The scope and severity of white-nose syndrome on hibernating bats in North America

Assessing the scope and severity of threats is necessary for evaluating impacts on populations to inform conservation planning. Quantitative threat assessment often requires monitoring programs that provide reliable data over relevant spatial and temporal scales, yet such programs can be difficult to justify until there is an apparent stressor. Leveraging efforts of wildlife management agencies to record winter counts of hibernating bats, we collated data for 5 species from over 200 sites across 27 U.S. states and 2 Canadian provinces from 1995 to 2018 to determine the impact of white-nose syndrome (WNS), a deadly disease of hibernating bats. We estimated declines of winter counts of bat colonies at sites where the invasive fungus that causes WNS (Pseudogymnoascus destructans) had been detected to assess the threat impact of WNS. Three species undergoing species status assessment by the U.S. Fish and Wildlife Service (Myotis septentrionalis, Myotis lucifugus, and Perimyotis subflavus) declined by more than 90%, which warrants classifying the severity of the WNS threat as extreme based on criteria used by NatureServe. The scope of the WNS threat as defined by NatureServe criteria was large (36% of Myotis lucifugus range) to pervasive (79% of Myotis septentrionalis range) for these species. Declines for 2 other species (Myotis sodalis and Eptesicus fuscus) were less severe but still qualified as moderate to serious based on NatureServe criteria. Data-sharing across jurisdictions provided a comprehensive evaluation of scope and severity of the threat of WNS and indicated regional differences that can inform response efforts at international, national, and state or provincial jurisdictions. We assessed the threat impact of an emerging infectious disease by uniting monitoring efforts across jurisdictional boundaries and demonstrated the importance of coordinated monitoring programs, such as the North American Bat Monitoring Program (NABat), for data-driven conservation assessments and planning.     

浅水湖泊孢粉和植物残体对水生植被的表现率

研究浅水湖泊中植物残体对水生植物的表现率,用于重建近代水生植被历史,可为治理湖泊富营养化,恢复湖泊生态环境提供依据。研究选址为英国北部的一个小湖泊,通过水生植物调查及表层沉积物中植物残体和孢粉分析,及地理信息系统方法定量研究植物残体对水生植物的表现率。结果表明：沉积物中植物残体精确地反映了植物优势种的存在;植物和植物残体的关系是很复杂的,有些植物在残体中表现率明显超高,而有些表现率偏低; 应把叶子和其它非繁殖植株部分作为恢复近代多年生植物历史依据;植物残体传输性较差,主要集中在植物母体附近;利用植物残体与孢粉分析相结合的方法能更准确地重建植被历史。     

Environmental impact assessment for aquatic ecosystems of industrial effluents†

A system of environmental impact assessment of industrial effluents is presented and discussed. Environmental assessment consists of three phases, hazard assessment, risk determination, and societary evaluation. It is regarded an integrated study of natural sciences, i.e. ecochemicology (chemical fate), ecotoxicology (toxical effects), and ecoepidemiology (biological damages); and social sciences, e.g. geography, sociology, and economy. And the outcome should be the basis of political decision making. Hazard assessment may be divided into a subphase of hazard identification from a base set of scientific information on the industrial effluent, and a second subphase of hazard analysis at a more elevated level of scientific information akin to the procedures suggested elsewhere for single chemicals. Methods of hazard assessment are laboratory experiments, e.g. chemical analysis, degradation and bioaccumulation studies, acute and chronic toxicity assessments, physical modelling, etc. Risk determination may then be conducted by extrapolation of the obtained results from laboratory to field, i.e. by risk estimation to the receiving waters, using methods of hydraulic modelling, biological surveillance, etc. Risk‐benefit evaluation is conducted in the society evaluation phase by balancing environmental consequences against the society value of the production. The outcome is determined by the interaction between hazard‐makers (industry), risk‐takers (administrators), guardians (regulators), and assessors (scientists) in risk management, the crank of environmental assessment.     

Correlation between the seasonal distribution of harbour porpoises and their prey in the Sound,Baltic Sea

Low densities of harbour porpoises in winter (November–March) and high densities in summer (April–October) were found in the Sound, connecting the Baltic Sea and Kattegat. Due to their high energy requirements, it is hypothesized that the density of harbour porpoises is related to local prey abundance. This was tested by examining the stomach content of 53 harbour porpoises collected between 1987 and 2010 in the Sound (high season, 34 porpoises; low season, 19 porpoises). A total of 1,442 individual fish specimens from thirteen species were identified. Twelve of these were present in the high–porpoise density season and seven in the low-density season. The distribution of occurrence and the distribution of number of fish species were different between seasons, indicating a shift in prey intake between seasons. Furthermore, during the high-density season, the mean and total prey weight per stomach as well as the prey species diversity was higher. However, no difference was found in the number of prey species between the two seasons, indicating a higher quality of prey in the high-density season. Atlantic cod was found to be the main prey species in terms of weight in the high-density season while Atlantic herring and Atlantic cod were equally important during the low-density season. Prey availability and predictability are suggested as the main drivers for harbour porpoise distribution, and this could be caused by the formation of frontal zones in spring in the northern part of the Sound, leading to prey concentrations in predictable areas.     

Predicting a ‘tree change’ in Australia's tropical savannas: Combining different types of models to understand complex ecosystem behaviour

In this study, key ecological modelling limitations of a process-based simulation model and a Bayesian network were reduced by combining the two approaches. We demonstrate the combined modelling approach with a case study investigating increases in woody vegetation density in northern Australia's tropical savannas. We found that by utilising the strengths of a simulation model and a Bayesian network we could both forecast future change in woody vegetation density and diagnose the reasons for current vegetation states. The local conditions of climate, soil characteristics and the starting population of trees were found to be more important in explaining the likelihood of change in woody vegetation density compared to management practices such as grazing pressure and fire regimes. We conclude that combining the strengths of a process and BN model allowed us to produce a simple model that utilised the ability of the process model to simulate ecosystem processes in detail and over long time periods, and the ability of the BN to capture uncertainty in ecosystem response and to conduct scenario, sensitivity and diagnostic analysis. The overall result was a model that has the potential to provide land managers with a better understanding of the behaviour of a complex ecosystem than simply utilising either modelling approach in isolation.     

Determinants of reproductive potential and population size in open populations of Patella vulgata

The importance of external and internal population processes in determining variation in reproductive output and variation in population size were quantified with model simulations for open populations of the sequentially hermaphroditic limpet Patella vulgata using field data from the Isle of Man and South West Ireland. Cross-correlation analyses of model outputs and elasticity analyses show that population dynamics are dominated by the effects of large females, and that recruitment adds little to reproductive output. However, populations experiencing low but highly variable recruitment appear male limited and recruitment pulses carrying young males into the population are correlated to reproductive output with a 2–5-year lag. We conclude that pulses in recruitment can be a major structuring force in these limpet populations, but site-specific post-recruitment processes will determine the relative importance of recruitment to population dynamics and the lag between recruitment and reproductive output.     

The oasis effect: response of birds to exurban development in a southwestern savanna

Ranches are being converted to exurban housing developments in the southwestern United States, with potentially significant but little-studied impacts on biological diversity. We counted birds in grasslands and savannas in southeastern Arizona that were grazed by livestock, embedded in low-density exurban housing developments, or both, or neither. Species richness and bird abundance were higher in exurban neighborhoods than in undeveloped landscapes, independent of livestock grazing. The positive response to development was particularly evident among doves, quail, hummingbirds, aerial insectivores, and some but not all ground-foraging sparrows. Effects of livestock grazing were comparatively minor and mostly involved birds with requirements for tall ground cover or the lack of it. The average rank correlation between counts of individual species and housing density was positive across all transects. However, this relationship disappeared among the exurban transects alone, and bird species richness on the exurban transects was negatively correlated with the number of homes nearby. These results suggest that the positive influence of exurban development on avian abundance and variety was greatest at the lowest housing densities. We attribute the attraction of many birds to exurban development to an oasis effect, in which resources otherwise scarce in arid southwestern environments (shade, nectar, nest sites, and especially water) are relatively abundant around exurban home sites. This finding is consistent with the hypothesis that exurban home sites represented resource supply points inside birds' home ranges otherwise consisting mostly of natural vegetation.     

Spatial dynamics and substrate impacts of recreational snorkelers and SCUBA divers in Hawaiian Marine Protected Areas

We quantified spatial dynamics and substrate impacts of snorkelers and SCUBA divers within four Hawaiian MPAs to determine: (1) whether coral reefs in these areas are being damaged by recreational activities, and (2) how damage might be mitigated. Observers secretly followed snorkelers and SCUBA divers, and used handheld Global Positioning System (GPS) units to record their geographic tracks and substrate contacts. Most activities occurred within relatively small, well-defined areas associated with access points. Despite heavy use, recreation impact was low at Hawaiian MPAs because most fragile corals occurred below the maximum depth of the dominant recreational activity (snorkeling). SCUBA diving was only common at one MPA with physically durable benthic habitats. GPS tracking provided useful insights into how recreational impacts to MPAs could be reduced. General topography could be used to predict where visitors will go, and designated access points could be used to focus substrate contact away from fragile habitats.     

In situ push-pull method to determine ground water denitrification in riparian zones

To quantify ground water denitrification in discrete locations of riparian aquifers, we modified and evaluated an in situ method based on conservative tracers and 15N-enriched nitrate. Ground water was "pushed" (i.e., injected) into a mini-piezometer and then "pulled" (i.e., extracted) from the same mini-piezometer after an incubation period. This push-pull method was applied in replicate mini-piezometers at two Rhode Island riparian sites, one fresh water and one brackish water. Conservative tracer pretests were conducted to determine incubation periods, ranging from 5 to 120 h, to optimize recovery of introduced plumes. For nitrate push-pull tests, we used two conservative tracers, sulfur hexafluoride and bromide, to provide insight into plume recovery. The two conservative tracers behaved similarly. The dosing solutions were amended with 15N-enriched nitrate that enabled us to quantify the mass of denitrification gases generated during the incubation period. The in situ push-pull method detected substantial denitrification rates at a site where we had previously observed high denitrification rates. At our brackish site, we found high rates of ground water denitrification in marsh locations and minimal denitrification in soils fringing the marsh. The push-pull method can provide useful insights into spatial and temporal patterns of denitrification in riparian zones. The method is robust and results are not seriously affected by dilution or degassing from ground water to soil air. In conjunction with measurements of ground water flow-paths, this method holds promise for evaluating the influence of site and management factors on the ground water nitrate removal capacity of riparian zones.