to answer key questions that should make up such CSS assessment. In doing so, we identify key outstanding science and policy tasks that are needed to further operationalize CSS assessment in restoration.Synthesis and applications. By illustrating how key Complex Systems Science (CSS) concepts linked to non‐linear threshold behaviour can impact restoration outcomes through influencing recovery trajectories, our framework Explore Before You Restore demonstrates the need to incorporate Complex Systems thinking in ecosystem restoration. We argue that inclusion of CSS assessment into restoration project cycles, and more broadly, into international restoration guidelines, may significantly improve restoration outcomes. [ABSTRACT FROM AUTHOR]

The intense human pressures in the Anthropocene epoch are causing an alarming decline in marine coastal ecosystems and an unprecedented loss of biodiversity. This situation underscores the urgency of making ecological restoration a global priority to recover degraded ecosystems. Meadows of the endemic Mediterranean seagrass Posidonia oceanica have lost more than half of their original extent in the last century, necessitating immediate conservation and management measures, supported by active restoration interventions. This paper explores new opportunities and provides specific recommendations to enhance restoration as a fundamental strategy for reversing the decline of P. oceanica ecosystems in the Mediterranean Sea. When a return to a historical pristine reference condition may not be feasible in the short term or desirable given current environmental conditions and uncertainty, transplanting the tolerant and fast-growing seagrass species Cymodocea nodosa could facilitate natural recolonization. This would occur through secondary ecological succession, benefiting the sensitive and slow-growing species P. oceanica. Future global and local efforts should primarily focus on proactive management to prevent further alterations by planning appropriate conservation measures in a timely manner to mitigate and reverse global changes. As a secondary step, restoration programs can be implemented with a focus on 'target-oriented' rather than 'reference-oriented' conditions, aiming to establish ecosystems capable of sustaining the future rather than replicating the historical environment. [ABSTRACT FROM AUTHOR]

The resilience and resistance of ecosystems to regime shifts is an emerging area of research in ecological systems. In this article, we investigate the regime shift phenomena in a Rosenzweig–MacArthur predator–prey model when a strong Allee effect is present in the prey population. Apart from strong Allee effect, we incorporate the time scale disparity between the prey and predator populations. We investigate both single-patch and two-patch models with and without dispersal delay. Our findings indicate that the Allee threshold has a negative impact on species persistence and that species extinction occurs through a regime shift due a to non-local bifurcation. This regime shift through a boundary crisis of a limit-cycle oscillator is fatal from the ecological point of view as it leads to sudden extinction. Our investigation also explores how time scale differences affect the tipping point of the regime shift event and we find that it makes species less resilient. Furthermore, we demonstrate that species dispersal in a two-patch model increases resilience and can rescue populations from extinction when a single isolated patch's species become extinct due to a regime shift. Finally, we show that a time delay in dispersal can further enhance resistance to regime shift by large extent. The occurence of a regime shift through a boundary crisis of an oscillatory attractor has not been extensively investigated previously within the context of a two-species predator–prey model. In this study, we offer a comprehensive bifurcation analysis that delves into how species resilience can be enhanced through the effects of dispersal and time lag in dispersal. We quantify species resilience by employing basin stability metric. [ABSTRACT FROM AUTHOR]

Recent changes in oceanic plankton are being reported at unprecedented rates. Most changes are related to environmental factors, and many were identified as driven by climate, either through natural cycles or by anthropogenic effects. However, the separation of both effects is difficult because of the short length of most observational series. Moreover, some changes are related to trends and cycles, while others were perceived as system shifts, often synchronized over large spatial scales. Here, studies on observational series of plankton, with the focus in the North Atlantic, are reviewed. Two main periods of shifts in plankton assemblages were identified: one in the late 1980s and a more recent one at the beginning of the new millennium. While the origin and extent of most shifts varied locally, their synchronization seems to confirm the response of plankton to changes in warming and in large-scale climatic factors. Changes in species abundance and distribution patterns were generally related to hydrographic factors, but also to non-linear effects of warming, the latter particularly affecting species in regions near the limits of their thermal niches. Indeed, most of the changes were attributed to trade-offs between different biological strategies. Taken together, the reviewed case studies indicate a lagged biological response to variations in the local environment driven by large-scale climate forcing. The challenges for interpreting future shifts include considering local changes within a larger geographical area, variations in species life traits, and potential top-down effects of plankton predators. [ABSTRACT FROM AUTHOR]

Using the ERA‐5 reanalysis datasets, NCEP/NCAR sea ice concentration (SIC) and observed winter surface wind speed (WSWS) in northwest China during 1979–2020, this study examined the regime shift of the leading mode of observed WSWS in northwest China and investigated its possible link with the winter Barents–Kara Sea (BKS) SIC. The leading mode of observed WSWS in northwest China showed negative anomalies in southern and northeastern Xinjiang, Gansu, western and northern Shaanxi Provinces, and positive anomalies in northwestern and middle Xinjiang, Qinghai and Ningxia Provinces. The signs of WSWS in the leading mode is generally opposite to their trends during 1979–2020. Leading principal component (PC1) of observed WSWS in northwest China underwent an obvious decreasing regime shift in 2003/04, as well as the winter BKS SIC. There are significant correlations between PC1 and BKS SIC on both interdecadal and interannual timescales. Decadal decrease of BKS SIC is accompanied with a positive phase of Scandinavia pattern (SP) with positive anomalies of 500‐hPa geopotential height over subtropical North Atlantic, Arctic‐Ural region and southern Asia, and negative anomalies over northern North Atlantic‐West Europe and Siberia regions. BKS SIC and SP significantly influenced the Northern China Wind Index (NCWI) at 200 hPa on interdecadal timescale, which was related to the PC1 on both interdecadal and interannual timescales after removing the signal of Arctic Oscillation. Meridional configuration of Siberian cyclonic anomaly and southern Asian anticyclonic anomaly associated with the winter BKS SIC could enhance the intensity of NCWI, which favoured the increase of observed WSWS in northwest China and thereby may contribute to the regime shift in 2003/04 of the leading mode. However, there were still some stations showing decreasing regime shift, which mainly located at the region of steeping terrain. These decreasing changes of WSWS may be related to circumfluence effect of terrain, urbanization and local microclimate, and these reasons still need further detailed study. [ABSTRACT FROM AUTHOR]

The threshold public goods game is one of the best-known models of non-linear public goods dilemmas. Cooperators and defectors typically coexist in this game when the population is assumed to follow the so-called structured deme model. In this article, we develop a dynamical model of a general N-player game in which there is no deme structure: Individuals interact with randomly chosen neighbours and selection occurs between randomly chosen pairs of individuals. We show that in the deterministic limit, the dynamics in this model leads to the same replicator dynamics as in the structured deme model, i.e. coexistence of cooperators and defectors is typical in threshold public goods game even when the population is completely well mixed. We extend the model to study the effect of density dependence and density fluctuation on the dynamics. We show analytically and numerically that decreasing population density increases the equilibrium frequency of cooperators till the fixation of this strategy, but below a critical density cooperators abruptly disappear from the population. Our numerical investigations show that weak density fluctuations enhance cooperation, while strong fluctuations suppress it. [ABSTRACT FROM AUTHOR]

Long transient dynamics in ecological models are characterized by extended periods in one state or regime before an eventual, and often abrupt, transition. One mechanism leading to long transient dynamics is the presence of ghost attractors, states where system dynamics slow down and the system lingers before eventually transitioning to the true attractor. This transition results solely from system dynamics rather than external factors. This paper investigates the dynamics of a classical herbivore-grazer model with the potential for ghost attractors or alternative stable states. We propose an intuitive threshold for first passage time analysis applicable to both bistable and ghost attractor regimes. By formulating the first passage time problem as a backward Kolmogorov equation, we examine how the mean first passage time changes as parameters are varied from the ghost attractor regime to the bistable one, through a saddle-node bifurcation. Our results reveal that the mean and variance of first passage times vary smoothly across the bifurcation threshold, eliminating the deterministic distinction between ghost attractors and bistable regimes. This work suggests that first passage time analysis can be an informative way to classify the length of a long transient. A better understanding of the duration of long transients may contribute to greater ecological understanding and more effective environmental management. [ABSTRACT FROM AUTHOR]

Abstract Deep lakes are critical for freshwater storage, yet they are struggling against major ecological issues from climate change and nutrient pollution. A comprehensive understanding of internal feedback mechanisms is crucial for regulating nutrients in these lakes. A five‐year study was conducted on the diatom community and environment in Lake Fuxian, China's largest deep freshwater lake, which is becoming eutrophic. The results indicate a shift in the diatom community from a stable state dominated by a single species to a rapid seasonal fluctuation, and there is a significant increase in diatom biomass. Specifically, stable stratification and low nutrient concentrations are limiting the growth of diatom biomass and maintaining the dominance of Cyclotella. Nutrients in the hypolimnion were replenished in the epilimnion during the extreme cold of winter, triggering a shift in the diatom community. This shift may imply that future climate change will exacerbate the positive feedback of hypoxia‐nutrient release of algal blooms, potentially triggering a regime shift in the ecosystem of the entire lake. This study underscores the fact that climate change alters the internal feedback mechanisms of deep lakes, reducing ecosystem stability, and provides a scientific basis for further clarification of protection measures for deep lakes.

Monitoring programs that integrate both structural and functional ecosystem components play integral roles in ecosystem management and conservation planning. In the early 1990's, the marine ecosystem of the waters surrounding Newfoundland and Labrador (NL) underwent a regime shift. Several demersal and pelagic fish stocks collapsed simultaneously, and this had significant ecological and socioeconomic consequences. As this regime shift impacted numerous commercial and non-commercial species, assessments based on individual species would be insufficient. We explored a variety of metrics that capture different facets of diversity across multiple species to provide a more robust ecosystem assessment. These were species richness, evenness, community-weighted means of maximum body length and trophic level (i.e., the mean maximum body size or trophic level of the species present in a community), and functional dispersion (FDis). The objectives of this study were 1) to assess trends in community structure of the NL demersal community during the post-collapse period (1995-2018), 2) explore how the various community-level metrics differ or are redundant, and 3) investigate how these metrics are associated with important covariates. Several metrics were redundant and displayed strongly positive, temporal trends being consistent with expectations for a recovery encompassing the entire demersal community. In particular, unweighted community-weighted means of body length and trophic level displayed nearly equal temporal patterns, showing increasing trends throughout the study period which were most prominent in the northern study area and within a limited depth range at the upper shelf break. Corresponding biomass-weighted metrics were also correlated with each other but only showed similar increasing tendencies after the first decade. In contrast, species richness did not show any temporal increase. Evenness and biomass-weighted FDis showed similar temporal patterns, decreasing during the first decade followed by strong increases during subsequent years, patterns that were directly linked to variation in Northern shrimp and Atlantic cod biomass. This study demonstrates how a variety of community metrics can provide insight into different aspects of the post-collapse recovery of the demersal community and help us better understand the complexity of the changes the ecosystem is undergoing. [ABSTRACT FROM AUTHOR]

Using multiple observational and reanalysis data, this paper investigates the impact of the interdecadal shift in summer Arctic Oscillation (AO) on precipitation in East Asia, by removing ENSO influences. The results indicate that the lower-layer activity center of summer AO in Atlantic shifted eastward after the mid-1980s. This regime shift of summer AO has a significant impact on precipitation in East Asia. Before the mid-1980s, the key regions in which precipitation was affected by AO in East Asia were northern East Asia and Northeastern China and adjacent regions. After the mid-1980s, the key regions in which precipitation was affected by AO in East Asia were central Inner Mongolia and Southern China. The mechanism of precipitation changes can be attributed to changes in atmospheric circulation and water vapor transport related to AO changes. After the mid-1980s, the influence of AO on geopotential height over northern East Asia weakened; meanwhile, the impact of AO on geopotential height over China increased. Consistent with the changes in atmospheric circulation, water vapor transport in East Asia also underwent interdecadal changes before and after the mid-1980s. The differences in atmospheric circulation and water vapor transport in East Asia can be traced back to the North Atlantic. Before the mid-1980s, wave activity flux related to summer AO tended to propagate in high latitudes and subtropics; after the mid-1980s, the wave activity flux changed in its subtropical path and propagated eastward from the North Atlantic through the Middle East to China, significantly affecting the summer precipitation in China. [ABSTRACT FROM AUTHOR]

Permafrost is one of the essential carbon pools in the world. Due to limited studies on historical soil moisture changes and the coupling relationship between soil moisture and temperature in permafrost regions, significant uncertainty exists in the carbon loss in permafrost predicted by different models under global warming scenarios. Based on the tree‐ring width chronology of Pinus sylvestris var. mongholica Litv. growing in the southern edge of the Eurasian continuous permafrost zone, we reconstructed the summer (June–September) 0–1 m soil moisture variations from 1705 to 2009, which could explain 45.6% of the variance in the observed soil moisture. Overall, local precipitation and temperature exhibited statistically significant positive feedback (p < 0.001) to soil moisture before the 1950s, indicating that the warm/humid climate pattern was conducive to soil moisture conservation before the Anthropocene Epoch. However, the effect of temperature on soil moisture has shifted suddenly to negative since the 1950s, implying that the positive soil moisture‐temperature relationship during the past three centuries has been disrupted by the unprecedented warming in the Modern Warm Period. Furthermore, we found that the temporal relationship of the soil moisture‐temperature (15‐year sliding correlation) in the study area is negatively regulated by the global mean temperature variations (p < 0.01). The regime shift between soil moisture and temperature might be attributed to the superimposed influence of natural and anthropogenic factors since the 1950s. Although the warming leads to the melting of the permafrost layer, and thus the increase in soil moisture content, the enhanced evapotranspiration caused by warming up results in more water loss and drier soil. This study provides historical evidence of shifted soil moisture‐temperature coupling in the permafrost zone, warning that soil moisture in the permafrost region may further decline under global warming scenarios, thereby affecting vegetation growth and forest carbon sequestration potential. [ABSTRACT FROM AUTHOR]

Coral reefs are model systems for studies of ecological resilience, with communities generally exhibiting multiple stable states and more resilient regions trending towards a single, coral-dominated, regime. We expand the theory of ecological resilience beyond the concepts of distinct stable states to integrate emerging ideas from transient dynamics as long-term intermediate states with no pronounced trend towards equilibria. We show that low coral abundance, together with stochastic larval supply and disturbance, can trap otherwise resilient reefs in a persistent intermediate state whose long-term outcome is difficult to predict. Common metrics, such as the ecosystem slowing down before crossing tipping points and using historical coral cover trends, may become unreliable predictors of future behaviour. Helping reefs out of transient states requires agile management that allows for short-term, targeted interventions after which natural ecological feedbacks can take over. [ABSTRACT FROM AUTHOR]

We propose a real options model with regime shifts to investigate the effect of cutting interest rates on corporate investments when a financial crisis occurs. Cutting interest rates would lower the investment project's hurdle rate. The reduction in hurdle rate is positively related to the magnitude of interest rate cuts and the persistence of the financial crisis. The hurdle rate becomes lower in the financial crisis state because the reduction in interest rate would lower the cost of capital and the opportunity cost of immediate investment. In the numerical analysis of this study, we show that the change in the opportunity cost accounts for most of the change in the hurdle rate. Upon taking into consideration the firm's financing constraints, we find that cutting interest rates accelerates investments for firms with high liquidity. However, for firms with low liquidity, the optimal investment threshold is not affected by the variation in interest rates. Instead, the investments of low‐liquidity firms are affected by the change in the friction of credit supply. [ABSTRACT FROM AUTHOR]

Aquatic ecosystems, especially freshwater ecosystems, are facing increasing anthropogenic disturbances, highlighting the urgency for accurate ecosystem assessment for informed decision-making and effective management. While ecosystem health and integrity assessments have been widely applied, they often focus on ecosystem elements, overlooking their interconnections and dynamic characteristics. Establishing an integrated ecosystem assessment framework is vital to apply a comprehensive perspective in evaluations. In the current paper, a systematic review of aquatic ecosystem assessment methods is done, encompassing health and integrity assessment, network analysis, and stability and regime shift assessment. These approaches consider not only the individual elements but also the complex interconnections and dynamic characteristics within the ecosystem, which have been rarely studied due to limitations in field data availability. A case study of Poyang Lake is further presented for practical demonstration on the specific operation of the combined assessments. The integration of aquatic ecosystem assessment with ecological modeling is strongly advocated because it not only helps overcome the limitations of field data for assessing historical or current conditions, but it also enables prediction of future developments. [ABSTRACT FROM AUTHOR]

Simple Summary: The European hake is under fishing pressure, both in the Atlantic and the Mediterranean waters. Moreover, in certain geographic locations, its size-at-maturity has been reported to decline over time. Understanding biological processes in marine life can assist in species stock evaluation and future management, allowing for the avoidance of population decline and diversity loss. This work focuses on exploring the variation in European hake size-at-maturity in the eastern Ionian Sea (Central Mediterranean) during the last five decades, investigating, at the same time, its relationship with environmental change. European hake, Merluccius merluccius L. 1758, is a highly valuable demersal fish species exploited in both the east Atlantic and the Mediterranean Sea. Changes in the size-at-maturity of this species have been reported in various geographic areas. Size-at-maturity is a key parameter in fishery management. Our main goal was to study the trend of the size-at-maturity of European hake in the eastern Ionian Sea (Central Mediterranean) over the last five decades. Utilizing a multi-decadal series of data for various environmental variables, we employed multivariate analyses and non-additive modeling in an attempt to identify shifts in the climatic environment of the eastern Ionian Sea and whether the maturation of the hake population could be affected by these changes. The analyses used suggest a plausible environmental regime shift in the study area in the late 1990s/early 2000s. The decrease in size-at-maturity that was detected in the last two decades may, thus, be associated with environmental changes. However, as many fish stocks already experience fishery-induced evolution, further investigation is necessary to determine whether this environmental effect is an additional stressor on a possibly already fishery-impacted population. The outcomes of this study highlight the importance of investigating the relationship between fish reproductive traits and altered environmental conditions, as the latter are generally ignored during assessments, affecting the robustness of fishery management. [ABSTRACT FROM AUTHOR]

Microplastics can be ingested by a wide range of aquatic animals. Extensive studies have demonstrated that microplastic ingestion—albeit often not lethal—can affect a range of species life‐history traits. However, it remains unclear how the sublethal effects of microplastics on individual levels scale up to influence ecosystem‐level dynamics through cascading trophic interactions.Here we employ a well‐studied, empirically fed three‐species trophic chain model, which was parameterized to mimic a common type of aquatic ecosystems to examine how microplastic ingestion by fish on an intermediate trophic level can produce cascading effects on the species at both upper and lower trophic levels.We show that gradually increasing microplastics in the ingested substances of planktivorous fish may cause population structure effects such as skewed size distributions (i.e. reduced average body length vs. increased maximal body size), and induce abrupt declines in fish biomass and reproduction.Our model analysis demonstrates that these abrupt changes correspond to an ecosystem‐level tipping point, crossing which difficult‐to‐reverse ecosystem degradation can happen. Importantly, microplastic pollution may interact with other anthropogenic stressors to reduce safe operating space of aquatic ecosystems.Our work contributes to better understanding complex effects of microplastic pollution and anticipating tipping points of aquatic ecosystems in a changing world. It also calls attention to an emerging threat that novel microplastic contaminants may lead to unexpected and abrupt degradation of aquatic ecosystems, and invites systematic studies on the ecosystem‐level consequences of microplastic exposure. [ABSTRACT FROM AUTHOR]

Anthropogenic warming is altering species abundance, distribution, physiology, and more. How changes observed at the species level alter emergent community properties is an active and urgent area of research. Trait‐based ecology and regime shift theory provide complementary ways to understand climate change impacts on communities, but these two bodies of work are only rarely integrated. Lack of integration handicaps our ability to understand community responses to warming, at a time when such understanding is critical. Therefore, we advocate for merging trait‐based ecology with regime shift theory. We propose a general set of principles to guide this merger and apply these principles to research on marine communities in the rapidly warming North Atlantic. In our example, combining trait distribution and regime shift analyses at the community level yields greater insight than either alone. Looking forward, we identify a clear need for expanding quantitative approaches to collecting and merging trait‐based and resilience metrics in order to advance our understanding of climate‐driven community change. [ABSTRACT FROM AUTHOR]

Understanding the ecosystem history of reservoirs threatened by water-quality degradation is of utmost relevance for public health and ecosystem services. In this study, we examined the responses of diatom composition and diversity (richness and evenness) to long-term climate change and anthropogenic activities since 1960 CE in a deep subtropical reservoir (Qiandao Lake) in southeastern China. Besides, we detected structure changes in diatom community with F statistic test, and disclosed early warning signals of critical transition with a composite index comprising three resilience metrics, variance, skewness, and lag-1 autocorrelation (AR1). Our results showed that annual mean water level (MWL), annual mean temperature (Tann), ratio of total nitrogen to total phosphorus (N:P), and fish catch (FC) significantly affected diatom compositional change. Diatom richness was regulated primarily by MWL and Tann, whereas evenness was affected by MWL and FC. In general, human activities (most notably, water-level regulation) exerted the greatest influence on diatom composition and diversity changes since the impoundment. In maintaining the service function of Qiandao Lake, assessing the ecological effects of water-level regulation is important. F statistic test indicated striking structure changes of diatom assemblage in 1980 and 2002 CE. According to the composite resilience index, the early warning signals appeared a decade before the regime shift in 2002 CE. This study demonstrated that resource competition was probably the critical mechanism triggering regime shifts in the diatom community during the past 60 years. For management practice, our work suggested the necessity of monitoring water temperature and nutrient stoichiometry regularly, and implementing more stringent measures for constraining nutrient loads are necessary in preventing catastrophic shifts in Qiandao Lake ecosystem. [ABSTRACT FROM AUTHOR]

Abstract Strengthening aquatic resilience to prevent adverse shifts is critical for preserving global freshwater biodiversity and advancing Sustainable Development Goals. Nonetheless, understanding the long‐term trends and underlying causes of lake ecosystem resilience at a global scale remains elusive. Here, we employ an innovative framework, integrating satellite‐derived water quality indices with early warning signals and machine learning techniques, to investigate the dynamics of resilience in 1,049 lakes worldwide during 2000–2018. Our results indicate that 46.7% of lakes are experiencing a significant decline in resilience, particularly since the early 2010s, closely associated with higher human population density and anthropogenic eutrophication. In contrast, most lakes situated in alpine regions exhibit an increase in resilience, probably benefiting from climate warming and wetting. Together, this study provides a novel way to monitor lake resilience and predict undesired transitions, and reveals a widespread erosion in the ability of lakes to withstand stressors associated with global change.

The effects of climate-induced, long-term changes on mesozooplankton biomasses were studied based on monitoring data collected since 1966 in the northern Baltic Sea. We found that the biomasses of marine and brackish mesozooplankton had decreased significantly from 1966 to 2019, and a remarkable biomass and functional biodiversity loss took place in the mesozooplankton community. Our results put emphasis on the impact of two climate-driven regime shifts for the region's mesozooplankton community. The regime shifts took place in 1975 and 1976 and in 1989 and 1990, and they were the most important factor behind the abrupt biomass changes for marine mesozooplankton and total and marine Copepoda. Only the latter regime shift influenced the biomasses of brackish Copepoda, marine Cladocera, and total Rotifera. The decreasing length of the ice-cover period drove the decrease of the biomass of limnic Limnocalanus macrurus (Copepoda), while the winter North Atlantic Oscillation was behind biomass changes in the total and the brackish Cladocera. These findings may have important implications for planktivorous fish, such as Baltic herring, particularly in terms of their impact on commercial fishing.

The rural transformation driven by regime shift is obvious around the world, and there is still insufficient research exploring related effective analytical frameworks and ideas. Transformation adaptation is widely used in the field of disaster research as a concept of dynamic systems’ evolutionary development, emphasizing fundamental changes in the structure or function of systems and promoting equity and justice for communities in social–ecological systems. This paper critically reviews and synthesizes the literature on adaptation to construct an evaluation framework of transformative adaptation of social–ecological systems. This framework is applied to the analysis of the adaptive process, capacity, and outcomes of rural tourism transformation in different cases of Shaanxi Province, China. The results were as follows: (1) The shift of regime state in the process of rural transformation adaptation has diversified, while the tourism regime shift with active adaptation has better adaptive capacity and outcomes; (2) a strong community foundation and benefit-sharing tourism development model can promote adaptation in the rural system; and (3) social relationship networks, farmers’ collective interests and discourse power, and rural economic and material conditions are the key factors affecting the adaptation of rural tourism transformation. This study provides practical analytical tools and opportunities for improving adaptation of the rural tourism transformation at the global level.

Aim: The widely observed positive response of productivity to biodiversity, known as the biodiversity‐productivity relationship (BPR), underpins nature‐based solutions for mitigating and adapting to global changes. Little is known of the role of such emergent processes in the restoration of damaged ecosystems. Here, we test for evidence of a BPR in degraded freshwater lakes, and its role in underpinning or undermining lake recovery from eutrophic states. Location: Lower Yangtze and Huaihe river basins, China, East Asia. Taxa: Freshwater phytoplankton; also macrophytes, fish, zooplankton and zoobenthos. Methods: A systematic review of biodiversity studies was conducted to enumerate freshwater biodiversity change during eutrophication, encompassing 572 samples from 155 lakes in East China. Empirical samples were then taken of 93 phytoplankton communities from 38 lakes in ecologically degraded states of eutrophication. Samples were analysed for niche overlap in relation to biodiversity and productivity, and metrics of network structure indicative of community stability. Results: Reviewed publications on eutrophication in East China lakes revealed losses in biodiversity of macrophytes, fishes, zooplankton and zoobenthos but not phytoplankton. Empirically sampled eutrophic lakes maintained high phytoplankton biodiversity through niche differentiation, and phytoplankton biodiversity correlated positively with biomass, in line with the expectations of BPR. Conclusions: The positive effect of biodiversity on phytoplankton productivity in eutrophic lakes acts in opposition to the negative impacts on productivity induced by eutrophication‐management strategies of nutrient suppression. In degraded systems, the BPR contributes to sustaining productivity of lake phytoplankton communities, impeding recovery from a eutrophic state. This is a case of the BPR playing an undesirable role at the ecosystem level. Lake recovery programmes need to anticipate that the control of phytoplankton biomass will depend on reducing nutrients to a level sufficient to degrade the internal structure of the phytoplankton community. [ABSTRACT FROM AUTHOR]

To understand the effect of regime shift in Caohai Lake in Yunnan-Guizhou Plateau, SW China from submerged macrophyte dominance to phytoplankton dominance on the specification and distribution of phosphorus and on ecological and environmental states, changes in phosphorus specification in the sediments and water were studied. The form, composition, and distribution of phosphorus in sediment were sampled in July 2020 (before regime shift) and July 2021 (after regime shift) were analyzed. Results reveal that phosphorus content in sediment was lower than that those of Erhai Lake and Dianchi Lake, Yunnan, SW China, on the same plateau, and was lower than those of Taihu Lake, Chaohu Lake, and Poyang Lake in the middle-lower Changjiang (Yangtze) River Plain. Organic phosphorus (Or-P) was the main form (up to 60%), followed by inactive phosphorus (Ina-P), and the active phosphorus (Act-P), the least, which is opposite to those of Taihu Lake and Poyang Lake in the middle-lower Changjiang River Plain in the eastern China. Or-P content was high, indicating a high potential risk of phosphorous release. After the regime shift, the total phosphorus in sediment decreased from 0.87±0.13 to 0.70±0.13 g/kg. The proportion of Or-P and Act-P decreased from 68.23% to 65.32% and from 5.35% to 4.69%, respectively. In contrast, the proportion of Ina-P increased from 26.42% to 29.99%. The Moran's I index revealed that the heterogeneity of the spatial distributions of the total phosphorus (S-TP) and Act-P in the sediments before regime shift was significant (P<0.1). However, the heterogeneity of the spatial distributions of S-TP and the various forms of phosphorus after regime shift was not significant (P>0.05). The regime shift aggravated the eutrophication of the lake, the trophic level index (TLI) increased from 48.42 to 54.49 (P<0.01), and the previously mesotrophic lake became a mildly eutrophic lake. The results of this study revealed the impact of regime shift in the lake from submerged macrophyte dominance to phytoplankton dominance on the composition and spatial distribution of phosphorus in sediments and provided a basis for the restoration of eutrophicated and aquatic ecosystem degraded lakes. [ABSTRACT FROM AUTHOR]

Eutrophic lakes often exhibit two alternative types: macrophytes-dominated (MD) and phytoplankton-dominated (PD). However, the nature of bacterial community types that whether the transition from the MD to the PD types occurs in a gradual or abrupt manner remains hotly debated. Further, the theoretical recognition that stability regulates the transition of bacterial community types remains qualitative. To address these issues, we divided the transition of bacterial communities along a trophic gradient into 12 successional stages, ranging from the MD to the PD types. Results showed that 12 states were clustered into three distinct regimes: MD type, intermediate transitional type and PD type. Bacterial communities were not different between consecutive stages, suggesting that the transition of alternative types occurs in a continuous gradient. At the same time, the stability of bacterial communities was significantly lower in the intermediate type than in the MD or PD types, highlighting that the collapse and re-establishment of community stability regulate the transition. Further, our results showed that the high complexity of taxon interactions and strong stochastic processes disrupt the stability. Ultimately, this study enables deeper insights into understanding the alternative types of microbial communities in the view of community stability. [ABSTRACT FROM AUTHOR]

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The effects of grazing on wildlife have received considerable attention. Depending on factors such as its intensity and duration, grazing can impact higher-level species along the food chain through competition for available resources with wild herbivores. However, relatively few studies have investigated whether there are tipping points at which grazing intensity begins to seriously impact wildlife. In particular, studies that assess the impact of overgrazing on food chains that include carnivores remain scarce. We developed a time dynamic, age-structured model for the wild ungulates-Amur tiger trophic chain, including cattle grazing as a disturbance. We explored 1) the impact of cattle grazing intensity on the long-term behaviour of the wildlife population; 2) the effect of demographic parameters on wildlife population viability; and 3) the temporal dynamic impact of periods of heavy grazing on the population trajectory. Our results showed that increasing cattle density reaches a tipping point, triggering a rapid and significant shift in wildlife population size. Below the tipping point, wildlife can coexist with grazing livestock; when cattle density exceeds the tipping point, wild ungulate and tiger populations move towards extinction. In the case of heavy grazing, the dynamics of the wild ungulate population was more affected by its intensity, and the dynamics of the Amur tiger population was more affected by its duration. Our model and results suggest that theoretically wildlife conservation and cattle production can coexist but that serious regime shifts in wildlife populations may occur if grazing intensity exceeds a tipping point. These findings provide new insights useful for developing policies related to balancing livestock and wildlife conservation.

Monitoring programs that integrate both structural and functional ecosystem components play integral roles in ecosystem management and conservation planning. In the early 1990’s, the marine ecosystem of the waters surrounding Newfoundland and Labrador (NL) underwent a regime shift. Several demersal and pelagic fish stocks collapsed simultaneously, and this had significant ecological and socioeconomic consequences. As this regime shift impacted numerous commercial and non-commercial species, assessments based on individual species would be insufficient. We explored a variety of metrics that capture different facets of diversity across multiple species to provide a more robust ecosystem assessment. These were species richness, evenness, community-weighted means of maximum body length and trophic level (i.e., the mean maximum body size or trophic level of the species present in a community), and functional dispersion (FDis). The objectives of this study were 1) to assess trends in community structure of the NL demersal community during the post-collapse period (1995-2018), 2) explore how the various community-level metrics differ or are redundant, and 3) investigate how these metrics are associated with important covariates. Several metrics were redundant and displayed strongly positive, temporal trends being consistent with expectations for a recovery encompassing the entire demersal community. In particular, unweighted community-weighted means of body length and trophic level displayed nearly equal temporal patterns, showing increasing trends throughout the study period which were most prominent in the northern study area and within a limited depth range at the upper shelf break. Corresponding biomass-weighted metrics were also correlated with each other but only showed similar increasing tendencies after the first decade. In contrast, species richness did not show any temporal increase. Evenness and biomass-weighted FDis showed similar temporal patterns, decreasing during the first decade followed by strong increases during subsequent years, patterns that were directly linked to variation in Northern shrimp and Atlantic cod biomass. This study demonstrates how a variety of community metrics can provide insight into different aspects of the post-collapse recovery of the demersal community and help us better understand the complexity of the changes the ecosystem is undergoing.

The intense human pressures in the Anthropocene epoch are causing an alarming decline in marine coastal ecosystems and an unprecedented loss of biodiversity. This situation underscores the urgency of making ecological restoration a global priority to recover degraded ecosystems. Meadows of the endemic Mediterranean seagrass Posidonia oceanica have lost more than half of their original extent in the last century, necessitating immediate conservation and management measures, supported by active restoration interventions. This paper explores new opportunities and provides specific recommendations to enhance restoration as a fundamental strategy for reversing the decline of P. oceanica ecosystems in the Mediterranean Sea. When a return to a historical pristine reference condition may not be feasible in the short term or desirable given current environmental conditions and uncertainty, transplanting the tolerant and fast-growing seagrass species Cymodocea nodosa could facilitate natural recolonization. This would occur through secondary ecological succession, benefiting the sensitive and slow-growing species P. oceanica. Future global and local efforts should primarily focus on proactive management to prevent further alterations by planning appropriate conservation measures in a timely manner to mitigate and reverse global changes. As a secondary step, restoration programs can be implemented with a focus on ‘target-oriented’ rather than ‘reference-oriented’ conditions, aiming to establish ecosystems capable of sustaining the future rather than replicating the historical environment.

Abstract Backgrounds Grazing prohibition and reduced grazing intensity, as two important “vegetation close‐to‐nature recovery” methods, have been suggested as economical and effective technologies for enhancing forage production. However, numerous studies have found that the yield of forage could be increased by removing or reducing grazing in a short time in some steady stage of alpine Kobresia meadows, but not in others. To reveal the mechanism behind this phenomenon, we proposed a series of experiments. Methods We monitored the plant and soil characteristics in the key steady stages of Kobresia meadows under reduced and prohibited grazing conditions in the same geographic and climatic environments in the northeastern Qinghai‐Tibet Plateau for 6 years. We estimated the relationships between the plant community and soil nutrients and obtained the following results. Results All measured variables were positively correlated with each other. The plant community structure had higher path coefficients to aboveground biomass, soil organic matter, total nitrogen, and nitrate nitrogen than to other factors. The plant community structure played an important role in response to grazing intensity. Different plant functional groups (PFGs) had different responses to grazing intensity, which led to plant community re‐establishment or re‐organization under different grazing intensities. Poaceae and Kobresia were more sensitive to grazing intensity than other PFGs, and the ratio of Kobresia biomass (including Kobresia humilis and Kobresia pygmaea) to the total biomass of Poaceae and Kobresia could be used as an indicator of regime shifts within plant communities. With Kobresia pygmaea as the dominant species, the prohibition of grazing was not an efficient approach to increase the yield in the steady stages because this treatment needed more time to recover aboveground biomass. If Poaceae is the dominant PFG, grazing should only be prohibited for 3 years in the steady stages because the aboveground biomass will decrease if grazing is prohibited for more than 3 years. Conclusions Therefore, the different steady stages of alpine meadows require different recovery methods to increase recovery efficiency and speed.

Microxanox is an R package to simulate a three functional group ecosystem (cyanobacteria, phototrophic sulfur bacteria, and sulfate-reducing bacteria) with four chemical substrates (phosphorus, oxygen, reduced sulfur, and oxidized sulfur) using a set of ordinary differential equations. Simulations can be run individually or over a parameter range. The model can be implemented with different numbers of species per functional group. The package is constructed in such a way that the results contain the input parameter used, so that a saved results can be loaded again and the simulation be repeated. Furthermore, the package framework and code should serve as a useful starting point for making simulation models of other types of ecosystems.

The present study assessed the impact of regime shifts on the ecosystems that support fisheries in the coastal area of Kyoto Prefecture, the Sea of Japan. Ecopath models were constructed during cold (1985) and warm (2013) regime periods, when the fishery structures were different. Both models evaluated by pre-balance diagnostics were reliably constructed. Multiple ecosystem indicator values were compared between the two periods to assess changes in the ecosystem structure and the impact of fisheries on the ecosystem. The major change in catches in the coastal area of Kyoto Prefecture between 1985 and 2013 was that the Japanese sardine drastically declined and Spanish mackerel increased. The primary production requirements of fisheries (%PPR) were higher in 1985, reflecting the greater impact of sardine. The mean trophic level of catch and system omnivory index suggested that stability of trophic network increased after the sharp decline in sardine biomass. The %PPR, the loss of secondary production due to fisheries exploitation and probability analysis of fishery sustainability suggested that the fishery structure in 2013, which was dominated by set nets, contributed to a more sustainable fishery than the structure in 1985, when fishery was dominated by purse seines and set nets. [ABSTRACT FROM AUTHOR]

While populations of other migratory salmonids suffer in the Anthropocene, pink salmon (Oncorhynchus gorbusca Salmonidae) are thriving, and their distribution is expanding both within their natural range and in the Atlantic and Arctic following introduction of the species to the White Sea in the 1950s. Pink salmon are now rapidly spreading in Europe and even across the ocean to North America. Large numbers of pink salmon breed in Norwegian rivers and small numbers of individuals have been captured throughout the North Atlantic since 2017. Although little is known about the biology and ecology of the pink salmon in its novel distribution, the impacts of the species' introduction are potentially highly significant for native species and watershed productivity. Contrasts between pink salmon in the native and extended ranges will be key to navigating management strategies for Atlantic nations where the pink salmon is entrenching itself among the fish fauna, posing potential threats to native fish communities. One key conclusion of this paper is that the species' heritable traits are rapidly selected and drive local adaptation and evolution. Within the Atlantic region, this may facilitate further establishment and spread. The invasion of pink salmon in the Atlantic basin is ultimately a massive ecological experiment and one of the first examples of a major faunal change in the North Atlantic Ocean that is already undergoing rapid changes due to other anthropogenic stressors. New research is urgently needed to understand the role and potential future impacts of pink salmon in Atlantic ecosystems. [ABSTRACT FROM AUTHOR]

Small shallow ponds are widespread but understudied water bodies in agricultural landscapes. Agricultural run‐off (ARO) transports pesticides and nutrients into adjacent aquatic ecosystems where they occur dissolved in the water column or are bound to sediments. Consequently, aquatic communities are affected by ARO via different exposure pathways. We hypothesize that sediment‐bound ARO mainly affects submerged rooted macrophytes, while phytoplankton and periphyton are more prone to ARO in water. These primary producers compete for resources resulting in a regime shift between alternative stable states of macrophyte or phytoplankton dominance. We hypothesize that warming increases nutrient release from sediments and thereby facilitates the occurrence of phytoplankton dominance.Using a full‐factorial microcosm design, we exposed aquatic primary producers to either sediment or water application of a mixture of common pesticides (terbuthylazine, pirimicarb, tebuconazole and copper) and nitrate at two concentrations and two temperatures (22°C and 26°C) for 4 weeks. Initial and final concentrations of pesticides and nitrate, final biomass of macrophytes, periphyton and phytoplankton, pesticide accumulation in macrophytes and changes in carbon, nitrogen and phosphorus content and selected exoenzyme activities in the sediment were measured.We found lower final macrophyte biomass for both ARO treatments compared to controls, indicating a prevalence of negative effects by herbicides and competition for light with other phototrophs. In contrast, phytoplankton and periphyton biomass increased, but only when exposed to ARO via the water column, indicating a prevalence of positive effects by nutrient supply. Microbial carbon and nutrient cycling in sediments was not affected by ARO. Higher temperature mitigated ARO‐related effects on macrophytes under sediment exposure.Synthesis and application. ARO poses a strong risk of submerged macrophyte loss and establishment of turbid conditions with phytoplankton dominance in aquatic ecosystems. In conclusion, exposure pathways as well as indirect and interacting effects of multiple stressors need to be considered when designing appropriate mitigation measures. Under climate change, we suggest to prioritize local measures as buffer strips a reduced use of pesticides and fertilizers, and sediment removal as appropriate measures to protect these vulnerable but widespread aquatic systems, which are highly relevant for biodiversity in agricultural landscapes. [ABSTRACT FROM AUTHOR]

Positive feedback is key to producing alternative stable states and largely determines ecological resilience in response to external perturbations. Understanding the positive feedback mechanisms in macrophyte‐dominated lakes is crucial for resilience‐based management and restoration. Based on the field investigation of submerged macrophyte communities in 35 lakes in China, we found that morphological complexity (MC) and morphological plasticity (MP) are correlated with the stoichiometric homeostasis of phosphorus (HP) and are related to ecosystem structure, functioning, and stability. We also found that the positive feedback strength of lakes dominated by macrophytes is biomass‐ and diversity‐dependent. Eutrophication can decrease the community biomass by decreasing community MC, MP, and HP and the species diversity through low‐light availability, ultimately decreasing the positive feedback strength and resilience of clear water states. We argue that functional traits and species diversity should be considered to build more resilient ecosystems in future changing environment scenarios. [ABSTRACT FROM AUTHOR]

Aquatic ecosystem degradation is a considerable challenge of global interest. Although substantial efforts have been accomplished to restore phytoplankton-dominated shallow lakes to a clear state with high coverage of submerged macrophytes, the phenomenon, driving mechanism, and threshold range of such nonlinear regime shifts remain unclear. Here, we constructed an aquatic ecological model based on PCLake, simulated and predicted the aquatic ecological changes before and after treatments of Xinglong Lake, a subtropical artificial shallow lake that had been completed ecological restoration in Chengdu, China. The model included the future prediction of TN, TP, Chl-a, and aquatic vegetation biomass, as well as the threshold of regime shifts using bifurcation analysis. We also quantified the impact of some common management measures (point and non-point source pollution control, water level regulation) on the stability of the lake's aquatic ecosystem. The results showed that the thresholds of Xinglong Lake from a clear state to a turbid state were 1.405 mg/m2/day and vice versa 0.68 mg/m2/day, indicating its initial turbidity and transitional state after treatment. After treatment, phosphorus loads still exceeded the threshold for a clear-water state, while the non-point source pollution of Xinglong Lake accounted for more than 80%. To prevent the aquatic ecosystem from collapsing in the future, it is necessary to combine upstream water quality improvement, runoff and air pollution control to reduce total pollution by 60%. Reasonable water level regulation, such as adjusting the water level downwards by 0.5 m in spring, is beneficial in maintaining the health and stability of aquatic ecosystems. The present study can be used to evaluate the effectiveness of the management measures of Xinglong Lake as well as to provide scientific support for the management of shallow lakes.