121 research outputs found

    Factors associated with bat mortality at wind energy facilities in the United States

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    Hundreds of thousands of bats are killed annually by colliding with wind turbines in the U.S., yet little is known about factors causing variation in mortality across wind energy facilities. We conducted a quantitative synthesis of bat collision mortality with wind turbines by reviewing 218 North American studies representing 100 wind energy facilities. This data set, the largest compiled for bats to date, provides further evidence that collision mortality is greatest for migratory tree-roosting species (Hoary Bat [Lasiurus cinereus], Eastern Red Bat [Lasiurus borealis], Silver-haired Bat [Lasionycteris noctivagans]) and from July to October. Based on 40 U.S. studies meeting inclusion criteria and analyzed under a common statistical framework to account for methodological variation, we found support for an inverse relationship between bat mortality and percent grassland cover surrounding wind energy facilities. At a national scale, grassland cover may best reflect openness of the landscape, a factor generally associated with reduced activity and abundance of tree-roosting species that may also reduce turbine collisions. Further representative sampling of wind energy facilities is required to validate this pattern. Ecologically informed placement of wind energy facilities involves multiple considerations, including not only factors associated with bat mortality, but also factors associated with bird collision mortality, indirect habitat-related impacts to all species, and overall ecosystem impacts

    The role of fire severity, distance from fire perimeter and vegetation on post-fire recovery of small-mammal communities in chaparral

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    Abstract. Chaparral shrublands in southern California, US, exhibit significant biodiversity but are prone to large, intense wildfires. Debate exists regarding fuel reduction to prevent such fires in wildland areas, but the effects of these fires on fauna are not well understood. We studied whether fire severity and distance from unburned fire perimeter influenced recovery of the small-mammal community from 13 to 39 months after the large (1134.2 km 2 ) Cedar fire in San Diego County. In general, neither factor influenced small-mammal recovery. However, vegetation characteristics, distance to riparian habitat and the prevalence of rocky substrate affected recovery in species-specific patterns. This indicates the effects of fire severity and immigration from outside the fire perimeter, if they occur, do so within 1 year, whereas longerterm recovery is largely driven by previously known relationships between small mammals and habitat structure. Our results, when combined with results from other studies in southern California, suggest where human lives or infrastructure are not at risk, efforts to preserve chaparral biodiversity should focus on maintaining the native plant community. Doing so may require novel management strategies in the face of an increasing human population, ignition sources and the spread of invasive exotic plants

    A General Modeling Framework for Describing Spatially Structured Population Dynamics

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    Variation in movement across time and space fundamentally shapes the abundance and distribution of populations. Although a variety of approaches model structured population dynamics, they are limited to specific types of spatially structured populations and lack a unifying framework. Here, we propose a unified network‐based framework sufficiently novel in its flexibility to capture a wide variety of spatiotemporal processes including metapopulations and a range of migratory patterns. It can accommodate different kinds of age structures, forms of population growth, dispersal, nomadism and migration, and alternative life‐history strategies. Our objective was to link three general elements common to all spatially structured populations (space, time and movement) under a single mathematical framework. To do this, we adopt a network modeling approach. The spatial structure of a population is represented by a weighted and directed network. Each node and each edge has a set of attributes which vary through time. The dynamics of our network‐based population is modeled with discrete time steps. Using both theoretical and real‐world examples, we show how common elements recur across species with disparate movement strategies and how they can be combined under a unified mathematical framework. We illustrate how metapopulations, various migratory patterns, and nomadism can be represented with this modeling approach. We also apply our network‐based framework to four organisms spanning a wide range of life histories, movement patterns, and carrying capacities. General computer code to implement our framework is provided, which can be applied to almost any spatially structured population. This framework contributes to our theoretical understanding of population dynamics and has practical management applications, including understanding the impact of perturbations on population size, distribution, and movement patterns. By working within a common framework, there is less chance that comparative analyses are colored by model details rather than general principles

    Mapping development preferences on the perceived value of ecosystem services and land use conflict and compatibility in Greater Kuala Lumpur

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    Rapid and unplanned development can diminish the social values for ecosystem services associated with urban landscapes. Tropical Global South cities, such as Greater Kuala Lumpur (GKL), Malaysia, that are highly biodiverse, are particularly vulnerable to the fragmentation and loss of natural ecosystems. This study investigates the social values for ecosystem services in GKL, a rapidly urbanising metropolitan area in Southeast Asia and presents the novel application of the SolVES (Social Values for Ecosystem Services) tool to an urban area. A public participatory GIS (PPGIS) survey was conducted to assess residents’ development preferences and perceived distribution of social values. The study revealed two groups of respondents, using cluster analysis, each with unique development preferences - a group favouring both green and grey developments and another favouring green development but strongly opposing grey development. The two groups differed statistically in their sociodemographic characteristics, and also how they mapped different social values. Our spatial analysis of their preferences towards future urban expansion in GKL highlighted locations where there is potential for land-use conflict. For example, the favour-balanced-development group tended to value built areas over green spaces. These findings support the need to consider residents’ preferences and socioecological traits through greater public engagement in urban landscape management. © 2024 The Author

    Density estimates of monarch butterflies overwintering in central Mexico

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    Given the rapid population decline and recent petition for listing of the monarch butterfly (Danaus plexippus L.) under the Endangered Species Act, an accurate estimate of the Eastern, migratory population size is needed. Because of difficulty in counting individual monarchs, the number of hectares occupied by monarchs in the overwintering area is commonly used as a proxy for population size, which is then multiplied by the density of individuals per hectare to estimate population size. There is, however, considerable variation in published estimates of overwintering density, ranging from 6.9–60.9 million ha−1. We develop a probability distribution for overwinter density of monarch butterflies from six published density estimates. The mean density among the mixture of the six published estimates was ∼27.9 million butterflies ha−1 (95% CI [2.4–80.7] million ha−1); the mixture distribution is approximately log-normal, and as such is better represented by the median (21.1 million butterflies ha−1). Based upon assumptions regarding the number of milkweed needed to support monarchs, the amount of milkweed (Asclepias spp.) lost (0.86 billion stems) in the northern US plus the amount of milkweed remaining (1.34 billion stems), we estimate >1.8 billion stems is needed to return monarchs to an average population size of 6 ha. Considerable uncertainty exists in this required amount of milkweed because of the considerable uncertainty occurring in overwinter density estimates. Nevertheless, the estimate is on the same order as other published estimates. The studies included in our synthesis differ substantially by year, location, method, and measures of precision. A better understanding of the factors influencing overwintering density across space and time would be valuable for increasing the precision of conservation recommendations

    Riding the Wave: Reconciling the Roles of Disease and Climate Change in Amphibian Declines

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    We review the evidence for the role of climate change in triggering disease outbreaks of chytridiomycosis, an emerging infectious disease of amphibians. Both climatic anomalies and disease-related extirpations are recent phenomena, and effects of both are especially noticeable at high elevations in tropical areas, making it difficult to determine whether they are operating separately or synergistically. We compiled reports of amphibian declines from Lower Central America and Andean South America to create maps and statistical models to test our hypothesis of spatiotemporal spread of the pathogen Batrachochytrium dendrobatidis (Bd), and to update the elevational patterns of decline in frogs belonging to the genus Atelopus. We evaluated claims of climate change influencing the spread of Bd by including error into estimates of the relationship between air temperature and last year observed. Available data support the hypothesis of multiple introductions of this invasive pathogen into South America and subsequent spread along the primary Andean cordilleras. Additional analyses found no evidence to support the hypothesis that climate change has been driving outbreaks of amphibian chytridiomycosis, as has been posited in the climate-linked epidemic hypothesis. Future studies should increase retrospective surveys of museum specimens from throughout the Andes and should study the landscape genetics of Bd to map fine-scale patterns of geographic spread to identify transmission routes and processes

    Riding the Wave: Reconciling the Roles of Disease and Climate Change in Amphibian Declines

    Get PDF
    We review the evidence for the role of climate change in triggering disease outbreaks of chytridiomycosis, an emerging infectious disease of amphibians. Both climatic anomalies and disease-related extirpations are recent phenomena, and effects of both are especially noticeable at high elevations in tropical areas, making it difficult to determine whether they are operating separately or synergistically. We compiled reports of amphibian declines from Lower Central America and Andean South America to create maps and statistical models to test our hypothesis of spatiotemporal spread of the pathogen Batrachochytrium dendrobatidis (Bd), and to update the elevational patterns of decline in frogs belonging to the genus Atelopus. We evaluated claims of climate change influencing the spread of Bd by including error into estimates of the relationship between air temperature and last year observed. Available data support the hypothesis of multiple introductions of this invasive pathogen into South America and subsequent spread along the primary Andean cordilleras. Additional analyses found no evidence to support the hypothesis that climate change has been driving outbreaks of amphibian chytridiomycosis, as has been posited in the climate-linked epidemic hypothesis. Future studies should increase retrospective surveys of museum specimens from throughout the Andes and should study the landscape genetics of Bd to map fine-scale patterns of geographic spread to identify transmission routes and processes

    Effects of Fire Severity and Distance from Unburned Edge on Mammalian Community Post-fire Recovery

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    This final report summarizes key findings relative to the five major objectives listed in our proposal, along with the crosswalk of accomplished and future deliverables. Additional details concerning objectives, methods, results, and recommendations are presented in Attachment A. Each of our major objectives is listed below with a brief summary of findings to date. Because we only recently finished the final session of data collection, all findings are preliminary and may change as more comprehensive statistical analyses are completed. 1. Evaluate the effects of fire on southern California rodent, large mammal, and bat diversity and study patterns of post fire recovery. Overview: Fire immediately alters the composition of the mammal community in chaparral and coastal sage scrub vegetation, although species responses to fire, including changes over time following fire, are highly species-specific. In chaparral, overall rodent richness is similar between burned and unburned areas, but the composition of the community is very different between these conditions. Furthermore, even after 4 years, the post-burn communities differ from their pre-fire status and from unburned communities. Fire in coastal sage scrub reduced rodent diversity to a simpler community, similar to that that of disturbed habitats dominated by annual grasses and forbs. Carnivore species appear not to be strongly affected by fire. We also detected little effect of burn status on the bat community, although at least two species appear to forage more frequently over unburned chaparral. Rodents: We examined rodent responses to fire in both chaparral (Cedar Fire; Cleveland National Forest) and coastal sage scrub (Otay Fire; Rancho Jamul Ecological Reserve) vegetation beginning about 13 months following fire and continuing until 43 months post fire. In both communities we noted substantial differences in mammal community composition between burned and unburned habitat, and in patterns of post-fire responses over time. Some species were clearly more widespread and abundant in burned than unburned chaparral, others showed the opposite pattern, and still others showed more complex associations with fire over time (Figure 1). For example, the Dulzura kangaroo rat (Dipodomys simulans; DISI) was far more common on burned than unburned plots over the nearly 4-year study duration, while the California mouse (Peromyscus californicus; PECA) was far more common on unburned plots, and the cactus mouse (Peromyscus eremicus; PEER) was equally common on burned and unburned plots. In unburned chaparral, PECA dominated the rodent community across the entire study period, with several other species varying in their relative abundance over time. For example, the California pocket mouse (Chaetodiopus californicus; CHCA) was not abundant on unburned plots during the first spring sampling session, but increased to become the second most abundant species during the last two spring samples (the third and fourth springs following fire). Conversely, the brush mouse (Peromyscus boylii; PEBO) was fairly common on unburned plots early in the study, but gradually declined to become a minor component of the community in latter sessions. Burned plots were dominated by deer mice (Peromyscus maniculatus; PEMA) during the first post-fire spring sample, with DISI second most abundant. Over time, PEMA declined in abundance on burned plots, while DISI increased to become the dominant species. The bigeared woodrat (Neotoma macrotis; NEMA) was very rare on burned plots although common on unburned plots. In contrast, the desert woodrat (N. lepida; NELE) was about equally common on burned and unburned plots. Despite gradual recovery of some chaparral species on burned plots over time, compositional differences between burned and unburned plots were still pronounced 4 years following fire, and the communities are still changing. Sampling would need to continue for more years to determine when communities return to pre-fire status
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