Exotic Grass Invasions: Applying a Conceptual Framework to the Dynamics of Degradation and Restoration in Australia’s Tropical Savannas

Plant invasions can cause severe degradation of natural areas. The ability of an ecosystem to recover autogenically from degradation following weed control is in part determined by the type and magnitude of changes to both biotic and abiotic processes caused by the invasion and how these interact with structural and functional components of the ecosystem. Recently, a number of conceptual frameworks have been proposed to describe the dynamics of degradation and regeneration in degraded ecosystems. We assessed the utility of one of these frameworks in describing the degradation and restoration potential of Australia’s tropical savannas following exotic grass invasion. First, we identified easily measured structural characteristics of putative states. We found that a continuous cover of the exotic grasses Gamba grass (Andropogon gayanus Kunth.) and Perennial mission grass (Pennisetum polystachion (L.) Schult.) under an intact tree canopy was a common state with an understorey characterized by reduced species richness and abundance and a change in the relative contribution of functional groups. Further degradation led to a state where the canopy was severely reduced and the impacts on the understorey were more severe. In both states, the seed bank was substantially less degraded than the understorey vegetation. Guided by the framework, we combined our study with other studies to construct a conceptual model for degradation in exotic grass‐invaded savannas.     

A framework for understanding physical ecosystem engineering by organisms

While well‐recognized as an important kind of ecological interaction, physical ecosystem engineering by organisms is diverse with varied consequences, presenting challenges for developing and using general understanding. There is also still some uncertainty as to what it is, and some skepticism that the diversity of engineering and its effects is amenable to conceptual integration and general understanding. What then, are the key cause/effect relationships and what underlies them? Here we develop, enrich and extend our extant understanding of physical ecosystem engineering into an integrated framework that exposes the essential cause/effect relationships, their underpinnings, and the interconnections that need to be understood to explain or predict engineering effects. The framework has four cause/effect relationships linking four components: 1. An engineer causes structural change; 2. Structural change causes abiotic change; 3. Structural and abiotic change cause biotic change; 4. Structural, abiotic and biotic change can feedback to the engineer. The first two relationships describe an ecosystem engineering process and abiotic dynamics, while the second two describe biotic consequence for other species and the engineer. The four relationships can be parameterized and linked using time‐indexed equations that describe engineered system dynamics. After describing the relationships we discuss the utility of the framework; how it might be enriched; and briefly how it can be used to identify intersections of ecosystem engineering with fields outside ecology.     

Restoration Ecology and the Ecosystem Perspective

The ecosystem perspective provides a framework within which most other aspects of the ecology of restoration can be incorporated. By considering the ecosystem functions of a restoration project, the restorationist is forced to consider the placement of the project in the landscape—its boundaries, its connections or lack thereof to adjoining ecosystems, and its receipts and losses of materials and energy from its physical surroundings. These characteristics may set limits on the kind(s) of biotic communities that can be created on the site. The ecosystem perspective also gives restorationists conceptual tools for structuring and evaluating restorations. These include the mass balance approach to nutrient, pollutant, and energy budgets; subsidy/stress effects of inputs; food web architecture; feedback among ecosystem components; efficiency of nutrient transfers, primary productivity and decomposition as system-determining rates; and disturbance regimes. However, there are many uncertainties concerning these concepts, their relation to each other, and their relationships to population- and community-level phenomena. The nature of restoration projects provides a unique opportunity for research on these problems; the large spatial scale of restorations and the freedom to manipulate species, soil, water, and even the landscape could allow ecosystem-level experiments to be conducted that could not be performed otherwise.     

An outcome-based model for predicting recovery pathways in restored ecosystems: The Recovery Cascade Model

Restoration is increasingly the focus of ecosystem management. Few conceptual models exist for predicting the consequences of restoration, especially those that predict the stages of recovery following restoration. Existing models focus either on defining endpoints for recovery or on defining ecosystem processes, but often do not identify barriers to recovery or potential negative effects of restoration. We describe a conceptual model that identifies the outcomes of the recovery pathways following flow restoration in rivers: the Recovery Cascade Model. The model identifies six general aspects of recovery following restoration: physical ecosystem change; creation of, or improvement in habitat condition; reconnection of the restored area to adjacent ecosystems; recolonization of the restored area; resumption of ecological processes; re-establishment of biotic interactions and reproduction by colonists in the restored area. These aspects may occur in sequence, such that recovery is blocked by a single barrier. The model accommodates feedback loops and includes strong connections between physical processes and ecosystem processes, but also identifies factors that are important in achieving endpoints such as potential barriers to further recovery. Identification of barriers to recovery enables improved planning to maximise the positive effects of restoration. By focussing on outcomes, the model provides a planning tool for managers that can be adapted for different ecosystems and restoration methods and which can be used to identify the amenities that an ecosystem will deliver at different stages of recovery. Ecosystem recovery is as much about overcoming barriers as it is about restorative actions.     

Ecosystemic structural–functional approach of the state and transition model

Objective: To contribute to the integration of key ecological concepts such as dynamic equilibrium, critical threshold, resistance and resilience to the ‘State and Transition Model’ (STM), in order to apply them in a more feasible way for rangeland management. Methods: Review and discussion of conceptual models and applied literature, including examples of rangeland dynamics. Results and Conclusions: We propose to enhance the STM considering two principal axes: (a) the x axis determined by structural ecosystem changes (vegetation and soil) and (b) the y axis determined by ecosystem functions and/or processes (recruitment, rain use efficiency). These axes define what we will call Structural–Functional State and Transition Model (SFSTM). Both axes of SFSTM make it possible to determine and quantify states and transitions, critical thresholds and to evaluate the resistance and resilience of an ecosystem to a given disturbance. The critical threshold is identified by structural and functional thresholds (x and y axes), thus defining the point where the ecosystem loses its resilience. Furthermore, in the supplementary file we provide examples with field data from Patagonia to illustrate the SFSTM. The proposed SFSTM has large implications for rangeland research and management, facilitating the understanding and integration of key concepts to enhance the STM. The identification of variables to assess structure and processes makes the model more useful.     

The importance of ecological memory for trophic rewilding as an ecosystem restoration approach

Increasing human pressure on strongly defaunated ecosystems is characteristic of the Anthropocene and calls for proactive restoration approaches that promote self‐sustaining, functioning ecosystems. However, the suitability of novel restoration concepts such as trophic rewilding is still under discussion given fragmentary empirical data and limited theory development. Here, we develop a theoretical framework that integrates the concept of ‘ecological memory’ into trophic rewilding. The ecological memory of an ecosystem is defined as an ecosystem's accumulated abiotic and biotic material and information legacies from past dynamics. By summarising existing knowledge about the ecological effects of megafauna extinction and rewilding across a large range of spatial and temporal scales, we identify two key drivers of ecosystem responses to trophic rewilding: (i) impact potential of (re)introduced megafauna, and (ii) ecological memory characterising the focal ecosystem. The impact potential of (re)introduced megafauna species can be estimated from species properties such as lifetime per capita engineering capacity, population density, home range size and niche overlap with resident species. The importance of ecological memory characterising the focal ecosystem depends on (i) the absolute time since megafauna loss, (ii) the speed of abiotic and biotic turnover, (iii) the strength of species interactions characterising the focal ecosystem, and (iv) the compensatory capacity of surrounding source ecosystems. These properties related to the focal and surrounding ecosystems mediate material and information legacies (its ecological memory) and modulate the net ecosystem impact of (re)introduced megafauna species. We provide practical advice about how to quantify all these properties while highlighting the strong link between ecological memory and historically contingent ecosystem trajectories. With this newly established ecological memory–rewilding framework, we hope to guide future empirical studies that investigate the ecological effects of trophic rewilding and other ecosystem‐restoration approaches. The proposed integrated conceptual framework should also assist managers and decision makers to anticipate the possible trajectories of ecosystem dynamics after restoration actions and to weigh plausible alternatives. This will help practitioners to develop adaptive management strategies for trophic rewilding that could facilitate sustainable management of functioning ecosystems in an increasingly human‐dominated world.     

Conceptual Evaluation of Factors Potentially Affecting Restoration of Habitat Structure within the Channelized Kissimmee River Ecosystem

A critical element of the ongoing effort to restore the ecological integrity of Florida's Kissimmee River ecosystem is the reestablishment of pre-channelization habitat structure and function. Restoration of habitat will form the basis for responses by most biological components of the ecosystem and will provide a key indicator of the success of the restoration effort. This paper evaluates the relative importance of a range of abiotic and biotic habitat parameters in the existing and historic Kissimmee River ecosystem and provides a conceptual framework for predicting expected spatial and temporal responses of river and floodplain habitats to the restoration project. Among the ecological factors and process that influenced the development, dynamics, and maintenance of river and floodplain habitat structure, hydrology is expected to be of central importance in eliciting restoration responses in the Kissimmee River Ecosystem. Based on the assumption that the restoration plan will reestablish historic hydrologic characteristics, predictions are made of expected responses by geomorphic and vegetative components of the Kissimmee River's habitat structure. Recommendations are made regarding key habitat parameters requiring long term tracking and analysis and utilization of a geographic information system(GIS). A hierarchical habitat classification scheme is provided as a foundation for all components of the restoration evaluation program.     

淡水湖泊生态系统退化驱动因子及修复技术研究进展

目前我国多数淡水湖泊污染、退化问题非常严重,诸多修复技术也已初见成效。影响淡水湖泊生态系统退化的驱动因子众多,既有生物因素也有非生物因素,它们之间相互联系,相互作用,且作用机理错综复杂。首先介绍了淡水湖泊生态系统退化的含义及形式;其次,分析、总结了淡水湖泊生态系统退化的驱动因子,从退化的生态学完整性意义和退化修复的技术手段上看,淡水湖泊生态系统主要受物理、化学和生物三大驱动因子影响,且基本遵循"环境变化-驱动力-压力(阈值)-状态-响应"原理;再次,在厘清湖泊生态系统退化驱动原理的基础上,从淡水湖泊生态系统功能模块和湖泊生态系统修复实践经验总结的角度出发,构建了淡水湖泊生态系统修复模块技术体系,并就湖泊富营养化和湖滨湿地生态系统退化修复的技术进行了讨论和对比;最后,对淡水湖泊生态系统修复的环境变化驱动因子的作用机制、作用途径和修复技术的长效机制等方面进行了展望。     

A conceptual model of climate-related effects on lake ecosystems

Climatic variation and change affect the dynamics of organisms and ecosystem processes. Many studies in the past have analyzed and discussed various climate-driven effects on different components of the lake ecosystem. Only a few synthesis papers have been published in this field. In this overview, a conceptual model has been developed to help explain why lakes respond individually to climate. The model consists of two main components, a so-called Landscape Filter comprising the features of geographical position, catchment characteristics and lake morphology, and a so-called Internal Lake Filter, comprising the features of lake history and biotic/abiotic interactions. The application of this conceptual model on published literature findings illustrates the strength in this encompassing perspective. An assessment of current climate research methods is presented with some perspectives given.     

Alternative states and positive feedbacks in restoration ecology

There is increasing interest in developing better predictive tools and a broader conceptual framework to guide the restoration of degraded land. Traditionally, restoration efforts have focused on re-establishing historical disturbance regimes or abiotic conditions, relying on successional processes to guide the recovery of biotic communities. However, strong feedbacks between biotic factors and the physical environment can alter the efficacy of these successional-based management efforts. Recent experimental work indicates that some degraded systems are resilient to traditional restoration efforts owing to constraints such as changes in landscape connectivity and organization, loss of native species pools, shifts in species dominance, trophic interactions and/or invasion by exotics, and concomitant effects on biogeochemical processes. Models of alternative ecosystem states that incorporate system thresholds and feedbacks are now being applied to the dynamics of recovery in degraded systems and are suggesting ways in which restoration can identify, prioritize and address these constraints.     

An Ecosystem View of the Restoration of the Kissimmee River

Restoration of the Kissimmee River and floodplain ultimately will involve restoring 70 km of river channel and riparian zone and 11,000 ha of wetland over a period of two decades. Restoring ecosystem integrity is a crucial goal of the project, and the evaluation program is designed to assess the success of this endeavor. Major components of the riverine and floodplain ecosystem will be evaluated, guided by conceptual models of their structure and function. These studies will be referenced to historic conditions of the past and to present-day conditions in the channelized system. Enhanced connectivity and interactions between the river and floodplain, the interplay of abiotic and biotic variables, and interactions between trophic levels will restructure the channelized river and the largely drained floodplain that now exist. The key to evaluating the success of this ambitious project will be selecting measurements of the structure and function of the river and floodplain ecosystems that are responsive to this large-scale manipulation. The timing and duration of floodplain inundation, improved dissolved oxygen conditions, germination and establishment of wetland vegetation, and enhancement and expansion of rheophilic benthic invertebrate populations are critical initial elements of restoration. Further expected outcomes are an increase in the primary productivity of the ecosystem, expansion of the fish community into the reopened channels and onto the reflooded floodplain, and improved visitation and use by waterbirds in the restored regions. We highlight predictions of some of these key linkages and primary structural and functional attributes of the restored river and floodplain that should be measured.     

Measuring progress in status of land under forest landscape restoration using abiotic and biotic indicators

The paper suggests a minimum set of abiotic and biotic threshold indicators and progress indicators for forest landscape restoration (FLR), then also briefly discusses progress indicators of pressures and project outputs. FLR aims to restore multiple functions of forests at a landscape scale. It is predicated on the hypothesis that restoration produces enabling conditions for ecosystem services, including regulating services such as carbon sequestration and pollination, and provisioning services such as food and energy. As FLR gains greater uptake, it is increasingly important to monitor progress. The types of indicators required are influenced by the degree of forest loss and degradation. To measure the status of land under restoration, one or more abiotic and biotic threshold indicators are required, measuring the return of enabling conditions for restoration (soil quality, water, etc.), along with progress indicators measuring the reemergence of the ecosystem services. Although all elements of the proposed monitoring framework are well known, compiling them into a coherent system, suitable for application in a wide range of conditions, will take much further development.     

The Power of Regeneration: Lessons from a Degraded Grassland

To gain insight into mechanisms controlling ecosystem regeneration, we investigated a grassland that was heavily polluted by a phosphate fertilizer factory between 1960 and 1990. Abiotic and biotic filters that influenced species assemblage and succession were monitored and restoration approaches assessed. Studies included the investigation of soil parameters, impact of abiotic stress on microbes and plants, plant succession, recolonization mechanisms, functional group interactions, mycorrhizal diversity and function, and food web analysis. Results indicate that after cessation of pollution, the system had high potential for self‐recovery. About 15 years of research are now summarized by interrelating the results of all projects and fitting them into one conceptual model.     

Three-Dimensional Framework of Vigor,Organization, and Resilience (VOR) for Assessing Rangeland Health: A Case Study from the Alpine Meadow of the Qinghai-Tibetan Plateau,China

Rangeland health assessments play an important role in providing qualitative and quantitative data about ecosystem attributes and rangeland management. The objective of this study is to test the feasible of a modified model and visualize the health in a three-dimensional model. A modified Costanza model was employed, and eight indicators, including the biomass, biodiversity, and carrying capacity [associated with the vigor, organization, and resilience (VOR)] were applied. An entropy method was also developed to calculate the weight of each indicator, and a three-dimensional framework was applied to visualize the indicators and health index. The conceptual model was demonstrated using data from a case study on the alpine rangeland of the Qinghai-Tibetan Plateau, one of the globally important grassland biomes being severely degraded by natural and human factors. The health indices of four grassland plots at different levels of degradation were calculated using a modified approach to measuring their VOR. The results indicated that the least disturbed plot was relatively healthy compared to the other plots. In addition, the health indices presented in the three-dimensional VOR framework decreased in a consistent manner across the four plots along the disturbance gradients. Such rangeland health assessments should be integrated with management efforts to insure their long-term sustainable use.     

藏北高寒草地生态补偿机制与方案

根据藏北那曲高寒草地的生产力、季节放牧重要性、生态服务价值、生态环境敏感性,构建了基于草地亚类的功能分区模型,从空间上将高寒草地划分为适度生产功能区、减畜恢复功能区和禁牧封育功能区,据此构建了基于高寒草地功能分区的分级生态补偿模式,设计了高寒草地生态补偿的组织管理体系及流程、生态补偿的损益评估机制和约束奖惩机制;提出了针对不同功能区的生态补偿方案.根据藏北那曲高寒草地功能分区结果和不同功能区生态补偿内容和目标,确定生态补偿周期为5a,核算出适度生产功能区、减畜恢复功能区和禁牧封育保护功能区分别需要补偿资金19.4亿元、15.77亿元和0.6亿元,每年分别需补偿资金3.88亿元、3.16亿元和0.12亿元,5a全区共需补偿资金35.77亿元,年需7.16亿元.通过对高寒草地的功能分区分级生态补偿,对提高高寒草地的生态保护能力,增加牧民的经济收入,促进藏北高寒草地生态系统的可持续发展具有重要的理论和实践意义.     

Plant community and soil available nutrients drive arbuscular mycorrhizal fungal community shifts during alpine meadow degradation

Arbuscular mycorrhizal fungi (AMF) play an important role in maintaining the function and sustainability of grassland ecosystem, but they are also susceptible to environmental changes. In recent decades, alpine meadows on the Tibetan Plateau have experienced severe degradation due to the impact of human activities and climate change. But it remains unclear how degradation affects the AMF community, a group of functionally important root associated microorganisms, which potentially limit the development and application of microbial technologies in the restoration of degraded grasslands. In this study, we investigated AMF communities richness and composition in non-degraded (ND), moderately degraded (MD) and severely degraded (SD) alpine meadows on the Tibetan Plateau, and then explored their main biotic and abiotic determinants. Alpine meadow degradation significantly reduced plant community biomass, richness, soil organic carbon, total nitrogen, total phosphorus, available nitrogen and available phosphorus, but increased soil pH. AMF community composition and the iesdominant family and genera differed significantly among different degradation stages. Grassland degradation shifted the AMF community composition in favor of Claroideoglomus over Rhizophagus, and resulted in a marked loss of Glomeraceae and the dominance of Diversisporaceae. Alpine meadow degradation significantly increased AMF hyphal density and richness, likely working as a plant strategy to relieve nutrient deficiencies or loss as a result of degradation. The structural equation model showed that AMF community richness and composition were significantly influenced by plant community, followed by soil available nutrients. Soil available nutrients was the key contributor to the increased AMF hyphal density and richness during grassland degradation. Our findings identify the effects of alpine meadow degradation on AMF richness and highlight the importance of the plant community in shaping the AMF community during alpine meadow degradation. These results suggest that plant community restoration should be the primary goal for the ecological restoration of degraded alpine meadows, and these soil functional microorganisms should be simultaneously integrated into ecological restoration strategies and management.     

Restoration Ecology: Repairing the Earth's Ecosystems in the New Millennium

The extent of human‐induced change and damage to Earth's ecosystems renders ecosystem repair an essential part of our future survival strategy, and this demands that restoration ecology provide effective conceptual and practical tools for this task. We argue that restoration ecology has to be an integral component of land management in today's world, and to be broadly applicable, has to have a clearly articulated conceptual basis. This needs to recognize that most ecosystems are dynamic and hence restoration goals cannot be based on static attributes. Setting clear and achievable goals is essential, and these should focus on the desired characteristics for the system in the future, rather than in relation to what these were in the past. Goal setting requires that there is a clear understanding of the restoration options available (and the relative costs of different options). The concept of restoration thresholds suggests that options are determined by the current state of the system in relation to biotic and abiotic thresholds. A further important task is the development of effective and easily measured success criteria. Many parameters could be considered for inclusion in restoration success criteria, but these are often ambiguous or hard to measure. Success criteria need to relate clearly back to specific restoration goals. If restoration ecology is to be successfully practiced as part of humanity's response to continued ecosystem change and degradation, restoration ecologists need to rise to the challenges of meshing science, practice and policy. Restoration ecology is likely to be one of the most important fields of the coming century.     

生态系统退化程度诊断：生态恢复的基础与前提

 生态系统退化程度诊断是进行生态恢复与重建的基础和前提。然而目前的生态系统化程度诊断大多停留在定性的水平,如何对退化生态系统的退化程度进行定量的诊断就成为恢复生态学与生态恢复实践所面临的一个迫切且十分关键的问题。在综述前人研究的基础上,比较系统地论述了生态系统退化程度诊断的一系列问题：绘制了描述生态系统退化程度的概念模型;认为在实践中退化程度诊断的参照系统可以选择相应的受人类或自然干扰程度比较轻的“自然生态系统”;归纳了生态系统退化程度诊断的生物途径、生境途径、生态过程途径、生态系统功能/服务途径、景观途径;把诊断方法分为单途径单因子诊断法、单途径多因子诊断法、多途径综合诊断法;分析了生态系统退化程度诊断的可能指标（体系）;给出了生态系统退化程度诊断的策略与流程,并对生态系统退化程度诊断及生态恢复过程中应注意的事项进行了讨论。建议我国加强典型生态系统退化程度的综合诊断研究。     

Trait‐based ecology of terrestrial arthropods

In focusing on how organisms' generalizable functional properties (traits) interact mechanistically with environments across spatial scales and levels of biological organization, trait‐based approaches provide a powerful framework for attaining synthesis, generality and prediction. Trait‐based research has considerably improved understanding of the assembly, structure and functioning of plant communities. Further advances in ecology may be achieved by exploring the trait–environment relationships of non‐sessile, heterotrophic organisms such as terrestrial arthropods, which are geographically ubiquitous, ecologically diverse, and often important functional components of ecosystems. Trait‐based studies and trait databases have recently been compiled for groups such as ants, bees, beetles, butterflies, spiders and many others; however, the explicit justification, conceptual framework, and primary‐evidence base for the burgeoning field of ‘terrestrial arthropod trait‐based ecology’ have not been well established. Consequently, there is some confusion over the scope and relevance of this field, as well as a tendency for studies to overlook important assumptions of the trait‐based approach. Here we aim to provide a broad and accessible overview of the trait‐based ecology of terrestrial arthropods. We first define and illustrate foundational concepts in trait‐based ecology with respect to terrestrial arthropods, and justify the application of trait‐based approaches to the study of their ecology. Next, we review studies in community ecology where trait‐based approaches have been used to elucidate how assembly processes for terrestrial arthropod communities are influenced by niche filtering along environmental gradients (e.g. climatic, structural, and land‐use gradients) and by abiotic and biotic disturbances (e.g. fire, floods, and biological invasions). We also review studies in ecosystem ecology where trait‐based approaches have been used to investigate biodiversity–ecosystem function relationships: how the functional diversity of arthropod communities relates to a host of ecosystem functions and services that they mediate, such as decomposition, pollination and predation. We then suggest how future work can address fundamental assumptions and limitations by investigating trait functionality and the effects of intraspecific variation, assessing the potential for sampling methods to bias the traits and trait values observed, and enhancing the quality and consolidation of trait information in databases. A roadmap to guide observational trait‐based studies is also presented. Lastly, we highlight new areas where trait‐based studies on terrestrial arthropods are well positioned to advance ecological understanding and application. These include examining the roles of competitive, non‐competitive and (multi‐)trophic interactions in shaping coexistence, and macro‐scaling trait–environment relationships to explain and predict patterns in biodiversity and ecosystem functions across space and time. We hope this review will spur and guide future applications of the trait‐based framework to advance ecological insights from the most diverse eukaryotic organisms on Earth.     

Trophic-dynamic considerations in relating species diversity to ecosystem resilience

Complexity in the networks of interactions among and between the living and abiotic components forming ecosystems confounds the ability of ecologists to predict the economic consequences of perturbations such as species deletions in nature. Such uncertainty hampers prudent decision making about where and when to invest most intensively in species conservation programmes. Demystifying ecosystem responses to biodiversity alterations may be best achieved through the study of the interactions allowing biotic communities to compensate internally for population changes in terms of contributing to ecosystem function, or their intrinsic functional redundancy. Because individual organisms are the biologically discrete working components of ecosystems and because environmental changes are perceived at the scale of the individual, a mechanistic understanding of functional redundancy will hinge upon understanding how individuals' behaviours influence population dynamics in the complex community setting. Here, I use analytical and graphical modelling to construct a conceptual framework for predicting the conditions under which varying degrees of interspecific functional redundancy can be found in dynamic ecosystems. The framework is founded on principles related to food web successional theory, which provides some evolutionary insights for mechanistically linking functional roles of discrete, interacting organisms with the dynamics of ecosystems because energy is the currency both for ecological fitness and for food web commerce. Net productivity is considered the most contextually relevant ecosystem process variable because of its socioeconomic significance and because it ultimately subsumes all biological processes and interactions. Redundancy relative to productivity is suggested to manifest most directly as compensatory niche shifts among adaptive foragers in exploitation ecosystems, facilitating coexistence and enhancing ecosystem recovery after disturbances which alter species' relative abundances, such as extinctions. The framework further explicates how resource scarcity and environmental stochasticity may constitute 'ecosystem legacies' influencing the emergence of redundancy by shaping the background conditions for foraging behaviour evolution and, consequently, the prevalence of compensatory interactions. Because it generates experimentally testable predictions for a priori hypothesis testing about when and where varying degrees of functional redundancy are likely to be found in food webs, the framework may be useful for advancing toward the reliable knowledge of biodiversity and ecosystem function relations necessary for prudent prioritization of conservation programmes. The theory presented here introduces explanation of how increasing diversity can have a negative influence on ecosystem sustainability by altering the environment for biotic interactions and thereby changing functional compensability among biota--under particular conditions.