A conceptual ecological model to facilitate understanding the role of invasive species in large-scale ecosystem restoration

We developed a conceptual ecological model (CEM) for invasive species to help understand the role invasive exotics have in ecosystem ecology and their impacts on restoration activities. Our model, which can be applied to any invasive species, grew from the eco-regional conceptual models developed for Everglades restoration. These models identify ecological drivers, stressors, effects and attributes; we integrated the unique aspects of exotic species invasions and effects into this conceptual hierarchy. We used the model to help identify important aspects of invasion in the development of an invasive exotic plant ecological indicator, which is described a companion paper in this special issue journal. A key aspect of the CEM is that it is a general ecological model that can be tailored to specific cases and species, as the details of any invasion are unique to that invasive species. Our model encompasses the temporal and spatial changes that characterize invasion, identifying the general conditions that allow a species to become invasive in a de novo environment; it then enumerates the possible effects exotic species may have collectively and individually at varying scales and for different ecosystem properties, once a species becomes invasive. The model provides suites of characteristics and processes, as well as hypothesized causal relationships to consider when thinking about the effects or potential effects of an invasive exotic and how restoration efforts will affect these characteristics and processes. In order to illustrate how to use the model as a blueprint for applying a similar approach to other invasive species and ecosystems, we give two examples of using this conceptual model to evaluate the status of two south Florida invasive exotic plant species (melaleuca and Old World climbing fern) and consider potential impacts of these invasive species on restoration.

Alligators and crocodiles as indicators for restoration of Everglades ecosystems

Alligators and crocodiles integrate biological impacts of hydrological operations, affecting them at all life stages through three key aspects of Everglades ecology: (1) food webs, (2) diversity and productivity, and (3) freshwater flow. Responses of crocodilians are directly related to suitability of environmental conditions and hydrologic change. Correlations between biological responses and environmental conditions contribute to an understanding of species’ status and trends over time. Positive or negative trends of crocodilian populations relative to hydrologic changes permit assessment of positive or negative trends in restoration. The crocodilian indicator uses monitoring parameters (performance measures) that have been shown to be both effective and efficient in tracking trends. The alligator component uses relative density (reported as an encounter rate), body condition, and occupancy rates of alligator holes; the crocodile component uses juvenile growth and hatchling survival. We hypothesize that these parameters are correlated with hydrologic conditions including depth, duration, timing, spatial extent and water quality. Salinity is a critical parameter in estuarine habitats. Assessments of parameters defined for crocodilian performance measures support these hypotheses. Alligators and crocodiles are the charismatic megafauna of the Everglades. They are both keystone and flagship species to which the public can relate. In addition, the parameters used to track trends are easy to understand. They provide answers to the following questions: How has the number of alligators or crocodiles changed? Are the animals fatter or thinner than they should be? Are the animals in the places (in terms of habitat and geography) where they should be? As surely as there is no other Everglades, no other single species defines the Everglades as does the American alligator. The Everglades is the only place in the world where both alligators and crocodiles exist. Crocodilians clearly respond to changes in hydrologic parameters of management interest. These relationships are easy to communicate and mean something to managers, decision makers, and the public. Having crocodilians on the list of system-wide, general indicators provides us with one of the most powerful tools we have to communicate progress of ecosystem restoration in Greater Everglades ecosystems to diverse audiences.

Factors influencing movements and foraging ecology of American alligators (Alligator mississippiensis) in a dynamic subtropical coastal ecosystem

Top predators can have large effects on community and population dynamics but we still know relatively little about their roles in ecosystems and which biotic and abiotic factors potentially affect their behavioral patterns. Understanding the roles played by top predators is a pressing issue because many top predator populations around the world are declining rapidly yet we do not fully understand what the consequences of their potential extirpation could be for ecosystem structure and function. In addition, individual behavioral specialization is commonplace across many taxa, but studies of its prevalence, causes, and consequences in top predator populations are lacking. In this dissertation I investigated the movement, feeding patterns, and drivers and implications of individual specialization in an American alligator (Alligator mississippiensis ) population inhabiting a dynamic subtropical estuary. I found that alligator movement and feeding behaviors in this population were largely regulated by a combination of biotic and abiotic factors that varied seasonally. I also found that the population consisted of individuals that displayed an extremely wide range of movement and feeding behaviors, indicating that individual specialization is potentially an important determinant of the varied roles of alligators in ecosystems. Ultimately, I found that assuming top predator populations consist of individuals that all behave in similar ways in terms of their feeding, movements, and potential roles in ecosystems is likely incorrect. As climate change and ecosystem restoration and conservation activities continue to affect top predator populations worldwide, individuals will likely respond in different and possibly unexpected ways.

Evaluating Effects of Everglades Restoration on American Crocodile Populations in South Florida Using a Spatially-Explicit, Stage-Based Population Model

The distribution and abundance of the American crocodile (Crocodylus acutus) in the Florida Everglades is dependent on the timing, amount, and location of freshwater flow. One of the goals of the Comprehensive Everglades Restoration Plan (CERP) is to restore historic freshwater flows to American crocodile habitat throughout the Everglades. To predict the impacts on the crocodile population from planned restoration activities, we created a stage-based spatially explicit crocodile population model that incorporated regional hydrology models and American crocodile research and monitoring data. Growth and survival were influenced by salinity, water depth, and density-dependent interactions. A stage-structured spatial model was used with discrete spatial convolution to direct crocodiles toward attractive sources where conditions were favorable. The model predicted that CERP would have both positive and negative impacts on American crocodile growth, survival, and distribution. Overall, crocodile populations across south Florida were predicted to decrease approximately 3 % with the implementation of CERP compared to future conditions without restoration, but local increases up to 30 % occurred in the Joe Bay area near Taylor Slough, and local decreases up to 30 % occurred in the vicinity of Buttonwood Canal due to changes in salinity and freshwater flows.

Density-Dependent Effects of Coral Reef Restoration on Herbivory and Community Interactions

Coral reefs are among the most productive ecosystems in the world. Yet, with their recent declines due to disease, climate change, and overfishing, restoration of these habitats is one of the main concerns for ecologists, resource managers, and government organizations. Coral reef restoration aims to promote key ecosystem processes to shift these habitats to their historical state of high coral cover, but few studies have focused on effective ways to promote resilience. In addition, little is known about the impact of restoration on the fish communities. The aim of this study is to understand how the community of herbivorous fishes is affected by the density of coral outplants inside a special protection area located in the Florida Keys National Marine Sanctuary. Grazing rates, number of visits and time spent foraging were compared using video footage of sites previously devoid of corals, and six months after coral restorations had occurred. Coral transplantations did not appear to attract herbivores nor increase grazing rates of fishes. Instead Sparisoma and Acanthurus fishes appear to respond to changes in the environment by modifying their grazing behavior. However, there was an observed increase in visits by Acanthurus species after transplantation for all the sites sampled within the reef. These fishes seemed to prefer low coral cover sites for grazing. This study highlights the importance of examining coral restorations impacts at the community level. Understanding how restoration influences herbivores and other guilds of reef fishes will allow individuals to not only determine if these habitats are returning to their “original” state, but provide more information on the ways these systems cope with changes in the environment.

Biodiversity offsetting and restoration under the European Union Habitats Directive: balancing between no net loss and deathbed conservation?

Biodiversity offsets have emerged as one of the most prominent policy approaches to align economic development with nature protection across many jurisdictions, including the European Union. Given the increased level of scrutiny that needs to be applied when authorizing economic developments near protected Natura 2000 sites, the incorporation of onsite biodiversity offsets in project design has grown increasingly popular in some member states, such as the Netherlands and Belgium. Under this approach, the negative effects of developments are outbalanced by restoration programs that are functionally linked to the infrastructure projects. However, although taking into consideration that the positive effects of onsite restoration measures leads to more leeway for harmful project development, the EU Court of Justice has recently dismissed the latter approaches for going against the preventative underpinnings of the EU Habitats Directive. Also, the expected beneficial outcomes of the restoration efforts are uncertain and thus cannot be relied upon in an ecological assessment under Article 6(3) of the Habitats Directive. Although biodiversity offsets can still be relied upon whenever application is being made of the derogation clause under Article 6(4) of the Habitats Directive, they cannot be used as mitigation under the generic decision-making process for plans and programs liable to adversely affect Natura 2000 sites. We outline the main arguments pro and contra the stance of the EU Court of Justice with regards to the exact delineation between mitigation and compensation. The analysis is also framed in the ongoing debate on the effectiveness of the EU nature directives. Although ostensibly rigid, it is argued that the recent case-law developments are in line with the main principles underpinning biodiversity offsetting. Opening the door for biodiversity offsetting under the Habitats Directive will certainly not reverse the predicament of the EU’s biodiversity. A reinforcement of the preventative approach is instrumental to avert a further biodiversity loss within the European Union, even if it will lead to additional permit refusals for unsustainable project developments.

Creating restoration landscapes: partnerships in large-scale conservation in the UK

It is increasingly recognized that ecological restoration demands conservation action beyond the borders of existing protected areas. This requires the coordination of land uses and management over a larger area, usually with a range of partners, which presents novel institutional challenges for conservation planners. Interviews were undertaken with managers of a purposive sample of large-scale conservation areas in the UK. Interviews were open-ended and analyzed using standard qualitative methods. Results show a wide variety of organizations are involved in large-scale conservation projects, and that partnerships take time to create and demand resilience in the face of different organizational practices, staff turnover, and short-term funding. Successful partnerships with local communities depend on the establishment of trust and the availability of external funds to support conservation land uses. We conclude that there is no single institutional model for large-scale conservation: success depends on finding institutional strategies that secure long-term conservation outcomes, and ensure that conservation gains are not reversed when funding runs out, private owners change priorities, or land changes hands.

An appraisal of adaptive management planning and implementation in ecological restoration: case studies from the San Francisco Bay Delta, USA

Adaptive management has been defined and redefined in the context of natural resource management, yet there are few examples of its successful application in ecological restoration. Although the 2009 Delta Reform Act now legally requires adaptive management for all restoration efforts in the Sacramento-San Joaquin Delta, in California, USA, projects in this region still encounter problems with implementation. We used a comparative case study analysis to examine adaptive management planning and implementation both in and around the Delta, assessing not only why adaptive management is not yet well implemented, but also what changes can be made to facilitate the adaptive management approach without sacrificing scientific rigor. Adaptive management seems to be directly and indirectly affected by a variety of challenges and convoluted by ambiguity in both planning documents and practitioner’s interpretations of the concept. Addressing these challenges and ambiguities at the project level may facilitate the adaptive management process and help make it more accessible to practitioners.

Long-term fish community response to a reach-scale stream restoration

At a global scale, aquatic ecosystems are being altered by human activities at a greater rate than at any other time in history. In recent years, grassroots efforts have generated interest in the restoration of degraded or destroyed aquatic habitats, especially small wetlands and streams where such projects are feasible with local resources. We present ecological management lessons learned from 17 years of monitoring the fish community response to the channel relocation and reach-level restoration of Juday Creek, a 3rd-order tributary of the St. Joseph River in Indiana, USA. The project was designed to increase habitat complexity, reverse the effects of accumulated fine sediment (< 2 mm diameter), and mitigate for the impacts of a new golf course development. The 1997 restoration consisted of new channel construction within two reaches of a 1.2-km section of Juday Creek that also contained two control reaches. A primary social goal of the golf course development and stream restoration was to avoid harm to the non-native brown trout fishery, as symbolic of community concerns for the watershed. Our long-term monitoring effort revealed that, although fine sediment increased over time in the restored reaches, habitat conditions have promoted the resurgence of native fish species. Since restoration, the fish assemblage has shifted from non-native Salmonidae (brown trout, rainbow trout) to native Centrarchidae (rock bass, largemouth bass, smallmouth bass). In addition, native, nongame species have remained stable or have increased in population abundance (e.g., Johnny darter, mottled sculpin). The results of this study demonstrate the value of learning from a restoration project to adjust management decisions that enhance environmental quality.

The challenges of integrating biodiversity and ecosystem services monitoring and evaluation at a landscape-scale wetland restoration project in the UK

There is an increasing emphasis on the restoration of ecosystem services as well as of biodiversity, especially where restoration projects are planned at a landscape scale. This increase in the diversity of restoration aims has a number of conceptual and practical implications for the way that restoration projects are monitored and evaluated. Landscape-scale projects require monitoring of not only ecosystem services and biodiversity but also of ecosystem processes since these can underpin both. Using the experiences gained at a landscape-scale wetland restoration project in the UK, we discuss a number of issues that need to be considered, including the choice of metrics for monitoring ecosystem services and the difficulties of assessing the interactions between ecosystem processes, biodiversity, and ecosystem services. Particular challenges that we identify, using two pilot data sets, include the decoupling of monetary metrics used for monitoring ecosystem services from biophysical change on the ground and the wide range of factors external to a project that influence the monitoring results. We highlight the fact that the wide range of metrics necessary to evaluate the ecosystem service, ecosystem process, and biodiversity outcomes of landscape-scale projects presents a number of practical challenges, including the need for high levels of varied expertise, high costs, incommensurate monitoring outputs, and the need for careful management of monitoring results, especially where they may be used in making decisions about the relative importance of project aims.

Sociocultural Complexities of Ecosystem Restoration: Remaking Identity, Landscape and Belonging in the Florida Everglades

The Florida Everglades is a highly diverse socionatural landscape that historically spanned much of the south Florida peninsula. Today, the Florida Everglades is an iconic but highly contested conservation landscape. It is the site of one of the world’s largest publicly funded ecological restoration programs, estimated to cost over $8 billion (U.S. GAO 2007), and it is home to over two million acres of federally protected lands, including the Big Cypress National Preserve and Everglades National Park. However, local people’s values, practices and histories overlap and often conflict with the global and eco-centric values linked to Everglades environmental conservation efforts, sparking environmental conflict. My dissertation research examined the cultural politics of nature associated with two Everglades conservation and ecological restoration projects: 1) the creation and stewardship of the Big Cypress National Preserve, and 2) the Tamiami Trail project at the northern boundary of Everglades National Park. Using multiple research methods including ethnographic fieldwork, archival research, participant observation, surveys and semi-structured interviews, I documented how these two projects have shaped environmental claims-making strategies to Everglades nature on the part of environmental NGOs, the National Park Service and local white outdoorsmen. In particular, I examined the emergence of an oppositional white identity called the Gladesmen Culture. My findings include the following: 1) just as different forms of nature are historically produced, contingent and power-laden, so too are different claims to Everglades nature; 2) identity politics are an integral dimension of Everglades environmental conflicts; and 3) the Big Cypress region’s history and contemporary conflicts are shaped by the broader political economy of development in south Florida. My dissertation concluded that identity politics, class and property relations have played a key, although not always obvious, role in shaping Everglades history and environmental claims-making, and that they continue to influence contemporary Everglades environmental conflicts.

Factors Influencing Movements and Foraging Ecology of American Alligators (Alligator mississippiensis) in a Dynamic Subtropical Coastal Ecosystem

Top predators can have large effects on community and population dynamics but we still know relatively little about their roles in ecosystems and which biotic and abiotic factors potentially affect their behavioral patterns. Understanding the roles played by top predators is a pressing issue because many top predator populations around the world are declining rapidly yet we do not fully understand what the consequences of their potential extirpation could be for ecosystem structure and function. In addition, individual behavioral specialization is commonplace across many taxa, but studies of its prevalence, causes, and consequences in top predator populations are lacking. In this dissertation I investigated the movement, feeding patterns, and drivers and implications of individual specialization in an American alligator (Alligator mississippiensis) population inhabiting a dynamic subtropical estuary. I found that alligator movement and feeding behaviors in this population were largely regulated by a combination of biotic and abiotic factors that varied seasonally. I also found that the population consisted of individuals that displayed an extremely wide range of movement and feeding behaviors, indicating that individual specialization is potentially an important determinant of the varied roles of alligators in ecosystems. Ultimately, I found that assuming top predator populations consist of individuals that all behave in similar ways in terms of their feeding, movements, and potential roles in ecosystems is likely incorrect. As climate change and ecosystem restoration and conservation activities continue to affect top predator populations worldwide, individuals will likely respond in different and possibly unexpected ways.

Population ecology of the sea lamprey (Petromyzon marinus) as an invasive species in the Laurentian Great Lakes and an imperiled species in Europe.

The sea lamprey Petromyzon marinus (Linnaeus) is both an invasive non-native species in the Laurentian Great Lakes of North America and an imperiled species in much of its native range in North America and Europe. To compare and contrast how understanding of population ecology is useful for control programs in the Great Lakes and restoration programs in Europe, we review current understanding of the population ecology of the sea lamprey in its native and introduced range. Some attributes of sea lamprey population ecology are particularly useful for both control programs in the Great Lakes and restoration programs in the native range. First, traps within fish ladders are beneficial for removing sea lampreys in Great Lakes streams and passing sea lampreys in the native range. Second, attractants and repellants are suitable for luring sea lampreys into traps for control in the Great Lakes and guiding sea lamprey passage for conservation in the native range. Third, assessment methods used for targeting sea lamprey control in the Great Lakes are useful for targeting habitat protection in the native range. Last, assessment methods used to quantify numbers of all life stages of sea lampreys would be appropriate for measuring success of control in the Great Lakes and success of conservation in the native range.

Using information criteria to select the correct variance–covariance structure for longitudinal data in ecology

1. Ecological data sets often use clustered measurements or use repeated sampling in a longitudinal design. Choosing the correct covariance structure is an important step in the analysis of such data, as the covariance describes the degree of similarity among the repeated observations. 2. Three methods for choosing the covariance are: the Akaike information criterion (AIC), the quasi-information criterion (QIC), and the deviance information criterion (DIC). We compared the methods using a simulation study and using a data set that explored effects of forest fragmentation on avian species richness over 15 years. 3. The overall success was 80.6% for the AIC, 29.4% for the QIC and 81.6% for the DIC. For the forest fragmentation study the AIC and DIC selected the unstructured covariance, whereas the QIC selected the simpler autoregressive covariance. Graphical diagnostics suggested that the unstructured covariance was probably correct. 4. We recommend using DIC for selecting the correct covariance structure.