High Dynamic Range in Entomological Scheimpflug Lidars
TL;DR: In this article, the authors report count rates of 104 insects/minute up to 2 km range and demonstrate that smaller insects can be detected further away by long exposures and show consistency between the captured biomass size spectra.
Abstract: Minimizing insecticide use, preventing vector diseases and facilitating biodiversity assessments are suitable applications of recent advances in photonic insect surveillance and entomological lidar. The tools also comprise a new window into fundamental aspect of the fascinating life and ecology of insects and their predators in situ . At the same time, it is evident that lidars are subject to finite detection range given by the instrument noise and saturation levels, and therefore, intervals of the biomass spectra are sectioned at different ranges. The Scheimpflug lidar allows an interesting trade-off between high sample rate and low pulse energy for retrieving wing beat harmonics and slow sample rates with high pulse energy for detecting small species far away. In this paper, we review and revise calibration, sizing and associated deficiencies, and report count rates to 104 insects/minute up to 2 km range. We investigate if and how high dynamic range can be exploited in entomological lidar and also how fast and slow sample rates could complement each other and capture a wider span of the biomass spectrum. We demonstrate that smaller insect can be detected further away by long exposures and show consistency between the captured biomass size spectra. However, we find unexpected discrepancies between short and long exposures in the range distributions. We found that vertebrates as well as specular insects can saturate signals. Error sources and limitations are elaborated on.
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TL;DR: In this article , a compact, inexpensive hyperspectral fluorescence lidar was constructed based on off-the-shelf components and 3D printing, which can efficiently monitor several tagged insects in parallel for comparative ecological analysis.
Abstract: Insects play crucial roles in ecosystems, and how they disperse within their habitat has significant implications for our daily life. Examples include foraging ranges for pollinators, as well as the spread of disease vectors and pests. Despite technological advances with radio tags, isotopes, and genetic sequencing, insect dispersal and migration range remain challenging to study. The gold standard method of mark-recapture is tedious and inefficient. This paper demonstrates the construction of a compact, inexpensive hyperspectral fluorescence lidar. The system is based on off-the-shelf components and 3D printing. After evaluating the performance of the instrument in the laboratory, we demonstrate its efficient range-resolved fluorescence spectra in situ. We present daytime remote ranging and fluorescent identification of auto-powder-tagged honey bees. We also showcase range-, temporally- and spectrally-resolved free-flying mosquitoes, which were tagged through feeding on fluorescent-dyed sugar water. We conclude that violet light can efficiently excite administered sugar meals imbibed by flying insects. Our field experiences provide realistic expectations of signal-to-noise levels, which can be used in future studies. The technique is generally applicable and can efficiently monitor several tagged insect groups in parallel for comparative ecological analysis. This technique opens up a range of ecological experiments, which were previously unfeasible.
6 citations
TL;DR: In this article , the authors discuss some features of open-path remote sensing inherent to CW range-resolved S-lidars (S comes from Scheimpflug) as a new, to the best of our knowledge, and promising class of laser instruments for environmental monitoring.
Abstract: In this paper, we discuss some features of open-path remote sensing inherent to CW range-resolved S-lidars (S comes from Scheimpflug) as a new, to the best of our knowledge, and promising class of laser instruments for environmental monitoring. In many remote-sensing applications, the accompanying skylight can degrade the sensitivity and overload the photodetectors, which is also very relevant for S-lidars with Si and InGaAs arrays. We paid special attention to the topical problem of predicting the limitations and potential of S-lidars in the VIS and SWIR spectral bands, where the sky background is particularly strongly affected. For this purpose, the index of immunity against external backgrounds as a quantitative indicator of S-lidars' potential insensitivity to the current skylight is introduced. Its evaluation is carried out by comparing the potentially achievable signal-to-noise ratios at the detector output in the presence and absence of external illumination. The detector response to the skylight in the photon-counting mode is normalized to appropriate parameters of the array in order to use dimensionless estimates in describing the variability of conditions. Characteristic spectral and dark-current-related features distinguishing the response of Si and InGaAs array detectors in the presence of background illumination are taken into account. It is then shown how to determine the minimum required full well capacity of the array in order to neglect the skylight contribution and ensure stable operation of S-lidars. The proposed methodology is aimed at providing a rationale for design solutions to expand the applicability of this promising type of remote sensors.
2 citations
TL;DR: In this article , a hyperspectral lidar with 64 spectral bands based on a supercontinuum light source using ray-tracing and 3D printing is developed to detect free-flying insects and their wingbeats.
Abstract: Monitoring insects of different species to understand the factors affecting their diversity and decline is a major challenge. Laser remote sensing and spectroscopy offer promising novel solutions to this. Coherent scattering from thin wing membranes also known as wing interference patterns (WIPs) have recently been demonstrated to be species specific. The colors of WIPs arise due to unique fringy spectra, which can be retrieved over long distances. To demonstrate this, a new concept of infrared (950–1650 nm) hyperspectral lidar with 64 spectral bands based on a supercontinuum light source using ray-tracing and 3D printing is developed. A lidar with an unprecedented number of spectral channels, high signal-to-noise ratio, and spatio-temporal resolution enabling detection of free-flying insects and their wingbeats. As proof of principle, coherent scatter from a damselfly wing at 87 m distance without averaging (4 ms recording) is retrieved. The fringed signal properties are used to determine an effective wing membrane thickness of 1412 nm with ±4 nm precision matching laboratory recordings of the same wing. Similar signals from free flying insects (2 ms recording) are later recorded. The accuracy and the method's potential are discussed to discriminate species by capturing coherent features from free-flying insects.
1 citations
TL;DR: In this article , the performance of S-lidars with Si/InGaAs arrays was analyzed under conditions of wide variability of optical weather and sky background brightness. But the authors focused on the performance analysis of the S-Lidar instrument and the external background source, taking into account their wide variability.
Abstract: The article proposes a methodology for analyzing the performance of S-lidars (S comes from Scheimpflug) as a new class of environmental remote sensors operating under conditions of wide variability of optical weather and sky background brightness. The novelty of the problem statement, the methods used and the results obtained are determined by their application to laser sensing systems with unconventional design principles and the consequent need to revise the traditional ways of assessing their potential capabilities. The research method is based on a dimensionless-parametric approach, which allows comparing phenomena and systems of different scales and combining complementary characteristics and parameters. Effects of the dimensionless optical weather factor on lidar potential are shown being investigated under various environmental conditions, from the clear atmosphere through haze and mist to fog when probing in Vis/SWIR spectral bands and using Si/InGaAs detector arrays. It is shown exactly how and to what extent the significant differences in their spectral sensitivity and internal noise parameters are susceptible to the wide spectral and energy variability of the sky background brightness observed at very different angles to the Sun. A detailed analysis of the two most important influencing factors within the system, “S-Lidar instrument + Optical weather + External background source”, taking into account their wide variability, allowed us to describe their joint nonlinear influence and, thus, to anticipate the imposed limitations. The proposed dimensionless-parametric concept for predicting the potential capabilities of S-lidars with Si/InGaAs arrays is aimed at expanding applications of this rapidly developing class of remote sensors in a wide variety of environments.
TL;DR: In this paper , the authors focus on real-time, laser-based monitoring methods that enable online monitoring of insect activity and study the response of insect populations to changes in environmental conditions such as weather.
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TL;DR: The results suggest that major drivers of arthropod decline act at larger spatial scales, and are associated with agriculture at the landscape level, which implies that policies need to address the landscape scale to mitigate the negative effects of land-use practices.
Abstract: Recent reports of local extinctions of arthropod species1, and of massive declines in arthropod biomass2, point to land-use intensification as a major driver of decreasing biodiversity. However, to our knowledge, there are no multisite time series of arthropod occurrences across gradients of land-use intensity with which to confirm causal relationships. Moreover, it remains unclear which land-use types and arthropod groups are affected, and whether the observed declines in biomass and diversity are linked to one another. Here we analyse data from more than 1 million individual arthropods (about 2,700 species), from standardized inventories taken between 2008 and 2017 at 150 grassland and 140 forest sites in 3 regions of Germany. Overall gamma diversity in grasslands and forests decreased over time, indicating loss of species across sites and regions. In annually sampled grasslands, biomass, abundance and number of species declined by 67%, 78% and 34%, respectively. The decline was consistent across trophic levels and mainly affected rare species; its magnitude was independent of local land-use intensity. However, sites embedded in landscapes with a higher cover of agricultural land showed a stronger temporal decline. In 30 forest sites with annual inventories, biomass and species number—but not abundance—decreased by 41% and 36%, respectively. This was supported by analyses of all forest sites sampled in three-year intervals. The decline affected rare and abundant species, and trends differed across trophic levels. Our results show that there are widespread declines in arthropod biomass, abundance and the number of species across trophic levels. Arthropod declines in forests demonstrate that loss is not restricted to open habitats. Our results suggest that major drivers of arthropod decline act at larger spatial scales, and are (at least for grasslands) associated with agriculture at the landscape level. This implies that policies need to address the landscape scale to mitigate the negative effects of land-use practices. Analyses of a dataset of arthropod biomass, abundance and diversity in grassland and forest habitats in Germany for the period 2008–2017 reveal that drivers of arthropod declines act at the landscape level.
625 citations
TL;DR: In a recent TREE article, Sutherland and colleagues used horizon scanning to identify fifteen emerging issues in biodiversity conservation, including invasive species, synthetic meat, nanosilver and microplastic pollution, but feel they overlooked an emerging problem of great importance and urgency, namely light pollution.
Abstract: In a recent TREE article, Sutherland and colleagues [1] used horizon scanning to identify fifteen emerging issues in biodiversity conservation. They discussed both threats and opportunities for a broad range of issues, including invasive species, synthetic meat, nanosilver and microplastic pollution. We recognize that the article was not intended to be comprehensive, but feel they overlooked an emerging problem of great importance and urgency, namely that of light pollution. Although the widespread use of artificial light at night has enhanced the quality of human life and is positively associated with security, wealth and modernity, the rapid global increase of artificial light has fundamentally transformed nightscapes over the past six decades, both in quantity (6% increase per year, range: 0–20%) and quality (i.e.
576 citations
TL;DR: Protective tree cover may allow earlier evening emergence of bats and therefore provide access to more food, and have implications for the conservation ofbats and their habitats particularly at high latitudes.
Abstract: The flight activity of three species of insectivorous bats and their prey was studied in north-east Scotland (57°N) during summer 1993. Aerial insects of sizes taken by bats were more abundant during the day than during the night, but the highest abundance usually occurred around dusk, partly reflecting increased flight of dipterans. In contrast, the flight activity of moths, mainly Geometridae and Pyralidae, was greatest around midnight. Two species of aerial-hawking bats, Pipistrellus pipistrellus and Myotis daubentonii, which feed primarily on small flying insects, mainly Diptera, emerged from their roosts 15-30 min after sunset, during or after the dusk peak in insect activity, and subsequently foraged as their food was declining in abundance. In contrast, the foliage gleaning bat Plecotus auritus, which feeds primarily on moths, did not emerge until about one hour after sunset, but while the activity of its main prey was increasing. The two aerial-hawking bats therefore seem to be constrained from exploiting most of the evening peak in aerial insect abundance, presumably because earlier emergence would result in higher predation risk at the higher light levels. P. auritus may have less to gain by emerging early, since it can feed on moths and non-flying prey independently of the activity of small insects at dusk. The conclusions have implications for the conservation of bats and their habitats particularly at high latitudes. Protective tree cover may allow earlier evening emergence of bats and therefore provide access to more food.
293 citations
TL;DR: A long-term study of the migration of large and small insects over the southern United Kingdom for a decade reveals a major transport process with implications for ecosystem services, processes, and biogeochemistry.
Abstract: Migrating animals have an impact on ecosystems directly via influxes of predators, prey, and competitors and indirectly by vectoring nutrients, energy, and pathogens. Although linkages between vertebrate movements and ecosystem processes have been established, the effects of mass insect “bioflows” have not been described. We quantified biomass flux over the southern United Kingdom for high-flying (>150 meters) insects and show that ~3.5 trillion insects (3200 tons of biomass) migrate above the region annually. These flows are not randomly directed in insects larger than 10 milligrams, which exploit seasonally beneficial tailwinds. Large seasonal differences in the southward versus northward transfer of biomass occur in some years, although flows were balanced over the 10-year period. Our long-term study reveals a major transport process with implications for ecosystem services, processes, and biogeochemistry.
236 citations
TL;DR: A pantropical dataset of 875 local species assemblages sampled in primary forest and 10 other land-use types previously converted from forest is compiled and analyzed, addressing the challenge of estimating global biodiversity losses that accrue with tropical deforestation.
Abstract: Tropical forests are incredibly biodiverse; they support at least two-thirds of the world’s biodiversity (1) despite covering less than 10% of Earth’s land surface (2). Unfortunately, prospects for tropical forests and the biodiversity therein are becoming increasingly bleak owing to unabated deforestation and forest alteration (3) that stem from human activities such as logging, hunting, agricultural expansion, and human settlement (4, 5) (Fig. 1). Previous studies have summarized how local or subregional biodiversity values differ across primary forests and other land-use types (6, 7), but it is unclear how site- and landscape-level impacts scale up globally. In PNAS, Alroy (8) addresses this challenge by compiling and analyzing a pantropical dataset of 875 local species assemblages sampled in primary forest and 10 other land-use types previously converted from forest.
Fig. 1.
Human activities that threaten tropical forests and the biodiversity therein. ( A ) Logging in Peninsular Malaysia. ( B ) Oil palm monoculture in Kalimantan, Indonesia. ( C ) Cattle grazing on pastures converted from forests in Mato Grosso, Brazil. ( D ) Smallholder cropping (of cassava) in Loreto, Peru. ( E ) Harvesting of wood for charcoal production in Benin. ( F ) Hunting threatens many forest species, including the Malayan tiger caught here on a camera trap in Peninsular Malaysia. Photographs courtesy of Rimba ( A and F ), X.G. ( B ), Jacob Socolar ( C and D ), and Orou Gaoue ( E ).
The task of estimating global biodiversity losses that accrue with tropical deforestation might seem straightforward at first. For example, one might approach this problem by collating global distributions of different taxa, removing increasing extents of forest, and then counting the extinctions that accumulate when entire species ranges become deforested. This approach suffers from a number of pitfalls. First, it assumes populations originally occurring in forests can never survive in altered habitats. Indeed, it is well documented that altered forests and other …
[↵][1]1Email: xgiam{at}utk.edu.
[1]: #xref-corresp-1-1
222 citations