Changes In Population Density Research Articles

Demographic differentiation among pioneer tree species during secondary succession of a Neotropical rainforest

Abstract Early pioneer species share life histories enabling them to colonize disturbed sites, but how much they differ demographically and how such differentiation determines pioneer species turnover during succession are still open questions. Here, we approached these issues by comparing the demography of dominant pioneer tree species during the secondary succession of tropical rainforest in Southeast Mexico. We assessed changes in population density, population structure, vital rates and intrinsic population growth rate (r) of the pioneer species Trema micrantha, Cecropia peltata and Trichospermum mexicanum during the first 35 years of succession. For this, we combined chronosequence and long‐term (from 2000 to 2018) data from 14 abandoned cornfields with 0.5–35 years fallow age. Trema colonized and disappeared first during succession (<15 years), followed by Cecropia (<28) and Trichospermum (>31). All species exhibited hump‐shaped successional trajectories of population density and biomass with Trema reaching a peak first, followed by Cecropia and later Trichospermum. Species exhibited a fast reduction in r with fallow age, with Trema reaching negative growth rates (r < 0) in the third, Cecropia in the fourth, and Trichospermum in the seventh year of succession. Recruitment, growth and mortality rates of seedlings and juveniles defined the period of population increase and the age of succession at which each species reached maximum density and biomass. The mortality rate in mature stages determined how long each species persisted during succession. An important variation in species replacement occurred among study sites. In some sites, one species was abundant and the others were almost absent, while it was the opposite in other sites. We inferred that priority inhibitory effects operated among species during the field colonization. Synthesis. Although Trema, Cecropia and Trichospermum are considered typical pioneer trees, these species differed importantly in their demographic attributes during succession. The speed at which r declined with age of succession indicated the moment at which each species reached its maximum density and species replacement sequence during succession. However, inter‐specific priority inhibitory effects during field colonization may also be involved in the chance of colonization and replacement between species with similar regeneration strategies.

Climate and land-use changes drive biodiversity turnover in arthropod assemblages over 150 years.

Long-term studies are essential to understand the impacts of global changes on the multiple facets of biological diversity. Here, we use distribution data for over 600 species of arthropods collected over 150 years from locations across Italy and test how multiple environmental stressors (climate, land use and human population density) influenced assemblage composition and functionality. By carefully reconstructing the temporal changes in these stressors, we explicitly tested how environmental changes can determine the observed changes in taxonomic and functional diversity. We found that rapid changes in precipitation destabilize the assemblages and maximize colonization and extinction rates, especially when coupled with changes in human population density (for taxonomy) or temperature (for functionality). Higher microclimatic heterogeneity increases the stability of biodiversity by reducing taxonomic and functional loss. Finally, changes in natural habitats increased colonization, influencing taxonomic nestedness and functional replacement. The integration of long-term datasets combining distributions, climate and traits may deepen our understanding of the processes underlying biodiversity responses to global-scale drivers.

Early Holocene bark-stripping damages as an indicator of large herbivores: Evidence from a submerged Mesolithic landscape in the Haväng area, southern Baltic basin

A unique assemblage consisting of 113 pine samples collected from a submerged Mesolithic landscape in the Haväng area, southern Sweden, was examined to assess the presence of large herbivores, as well as changes in wild-game population density and composition. Bark-stripping damages on prehistoric trees is an extremely underutilized source of information about past game-population dynamics, yet our analyzes of wood samples – dated to around 10 500 cal. yr. BP – shows that such material can be successfully used to study the presence and activities of large herbivores, most likely ungulates. To evaluate our results, comparisons have been made with subfossil peatland trees that grew around 6000 years ago, as well as trees from two present day clearcut logging sites in southern Sweden. Furthermore, studies in a wild-game reserve were performed to recognize and understand different types of damages on trees caused by ungulates. Bark-stripping indicate the presence of ungulates, and the rate of damage is commonly associated with the density of the wild game. Bark-stripping was most frequently observed in the submerged wood material from the early Holocene, where damages were detected in 15% of the trees. In comparisons, 11% of the mid-Holocene trees show bark-stripping damages, whereas marks could be detected in the range between 0% and 6% of the trees from the two present-day clearcut logging sites. Our results show that tree-ring analyzes of prehistoric wood can generate information about wild-game dynamics of the past, and thereby being a valuable complement to more commonly used paleoecological and zooarcheological records.

The Second Wave of COVID-19 and Risk of the Third Wave: Factors Affecting the Continuous Transmission, Spread of, and Increased Mortality Associated With Coronavirus Disease 2019 (COVID-19)

The novel coronavirus disease (COVID-19) originated from China and spread globally within a short period. The spread of the first and second wave of COVID-19 were influenced by factors such as population density and weather changes. Areas that are densely populated have reported increased confirmed cases of COVID-19 compared to less populated areas. The main reason for this could be the fact that it is difficult to practice social distancing in overpopulated countries. With regards to temperature changes, most respiratory infections affect people when temperatures are low. This is exaggerated when there is increased air pollution in the environment. Economic factors have prevented countries to conduct a lockdown of epicentre towns and cities. This is in fear of an economic shut down because some cities are economic cornerstones of countries. Politically, most political leaders have failed to lockdown their countries for the fear of losing political support from their citizens. Further, some traditional and religious beliefs have also influenced the spread of COVID-19, thereby leading to increased morbidity and mortality globally. The spread of COVID-19 has been worsened by peoples negative perceptions and misinformation that COVID-19 is a myth, and thus relax to adhere to the recommended preventive measures. Besides, comorbidities, poor health-seeking behavior, and lack of vaccines, inadequate treatment modalities and test kits have worsened the failure to contain the COVID-19 pandemic. The initiation and implementation of COVID-19 vaccination programs will help reduce the disease burden. However, there is need to improve the awareness and uptake of COVID-19 vaccines globally. Low COVID-19 vaccine acceptability and uptake due vaccine hesitancy have been reported globally. Hence, there is a need for continuous community sensitisation and education programmes and campaigns on the benefits of vaccines in containing disease outbreaks.

Bayesian Skyline Plots disagree with range size changes based on Species Distribution Models for Holarctic birds.

During the Quaternary, large climate oscillations impacted the distribution and demography of species globally. Two approaches have played a major role in reconstructing changes through time: Bayesian Skyline Plots (BSPs), which reconstruct population fluctuations based on genetic data, and Species Distribution Models (SDMs), which allow us to back-cast the range occupied by a species based on its climatic preferences. In this paper, we contrast these two approaches by applying them to a large data set of 102 Holarctic bird species, for which both mitochondrial DNA sequences and distribution maps are available, to reconstruct their dynamics since the Last Glacial Maximum (LGM). Most species experienced an increase in effective population size (Ne , as estimated by BSPs) as well as an increase in geographical range (as reconstructed by SDMs) since the LGM; however, we found no correlation between the magnitude of changes in Ne and range size. The only clear signal we could detect was a later and greater increase in Ne for wetland birds compared to species that live in other habitats, a probable consequence of a delayed and more extensive increase in the extent of this habitat type after the LGM. The lack of correlation between SDM and BSP reconstructions could not be reconciled even when range shifts were considered. We suggest that this pattern might be linked to changes in population densities, which can be independent of range changes, and caution that interpreting either SDMs or BSPs independently is problematic and potentially misleading.

Ecology of outbreak populations of the western spruce budworm

AbstractWe sampled outbreak populations of western spruce budworm, Choristoneura occidentalis (Lepidoptera: Tortricidae), between 1997 and 2016 in Douglas‐fir forests in the interior of British Columbia, Canada. Annual rates of change in population densities were correlated with generation survival, modulated by egg recruitment via dispersal of moths. Most temporal variation in generation survival was the result of variation in survival of small, non‐feeding larval stages. Survival rates of feeding larval and pupal stages determined the magnitude of generation survival but contributed little to temporal trend. Survival of small larvae was the product of density‐related losses of larvae dispersing to and from hibernation sites and weather‐related stress caused by warm temperatures in late summer and early spring. Overwinter survival improved in cooler years and at higher elevations. Survival of feeding larvae and pupae was associated with mortality by natural enemies, in particular a few species of dominant, ubiquitous endoparasitoids, and an episodic, virulent baculovirus. Recruitment of eggs indicated emigration of gravid moths independent of defoliation but proportional to density of local moths. During periods of increasing and decreasing population densities over a large outbreak area, a marked differential in adult densities among locations resulted in greater than expected per‐capita egg recruitment to areas of relatively low density and vice versa, indicative of net exchange of gravid moths from high‐ to low‐density populations. The result was homogenization of egg densities among locations, apparent synchrony of the outbreak at the large scale, and extended duration of the outbreak at some locations, despite declining generation survival. These results are compared with field studies of the closely related spruce budworm, Choristoneura fumiferana. We suggest our interpretation applies more generally and outbreaks of conifer‐feeding budworms are maintained for several years by compensatory survival of sequential life‐history stages and spatio‐temporal smoothing of densities via dispersal of gravid moths. Parasitoids and pathogens can cause sudden declines in densities, but populations inevitably wane as a result of cumulative degradation of their resource. The interaction and temporal sequence of bottom‐up and top‐down factors explain the similarities and differences in outbreak characteristics within‐ and among‐budworm species.

Flood-induced interspecific interactions in spring-fed tributary as an ecosystem function of heterogeneous river networks

Understanding the migratory community dynamics of river networks is important for maintaining lotic system integrity. River animals migrate to their preferred habitats in spatiotemporally heterogeneous river environments. Spring-fed habitats are uniquely characterized by stable temperature and flow regimes, which create suitable spawning habitats for the chum salmon Oncorhynchus keta. O. keta exhibits “run up” to its birthplace for spawning, especially during floods. Because the eggs deposited by this anadromous fish are nutritious and actively consumed by freshwater animals, the location and timing of O. keta spawning events affect the spatiotemporal accumulation of mobile consumers. In this study, we examined changes in temporal population density in spawning O. keta and a mobile consumer (juvenile O. masou masou) in a lowland, spring-fed tributary in northern Japan during a 48.5-mm autumn rainfall event. In both species, population density increased, and then decreased, after the rainfall event. In O. keta, these changes were closely associated with rainfall intensity, whereas in O. masou masou the peak was delayed until 3 days after the rainfall event. A comparison of the gut contents of O. masou masou sampled from a spring-fed tributary and an adjacent non-spring-fed tributary indicated greater consumption of O. keta eggs in the spring-fed tributary. These results suggested that preferential migration of O. keta into spring-fed tributaries for spawning induces subsequent accumulation of juvenile O. masou masou, in turn increasing O. keta egg consumption. These findings improve our understanding of community dynamics during floods in a heterogeneous river network environment.

Crowd counting method based on cross column fusion attention mechanism

Deep learning has made substantial progress in crowd density estimation, but there are still some problems in existing methods, such as large population density, background interference, and scale change, which makes it difficult to count people. To solve the above problems, we proposed a crowd counting method based on a cross column fusion attention mechanism. First, the first ten layers of VGG16 with good migration ability and feature extraction ability are used as the front-end network to preliminarily extract human head features. Then, a cross column fusion attention module is designed. In this module, feature maps are fused across columns to make the network contain richer deep and shallow features. At the same time, to alleviate the background interference, the attention mechanism is used to guide the network to focus on the head position in the picture, and different weights are assigned to different positions according to the attention score map, so as to highlight the crowd and weaken the background, and finally get a high-quality density map. In addition, a shallow convolution module is designed as another branch. The output feature map of the shallow convolution module and the output feature map of the attention module of cross column fusion are fused to solve the problem of scale change effectively. Finally, in the last layer of the network, the convolution layer of 1 × 1 is used to replace the full connection layer, and fewer network parameters are used to reduce the calculation and the population density map is regressed. The experimental results show that the mean absolute error and mean square error of the proposed algorithm are significantly reduced compared with the comparison algorithm.

Effects of historical co‐infection on host shift abilities of exploitative and competitive viruses

Rapid evolution contributes to frequent emergence of RNA viral pathogens on novel hosts. However, accurately predicting which viral genotypes will emerge has been elusive. Prior work with lytic RNA bacteriophage ɸ6 (family Cystoviridae) suggested that evolution under low multiplicity of infection (MOI; proportion of viruses to susceptible cells) selected for greater host exploitation, while evolution under high MOI selected for better intracellular competition against co-infecting viruses. We predicted that phage genotypes that had experienced 300 generations of low MOI ecological history would be relatively advantaged in initial growth on two novel hosts. We inferred viral growth through changes in host population density, specifically by analyzing five attributes of growth curves of infected bacteria. Despite equivalent growth of evolved viruses on the original host, low MOI evolved clones were generally advantaged relative to high MOI clones in exploiting novel hosts. However, the specific attributes of growth curves that supported their advantage differed by host, indicating interactions between both viral and host genotype. Although there will be host specificity in viral growth, we suggest based on infectivity differences of viruses from high versus low MOI histories that prior MOI selection can later affect emergence potential.

Monitoring the extent and impacts of watershed urban development in the Lake Victoria Basin, Kenya, using a combination of population dynamics, remote sensing and GIS techniques

Abstract Several urban centres of different sizes have developed over time, and continue to grow, within the basin of Lake Victoria. Uncontrolled urban development, especially along the lake shore, puts environmental pressure on Lake Victoria and its local ecosystem. This study sought to monitor the extent and impacts of urban development (as measured by population growth and built-up land use/land cover) in the Lake Victoria basin, Kenya, between 1978 and 2018. Remote sensing and GIS-based land use/land cover classification was conducted to extract change in built-up areas from Landsat 3, 4, 5 and 8 satellite imagery obtained for the month of January at intervals of ten years. Change in population distribution and density was analysed based on decadal census data from the Kenya National Bureau of Statistics between 1979 and 2019. A statistical regression model was then estimated to relate population growth to built-up area expansion. Results indicate that the basin’s built-up area has expanded by 97% between 1978 and 2018 while the population increased by 140% between 1979 and 2019. Urban development was attributed to the rapidly increasing population in the area as seen in a positive statistical correlation (R2=0.5744) between increase in built-up area and population growth. The resulting environmental pressure on the local ecosystem has been documented mainly in terms of degradation of lake water quality, eutrophication and aquatic biodiversity loss. The study recommends the enactment and implementation of appropriate eco-sensitive local legislation and policies for sustainable urban and rural land use planning in the area. This should aim to control and regulate urban expansion especially in the immediate shoreline areas of the lake and associated riparian zones.

The link between climate change and biodiversity of lacustrine inhabitants and terrestrial plant communities of the Uvs Nuur Basin (Mongolia) during the last three millennia

The paper is focused on changes in biodiversity, the environment, and human activity in the Uvs Nuur Basin during the last three millennia based on biological and geochemical proxies from the lake Bayan Nuur. Regions with high biodiversity and relatively low anthropogenic pressures are typically the most vulnerable to both climate change and human activities. One such area is the Uvs Nuur Basin located on the north of the Great Lake Depression of Mongolia. The main objective of this study is to assess changes in the past biodiversity of the lake’s microflora and microfauna, and surrounding vegetation biodiversity in the Uvs Nuur Basin, and to determine the main drivers of diversity change. Based on the analysis of pollen and chironomids we conclude that the most humid and afforested phase was between 1400 and 1800 CE. We assume that the Little Ice Age in the Uvs Nuur Basin was humid with mean annual precipitation ca. 305 mm/year and mean July temperature about 13°C. Conversely, the warmest and most arid period was between 650 and 1350 CE with mean annual precipitation ca. 280 mm/year and mean July temperature of about 16°C, attributed to the Medieval Warm Period. The biodiversity of terrestrial plants, chironomids, and Cladocera positive react to changes in annual precipitation and July temperature, whereas diatoms do not correlate directly to the climatic factors. The diversity and the evenness of plants are strongly correlated with the change in the leading biomes. The calculated species turnover suggests no significant changes in plant and Cladocera taxa composition, but significant changes in diatom and chironomid communities. This may be explained by the instability of lake ecology due to the fluctuation of the salinity and acidity of the water. An additional aim was to assess if dung fungi in lacustrine sediments reflect changes in human population density around the lake. We found that neither historical sources of human presence nor the influx of coprophilous fungi are correlated with the inferred climate changes. Coprophilous fungi can be used as individual or additional sources of assessment for the peopling and human-related herbivore density including overgrazing of the studied area.

Urban Densification and Physical Activity Change: A 12-Year Longitudinal Study of Australian Adults.

Urbanization, a major force driving changes in neighborhood environments, may affect residents' health by influencing their daily activity levels. We examined associations of population density changes in urban areas with adults' physical activity changes over 12 years using data from the Australian Diabetes, Obesity and Lifestyle Study (1999-2012). The analytical sample contained 2,354 participants who remained at the same residential address throughout the study period in metropolitan cities and regional cities (42 study areas). Census-based population density measures were calculated for 1-km-radius buffers around their homes. Population density change was estimated using linear growth models. Two-level linear regression models were used to assess associations between changes in population density and changes in self-reported walking and physical activity durations. The average change in population density was 0.8% per year (range, -4.1 to 7.8) relative to baseline density. After adjustment for confounders, each 1% annual increase in population density was associated with 8.5-minutes/week (95% confidence interval: 0.6, 16.4) and 19.0-minutes/week (95% confidence interval: 3.7, 34.4) increases in walking and physical activity, respectively, over the 12-year study period. Increasing population density through urban planning policies of accommodating population growth within the existing urban boundary, rather than expanding city boundaries, could assist in promoting physical activity at the population level.

Density‐dependent age of first reproduction as a key factor for population dynamics: stable breeding populations mask strong floater declines in a long‐lived raptor

AbstractThe age at which individuals reproduce for the first time is a key demographic factor impacting population dynamics and is subject to substantial variation across animal populations. There is also widespread empirical evidence that age of first reproduction responds to changes in population density over time, especially for long‐lived birds and mammals. The density dependence in age of first reproduction has profound impacts on the size of the non‐breeding (‘floater’) part of the population. A better understanding of floater dynamics in raptor populations is urgently needed for comprehensive assessments of conservation status and management. We use the European near‐endemic red kite Milvus milvus, a long‐lived raptor of conservation concern, as an example to investigate total population dynamics with an age‐structured demographic model. Using published estimates of survival and reproduction, we model the red kite population in Germany over four decades, considering also density dependence in the age of first reproduction in different model scenarios. Based on the literature and the results of our simulations, we show that age of first reproduction for the red kite most likely responds non‐linearly to density and that this general feedback mechanism should regularly be considered in demographic simulations. Our model results have far‐reaching implications for the conservation status of the red kite, as they highlight a drastic decrease of juvenile and non‐breeding individuals in the population over time – driven both by declining vital rates and a density‐dependent shift towards a younger age of first breeding. This process is not visible when judged only by the size of the breeding population, which our model estimates to be of similar size today as in the 1980s. The total red kite population reconstructed for Germany, however, seems diminished to nearly 50% of its former size.

Personality traits, sex and food abundance shape space use in an arboreal mammal

Animal space use is affected by spatio-temporal variation in food availability and/or population density and varies among individuals. This inter-individual variation in spacing behaviour can be further influenced by sex, body condition, social dominance, and by the animal’s personality. We used capture-mark-recapture and radio-tracking to examine the relationship between space use and personality in Eurasian red squirrels (Sciurus vulgaris) in three conifer forests in the Italian Alps. We further explored to what extent this was influenced by changes in food abundance and/or population density. Measures of an individual’s trappability and trap diversity had high repeatability and were used in a Principal Component Analysis to obtain a single personality score representing a boldness-exploration tendency. Males increased home-range size with low food abundance and low female density, independent of their personality. However, bolder males used larger core-areas that overlapped less with other males than shy ones, suggesting different resource (food, partners) utilization strategies among personality types. For females, space use-personality relationships varied with food abundance, and bolder females used larger home ranges than shy ones at low female density, but the trend was opposite at high female density. Females’ intrasexual core-area overlap was negatively related to body mass, with no effect of personality. We conclude that relationships between personality traits and space use in free-ranging squirrels varied with sex, and were further influenced by spatio-temporal fluctuations in food availability. Moreover, different personality types (bold-explorative vs. shy) seemed to adopt different space-use strategies to increase access to food and/or partners.

Comparison of the trend moment and double moving average methods for forecasting the number of dengue hemorrhagic fever patients

Spread of Dengue Hemorrhagic Fever (DHF) is influenced by an increase in air temperature due to changes in weather and population density so that there is a lot of exchange of dengue virus through the bite of the Aedes aegypti mosquito. Forecasting models are needed to predict the number of DHF patients in the future so that monitoring of the number of DHF patients can be carried out as anticipation and consideration of decision making. Forecasting the number of patients is based on actual data within 2 (two) previous years by comparing the two methods, namely trend moment and double moving average. To measure the accuracy of the forecasting results from the two forecasting methods, tracking signal and moving range are used. Based on the test results, it shows that the forecasting results are said to be good because no one has passed the upper control limit and lower control limit values so that the difference between the actual data and the forecasting results is not too significant and the trend moment more recommended because the difference in actual data and forecasting results are approached and shown in the pattern graph by looking at the data difference in each period.

Do Rail Transit Stations Affect the Population Density Changes around Them? The Case of Dallas-Fort Worth Metropolitan Area

This study investigates changes in population density in 454 block groups within a one-mile buffer around rail transit stations (the study area) in the Dallas-Fort Worth (DFW) metropolitan area. The research uses three analysis approaches to explore a correlation between proximity to rail stations and population density changes. Changes in population density between 2000 and 2014 are calculated. Changes in population density in the study area are compared to the remainder of the block groups within the four counties served by the same rail transit systems. An innovative approach is employed to select the best regression model using the data of the study area. A relationship between the independent variables and the changes in population density is formulated. The proximity of block groups in the study area to the nearby highway ramps or city centers is also investigated during the study period. Results show that it has a positive impact on population density. Changes in population density within the block groups located beyond the one-mile buffer, especially toward outlying areas, are greater than those within the one-mile buffer. Unexpectedly, it is found that an increase in the percentage of employed and white residents leads to an increase in population density. Other interesting results show that the number of jobs is in inverse proportion to the population density. However, block groups that are developed as part of transit-oriented development (TOD) are dramatically higher in population density than the other block groups. These results represent a beneficial contribution to the field of urban planning. Urban planners and policymakers can also use the findings to adopt specific policies for increasing density, advancing rail transit systems’ success, increasing transit usage, and sustaining station area development.

Land Pattern of Highly Urbanizing Cities: Change in Built-up Area, Population Density and Spatial Development of the Sprawling Dar es Salaam City

Dar es Salaam is one of the most diverse cities in Tanzania in terms of its physical, social, economic, environmental and spatial features. This diversity has contributed to differences in built-up area, population density, as well as the pace of spatial development across different parts of the city. This study aims to examine the relationship between physical built-up area changes in Dar es Salaam, population density change and spatial development using remote sensing images and census data. The study finds that the city population has grown tremendously, with peri-urban wards in particular having experienced positive growth. Dar es Salam’s built-up area change and urban sprawl emerging at the city’s edges distinctly follows the pattern of demographic change. This is accompanied by substantial compact growth in the inner parts of the city. A number of factors such as transport, residential development, migration, high natural growth rates, public policies and land speculation are found to have contributed to these changes. Overall, the study aims to aid planning authorities in effectively responding to the rapid spatial development taking place in the city, for which a holistic approach that combines an understanding of physical and demographic changes is needed. By investigating the changing patterns in land use within this highly urbanizing city, it aims to generate insights into urban development control machineries and identify their underlying dynamics.

Do changes in skull size of South American sea lions reflect changes in population density?

AbstractPopulations of the South American sea lion (SASL, Otaria byronia) have been intensely exploited for leather and oil in different parts of its distribution range throughout the 19th and 20th centuries, generating large changes in abundance. In Patagonia, the SASL population was reduced by more than 90% of its original abundance, and it began to recover after sealing ended. The aim of this work was to assess changes in size and shape of the skull related to changes in population abundance during the last 100 years. Using geometric morphometry techniques, we analyzed 145 individuals (68 males and 77 females) from Patagonia. Skulls were classified by sex, time period (harvest vs. postharvest), and decades of individual's birth. Results indicated that there were differences in skull size but not in shape discriminated by time period. Moreover, individuals of the postharvest period showed a decrease in the skull size during the last two decades, coinciding with the recovery in population abundance. Our results suggest the existence of a density‐dependence response in somatic growth of SASL population of Patagonia.

Threatened bird species are concentrated in regions with less historical human impacts

Previous human activities have a lasting influence on modern biodiversity patterns, especially on the distribution of threatened species. China is a large country, with a high population and a long history of agriculture, but is also a megadiverse country, with over 1370 bird species and over 300 threatened bird species. As far as we know, this study is the first attempt to test the associations between distribution of proportion of threatened bird species and anthropogenic activities (changes in forest cover, cropland area and population density) over different periods (between 1700 and 1800, between 1800 and 1900, and between 1900 and 2000). We show that there are higher proportions of threatened bird species in Northern China, especially Northeastern and Northwestern China. Notably, both ordinary least squares models and simultaneous autoregressive models indicate that higher proportions of threatened bird species were largely associated with less historical anthropogenic activities, i.e., smaller changes in forest cover and cropland area in Northern China between 1700 and 1800. These findings emphasize the role of historical land use changes in shaping current distribution of threatened bird species, and highlight the importance of avoiding further anthropogenic activities in the last-of-the-wild regions for biodiversity conservation.

Capturing response differences of species distribution to climate and human pressures by incorporating local adaptation: Implications for the conservation of a critically endangered species

Considering local adaptation has been increasingly involved in forecasting species distributions under climate change and the management of species conservation. Herein, we take the critically endangered Chinese giant salamander (Andrias davidianus) that has both a low dispersal ability and distinct population divergence in different regions as an example. Basin-scale models that represent different populations in the Huanghe River Basin (HRB), the Yangtze River Basin (YRB), and the Pearl River Basin (PRB) were established using ensemble species distribution models. The species ranges under the future human population density (HPD) and climate change were predicted, and the range loss was evaluated for local basins in 2050 and 2070. Our results showed that the predominant factors affecting species distributions differed among basins, and the responses of the species occurrence to HPD and climate factors were distinctly different from northern to southern basins. Future HPD changes would be the most influential factor that engenders negative impacts on the species distribution in all three basins, especially in the HRB. Climate change will likely be less prominent in decreasing the species range, excluding in the YRB and PRB under the highest-emissions scenario in 2050. Overall, the high-emissions scenario would more significantly aggravate the negative impacts produced by HPD change in both 2050 and 2070, with maximum losses of species ranges in the HRB, YRB, and PRB of 83.4%, 60.0%, and 53.5%, respectively, under the scenarios of the combined impacts of HPD and climate changes. We proposed adapted conservation policies to effectively protect the habitat of this critically endangered animal in different basins based on the outcomes. Our research addresses the importance of incorporating local adaptation into species distribution modeling to inform conservation and management decisions.