Many African large carnivore populations are declining due to decline of the herbivore populations on which they depend. The densities of apex carnivores like the lion and spotted hyena correlate strongly with prey density, but competitive subordinates like the African wild dog benefit from competitive release when the density of apex carnivores is low, so the expected effect of a simultaneous decrease in resources and dominant competitors is not obvious. Wild dogs in Zambia’s Luangwa Valley Ecosystem occupy four ecologically similar areas with well-described differences in the densities of prey and dominant competitors, due to spatial variation in illegal offtake. We used long-term data to fit a Bayesian integrated population model (IPM) of the demography and dynamics of wild dogs in these four regions. The IPM used Leslie projection to link a Cormack-Jolly-Seber model of area-specific survival (allowing for individual heterogeneity in detection), a zero-inflated Poisson model of area-specific fecundity, and a state-space model of population size that used estimates from a closed mark-capture model as the counts from which (latent) population size was estimated. The IPM showed that both survival and reproduction were lowest in the region with the lowest density of preferred prey (puku, Kobus vardonii, and impala, Aepyceros melampus), despite little use of this area by lions. Survival and reproduction were highest in the region with the highest prey density, and intermediate in the two regions with intermediate prey density. The population growth rate (λ) was positive for the population as a whole, strongly positive in the region with the highest prey density, and strongly negative in the region with the lowest prey density. It has long been thought that the benefits of competitive release protect African wild dogs from the costs of low prey density. Our results show that the costs of prey depletion overwhelm the benefits of competitive release and cause local population decline where anthropogenic prey depletion is strong. Because competition is important in many guilds and humans are affecting resources of many types, it is likely that similarly fundamental shifts in population limitation are arising in many systems.

Methods Data on the survival and reproduction of African wild dogs (Lycaon pictus) were collected by radiocollaring and direct observation in the Luangwa Valley ecosystem. The raw data were entered into a relational database (MS Access) and exported to CSV files using SQL queries.

1. Population decline is associated with increased vulnerability to extinction, but also with possible density-, frequency-, or distance-related 'rarity advantages' that increase recruitment success as individuals become isolated from their congeners. Distinguishing between these alternatives (risk versus recovery of rare populations via demographic processes) has become critical, given how anthropogenic disturbances are causing population declines globally. 2. Here, we demonstrate how distance-related rarity advantages are evident in spatially isolated recruits of a canopy-dominant but regionally rare species of oak that appears to be suffering recruitment collapse. As distance from parent trees increased, seedlings had significantly more leaves and experienced reduced insect browsing and intraspecific competition. Long-term field-based experimental treatments revealed these advantages to be associated with rapid rates of juvenile maturation and survival that are unobserved in natural settings. 3. The discrepancy between the experimental and natural settings was explained by trophic collapse and habitat loss - two changes ubiquitous to many terrestrial ecosystems – that combine to concentrate vertebrate herbivores in habitat remnants and cause 100% juvenile mortality via the browsing of taller juveniles. Exotic grass cover, long associated with oak recruitment failure, significantly suppressed seedling height and leaf production, but appeared to delay mortality by hiding shorter seedlings from vertebrate herbivores. 4. Synthesis. Our work demonstrates how rarity advantages have the potential to positively influence the population performance of a declining species, but are short-circuited by intense herbivory associated with human-based environmental change. Regionally, there appear to be few existing conditions on the contemporary landscape that favor juvenile survival, suggesting ongoing recruitment difficulties without intervention. Our work clarifies how extinction risk can in some cases be best defined by how anthropogenic disturbances affect, and are offset by, demographic-based persistence mechanisms, than simply by present-day abundance or distribution.

1. Road-side amphibian citizen science programs bring together volunteers focused on collecting scientific data while working to mitigate population declines by directly reducing road mortality of pond-breeding amphibians. Despite the international popularity of these movement-based road-side conservation efforts (i.e., 'big nights', 'bucket brigades' and 'toad patrols'), direct benefits to conservation have rarely been quantified or evaluated. 2. As a case study, we used a population simulation approach to evaluate how volunteer intensity, frequency and distribution influence three conservation outcomes (minimum population size, population growth rate, and years to extinction) of the spotted salamander (Ambystoma maculatum) – a common, focal pond-breeding amphibian of citizen science and conservation programs in the United States. 3. Sensitivity analysis supported the expectation that populations were primarily recruitment-driven. Thus, conservation outcomes were highest when volunteers focused on out-migration of metamorphs as opposed to in-migration of adults –contrary to the typical timing of such volunteer events. 4. Almost every volunteer strategy resulted in increased conservation outcomes compared to a no-volunteer strategy. Specifically, volunteer frequency during metamorph migration increased outcomes more than the same increases in volunteer effort during adult migration. Small population sizes resulted in a negligible effect of volunteer intensity. Volunteers during the first adult in-migration had a relatively small effect compared to most other strategies. 5. Synthesis and applications. Although citizen science focused conservation actions could directly benefit declining populations, other conservation measures are additionally needed to halt or reverse local amphibian declines. This study demonstrates a need to evaluate the effectiveness of focusing citizen science mitigation efforts on the metamorph stage, as opposed the adult stage, which may be challenging, compared to other management actions such as road-crossing infrastructure. Current amphibian citizen science programs will be challenged to balance implementing evidence-based conservation measures on the most limiting life stage while retaining the social and community benefits to volunteers.

The graph shows the population growth in China from 2000 to 2024. In 2024, the Chinese population decreased by about 0.1 percent or 1.39 million to around 1.408 billion people. Declining population growth in China Due to strict birth control measures by the Chinese government as well as changing family and work situations of the Chinese people, population growth has subsided over the past decades. Although the gradual abolition of the one-child policy from 2014 on led to temporarily higher birth figures, growth rates further decreased in recent years. As of 2024, leading countries in population growth could almost exclusively be found on the African continent and the Arabian Peninsula. Nevertheless, as of mid 2024, Asia ranked first by a wide margin among the continents in terms of absolute population. Future development of Chinese population The Chinese population reached a maximum of 1,412.6 million people in 2021 but decreased by 850,000 in 2022 and another 2.08 million in 2023. Until 2022, China had still ranked the world’s most populous country, but it was overtaken by India in 2023. Apart from the population decrease, a clear growth trend in Chinese cities is visible. By 2024, around 67 percent of Chinese people lived in urban areas, compared to merely 36 percent in 2000.

Although territorial animals are able to maintain exclusive use of certain regions of space, movement data from neighboring individuals often suggest overlapping home ranges. To explain and unify these two aspects of animal space use, we use recently developed mechanistic models of collective animal movement. We apply our approach to a natural experiment on an urban red fox (Vulpes vulpes) population that underwent a rapid decline in population density due to a sarcoptic mange epizooty. By extracting details of movement and interaction strategies from location data, we show how foxes alter their behavior, taking advantage of sudden population-level changes by acquiring areas vacated due to neighbor mortality, while ensuring territory boundaries remain contiguous. The rate of territory border movement increased eightfold as the population declined and the foxes’ response time to neighboring scent reduced by a third. By demonstrating how observed, fluctuating territorial patterns emerge from movements and interactions of individual animals, our results give the first data-validated, mechanistic explanation of the elastic disc hypothesis, proposed nearly 80 years ago.

In 2024, the total population of Taiwan increased to approximately 23.4 million people. The significant drop in 2021 and 2022 was mainly due to people leaving the island during the coronavirus pandemic, while the natural growth rate was also slightly negative. The return of many people in 2023 led to a growth in population. According to national statistics and projections, population numbers entered a general declining path in 2020. Taiwan's demographic development Taiwan experienced rapid population growth in the 1950s and 60s, but alongside with economic development, growth rates decreased significantly. Falling birth figures have also been attributed to Taiwan’s family planning policy, which was aimed at keeping population growth at check. This led to a situation on the island where overall population density was very high and still growing, while the total fertility rate dropped quickly and eventually reached extremely low levels compared internationally. In the 21st century, the challenges of a quickly aging society became more and more apparent and the government initiated family friendly and birth promoting policies. However, fertility still kept on decreasing and reached a historical low in 2010 at 0.9 births per woman on average, and only in recent years has the number of births increased slightly. Implications of an aging society Today's Taiwan, like many East Asian societies, faces the challenges of a rapidly aging population. While the share of the population aged 65 and older accounted to around 18 percent in 2023, it is projected to reach 43 percent in 2060. The old-age dependency ratio, which denotes the relation of people of 65 years and above to the working-age population, is expected to reach around 87 percent in those years. This puts heavy pressure on the working people and the economy as a whole. However, compared to mainland China, which is in a very much comparable demographic situation, Taiwan enjoys the advantage of a relatively wealthy society, which helps to curb the negative economic effects of an aging population.

Aim: Habitat loss and climate change constitute two of the greatest threats to biodiversity worldwide, and theory predicts that these factors may act synergistically to affect population trajectories. Recent evidence indicates that structurally complex old-growth forest can be cooler than other forest types during spring and summer months, thereby offering potential to buffer populations from negative effects of warming. Old growth may also have higher food and nest-site availability for certain species, which could have disproportionate fitness benefits as species approach their thermal limits. Location: Pacific Northwestern United States. Methods: We predicted that negative effects of climate change on 30-year population trends of old-growth-associated birds should be dampened in landscapes with high proportions of old-growth forest. We modelled population trends from Breeding Bird Survey data for 13 species as a function of temperature change and proportion old-growth forest. Results: We found a significant negative effect of summer warming on only two species. However, in both of these species, this relationship between warming and population decline was not only reduced but reversed, in old-growth-dominated landscapes. Across all 13 species, evidence for a buffering effect of old-growth forest increased with the degree to which species were negatively influenced by summer warming. Main conclusions: These findings suggest that old-growth forests may buffer the negative effects of climate change for those species that are most sensitive to temperature increases. Our study highlights a mechanism whereby management strategies to curb degradation and loss of old-growth forests—in addition to protecting habitat—could enhance biodiversity persistence in the face of climate warming.

Extinctions are predicted to rise by an order of magnitude over the next century. Although contemporary documented extinctions are uncommon, local extirpations likely provide hints about global extinction risks. Comparing responses to global change of locally extinct versus extant species pairs in a phylogenetic framework could highlight why certain species are more vulnerable to extinction than others and which anthropogenic changes are most relevant to their decline. As anthropogenic changes likely interact to affect population declines, demographic studies partitioning the effects of multifactorial stressors are needed but remain rare. I examine demographic responses to nitrogen addition and deer herbivory, two major drivers of species losses in grasslands, in experimental reintroductions of fourteen locally extinct and extant confamilial native plants from Michigan prairies. Nitrogen consistently reduces survival, especially in locally extinct species, and growth of locally extinct species benefits less from nitrogen than growth of extant species. Nitrogen reduces population growth rates, largely via reductions in survival. Deer herbivory, meanwhile, had inconsistent effects on vital rates among species and did not affect population growth. Nitrogen and herbivory rarely interacted to affect vital rates. These results link community-level patterns of species loss under nitrogen addition to the population-level processes underlying those losses.

1. Conservation translocations are becoming more common to assist in the management of threatened native species. While many translocation programs focus on maximizing survival in newly established populations, consideration is also required for the persistence of source populations. 2. Here, we present and test a theoretical framework that assesses the translocation trade-off between increasing a species probability of survival and decreasing a species’ overall genetic diversity. We anticipate that i) the genetic diversity of translocated populations will be reduced compared to the source due to a failure to capture and retain genetic diversity, and ii) the genetic diversity of the source population will decline due to the removal of founder individuals. 3. We test this framework with an empirical study of redfin blue eye, Scaturiginichthys vermeilipinnis; a critically endangered fish species which has undergone several replicate translocations, established with founders sourced from a...

Warmer springs may cause animals to become mistimed if advances of spring timing, including available resources, and of timing of breeding occur at different speed. We used thermal sums (cumulative sum of degree days) during spring to describe the thermal progression (timing) of spring and investigate its relationship to breeding phenology and demography of a long-distant migrant bird, the northern wheatear (Oenanthe oenanthe L.). We first compare 20-year trends in spring timing, breeding time, selection for breeding time and annual demographic rates. We then explicitly test whether annual variation in selection for breeding time and demographic rates associates to the degree of phenological matching between breeding time and thermal progression of spring. Both thermal progression of spring and breeding time of wheatears advanced in time during the study period. But despite breeding on average 7 days earlier with respect to date, wheatears bred about 4 days later with respect to thermal...

Population size estimates refer to estimates provided by Palomero and co-authors [26]. Numbers of deaths, compiled by the authors of this paper, are presented by period and sex. Details on each death report are provided in supplementary information (S1 Table).

Aim. Halting widespread biodiversity loss will require detailed information on species’ trends and the habitat conditions correlated with population declines. However, constraints on conventional monitoring programs and commonplace approaches for trend estimation can make it difficult to obtain such information across species’ ranges. Here, we demonstrate how recent developments in machine learning and model interpretation, combined with data sources derived from participatory science, enable landscape-scale inferences on the habitat correlates of population trends across broad spatial extents. Location. Worldwide, with a case study in the western United States. Methods. We used interpretable machine learning to understand the relationships between land cover and spatially explicit bird population trends. Using a case study with three passerine birds in the western U.S. and spatially explicit trends derived from eBird data, we explore the potential impacts of simulated land cover modification while evaluating potential co-benefits among species.Results. Our analysis revealed complex, non-linear relationships between land cover variables and species’ population trends as well as substantial interspecific variation in those relationships. Areas with the most positive impacts from a simulated land cover modification overlapped for two species, but these changes had little effect on the third species. Main conclusions. This framework can help conservation practitioners identify important relationships between species trends and habitat while also highlighting areas where potential modifications to the landscape could bring the biggest benefits. The analysis is transferrable to hundreds of species worldwide with spatially explicit trend estimates, allowing inference across multiple species at scales which are tractable for management to combat species declines.

The total population of Germany was estimated at over 84.4 million inhabitants in 2025, although it is projected to drop in the coming years and fall below 80 million in 2043. Germany is the most populous country located entirely in Europe, and is third largest when Russia and Turkey are included. Germany's prosperous economy makes it a popular destination for immigrants of all backgrounds, which has kept its population above 80 million for several decades. Population growth and stability has depended on immigration In every year since 1972, Germany has had a higher death rate than its birth rate, meaning its population is in natural decline. However, Germany's population has rarely dropped below its 1972 figure of 78.6 million, and, in fact, peaked at 84.7 million in 2024, all due to its high net immigration rate. Over the past 75 years, the periods that saw the highest population growth rates were; the 1960s, due to the second wave of the post-WWII baby boom; the 1990s, due to post-reunification immigration; and since the 2010s, due to high arrivals of refugees from conflict zones in Afghanistan, Syria, and Ukraine. Does falling population = economic decline? Current projections predict that Germany's population will fall to almost 70 million by the next century. Germany's fertility rate currently sits around 1.5 births per woman, which is well below the repacement rate of 2.1 births per woman. Population aging and decline present a major challenge economies, as more resources must be invested in elderly care, while the workforce shrinks and there are fewer taxpayers contributing to social security. Countries such as Germany have introduced more generous child benefits and family friendly policies, although these are yet to prove effective in creating a cultural shift. Instead, labor shortages are being combatted via automation and immigration, however, both these solutions are met with resistance among large sections of the population and have become defining political issues of our time.

Details on the brown bear deaths reported in the Cantabrian populations, from 1977 to 2020. (XLSX)

Monitoring population trends of threatened species requires standardized techniques that can be applied over broad areas and repeated through time. Sun bears Helarctos malayanus are a forest dependent tropical bear found throughout most of Southeast Asia. Previous estimates of global population trends have relied on expert opinion and cannot be systematically replicated. We combined data from 1,463 camera traps within 31 field sites across sun bear range to model the relationship between photo catch rates of sun bears and tree cover. Sun bears were detected in all levels of tree cover above 20%, and the probability of presence was positively associated with the amount of tree cover within a 6-km2 buffer of the camera traps. We used the relationship between catch rates and tree cover across space to infer temporal trends in sun bear abundance in response to tree cover loss at country and global-scales. Our model-based projections based on this “space for time” substitution suggested that sun bear population declines associated with tree cover loss between 2000–2014 in mainland southeast Asia were ~9%, with declines highest in Cambodia and lowest in Myanmar. During the same period, sun bear populations in insular southeast Asia (Malaysia, Indonesia and Brunei) were projected to have declined at a much higher rate (22%). Cast forward over 30-years, from the year 2000, by assuming a constant rate of change in tree cover, we projected population declines in the insular region that surpassed 50%, meeting the IUCN criteria for endangered if sun bears were listed on the population level. Although this approach requires several assumptions, most notably that trends in abundance across space can be used to infer temporal trends, population projections using remotely sensed tree cover data may serve as a useful alternative (or supplement) to expert opinion. The advantages of this approach is that it is objective, data-driven, repeatable, and it requires that all assumptions be clearly stated.

Although matrix improvement in fragmented landscapes is a promising conservation measure, matrix permeability (willingness of an organism to enter the matrix) and movement survival in the matrix are usually aggregated. Consequently, it is unknown which matrix property needs to be improved. It also remains unclear whether matrix upgrading from dispersal passage to providing reproduction opportunities has large conservation benefits and whether there are interactive effects between habitat and matrix management. We examined matrix effects on regional populations across a gradient of habitat loss and fragmentation using simulation experiments that integrated demographic processes and movement modeling based on circuit theory. We separately modified the levels of matrix permeability and movement survival to evaluate their individual effects. We also altered the amount and configuration of not only habitat but also improved matrix to assess their effects on population vital rates (size, surv...

Bee foraging behavior provides a pollination service that has both ecological and economic benefits. However, bee population decline could directly affect the efficiency of this interaction. Among the drivers of this decline, global warming has been implicated as an emerging threat but exactly how increasing temperatures affect bee foraging behavior remains unexplored. Here, we assessed how exposure to elevated temperatures during development affects the foraging behavior and morphology of workers from commercial and wild Bombus terrestris colonies. Workers reared at 33°C had a higher visiting rate and shorter visiting time than those reared at 27°C. In addition, far fewer workers reared at 33°C engaged in foraging activities and this is potentially related to the drastic reduction in the number of individuals produced in colonies exposed to 33°C. The impact of elevated developmental temperature on wild colonies was even stronger as none of the workers from these colonies performed any foraging trips. We also found that rearing temperature affected wing size and shape. Our results provide the first evidence that colony temperature can have striking effects on bumblebee foraging behavior. Of particular importance is the drastic reduction in the number of workers performing foraging trips, and the total number of foraging trips made by workers reared in high temperatures. Further studies should explore if, ultimately, these observed effects of exposure to elevated temperature during development lead to a reduction in pollination efficiency.

Quercus chungii, a rare and endangered endemic tree species, is found exclusively in subtropical regions of China. Understanding the population structure and temporal dynamics of Q. chungii is pivotal for effective conservation and restoration of its populations and associated ecosystems. However, large knowledge gaps remain about its population structure and temporal change, and its key demographic rates across size classes. In this study, we investigated the population structures of Q. chungii in 2013 and 2023 in a nature reserve specifically established to better conserve this species and its associated ecosystems. We found that Q. chungii increased in its overall abundance, and tree size in the past decade, suggesting active regeneration and a rapid growth rate for this species and the effectiveness of past conservation efforts. The age structure in 2023 showed a pyramid shape, with a sharp decline in the numbers of individuals from germinated seeds to seedlings and from seedlings to saplings. These led to the low numbers of seedlings and saplings and high age-specific death probabilities at the early developmental stages. These results indicated potential risks of future population decline. These risks may have already manifested over the past decade, as a high mortality rate during the seedling-to-sapling transition could be one of the primary reasons contributing to the decreased proportion of saplings in 2023 compared to 2013. We propose that future studies may benefit from in-depth studies on the regeneration processes of Q. chungii by considering seed predation and germination under changing climate. This study improves the prediction of population development of Q. chungii, thereby offering theoretical guidance essential for its conservation.

The statistic shows the total population of India from 2019 to 2029. In 2023, the estimated total population in India amounted to approximately 1.43 billion people.

Total population in India

India currently has the second-largest population in the world and is projected to overtake top-ranking China within forty years. Its residents comprise more than one-seventh of the entire world’s population, and despite a slowly decreasing fertility rate (which still exceeds the replacement rate and keeps the median age of the population relatively low), an increasing life expectancy adds to an expanding population. In comparison with other countries whose populations are decreasing, such as Japan, India has a relatively small share of aged population, which indicates the probability of lower death rates and higher retention of the existing population.

With a land mass of less than half that of the United States and a population almost four times greater, India has recognized potential problems of its growing population. Government attempts to implement family planning programs have achieved varying degrees of success. Initiatives such as sterilization programs in the 1970s have been blamed for creating general antipathy to family planning, but the combined efforts of various family planning and contraception programs have helped halve fertility rates since the 1960s. The population growth rate has correspondingly shrunk as well, but has not yet reached less than one percent growth per year.

As home to thousands of ethnic groups, hundreds of languages, and numerous religions, a cohesive and broadly-supported effort to reduce population growth is difficult to create. Despite that, India is one country to watch in coming years. It is also a growing economic power; among other measures, its GDP per capita was expected to triple between 2003 and 2013 and was listed as the third-ranked country for its share of the global gross domestic product.

BackgroundSince 1990, the world’s homicide rate has declined by nearly 20%. While prior research has documented parallel homicide declines across many individual countries, the causes of a shared international homicide decline remain unknown. Drawing on a worldwide process of population ageing, and on research linking age to criminal activity, this study investigates the contribution of global demographic shifts to the international homicide decline.MethodsWe draw from (1) a High Coverage Sample of 126 countries since 1990, and (2) a Long Series Sample of 26 countries since 1960 and utilize fixed-effect regressions to evaluate the impact of age structure on homicide trends. In addition, we use a quantile regression to explore variations in the relationship between age structure and homicide conditional on homicide levels.FindingsResults using the High Coverage Sample suggest no relationship between age structure and homicide. However, results from the Long Series Sample suggest that changes in the relative size of countries’ youth population is a major predictor of homicide trends since 1960. In exploring this divergence, we find that the influence of age structure on homicide becomes less evident as other risk factors for violence gain prominence. Thus, while high homicide countries had the most to gain from falling homicide rates, the safety benefits of an ageing population have been concentrated among the least violent countries.InterpretationWhile the homicide declines of individual countries have often been attributed to domestic policies, the universality of international homicide trends suggests the influence of broader global phenomenon. We find that countries’ homicide trends are strongly associated with changes in the size of their youth populations, particularly where there are few competing criminogenic forces. Based on these results, we propose an explanation for the international homicide decline, while highlighting the importance of demographic patterns in explaining homicide trends.