Levels Of Anthropogenic Disturbance Research Articles

Intensified anthropogenic disturbances impair planktonic algae in an urban river

Anthropogenic activities have posed significant threats to water quality and aquatic organisms in urban rivers, yet the understanding of how planktonic and sedimentary algal communities respond to different levels of anthropogenic disturbances remains limited. To address this knowledge gap, we conducted a systematic investigation on the effects of three anthropogenic-disturbance levels (i.e., low in the upstream, moderate in the midstream, and high in the downstream reach) on algal communities in water and sediment of the Bahe River. Our results revealed that planktonic rather than sedimentary algae were more vulnerable to anthropogenic activities in the urban river. Notably, we found the lowest biodiversity and niche breadth of planktonic algae in the downstream subjected to the high anthropogenic stress. Furthermore, the lowest complexity and stability of co-occurrence patterns of planktonic algae as well as planktonic algae-bacteria were witnessed under the highest human disturbance. Anthropogenic activities, followed by physicochemical variables, geographical patterns, and bacteria co-occurring with algae, played essential roles in shaping the niche differentiation and community assembly of planktonic algae. This study suggested that anthropogenic disturbances (represented by nighttime light, gross domestic product, and impervious surface) can alter physiochemical conditions (such as nitrogen and phosphorus contents) and thereby damage algal compositions along the urban river, highlighting the importance of effective measures for mitigating the impacts of anthropogenic activities and protecting the ecological health of river systems.

Environmental conditions influencing the early colonization stage of Ludwigia hexapetala , an aquatic plant recently invasive in Italy

Freshwater ecosystems are among the most susceptible to biological invasions. The South American Ludwigia hexapetala is an aquatic plant that is becoming an increasing threat in many European waterbodies, recently including Italy. This study aimed to define the main parameters influencing the early colonization stage of L. hexapetala by overlapping the percentage cover of this species with environmental parameter data collected at 24 aquatic sites from six waterbodies in north-central Italy. At each site, chemical and physical characteristics of the water (temperature, pH, dissolved oxygen, conductivity, nitrates, phosphates, ammonia, depth, transparency), grain size of the substrate and level of anthropogenic disturbance were evaluated. The results showed that although L. hexapetala prefers shallow, warm, alkaline, moderately rich in ions and nutrients (especially phosphates) and oxygen-poor waters, it can grow in a wide range of environmental conditions. Moreover, as a typical invasive alien species, it spreads opportunistically in disturbed, unstable sites. Thus, L. hexapetala can invade freshwater habitats with different environmental conditions and subjected to anthropogenic disturbance. However, the results suggest that water depth may be a limiting factor in the early colonization stage of this species, which does not seem to be able to colonise waters deeper than 1 m in investigated sites, while it has been observed in significantly deeper waters in other European countries with a longer invasion history. Detecting the environmental parameters that most influence the growth of L. hexapetala becomes crucial both to identify the sites most at-risk of invasion in which to initiate timely monitoring actions for the species, and to be able to develop better management and control actions for this alien species in sites that have already been invaded.

Use of linear features by mammal predators and prey in managed boreal forests

In managed boreal forests, logging operations maintain high levels of anthropogenic disturbance in the ecosystem. The establishment of permanent anthropogenic linear features such as logging roads in the landscape may be a major factor in the predator-prey system. Logging roads may potentially improve the numerical and functional response of predators. Using camera traps, our objective was to explain according to local and landscape factors how the number of uses by wolves, black bears, lynx and moose, varies along different natural and anthropogenic linear features during the snow-free season. In western Quebec (Canada), the managed forest south of Val-d’Or encloses an isolated caribou population facing extinction that requires active restoration of their habitat. In this site, we used stratified random selection of gravel forest roads (n = 33), winter forest roads (n = 28) and riparian areas (n = 19) to compare their characteristics and number of uses by the four species. For wolves, black bears, and lynx, positive differences in lateral cover between the surroundings and the linear feature mainly explained their number of uses. Number of uses by wolves and lynx were positively related to use by their respective prey species (moose and snowshoe hare). Gray wolf use was also positively affected by distance to a higher forest road class and negatively affected by distance to the nearest urban area. Gravel forest roads had the highest number of uses by all species, as they showed greater positive differences in lateral cover as compared to the surroundings area due to their limited vegetation growth and by frequent maintenance activities. We recommend that restoration efforts aimed at forest road closures should target roads with a high value of difference in lateral cover, which is particularly the case in most gravel roads. Lower lateral cover on these linear feature as compared to their surroundings area favors the movement of predators and alternative prey. Our results thus suggest that investing in gravel roads restoration can benefit conservation efforts in caribou habitat.

Difference in acoustic responses to urbanisation in two African passerines

Modification of ecosystems as a consequence of urbanisation alters natural habitat structures and soundscapes, creating constraints for vocal communication in animals. Birds are able to adjust their vocalisation to the prevailing acoustic features of their habitat. As such, their sounds have been shown to reflect the level of anthropogenic disturbances across landscapes. While the effect of a single anthropogenic disturbance like ambient noise on birds’ vocal communication is widely investigated, the combined effects of various disturbances remain less explored. We tested single and combined effects of anthropogenic noise and urban physical structures on the vocalisations of two African passerines, the Common Bulbul Pycnonotus barbatus and Northern Grey-headed Sparrow Passer griseus. We predicted that (i) both species would increase the minimum frequency of their vocalisation to avoid masking by ambient noise, (ii) both species would decrease their maximum frequency to evade distortion by physical structures, (iii) the two urban components would have a significant combined effect on the vocalisations, and (iv) the change in minimum or maximum frequency will lead to a corresponding change in the vocalisation bandwidth. For the Common Bulbul, the minimum frequency increased significantly as the ambient noise level increased, but the maximum frequency did not change in response to urban physical structures. For the Northern Grey-headed Sparrow, the minimum frequency did not show a response to ambient noise, but the maximum frequency decreased significantly as physical structures and ambient noise increased. We did not find any evidence for a combined effect of urban physical structures and ambient noise on the vocal adjustment of either species. A change in either the minimum or maximum frequency resulted in a corresponding change in the vocalisation bandwidth of each species. Our findings highlight how the same vocalisation traits of different songbird species can be affected differently by novel selective pressures in acoustic communication that arise in urban environments.

Female chimpanzees avoid inbreeding even in the presence of substantial bisexual philopatry.

Inbreeding (reproduction between relatives) often decreases the fitness of offspring and is thus expected to lead to the evolution of inbreeding avoidance strategies. Chimpanzees (Pan troglodytes) are expected to avoid inbreeding as they are long-lived, invest heavily in offspring and may encounter adult, opposite sex kin frequently, especially in populations where both males and females commonly remain in the group in which they were born (bisexual philopatry). However, it is unclear whether substantial bisexual philopatry has been a feature of chimpanzees' evolutionary history or whether it is a result of recent anthropogenic interference, as the only groups for which it has been documented are significantly impacted by human encroachment and experience notable rates of potentially unsustainable inbreeding. Here we use 14 years of observational data and a large genomic dataset of 256 481 loci sequenced from 459 individuals to document dispersal and inbreeding dynamics in an eastern chimpanzee (P. t. schweinfurthii) community with low levels of anthropogenic disturbance. We document the first case of substantial bisexual philopatry in a relatively undisturbed chimpanzee community and show that, despite an increased inbreeding risk incurred by females who do not disperse before reaching reproductive age, natal females were still able to avoid producing inbred offspring.

Contrasting effects of beekeeping and land use on plant–pollinator networks and pathogen prevalence in Mediterranean semiarid ecosystems

Pollinators are fundamental for plant reproduction in natural and agricultural ecosystems. However, their populations are declining worldwide, threatening the functioning of the ecosystem service they provide. The factors driving this change are manifold, but land use changes and interspecific transmission of pathogens between managed and wild bees are prominent. In this context, most research efforts have focused on specific taxa and rarely at the community level, limiting our ability to fully understand the effects of global change on the functioning of plant–pollinator interactions in ecosystems.Here, we investigate the impact of human activities (beekeeping and land use intensity) on the spread of an emergent pathogen Vairimorpha ceranae in Mediterranean wild bee communities inhabiting landscapes with varying levels of anthropogenic disturbance. Plant–pollinator interactions were sampled in nine one‐hectare plots along a gradient of land use (urban structures, croplands and natural vegetation) and beekeeping intensity. We analysed the impact of human disturbances on pollination networks and pathogen prevalence, and applied a network approach to examine whether total effects of species in networks (i.e. direct plus indirect interactions) explain pathogen spread through bee communities.We found that V. ceranae prevalence in honey bees is not a good predictor of the pathogen spread through bee communities. There seems to be a temporal mismatch between pathogen dynamics in managed and wild bees. Networks with more diversity of interactions and more plants showed less pathogen prevalence, but total effect analyses (i.e. combining direct and indirect interactions) failed to explain pathogen transmission across pollination networks. Croplands increased wild bee density, and interactions and species diversity in networks, while shrublands had the opposite effect. Our results highlight the importance of studying pathogen dynamics at the community level and analysing species interaction patterns to improve our understanding of pathogen spread through communities.

Metagenomics-Based Microbial Ecological Community Threshold and Indicators of Anthropogenic Disturbances in Estuarine Sediments.

Assessing the impacts of cumulative anthropogenic disturbances on estuarine ecosystem health is challenging. Using spatially distributed sediments from the Pearl River Estuary (PRE) in southern China, which are significantly influenced by anthropogenic activities, we demonstrated that metagenomics-based surveillance of benthic microbial communities is a robust approach to assess anthropogenic impacts on estuarine benthic ecosystems. Correlational and threshold analyses between microbial compositions and environmental conditions indicated that anthropogenic disturbances in the PRE sediments drove the taxonomic and functional variations in the benthic microbial communities. An ecological community threshold of anthropogenic disturbances was identified, which delineated the PRE sediments into two groups (H and L) with distinct taxa and functional traits. Group H, located nearshore and subjected to a higher level of anthropogenic disturbances, was enriched with pollutant degraders, putative human pathogens, fecal pollution indicators, and functional traits related to stress tolerance. In contrast, Group L, located offshore and subjected to a lower level of anthropogenic disturbances, was enriched with halotolerant and oligotrophic taxa and functional traits related to growth and resource acquisition. The machine learning random forest model identified a number of taxonomic and functional indicators that could differentiate PRE sediments between Groups H and L. The identified ecological community threshold and microbial indicators highlight the utility of metagenomics-based microbial surveillance in assessing the adverse impacts of anthropogenic disturbances in estuarine sediments, which can assist environmental management to better protect ecosystem health.

Determinants of plant community along environmental gradients in Geramo forest, the western escarpment of the rift valley of Ethiopia.

Detailed information on plant community types, distribution, and their relationships with various environmental gradients is crucial for understanding forest dynamics and sustainable forest management because plant community types are influenced by various environmental factors. Thus, this study was conducted to investigate plant community types and species diversity in relation to various environmental gradients in Geramo Forest, which is a remnant forest in the western escarpment of the Rift Valley of Ethiopia. Vegetation data were collected in 96 nested plots (20 × 20 m2 and five 1 ×1 m2) laid systematically at a distance of 250 m along 16 line transects, which were laid 300 m apart. Environmental and disturbance variables were also collected from each main plot. Agglomerative hierarchical cluster analysis and Canonical correspondence analysis (CCA) with R software were used to identify plant community types and analyze the relationship between plant community types and environmental variables, respectively. The Shannon Wiener diversity index was used to compute species diversity among community types. Five significantly different (p ≤ 0.001) plant community types were identified. The CCA results showed that species diversity and community composition among different community types were significantly influenced by altitude, disturbance, soil organic carbon, slope, soil available phosphorus, and pH, which revealed the compounded effect of various environmental factors on species richness, diversity, and evenness among plant community types. The study also identified a significant level of anthropogenic disturbance and a strong reliance of the local community on the forest in the research area. Therefore, it is recommended that sustainable forest conservation interventions be implemented through awareness creation and the promotion of community-based approaches.

Multitemporal Analysis of Land Use/Cover Changes and Landscape Fragmentation in Murshidabad District of West Bengal, India

Rapid population growth, human migration, and commercial activities are changing land use and Land cover at a faster rate. The human being's need and greed to sustain themselves alter the earth's natural environment, and that change affected us. However, poor and unmanageable land conversion led to severe environmental effects. For planning and management purposes, precise information regarding land use and its characteristics is required to ensure the sustainability of the area. The current study uses multi-temporal satellite images to analyze the decadal change from 1991 to 2021. Supervised image classification is performed using the Maximum likelihood classifier. The main goal of this study is to compare post-classification results using change vector analysis and analyze human impact on the environment using FRAGSTAT. Fragstat is a widely used software program designed for analyzing spatial patterns in categorical maps. It is commonly employed in landscape ecology, conservation biology, and land management studies. The primary purpose of Fragstats is to quantify and assess the composition and configuration of patches or landscape elements within a given area. The built-up area increased from 2.57% to 8.41% over the past 30 years, while the agricultural land decreased from 83.51% to 70.05%. It was observed that the density of patches and percentage of landscape reduction over time, the rise in the number of patches for agricultural class from 3570 in 1991 to 10173 in 2021 indicates that spatial diversity is increasing in the class with higher levels of anthropogenic disturbances. Moreover, in landscape-level indices, the number of patch and landscape shape index increases, and a fall in the largest patch index indicate that the landscape is becoming more complicated and fragmented. To achieve the sustainable land-use planning and safeguard natural ecosystems and biodiversity from anthropogenic activities, land-use change maps are utilized as an early warning system.

Oil exploitation drives environmentally- and trait-mediated diversity of non-native plants in the Yungas forest in Argentina

Anthropogenic disturbances profoundly affect forest ecosystems worldwide. Oil exploitation is one of the major stressors driving the high co-occurrence of different non-native plant species in the Yungas forest of Calilegua National Park, Argentina. Using a dataset of records collected from 2010 to 2020, we evaluated environmental drivers and oil exploitation activity shaping the occurrence and diversity of non-native plant species in 18 study sites.To do so, we first compared species richness and diversity at different levels of anthropogenic disturbance. Then, we used regression models to investigate species-environment relationships. Lastly, a fourth corner analysis was applied to investigate how the interaction between explanatory variables and plant functional traits shapes the occurrence of the studied non-native plant species.We found that oil exploitation activities promoted the diversity of non-native plants in the protected area. Presence of the three most widespread non-native plant species was influenced by the topographic slope and organic matter content. The fourth corner analysis further showed that the positive interaction between plant N-fixation capacity with either close proximity to oil boreholes, a low organic matter content or a high coverage of herbs positively affected the presence of non-native plant species.To our knowledge, this is the first time that trait-environment relationships under a gradient of anthropogenic disturbance were investigated to explain the occurrence and diversity of non-native plant species. Given that abundant non-native plant species have partially overlapping niches in the Yungas transition forests, it is advisable that future restoration actions focus on groups of non-native plants rather than single species. Additionally, non-native plant species of concern, which are able to successfully establish in both disturbed and undisturbed areas require adapted eradication measures.

Characteristics of the Stone Crayfish Population along a Disturbance Gradient—A Case Study of the Kustošak Stream, Croatia

The stone crayfish, Austropotamobius torrentium, is a native European freshwater species sensitive to habitat alterations such as stream channelization and urban development, putting its populations at risk. This study aims to assess how habitat alteration and subsequent water quality changes affect the stone crayfish population in the Kustošak Stream (Croatia) through three selected sites under different levels of anthropogenic disturbance: (1) undisturbed; (2) recently modified, and (3) long-time modified sites. At each site, crayfish were captured, measured, and marked to estimate population size, structure, and crayfish condition. Additionally, we examined whether water quality (18 measured physicochemical parameters) affects relative crayfish abundance. We also used mitochondrial sequencing and microsatellite genotyping to assess species genetic diversity and population connectivity and to compare results among the sites. The results showed that habitat alteration caused an overall reduction in population abundance and changes in size structure; however, it had not yet resulted in detectable genetic differences. Partial least squares regression showed that crayfish abundance was affected by the physicochemical parameters of water, including, among others, oxygen, calcium ions, nitrates, pH, and water temperature. We discuss our findings in the context of the effects of anthropogenic disturbance on the viability and persistence of this EU priority species.

Effects of human disturbance on risk‐taking behavior in painted turtles

AbstractAnimals are exposed to high levels of anthropogenic disturbance, which has profound consequences for population persistence. Individuals can adjust their behavior plastically when faced with perturbations in their environment and may show consistent differences in the way they perceive and respond to risky situations. Over time, this variability among individuals in response to risk can affect the dynamics of populations exposed to human disturbance. Thus, understanding how animals cope behaviorally with human disturbance is important, especially for species vulnerable to human perturbations, such as turtles. In this context, we evaluated whether risk‐taking behaviors are consistent within individual painted turtles (Chrysemys picta) and assessed how these behaviors are related to the extent of human disturbance along the Rideau Canal, Ontario, Canada. Specifically, we conducted repeated measurements of the number of active defensive behaviors used during handling and the time taken to escape a floating platform for 730 painted turtles (1117 observations) from 22 sites varying in human disturbance along the canal. We also quantified the emergence of the turtles from the water after escaping the platform. First, individual painted turtles showed consistent differences in all risk‐taking behaviors. Second, painted turtles in areas with high boat activity displayed more active defensive behaviors, while turtles from sites in proximity to more houses with access to the canal used fewer. Our study highlights the importance of studying animal behavior to better understand the impact of human activities on animal populations.

Determination of optimal tree height models and calibration designs for Araucaria araucana and Nothofagus pumilio in mixed stands affected to different levels by anthropogenic disturbance in South-Central Chile

Key messageHere, we present a workflow for determining the optimal tree height model and calibration design for forests affected to varying degrees by anthropogenic disturbance. For mixed Araucaria-Nothofagus forests, tree height predictions in newly surveyed stands are most accurate and effective when the height of up to five random trees is measured to recalibrate predefined nonlinear mixed-effects models.ContextAraucaria-Nothofagus forests in Chile are affected by anthropogenic disturbances such as intentional forest fires, grazing, and seed harvesting, causing forest structure to become more heterogeneous. This also challenges tree height predictions, which are required for yield estimations, carbon accounting, and forest management, since height measurements of standing trees are often considered too costly, difficult, and imprecise.AimsHow does the structure of these forests vary by different levels of anthropogenic disturbance? Which models for estimating tree height of Araucaria araucana and Nothofagus pumilio are most reliable and generally usable? And considering their application in stands they have not been fitted to, which calibration design is optimal for these models?MethodsTwelve stands were surveyed and classified into four different intensities of anthropogenic disturbance. In 25 to 36 plots per stand, horizontal point sampling measurements of stem diameter as well as of height of selected trees were carried out. Different quantitative stand-level properties were calculated to determine forest structure, which was compared among stands by cluster analysis. To identify the optimal height-diameter (H–D) model, simple models including diameter only as well as generalized models including stand variables were tested, each additionally extended by a nonlinear mixed-effects (NLME) modeling framework accounting for nested and random effects. To further determine tree height in new stands, the optimal model calibration design was identified involving the empirical best unbiased predictor technique.ResultsForest structure greatly varied among stands affected by different levels of anthropogenic disturbance, which challenged the development of tree height prediction models. Of all the simple H–D models considered, the Gompertz model was the best for A. araucana and the Näslund model for N. pumilio. The models progressively improved by adding stand variables and using NLME techniques. However, our final model comparisons indicate that a calibrated simple NLME model without stand variables should be preferred. It was further found that the optimal calibration design is to use five randomly selected trees.ConclusionAlthough anthropogenic disturbances can have a complex effect on height-diameter relationships, the same H–D model can be used for stands representing different anthropogenic disturbance levels and recalibrated by cost-effective measurements.

Assessing benthic reef assemblages: A comparison between no-take artificial reefs and partially protected natural reefs

The marine protected area (MPA) of the Espiritu Santo Archipelago (ESA; Gulf of California), is exposed to a high level of anthropogenic disturbances, consequently, the local authorities have deployed artificial reefs (shipwrecks) in the ESA area to increase fishing refuges, breeding sites, and tourist attractions. To explore the potential contribution of these artificial reefs as a conservation tool, we compared their benthic community structures (i.e. diversity and live cover categories) to those of the natural reefs. Our results indicate a higher abundance of mollusks on the artificial reefs compared to the natural reefs; a higher echinoderm abundance on the natural reefs; and a very similar species richness of hexacorals between the natural and artificial reefs, with 10 and 9 species recorded respectively. The natural reefs hosted a four-fold higher live cover of hexacorals than the artificial reefs, while the artificial reefs had a higher number of octocoral species, 8 versus 5 on the natural reefs. In addition, the artificial reefs had a 4.6 fold higher octocoral cover than the natural reefs. Overall findings indicate that the benthic community assemblages significantly differ between the natural and artificial reefs, which may be related to their location, structural composition, material, and morphology. These results suggest that shipwrecks have the potential to enhance local reef diversity by increasing the cover and abundance of certain benthic-associated species. Although the shipwrecks do not function as surrogate habitats for the adjacent natural rocky reefs, as no-take areas they provide suitable refuges for several target species (e.g. black coral and mollusks).

Oxidative status of Ctenomys flamarioni (Rodentia: Ctenomyidae) in natural areas with different levels of anthropic activity in southern Brazil

Rampant urbanization in coastal environments turns areas close to the seafront into a highly impacted ecosystem, possibly affecting the health and well-being of resident animal species. The tuco-tuco Ctenomys flamarioni is an endemic and endangered subterranean mammal from southern Brazil, and the anthropic influence was considered one of the main threats to the species. In this context, the present study aimed to investigate the patterns of oxidative status of the species in natural areas with different levels of anthropogenic disturbance. We evaluated two populations of C. flamarioni, one located in an area with intense anthropogenic impact due to urbanization and tourist activity, and the other in a non-impacted area. Oxidative injury parameters (lipid peroxidation and carbonylated protein levels), and the activities of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glucose 6-phosphate dehydrogenase, glutathione S-transferase and carboxylesterase were measured. Individuals inhabiting the impacted area had lower G6PDH activity and higher levels of carbonylated proteins. This combination of higher level of oxidative damage and lower antioxidant activity is an indication that the oxidative status of animals in the impacted population is possibly being affected as a consequence of anthropogenic activities in this environment. The values of the parameters obtained in the current study can be used as a reference of the oxidative state of C. flamarioni in future studies with tuco-tucos.

Factors affecting the transferability of bioindicators based on stream fish assemblages

The development of multimetric indices (MMIs) to measure the biotic condition of aquatic habitats is based on metrics derived from biological assemblages. Considering fish assemblages, the inconsistencies in metrics responses outside of the places where they were developed limit MMI transferability and applicability to other locations, requiring local calibration. The factors behind the low transferability of these MMIs are still poorly understood. We investigated how environmental dissimilarity and spatial distance influence the transferability of metrics generated from local stream fish assemblages to other regions. We also tested whether functional and taxonomic metrics respond differently to the spatial distance. We used data from 239 fish assemblages from streams distributed across a Brazilian, the upper Parana basin and characterized each site according to the level of anthropogenic disturbance at the landscape scale using an Anthropogenic Pressure Index (API). We divided the upper Parana basin into sub-basins and used two of them to create template response models of the metrics in relation to the API. We used these response models to predict the responses outside the template sub-basins. Our response variable representing a metric of transferability was the absolute difference between metric's predicted and observed value for each site (prediction error). We thus modeled the prediction error in relation to the predictor variables that were i) the environmental dissimilarity between each site with the average of the sites from template sub-basins (climatic, topographic and soil type variables) and ii) the spatial distance (overland and watercourse distance) between each site and the center of the template sub-basin. We found that errors in metric predictions were associated with both environmental dissimilarity and spatial distance. Furthermore, functional and taxonomic metrics responded equally to spatial distance. These results indicate the need for local calibration of metrics when developing MMIs, especially if the protocols already available come from distant and environmentally dissimilar places.

Fluctuating asymmetry and environmental stress in a reptile under different levels of anthropogenic disturbance

In the Monte region of Argentina, the local population is causing severe habitat degradation by extracting native vegetation and domestic animal grazing. To assess whether disturbed environments have higher levels of asymmetry than control environments, we examined morphological variation and fluctuating asymmetry in the cephalic region of the longtail whiptail lizard Aurivela longicauda (Teiidae) using a Procrustes analysis with geometric morphometry. This is the first study of asymmetry using geometric morphometry in a lizard from Argentina. While there was no difference in the size of the cephalic region between the two environments, there were differences in shape between the right and left side of the lizard's head (object symmetry), the differences being greater at disturbed sites (fluctuating asymmetry), suggesting that anthropogenic activities may act as stressors driving alterations in the fitness (reproduction) of reptile populations. Fluctuating asymmetry analysis is an excellent conservation biology and environmental monitoring tool for measuring stress in different organisms.

Butterfly Diversity in Relation to Human-Impact Gradient in Outskirts of Kolkata, West Bengal, India

Anthropogenic activities may affect species diversity and community structure. Butterfly species diversity in relation to human-impact gradient was evaluated in the Baruipur subdivision, outskirts of Kolkata metropolis, West Bengal, India as a model geographic area. Four study sites situated in bird sanctuaries, rural, suburban and urban areas with different levels of anthropogenic disturbances were selected to assess the human impact on butterfly diversity. A total of 80 butterfly species were recorded during the entire study period with the sanctuary (with minimal anthropogenic disturbance) showing the highest species richness (73) followed by rural (62), suburban (54) and urban (36) study sites indicating a strong negative impact of anthropogenic disturbance on butterfly species diversity. Butterfly species diversity varied significantly among different habitats (p ˂ 0.001). The relative abundance of butterflies also varied seasonally. It is apparent that the area under the present study is able to sustain diverse butterfly species provided natural habitats are protected from anthropogenic disturbances and steps are taken to increase urban greenery to support butterfly diversity and consequent ecosystem services.

Urban forest soils harbour distinct and more diverse communities of bacteria and fungi compared to less disturbed forest soils.

Anthropogenic changes to land use drive concomitant changes in biodiversity, including that of the soil microbiota. However, it is not clear how increasing intensity of human disturbance is reflected in the soil microbial communities. To address this issue, we used amplicon sequencing to quantify the microbiota (bacteria and fungi) in the soil of forests (n=312) experiencing four different land uses, national parks (set aside for nature conservation), managed (for forestry purposes), suburban (on the border of an urban area) and urban (fully within a town or city), which broadly represent a gradient of anthropogenic disturbance. Alpha diversity of bacteria and fungi increased with increasing levels of anthropogenic disturbance, and was thus highest in urban forest soils and lowest in the national parks. The forest soil microbial communities were structured according to the level of anthropogenic disturbance, with a clear urban signature evident in both bacteria and fungi. Despite notable differences in community composition, there was little change in the predicted functional traits of urban bacteria. By contrast, urban soils exhibited a marked loss of ectomycorrhizal fungi. Soil pH was positively correlated with the level of disturbance, and thus was the strongest predictor of variation in alpha and beta diversity of forest soil communities, indicating a role of soil alkalinity in structuring urban soil microbial communities. Hence, our study shows how the properties of urban forest soils promote an increase in microbial diversity and a change in forest soil microbiota composition.

Anthropogenic influences on the distribution of a threatened apex-predator around sustainable-use reserves following hydropower dam installation.

Although previous studies demonstrate declines in many large bodied species following hydropower dam installation, others suggest that some species, including the giant otter (Pteronura brasiliensis) may return to newly created reservoir habitats. Yet, there is a lack of evidence to support such theories. Here, we analyzed the effects of a hydropower dam on giant otters using a before-after control-impact study design in the eastern Brazilian Amazon. We collected data 3 years before (2011–2012 and 2015) and after (2017–2019) dam construction, totaling 6,459 km of surveys along rivers with 43 direct sightings of giant otters. Contrary to expectations, our results revealed that giant otters did not remain nor did they return to the dam reservoir. Beyond the zone directly impacted by the dam giant otter occurrence and relative abundance declined next to sustainable-use reserves where the river was more intensely used by people. Our study showed that in the absence of active management sustainable-use reserves and low human density were not sufficient to maintain this apex-predator. Our findings suggest a need to proactively create and maintain areas with low levels of anthropogenic disturbance to enable sustainable coexistence between energy demands and biodiversity across Amazonia.