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Meaning of stability
... These abrupt changes may impair any attempts to preserve or restore ecosystems, to manage the exploitation of their resources or to preserve the services that they provide [4,5]. Lewontin [6] introduced the concept of alternate stable (AS) states resting on the existence of a set of multiple stable (MS) states in the dynamics of ecological systems, and hence the possibility for ecological variables to "jump" from one basin of attraction to another. Alternate stable states can therefore be considered as a subset of multiple stable (MS) states; they regroup the MS states for which shifts between stable states are possible in a given system. ...
... In parallel, Schelling [19] developed the notion of "tipping points", a concept introduced earlier by Grodzins [20] to express the idea that a variable can increase progressively to reach a value at which a sudden and large change in state occurs. If both AS states and tipping points are now accepted as part of the mathematics of dynamic systems, "tipping points" were initially motivated by a controversial societal context [20], while AS states were initially motivated by ideas in ecology about rapid change [6]. Nonetheless, both concepts merged in the earth and climate sciences to create a common theoretical framework for AS states; Lenton [21], in a review about the concept of tipping points applied to environmental sciences, has retraced the epistemology of these concepts and stressed that "multiple equilibrium", "multiple stable states", "alternate stable states", "system shifts" and "tipping points" are all part of the same conceptual framework of the complex landscape of dynamic stability in natural systems. ...
... This function is an integral function of the dynamic processes that provides an indication of the strength of the equilibrium point and the extent of the perturbation shift from one stable state to another. Overall, the system is said to have AS states if the state variable trajectories can shift between different basins of attraction [6]. In other words, a shift to an AS state occurs when a perturbation creates a deviation of the trajectory large enough to cause it to tip over into another basin of attraction. ...
In their 2023 book, “The Blue Compendium: From Knowledge to Action for a Sustainable Ocean Economy”, Lubchenko and Haugan invoked alternate stable (AS) states marginally as an undesired consequence of sources of disturbance on populations, communities and ecosystems. They did not provide detailed arguments, but considered the existence of AS states as a given. Conversely, May, in his 1977 Nature article, pointed out that, when applied to systems that are complex, “the [AS states] theory remains largely metaphorical”. This is the starting point of this critical review, which aims to re-examine the general theory behind AS states in ecological systems and its applications to marine ecology and conservation. The focus is first on theory, taking as examples communities that sustain competition and studying the relative importance of the fluxes of individuals between simple low-dimension, interconnected systems. We find that a minimal formulation of fluxes is sufficient to obtain a set of non-null multiple stable (MS) states and to trigger shifts between AS states when fluxes become large enough. This provides new insights into the theory of rescue and mass effects by distinguishing them through a threshold at which the system dynamics shift from one stable equilibrium to another. Then, we consider how the theoretical framework of AS states has been applied in marine environments. It appears that many applications have confounded shifts between AS states and changes in the structure of systems, particularly when the complexity of the systems increases. The main difficulty for any application remains that the concepts of MS and AS states can only be established and validated for low-dimension systems and simplified experiments. This is because the mathematical properties of models that describe large-dimension, complex systems deviate from the observed characteristics of their real-world counterparts. There are many intriguing scientific challenges around the plausible shifts between AS states, but a deeper understanding and characterization of their occurrence in nature would require a significant investment in modeling to formulate predictive ecosystem models.
... Disturbance may more or less affect a community composition and state depending on its resistance and resilience, two important aspects of ecosystem stability (Fig. 5;Lewontin 1969, Holling 1973, Beisner et al. 2003, Lake 2013, Nimmo et al. 2015. Resistance is a community's ability to resist disturbance and change (Lake 2013, Nimmo et al. 2015. ...
... Resilience describes a community's elasticity and its capacity to return to a stable state after being affected by disturbance (Holling 1973). Ecosystems and communities are conceptualized as dynamic entities as disturbance may provoke strong structural changes, affecting how communities are shaped and individual species interact with the environment and with each other (Lewontin 1969, Beisner et al. 2003. Within the same ecological parameters, communities may shift/cycle between several alternative stable states when disturbed (Lewontin 1969, Beisner et al. 2003. ...
... Ecosystems and communities are conceptualized as dynamic entities as disturbance may provoke strong structural changes, affecting how communities are shaped and individual species interact with the environment and with each other (Lewontin 1969, Beisner et al. 2003. Within the same ecological parameters, communities may shift/cycle between several alternative stable states when disturbed (Lewontin 1969, Beisner et al. 2003. The disturbance itself however is not the only parameter conditioning the community equilibrium. ...
Marine infrastructures offer new substrates, colonized by a variety of organisms (biofouling), but are different from natural habitats since environmental filters and ecological processes differ, biotic composition differs from natural habitats, and they are characterized by a high diversity and abundance of non-indigenous species (NIS). Artificialization in marinas modifies hydrodynamism, affecting the water column characteristics like temperature and favoring the concentration of anthropic disturbances like pollutants. Environmental gradients may be present, with higher levels of disturbance in the innermost parts of marinas, acting as selective filters for organisms. The present work aimed to understand the diversity and functioning of sessile communities in marinas by studying how disturbance gradients shape community structure and function between the entrances of marinas and their more disturbed inner parts. A particular focus laid on NIS, which are common in marinas and constitute an important societal challenge. An experimental approach (reciprocal transplant) in six marinas from two regions (Mediterranean, Atlantic), revealed that differences in community structure are caused by local pollution levels, associated to local adaptation at small spatial scale (<100m). However, other processes might affect these dynamics like biotic interactions (predation) and pulse disturbances (heat waves). In the context of climate change, we also tested how projected seawater warming (+3°C) may impact marina communities and might favor NIS. These results might help understanding how disturbances in marine urban ecosystems drive biodiversity and especially the prevalence of NIS.
... In conducting regime shift studies, one of the most critical analyses involves determining the stable or equilibrium points of the dynamic system state (Yodzis 1981;Allesina & Tang 2012). By simply discovering that a system is at its equilibrium point, how it arrived at this point and where it is headed can be predicted (Lewontin 1969;Holling 1973). To date, many models and methods (such as early warning signals), based on alternative states theory and application of metrics to monitor the featured fluctuations in abundance (such as biomass, cover or nutrition, among others fluctuations) or traitbased (body size) signals of instability, are providing deeper understand of regime shifts across diverse systems (Scheffer et al. 2009;Dakos et al. 2012;Clements & Ozgul 2018). ...
... and, thus, corresponds to the global stable points of ecosystem states (global stability) under a given disturbance. This removes the limitation of current methods in determining the attraction domain or the stable point (local stability) using statistical or difference equations(Lewontin 1969).Because energy flow is realistic and integrates measures of states, estimating it from observed data still remains a challenge because of the different driving factors at each energy-flow path in trophic levels. Energy flow can only be partially estimated or quantified through experimental measurements and experiential equations (Barnes et al. 2018), indicating that it is very difficult and practically impossible to accurately acquire the transferring efficiency of energy-flow for each edge of the path of the trophic network. ...
Complex ecosystems exhibit more nonlinearity and stochasticity than the simple ones, rendering timely and accurate detection regime shifts in complex dynamic ecosystems a challenge. To resolve this dilemma, one of the most critical steps is to determine and quantify the equilibrium states reached by complex ecosystems under a given disturbance. This study utilizes the energy-transfer-network equilibrium model based on Nash-equilibrium theory and the maximum power principle to quantify and predict the equilibrium state of a complex ecosystem with multiple trophic levels. The model successfully simulated ecosystem energy transfer under equilibrium and quantified ecosystem state. The application of the model to monitor the aboveground biomass of a long-term dataset of un-grazed steppe achieved the description and prediction of the regime shift. This approach can possibly be used not only to find the equilibrium state for complex and simple ecosystems but also to remove the limitations of current methods to determine the attraction domain or stable points through statistical or difference equations in regime shift studies.
... Ecologists have long had an interest in how and why abiotic or biotic drivers can lead to changes in the resilience of a specific ecosystem state, and under what circumstances such drivers will result in an ecosystem potentially moving into a different stable state [2][3][4] . There is evidence that such ecological regime shifts can be driven by climatic factors like increased warming, heat waves, and droughts 5,6 . ...
... temperature and relative humidity) makes it difficult to predict the shape of the phase diagram, and therefore whether we can expect alternative stable states in the focal example. For such cases, the dominance of the dung beetle community could (1) shift in a linear fashion toward the functional group favored by climatic conditions; (2) shift between functional groups in non-linear threshold response to climatic conditions without hysteresis; or (3) shift between functional groups in non-linear threshold response to climatic conditions with hysteresis -and thus showing bistability (see Fig. 1b, or 12 ). Other possibilities, e.g. a non-linear shift between functional groups where one group is favored at intermediate climatic conditions 12 are discarded as the invader is better suited for warmer and drier conditions. ...
Although biological invasions play an important role in ecosystem change worldwide, little is known about how invasions are influenced by local abiotic stressors. Broadly, abiotic stressors can cause large-scale community changes in an ecosystem that influence its resilience. The possibility for these stressors to increase as global changes intensify highlights the pressing need to understand and characterize the effects that abiotic drivers may have on the dynamics and composition of a community. Here, we analyzed 26 years of weekly abundance data using the theory of regime shifts to understand how the structure of a resident community of dung beetles (composed of dweller and tunneler functional groups) responds to climatic changes in the presence of the invasive tunneler Digitonthophagus gazella. Although the community showed an initial dominance by the invader that decreased over time, the theory of regime shifts reveals the possibility of an ecological transition driven by climate factors (summarized here in a climatic index that combines minimum temperature and relative humidity). Mid and low values of the driver led to the existence of two alternative stable states for the community structure (i.e. dominance of either dwellers or tunnelers for similar values of the climatic driver), whereas large values of the driver led to the single dominance by tunnelers. We also quantified the stability of these states against climatic changes (resilience), which provides insight on the conditions under which the success of an invasion and/or the recovery of the previous status quo for the ecosystem are expected. Our approach can help understand the role of climatic changes in community responses, and improve our capacity to deal with regime shifts caused by the introduction of exotic species in new ecosystems.
... This long-term persistence has motivated the assumption that Marantaceae forests could be an alternative stable state, i.e., a vegetation community arising from a succession that has been deflected or arrested, to dense mixed-species forests in the Congo Basin (Tovar-Ingar, 2015). Since its introduction into ecology (Lewontin, 1969), 'alternative stable state' or 'alternative stable equilibrium' has become an influential concept (Soto and Puettmann, 2020). It has evoked a lot of attention by both theoreticians and empiricists and stimulated a large body of research activities. ...
Marantaceae forests are tropical rainforests characterized by a continuous understory layer of perennial giant herbs and a near absence of tree regeneration. Although widespread in West‐Central Africa, Marantaceae forests have rarely been considered in the international literature. Yet, they pose key challenges and opportunities for theoretical ecology that transcend the borders of the continent. Specifically, we ask in this review whether open Marantaceae forests and dense closed‐canopy forests can be considered as one of the few documented examples of alternative stable states in tropical forests. First, we introduce the different ecological factors that have been posited to drive Marantaceae forests (climate, soil, historical and recent anthropogenic pressures, herbivores) and develop the different hypotheses that have been suggested to explain how Marantaceae forests establish in relation with other vegetation types (understory invasion, early succession after disturbance, and intermediate successional stage). Then, we review the underlying ecological mechanisms that can explain the stability of Marantaceae forests in the long term (tree recruitment inhibition, promotion of and resilience to fire, adaptive reproduction, maintenance by megaherbivores). Although some uncertainties remain and call for further empirical and theoretical research, we found converging evidence that Marantaceae forests are associated with an ecological succession that has been deflected or arrested. If verified, Marantaceae forests may provide a useful model to understand critical transitions in forest ecosystems, which is of particular relevance to achieve sustainable forest management and mitigate global climate change.
... Since the seminal work of Lewontin [43], the possibility for alternative stable states and transitions between them has been a recurrent topic (e.g. [44]). ...
In the Anthropocene, intensifying ecological disturbances pose significant challenges to our predictive capabilities for ecosystem responses. Macroecology—which focuses on emergent statistical patterns in ecological systems—unveils consistent regularities in the organization of biodiversity and ecosystems. These regularities appear in terms of abundance, body size, geographical range, species interaction networks, or the flux of matter and energy. This paper argues for moving beyond qualitative resilience metaphors, such as the ‘ball and cup’, towards a more quantitative macroecological framework. We suggest a conceptual and theoretical basis for ecological resilience that integrates macroecology with a stochastic diffusion approximation constrained by principles of biological symmetry. This approach provides an alternative novel framework for studying ecological resilience in the Anthropocene. We demonstrate how our framework can effectively quantify the impacts of major disturbances and their extensive ecological ramifications. We further show how biological scaling insights can help quantify the consequences of major disturbances, emphasizing their cascading ecological impacts. The nature of these impacts prompts a re-evaluation of our understanding of resilience. Emphasis on regularities of ecological assemblages can help illuminate resilience dynamics and offer a novel basis to predict and manage the impacts of disturbance in the Anthropocene more efficiently.
This article is part of the theme issue ‘Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere’.
... There is, therefore, a need for tools that bridge the gap between theoretical and empirical ecology so that resilience can be quantified in non-equilibrium ecosystems accounting for their stochasticity and dimensionality (Rogers et al., 2022). A very useful approach in resilience theory is the "vector field model" proposed by Lewontin (1969). The approach consists of an n-dimensional space defined by a set of variables that describe the state of the system (i.e., state variables). ...
The increasing incidence of extreme events combined with long-term pressures due to climate change and anthropogenic activities are seriously threatening ecosystems worldwide. Promoting ecological resilience (i.e., the ability of ecosystems to absorb changes and maintain their processes and functioning) is a pivotal target for biological conservation. Many empirical approaches to assess resilience have relied on the underlying assumption that, in the absence of disturbances, ecosystems would be in a 'static' baseline state. In reality, ecological systems are highly dynamic and undergo phases of development and reorganization resulting from natural successional changes and their response to multiple interacting variables. As such, ecosystem states can be better described by 'dynamic regimes' rather than stationary states. In this context, there is an urgent need to expand the common 'equilibrium-based' approaches used in empirical ecology to evaluate resilience so that they can be applied to non-static ecosystems. Here, we present our perspective on the relevance of approaches based on dynamic regimes to assess ecological resilience empirically. More specifically, we briefly review the concept of resilience and discuss the main challenges for empirical applications. Then, we review an approach based on ecological dynamic regimes and temporal trajectories that can be used to assess the ecological resilience of non-static ecosystems from empirical data. Approaches focused on dynamic regimes help evaluate the management effort necessary to restore a disturbed ecosystem. Besides, they facilitate the identification of the factors that must receive special attention for enhancing ecosystem resilience.
... A large body of theory developed over decades provides guidance for interpreting possible outcomes and explanation for sudden, large changes of community state. Catastrophe theory (Arnol'd, 1992;Thom, 1975;Zeeman, 1976) and the theory of alternative stable states (Lewontin, 1969;May, 1977) describe stable, asymptotic behaviours of systems and their possible outcomes, which have been a focus of ecologists and the topic of several reviews (e.g. Connell and Sousa, 1983;Peterson, 1984, Knowlton, 1992Scheffer et al., 2001;Petraitis andDudgeon, 2004, 2015b;Schröder et al., 2005;Dudgeon et al., 2010). ...
Background
Unprecedented influence of human activities on natural ecosystems in the 21st century has resulted in increasingly frequent large-scale changes in ecological communities. This has heightened interest in understanding such changes and effective means to manage them. Accurate interpretation of state changes is challenging because of difficulties translating theory to empirical study, and most theory emphasises systems near equilibrium, which may not be relevant in rapidly changing environments.
Scope
We review concepts of long-transient stages and phase shifts between stable community states, both smooth, continuous and discontinuous shifts, and the relationships among them. Three principal challenges emerge when applying these concepts. The first is how to interpret observed change in communities - distinguishing multiple stable states from long-transients, or reversible shifts in the phase portrait of single attractor systems. Second, is how to quantify the magnitudes of three sources of variability that cause switches between community states, (1) ‘noise’ in species’ abundances, (2) ‘wiggle’ in system parameters, and (3) trends in parameters that affect topography of the basin of attraction. Third, is how variability of the system shapes evidence used to interpret community changes. We outline a novel approach using critical length scales to potentially address these challenges. These concepts are highlighted by review of recent examples involving macroalgae as key players in marine benthic ecosystems.
Conclusions
Real-world examples show three or more stable configurations may exist, and transient stages may persist for long periods necessitating their respective consideration. Characteristic Length Scales (CLS) is a useful metric that uniquely identifies a community “basin of attraction”, enabling distinguishing phase shifts from long transients. Variabilities of CLS and timeseries data may likewise provide proactive management measures to mitigate phase shifts and loss of ecosystem services. Continued challenges remain distinguishing continuous from discontinuous phase shifts because their respective dynamics lack unique signatures.
... The second resilience category is also state space-based and referred to as ecological resilience. Ecological resilience applies to natural phenomena, including biological and network systems, that lack fixed stable points in their dynamics [22]- [24]. For example, predator-prey systems have predator and prey populations that vary over time. ...
Goal-based agents need to be resilient to perturbations in the world. Existing resilience definitions emphasize
maintenance-type goals
and, consequently, describe how well systems can recover and return to a desirable operating state after a perturbation. An alternative formulation of resilience is required for
achievement-type goals
that emphasize the ability to progress towards a goal state. This manuscript proposes a new formalism of resilience as a computational construct that accounts for an agent’s sensors, effectors, communication channels, and computational resources. Two metrics for comparing the resilience of different algorithms are derived, namely
power
and
efficiency
. Three case studies demonstrate how the metrics can be used to characterize power-efficiency tradeoffs in algorithm design. A common property of the resilient algorithms in the case studies is that they have the ability to exploit many possible world trajectories, often at the cost of failing to find optimal trajectories in unperturbed conditions.
... Consequently there should be a special focus on the representation of key processes in models to ensure their timescales of response are credible. Related to this is the issue of possible hysteresis behaviour (Lewontin, 1969), which effectively represents an infinite timescale of recovery, since return to the previous state is no longer possible. Any trajectory that led to hysteresis would then be excluded from acceptability. ...
Ecosystem-based management is mandated by international legislation, including the Marine Strategy Framework Directive (MSFD) in the EU. This introduces a requirement for marine environments to achieve "Good Environmental Status" or GES, implying that the ecosystem is in a healthy and biodiverse state which does not limit the management options of future generations. Indicators of GES typically refer to the current or past state; however, an alternative approach that defines GES in terms of being able to recover to the appropriate reference unperturbed state within 30 years if human activities cease has been suggested. In this study we evaluate this "longest recovery timescales" (LRT) approach using the StrathE2E2 "big picture" model, an end-to-end ecosystem model designed to evaluate both top-down and bottom-up effects at an ecosystem level. We ask whether the approach is enough to prevent severe depletion as well as ensuring recovery at some future time. We also ask whether implementation is practical given uncertainties in defining appropriate baselines for recovery, defining what recovery looks like relative to this baseline, and taking account of natural variability. We find that the main issues with implementation of LRT are a) defining the appropriate baseline for recovery in a changing environment, and b) ensuring that there is stakeholder acceptance of any recommended actions in the event that they differ substantially from current policy. Subject to these two issues, we conclude that the LRT method is a valuable addition to management in support of achieving GES alongside existing methods that focus on current or near-future states.
... To examine this possibility, the alternative stable states theory offers an adequate theoretical framework (Petraitis, 2013). The notion of alternative stable states can be traced back to Lewontin's (1969) discussion of community structural stability, followed closely by the seminal papers of Holling (1973), May (1973) and Noy-Meir (1975) on the existence of alternative attracting equilibrium points. These early ideas prompted a rapidly growing field of research, in which the current debate largely focuses on the issue of ecosystem stability in the event of disturbances. ...
Data-based modelling of the dynamic behaviour of ecological communities is a big challenge in systems ecology and conservation biology. Implementing such models to forecast future scenarios is key for supporting decisionmaking in ecological reserves, given the multiple disturbances threatening their future. Using demographic and dynamic data for three tree (or tree-like) species from the Pedregal de San ´Angel Ecological Reserve (Mexico City, Mexico), we constructed a family of dynamical models (using systems of ordinary differential equations) to reconstruct their dynamic interactions. The first two models considered two native species (Pittocaulon praecox and Buddleja cordata), with either antagonistic or cooperative interactions between them. These species have been considered ecosystem engineers playing different roles in the system and determining several community attributes. These models predict the transition from a stable steady state dominated by P. praecox (as reported in the 1950s) to the current community whose structure is apparently shifting to an alternative stable state dominated by B. cordata. The second pair of models additionally incorporate the invasive tree Eucalyptus camaldulensis, which exerts negative effects on all native plant species. The prediction of these models is an E. camaldulensis-dominated state with the exclusion of the native species from the reserve, provided this invasive species follows current population growth trends, without external intervention to check this process. Bifurcation analysis of this latter model allowed us to rationally design optimal intervention strategies that could potentially divert the trajectory from converging to an E. camaldulensis-only configuration into the stable coexistence of the native species. For the two-species and three-species models we made two versions, one with only competitive interactions and another one including a facilitation interaction between B. cordata and P. praecox. This analysis shows that facilitation is a requirement to achieve stable coexistence between the two native species, even in the presence of E. camaldulensis. The models constructed here, which integrate multiple data sources, help clarify conflicting empirical information regarding potential ecological mechanisms, and allow making predictions for strengthening the future management and E. camaldulensis control programs before its effects irreversibly modify the functioning and biodiversity of the biotic community protected in the reserve.
... The issues of alternative states of ecosystems in the context of stability and resilience were discussed already at the turn of the 1960's and 1970's ( Lewontin, 1969 ;Holling, 1973 ). Probably the first observations of alternating states in lakes, based on paleolimnological research, were made by Walker (1970) : ...
... These contrast states are maintained through different types of stabilizing feedback, with sudden drastic switches between these states [44,92]. A theory was first proposed in the 1960s as to whether two or more stable communities could be found in a given habitat [93]. Then, increasing empirical evidence supported the theory [94][95][96][97]. ...
Submerged macrophytes have attracted increasing attention in lake restoration due to the importance of their structuring communities and stabilizing functions in lake ecosystems. However, there is still a lack of systematic reviews on lake restoration with submerged macrophytes. Thus, we performed a systematic review based on a bibliometric analysis via analyzing and visualizing 934 published works from 1996 to 2023 from the Web of Science core collection. Publication characteristics were summarized, and keyword co-occurrence networks, reference co-citation analysis, and keyword burst tests were conducted. Our results suggest that the increasing attention in this field has partly resulted from the many water treatments and scientific schemes in Europe, China, and the USA and extensive international cooperation. The development of this field was divided into three stages based on keyword bursts (e.g., early, turning, and recent stages). Alternative stable states and biomanipulation laid the foundations of this field in the early stage. Progress in the field was discussed based on four aspects, the influence of environmental factors on submerged macrophytes, theory and mechanisms, targets, and evaluation and methods. Therefore, our results provide a new and comprehensive understanding of lake restoration with submerged macrophytes.
... Much of the conceptualization of disturbance that extends beyond precipitation-runoff events has origins in the ecological literature (Brookhaven Symposium on Biology, 1969;Connell, 1978;White and Pickett, 1985) including work specific to lotic ecosystems (Resh et al., 1988;Lake, 2000). The ecological literature has contributed significantly to the closely related concepts of resilience (Lewontin, 1969;Holling, 1973) and alternative stable states (Holling, 1973;May, 1977) to characterize the uncertainty and nonlinear dynamics of complex systems. Emerging from this literature are quantitative approaches to assess resilience and tipping points (Scheffer et al., 2001;Carpenter et al., 2006;Hillebrand et al., 2017;Hillebrand and Kunze, 2020). ...
River corridors integrate the active channels, geomorphic floodplain and riparian areas, and hyporheic zone while receiving inputs from the uplands and groundwater and exchanging mass and energy with the atmosphere. Here, we trace the development of the contemporary understanding of river corridors from the perspectives of geomorphology, hydrology, ecology, and biogeochemistry. We then summarize contemporary models of the river corridor along multiple axes including dimensions of space and time, disturbance regimes, connectivity, hydrochemical exchange flows, and legacy effects of humans. We explore how river corridor science can be advanced with a critical zone framework by moving beyond a primary focus on discharge-based controls toward multi-factor models that identify dominant processes and thresholds that make predictions that serve society. We then identify opportunities to investigate relationships between large-scale spatial gradients and local-scale processes, embrace that riverine processes are temporally variable and interacting, acknowledge that river corridor processes and services do not respect disciplinary boundaries and increasingly need integrated multidisciplinary investigations, and explicitly integrate humans and their management actions as part of the river corridor. We intend our review to stimulate cross-disciplinary research while recognizing that river corridors occupy a unique position on the Earth's surface.
... The stable state theory was first proposed in the 1960s (Lewontin, 1969) and described mathematically within ecological communities in the 1970s (May, 1977;Noy-Meir, 1975). This contemporary view states that all ecosystems (cyanospheres in this example) are exposed to gradual changes in climate, nutrients or biotic interactions, usually assumed to respond smoothly ( Figure 6.2a and b) (Scheffer et al., 2001). ...
The presence of taste and odour compounds (T&O) in drinking water lead to numerous complaints to water companies worldwide. Geosmin and 2-MIB are common T&O compounds, with Cyanobacteria being the primary biological source in drinking water reservoirs. Both compounds have low odour thresholds in humans and require expensive additional treatment. This thesis used molecular and statistical analysis of water from Welsh Water reservoirs, to provide a framework for predicting and monitoring T&O events and understanding their causes.
Elevated T&O concentrations were confined to warmer months, except for a one geosmin event in winter 2019. There was no correlation between cyanobacterial abundance and T&O concentrations, but qPCR analysis based on eDNA sampling demonstrated that geosmin synthase (geoA) was a suitable proxy for predicting geosmin concentrations. Abundances of geoA and 2-MIB cyclase (mic) were significantly non-linearly associated with high ammonium-to-nitrate ratios, identifying thresholds for heightened T&O risk. The ratio of total inorganic nitrogen to total phosphorous was significantly non-linearly associated with increases in geoA. Increased geoA was also significantly negatively associated with temperature and dissolved reactive silicate in all reservoirs. Next-generation sequencing of bacterial and algal communities showed that community compositions clustered according to T&O concentrations. Bacterial and algal co-occurrence networks uncovered significant positive and negative associations, highlighting cyanospheres in all reservoirs. Random Forest models were developed for geosmin (Alaw) and 2-MIB (Pentwyn) using significantly co-occurring taxa exposing indicative T&O taxa and the probable Cyanobacteria causing the T&O. Cyanobacteria had more negative than positive associations in their cyanospheres.
This thesis illustrates the importance of nutrient ratios in triggering potential geosmin and 2-MIB events. It also indicates that Cyanobacteria subjected to environmental stress (negative biotic interactions and low temperatures) increase their T&O-production. These findings provide a useful framework for water monitoring to enable the prediction and possible prevention of T&O events.
... Alternative stable states have been a recurring, albeit controversial, theme in ecology since the 1960s (12)(13)(14). In this concept, microbiome composition is not determined exclusively by the environment, and therefore different community states are possible under the same environmental parameters (15)(16)(17)(18). ...
Biotic factors that influence the temporal stability of microbial community functioning are an emerging research focus for control of natural and engineered systems. Discovery of common features within community ensembles that differ in functional stability over time is a starting point to explore biotic factors. We serially propagated a suite of soil microbial communities through five generations of 28 d microcosm incubations to examine microbial community compositional and functional stability during plant-litter decomposition. Using DOC abundance as a target function, we hypothesized that microbial diversity, compositional stability, and associated changes in interactions would explain the relative stability of the ecosystem function between generations. Communities with initially high DOC abundance tended to converge towards a “low DOC” phenotype within two generations, but across all microcosms, functional stability between generations was highly variable. By splitting communities into two cohorts based on their relative DOC functional stability, we found that compositional shifts, diversity, and interaction network complexity were associated with the stability of DOC abundance between generations. Further, our results showed that legacy effects were important in determining compositional and functional outcomes, and we identified taxa associated with high DOC abundance. In the context of litter decomposition, achieving functionally stable communities is required to utilize soil microbiomes to increase DOC abundance and long-term terrestrial DOC sequestration as 1 solution to reduce atmospheric carbon dioxide concentrations. Identifying factors that stabilize function for a community of interest may improve the success of microbiome engineering applications.
Importance
Microbial community functioning can be highly dynamic over time. Identifying and understanding biotic factors that control functional stability is of significant interest for natural and engineered communities alike. Using plant litter decomposing communities as a model system, this study examined the stability of ecosystem function over time following repeated community transfers. By identifying microbial community features that are associated with stable ecosystem functions, microbial communities can be manipulated in ways that promote the consistency and reliability of the desired function, improving outcomes and increasing the utility of microorganisms.
... While focused mainly on resistance, earlier work byLewontin (1969) on the stability of ecological systems may also be viewed as a seminal reference for resilience. 5 FOOD SECURITY AND RESILIENCE: THE POTENTIAL … ...
Explains why we need to look beyond agriculture and trade and embrace a holistic food systems perspective
Broaches an array of issues relating to resilience and food security, including gender, climate change, and COVID-19
Appeals to a broad audience, from academics to policymakers, students to practitioners
This book is open access, which means that you have free and unlimited access
... While focused mainly on resistance, earlier work byLewontin (1969) on the stability of ecological systems may also be viewed as a seminal reference for resilience. 5 FOOD SECURITY AND RESILIENCE: THE POTENTIAL … ...
Climate change poses significant risks to our food systems, thus jeopardising the food security of millions of people worldwide. The concept of resilience is increasingly being proposed as a framework to find solutions to these challenges. In this chapter, we assess how resilience has been integrated in discussions about climate change and food security by both academics and practitioners. We performed a targeted review of the academic literature on climate change, food security, and resilience and found that despite a growing body of literature on the subject, the pathways through which actions translate into resilience and then into food security remain unclear. An examination of a sample of projects implemented through the Adaptation Fund revealed that many good practices with potential for resilience-building are used but also that suitable indicators and methods to monitor and evaluate resilience and its outcomes are lacking. Based on our findings, we conclude that while the concept of resilience has accompanied and may have favoured a transition towards more integrated approaches and interventions in work related to climate change and food security, further efforts are needed to identify an efficient and rational sequence of interventions to improve food security in response to climate threats.
... While focused mainly on resistance, earlier work byLewontin (1969) on the stability of ecological systems may also be viewed as a seminal reference for resilience. 5 FOOD SECURITY AND RESILIENCE: THE POTENTIAL … ...
Linking the concepts of food systems and resilience offers the opportunity to strengthen our understanding of these concepts, the potential they hold for more informed policy discussions, and the design and implementation of interventions that will better deliver on food security outcomes. This chapter outlines how these twin concepts can be linked conceptually and empirically. It argues that while we know much about certain elements of the food system, specifically production and consumption, our understanding of the processing and distribution components of the food system are weak. For example, market structure in the processing sector and market integration can contribute to food system resilience, but these are rarely measured at a country level. This makes efforts to measure resilience at the system-level challenging. Understanding what can make a resilient food system has important implications for policy and intervention design. Building resilient food systems requires that policymakers grapple with trade-offs and tensions such as those between the benefits of diversification versus gains from specialization; and how openness to trade reduces vulnerability to domestic shocks to the food system while exposing it to external shocks. How best to manage these will be an important challenge to address.
... While focused mainly on resistance, earlier work byLewontin (1969) on the stability of ecological systems may also be viewed as a seminal reference for resilience. 5 FOOD SECURITY AND RESILIENCE: THE POTENTIAL … ...
The aim of this introduction chapter is twofold. First it will set the scene, frame the overarching problem and present the central question of this volume: How does the concept of resilience help in improving our general understanding of the development process, in particular around the issue of food (in)security, and how does it influence the way development interventions around this question of food security are now programmed and implemented? To address this ambitious question, the entire series of chapters will adopt a food system approach. The second part of the introduction chapter will then ‘kick-start’ the discussion, first by providing some initial element of definition for the three concepts under consideration and then by highlighting some of the main discussions, debates or even contradictions that emerge in the literature around the definition, interpretations and application of those concepts.
... While focused mainly on resistance, earlier work byLewontin (1969) on the stability of ecological systems may also be viewed as a seminal reference for resilience. 5 FOOD SECURITY AND RESILIENCE: THE POTENTIAL … ...
Food systems have outcomes related to three goals: food and nutrition security; livelihoods and economic inclusion; and environmental sustainability. Place-based approaches help to delineate the adequate territories in which coalitions of actors can address such goals. In the case of food, they facilitate food system resilience through identifying opportunities for adaptation to change and offer risk management to deal with external shocks. In many countries, local authorities and communities were central in the early response to the COVID-19 pandemic. The South African experience is illustrative of their potential roles in a time of crisis. Although South Africa’s provinces have restricted competency for food system governance, the Western Cape Province adopted a pro-active approach and developed from 2014 a food security strategy where it commits to a wide range of interventions. Related and following local debates provided a fertile context which allowed further engagement about ways to improve food governance. It facilitated the emergence of multiple community-led initiatives to address the loss of livelihoods and food insecurity during the crisis. This experience illustrates the potential to produce polycentric forms of governance that can progressively result in collaborative governance; it also reveals how embryonic territorial approaches addressing food system issues can emerge.
... While focused mainly on resistance, earlier work byLewontin (1969) on the stability of ecological systems may also be viewed as a seminal reference for resilience. 5 FOOD SECURITY AND RESILIENCE: THE POTENTIAL … ...
The concept of resilience within urban food systems has gained significant academic and policy focus in recent years. This aligns with the increased global awareness of the problem of urban food insecurity, and increased focus on sub-national policies for sustainable development. COVID-19 demonstrated a series of vulnerabilities in the food system and the urban system. Academic work on urban food system resilience is wide ranging, however particular areas of focus dominate, focusing on urban agriculture, localized food systems, resilient city region food systems and the water-energy-food nexus. Renewed interest in resilience policy at the local government level has been amplified by global networks, whose framing of urban food systems resilience is embedded within the SDGs and the New Urban Agenda. Using findings from cities in five African countries, we argue for a re-framing of urban food system resilience that is inclusive of a wider set of factors shaping the form and function of the food system; that the urban system, specifically infrastructure, shapes the functioning of the food system and the ability of consumers to use the food system; and that the agency of urban food system users needs inclusion in understandings of, and efforts to increase, food systems resilience.
... While focused mainly on resistance, earlier work byLewontin (1969) on the stability of ecological systems may also be viewed as a seminal reference for resilience. 5 FOOD SECURITY AND RESILIENCE: THE POTENTIAL … ...
Achieving food security for the global population of 8 billion will be a challenge without functional, equitable, and resilient food systems. This chapter examines the history of how food security has been framed and addressed in international development, and the importance of a food systems approach and mindset in tackling food security. While this new food systems framing is important in bringing together the myriad of actors and components that food touches upon, food security has become more complex in the modern, challenged world, and functional food systems do not necessarily equate to improved food security. As international goals and commitments are made, policymakers must consider how food systems engage with other systems, and the failures and successes that history has taught us in efforts to achieve food security for all.
... While focused mainly on resistance, earlier work byLewontin (1969) on the stability of ecological systems may also be viewed as a seminal reference for resilience. 5 FOOD SECURITY AND RESILIENCE: THE POTENTIAL … ...
Resilience offers a useful lens for studying how human well-being and agri-food systems absorb and recover from a range of shocks and stressors, including the COVID-19 pandemic. Looking beyond the direct effects of observable shocks to the mechanisms that shape their impacts can guide our understanding of COVID-19 and leverage findings from the pandemic to better understand resilience to future shocks. We develop a conceptual framework for the multiple paths through which observed shocks interact with systemic mechanisms to influence resilience. We illustrate this framework with reference to the pandemic and policy responses as they unfolded in three rural areas in Malawi, Madagascar, and Kenya. Consistent with this framework, we find multiple pathways through which the pandemic affected household food security and resilience. Our findings highlight that, in some settings, the direct effects—in this case severe illness and mortality from SARS-CoV-2—may impact fewer people than the indirect impacts that arise as behaviors, markets, and policies adjust. We illustrate that although COVID-19 is a new shock, its massive, broad-reaching impacts manifest through familiar stressors and uncertainties that frequently burden poor rural populations in much of the low- and middle-income world.
... While focused mainly on resistance, earlier work byLewontin (1969) on the stability of ecological systems may also be viewed as a seminal reference for resilience. 5 FOOD SECURITY AND RESILIENCE: THE POTENTIAL … ...
The published narratives on food resilience of 16 development agencies are analysed. Using a rapid appraisal method, their positions and conception of resilience as a factor in food security are scrutinised. The study provides a snapshot of thought in 2020 and 2021. The COVID-19 pandemic, climate change, biodiversity loss and a policy focus on food systems have made resilience prominent in food policy. Firstly, concerns are raised that resilience may follow food security in its plasticity, blunting its critical edge. Secondly, the methods are explained. Thirdly, the findings are presented and organised by agency type. Fourthly, the findings are discussed. A fractured consensus around food resilience is noted. Despite broad agreement that resilience is a useful dimension for food security, there is no mutually agreed systematic conceptualisation or framework. Agencies use different definitions, approaches and measurements in their discourse, with varying levels of complexity. Some agencies adopt resilience as a buzzword, while others make it central to their institutional approach. The chapter concludes that, although resilience is emerging as core concept, its value would be strengthened with interdisciplinary attention paid to how food resilience is measured; unless this occurs, the risk is that resilience will be diluted as it becomes ubiquitous.
... While focused mainly on resistance, earlier work byLewontin (1969) on the stability of ecological systems may also be viewed as a seminal reference for resilience. 5 FOOD SECURITY AND RESILIENCE: THE POTENTIAL … ...
While the topic of food security has long been a focal point for research and policy concerned with development, resilience represents a newer area of work. Given the complexity of each topic on its own, the task of integrating the inherently multidimensional concepts of resilience and food security is an ambitious undertaking. Against this background, the present chapter was motivated by two questions: How can the integration of food security and resilience be conceptualized? What trends can be observed when food security and resilience are linked? To answer the first question, the chapter offers a new conceptual model that articulates possibilities for connecting food security and resilience. In response to the second question, a case study of selected policy documents and a sample of research was conducted. From a methodological perspective, the case study combined lexical analysis methods with a scoping review protocol. The findings from the policy review and from the research literature revealed that attempts to integrate food security and resilience were limited, inconsistent, and largely superficial. The conceptual model and the findings from the case study highlight the need for more coherent integration of work situated at the intersection of food security and resilience.
... (1) correctly quantify the contributions of deterministic versus stochastic variability; (2) successfully estimate "true" abundance dynamics; and INTRODUCTION Stability has long been a central focus in ecology (Holling, 1973;Ives et al., 1999;Lewontin, 1969;May, 1973;Pimm, 1984). Although many different definitions and aspects of stability exist, a unifying theme is that they aim to quantify variability and sensitivity to disturbance in dynamical systems (Donohue et al., 2016;Grimm & Wissel, 1997). ...
Ecological stability refers to a range of concepts used to quantify how species and environments change over time and in response to disturbances. Most empirically tractable ecological stability metrics assume that systems have simple dynamics and static equilibria. However, ecological systems are typically complex and often lack static equilibria (e.g., predator–prey oscillations, transient dynamics, chaos). Failing to account for these factors can lead to biased estimates of stability, in particular, by conflating effects of observation error, process noise, and underlying deterministic dynamics. To distinguish among these processes, we combine three existing approaches: state space models; delay embedding methods; and particle filtering. Jointly, these provide something akin to a deterministically “detrended” version of the coefficient of variation, separately tracking variability due to deterministic dynamics versus stochastic perturbations. Moreover, these variability estimates can be used to forecast dynamics, classify underlying sources of stochastic dynamics, and estimate the “exit time” before a state change takes place (e.g., local extinction events). Importantly, the time‐delay embedding methods that we employ make very few assumptions about the functions governing deterministic dynamics, which facilitates applications in systems with limited data and a priori biological knowledge. To demonstrate how complex dynamics without static equilibria can bias ecological stability estimates, we analyze simulated time series of abundance dynamics in a system with time‐varying carrying capacity and empirically observed abundance dynamics of the green algae Chlamydomonas terricola grown in a diverse microcosm mixture under variable temperature conditions. We show that stability estimates based on raw observations greatly overestimate temporal variability and fail to accurately forecast time to extinction. In contrast, joint application of state space modeling, delay embedding, and particle filters were able to: (1) correctly quantify the contributions of deterministic versus stochastic variability; (2) successfully estimate “true” abundance dynamics; and (3) correctly forecast time to extinction. Our results therefore demonstrate the importance of accounting for effects of complex, nonstatic dynamics in studies of ecological stability and provide an empirically tractable and flexible toolkit for conducting these measurements.
... Interactively learning concepts can help students move from relatively passive memorizing to actively applying new concepts in and outside the classroom (Franco & DeLuca, 2019). The game Jenga (Pokonobe Associates, 2016) can be viewed as a simple perspective of resilience, that is, how much disturbance a system (the Jenga tower) can absorb before it collapses (Holling, 1973) or shifts to another state (Beisner et al., 2003;Lewontin, 1969). In Jenga, players construct a tower of 54 rectangular wooden blocks and take turns pulling single blocks from the tower until there are no more moves or the tower collapses. ...
Solutions to global problems such as climate change and biodiversity loss require educational frameworks and accompanying teaching resources that are theory‐based, interdisciplinary, and accessible to broad undergraduate and graduate student audiences. Ecological resilience theory (ERT) is a framework with established interdisciplinary application to complex global problems, but despite an emphasis on the utility of resilience in national higher education frameworks, we found that many current ecology textbooks incorporate multiple definitions and highly variable amounts of discussion on core resilience concepts. To facilitate the use of innovative teaching resources in ERT in universities, this paper describes four free multimedia tools and templates that align with national education frameworks and are available for innovation and development by educators interested in ERT. The products are (1) content modules on core terms and concepts of ERT, (2) a classroom game and discussion, (3) interactive case studies, and (4) a complementary podcast based on resilience concepts and interviews with resilience experts to supplement formal classroom education. We contextualize the opportunities of ERT and thinking for students in university classrooms, as well as the benefits of involving graduate students and encouraging their initiative with this type of project. We conclude with a brief discussion of future opportunities for these types of educational resources. Our intent is that these resources be available for educators and researchers to facilitate interdisciplinarity, collaboration, and innovation to address complex global problems from a core educational framework of ERT.
... Table 3-1). Lewontin (1969) was the first to propose that natural communities can be found in one of several possible alternative stable states, where each state is characterized by a specific species assemblage and the states can be described as basins of attraction. Perturbations applied directly to the state variables (e.g., population densities) can push communities from one basin of attraction to another. ...
Many marine mammal populations are currently recovering from population depletion after overharvest. As marine mammals are often important predators in shaping marine ecosystems, there is a need to understand the impacts of recovering populations on other species and the marine ecosystem as a whole. The depletion and subsequent recovery of these species presents biologists with natural experiments to study their ecology, including drivers of their population dynamics and the function of the species in the ecosystem. This dissertation focuses on the recovery of a translocated population of sea otters (Enhydra lutris kenyoni) in Washington State. The presence or absence of sea otters, a keystone species, can dramatically influence marine community structure. The overall aim of this dissertation was to utilize the natural experiment of sea otter translocation to Washington State to understand drivers of sea otter population dynamics as well as the ecological role that sea otters play in Washington State. In Chapter 2, my coauthors and I found that the sea otter population in Washington has grown from an estimated 21 adult sea otters in 1977 to 2,336 adult sea otters in 2019, and the population is predicted to continue to grow and expand primarily to the south of the current range over the next 25 years. We also estimated that Washington State can support twice as many sea otters than previously estimated (equilibrium abundance of 6,080 vs. 2,734 sea otters), and that estimates of mean equilibrium density in currently occupied areas had the largest impact on predictions of population growth and range expansion. In Chapter 3, we quantified how sea otter population status (i.e., sea otter cumulative density) and habitat type (i.e., sea otter foraging in open water, kelp canopy, emergent rock, or intertidal) influence sea otter diet, and found that habitat was 1.77 times more important than sea otter population status in determining sea otter diet composition. We also found that sea otter long-term average rate of energy intake and diet diversity were negatively and positively correlated with sea otter cumulative density, respectively. In Chapter 4, we demonstrated the ecological role of sea otters in the nearshore marine ecosystem in Washington as a keystone species. We found that temporal transitions in the amount of kelp canopy were related to the duration of sea otter occupation, and that this relationship was more complex than a simple linear function. We also found that sea urchins were present at higher densities at sites more recently occupied by sea otters compared to long-occupied sites. In Chapter 5, we demonstrated the impact of sea otters as a recovering predator on the Pacific razor clam (Siliqua patula). We found that the magnitude of sea otter predation effects varied over time and space, with sea otter-caused razor clam mortality surpassing natural mortality in 2018 at Kalaloch Beach, occupied by sea otters since 2005. We also found that sea otters selectively consume the larger “recruit” size razor clams, the size that is also targeted in the recreational fishery, despite the smaller pre-recruit size clams being more abundant. Collectively, these results provide a deeper understanding of sea otter recolonization in Washington State as well as the ecological consequences of this recolonization.
... Phase shift, also known as regime shift (Petraitis and Dudgeon, 2004), is among the most serious consequences of environmental degradation and has been worrying scientists since the 1960s (Lewontin, 1969). This phenomenon is triggered when a disturbance, punctual or chronic, is more intense than the resistance of the community (i.e., the ability to absorb the impact while remaining within the limits of its natural variation c.f. Dudgeon et al., 2010). ...
... Knowledge is based on a mix of indigenous and academic study of what makes forest and farm ecosystems stable and how they respond to disturbance (Lewontin 1969;Holling 1973). Useful reviews have laid out 10 guiding principles for the integration of production and conservation in ways that maintain ecological resilience (Fischer et al. 2006): ...
Global climate resilience is a matter of life and death. In forest landscapes, 1.3 billion smallholder farmers, communities and Indigenous Peoples must organise for climate resilience to survive. With joint responsibility for managing much of the world’s remaining forests and securing food for many of the world’s poor, their resilience is also essential for global climate solutions.
This report is written for representatives of forest and farm producer organisations (FFPOs) and their technical support partners. It explains why climate resilience matters and what it is. It introduces a climate framework and how to build it – including 30 practical climate-resilience options. It includes new analysis of 10 international climate-resilience case studies that show the extraordinary extent to which FFPOs are pushing ahead with climate-resilience options.
Five pathways are advanced to scale up the beneficial impacts of FFPO climate-resilience action – including poverty reduction, biodiversity conservation, forest landscape restoration and climate change mitigation. The close fit between globally accepted generic principles for resilience and the day-to-day characteristics of FFPOs argues for them playing a more central role in bringing about the climate resilience that is important to us all.
... Como complemento a los modelos mencionados, y en oposición a los que postulan la existencia de una única trayectoria sucesional y estado de climax, Lewontin (1969) propuso un modelo en el que los ecosistemas se desarrollan por estados estables alternos. Este modelo predice una dinámica de umbrales bióticos o abióticos, los cuales mantienen el sistema dentro de un determinado estado estable por procesos de retroalimentación. ...
... Como complemento a los modelos mencionados, y en oposición a los que postulan la existencia de una única trayectoria sucesional y estado de climax, Lewontin (1969) propuso un modelo en el que los ecosistemas se desarrollan por estados estables alternos. Este modelo predice una dinámica de umbrales bióticos o abióticos, los cuales mantienen el sistema dentro de un determinado estado estable por procesos de retroalimentación. ...
... Como complemento a los modelos mencionados, y en oposición a los que postulan la existencia de una única trayectoria sucesional y estado de climax, Lewontin (1969) propuso un modelo en el que los ecosistemas se desarrollan por estados estables alternos. Este modelo predice una dinámica de umbrales bióticos o abióticos, los cuales mantienen el sistema dentro de un determinado estado estable por procesos de retroalimentación. ...
El libro está dividido en siete capítulos que incluyen principales aspectos ecológicos y sociales como: sus determinantes ecológicos, su dinámica vegetal natural, el régimen de disturbios natural y antrópico; los socioecosistemas y su gobernanza, y aspectos prácticos como la determinación de los escenarios de restauración; las estrategias necesarias para superar las barreras y el tipo de alcances, y resultados que pueden tener las acciones implementadas.
El primer capítulo es una introducción al ecosistema páramo, que trata sobre las diferentes definiciones, los determinantes ecológicos y los componentes bióticos y abióticos que se interrelacionan para dar lugar a la funcionalidad del ecosistema. Se discute sobre la influencia humana, por medio de sus actividades productivas, cada vez más demandantes, que generan riesgo y hacen más vulnerable su funcionalidad, en especial del suelo y la regulación hídrica. Se desarrolla brevemente el tema del cambio climático y cómo este factor refuerza las alteraciones de origen antrópico.
En el segundo capítulo, se exponen las diferentes formas de vida y crecimiento presentes en los páramos, se hace una revisión de las primeras propuestas y tipologías, así como la descripción y clasificación de los biotipos dominantes a lo largo de los gradientes altitudinales. Al final se presenta un caso de estudio, en el que el conocimiento de las formas de vida y otros atributos de las especies vegetales permiten la adecuada selección de plantas según el tipo de disturbio, las barreras a la restauración y las estrategias que se puedan desarrollar tales como: la reubicación, propagación y enriquecimiento del componente vegetal.
El tercer capítulo desarrolla el tema de la dinámica de la vegetación en el páramo, teniendo en cuenta que el factor que moldea las comunidades vegetales y sus cambios son las dinámicas naturales y antrópicas de los disturbios. Además, se hace principal énfasis en las dinámicas ocasionadas por disturbios antrópicos, y las consecuencias que estos tienen sobre los componentes del ecosistema y sus implicaciones para su restauración ecológica
El capítulo cuarto presenta una síntesis de los diferentes conjuntos de estrategias de restauración identificadas, haciendo énfasis en las técnicas y la aplicabilidad para la recuperación de algunos componentes en el ecosistema. Posteriormente desarrolla los diferentes escenarios de restauración que pueden encontrarse en los páramos, a partir de la identificación del ecosistema, comunidad o población de referencia, el disturbio que ha generado la degradación, el proceso de degradación y las barreras a la restauración derivadas de cada disturbio; a manera de síntesis, para cada escenario se presenta un cuadro que relaciona los diferentes conjuntos de estrategias con cada una de las barreras que pueden ser identificadas. El capítulo quinto desarrolla en síntesis el concepto de socioecosistema haciendo énfasis en sus componentes, con ejemplos prácticos y la forma como se puede insertar la restauración ecológica dentro de los socioecosistemas de páramo, a través de las diferentes formas de gobernanza.
El sexto capítulo trata de la investigación alrededor de la ecología y la fisiología de la germinación de semillas como un aporte fundamental para la aplicación y consolidación de los procesos de restauración ecológica y conservación de plantas nativas. El capítulo inicia con una revisión de los aspectos más relevantes para la selección de las especies y de las fuentes semilleras; realiza una síntesis con las recomendaciones más importantes para adelantar la recolecta de semillas para la investigación y para los procesos de restauración; finaliza la descripción y análisis de los factores más relevantes tanto para la generación de conocimiento, como para la germinación de semillas de especies nativas de páramo.
El capítulo séptimo plantea un modelo conceptual de la restauración ecológica en páramos que han sido transformados por actividades productivas como la ganadería y agricultura. Este modelo permite ordenar los resultados de la investigación y las estrategias de restauración que pueden ser llevadas a cabo en este tipo de ecosistemas, al comprender mejor los estados no deseados, dirigidos por los disturbios y las barreras asociadas; y los estados deseados, dirigidos por las estrategias de restauración y de manejo para estas áreas. De esta forma, el modelo conceptual ordena, prioriza y plantea una ruta de las estrategias que pueden llevar a que un páramo se recupere y de esta manera apoyar la toma de decisiones de manejo sobre estas áreas.
Este libro puede ser una herramienta de gran utilidad paras las personas e instituciones que planean, desarrollan e implementan procesos de restauración ecológica en los páramos y que están interesados en su manejo, conservación y restauración.
... The prevalent concept to explain this behavior is the notion of alternative stable states going back to the seminal works of Lewontin (1969), Holling (1973), Noy-Meir (1975), and May (1977). This means that more than one stable equilibrium state of the ecosystem exists for given environmental conditions. ...
We construct a generic ecosystem model that features the basic mechanisms of alternative stable states as well as two different stochastic influences. In particular, we use a mean‐reverting jump‐diffusion process to model the evolution of the ecosystem state over time. We review key concepts of multistability theory and the simple heuristics commonly employed to illustrate them. We then provide mathematical definitions for these concepts in the model context. Our contribution to the literature is twofold: we improve the representation of stochasticity in, and clarify key concepts of, multistability theory. The simplicity of the model enables a number of applications, such as finding economically optimal management strategies, identifying criteria for sustainable ecosystem management in a stochastic viability framework, deriving the probability of a regime shift, or empirically identifying the factors which have caused a specific regime shift.
Recommendations for resource managers:
Stochasticity is an important feature of multistable ecosystems and may by itself cause abrupt regime shifts. This highlights the role of active resilience management.
Previously deemed safe management strategies can trigger undesired regime shifts under changed environmental conditions. Hence, managers need to adapt to changing conditions.
Different types of management actions come with different probabilities of (un)desired regime shifts.
... If the equations governing the species are linear, only one stable state exists in which all species are present. Nevertheless, other stable states in which some of the species are absent may exist [154]. ...
Many systems on our planet shift abruptly and irreversibly from the desired state to an undesired state when forced across a “tipping point”. Some examples are mass extinctions within ecosystems, cascading failures in infrastructure systems, and changes in human and animal social networks. The ability to avoid such regime shifts or to recover quickly from such a non-resilient state demonstrates a system’s resilience; system resilience is a quality that enables a system to adjust its activities to retain its basic functionality when errors and failures occur. In the past 50 years, attention has been paid almost exclusively to low-dimensional systems; scholars have focused on the calibration of the resilience functions of such systems and the identification of indicators of early warning signals based on two to three connected components. In recent years, taking advantage of network theory and the availability of lavish real datasets, network scientists have begun to explore real-world complex networked multidimensional systems, as well as their resilience functions and early warning indicators. This report presents a comprehensive review of resilience functions and regime shifts in complex systems in domains such as ecology, biology, society, and infrastructure. The research approach includes empirical observations, experimental studies, mathematical modeling, and theoretical analysis. We also review the definitions of some ambiguous terms, including robustness, resilience, and stability.
... One challenge with the study of ecological stability is inconsistency in its definition and measurement. Ecologists have long recognised that there is no single agreed-upon definition of stability (Lewontin 1969;Pimm 1984;Grimm & Wissel 1997). This perhaps results from the different approaches theoreticians and empiricists have taken when measuring stability (Donohue et al. 2016). ...
Through global environmental change, humans are modifying the planet at an unprecedented rate and scale, triggering the ongoing biodiversity and climate crises. Ecological stability and the consistency of nature’s contributions to people are fundamental to the continued sustainability of human societies. Stability is a complex and multidimensional concept including components such as variability in time and space and the resistance to and recovery from disturbances. Global change has the potential to destabilise ecosystems, but the form and strength of the relationship between different global change drivers and dimensions of stability remains understudied, precluding general or mechanistic understanding. Here, I combine theory, a field experiment, and observational data from a high-resolution acoustic monitoring network to reveal the potential for multiple global change drivers to erode multidimensional ecological stability. Critically, I also show how biodiversity and natural habitats can buffer the destabilising effects of global environmental change on ecosystems and soundscapes, providing vital insurance against disturbance. In an era characterised by unrelenting global change and intensifying disturbance regimes, my results provide a key step towards a generalisable understanding—and ultimately management—of the stability of ecosystems and their contributions to human wellbeing.
Modification of food webs is a frequent cause of shifts in ecosystem states that resist reversal when the food web is restored to its original condition. We used the restoration of the large carnivore guild including gray wolves (Canis lupis), cougars (Felis concolor), and grizzly bears (Ursus arctos horribilis) to the northern range of Yellowstone National Park as a model system to understand how ecosystems might resist reconfiguration after the restoration of apex predators to the food web. The absence of wolves, cougars, and grizzly bears for nearly a century from the northern range was the primary cause of dramatic changes in riparian plant communities. Willows (Salix spp.) were suppressed in height by intense browsing by the dominant herbivore, elk (Cervus canadensis). The loss of activity by beavers (Castor canadensis) coincided with the loss of tall willows. We hypothesized that intense elk browsing interrupted the mutualism between willow and beavers: ecosystem engineering by beavers was a critical component of willow habitat and tall willows were a critical component of habitat for beavers. This interruption made riparian communities resilient to the disturbance caused by the restoration of apex predators. We hypothesized further that reductions in elk browsing attributable to reductions in elk population size were not sufficient to prevent the suppression of willow growth. To test these hypotheses, we conducted a 20‐year, factorial experiment that crossed simulated beaver dams with the exclusion of browsing. We found that willows grew to heights expected for restored communities only in the presence of dams and reduced browsing. Willows experiencing ambient conditions remained well below this expectation. We found no difference in heights or growth rates of willows in experimental controls and willows in 21 randomly chosen sites, confirming that the results of the experiment were representative of range‐wide conditions. A reorganized community of large herbivores was implicated in the suppression of willow growth. We conclude that the restoration of large carnivores to the food web failed to restore riparian plant communities on Yellowstone's northern range, supporting the hypothesis that this ecosystem is in an alternative stable state caused primarily by the extirpation of apex predators during the early 20th century.
Stochasticity or noise is omnipresent in ecosystems that mediates community dynamics. The beneficial role of stochasticity in enhancing species coexistence and hence in promoting biodiversity is well recognized. However, incorporating stochastic birth and death processes in excitable slow-fast ecological systems to study
its response to biodiversity is largely unexplored. Considering an ecological network of excitable consumer-resource systems, we study the interplay of network structure and noise on species’ collective dynamics. We find that noise drives the system out of the excitable regime, and high habitat patch connectance in the ordered as well as random networks promotes species’ diversity by inducing new steady states via noise-induced symmetry breaking.
Phase shift is characterized by an abrupt change in the structure of a community in response to a disturbance that can break its resistance, displacing it from its natural variation. This phenomenon has been recognized in several ecosystems and often points to human activities as the main cause. However, reactions of shifted communities to anthropogenic impacts have been less studied. In recent decades, heatwaves resulting from climate change have strongly affected coral reefs. Mass coral bleaching events are recognized as the main cause of coral reef phase shifts on a global scale. In 2019, an unprecedented heatwave hit the southwest Atlantic Ocean causing mass coral bleaching in non-degraded and phase-shifted reefs of Todos os Santos Bay, at an intensity never recorded in a 34-year historical series. We analyzed the effects of this event on the resistance of phase-shifted reefs, dominated by the zoantharian Palythoa cf. variabilis. Using benthic coverage data from 2003, 2007, 2011, 2017, and 2019, we analyzed three non-degraded reefs and three phase-shifted reefs. We estimated the coverage and bleaching of corals and P. cf. variabilis on each reef. There was a reduction in coral coverage in non-degraded reefs before the 2019 mass bleaching event (i.e., heatwave). However, there was no significant coral coverage variation after the event and the structure of non-degraded reef communities did not change. In phase-shifted reefs the coverage of zoantharians did not change significantly before the 2019 event, however, after the mass bleaching, there was a significant reduction in the coverage of these organisms. Here we revealed that the resistance of the shifted community was broken, and its structure was altered, indicating that reefs in this condition were more susceptible to bleaching disturbance than non-degraded reefs.
The oral microbiota is essential to the health of the host, yet little is known about how it responds to disturbances. We examined the oropharyngeal microbiota of 30 individuals over 40 weeks. As the oropharynx is an important gateway to pathogens, and as smoking is associated with increased incidence and severity of respiratory infections, we compared the microbiota of smokers and nonsmokers to shed light on its potential for facilitating infections. We hypothesized that decreased species diversity, decreased community stability, or increased differences in community structure could facilitate invading pathogens. We found that smoking is associated with reduced alpha diversity, greater differences in community structure, and increased environmental filtering. The effects of short-term perturbations (antibiotic use and participants exhibiting cold symptoms) were also investigated. Antibiotic use had a negative effect on alpha diversity, irrespective of smoking status, and both antibiotic use and cold symptoms were associated with highly unique bacterial communities. A stability analysis of models built from the data indicated that there were no differences in local or global stability in the microbial communities of smokers, compared to nonsmokers, and that their microbiota are equally resistant to species invasions. Results from these models suggest that smoker microbiota are perturbed but characterized by alternative stable states that are as stable and invasion-resistant as are the microbiota of nonsmokers. Smoking is unlikely to increase the risk of infectious disease through the altered composition and ecological function of the microbiota; this is more likely due to the effects of smoking on the local and systemic immune system. IMPORTANCE Smoking is associated with an increased risk of respiratory infections. Hypothetically, the altered community diversity of smokers' pharyngeal microbiota, together with changes in their ecological stability properties, could facilitate their invasion by pathogens. To address this question, we analyzed longitudinal microbiota data of baseline healthy individuals who were either smokers or nonsmokers. While the results indicate reduced biodiversity and increased species turnover in the smokers' pharyngeal microbiota, their ecological stability properties were not different from those of the microbiota of nonsmokers, implying, in ecological terms, that the smokers' microbial communities are not less resistant to invasions. Therefore, the study suggests that the increased propensity of respiratory infections that is seen in smokers is more likely associated with changes in the local and systemic immune system than with ecological changes in the microbial communities.
The stability of cultivated land ecosystem is crucial to the green and high-quality development of agriculture. Revealing its spatio-temporal differentiation is an important scientific issue to improve the resilience of cultivated land and ensure food security. In this paper, Shenyang, a typical region of Lower Liaohe Plain, is the study area. Starting from the stress buffer response process of cultivated land ecosystem stability, USLE, RWEQ, SDI, RSEI and grey relational model are used to clarify the relationship between the three, and depict the temporal and spatial differentiation pattern of cultivated land ecosystem stability. The results showed that the external stress intensity of cultivated land in Shenyang decreased as a whole, but the stress intensity of cultivated land distributed in the northern and southeast hilly areas increased. Most of the endogenous buffer strength has been improved, and the buffer capacity of cultivated land in the northern hilly region has declined on a large scale. More than half of the response intensity to the effect has been improved, while the response intensity of cultivated land in the west and north has generally declined. The stability of cultivated land ecosystem in Shenyang has been improved for the most part, but in the hilly areas in the north and southeast, the stability in the lower reaches of Liaohe River plain in the south has declined. Terrain conditions and high-intensity cultivation patterns are the important reasons for the temporal and spatial differentiation of cultivated land ecosystem stability in the study area. The study clarified the dynamic process of cultivated land ecosystem stability and provided an important way to grasp the scientific law of stability change.
In this paper, an SIR-SI mathematical model in the form of a system of integral equations describing the transmission of dengue disease between human and mosquitoes is proposed and analyzed. Age-dependent functions are used to describe the survival of individuals in human and mosquito populations. The basic reproduction number is derived and its relationship to the equilibria is also explored. The results show that the existence of the positive endemic equilibrium is determined by a threshold number. This threshold number is also the same one that determines the global stability of the equilibrium. The threshold acts like the known basic reproduction number in the counterpart differential equations model and also follows the same rule for the critical level of intervention. Furthermore, as an application, the effect of wolbachia infection is explored, such as how this infection changes the resulting threshold and what the consequence of its presence is in the dynamics of the disease. In this case, the decrease of the mosquitoes’ life expectancy and biting rate are used to reflect the effect of wolbachia bacterial infection on the mosquitoes. In other words, a mosquito which is infected by wolbachia has a lower life expectancy than a normal mosquito. The results, both from mathematical analysis and numerical examples, show that the presence of wolbachia has the potential as a biological control agent to eliminate the dengue in the human population. A comparison of the wolbachia introduction into the mosquito population with the existing strategy, such as vaccination, is also presented.
This article describes and compares three modelings of the relationship between Sama Bajo boat-dwellers Bagai land-dwellers social capital and the social resilience of Sama Bajo in three local social contexts of land-dwellers in Wakatobi National Park (WNP). The research was conducted from May 2018 until June 2019 in Mantigola Sama Bajo on Kaledupa Island, Lamanggau Sama Bajo on Tomia Island, and Mola Sama Bajo on Wangi-wangi Island. Information was collected from 240 respondents who were selected by spatial sampling technique. Using Structural Equation Modeling (SEM) analysis, we found that the structural model is effective for evaluating social resilience, particularly for Mantigola and Lamanggau Sama Bajo who interact with homogenous land-dwellers, namely Kaledupa and Tomia land-dwellers as well as a stepping stone to strengthen their social resilience capacity by taking into account social relation, livelihood, the human and financial capital of the land-dwellers in the marine preserve area. Despite the success shown, a key constraint is due to inadequacies when the structural modeling reflects the urban local social environment of Sama Bajo as stated by Mola Sama Bajo, who established their bridging capital to the heterogeneous land-dwellers. Future research should take limitations into account by identifying various land-dwellers who develop social ties with the boat-dwellers. Similar research should be taken into consideration to validate the modeling in Sama Bajo populations that live in open access types. This is crucial to determine if other characteristics of Sama Bajo social resilience appear in the social setting of a different kinds of marine preserve areas.
Ecology and evolutionary biology have focused on how organisms fit the environment. Less attention has been given to the idea that organisms can also modify their environment, and that these modifications can feed back to the organism, thus providing a key factor for their persistence and evolution. There are at least three independent lines of evidence emphasizing these biological feedback processes at different scales: niche construction (population scale); alternative biome states (community scale); and the Gaia hypothesis (planetary scale). These feedback processes make us rethink traditional concepts like niche and adaptation. We argue that organism–environment feedbacks must become a regular part of ecological thinking, especially now that the Earth is quickly changing.
Increasing wildfire severity highlights the need for large-scale shifts in management of fire-prone landscapes. While prior research has focused on cognitive biases, social norms, and institutional disincentives that limit reform, such factors are best understood as components of feedback loops that operate within complex adaptive systems. We evaluated the prominence and function of feedback loops embedded in cognitive maps—beliefs about patterns of causal relationships that drive system dynamics—elicited from a diverse cross-section of stakeholders in a fire-prone region in the U.S. West. We demonstrate that cognition of feedback loops is rare among individuals, but increasingly prominent within aggregations of cognitive maps, which underscores the importance of collaborative decision-making. Our analysis further reveals a bias toward perception of amplifying feedback loops and of loops in which management actions result in desirable outcomes, which points to areas where progress may be made in reforming wildfire risk governance.
Freshwater lakes are among the most important ecosystems for both human and other biological communities. They account for about 87% of surface freshwater in the planet, thus constituting a major source of drinking water. They also provide a wide range of ecosystem services that go from the sustenance of a rich biodiversity to the regulation of hydrological extremes; from the provision of a means for recreation to the support of local economies, e.g., through tourism and fisheries, just to cite a few. Lakes are now also widely recognised as natural early warning systems, their responses potentially being effective indicators of local, regional and global scale phenomena such as acidification and climate change, respectively. This is because of their high sensitivity to environmental factors of the most diverse nature that can rapidly alter the course of their evolution. Examples of this are the observed abrupt shifts between alternative stable states in shallow lakes, which led them to become the archetype, go-to example in alternative stable state theory. Therefore, attaining a good scientific understanding of the many processes that take place within these ecosystems is fundamental for their adequate management. Among the tools that serve this purpose, ecological models are particularly powerful ones. Since their introduction in the 1960s, the development of mechanistic ecological models has been driven by their wide spectrum of potential applications. Nevertheless, these models often fall into one of the two following categories: overly simplistic representations of isolated processes, with limited potential to explain real-world observations as they fail to see the bigger picture; or overly complex and over-parameterised models that can hardly improve scientific understanding, their results being too difficult to analyse in terms of fundamental processes and controls. Moreover, it is now well known that an increased complexity in the mechanistic description of ecological processes, does not necessarily improve model accuracy, predictive capability or overall simulation results. To the contrary, a simpler representation allows for the inclusion of more links between model components, feedbacks which are usually overlooked in highly-complex models that partially couple a hydro-thermodynamic module to a biogeochemical one. However, ecological processes are now known to have the potential to significantly alter the physical response of aquatic ecosystems to environmental forcing. For example, steadily increasing concentrations of coloured dissolved organic carbon, a process known as brownification (also browning), as well as the intense phytoplankton blooms that characterise lakes undergoing severe nutrient enrichment, a process known as eutrophication, have been shown to have the potential to alter the duration of the stratified period, thermal structure and mixing regime of some lakes. In this thesis, with the aim of addressing the limitation of partially-coupled models to account for such feedbacks, we further develop a process-based model previously reported in scientific literature. Subsequent studies have already built upon this model in the last few years. In Chapter 2, we do so too by integrating hydro-thermodynamics and biogeochemistry in a reduced complexity framework, i.e., customising the model so that each version only includes the fundamental processes that, brought together, sufficiently describe the studied phenomena. Two case studies served the purpose of testing the adaptability and applicability of the developed model under different configurations and requirements. Limnological data for these two studies were measured at high spatial and temporal resolutions by means of an automated profiling system and recorded as part of two large-scale mesocosm experiments conducted in 2015 and 2016 at the IGB LakeLab in Lake Stechlin, Brandenburg, Germany. Meteorological datasets were also made available to us for both periods by the German Federal Environment Agency. The scope of the first experiment, which we describe in Chapter 3, was that of detecting any changes attributable to eutrophication and browning, in the competition for nutrients and light between four different groups of lake primary producers. These four groups are phytoplankton, periphyton, epiphyton and macrophytes. The model version for this study, therefore, includes equations for all four groups. By tailoring the model to these very specific needs with relative ease, we demonstrate its versatility and hint at its potential. The second experiment, described in Chapter 4, sought to shed light on the largely unknown effects of an increase in the diffuse luminance of the night sky that is due to artificial light at night (artificial skyglow) on lake metabolic rates, i.e., gross primary productivity, ecosystem respiration and net ecosystem productivity (the difference between the first two). For this purpose, an empirical equation for dissolved oxygen concentration was included, the parameters of which were estimated by means of a Markov Chain Monte Carlo sampling method within a Bayesian statistical framework, showing the compatibility, with these statistical methods, of our otherwise fully deterministic model. In Chapter 5, we present a theoretical study on the ecological controls of light and thermal patterns in lake ecosystems. A series of simulations were performed to determine in which cases ecological processes such as eutrophication and brownification may have an observable effect on the physical response of lakes to environmental forcing, which we assessed along a latitudinal gradient. Results show that, in general, across all examined latitudes, and consistent with previous studies, accounting for phytoplankton biomass results in higher surface temperatures during the warm-up phase, slightly lower water temperatures during the cool-down phase, and a shallower thermocline throughout the entire stratified period. This effect is relatively more important in eutrophic lakes where intense blooms are likely. This importance, however, decreases as lakes get browner. Finally, in line with the overall scope of the SMART EMJD, in Chapter 6 we illustrate the case of Ypacaraí Lake, the most important lake in landlocked Paraguay, hoping to provide an example of how interdisciplinary research and international intersectoral collaboration can help bridge the gap between science and management of freshwater ecosystems. This lake presents very special hydro-ecological conditions, such as very high turbidity that can impair phytoplankton growth despite its nutrient-based trophic state indices having consistently fallen within the hyper-eutrophic range in recent years. A strong interest in its complex functioning, through modelling, was taken early on. This led to a collaborative research line being established among several public and private institutions in Italy, Germany and Paraguay. Results so far include: • three concluded UniTN Master theses in Environmental Engineering, partly developed in Paraguay, the first two in collaboration with the “Nuestra Señora de la Asunción” Catholic University (UCNSA) and the third one with the National University of Asunción (UNA); • a collaborative UCNSA-UniTN research proposal submitted for consideration to receive funding through the PROCIENCIA Programme of the National Council of Science and Technology of Paraguay (CONACYT); and • the first multidisciplinary review that has ever been published about the case of Ypacaraí Lake, which highlights the importance of such a collaborative and integrative approach to further advance scientific knowledge and effectively manage this ecosystem.
Biomes of the world have long been assumed to be determined by climate. Major disparities, where open low biomass systems occurred in the same climate zone as closed forests have been dismissed as products of deforestation. Many of these open ecosystems of the world, have been shown to be of ancient origins, stable alternatives to forests, and typically maintained by disturbance regimes. Open ecosystems include some of the most biodiverse regions in the world. They are often consumer-controlled by large mammal herbivores or fire. Mosaics of closed forest and open ecosystems have been interpreted as alternative stable states with each state maintained by positive feedbacks to environmental conditions that maintain that state. For example, flammable grasses maintain fires which consume woody plants, while closed forests exclude flammable grasses by shading them out. Understanding open ecosystems may therefore require some radical revision of familiar ecological concepts, starting with the hypothesis that climate largely determines world vegetation patterns. Open ecosystems function differently from forests in an earth system context affecting the hydrological cycle, rates of rock weathering, and presenting a different planetary surface to solar radiation reaching the earth’s land surface. Open ecosystems require explicit attention in conservation policy and management.
Humans were considered external drivers in much foundational ecological research. A recognition that humans are embedded in the complex interaction networks we study can provide new insight into our ecological paradigms. Here, we use time-series data spanning three decades to explore the effects of human harvesting on otter–urchin–kelp trophic cascades in southeast Alaska. These effects were inferred from variation in sea urchin and kelp abundance following the post fur trade repatriation of otters and a subsequent localized reduction of otters by human harvest in one location. In an example of a classic trophic cascade, otter repatriation was followed by a 99% reduction in urchin biomass density and a greater than 99% increase in kelp density region wide. Recent spatially concentrated harvesting of otters was associated with a localized 70% decline in otter abundance in one location, with urchins increasing and kelps declining in accordance with the spatial pattern of otter occupancy within that region. While the otter–urchin–kelp trophic cascade has been associated with alternative community states at the regional scale, this research highlights how small-scale variability in otter occupancy, ostensibly due to spatial variability in harvesting or the risk landscape for otters, can result in within-region patchiness in these community states.
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