The Differential Absorption Lidar (DIAL) technique is one of the most effective methods for detecting atmospheric gases. It is based on the interaction between laser-emitted light and atmospheric molecules. The backscattered optical signal is converted into an electrical signal using photomultiplier tubes or other types of detectors. Two main detection approaches are commonly used: analog detection and photon-counting detection. While the analog mode is widely employed, it suffers from limited sensitivity. The photon-counting mode, although more suitable for detecting extremely weak signals, faces challenges in daytime measurements due to strong solar background noise. The main objective of this study is to evaluate the performance of the photon-counting technique to enable the DIAL system to detect extremely weak optical signals. To this end, modeling and simulation of the parameters influencing system performance have been carried out. Furthermore, the impact of using ultra-narrow band filter (UNBF) has been investigated and compared to that of conventional interference filter, with the aim of reducing background noise in daytime measurements and improving the transmission of the useful signal. The results show that the photon counting acquisition technique for a DIAL system or P-DIAL (Photon-counting DIAL) provides superior performance in terms of signal quality and measurement accuracy compared to analogue detection using an UNBF for noise limitation.
Abstract Conservation funding is currently limited; cost‐effective conservation solutions are essential. We suggest that the thousands of field stations worldwide can play key roles at the frontline of biodiversity conservation and have high intrinsic value. We assessed field stations’ conservation return on investment and explored the impact of COVID‐19. We surveyed leaders of field stations across tropical regions that host primate research; 157 field stations in 56 countries responded. Respondents reported improved habitat quality and reduced hunting rates at over 80% of field stations and lower operational costs per km2 than protected areas, yet half of those surveyed have less funding now than in 2019. Spatial analyses support field station presence as reducing deforestation. These “earth observatories” provide a high return on investment; we advocate for increased support of field station programs and for governments to support their vital conservation efforts by investing accordingly.
Amphibians are experiencing severe population declines, requiring targeted conservation action for the most threatened species and habitats. Unfortunately, we do not know the basic demographic traits of most species, which hinders population recovery efforts. We studied one of Madagascar’s most threatened frog species, the harlequin mantella (Mantella cowanii), to confirm it is still present at historic localities and estimate annual survival and population sizes. We surveyed eleven of all thirteen known localities and were able to detect the species at eight. Using a naïve estimate of detection probability from sites with confirmed presence, we estimated 1.54 surveys (95% CI [1.10–2.37]) are needed to infer absence with 95% confidence, suggesting the three populations where we did not detect M. cowanii are now extirpated. However, we also report two new populations for the first time. Repeated annual surveys at three sites showed population sizes ranged from 13–137 adults over 3–8 years, with the most intensively surveyed site experiencing a >80% reduction in population size during 2015–2023. Annual adult survival was moderately high (0.529–0.618) and we recaptured five individuals in 2022 and one in 2023 first captured as adults in 2015, revealing the maximum lifespan of the species in nature can reach 9 years and beyond. Our results confirm M. cowanii is characterized by a slower life history pace than other Mantella species, putting it at greater extinction risk. Illegal collection for the international pet trade and continued habitat degradation are the main threats to the species. We recommend conservation efforts continue monitoring M. cowanii populations and reassess the International Union for Conservation of Nature (IUCN) Red List status because the species may be Critically Endangered rather than Endangered based on population size and trends.
Furcifer labordi est une espèce de caméléons uniquement connue dans quelques localités de la partie occidentale de Madagascar. Son aire de distribution est restreinte entre les fleuves Tsiribihina et Fiherenana. Nous avons réalisé des recherches pour comprendre sa distribution écologique et spatiale dans la Reserve Spéciale d’Andranomena. Des investigations ont été menées dans les habitats proche et loin de cours d’eau, à la lisière et l’intérieur de la forêt et dans la forêt relativement intacte et celle en régénération. Nos résultats ont révélé que cette espèce se répartit uniformément dans les différents types d’habitats. Autrement dit, sa distribution horizontale n’est pas influencée ni par la dégradation de l’habitat, ni par le cours d’eau. La couverture de la canopée et la repartition des plantes selon la hauteur de l’extérieur vers l’itérieur de la forêt sont des paramètres qui influencent cette distribution horizontale. Les oiseaux (six espèces) et les serpents (quatre espèces) prédateurs ne provoquent pas de perturbation sur F. labordi et n’influencent pas sa distribution horizontale. Cette dernière n’est pas aussi influencée par l’abondance en insectes disponibles. La hauteur du perchoir utilisé varie beaucoup, elle n’est pas cependant liée, ni à la classe d’âge ni au sexe. F. labordi ne présente en général aucune préférence particulière quant au choix de plante utilisée comme perchoir. Il en est de même pour la hauteur et les DHP de plantes perchoirs. L’espèce emploie similairement les parties des plantes disponibles et ne présente pas de préférence particulière. Toutes les classes d’âges ont été observées et ne présentent pas de préférence particulière en terme de types d’habitats. Nos résultats suggèrent que la répartition restreinte de cette espèce pourrait être dû à la disparition de son habitat. Furcifer labordi is a species of chameleon only known from a few localities in the western part of Madagascar. Its distribution area is restricted between the Tsiribihina and Fiherenana rivers. We carried out research to understand its ecological and spatial distribution in the Andranomena Special Reserve. Investigations were carried out in habitats near and far from watercourses, at the edge and interior of the forest and in relatively intact and regenerating forest. Our results revealed that this species is evenly distributed across different habitat types. In other words, its horizontal distribution is not influenced either by habitat degradation or by the watercourse. The cover of the canopy and the distribution of plants according to height from the outside to the inside of the forest are parameters that influence this horizontal distribution. Predatory birds (six species) and snakes (four species) do not cause any disturbance to F. labordi and do not influence its horizontal distribution. The latter is not as influenced by the abundance of available insects. The height of the perch used varies a lot, however it is not linked to age class or sex. F. labordi generally shows no particular preference regarding the choice of plant used as a perch. The same goes for the height and DBH of perching plants. The species uses available plant parts similarly and shows no particular preference. All age classes were observed and do not show any particular preference in terms of habitat types. Our results suggest that the restricted distribution of this species could be due to the disappearance of its habitat.
Many studies on reptiles have been conducted across Madagascar but some areas are poorly known in terms of the diversity of reptiles such as the Bobaomby Complex in the northern tip of Madagascar. In February and March 2018, we conducted a biodiversity survey within five sites. This biological survey is to collect scientific information for helping new protected creations. Three main methods were used including pitfall trap, visual and acoustic searching along the transect and refuge examination. In total, we recorded 42 species including 5 chameleons, 8 skinks, 11 geckos, 16 snakes and 2 blinds snake species. All recorded species are endemic to Madagascar except Hemidactylus frenatus, Ebenavia inunguis and Phelsuma abbotti. Rare species known only from a few specimens have been recorded in the Bobaomby Complex: Heteroliodon fohy, Pseudoxyrhopus ambreensis, and Madascincus arenicola. Thirteen species are classified as threatened on the IUCN Red List, of which three are Critically Endangered: Paracontias minimus, Madascincus arenicola, and Paroedura lohatsara; three are Endangered: Heteroliodon fohy, Lycodryas inopinae, and Phisalixella variabilis; and seven are Vulnerable: Brookesia ebenaui, Furcifer petteri, Blaesodactylus boivini, Uroplatus ebenaui, Uroplatus henkeli, Liophidium therezieni and Flexiseps ardouini. Our results reveal the importance of the Bobaomby Complex for conserving reptile diversity and highlight the need to protect it.
