Extent Of Habitat Research Articles

Marine habitat mapping to support the use of conservation and anti-trawl structures in Kep Province, Cambodia

Abstract The marine habitats within the Kep Archipelago, Cambodia, support species of conservation importance and commercial value. Despite the area being designated a Marine Fisheries Management Area (equivalent to a Marine Protected Area locally), illegal trawling has continued to damage vulnerable habitats within the region. To augment the protection of the designated area, Conservation and Anti Trawl Structures (CATS) have been deployed locally. These structures can snare the nets of illegal trawlers and provide a hard substratum for coral colonization. A sidescan sonar survey and ground truthing campaign was used to precisely locate the 40 CATS deployed and produce maps of the important benthic habitats in the area. Due to the challenging coastal environment and minimal available infrastructure, this study used small, rechargeable or low-power (12 V), and low-cost habitat mapping equipment to map the approximate extent of several benthic habitats of conservation interest. The area and type of habitat protected by CATS has been estimated by combining the marine habitat map with the precise locations of the deployed CATS. It is hoped that this information will help inform local management decisions, such as optimizing the placement of future CATS.

Predicting the optimal amount of time to spend learning before designating protected habitat for threatened species

Abstract Deciding when to protect threatened species habitat when complete knowledge about the habitat extent is uncertain is a common problem in conservation. More accurate habitat mapping improves conservation outcomes once that habitat is protected. However, delaying protection to improve accuracy can lead to species decline or, at worst, local extinction when threats to that habitat continue unabated before protection is implemented. Hence, there is a trade‐off between gaining knowledge and taking conservation action. We quantified this trade‐off and determined the optimal time to spend learning about a species' habitat before protecting that habitat. We used a range of hypothetical learning curves to model improvements in the accuracy of predicted habitat over time, and receiver operating characteristic (ROC) curves to model the corresponding increase in the proportion of habitat protected. We used rates of habitat loss to model the impact of delaying habitat protection and derived analytical solutions to the problem for different types of learning curves. We illustrate our approach using two threatened species, the koala Phascolarctos cinereus in Australia and northern abalone Haliotis kamtschatkana in Canada. Our approach confirms that when impacts of threatening processes are incurred rapidly, the need for timely protection is high, and the optimal time to spend learning is short for all learning curves. When the rate of habitat loss is low, we benefit from better habitat identification, and the optimal time to protect is sensitive to assumptions about how we learn and the proportion of non‐habitat we are willing to protect unnecessarily. Navigating the trade‐off between information gain and timely action is a common problem in conservation. By optimizing the trade‐off between the benefits of improving mapping accuracy and the costs of delaying protection, we provide guidelines on the effective allocation of resources between habitat identification and habitat protection. Importantly, by explicitly modelling this trade‐off with a range of learning curves and estimates of the rates of habitat loss or other threatening processes, we can predict the optimal time to spend learning even when relatively little is known about a species and its habitat.

Modeling the Climate Suitability of Northernmost Mangroves in China under Climate Change Scenarios

Mangroves are important wetland ecosystems on tropical and subtropical coasts. There is an urgent need to better understand how the spatial distribution of mangroves varies with climate change factors. Species distribution models can be used to reveal the spatial change of mangroves; however, global models typically have a horizontal resolution of hundreds of kilometers and more than 1 km, even after downscaling. In the present study, a maximum entropy model was used to predict suitable areas for the northernmost mangroves in China in the 2050s. An approach was proposed to improve the resolution and credibility of suitability predictions by incorporating land-use potential. Predictions were made based on two CMIP6 scenarios (i.e., SSP1-2.6 and SSP5-8.5). The results show that the northern edge of the natural mangrove distribution in China would migrate from 27.20° N to 27.39° N–28.15° N, and the total extent of suitable mangrove habitats would expand. By integrating 30 m resolution land-use data to refine the model’s predictions, under the SSP1-2.6 scenario, the suitable habitats of mangroves are predicted to be 13,435 ha, which would increase by 33.9% compared with the current scenario. Under the SSP5-8.5 scenario, the suitable area would be 23,120 ha, with an increased rate of 96.5%. Approximately 40–44% of the simulated mangrove patches would be adjacent to aquacultural ponds, cultivated, and artificial land, which may restrict mangrove expansion. Collectively, our results showed how climate change and land use could influence mangrove distributions, providing a scientific basis for adaptive mangrove habitat management despite climate change.

Projecting the remaining habitat for the western spadefoot (Spea hammondii) in heavily urbanized southern California

Extensive urbanization in coastal southern California has reduced natural habitat in this biodiversity hotspot. To better conserve ecological communities, state and federal agencies, along with local jurisdictions and private stakeholders, developed regional conservation plans for southern California. Although many protected areas exist within this region, the patchwork nature of these protected areas might not provide good coverage for species that require multiple habitat components, such as amphibians with complex life histories. Because of declines in the past century, the status of the western spadefoot ( Spea hammondii ) in southern California is of concern to state and federal wildlife agencies. Species distribution models (SDMs) can aid in determining the conservation status of imperiled species by projecting where suitable habitat remains and how much is protected from further development. We built SDMs that integrated site-occupancy data from systematic pitfall trapping surveys and presence-only data from biodiversity databases and citizen science platforms to project the current distribution of western spadefoots in southern California. Western spadefoot occurrence was positively related to the cover of grassland or shrub/scrub and the % sand in the soil within a 1000 m buffer, and was negatively related to slope, elevation, and distance to ephemeral streams or vernal pools. Most of the remaining unprotected habitat for western spadefoots is in the southern half of its historical range in western San Diego and Riverside counties. A few large tracts of spadefoot habitat exist on U.S. Department of Defense lands and smaller tracts remain on ecological reserves owned by state and local government agencies. Only small patches of habitat remain in the northern half of this clade’s historical range in Ventura, Orange, Los Angeles, and San Bernardino counties. Existing regional conservation plans provide ostensible spatial coverage of the majority of extant habitat for western spadefoots in southern California, but most of the habitat within the jurisdiction of these plans lacks formal protection, exposing this species to further declines as urbanization continues in the 21st century.

Impacts of climate change on the geographic distribution of African oak tree (Afzelia africana Sm.) in Burkina Faso, West Africa

Afzelia africana Sm – a multipurpose leguminous tree species – is threatened in West Africa – a climate change hotspot region. Yet, although the impacts of land use on this species dynamics have been widely reported, there is a little literature on the impacts of climate change on its spatial distribution. This study aimed to predict the impacts of climate change on the geographic distribution of A. africana in Burkina Faso. A total of 4,066 records of A. africana was compiled from personal fieldwork and vegetation database. Current and future bioclimatic variables were obtained from WorldClim website. For future climatic projections, six global climate models (GCMs) were selected under two emission scenarios (RCP 4.5 & RCP 8.5) and two horizons (2050 & 2070). Presence data and bioclimatic variables were processed in ArcGIS software and used in the algorithm MaxEnt (maximum of entropy) to predict the species distribution. Findings showed that maximum temperature of warmest month and mean temperature of coldest quarter mostly affect the habitat suitability of A. africana. About 25.54% of Burkina Faso land surface was currently suitable for A. africana conservation. Under future climatic projections, all the climate models predict climate-driven habitat loss of the species with a southward range shift. Across the two emission scenarios, the spatial extent of suitable habitats was predicted to decline from 9.43 to 23.99% and from 12.29 to 25% by the horizons 2050 and 2070, respectively. Habitat loss and range shifts predicted in this study underline the high vulnerability of A. africana to future climate change. Reforestation actions and the protection of predicted suitable habitats are recommended to sustain the species conservation.

EUPHORIA DAVIDII SUBILS (EUPHORBIACEAE) IN FLORA OF RAILWAY TRACKS OF DNIESTER BAY BAR

Aim. Anthropogenically transformed ecotopes act as a centre for existance of many adventive species. The distribution of North-American species Euphorbia davidii subsp. Poinsettia across various continents is often attributed to the export of grain. For some time scientists have been bringing up the issue about identification of plants E. davidii in new territories, because the species is morphologically similar to E. dentata agg.
 The species E. davidii is characterised by a high invasive potential, it is a neophyte. In Ukraine the species is represented by separate localities almost throughout the country. It is related to sectors of ports, railway tracks, and abandoned lands.
 Methods. In the year 2021, by means of route method, in sectors of railway tracks of the Dniester bay bar, between the railway stops Karolina-Buhas and Soniachna (total length is up to eight kilometers) seven localities of E. davidii were distinguished; the coordinates of the locations are listed in the publication. The examined ecotopes are characterised by a crushed stone substratum, with higher temperatures, and also by specific vibrational, insolational and hydrological modes.
 Results. Both inconsiderable in number of plants localities (32 exemplars) and zones, where the number of plants reaches over 2000 are represented. The extent of habitats ranges from 2 to 20 meters. The height of particular, the most developed individuals constituted 20 cm. As a rule, in the inter-rail space there is a considerably smaller number of plants, however, they are better developed, well-branched and have more inflorescences with fruits.
 Conclusions. A number of plants from the southern slopes of the railways is typically bigger, however, the plants on the southern slopes (in comparison with the northern ones) are worse developed, branch out less and, at the time of conducting the research were represented by a smaller number of generative individuals. In sandy sectors of the bay bar adjoining the railway tracks the plants E. davidii were almost not noticed. The individuals found in the above-mentioned sectors are characterised by stunted growth, a single stem, almost did not bloom, and did not produce seeds.

Coarazuphium auleri sp. n. (Carabidae: Zuphiini), a new troglobitic ground-beetle in Central-Western Brazil

ABSTRACT In this paper, we describe Coarazuphium auleri sp. n. Until now, the species occurred in a single limestone cave, located at Nobres municipality (state of Mato Grosso – Central-Western Brazil). The new species comprises an apterous species from the genus Coarazuphium with the complete absence of hindwings, eyes are composed of very reduced eyes-scars, depigmentation and ommatidia are not evident. We also provide an updated key for species identification of Coarazuphium from the most recently published one. We followed the criteria of IUCN and classified the species as Critically Endangered – CR, IUCN criteria B1ab(iii)+2ab(iii), since the species has a restricted geographical distribution; estimated occurrence length <100 km2; population in few locations and with a continued decline in area, extent, and quality of habitat. According to Brazilian law, the existence of a critically endangered species places the Lagoa Azul cave as one of maximum relevance. http://www.zoobank.org/urn:lsid:zoobank.org:pub:E33469CE-4638-4153-BD31-291F751AC3A1

A null model for quantifying the geometric effect of habitat subdivision on species diversity

AbstractAimTo derive null models for the expected number of species shared among multiple samples or habitat patches, allowing exploration of the geometric effects of subdivision on species diversity.LocationGlobal.Major taxa studiedPredominantly sessile organisms.MethodsThe occurrence probability of a species in a subdivided area depends on its abundance and spatial pattern over a known habitat extent. The joint probability that two subareas share a species is the product of the probability of species occurrence in each subarea provided that the latter probability is independent. The sum of this probability over all species is the number of species the two subareas share, or zeta diversity of order 2. Generalizing from 2 tomsubareas yields a null model for zeta diversity of orderm. From zeta diversity, many metrics (e.g., beta and gamma diversity) for themhabitat patches can be calculated, revealing the effects of increasing habitat fragmentation.ResultsThe null models show the geometric effects of subdivision depend on patterns of spatial distribution of species within a landscape and evenness of species abundance distribution. For aggregated assemblages, increasing subdivision decreases shared species, increases beta diversity and results in higher total species richness in subdivided habitat than an equal contiguous area.Main conclusionsTo correctly interpret diversity patterns in fragmented habitat the geometric effects of subdivision must be considered. Our models explain why fragmented habitat could have higher diversity than continuous habitat of equal area but predict a threshold patch‐size above which this will not occur (herec. 100 ha). Apparently positive diversity effects of subdivision, including more species in groups of small patches, are probable outcomes of spatial aggregation of assemblages. The shared species null models offer an analytical tool for exploring the geometric effects of subdivision on diversity while controlling for total habitat area.

The Endangered giant nuthatch Sitta magna: population size, habitat availability and the implications for its conservation in Thailand

AbstractAvailable habitat and hence the global population of the Endangered giant nuthatch Sitta magna, restricted to lower montane habitats of south-western China, eastern Myanmar and northern Thailand, remains poorly quantified. Thailand is the only portion of the species’ range for which there is a population estimate. To obtain a more precise estimate of the Thai population and clarify the extent and characteristics of suitable habitat remaining, we conducted 335 point-count surveys at 67 points across eight localities during November 2019–February 2020. We estimated abundance and identified preferred habitat characteristics using N-mixture models, and created suitable habitat maps based on data from surveys and remote sensing. Our estimate for Thailand was 578 (95% CI 391–854) individuals based on a density of 3.7 (95% CI 2.5–5.5) individuals/km2 in 156 km2 of suitable habitat. The giant nuthatch prefers dry forest with a large amount of mature native or planted pine Pinus kesiya and with a large tree basal area and an open canopy. Our estimate of suitable habitat remaining was less than previously reported and thus the population has probably decreased, although most of this habitat is within protected areas. Habitats for the species in Thailand have a stronger level of protection than in Myanmar and China, although habitat in China remains unquantified. We recommend further research in Myanmar and China, which may hold the majority of available habitat for the giant nuthatch. For long-term management, detailed study of the association of the giant nuthatch with pine plantations is required.

Distribution and density of the Critically Endangered estuarine pipefish across its range – implications for conservation

Abstract The identification and development of locally significant conservation actions require comprehensive and current ecological species information. Logistically this can be difficult, especially when studying rare and cryptic species which are at greater risk of becoming extinct. This study investigated the current distribution and density of the estuarine pipefish Syngnathus watermeyeri, the only Critically Endangered pipefish in the world, and the commonly found longsnout pipefish Syngnathus temminckii. Pipefish were surveyed using a seine net in the Kariega, Bushmans, Kasouga and Kleinemonde East and West estuaries, located on the south coast of South Africa, in October 2019, March 2020 and July 2020. The habitat and physico‐chemical characteristics of each site were measured to determine whether these factors had an effect on the presence of S. watermeyeri. In addition, available habitat extent within the Bushmans and Kariega estuaries was mapped. Pipefish were only detected in two of the five estuaries within the historical range of S. watermeyeri and a total of 59 S. watermeyeri and 45 S. temminckii were found across all three surveys. Zostera capensis and Codium sp. were the dominant submerged vegetation within the Bushmans and Kariega estuaries and the presence of pipefish was positively associated with the availability of vegetation, especially Codium sp. This is the most extensive targeted survey for S. watermeyeri to date, both temporally and spatially, and provides important insights into what threatens this species. This information should be used to inform future IUCN Red List assessments and the development of locally significant conservation actions.

Quantifying the Response of an Estuarine Nekton Community to Coastal Wetland Habitat Restoration

Globally coastal habitats are experiencing degradation and threatening the production of critical ecosystem services such as shoreline stabilization, water filtration, and nursery grounds for marine fauna. To combat the loss of these ecosystem services, resource managers are actively restoring coastal habitats. This study compares samples collected from non-restored sites, sites restored in 2011, and sites that underwent restoration in 2019. Restoration sites are impacted wetlands with high elevation mounds that were leveled to increase the areal extent of intertidal habitats, enabling the recruitment of intertidal flora and fauna. Fyke nets were used to sample nekton within the upper intertidal zone. To quantify restoration success, nekton abundance, biomass, diversity, and indicator species were quantified. Sites restored in 2011 had a greater abundance compared to non-restored sites. Common snook, clown gobies, silversides, juvenile mullet, and Gulf killifishes were indicator species at successfully restored sites, while salinity, site type, and Secchi depth played important roles in predicting abundance and diversity. These findings are consistent with recent studies suggesting it can take years to see quantifiable differences in nekton communities following habitat restoration. Additionally, this work provides new insight regarding the benefits of restoring coastal wetland elevation to maximize intertidal habitat, thereby positively impacting nekton communities.

Identification, surveillance and management of Aedes vexans in a flooded river valley in Nottinghamshire, United Kingdom

Aedes vexans is known to occur in large populations in riverine floodplains in much of Europe, where it can cause a significant biting nuisance and is often subject to large scale control strategies. Until recently it had only been reported in very small numbers in the United Kingdom. After receiving reports of nuisance biting near the river Idle, Nottinghamshire (East Midlands, England), mosquito surveillance was conducted over three years (2018-2020) using Mosquito Magnet adult traps. Ae. vexans was found in all years, in very high numbers, particularly in 2020, reaching a peak of almost 5,000 female mosquitoes per trap night, the highest reported density of trapped adult mosquitoes in the UK. Larval control was conducted in all years, and adult control in one year, however local peculiarities of flood and water management presents challenges and necessitates a multi-faceted approach. Strategies for further expansion of the control operation by developing strategies for water management, coupled with larval surveys to define the extent and seasonality of larval habitats, and application methods of Bacillus thuringiensis israelensis products are discussed.

Three new tiny species of the microhylid frog genus Cophixalus Boettger, 1892 from central Papua New Guinea

We describe three new species of frogs in the asterophryine microhylid genus Cophixalus from New Guinea's central cordillera. All three are characterized by their very small size (adult body length < 18 mm), reduced first fingers, narrow ridges on the dorsum, and having terminal discs on the fingers smaller than or the same size as those on the toes. They were found on the forest floor or on low vegetation in montane rainforest, where males called at night during or after heavy rain. Each of the new species is known only from one or two locations within a small area of central Papua New Guinea, although the extent of suitable habitat in the region suggests that their distributions may be broader. This study brings to 51 the number of described Cophixalus species known from the New Guinea region, but numerous additional undescribed forms reside in museum collections awaiting formal description, and others undoubtedly await discovery in their natural habitats.

Incorporating phylogeographic information in alien bird distribution models increases geographic extent but not accuracy of predictions

Species distribution models (SDM) have been proposed as valuable first screening tools for predicting species responses to new environmental conditions. SDMs are usually conducted at the species level, assuming that species-environment relationships are a species-specific feature that do not evolve and show no variability across a species’ range. However, broad environmental tolerances at the species level can encompass narrower and different environmental tolerances for specific lineages or populations. In this study, we evaluate whether SDMs that account for within-taxon niche variation in climate and human-habitat associations provide better fits between projected distributions and real occurrence data for alien bird species than species-level SDMs. Our study focuses on eight alien bird species with established alien populations for which detailed phylogeographic information was available. Similarity in climates and human disturbance conditions occupied by different phylogenetic groups within species was low and not greater than random expectations. Accounting for intraspecific niche variation in SDMs modified the distribution and extent of suitable habitat predicted as susceptible to invasion, but did not result in more accurate model predictions in alien ranges. Until more accurate information on intraspecific variability is available, species-level models can be reasonable candidates. When phylogeographic information is available, the use of the most conservative criterion (i.e. to model both species and lineages on the basis of the actual range) is recommended.

Assessing Suitable Habitats for Treefrog Species after Previous Declines in Costa Rica

Treefrogs represent 22% of amphibian species in Costa Rica, but gaps in the knowledge about this group of amphibians can impede conservation efforts. In this study, we first updated the status of Costa Rican treefrogs and found that a total of 38% of treefrog species are threatened according to the most recent IUCN assessment in 2019. Additionally, 21% of Costa Rican treefrog species have a high vulnerability to extinction according to environmental vulnerability scores. Then, we predicted the historical climatic suitability of eight target species that we expected to have exhibited changes in their ranges in the last 20 years. We assessed the location of new occurrence records since 2000 to identify recovery, range expansion, or previously underestimated ranges due to methodological limitations. We also estimated the area of each species’ suitable habitat with two metrics: extent of suitable habitat (ESH) and area of minimum convex polygon (AMCP). Six declined species exhibited recovery (i.e., new occurrences across historical range after 2000), with the widest recovery found in Agalychnis annae. We also found that Isthmohyla pseudopuma appears to have spread after the decline of sympatric species and that the range of I. sukia was originally underestimated due to inadequate detection. We found that the ESH was 32–49% smaller than the AMCP for species that are slowly recovering; however, the ESH is similar or greater than the AMCP for species that are recovering in most of their ranges, as well as rare species with widespread ranges. Results of this work can be used to evaluate the risk of environmental threats and prioritize regions for conservation purposes.

How Much Shallow Coral Habitat Is There on the Great Barrier Reef?

Australia’s Great Barrier Reef (GBR) is a globally unique and precious national resource; however, the geomorphic and benthic composition and the extent of coral habitat per reef are greatly understudied. However, this is critical to understand the spatial extent of disturbance impacts and recovery potential. This study characterizes and quantifies coral habitat based on depth, geomorphic and benthic composition maps of more than 2164 shallow offshore GBR reefs. The mapping approach combined a Sentinel-2 satellite surface reflectance image mosaic and derived depth, wave climate, reef slope and field data in a random-forest machine learning and object-based protocol. Area calculations, for the first time, incorporated the 3D characteristic of the reef surface above 20 m. Geomorphic zonation maps (0–20 m) provided a reef extent estimate of 28,261 km2 (a 31% increase to current estimates), while benthic composition maps (0–10 m) estimated that ~10,600 km2 of reef area (~57% of shallow offshore reef area) was covered by hard substrate suitable for coral growth, the first estimate of potential coral habitat based on substrate availability. Our high-resolution maps provide valuable information for future monitoring and ecological modeling studies and constitute key tools for supporting the management, conservation and restoration efforts of the GBR.

The impact of water supplement on habitat suitability for breeding red-crowned cranes

With the increasing influence of climate change and human activities, water shortage in wetlands is becoming an urgent problem. In order to maintain waterfowl habitat and prevent wetland degradation, water management strategies have been implemented for many wetland reserves. However, there is often uncertainty concerning optimal water supply amount, especially during the breeding periods of endangered waterfowls. In this study, the MIKE 21 hydrodynamic model was used to simulate the impact of different water supply amounts on water depths in the Zhalong wetlands, China. The simulated water depths were utilized to evaluate the area of suitable habitat for breeding red-crowned cranes (Grus japonensis) based on the Maximum Entropy (MaxEnt) niche model. The optimal water supply amount was determined by maximizing the extent of suitable breeding red-crowned cranes habitat. Results suggest that for the Zhalong wetlands, water depth is the key habitat feature which determines the variability of suitable habitat extent. The optimal water supply amount for the Zhalong wetlands in 2014 was 1.13 × 108 m3, producing a suitable breeding habitat area of 237.25 km2 at the end of the water supply period, 50% greater than the suitable habitat extent with the existing water supplement scenario. The proposed method, combining a hydrodynamic model with the MaxEnt niche model, has the potential to determine optimal water supply amount to any semi-closed floodplain. The results of the current study can not only provide an evidence base for wetland water management, but also provide a scientific basis for the study of wetland eco-hydrological processes and their impact on wetland biological diversity conservation.

The Extent of Seasonally Suitable Habitats May Limit Forage Fish Production in a Temperate Estuary

The sustained production of sufficient forage is critical to advancing ecosystem-based management, yet factors that affect local abundances and habitat conditions necessary to support aggregate forage production remain largely unexplored. We quantified suitable habitat in the Chesapeake Bay and its tidal tributaries for four key forage fishes: juvenile spotted hake Urophycis regia, juvenile spot Leiostomus xanthurus, juvenile weakfish Cynoscion regalis, and bay anchovy Anchoa mitchilli. We used information from monthly fisheries surveys from 2000 to 2016 coupled with hindcasts from a spatially interpolated model of dissolved oxygen and a 3-D hydrodynamic model of the Chesapeake Bay to identify influential covariates and construct habitat suitability models for each species. Suitable habitat conditions resulted from a complex interplay between water quality and geophysical properties of the environment and varied among species. Habitat suitability indices ranging between 0 (poor) and 1 (superior) were used to estimate seasonal and annual extents of suitable habitats. Seasonal variations in suitable habitat extents in Chesapeake Bay, which were more pronounced than annual variations during 2000–2016, reflected the phenology of estuarine use by these species. Areas near shorelines served as suitable habitats in spring for juvenile spot and in summer for juvenile weakfish, indicating the importance of these shallow areas for production. Tributaries were more suitable for bay anchovy in spring than during other seasons. The relative baywide abundances of juvenile spot and bay anchovy were significantly related to the extent of suitable habitats in summer and winter, respectively, indicating that Chesapeake Bay habitats may be limiting for these species. In contrast, the relative baywide abundances of juvenile weakfish and juvenile spotted hake varied independently of the spatial extent of suitable habitats. In an ecosystem-based approach, areas that persistently provide suitable conditions for forage species such as shoreline and tributary habitats may be targeted for protection or restoration, thereby promoting sufficient production of forage for predators. Further, quantitative habitat targets or spatial thresholds may be developed for habitat-limited species using estimates of the minimum habitat area required to produce a desired abundance or biomass; such targets or thresholds may serve as spatial reference points for management.

Estimated Density, Population Size and Distribution of the Endangered Western Hoolock Gibbon (Hoolock hoolock) in Forest Remnants in Bangladesh

Tropical forests are threatened worldwide due to deforestation. In South and Southeast Asia, gibbons (Hylobatidae) are important to seed dispersal and forest regeneration. Most gibbons are threatened due to deforestation. We studied the western hoolock gibbon (Hoolock hoolock) in Bangladesh to determine population size and extent of suitable habitat. We used distance sampling to estimate density across 22 sites in northeastern and southeastern Bangladesh. We used Maxent modeling to determine areas of highly suitable habitat throughout Bangladesh. Density was estimated to be 0.39 ± 0.09groups/km2, and the total estimated population was 468.96 ± 45.56 individuals in 135.31 ± 2.23 groups. The Maxent model accurately predicted gibbon distribution. Vegetation cover, isothermality, annual precipitation, elevation and mean temperature of the warmest quarter influenced distribution. Two areas in the northeast and two areas in the southeast have high potential for gibbon conservation in Bangladesh. We also found significantly more gibbons in areas that had some level of official protection. Thus, we suggest careful evaluation, comprehensive surveys and restoration of habitats identified as suitable for gibbons. We recommend bringing specific sites in the northeastern and southeastern regions under protection to secure habitat for remaining gibbon populations.

Current and potential carbon stock in the forest communities of the Białowieża Biosphere Reserve

Specifying the upper bound of C storage in forest ecosystems allows an estimate of the amount of C that can be stored in the future. The Białowieża Forest in NE Poland is the last relic forest in the European lowlands. Still, it has been subject to various natural and human-induced disturbances and its C stock has been reduced. The main goal of our study was therefore to assess the current and potential C stock in the forest communities of the Białowieża Biosphere Reserve (597 km2), taking into account the diversity of habitats as well as different protection and management practices. For this we identified 13 forest communities and quantified their current C stock stored in all major pools (living trees, deadwood and soil). We used vegetation and soil data collected in 2018 at 1391 systematically distributed 0.04 ha forest plots (sampling grid 650 × 650 m). We used the concept of potential natural vegetation (PNV) and randomized upscaling of plot level current biomass C stock values to estimate the upper bounds of biomass C stocks possible to obtain at the stand level. We showed that the Białowieża Forest stores currently 300 Mg C ha−1 (17.2 Tg C), of which 41% is accumulated in biomass, with significant variation among different forest communities and management regimes. We obtained the upper bounds of biomass C stocks ranging from 94 Mg ha−1 for swamp pine forest to 223 Mg ha−1 for lime-oak-hornbeam forest. We estimated the gap between the current and potential C stock in biomass at 66 Mg ha−1 (3.8 Tg); 62% of the potential level is achieved in managed forests, and 76% in the National Park. Our findings may be used in planning forest management aimed toward long-term C storage, and the obtained upper bounds can serve as benchmarks in assessing C storage potential of similar forest types elsewhere. We also suggest that the potential of ecosystems to store C should be considered in the landscape context, i.e. by taking into account the spatial extent of PNV habitats and their unequal capacity to provide C storage service.