James Battin

Bio: James Battin is an academic researcher from Northern Arizona University. The author has contributed to research in topics: Habitat fragmentation & Habitat. The author has an hindex of 5, co-authored 7 publications receiving 2236 citations.

Ecological Responses to Habitat Edges: Mechanisms, Models, and Variability Explained

Abstract: ▪ Abstract Edge effects have been studied for decades because they are a key component to understanding how landscape structure influences habitat quality. However, making sense of the diverse patterns and extensive variability reported in the literature has been difficult because there has been no unifying conceptual framework to guide research. In this review, we identify four fundamental mechanisms that cause edge responses: ecological flows, access to spatially separated resources, resource mapping, and species interactions. We present a conceptual framework that identifies the pathways through which these four mechanisms can influence distributions, ultimately leading to new ecological communities near habitat edges. Next, we examine a predictive model of edge responses and show how it can explain much of the variation reported in the literature. Using this model, we show that, when observed, edge responses are largely predictable and consistent. When edge responses are variable for the same species ...

When Good Animals Love Bad Habitats: Ecological Traps and the Conservation of Animal Populations

Abstract: The concept of the ecological trap, a low-quality habitat that animals prefer over other available habitats of higher quality, has appeared in the ecological literature irregularly for over 30 years, but the topic has received relatively little attention, and evidence for traps remains largely anecdotal. Recently, however, the ecological trap concept has been the subject of a flurry of theoretical activity that is likely to raise its profile substantially, particularly in conservation biology. Ecological trap theory suggests that, under most circumstances, the presence of a trap in a landscape will drive a local population to extinction. A number of empirical studies, almost all of birds, suggest the existence of traps and demonstrate the difficulties of recognizing them in the field. Evidence for ecological traps has primarily been found in habitats modified by human activities, either directly (e.g., through the mowing of grassland birds' nests) or indirectly (e.g., via human-mediated invasion of exotic species), but some studies suggest that traps may occur even in relatively pristine areas. Taken together, these theoretical and empirical results suggest that traps may be relatively common in rapidly changing landscapes. It is therefore important for conservation biologists to be able to identify traps and differentiate them from sinks. Commonly employed approaches for population modeling, which tend to assume a source-sink framework and do not consider habitat selection explicitly, may introduce faulty assumptions that mask the effects of ecological traps and lead to overly optimistic predictions about population persistence. Given the potentially dire consequences of ecological traps and the accumulating evidence for their existence, greater attention from the community of conservation biologists is warranted. In particular, it is important for conservation biologists and managers to incorporate into conservation planning an explicit understanding of the relationship between habitat selection and habitat quality.

The role of habitat area and edge in fragmented landscapes: definitively distinct or inevitably intertwined?This review is one of a series dealing with some aspects of the impact of habitat fragmentation on animals and plants. This series is one of several virtual symposia focussing on ecological topics that will be published in the Journal from time to time.

Abstract: Over the past few decades, much research has focussed on the effects of habitat area (i.e., patch size) and edges in fragmented landscapes. We review and synthesize the literature on area and edge effects to identify whether the eco- logical processes influenced by patch size and edge are distinct, to summarize evidence for the relative effect of each, and to discuss how estimating their independent effects may be accomplished in field studies. Area and edge directly influence ecological processes in distinct ways, yet indirect effects can be similar, making it difficult to isolate the effects of area and edge in nature. Many studies investigating both area and edge have been confounded in their design and (or) analysis (i.e., studies did not control for one potential effect while testing for the other). Nonconfounded studies have more fre- quently shown support for edge effects, and comparisons between nonconfounded and confounded studies suggest that some observed area effects could be explained by edge effects. We argue that by focussing on the fundamental processes directly influenced by area and edge, and by developing more rigorous study designs and analyses that isolate their relative influence, greater insight can be gained in future investigations on habitat loss and fragmentation.

Habitat edges and avian ecology: Geographic patterns and insights for western landscapes

Abstract: Habitat edges are an important feature in most terrestrial landscapes, due to increasing rates of habitat loss and fragmentation. A host of hypothesized influences of habitat edges on the distribution, abundance, and productivity of landbirds has been suggested over the past 60 years. Nevertheless, “edge effects” remains an ill-defined concept that encompasses a plethora of factors thought to influence avian ecology in heterogeneous landscapes. The vast majority of research on edge effects has been conducted in the broad-leafed forests of northeastern and midwestern North America. In general, many western habitats are more heterogeneous and naturally fragmented than their eastern counterparts, and habitat edges are a ubiquitous component of most western landscapes. These differences in landscape structure suggest that edge effects, and the mechanisms underlying them, may differ markedly in the West. We examined over 200 papers from the peer-reviewed literature on edge effects, focusing our efforts on empirical results and trends in research approaches. The relative dearth of western studies makes geographic comparisons difficult, but it is clear that mechanistic understanding of edge effects has lagged behind pattern identification. Bird responses to edge effects tend to vary markedly among species and among different edge types, while no clear pattern emerges regarding species diversity. In the context of the review, we discuss research and modeling approaches that could move our understanding of edge effects toward a more mechanistic and predictive frame-

One-Sided Edge Responses in Forest Birds Following Restoration Treatments

Abstract: . We studied the effects of the edge between two forest types on the probability of occurrence of seven species of birds and found that four responded to the edge on only one side. Over 4 years, we measured the responses of forest birds to the edge between ponderosa pine forest undergoing restoration and neighboring untreated stands. Of the seven species analyzed, one occurred most frequently near the edge. Of the remaining six, none responded to the edge in the treated forest, but four responded in the untreated forest. Relatively few studies have examined abundance changes on both sides of an edge between distinct habitats that support similar bird communities, and predictive models of edge effects used for mapping animal responses to habitat change often assume that animal abundance will change on both sides of this sort of edge, declining near the edge in the habitat in which the species is most abundant and increasing near the edge in the habitat in which the species is less abundant. One-sid...

Landscape modification and habitat fragmentation: a synthesis

Abstract: Landscape modification and habitat fragmentation are key drivers of global species loss. Their effects may be understood by focusing on: (1) individual species and the processes threatening them, and (2) human-perceived landscape patterns and their correlation with species and assemblages. Individual species may decline as a result of interacting exogenous and endogenous threats, including habitat loss, habitat degradation, habitat isolation, changes in the biology, behaviour, and interactions of species, as well as additional, stochastic threats. Human-perceived landscape patterns that are frequently correlated with species assemblages include the amount and structure of native vegetation, the prevalence of anthropogenic edges, the degree of landscape connectivity, and the structure and heterogeneity of modified areas. Extinction cascades are particularly likely to occur in landscapes with low native vegetation cover, low landscape connectivity, degraded native vegetation and intensive land use in modified areas, especially if keystone species or entire functional groups of species are lost. This review (1) demonstrates that species-oriented and pattern-oriented approaches to understanding the ecology of modified landscapes are highly complementary, (2) clarifies the links between a wide range of interconnected themes, and (3) provides clear and consistent terminology. Tangible research and management priorities are outlined that are likely to benefit the conservation of native species in modified landscapes around the world.

More than 75 percent decline over 27 years in total flying insect biomass in protected areas.

Abstract: Global declines in insects have sparked wide interest among scientists, politicians, and the general public. Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services. Our understanding of the extent and underlying causes of this decline is based on the abundance of single species or taxonomic groups only, rather than changes in insect biomass which is more relevant for ecological functioning. Here, we used a standardized protocol to measure total insect biomass using Malaise traps, deployed over 27 years in 63 nature protection areas in Germany (96 unique location-year combinations) to infer on the status and trend of local entomofauna. Our analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study. We show that this decline is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics cannot explain this overall decline. This yet unrecognized loss of insect biomass must be taken into account in evaluating declines in abundance of species depending on insects as a food source, and ecosystem functioning in the European landscape.

Confounding factors in the detection of species responses to habitat fragmentation

Abstract: Habitat loss has pervasive and disruptive impacts on biodiversity in habitat remnants. The magnitude of the ecological impacts of habitat loss can be exacerbated by the spatial arrangement -- or fragmentation -- of remaining habitat. Fragmentation per se is a landscape-level phenomenon in which species that survive in habitat remnants are confronted with a modified environment of reduced area, increased isolation and novel ecological boundaries. The implications of this for individual organisms are many and varied, because species with differing life history strategies are differentially affected by habitat fragmentation. Here, we review the extensive literature on species responses to habitat fragmentation, and detail the numerous ways in which confounding factors have either masked the detection, or prevented the manifestation, of predicted fragmentation effects. Large numbers of empirical studies continue to document changes in species richness with decreasing habitat area, with positive, negative and no relationships regularly reported. The debate surrounding such widely contrasting results is beginning to be resolved by findings that the expected positive species-area relationship can be masked by matrix-derived spatial subsidies of resources to fragment-dwelling species and by the invasion of matrix-dwelling species into habitat edges. Significant advances have been made recently in our understanding of how species interactions are altered at habitat edges as a result of these changes. Interestingly, changes in biotic and abiotic parameters at edges also make ecological processes more variable than in habitat interiors. Individuals are more likely to encounter habitat edges in fragments with convoluted shapes, leading to increased turnover and variability in population size than in fragments that are compact in shape. Habitat isolation in both space and time disrupts species distribution patterns, with consequent effects on metapopulation dynamics and the genetic structure of fragment-dwelling populations. Again, the matrix habitat is a strong determinant of fragmentation effects within remnants because of its role in regulating dispersal and dispersal-related mortality, the provision of spatial subsidies and the potential mediation of edge-related microclimatic gradients. We show that confounding factors can mask many fragmentation effects. For instance, there are multiple ways in which species traits like trophic level, dispersal ability and degree of habitat specialisation influence species-level responses. The temporal scale of investigation may have a strong influence on the results of a study, with short-term crowding effects eventually giving way to long-term extinction debts. Moreover, many fragmentation effects like changes in genetic, morphological or behavioural traits of species require time to appear. By contrast, synergistic interactions of fragmentation with climate change, human-altered disturbance regimes, species interactions and other drivers of population decline may magnify the impacts of fragmentation. To conclude, we emphasise that anthropogenic fragmentation is a recent phenomenon in evolutionary time and suggest that the final, long-term impacts of habitat fragmentation may not yet have shown themselves.

Landscape moderation of biodiversity patterns and processes - eight hypotheses

Abstract: Understanding how landscape characteristics affect biodiversity patterns and ecological processes at local and landscape scales is critical for mitigating effects of global environmental change. In this review, we use knowledge gained from human-modified landscapes to suggest eight hypotheses, which we hope will encourage more systematic research on

Ecological Responses to Habitat Edges: Mechanisms, Models, and Variability Explained

Abstract: ▪ Abstract Edge effects have been studied for decades because they are a key component to understanding how landscape structure influences habitat quality. However, making sense of the diverse patterns and extensive variability reported in the literature has been difficult because there has been no unifying conceptual framework to guide research. In this review, we identify four fundamental mechanisms that cause edge responses: ecological flows, access to spatially separated resources, resource mapping, and species interactions. We present a conceptual framework that identifies the pathways through which these four mechanisms can influence distributions, ultimately leading to new ecological communities near habitat edges. Next, we examine a predictive model of edge responses and show how it can explain much of the variation reported in the literature. Using this model, we show that, when observed, edge responses are largely predictable and consistent. When edge responses are variable for the same species ...