High-integrity human intervention in ecosystems: Tracking self-organization modes

Humans play major roles in shaping and transforming the ecology of Earth. Unlike natural drivers of ecosystem change, which are erratic and unpredictable, human intervention in ecosystems generally involves planning and management, but often results in detrimental outcomes. Using model studies and aerial-image analysis, we argue that the design of a successful human intervention form calls for the identification of the self-organization modes that drive ecosystem change, and for studying their dynamics. We demonstrate this approach with two examples: grazing management in drought-prone ecosystems, and rehabilitation of degraded vegetation by water harvesting. We show that grazing can increase the resilience to droughts, rather than imposing an additional stress, if managed in a spatially non-uniform manner, and that fragmental restoration along contour bunds is more resilient than the common practice of continuous restoration in vegetation stripes. We conclude by discussing the need for additional studies of self-organization modes and their dynamics.     

Freshwater as shared between society and ecosystems: from divided approaches to integrated challenges

The paper has its focus on water's key functions behind ecosystem dynamics and the water-related balancing involved in a catchment-based ecosystem approach. A conceptual framework is being developed to address fundamental trade-offs between humans and ecosystems. This is done by paying attention to society's unavoidable landscape modifications and their unavoidable ecological effects mediated by water processes. Because the coevolution of societal and environmental processes indicates resonance rather than a cause-effect relationship, humanity will have to learn to live with change while securing ecosystem resilience. In view of the partial incompatibility of the social imperative of the millennium goals and its environmental sustainability goal, human activities and ecosystems have to be orchestrated for compatibility. To this end a catchment-based approach has to be taken by integrating water, land use and ecosystems. It is being suggested that ecosystem protection has to be thought of in two scales: site-specific biotic landscape components to be protected for their social value, and a catchment-based ecosystem approach to secure sustainable supply of crucial ecosystem goods and services on which social and economic development depends.     

Are Existing Global Scenarios Consistent with Ecological Feedbacks?

Scenarios can help planners and decision makers to think through uncertainties about the future and make decisions that are robust to a variety of possible outcomes. To develop useful scenarios we need to understand the main processes of relevance to the system of interest. Ecological processes, and the feedbacks that they can create between human actions and human well-being, are thought to be important for human societies. Current uncertainties over the long-term resilience of ecosystems and the substitutability of ecosystem goods and services can be translated into three alternative realities: ecosystems may be relatively brittle, relatively resilient, or largely irrelevant. Although these extremes are only rough characterizations of reality, they help us to focus our thinking about the possible outcomes of interactions between humans and the rest of the biosphere. Existing global scenarios can be categorized into a small number of families based on shared themes and assumptions about the future. Considering the internal consistency of four of the main scenario families in relation to the three alternative ecological realities suggests that all existing scenarios make strong, implicit assumptions about the resilience of ecosystems. After a detailed discussion of individual examples, we present a synthesis of the incorporation of ecology in existing scenarios. All current scenarios are inconsistent with at least one possible property of ecosystems and their likely interaction with society. The interrelationships between ecological reality, human views of ecosystems, and social responses to actual and perceived ecological change are complex. For the Millennium Ecosystem Assessment and future scenario exercises, we recommend that essential ecological assumptions should be made explicit to ensure that the details of each scenario are consistent with both the perceived and the actual degree of resilience of ecosystems.     

Inferring the Relative Resilience of Alternative States

Ecological systems may occur in alternative states that differ in ecological structures, functions and processes. Resilience is the measure of disturbance an ecological system can absorb before changing states. However, how the intrinsic structures and processes of systems that characterize their states affects their resilience remains unclear. We analyzed time series of phytoplankton communities at three sites in a floodplain in central Spain to assess the dominant frequencies or “temporal scales” in community dynamics and compared the patterns between a wet and a dry alternative state. The identified frequencies and cross-scale structures are expected to arise from positive feedbacks that are thought to reinforce processes in alternative states of ecological systems and regulate emergent phenomena such as resilience. Our analyses show a higher species richness and diversity but lower evenness in the dry state. Time series modeling revealed a decrease in the importance of short-term variability in the communities, suggesting that community dynamics slowed down in the dry relative to the wet state. The number of temporal scales at which community dynamics manifested, and the explanatory power of time series models, was lower in the dry state. The higher diversity, reduced number of temporal scales and the lower explanatory power of time series models suggest that species dynamics tended to be more stochastic in the dry state. From a resilience perspective our results highlight a paradox: increasing species richness may not necessarily enhance resilience. The loss of cross-scale structure (i.e. the lower number of temporal scales) in community dynamics across sites suggests that resilience erodes during drought. Phytoplankton communities in the dry state are therefore likely less resilient than in the wet state. Our case study demonstrates the potential of time series modeling to assess attributes that mediate resilience. The approach is useful for assessing resilience of alternative states across ecological and other complex systems.     

New Directions for Understanding the Spatial Resilience of Social–Ecological Systems

The concept of spatial resilience has brought a new focus on the influence of multi-scale processes on the dynamics of ecosystems. Initial ideas about spatial resilience focused on coral reefs and emphasized escalating anthropogenic disturbances across the broader seascape. This perspective resonated with a new awareness of global drivers of change, such as growth in international trade and shifts in climate, and the need to respond by scaling up governance and management. We review recent trends and emerging ideas in spatial resilience, using coral reefs and dependent communities as exemplars of multi-scale social–ecological systems. Despite recent advances, management and governance of ecosystems remain spatially fragmented and constrained to small scales. Temporally, many interventions still miss or ignore warning signals and struggle to cope with history, politics, long-term cumulative pressures, feedbacks, and sudden surprises. Significant recent progress has been made in understanding the relevance of spatial and temporal scale, heterogeneity, networks, the importance of place, and multi-scale governance. Emerging themes include better integration of ecology and conservation with social and economic science, and incorporating temporal dynamics in spatial analyses. A better understanding of the multi-scale spatial and temporal processes that drive the resilience of linked social-ecosystems will help address the widespread mismatch between the scales of ongoing ecological change and effective long-term governance of land- and seascapes.     

Recent advances in ecosystem-atmosphere interactions: an ecological perspective

The atmosphere and terrestrial ecosystems are fundamentally coupled on a variety of time-scales. On short time-scales, this bi-directional interaction is dominated by the rapid exchange of CO(2), water and energy between the atmosphere and the land surface; on long time-scales, the interaction involves changes in ecosystem structure and composition in response to changes in climate that feed back through biophysical and biogeochemical mechanisms to influence climate over decades and centuries. After briefly describing some early pioneering work, I focus this review on recent advances in understanding long-term ecosystem-atmosphere interactions through a discussion of three case studies. I then examine how efforts to assess the stability and resilience of ecosystem-atmosphere interactions over these long time-scales using Dynamic Global Vegetation Models are hampered by the presence of important functional diversity and heterogeneity within plant communities. Recent work illustrates how this issue can be addressed through the use of Structured Ecosystem Models that more accurately scale between the short-term physiological responses of individual plants and the long-term, large-scale dynamics of heterogeneous, functionally diverse ecosystems.     

Assessment of ecosystem resilience to hydroclimatic disturbances in India

Recent studies have shown an increasing trend in hydroclimatic disturbances like droughts, which are anticipated to become more frequent and intense under global warming and climate change. Droughts adversely affect the vegetation growth and crop yield, which enhances the risks to food security for a country like India with over 1.2 billion people to feed. Here, we compared the response of terrestrial net primary productivity (NPP) to hydroclimatic disturbances in India at different scales (i.e., at river basins, land covers, and climate types) to examine the ecosystems’ resilience to such adverse conditions. The ecosystem water use efficiency (WUE_e: NPP/Evapotranspiration) is an effective indicator of ecosystem productivity, linking carbon (C) and water cycles. We found a significant difference (p < .05) in WUE_e across India at different scales. The ecosystem resilience analysis indicated that most of the river basins were not resilient enough to hydroclimatic disturbances. Drastic reduction in WUE_e under dry conditions was observed for some basins, which highlighted the cross‐biome incapability to withstand such conditions. The ecosystem resilience at land cover and climate type scale did not completely relate to the basin‐scale ecosystem resilience, which indicated that ecosystem resilience at basin scale is controlled by some other ecohydrological processes. Our results facilitate the identification of the most sensitive regions in the country for ecosystem management and climate policy making, and highlight the need for taking sufficient adaptation measures to ensure sustainability of ecosystems.     

基于传统生态智慧的江南水网空间韧性机制及实践启示

传统江南水网空间是一种典型的社会—生态系统,人文社会系统和自然生态系统之间的良性互动对于其韧性构建有着重要的积极作用。基于柯林斯等人提出的压力—冲击动态（PPD）模型,以平江府为典型代表,研究传统江南水网空间如何通过生态系统服务的桥梁搭建水网物质空间与人类社区发展之间的联系,从而厘清社会—生态系统在此过程中如何培育、优化和提升江南水网空间韧性。在此基础上,创新性地从生态系统服务供需关系的角度提出社会—生态韧性构建的生态智慧,并倡导以恢复力、适应力与变革力韧性机制培育为导向的、江南地区构建现代社区实践的若干启示,旨在引导江南水网空间实现具有韧性的社会—生态系统转型发展。     

Riverine landscape dynamics and ecological risk assessment

1. The aim of ecological risk assessments is to evaluate the likelihood that ecosystems are adversely affected by human‐induced disturbance that brings the ecosystem into a new dynamic equilibrium with a simpler structure and lower potential energy. The risk probability depends on the threshold capacity of the system (resistance) and on the capacity of the system to return to a state of equilibrium (resilience). 2. There are two complementary approaches to assessing ecological risks of riverine landscape dynamics. The reductionist approach aims at identifying risk to the ecosystem on the basis of accumulated data on simple stressor–effect relationships. The holistic approach aims at taking the whole ecosystem performance into account, which implies meso‐scale analysis. 3. Landscape patterns and their dynamics represent the physical framework of processes determining the ecosystem's equilibrium. Assessing risks of landscape dynamics to riverine ecosystems implies addressing complex interactions of system components (e.g. population dynamics and biogeochemical cycles) occurring at multiple scales of space and time. 4. One of the most important steps in ecological risk assessment is to establish clear assessment endpoints (e.g. vital ecosystem and landscape attributes). Their formulation must recognise that riverine ecosystems are dynamic, structurally complex and composed of both deterministic and stochastic components. 5. Remote sensing (geo)statistics and geographical information systems are primary tools for quantifying spatial and temporal components of riverine ecosystem and landscape attributes. 6. The difficulty to experiment at the riverine landscape level means that ecological risk management is heavily dependent on models. Current models are targeted towards simulating ecological risk at levels ranging from single species to habitats, food webs and meta‐populations to ecosystems and entire riverine landscapes, with some including socio‐economic considerations.     

Quantifying Climatological Ranges and Anomalies for Pacific Coral Reef Ecosystems

Coral reef ecosystems are exposed to a range of environmental forcings that vary on daily to decadal time scales and across spatial scales spanning from reefs to archipelagos. Environmental variability is a major determinant of reef ecosystem structure and function, including coral reef extent and growth rates, and the abundance, diversity, and morphology of reef organisms. Proper characterization of environmental forcings on coral reef ecosystems is critical if we are to understand the dynamics and implications of abiotic–biotic interactions on reef ecosystems. This study combines high-resolution bathymetric information with remotely sensed sea surface temperature, chlorophyll-a and irradiance data, and modeled wave data to quantify environmental forcings on coral reefs. We present a methodological approach to develop spatially constrained, island- and atoll-scale metrics that quantify climatological range limits and anomalous environmental forcings across U.S. Pacific coral reef ecosystems. Our results indicate considerable spatial heterogeneity in climatological ranges and anomalies across 41 islands and atolls, with emergent spatial patterns specific to each environmental forcing. For example, wave energy was greatest at northern latitudes and generally decreased with latitude. In contrast, chlorophyll-a was greatest at reef ecosystems proximate to the equator and northern-most locations, showing little synchrony with latitude. In addition, we find that the reef ecosystems with the highest chlorophyll-a concentrations; Jarvis, Howland, Baker, Palmyra and Kingman are each uninhabited and are characterized by high hard coral cover and large numbers of predatory fishes. Finally, we find that scaling environmental data to the spatial footprint of individual islands and atolls is more likely to capture local environmental forcings, as chlorophyll-a concentrations decreased at relatively short distances (>7 km) from 85% of our study locations. These metrics will help identify reef ecosystems most exposed to environmental stress as well as systems that may be more resistant or resilient to future climate change.     

Meta-ecosystems: a theoretical framework for a spatial ecosystem ecology

This contribution proposes the meta‐ecosystem concept as a natural extension of the metapopulation and metacommunity concepts. A meta‐ecosystem is defined as a set of ecosystems connected by spatial flows of energy, materials and organisms across ecosystem boundaries. This concept provides a powerful theoretical tool to understand the emergent properties that arise from spatial coupling of local ecosystems, such as global source–sink constraints, diversity–productivity patterns, stabilization of ecosystem processes and indirect interactions at landscape or regional scales. The meta‐ecosystem perspective thereby has the potential to integrate the perspectives of community and landscape ecology, to provide novel fundamental insights into the dynamics and functioning of ecosystems from local to global scales, and to increase our ability to predict the consequences of land‐use changes on biodiversity and the provision of ecosystem services to human societies.     

海湾生态韧性的陆海统筹测度与治理研究——基于厦门湾系统性视角

海岸带长期承受陆海生态风险的交互扰动,基于陆海统筹的系统性治理是提升其生态韧性的重要途径。海岸带生态管治条块分割的问题突出,生态系统具有相对独立性的海湾,作为陆海统筹的实施单元,为海岸带生态韧性测度与规划提供了新视角。在梳理海湾生态要素构成的基础上,分析陆海生态灾害诱因及其作用方式,进而厘清海湾生态系统的韧性响应机制。在陆海统筹目标下构建了海湾生态韧性测评指标体系,并以厦门湾为空间单元展开实例研究,采用相关模型剖析厦门湾陆域-海域生态韧性的耦合协调特征及演进驱动因子;聚焦厦门湾生态韧性薄弱之处,从构筑生态安全格局、分级整治韧性空间、联动管控韧性要素、建构跨界协同机制4个维度提出陆海统筹治理策略,以促进厦门湾生态系统可持续发展。该研究的理论建构及实践总结可为其他海湾单元生态文明建设提供参考。     

Conflict between dynamical and evolutionary stability in simple ecosystems

Here, we address the essential question of whether, in the context of evolving populations, ecosystems attain properties that enable persistence of the ecosystem itself. We use a simple ecosystem model describing resource, producer, and consumer dynamics to analyze how evolution affects dynamical stability properties of the ecosystem. In particular, we compare resilience of the entire system after allowing the producer and consumer populations to evolve to their evolutionarily stable strategy (ESS) to the maximum attainable resilience. We find a substantial reduction in ecosystem resilience when producers and consumers are allowed to evolve compared to the maximal attainable resilience. This study illustrates the inherent difference and possible conflict between maximizing individual-level fitness and maximizing resilience of entire ecosystems.     

Historical reconstruction reveals recovery in Hawaiian coral reefs

Coral reef ecosystems are declining worldwide, yet regional differences in the trajectories, timing and extent of degradation highlight the need for in-depth regional case studies to understand the factors that contribute to either ecosystem sustainability or decline. We reconstructed social-ecological interactions in Hawaiian coral reef environments over 700 years using detailed datasets on ecological conditions, proximate anthropogenic stressor regimes and social change. Here we report previously undetected recovery periods in Hawaiian coral reefs, including a historical recovery in the MHI (~AD 1400-1820) and an ongoing recovery in the NWHI (~AD 1950-2009+). These recovery periods appear to be attributed to a complex set of changes in underlying social systems, which served to release reefs from direct anthropogenic stressor regimes. Recovery at the ecosystem level is associated with reductions in stressors over long time periods (decades+) and large spatial scales (>10(3) km(2)). Our results challenge conventional assumptions and reported findings that human impacts to ecosystems are cumulative and lead only to long-term trajectories of environmental decline. In contrast, recovery periods reveal that human societies have interacted sustainably with coral reef environments over long time periods, and that degraded ecosystems may still retain the adaptive capacity and resilience to recover from human impacts.     

Differential responses of marine communities to natural and anthropogenic changes

Responses of ecosystems to environmental changes vary greatly across habitats, organisms and observational scales. The Quaternary fossil record of the Po Basin demonstrates that marine communities of the northern Adriatic re-emerged unchanged following the most recent glaciation, which lasted approximately 100 000 years. The Late Pleistocene and Holocene interglacial ecosystems were both dominated by the same species, species turnover rates approximated predictions of resampling models of a homogeneous system, and comparable bathymetric gradients in species composition, sample-level diversity, dominance and specimen abundance were observed in both time intervals. The interglacial Adriatic ecosystems appear to have been impervious to natural climate change either owing to their persistence during those long-term perturbations or their resilient recovery during interglacial phases of climate oscillations. By contrast, present-day communities of the northern Adriatic differ notably from their Holocene counterparts. The recent ecosystem shift stands in contrast to the long-term endurance of interglacial communities in face of climate-driven environmental changes.     

Resilience to Stress and Disturbance,and Resistance to Bromus tectorum L. Invasion in Cold Desert Shrublands of Western North America

Alien grass invasions in arid and semi-arid ecosystems are resulting in grass–fire cycles and ecosystem-level transformations that severely diminish ecosystem services. Our capacity to address the rapid and complex changes occurring in these ecosystems can be enhanced by developing an understanding of the environmental factors and ecosystem attributes that determine resilience of native ecosystems to stress and disturbance, and resistance to invasion. Cold desert shrublands occur over strong environmental gradients and exhibit significant differences in resilience and resistance. They provide an excellent opportunity to increase our understanding of these concepts. Herein, we examine a series of linked questions about (a) ecosystem attributes that determine resilience and resistance along environmental gradients, (b) effects of disturbances like livestock grazing and altered fire regimes and of stressors like rapid climate change, rising CO₂, and N deposition on resilience and resistance, and (c) interacting effects of resilience and resistance on ecosystems with different environmental conditions. We conclude by providing strategies for the use of resilience and resistance concepts in a management context. At ecological site scales, state and transition models are used to illustrate how differences in resilience and resistance influence potential alternative vegetation states, transitions among states, and thresholds. At landscape scales management strategies based on resilience and resistance—protection, prevention, restoration, and monitoring and adaptive management—are used to determine priority management areas and appropriate actions.     

Ecological Thresholds: The Key to Successful Environmental Management or an Important Concept with No Practical Application?

An ecological threshold is the point at which there is an abrupt change in an ecosystem quality, property or phenomenon, or where small changes in an environmental driver produce large responses in the ecosystem. Analysis of thresholds is complicated by nonlinear dynamics and by multiple factor controls that operate at diverse spatial and temporal scales. These complexities have challenged the use and utility of threshold concepts in environmental management despite great concern about preventing dramatic state changes in valued ecosystems, the need for determining critical pollutant loads and the ubiquity of other threshold-based environmental problems. In this paper we define the scope of the thresholds concept in ecological science and discuss methods for identifying and investigating thresholds using a variety of examples from terrestrial and aquatic environments, at ecosystem, landscape and regional scales. We end with a discussion of key research needs in this area.     

What is a healthy ecosystem?

Rapid deterioration of the world's major ecosystems has intensified the need for effective environmental monitoring and the development of operational indicators of ecosystem health. Ecosystem health represents a desired endpoint of environmental management, but it requires adaptive, ongoing definition and assessment. We propose that a healthy ecosystem is one that is sustainable – that is, it has the ability to maintain its structure (organization) and function (vigor) over time in the face of external stress (resilience). Various methods to quantify these three ecosystem attributes (vigor, organization, and resilience) are discussed. These attributes are then folded into a comprehensive assessment of ecosystem health. A network analysis based ecosystem health assessment is developed and tested using trophic exchange networks representing several different aquatic ecosystems. Results indicate the potential of such an ecosystem health assessment for evaluating the relative health of similar ecosystems, and quantifying the effects of natural or anthropogenic stress on the health of a particular ecosystem over time.     

Models of underlying autotrophic biomass dynamics fit to daily river ecosystem productivity estimates improve understanding of ecosystem disturbance and resilience

Directly observing autotrophic biomass at ecologically relevant frequencies is difficult in many ecosystems, hampering our ability to predict productivity through time. Since disturbances can impart distinct reductions in river productivity through time by modifying underlying standing stocks of biomass, mechanistic models fit to productivity time series can infer underlying biomass dynamics. We incorporated biomass dynamics into a river ecosystem productivity model for six rivers to identify disturbance flow thresholds and understand the resilience of primary producers. The magnitude of flood necessary to disturb biomass and thereby reduce ecosystem productivity was consistently lower than the more commonly used disturbance flow threshold of the flood magnitude necessary to mobilize river bed sediment. The estimated daily maximum percent increase in biomass (a proxy for resilience) ranged from 5% to 42% across rivers. Our latent biomass model improves understanding of disturbance thresholds and recovery patterns of autotrophic biomass within river ecosystems.