•Acoustic identification allows echolocating bats to be surveyed non-invasively.•Automated classifiers of bat calls promise high identification performances.•Use of classifiers is spreading yet they ...have not been tested enough in the field.•Misidentification may ultimately lead to wrong management and serious conservation issues.•Thorough field tests are needed to assess limitations and strengths of these tools.
Bats are a species-rich order of mammals providing key ecosystem services. Because bats are threatened by human action and also serve as important bioindicators, monitoring their populations is of utmost importance. However, surveying bats is difficult because of their nocturnal habits, elusiveness and sensitivity to disturbance. Bat detectors allow echolocating bats to be surveyed non-invasively and record species that would otherwise be difficult to observe by capture or roost inspection. Unfortunately, several bat species cannot be identified confidently from their calls so acoustic classification remains ambiguous or impossible in some cases.
The popularity of automated classifiers of bat echolocation calls has escalated rapidly, including that of several packages available on purchase. Such products have filled a vacant niche on the market mostly in relation to the expanding monitoring efforts related to the development of wind energy production worldwide.
We highlight that no classifier has yet proven capable of providing correct classifications in 100% of cases or getting close enough to this ideal performance. Besides, from the literature available and our own experience we argue that such tools have not yet been tested sufficiently in the field. Visual inspection of calls whose automated classification is judged suspicious is often recommended, but human intervention a posteriori represents a circular argument and requires noticeable experience.
We are concerned that neophytes – including consultants with little experience with bats but specialized into other taxonomical groups – will accept passively automated responses of tools still awaiting sufficient validation. We remark that bat call identification is a serious practical issue because biases in the assessment of bat distribution or habitat preferences may lead to wrong management decisions with serious conservation consequences. Automated classifiers may crucially aid bat research and certainly merit further investigations but the boost in commercially available software may have come too early. Thorough field tests need to be carried out to assess limitations and strengths of these tools.
The threats facing Ecuador's Yasuní National Park are emblematic of those confronting the greater western Amazon, one of the world's last high-biodiversity wilderness areas. Notably, the country's ...second largest untapped oil reserves--called "ITT"--lie beneath an intact, remote section of the park. The conservation significance of Yasuní may weigh heavily in upcoming state-level and international decisions, including whether to develop the oil or invest in alternatives.
We conducted the first comprehensive synthesis of biodiversity data for Yasuní. Mapping amphibian, bird, mammal, and plant distributions, we found eastern Ecuador and northern Peru to be the only regions in South America where species richness centers for all four taxonomic groups overlap. This quadruple richness center has only one viable strict protected area (IUCN levels I-IV): Yasuní. The park covers just 14% of the quadruple richness center's area, whereas active or proposed oil concessions cover 79%. Using field inventory data, we compared Yasuní's local (alpha) and landscape (gamma) diversity to other sites, in the western Amazon and globally. These analyses further suggest that Yasuní is among the most biodiverse places on Earth, with apparent world richness records for amphibians, reptiles, bats, and trees. Yasuní also protects a considerable number of threatened species and regional endemics.
Yasuní has outstanding global conservation significance due to its extraordinary biodiversity and potential to sustain this biodiversity in the long term because of its 1) large size and wilderness character, 2) intact large-vertebrate assemblage, 3) IUCN level-II protection status in a region lacking other strict protected areas, and 4) likelihood of maintaining wet, rainforest conditions while anticipated climate change-induced drought intensifies in the eastern Amazon. However, further oil development in Yasuní jeopardizes its conservation values. These findings form the scientific basis for policy recommendations, including stopping any new oil activities and road construction in Yasuní and creating areas off-limits to large-scale development in adjacent northern Peru.
Over recent years, it became widely accepted that alternative, renewable energy may come at some risk for wildlife, for example, when wind turbines cause large numbers of bat fatalities. To better ...assess likely populations effects of wind turbine related wildlife fatalities, we studied the geographical origin of the most common bat species found dead below German wind turbines, the noctule bat (Nyctalus noctula). We measured stable isotope ratios of non-exchangeable hydrogen in fur keratin to separate migrants from local individuals, used a linear mixed-effects model to identify temporal, spatial and biological factors explaining the variance in measured stable isotope ratios and determined the geographical breeding provenance of killed migrants using isoscape origin models. We found that 72% of noctule bat casualties (n = 136) were of local origin, while 28% were long-distance migrants. These findings highlight that bat fatalities at German wind turbines may affect both local and distant populations. Our results indicated a sex and age-specific vulnerability of bats towards lethal accidents at turbines, i.e. a relatively high proportion of killed females were recorded among migratory individuals, whereas more juveniles than adults were recorded among killed bats of local origin. Migratory noctule bats were found to originate from distant populations in the Northeastern parts of Europe. The large catchment areas of German wind turbines and high vulnerability of female and juvenile noctule bats call for immediate action to reduce the negative cross-boundary effects of bat fatalities at wind turbines on local and distant populations. Further, our study highlights the importance of implementing effective mitigation measures and developing species and scale-specific conservation approaches on both national and international levels to protect source populations of bats. The efficacy of local compensatory measures appears doubtful, at least for migrant noctule bats, considering the large geographical catchment areas of German wind turbines for this species.
Artificial light at night is spreading worldwide at unprecedented rates, exposing strictly nocturnal animals such as bats to a novel anthropogenic stressor. Previous studies about the effect of ...artificial light on bats focused almost exclusively on non-migratory species, yet migratory animals such as birds are known to be largely affected by light pollution. Thus, we conducted a field experiment to evaluate if bat migration is affected by artificial light at night. In late summer, we presented artificial green light of 520 nm wavelength to bats that were migrating south along the shoreline of the Baltic Sea. Using a light on-off treatment, we observed that the activity of Pipistrellus nathusii and P. pygmaeus, the two most abundant migratory species at our site, increased by more than 50% in the light-on compared to the light-off treatment. We observed an increased number of feeding buzzes during the light-on compared to the light-off treatment for P. nathusii. However, feeding activity was low in general and did not increase disproportionately during the light-on treatment in relation to the overall echolocation call activity of bats. Further, P. nathusii were attracted towards the green light at a distance of about 23 m, which is way beyond the echolocation detection range for insects of Nathusius' bats. We therefore infer that migratory bats were not attracted to artificial green light because of high insect densities, but instead by positive phototaxis. We conclude that artificial light at night may potentially impact bat migration in a yet unrecognized way.
Damaraland mole rats (Fukomys damarensis) are cooperatively breeding, subterranean mammals that exhibit a high reproductive skew. Reproduction is monopolised by the dominant female of the group, ...whereas subordinates are physiologically suppressed to the extent that they are anovulatory. In these latter animals, it is assumed that normal gonadotropin‐releasing hormone secretion from the hypothalamus is disrupted. The RFamide peptides kisspeptin (Kiss1) and RFamide‐related peptide‐3 (RFRP‐3) are considered as potent regulators of gonadotropin release. To assess whether these neuropeptides are involved in the mechanism of reproductive suppression, we investigated the distribution and gene expression of Kiss1 and Rfrp by means of in situ hybridisation in wild‐caught female Damaraland mole‐rats with different reproductive status. In both reproductive phenotypes, substantial Kiss1 expression was found in the arcuate nucleus and only few Kiss1‐expressing cells were detected in the anteroventral periventricular nucleus (AVPV), potentially as a result of low circulating oestradiol concentrations in breeding and nonbreeding females. Rfrp gene expression occurred in the dorsomedial nucleus, the paraventricular nucleus and the periventricular nucleus. While in female breeders and nonbreeders, plasma oestradiol levels were low and not significantly different, quantification of the hybridisation signal for both genes revealed significant differences in relation to reproductive status. Reproductively active females had more Kiss1‐expressing cells and a higher number of silver grains per cell in the arcuate nucleus compared to nonreproductive females. This difference was most pronounced in the caudal part of the nucleus. No such differences were found in the AVPV. Furthermore, breeding status was associated with a reduced number of Rfrp‐expressing cells in the anterior hypothalamus. This reproductive status‐dependent expression pattern of Kiss1 and Rfrp suggests that both neuropeptides play a role in the regulation of reproduction in Damaraland mole‐rats. Enhanced long‐term negative feedback effects of oestradiol could be responsible for the lower Kiss1 expression in the arcuate nucleus of reproductively suppressed females.
Evidence is accumulating that insects are frequently killed by operating wind turbines, yet it is poorly understood if these fatalities cause population declines and changes in assemblage structures ...on various spatial scales. Current observations suggest that mostly hill‐topping, swarming, and migrating insects interact with wind turbines. Recently, the annual loss of insect biomass at wind turbines was estimated for Germany to amount 1,200 t for the plant growth period, which equates to about 1.2 trillion killed insects per year, assuming 1 mg insect body mass. Accordingly, a single turbine located in the temperate zone might kill about 40 million insects per year. Furthermore, Scheimpflug Lidar measurements at operating wind turbines confirm a high insect activity in the risk zone of turbines. These numbers and observations are alarming, yet they require further consolidation, particularly across all continents and climate zones where wind energy industry is expanding. We need to understand (a) how attraction of insects to wind turbines affect fatality rates and interactions of insect predators with wind turbines. (b) We have to connect insect fatalities at wind turbines with source populations and evaluate if these fatalities add to the decline of insect populations and potentially the extinction of species. (c) We need to assess how fatalities at wind turbines change insect‐mediated ecosystem services. An ever‐growing global wind energy industry with high densities of wind turbines may have long‐lasting effects on insects and associated trophic links if negative impacts on insects are not considered during the erection and operation of wind turbines.
We develop an idealized, physically based model describing combined effects of ice nucleation and sublimation on ice crystal number during persistent contrail formation. Our study represents the ...first effort to predict ice numbers at the point where contrails transition into contrail cirrus—several minutes past formation—by connecting them to aircraft soot particle emissions and atmospheric supersaturation with respect to ice. Results averaged over an observed exponential distribution of ice supersaturation (mean value 15%) indicate that large reductions in soot particle numbers are needed to lower contrail ice crystal numbers significantly for soot emission indices around 1015 (kg fuel)−1, because reductions in nucleated ice number are partially compensated by sublimation losses. Variations in soot particle (−50%) and water vapor (+10%) emission indices at threefold lower soot emissions resulting from biofuel blending cause ice crystal numbers to change by −35% and <5%, respectively. The efficiency of reduction depends on ice supersaturation and the size distribution of nucleated ice crystals in jet exhaust plumes and on atmospheric ice supersaturation, making the latter another key factor in contrail mitigation. We expect our study to have important repercussions for planning airborne measurements targeting contrail formation, designing parameterization schemes for use in large‐scale models, reducing uncertainties in predicting contrail cirrus, and mitigating the climate impact of aviation.
Plain Language Summary
The formation and modification of ice crystals in persistent aircraft condensation trails (contrails) is an important component in evaluating the climate impact of aviation. We connect for the first time contrail ice numbers at the end of the formation stage to aircraft soot emissions and atmospheric ice supersaturation. We offer a framework to estimate changes in ice number and to compare effects of mitigation options. Our results show that large reductions in soot emissions are required to lower contrail ice numbers significantly, and those ice numbers are insensitive to small variations of the amount of water vapor emitted by aircraft jet engines. Our study has important implications for planning field measurements, reducing uncertainties in numerical predictions of contrail cirrus effects on climate and for mitigating this impact.
Key Points
First study to link ice crystal nucleation and sublimation in the contrail formation stage at the process level
Small variations in soot particle and water vapor emissions do not affect initial ice crystal numbers strongly
Conceptual framework useful to compare effects of mitigation options targeting contrail ice formation
In order to deal with the current, dramatic decline in biodiversity, the public at large needs to be aware of and participate in biodiversity research activities. One way to do this is citizen ...science projects, in which researchers collaborate with volunteering citizens in scientific research. However, it remains unclear whether engaging in such projects has an impact on the learning outcomes of volunteers. Previous research has so far presented mixed results on the improvement of citizens' attitudes and knowledge, mostly because such research has focused only on single aspects of citizen science projects in case studies. To address these limitations, we investigated the impact of an urban bat ecology project on citizens' attitudes and knowledge about bats, and on their engagement with citizen science. We also examined whether the degree of citizen participation (i.e., collecting data vs. collecting and analyzing data) had an influence on the outcomes. We conducted four field studies and used a survey-based, experimental, pre-/post-measurement design. To vary the degree of participation, we assessed the post measurement in one group directly after data collection, whereas, in a second group, we assessed it after data collection and analysis, at the end of the project. Across all studies, the results demonstrated that citizens' content knowledge of urban bat ecology increased, and their attitudes toward bats and toward their engagement in citizen science improved during their participation. Citizens' degrees of participation did not influence these outcomes. Thus, our research illustrates that citizen science can increase awareness of urban bat conservation, independently of citizens' degree of participation. We discuss the implications of our findings for the citizen science community.
The COVID‐19 pandemic led to a 72% reduction of air traffic over Europe in March–August 2020 compared to 2019. Modeled contrail cover declined similarly, and computed mean instantaneous radiative ...contrail forcing dropped regionally by up to 0.7 W m−2. Here, model predictions of cirrus optical thickness and the top‐of‐atmosphere outgoing longwave and reflected shortwave irradiances are tested by comparison to Meteosat‐SEVIRI‐derived data. The agreement between observations and modeled data is slightly better when modeled contrail cirrus contributions are included. The spatial distributions and diurnal cycles of the differences in these data between 2019 and 2020 are partially caused by differences in atmospheric and surface conditions, particularly for solar radiation in the spring of 2020. Aviation signals become discernible in the observed differences of these data between 2019 and 2020 when subtracting numerical weather prediction model results that approximate the atmosphere and surface conditions without contrails.
Plain Language Summary
Aircraft flying in cold and humid air masses induce contrails which warm the Earth‐atmosphere system by reducing the terrestrial radiation out into space and cool by increasing the Earth’s albedo. Previous studies found that the warming effects dominate and that contrails may contribute most of the present radiative forcing of climate change induced by aviation. The COVID‐19 pandemic led to a worldwide and long‐duration reduction of air traffic. This paper compares model predictions and satellite‐observed cirrus properties and irradiances over Europe for 6 months in 2019 and 2020. The models account for changes in the atmosphere and at the Earth’s surface in the two half‐years. Model and observation results show about 90% correlation and 20% mean normalized deviations. The agreement between observed and modeled optical cirrus thickness and terrestrial irradiances improves slightly when the modeled contrail cirrus contributions are included. Solar radiation changes show a larger variability because of large changes in the lower atmosphere and at the Earth surface. Since worldwide traffic activity has stayed at low levels after August 2020, the comparisons may be extended. Further model studies, including the effects of other emissions, are needed for a more comprehensive understanding of the observed changes.
Key Points
Air traffic reduction during the COVID‐19 pandemic is used for testing aviation contrail cirrus and related radiative forcing modeling
Cirrus optical depth and top‐of‐atmosphere irradiances from satellite observations and model results show reasonable correlations
Aviation contrail signatures are identifiable in spite of strongly different atmosphere and surface conditions in 2019 and 2020
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