Understanding abundance patterns of a declining seabird: implications for monitoring.

The Kittlitz's Murrelet (Brachyramphus brevirostris) is a rare, non-colonial seabird often associated with tidewater glaciers and a recent candidate for listing under the Endangered Species Act. We estimated abundance of Kittlitz's Murrelets across space and time from at-sea surveys along the coast of Alaska (USA) and then used these data to develop spatial models to describe abundance patterns and identify environmental factors affecting abundance. Over a five-week period in the summer of 2005, we recorded 794 Kittlitz's Murrelets, 16 Marbled Murrelets (B. marmoratus), and 70 unidentified murrelets. The overall population estimate (N, mean +/- SE) during the peak period (3-9 July) was 1317 +/- 294 birds, decreasing to 68 +/- 37 by the last survey period (31 July-6 August). Density of Kittlitz's Murrelets was highest in pelagic waters of Taan Fjord (18.6 +/- 7.8 birds/km2, mean +/- SE) during 10-16 July. Spatial models identified consistent "hotspots" of Kittlitz's Murrelets, including several small areas where high densities of murrelets were found throughout the survey period. Of the explanatory variables that we evaluated, tidal current strength influenced murrelet abundance most consistently, with higher abundance associated with strong tidal currents. Simulations based on the empirically derived estimates of variation demonstrated that spatial variation strongly influenced power to detect trend, although power changed little across the threefold difference in the coefficient of variation on detection probability. We include recommendations for monitoring Kittlitz's Murrelets (or other marine species) when there is a high degree of uncertainty about factors affecting abundance, especially spatial variability.     

Spatial factors affecting statistical power in testing marine fauna displacement

Impacts of offshore wind farms on marine fauna are largely unknown. Therefore, one commonly adheres to the precautionary principle, which states that one shall take action to avoid potentially damaging impacts on marine ecosystems, even when full scientific certainty is lacking. We implement this principle by means of a statistical power analysis including spatial factors. Implementation is based on geostatistical simulations, accommodating for zero-inflation in species data. We investigate scenarios in which an impact assessment still has to be carried out. Our results show that the environmental conditions at the time of the survey is the most influential factor on power. This is followed by survey effort and species abundance in the reference situation. Spatial dependence in species numbers at local scales affects power, but its effect is smaller for the scenarios investigated. Our findings can be used to improve effectiveness of the economical investment for monitoring surveys. In addition, unnecessary extra survey effort, and related costs, can be avoided when spatial dependence in species abundance is present and no improvement on power is achieved.     

Scale-dependent response diversity of seabirds to prey in the North Sea

Functional response diversity is defined as the diversity of responses to environmental change among species that contribute to the same ecosystem function. Because different ecological processes dominate on different spatial and temporal scales, response diversity is likely to be scale dependent. Using three extensive data sets on seabirds, pelagic fish, and zooplankton, we investigate the strength and diversity in the response of seabirds to prey in the North Sea over three scales of ecological organization. Two-stage analyses were used to partition the variance in the abundance of predators and prey among the different scales of investigation: variation from year to year, variation among habitats, and variation on the local patch scale. On the year-to-year scale, we found a strong and synchronous response of seabirds to the abundance of prey, resulting in low response diversity. Conversely, as different seabird species were found in habitats dominated by different prey species, we found a high diversity in the response of seabirds to prey on the habitat scale. Finally, on the local patch scale, seabirds were organized in multispecies patches. These patches were weakly associated with patches of prey, resulting in a weak response strength and a low response diversity. We suggest that ecological similarities among seabird species resulted in low response diversity on the year-to-year scale. On the habitat scale, we suggest that high response diversity was due to interspecific competition and niche segregation among seabird species. On the local patch scale, we suggest that facilitation with respect to the detection and accessibility of prey patches resulted in overlapping distribution of seabirds but weak associations with prey. The observed scale dependencies in response strength and diversity have implications for how the seabird community will respond to different environmental disturbances.     

Evaluating the coastal environment for marine birds

The marine environment is being increasingly exploited by fisheries and the oil and gas industry. Conservationists urgently need the ability to identify the processes that determine patterns of abundance of marine species. We describe a preliminary Geographic Information System (GIS) in which spatial data on environmental variables (seabird colony locations, sea depth and seabed sediments) are integrated with realistic energy constraints faced by marine birds during the breeding season. A simple foraging model predicts the spatial variation in the quality of given locations as potential feeding sites under different feeding conditions and stages of the breeding cycle. We show how the approach can be used to help managers identify key marine areas and assess the impacts of environmental change or damage.     

A statistical evaluation of non-ergodic variogram estimators

Geostatistics is a set of statistical techniques that is increasingly used to characterize spatial dependence in spatially referenced ecological data. A common feature of geostatistics is predicting values at unsampled locations from nearby samples using the kriging algorithm. Modeling spatial dependence in sampled data is necessary before kriging and is usually accomplished with the variogram and its traditional estimator. Other types of estimators, known as non-ergodic estimators, have been used in ecological applications. Non-ergodic estimators were originally suggested as a method of choice when sampled data are preferentially located and exhibit a skewed frequency distribution. Preferentially located samples can occur, for example, when areas with high values are sampled more intensely than other areas. In earlier studies the visual appearance of variograms from traditional and non-ergodic estimators were compared. Here we evaluate the estimators' relative performance in prediction. We also show algebraically that a non-ergodic version of the variogram is equivalent to the traditional variogram estimator. Simulations, designed to investigate the effects of data skewness and preferential sampling on variogram estimation and kriging, showed the traditional variogram estimator outperforms the non-ergodic estimators under these conditions. We also analyzed data on carabid beetle abundance, which exhibited large-scale spatial variability (trend) and a skewed frequency distribution. Detrending data followed by robust estimation of the residual variogram is demonstrated to be a successful alternative to the non-ergodic approach.     

Modeling Abundance Index Data from Anuran Calling Surveys

Abstract:  Evaluation of anuran populations is commonly based on calling surveys that report categorical abundance index data. I present a statistical model for abundance index data that are observations representing ordered abundance classes (e.g., none, some, many). The proposed model provides a formal treatment of detection probability, factors that affect detection, and variation in abundance. The model can be viewed as a generalization of that proposed by MacKenzie et al. (2002) for estimating site-occupancy rates in that it allows for more than two abundance classes. Because the abundance distribution is characterized by multiple abundance classes, it may be more sensitive to subtle changes in the underlying abundance that may go undetected with simple occupancy estimates under which sites are characterized merely as occupied or not. The method is most immediately applicable to surveys of anurans in which index data related to the intensity of calling activity are collected. I applied the proposed method to calling index data from the green frog (  Rana clamitans ) collected as part of the North American Amphibian Monitoring Program. The best model indicated considerable variation in detectability over time and in response to temperature. The resulting adjusted (for detectability) abundance-state distribution demonstrates the negative bias in abundance state obtained from simplistic summaries of calling index data that disregard these sources of variation in detectability.     

Geospatial variability of krill and top predators within an Antarctic submarine canyon system

The spatial distribution patterns of krill, seabirds (penguin, petrel and albatross), fur seals and baleen whales were mapped in nearshore waters (<50 km from land) to investigate their habitat selection within two adjacent submarine canyons near Livingston Island, Antarctica. Three shipboard surveys were conducted (February 2005–2007), and an echosounder was used to measure the distribution and abundance of krill while simultaneously conducting visual surveys to map seabird and marine mammals. Using a multispecies approach, we test the hypothesis that spatial organization of krill and top predators co-vary according to fine-scale changes in bathymetry in the nearshore marine environment. GAMs are used to examine the effect of sea depth, slope and distance to isobaths on the spatial distribution and abundance of krill and predators. Spatial distribution patterns of krill and predators relate to fine-scale (1–10 km) changes in bathymetry and exhibit cross-shelf gradients in abundance. Krill were concentrated along the shelf-break and abundant within both submarine canyons. Predators exhibited different preferences for locations within the submarine canyon system that relates to their foraging behavior. Penguins concentrated closer to shore and within the head of the east submarine canyon immediately adjacent to a breeding colony. Whales were also concentrated over the head of the east canyon (overlapping with penguins), whereas albatrosses and fur seals were concentrated in the west canyon. Fur seals also showed preference for steep slopes and were concentrated along the shelf-break. Petrels exhibited peaks in abundance throughout both submarine canyons. Owing to their orientation, size and proximity to the coastline, submarine canyons provide important habitat heterogeneity for krill and a variety of predators. This study highlights the multispecies approach for studying spatial ecology of top predators and krill and has implications for marine spatial management of the Scotia Sea.     

Trends in seabird breeding populations across the Great Barrier Reef

The Great Barrier Reef is an iconic ecosystem, known globally for its rich marine biodiversity that includes many thousands of tropical breeding seabirds. Despite indications of localized declines in some seabird species from as early as the mid-1990s, trends in seabird populations across the reef have never been quantified. With a long history of human impact and ongoing environmental change, seabirds are likely sentinels in this important ecosystem. Using 4 decades of monitoring data, we estimated site-specific trends for 9 seabird species from 32 islands and cays across the reef. Trends varied markedly among species and sites, but probable declines occurred at 45% of the 86 species-by-site combinations analyzed compared with increases at 14%. For 5 species, we combined site-specific trends into a multisite trend in scaled abundance, which revealed probable declines of Common Noddy (Anous stolidus), Sooty Tern (Onychoprion fuscatus), and Masked Booby (Sula dactylatra), but no long-term changes in the 2 most widely distributed species, Greater Crested Tern (Thalasseus bergii) and Brown Booby (Sula leucogaster). For Brown Booby, long-term stability largely resulted from increases at a single large colony on East Fairfax Island that offset declines at most other sites. Although growth of the Brown Booby population on East Fairfax points to the likely success of habitat restoration on the island, it also highlights a general vulnerability wherein large numbers of some species are concentrated at a small number of key sites. Identifying drivers of variation in population change across species and sites while ensuring long-term protection of key sites will be essential to securing the future of seabirds on the reef.     

Detecting Population Declines over Large Areas with Presence-Absence, Time-to-Encounter, and Count Survey Methods

Abstract:  Ecologists often discount presence-absence surveys as a poor way to gain insight into population dynamics, in part because these surveys are not amenable to many standard statistical tests. Still, presence-absence surveys are sometimes the only feasible alternative for monitoring large areas when funds are limited, especially for sparse or difficult-to-detect species. I undertook a detailed simulation study to compare the power of presence-absence, count, and time-to-encounter surveys to detect regional declines in a population. I used a modeling approach that simulates both population numbers and the monitoring process, accounting for observation and other measurement errors. In gauging the efficacy of presence-absence surveys versus other approaches, I varied the number of survey sites, the spatial variation in encounter rate, the mean encounter rate, and the type of population loss. My results showed that presence-absence data can be as or more powerful than count data in many cases. Quantitative guidelines for choosing between presence-absence surveys and count surveys depend on the biological and logistical constraints governing a conservation monitoring situation. Generally, presence-absence surveys work best when there is little variability in abundance among the survey sites, the organism is rare, and the species is difficult to detect so that the time spent getting to each survey site is less than or equal to the time spent surveying each site. Count surveys work best otherwise. I present a case study with count data on the Northern Flicker ( Colaptes auratus ) from the North American Breeding Bird Survey to illustrate how the method might be used with field-survey data. The case study demonstrates that a count survey would be the most cost-effective design but would entail reduction in the number of sites. If this site reduction is not desirable, a presence-absence survey would be the most cost-effective survey.     

Evaluating impacts of forage fish abundance on marine predators

Forage fish—small, low trophic level, pelagic fish such as herrings, sardines, and anchovies—are important prey species in marine ecosystems and also support large commercial fisheries. In many parts of the world, forage fish fisheries are managed using precautionary principles that target catch limits below the maximum sustainable yield. However, there are increasing calls to further limit forage fish catch to safeguard their fish, seabird, and marine mammal predators. The effectiveness of these extra-precautionary regulations, which assume that increasing prey abundance increases predator productivity, are under debate. In this study, we used prey-linked population models to measure the influence of forage fish abundance on the population growth rates of 45 marine predator populations representing 32 fish, seabird, and mammal species from 5 regions around the world. We used simulated data to confirm the ability of the statistical model to accurately detect prey influences under varying levels of influence strength and process variability. Our results indicate that predator productivity was rarely influenced by the abundance of their forage fish prey. Only 6 predator populations (13% of the total) were positively influenced by increasing prey abundance and the model exhibited high power to detect prey influences when they existed. These results suggest that additional limitation of forage fish harvest to levels well below sustainable yields would rarely result in detectable increases in marine predator populations.     

Predicting the Spatial Distribution of a Seabird Community to Identify Priority Conservation Areas in the Timor Sea

Understanding spatial and temporal variability in the distribution of species is fundamental to the conservation of marine and terrestrial ecosystems. To support strategic decision making aimed at sustainable management of the oceans, such as the establishment of protected areas for marine wildlife, we identified areas predicted to support multispecies seabird aggregations in the Timor Sea. We developed species distribution models for 21 seabird species based on at‐sea survey observations from 2000–2013 and oceanographic variables (e.g., bathymetry). We applied 4 statistical modeling techniques and combined the results into an ensemble model with robust performance. The ensemble model predicted the probability of seabird occurrence in areas where few or no surveys had been conducted and demonstrated 3 areas of high seabird richness that varied little between seasons. These were located within 150 km of Adele Island, Ashmore Reef, and the Lacepede Islands, 3 of the largest aggregations of breeding seabirds in Australia. Although these breeding islands were foci for high species richness, model performance was greatest for 3 nonbreeding migratory species that would have been overlooked had regional monitoring been restricted to islands. Our results indicate many seabird hotspots in the Timor Sea occur outside existing reserves (e.g., Ashmore Reef Marine Reserve), where shipping, fisheries, and offshore development likely pose a threat to resident and migratory populations. Our results highlight the need to expand marine spatial planning efforts to ensure biodiversity assets are appropriately represented in marine reserves. Correspondingly, our results support the designation of at least 4 new important bird areas, for example, surrounding Adele Island and Ashmore Reef. Pronostico de la Distribución Espacial de una Comunidad de Aves Marinas para Identificar Áreas Prioritarias de Conservación en el Mar de Timor     

Differential effects of a local industrial sand lance fishery on seabird breeding performance.

Fisheries management across the world is moving toward an ecosystem-based approach, implying that fishery effects on nontarget species should be taken into account. However, such effects are often not well understood, partly because, they can be difficult to distinguish from impacts of environmental fluctuations. We evaluated the effects of an industrial sand lance (Ammodytes marinus) fishery off the North Sea coast of the United Kingdom, which has been opened and closed in a quasi-experimental fashion, on sand-lance-dependent breeding seabirds. Controlling for environmental variation (sea surface temperature, abundance of larval sand lance, and size of adult sand lance), we found that, when the fishery was operating, breeding productivity in the intensively studied seabird colony on the Isle of May was significantly depressed for one surface-feeding seabird species, the Black-legged Kittiwake (Rissa tridactyla), but not for four diving species. Analyzing Kittiwake data from 12 colonies inside and outside the closure zone in a replicated before-after control-impact design, we again found that breeding productivity was significantly depressed in the closure zone when the fishery was active, whereas no effect was found in the control zone. Furthermore, Kittiwake breeding productivity was negatively correlated with fishery effort during the fishery period in the closure zone, but not in the control zone. The contrasting findings in the two zones could be related to environmental differences or to the fact that only one study colony in the control zone was exposed to high fishery effort within the typical foraging range of Kittiwakes during the breeding season. The strong impact on Kittiwakes, but not on diving species, could result from (1) inherently high sensitivity to reduced prey availability, (2) changes in the vertical distribution of sand lance at lower densities, (3) sand lance showing avoidance behavior to fishery vessels, or a combination of some or all of these factors. These findings indicate that local fishery closures can benefit sensitive predators and should be considered as a tool for future ecosystem-based fisheries management.     

Where the wild things are: predicting hotspots of seabird aggregations in the California Current System

Marine protected areas (MPAs) provide an important tool for conservation of marine ecosystems. To be most effective, these areas should be strategically located in a manner that supports ecosystem function. To inform marine spatial planning and support strategic establishment of MPAs within the California Current System, we identified areas predicted to support multispecies aggregations of seabirds ("hotspots"). We developed habitat-association models for 16 species using information from at-sea observations collected over an 11-year period (1997-2008), bathymetric data, and remotely sensed oceanographic data for an area from north of Vancouver Island, Canada, to the USA/Mexico border and seaward 600 km from the coast. This approach enabled us to predict distribution and abundance of seabirds even in areas of few or no surveys. We developed single-species predictive models using a machine-learning algorithm: bagged decision trees. Single-species predictions were then combined to identify potential hotspots of seabird aggregation, using three criteria: (1) overall abundance among species, (2) importance of specific areas ("core areas") to individual species, and (3) predicted persistence of hotspots across years. Model predictions were applied to the entire California Current for four seasons (represented by February, May, July, and October) in each of 11 years. Overall, bathymetric variables were often important predictive variables, whereas oceanographic variables derived from remotely sensed data were generally less important. Predicted hotspots often aligned with currently protected areas (e.g., National Marine Sanctuaries), but we also identified potential hotspots in Northern California/Southern Oregon (from Cape Mendocino to Heceta Bank), Southern California (adjacent to the Channel Islands), and adjacent to Vancouver Island, British Columbia, that are not currently included in protected areas. Prioritization and identification of multispecies hotspots will depend on which group of species is of highest management priority. Modeling hotspots at a broad spatial scale can contribute to MPA site selection, particularly if complemented by fine-scale information for focal areas.     

Trend der Schwermetall-Bioakkumulation 1990 bis 2005: Qualitätssicherung bei Probenahme, Analytik, geostatistischer Auswertung

Background, aim and scope Since 1990, the UN ECE Heavy Metals in Mosses Surveys provide data inventories of the atmospheric heavy metal bioaccumulation across national boundaries in Europe. The results prove how air pollution control in Germany and in all of Europe affected the bioaccumulation of metals in those ecosystems that are not directly influenced by nearby emission sources. This article focuses on the assessment of spatiotemporal patterns of the metal bioaccumulation in Germany since 1990. Furthermore, the spatial variance of the metal bioaccumulation is analysed with regard to sampling site-specific and regional land characteristics. Special focus hereby relies on the correlation of the metal concentration in mosses and in depositions. Hence, the moss surveys contribute to §?12 of the German Federal Nature Conservation Act as well as to the “Convention on Long-range Transboundary Air Pollution” (CLRTAP). Materials and methods The bioaccumulation of up to 40 trace elements in mosses was determined according to a European wide harmonised methodology. The according experimental protocol regulates the selection of sampling sites and moss species, the chemical analysis and quality control and the classification of the measured values for the mapping of spatial patterns. In Germany all sampling sites were described with regard to topographical and ecological criteria as well as other aspects seen as relevant in the mandatory guideline. Together with the measurements this metadata was combined with other information regarding emissions and land use in the surroundings of the sampling sites in the WebGIS MossMet. The spatial structure of the metal bioaccumulation was analysed and modeled by variogram analyses and then mapped by applying different kriging techniques. Furthermore, different multi-metal indices (MMI) were derived for both the sampling sites and raster maps with the help of percentile statistics: The MMI1990 aggregates the data for Cr, Cu, Fe, Ni, Pb, Ti, V and Zn determined in 1990. The MMI1995, MMI2000, MMI2005 furthermore include As, Cd, Hg and Sb for 1995, 2000 and 2005, respectively. Two other MMI allow for a time integrating view on the metal bioaccumulation in Germany: The MMI1990–2005 was calculated on behalf of all measured/geostatistically estimated data for Cr, Cu, Fe, Ni, Pb, Ti, V and Zn. Therefore the integrated assessment of the metal bioaccumulation in Germany from 1990 to 2005 is possible. The MMI1995–2005 furthermore includes the element-specific data of As, Cd, Hg and Sb therefore integrating 12 elements over the last three surveys. The statistical association of the metal bioaccumulation, site-specific characteristics as well as information on land use and emissions was analysed by bivariate correlation analysis and multivariate decision tree models (Classification and Regression Trees – CART, Chisquare Automatic Interaction Detection – CHAID). Results The results of the quality-controlled chemical analyses show a significant decrease of the metal bioaccumulation in Germany from 1990 to 2000. From 2000 to 2005 a further decrease can be stated for Hg, Pb and Ti. However, a significant increase for Cd, Cr, Cu, Sb and Zn can be observed. This especially holds true for Cr (+ 160?%) that almost reaches as high concentrations in mosses as in 1990. In 2005, the metal loads in mosses, except for Cr, show spatial distributions similar to those in 1990, 1995 and 2000. Hot spots are mostly found in the urbanised and industrially influenced Ruhr Area, the densely populated Rhine–Main region and in the industrially influenced regions of former East Germany (e.?g. Halle–Leipzig region). The spatial variance of the metal bioaccumulation can mainly be explained by site-specific (moss species, canopy drip effects) and site-surrounding (land use, depositions, emissions) characteristics. Discussion High Cr loads in mosses were also registered in other European countries like in Switzerland. Further investigation is therefore necessary to investigate whether this is due to different emission conditions or biogenic effects (e.?g. as a result of increasing nitrogen depositions). Compared to other environmental monitoring and modelling programmes the moss surveys registered increasing concentrations of toxic metal elements between 1990 and 2005. Contrary to deposition measurements that exhibit a higher temporal resolution the moss surveys provide measurement data on a wide range of elements. Some of these elements are important with regard to human-toxicological aspects (e.?g. Hg, Sb, As, Al, V). The standardised biomonitoring of atmospheric pollution by mosses is an important link between the technical acquisition of depositions and the accumulation in biological material. To claim that the element concentrations in mosses and in the deposition should correlate to a high degree is not appropriate since both approaches are physically related but are not identical. The degree of correlation thereby depends on the boundary conditions of the physical processes, like regional and site-specific meteorological conditions within the accumulation period, the vertical and horizontal vegetation structure or land use conditions. Conclusions The moss surveys contribute to the heavy metal and multi-component model of CLRTAP because they prove on different spatial scales how air pollution control influences the accumulation of emitted substances in environmental subjects of protection like vegetation. If environmental monitoring is seen as a continuous task and the applied methodology works well as an early warning system then environmental policy is enabled to act in preventative sense and to pursue unexpected developments. No other environmental monitoring programme provides such a wide range of ecotoxically relevant elements measured as spatially dense as the case for the moss surveys. The spatial distribution of environmental information is an essential criterion for their usability in terms of political measures for the federal states and the federation. Recommendations and perspectives The Heavy Metals in Mosses Surveys are a positive example for environmental monitoring activities reaching across three spatial and administrative levels: regional (e.?g. federal state or natural landscape), nationwide (e.?g. Germany) and continental (e.?g. Europe). In Germany the harmonised and quality-controlled moss data are made available via an internet-based webGIS portal. Therefore the moss data may easily be accessed for environmental monitoring purposes and the control of environmental political actions. Hence, the monitoring of Heavy Metals by Mosses Surveys is an important task among the European environmental observations, which should be continued in future for scientific and political reasons in its current extent.     

Spatial assessment of fin whale hotspots and their association with krill within an important Antarctic feeding and fishing ground

Fin whale (Balaenoptera physalus quoyi) habitat use and its relationship to environmental conditions are generally unknown in the Southern Ocean, presenting challenges for predicting their seasonal occurrence and potential effects of fishing pressure and climate change on this endangered species. Using biological data collected during 14 shipboard surveys off the northern Antarctic Peninsula and oceanographic data from satellite remote sensing, we mapped the distribution of fin whale hotspots, Antarctic krill abundance (biomass from acoustics, concentrations from nets) and ocean conditions during mid- and late-summer to investigate the environmental determinants of whale hotspots. Generalized additive models (GAM) were used to test the hypothesis that intra-seasonal changes in fin whale hotspot distribution relate to sea surface temperature (SST), krill abundance and eddy kinetic energy (EKE). More whale hotspots (sightings and individuals) are observed during late- than mid-summer surveys. During mid-summer, hotspots occurred near Elephant Island while in late-summer they were distributed throughout the slope region in proximity to the mean location of the southern Antarctic Circumpolar Current Front. The spatial mean of EKE did not differ between mid- and late-summer surveys, but the spatial mean of SST was significantly warmer during late-summer. The GAM for mid-summer indicates that fin whale hotspots were positively related to SST, EKE and acoustically determined krill biomass. The GAM for late-summer indicates the hotspots were negatively related to net-based krill abundance and positively related to acoustic krill biomass and EKE. This study is important because environmental determinants of fin whale hotspots may be used as reference points for implementing future conservation plans for their recovering populations.     

Climate, habitat, and species interactions at different scales determine the structure of a Neotropical bat community

Climate, habitat, and species interactions are factors that control community properties (e.g., species richness, abundance) across various spatial scales. Usually, researchers study how a few properties are affected by one factor in isolation and at one scale. Hence, there are few multi-scale studies testing how multiple controlling factors simultaneously affect community properties at different scales. We ask whether climate, habitat structure, or insect resources at each of three spatial scales explains most of the variation in six community properties and which theory best explains the distribution of selected community properties across a rainfall gradient. We studied a Neotropical insectivorous bat ensemble in the Isthmus of Panama with acoustic monitoring techniques. Using climatological data, habitat surveys, and insect captures in a hierarchical sampling design we determined how much variation of the community properties was explained by the three factors employing two approaches for variance partitioning. Our results revealed that most of the variation in species richness, total abundance, and feeding activity occurred at the smallest spatial scale and was explained by habitat structure. In contrast, climate at large scales explained most of the variation in individual species' abundances. Although each species had an idiosyncratic response to the gradient, species richness peaked at intermediate levels of precipitation, whereas total abundance was very similar across sites, suggesting density compensation. All community properties responded in a different manner to the factor and scale under consideration.     

Restoring piscivorous fish populations in the Laurentian Great Lakes causes seabird dietary change

Ecosystem change often affects the structure of aquatic communities thereby regulating how much and by what pathways energy and critical nutrients flow through food webs. The availability of energy and essential nutrients to top predators such as seabirds that rely on resources near the water's surface will be affected by changes in pelagic prey abundance. Here, we present results from analysis of a 25-year data set documenting dietary change in a predatory seabird from the Laurentian Great Lakes. We reveal significant declines in trophic position and alterations in energy and nutrient flow over time. Temporal changes in seabird diet tracked decreases in pelagic prey fish abundance. As pelagic prey abundance declined, birds consumed less aquatic prey and more terrestrial food. This pattern was consistent across all five large lake ecosystems. Declines in prey fish abundance may have primarily been the result of predation by stocked piscivorous fishes, but other lake-specific factors were likely also important. Natural resource management activities can have unintended consequences for nontarget ecosystem components. Reductions in pelagic prey abundance have reduced the capacity of the Great Lakes to support the energetic requirements of surface-feeding seabirds. In an environment characterized by increasingly limited pelagic fish resources, they are being offered a Hobsonian choice: switch to less nutritious terrestrial prey or go hungry.     

Space-time statistics for environmental and agricultural related phenomena

This paper presents an overview of space-time statistical procedures to analyse agricultural and environmental related phenomena. It starts with an application on root-rot development in cotton. Dependence modelling in space and time is done with the space-time variogram. Various kriging interpolators are presented for making predictions in space and time. Simulated annealing is used to design an optimal monitoring network for estimation of space-time variograms. In the application no clear indication was found for anisotropy, although strong evidence exists that the disease not only proceeds within rows but also jumps between rows. The optimal sampling scheme showed a spatial clustering of observations at the first and the last monitoring day and less observations at intermediate times.     

Recovery of insular seabird populations years after rodent eradication

Seabirds have been particularly affected by invasive non-native species, which has led to the implementation of numerous eradication campaigns for the conservation of these keystone and highly vulnerable species. Although the benefits of eradication of invasive non-native species for seabird conservation have been demonstrated, the recovery kinetics of different seabird populations on islands after eradication remains poorly evaluated. We conducted long-term monitoring of the number of breeding pairs of seven seabird species on a small atoll, Surprise Island, New Caledonia (southwestern tropical Pacific). Marine avifauna of the island were surveyed yearly 4 years before to 4 years after rodent eradication (conducted in 2005), and we conducted multiple one-time surveys from ∼10 years before and ∼15 years after eradication. We sought to determine how different seabird species responded to the eradication of invasive rodents in an insular environment. Three species responded positively (two- to 10-fold increase in population size) to eradication with differences in lag time and sensitivity. The number of breeding pairs increased (effect sizes = 0.49–0.95 and 0.35–0.52) for two species over 4 years post-eradication due to immigration. One species had a longer (at least 5 years) response time than all others; breeding pairs increased for over 10 years after eradication. Long-term sampling was necessary to observe the responses of the seabird populations on the island because of the delayed response of a species to eradication not visible in the first years after eradication. Our results confirmed the positive effects of eradication of invasive non-native species on seabirds and emphasize the importance of mid- and long-term pre- and posteradication surveys to decipher the mechanisms of seabird recovery and confirm the benefits of eradication for conservation purposes.     

Bioakkumulation von Metallen und Stickstoff zwischen 1990 und 2005 in Niedersachsen

Background, aim, and scope Since 1990 the UN ECE Heavy Metals in Mosses Surveys provide data inventories of the atmospheric heavy metal bioaccumulation across Europe. In the survey 2005 the nitrogen accumulation was measured for the first time in most of the participating countries. In Germany, the surveys were conducted in close cooperation of the relevant authorities of both the Federal Republic and the sixteen states. Therefore, statistical evaluations of the moss survey data with regard to the whole German territory and single federal states are of interest. This article concentrates on Lower Saxony, dealing with the mapping of the spatiotemporal trends of metal accumulation from 1990 to 2005, the spatial patterns of nitrogen accumulation in 2005, and the spatial variability of bioaccumulation due to characteristics of the sampling sites and their surroundings. Materials and methods The bioaccumulation of up to 40 trace elements and nitrogen in mosses was determined according to a Europe-wide harmonised methodology. The according experimental protocol regulates the selection of sampling sites and moss species, the chemical analysis and quality control and the classification of the measured values for mapping spatial patterns. In Lower Saxony all sampling sites were described with regard to topographical and ecological characteristics and several criteria to be fulfilled according to the guideline. Together with the measurements this metadata was combined with other information regarding land use in the surroundings of the sampling sites in the WebGIS MossMet. The spatial structure of the metal bioaccumulation was analysed and modelled by variogram analyses and then mapped by applying different Kriging techniques. Furthermore, multi metal indices (MMI) were derived for both the sampling sites and raster maps with help of percentile statistics: The MMI_1990–2005 was calculated for As, Cd, Cr, Cu, Fe, Ni, Pb, Ti, V and Zn. The statistical association of the metal and nitrogen bioaccumulation, site specific characteristics as well as information on land use and emissions was analysed by bivariate nonparametric correlation analysis, contingency tables and Classification and Regression Trees (CART). Results The results of the quality controlled chemical analyses shows a significant decrease of the metal bioaccumulation in Germany from 1990 to 2000 for all elements but Zn. From 2000 to 2005 a further significant decrease can be stated for Cd, Hg and Pb, to most parts non significant increases can be observed for Cr, Cu, Fe, Sb and Zn. Cr thereby exhibits the highest accumulation in 2005 when compared to the results of 1990, 1995 and 2000. The MMI illustrates the temporal trend of the metal bioaccumulation as a whole: From 1990 to 2000 a continuous significant decrease can be observed. From 2000 to 2005 the median of the MMI increases, again significantly, from 3.4 to 4. The N concentration in mosses in Lower Saxony reaches from 1.1 to 1.9?% in dry mass. High N concentrations were detected in agriculturally intensively used areas. Highly significant bivariate correlations between the metal bioaccumulation and land use in the surroundings of the sampling sites were found reaching from 0.3 to 0.5. Other location criteria with similar correlation coefficients/Cramér’s V are moss species, altitude, distance to the North and Baltic Sea and the distance of the sampling site to the nearest tree crown. N only shows negative correlations to urban land use and the distance to the nearest tree. Exemplified for Sb multivariate correlations were furthermore detected by CART. It could be shown that the Sb bioaccumulation interacts with the moss species and the ratio of agriculture, forests and urban areas around the sampling site. Discussion The decrease of the continuously decrease of heavy metals reflects the improving air quality in the past 15 years. Compared to other environmental monitoring and modelling programmes the moss surveys registered increasing concentrations of toxic metal elements between 1990 and 2005, e.?g. Cr. High Cr loads in mosses were also registered in other European countries like in Switzerland. Further investigations are therefore necessary to investigate whether this is due to different emission conditions or biogenic effects (e.?g. as a result of increasing nitrogen depositions). Contrary to deposition measurements that exhibit a higher temporal resolution the moss surveys provide measurement data on a wide range of elements. Some of these elements are important with regard to human-toxicological aspects (e.?g. As, Al, Hg, Sb, V). Due to its ecotoxicological relevance nitrogen was monitored in the European moss survey 2005 for the first time. Compared to the metals regionally high emissions of nitrogen compounds into the atmosphere can be detected in Lower Saxony. The standardised biomonitoring of atmospheric pollution with mosses is an important link between the technical acquisition of depositions and the accumulation in biological material. To claim that the element concentrations in mosses should correlate to a high degree with measured or modelled depositions is not appropriate since these approaches are considering different biological or physical receptors. Nevertheless, the accumulation of air pollutants in terricolous mosses reflects the degree of air pollution which is permanently deposited and affects the system of plants and soils. The degree of correlation thereby depends on the boundary conditions of the physical processes, like regional and site-specific meteorological conditions within the accumulation period, the vertical and horizontal vegetation structure or land use conditions. Conclusions The moss surveys contribute to the heavy metal and the multi-component-model of CLRTAP because they prove on different spatial scales how air pollution control influences the accumulation of emitted substances in environmental subjects of protection like vegetation incl. arable crops. If environmental monitoring is seen as a continuous task and the applied methodology works well as an early warning system then environmental policy is enabled to act in preventative sense and to pursue unexpected developments. No other environmental monitoring programme provides such a wide range of ecotoxicologically relevant elements measured as spatially dense as the case for the moss surveys. The spatial distribution of environmental information is an essential criterion for their usability in terms of political measures for the federal states and the federation. Recommendations and perspectives Heavy Metals in Mosses Surveys are a positive example for environmental monitoring activities reaching across three spatial and administrative levels: regional (e.?g. federal state or natural landscape), nation wide (e.?g. Germany) and continental (e.?g. Europe). In Germany the harmonised and quality controlled moss data are made available via a WebGIS portal. Therefore the moss data may easily be accessed for environmental monitoring purposes and the control of environmental political actions. Hence, the continuous task of environmental monitoring can be met and carried on in the future.