Aggregate Population Research Articles

Hierarchical assembly and environmental enhancement of bacterial ice nucleators

Bacterial ice nucleating proteins (INPs) are exceptionally effective in promoting the kinetically hindered transition of water to ice. Their efficiency relies on the assembly of INPs into large functional aggregates, with the size of ice nucleation sites determining activity. Experimental freezing spectra have revealed two distinct, defined aggregate sizes, typically classified as class A and C ice nucleators (INs). Despite the importance of INPs and years of extensive research, the precise number of INPs forming the two aggregate classes, and their assembly mechanism have remained enigmatic. Here, we report that bacterial ice nucleation activity emerges from more than two prevailing aggregate species and identify the specific number of INPs responsible for distinct crystallization temperatures. We find that INP dimers constitute class C INs, tetramers class B INs, and hexamers and larger multimers are responsible for the most efficient class A activity. We propose a hierarchical assembly mechanism based on tyrosine interactions for dimers, and electrostatic interactions between INP dimers to produce larger aggregates. This assembly is membrane-assisted: Increasing the bacterial outer membrane fluidity decreases the population of the larger aggregates, while preserving the dimers. Inversely, Dulbecco's Phosphate-Buffered Saline buffer increases the population of multimeric class A and B aggregates 200-fold and endows the bacteria with enhanced stability toward repeated freeze-thaw cycles. Our analysis suggests that the enhancement results from the better alignment of dimers in the negatively charged outer membrane, due to screening of their electrostatic repulsion. This demonstrates significant enhancement of the most potent bacterial INs.

Cardiovascular Disease Mortality Among Native Hawaiian and Pacific Islander Adults Aged 35 Years or Older, 2018 to 2022.

Native Hawaiian and Pacific Islander (NHPI) adults have historically been grouped with Asian adults in U.S. mortality surveillance. Starting in 2018, the 1997 race and ethnicity standards from the U.S. Office of Management and Budget were adopted by all states on death certificates, enabling national-level estimates of cardiovascular disease (CVD) mortality for NHPI adults independent of Asian adults. To describe CVD mortality among NHPI adults. Race-stratified age-standardized mortality rates (ASMRs) and rate ratios were calculated using final mortality data from the National Vital Statistics System for 2018 to 2022. Fifty states and the District of Columbia. Adults aged 35 years or older at the time of death. CVD deaths were identified from International Classification of Diseases, 10th Revision codes indicating CVD (I00 to I99) as the underlying cause of death. From 2018 to 2022, 10 870 CVD deaths (72.6% from heart disease; 19.0% from cerebrovascular disease) occurred among NHPI adults. The CVD ASMR for NHPI adults (369.6 deaths per 100 000 persons [95% CI, 362.4 to 376.7]) was 1.5 times higher than for Asian adults (243.9 deaths per 100 000 persons [CI, 242.6 to 245.2]). The CVD ASMR for NHPI adults was the third highest in the country, after Black adults (558.8 deaths per 100 000 persons [CI, 557.4 to 560.3]) and White adults (423.6 deaths per 100 000 persons [CI, 423.2 to 424.1]). Potential misclassification of underlying cause of death or race group. NHPI adults have a high rate of CVD mortality, which was previously masked by aggregation of the NHPI population with the Asian population. The results of this study support the need for continued disaggregation of the NHPI population in public health research and surveillance to identify opportunities for intervention. National Institute of General Medical Sciences, National Institutes of Health.

Size distribution of aggregates across different aquatic systems around Japan shows that stronger aggregates are formed under turbulence

AbstractMarine aggregates, composed of various particles, play a crucial role in ocean carbon storage. The overall size distribution of the aggregates (number size spectra) is controlled by the balance between aggregation and disaggregation processes. Turbulence has been proposed to facilitate both aggregation and disaggregation by increasing the collision rate of aggregates or sometimes directly tearing them apart. Predominant processes driven by turbulence typically depend on the level of turbulence—relatively weak turbulence is associated with aggregation while stronger turbulence promotes disaggregation. Aggregate strength also plays a key role, as strongly bonded aggregates can withstand turbulence better, leading to lower disaggregation rates. While the relationship between turbulence and aggregate strength has been studied numerically and experimentally, field measurements remain limited. Here, we compare our number size spectra to turbulence intensity from the field measurements across different environmental settings around Japan to determine the effect of turbulence on aggregate strength. We combined measurements from 10 sites with different environmental settings and observed the flatter slopes (higher net aggregation rate) and shifts in the intersection lengths with an increase of turbulence, while strong turbulence is typically linked with disaggregation. Our findings suggested that stronger aggregates are formed under stronger turbulence and the overall population of strong aggregates also increases with an increase of turbulence intensity. We also compared our number size spectra with three other confounding factors (fluorescence, salinity, and aggregate compositions) to confirm the effects of turbulence are dominant in our aggregate dynamics.

Habitat suitability and flood risk modeling for Gazella conservation actions in Mond Protected Area

Extreme floods are recognized as a major factor contributing to high mortality rates in mammalian populations. The primary objective of this study is to map flood hazards and evaluate habitat suitability within the Mond Protected Area (MPA), near the Mond River. This region is particularly important as it serves as a habitat for the vulnerable gazelle (Gazella subgutturosa). Through field surveys and information gathering, the study examines the effects of flooding on the mortality, distribution, and abundance of this gazelle population.The MaxEnt approach was used to assess habitat suitability, while flood hazard zoning was conducted using the HEC-RAS model. Field studies and the resulting flood hazard map identified three specific locations "Barid," "Rudbor," and "Cham Sheikh" where floodwaters infiltrate the protected area. This infiltration is attributed to riverbank erosion and the absence of protective vegetation in the above areas. The extreme flood on March 20, 2017, significantly increased gazelle mortality rates.By analyzing the maps integrating flood zoning, gazelle distribution, and population aggregation within the MPA, along with field surveys, practical and significant operational measures to enhance the gazelle habitat have been identified. One key measure includes establishing low-elevation platforms in areas where gazelles congregate. Six platforms have been designated, with three marked as "priority one" and three as "priority two," as the most effective solution for reducing gazelle casualties within the MPA. This decision considers factors such as the flood zoning map, gazelle presence, and historical data on locations with a substantial casualty of this species during floods.

Promotion Effects of High-Speed Rail on Urban Development: Evidence from Three Lines in China

Amid the vigorous development of the high-speed rail (HSR) network, local governments in China generally consider the construction of HSR as a crucial task in their regional development strategies. Currently, most provincial capitals and prefecture-level cities in the eastern and central regions of China already have operational HSR services. This study aims to examine a key question: has the objective of local governments to promote urban development through the construction of HSR been effective? The research selects cities along the Beijing–Shanghai, Beijing–Guangzhou, and Harbin–Dalian HSR lines as the study subjects. Based on the principles of proximity and similarity, cities with operational HSR and those without are chosen as the experimental group and the control group, respectively. Following the double difference (difference-in-differences) approach, an advantage index is proposed to systematically evaluate the impact of HSR operation on urban development from three dimensions: population aggregation, economic development, and expansion of construction land. Furthermore, the evaluation results are systematically clustered to identify city types that exhibit different promotional effects in various dimensions. The research findings indicate the following: (1) The promotion effect of HSR on the development of small to medium-sized cities is more reflected in economic growth and construction land growth. (2) The promotion effect of HSR on the development of large cities is more reflected in the growth of the employment population. (3) For smaller or economically less-developed cities, HSR may be detrimental to the aggregation of resident and employment populations. (4) Cities with moderate size and good economic development have the opportunity to use HSR to promote population aggregation. On this basis, combined with the findings above, strategies to promote the coordinated development of high-speed rail construction and urban systems are discussed.

High-resolution population maps derived from Sentinel-1 and Sentinel-2

Detailed population maps play an important role in diverse fields ranging from humanitarian action to urban planning. Generating such maps in a timely and scalable manner presents a challenge, especially in data-scarce regions. To address it we have developed Popcorn, a population mapping method whose only inputs are free, globally available satellite images from Sentinel-1 and Sentinel-2; and a small number of aggregate population counts over coarse census districts for calibration. Despite the minimal data requirements our approach surpasses the mapping accuracy of existing schemes, including several that rely on building footprints derived from high-resolution imagery. E.g., we were able to produce population maps for Rwanda with 100m GSD based on less than 400 regional census counts. In Kigali, those maps reach an R2 score of 66% w.r.t. a ground truth reference map, with an average error of only ±10 inhabitants/ha. Conveniently, Popcorn retrieves explicit maps of built-up areas and local building occupancy rates, making the mapping process interpretable and offering additional insights, for instance about the distribution of built-up, but unpopulated areas, e.g., industrial warehouses. With our work we aim to democratize access to up-to-date and high-resolution population maps, recognizing that some regions faced with particularly strong population dynamics may lack the resources for costly micro-census campaigns. Project page: https://popcorn-population.github.io/.

Landscape and insecticide use affecting the Leucoptera coffeella infestation and the natural parasitism spatiotemporal distribution in brazilian coffee agroecosystems

Monitoring the coffee leaf miner and natural parasitism is an important part of integrated pest management, and knowing the spatial distribution patterns of this pest can help improve sampling plans. This study aimed to determine spatial and temporal distributions of the coffee leaf miner infestation and natural parasitism in coffee plantations of different insecticide use and landscape configurations in the Planalto region, Bahia, Brazil. We monitored five coffee farms with different insecticide management practices in insecticide use and landscape features during two seasons, from December 2020 to November 2021. In each coffee farm, four regular grid plots of 30 points were established, for a total of 120 sample points per farm, that were georeferenced. Each point was a group of five coffee plants within 5 m of each other, 30 m in distance. Monthly collections of mined leaves were carried out at each sampling point to determine the L. coffeella infestation and natural parasitism rates. Geostatistical analysis was used to determine the spatial distribution of infestations and natural parasitism using semivariograms. Landscape metrics of each coffee plantation were surveyed in buffers ranging from 500 to 3000 m to assess their effects on population aggregation. Infestations of L. coffeella and natural parasitism of the pest occurred throughout the year and at varying intensities among farms. Leucoptera coffeella infestation and natural parasitism exhibited moderate aggregation patterns in most sampling months. The aggregation of L. coffeella infestations and natural parasitism were influenced by landscape and insecticide use. Forest cover, land cover use diversity, and insecticide use increased aggregation of L. coffeella infestations and natural parasitism, whereas edge density decreased aggregation of both. The study suggests that it may be beneficial to review the current sampling plans for the coffee leaf miner and the natural parasitism in coffee farms. This information can improve the integrated management of the pest in coffee farms and assist in decision-making regarding L. coffeella control strategies.

Secondary Nucleation of Aβ Revealed by Single-Molecule and Computational Approaches.

Understanding the mechanisms underlying amyloid-β (Aβ) aggregation is pivotal in the context of Alzheimer's disease. This study aims to elucidate the secondary nucleation process of Aβ42 peptides by combining experimental and computational methods. Using a newly developed nanopipette-based amyloid seeding and translocation assay, confocal fluorescence spectroscopy, and molecular dynamics simulations, the influence of the seed properties on Aβ aggregation is investigated. Both fragmented and unfragmented seeds played distinct roles in the formation of oligomers, with fragmented seeds facilitating the formation of larger aggregates early in the incubation phase. The results show that secondary nucleation leads to the formation of oligomers of various sizes and structures as well as larger fibrils structured in β-sheets. From these findings a mechanism of secondary nucleation involving two types of aggregate populations, one released and one growing on the mother fiber is proposed.

Multi-Scale Dynamics and Spatial Consistency of Economy and Population Based on NPP/VIIRS Nighttime Light Data and Population Imagery: A Case Study of the Yangtze River Delta

Population and economy are crucial factors contributing to regional disparities. Studying the patterns and relationships between these two elements is essential for promoting sustainable development in regions and cities. This study constructs multi-scale geographic concentration indices and inconsistency indices, utilizing NPP/VIIRS and LandScan data to quantitatively analyze the spatial pattern changes of population and economy in the Yangtze River Delta across various spatial scales, revealing the matching relationships between population and economic elements within cities. The results indicate that the economy in the Yangtze River Delta is spreading outward from the core areas, with the average population–nightlight inconsistency index decreasing from 1.57 to 1.33. This suggests that the imbalance between population and economy within the urban agglomeration is gradually improving, consistent with trends observed in statistical survey data. Within individual cities, there is a noticeable spatial mismatch between population and nightlight intensity, with the population primarily concentrated in urban core areas. As urban spaces expand, the areas where population concentration is significantly lower than nightlight concentration are gradually diminishing. By 2022, the land area where population and economic concentration are coordinated within the Yangtze River Delta urban areas increased from 9.13% to 16.24%. Population concentration in these coordinated regions rose from 11.33% to 16.33%, while nightlight concentration increased from 9.98% to 13.63%. The improved geographic concentration and inconsistency indices are effective indicators for multi-scale monitoring of population and economic spatial changes. The integration of NPP/VIIRS nighttime light data and LandScan data provides an effective method for uncovering different spatial patterns of population and socio-economic element aggregation in urban structures. This can offer insights for promoting sustainable regional and urban development.

The Ability of Different Tea Tree Germplasm Resources in South China to Aggregate Rhizosphere Soil Characteristic Fungi Affects Tea Quality.

It is generally recognized that the quality differences in plant germplasm resources are genetically determined, and that only a good "pedigree" can have good quality. Ecological memory of plants and rhizosphere soil fungi provides a new perspective to understand this phenomenon. Here, we selected 45 tea tree germplasm resources and analyzed the rhizosphere soil fungi, nutrient content and tea quality. We found that the ecological memory of tea trees for soil fungi led to the recruitment and aggregation of dominant fungal populations that were similar across tea tree varieties, differing only in the number of fungi. We performed continuous simulation and validation to identify four characteristic fungal genera that determined the quality differences. Further analysis showed that the greater the recruitment and aggregation of Saitozyma and Archaeorhizomyces by tea trees, the greater the rejection of Chaetomium and Trechispora, the higher the available nutrient content in the soil and the better the tea quality. In summary, our study presents a new perspective, showing that ecological memory between tea trees and rhizosphere soil fungi leads to differences in plants' ability to recruit and aggregate characteristic fungi, which is one of the most important determinants of tea quality. The artificial inoculation of rhizosphere fungi may reconstruct the ecological memory of tea trees and substantially improve their quality.

The association between visceral adiposity index and risk of type 2 diabetes mellitus

Relationships between the visceral adiposity index (VAI) and type 2 diabetes mellitus (T2DM) have been underexplored. The purpose of this study is to explore association between VAI and T2DM in adults in the US. Based on the National Health and Nutrition Examination Survey 2007–2018, 11,214 participants aged 20 years or older were included in a cross-sectional study. Multifactorial logistic regression analysis and smoothed curve fitting analysis were performed to investigate links between VAI and the prevalence of T2DM, as well as the stability and incidence between subgroups. In a fully adjusted continuous model, the aggregate population risk of T2DM increased 0.43-fold with each 1-unit increase in VAI [odds ratio (OR) = 1.43; 95% confidence interval (CI) 1.35–1.50]. In the fully adjusted categorical model with VAI scores stratified by quartiles, results showed a higher T2DM advantage among participants in the second, third, and fourth quartiles (Q2: OR 1.35, 95% CI 1.06–1.71; Q3: OR 2.46, 95% CI 1.95–3.11; Q4: OR 4.42, 95% CI 3.55–05.50). Compared with Q1, the prevalence of T2DM in the total population increased 3.42-fold in Q4. The above results indicated that VAI was positively associated with the prevalence of T2DM, which was consistent and nonlinear with the smoothed curve-fitting analysis (P for non-linear = 0). Subgroup analyses after adjusting for covariates showed that keeping with the overall population results, it also was found that there was an interaction between sex and hypertension in the subgroups. VAI was positively associated with the prevalence of T2DM and was more prevalent in women, non-hypertensive than in men, hypertensive populations.

Marital status and long-term cardiovascular risk in general population-RIFLE project (Italy).

The impact of marital status on cardiovascular disease (CVD) remains controversial in the general population. The present investigation sought to delineate the association between marital status and long-term major non-fatal and fatal CVD, along with all-cause mortality within the scope of the RIFLE project (Risk Factors and Life Expectancy). We examined the incidences of CVD, including cerebrovascular accidents and coronary heart disease (CHD), as well as all-cause mortality. In total, 47,167 individuals (46% female, average age 50 ± 9 years) were included in the analysis. Marital status at inception was categorized into married (inclusive of married or cohabitating) versus unmarried cohorts (including widowed, separated, divorced, or single individuals). Compared to their married counterparts, unmarried subjects demonstrated a heightened risk for CVD in both females and males. Throughout a median follow-up span of 7.4 years (interquartile range from 6 to 9 years), married participants, adjusting for standard risk factors, exhibited reduced mortality rates attributed to CHD [hazard ratio (HR) 0.54 (95% confidence interval (CI) 0.33-0.86)) and all causes (HR 0.75 (95% CI 0.62-0.91)] within the aggregate population; this reduction persisted for both CHD-specific [HR 0.39 (95% CI 0.51-0.90)]and all-cause mortality [HR 0.68 (95% CI 0.51-0.90)], independent of traditional risk factors in women. No associations were evident between matrimonial status and any measured outcomes in males. Within primary care settings, marital status should be considered a potential correlate of long-term CHD and overall mortality risks, especially among women.

Spatial Characteristics of Multidimensional Urban Vitality and Its Impact Mechanisms by the Built Environment

Urban vitality, intricately connected to urban morphology, has long been a cornerstone of urban planning and design. The accelerated pace of urbanization has created abundant living and working spaces, but it has also brought about a series of issues such as traffic congestion, environmental pollution, insufficient public spaces, and uneven urban development, leading to a decline in urban vitality. The spatial distribution patterns of urban vitality and their influencing factors are diverse and vary across different cities, necessitating a multidimensional exploration of the relationship between urban vitality and the built environment. Utilizing the central urban area of Beijing as a case study, this research leverages multi-source urban spatial data to delineate the spatial characteristics of social, economic, cultural, and comprehensive vitality. Furthermore, a comprehensive set of built-environment indicators is developed across five dimensions to analyze their correlation with urban vitality. The results indicate: (1) There is a significant spatial clustering of various vitality types in Beijing, with a pronounced correlation between high-density population aggregation and vigorous economic activities. (2) Subdistricts exhibiting high social vitality display an “n”-shaped distribution around the Second Ring Road. In contrast, those with high economic vitality are concentrated along Chang’an Street and various district commercial centers. High cultural vitality subdistricts are distributed in a northwest–southeast trajectory from the Fourth Ring Road to the Second Ring Road, and subdistricts with high comprehensive vitality exhibit a concentric distribution radiating outwards from the center. (3) Social vitality is most closely related to comprehensive vitality, and the various vitality types in Beijing’s central urban area develop relatively evenly. (4) The built environment significantly affects all types of urban vitality. Factors such as floor area ratio, POI density, POI mixing degree, and intersection density are fundamental to enhancing urban vitality, whereas the greening rate somewhat inhibits it. (5) Future spatial planning should utilize the radiating effect of high-vitality subdistricts to optimize population distribution, enhance POI mixing, increase metro station density, and strengthen critical urban structures for synergistic economic and cultural development. This study provides a foundation and promotion strategies for optimizing the layout and enhancing vitality at the subdistrict scale within Beijing’s central urban area.

The individual Laffer curve: evidence from the Spanish income tax

AbstractThis paper characterises the Laffer curve of each individual taxpayer in a schedular multi-rate income tax with income shifting. Analytical expressions for the revenue-maximising tax rate and the revenue-maximising elasticity are provided for the individual taxpayer and the aggregate population, as well as new estimates of the Elasticity of Taxable Income. Applying these to the Spanish income tax demonstrates that 44.72% (58.49%) of the taxpaying population in the non-savings tax base (savings tax base) is on the “normal” side of the Laffer curve. On average, these taxpayers are 6.59 points (24.73 points) above (below) the maximum of the Laffer curve. The fraction of total tax revenue lost through behavioural responses amounts to 53.77%. However, this fraction varies by population subgroup and decreases when we account for income-shifting responses, suggesting the presence of fiscal externalities in the Spanish PIT.

Regional disparities and social-ecological constraints of soil antibiotic pollution in urban agglomerations of China

With intensive socio-economic growth, antibiotics have been heavily discharged into soils, posing a threat to ecosystems and human health. However, limited data are available in broad-scale urban agglomerations which limit the understanding of the driving mechanisms for antibiotic pollution and hinder action plans for pollution control. Here, we examined the underlying mechanisms driving antibiotic pollution and their regional disparities (Central Yunnan vs. Yangtze River Delta), and we predicted antibiotic concentrations in the soils of these two urban agglomerations using machine learning algorithms. Specifically, anthropogenic pressures such as population aggregation and livestock production accounted for the highest contribution to model accuracy in Central Yunnan, suggesting human interference mediated by geographical isolation likely plays a pivotal role in the clustering of antibiotic pollution in soils. However, soil and climate variables were the most important predictors in the more developed Yangtze River Delta, indicating that human-mediated soil carrying capacity was likely the main mechanism controlling antibiotic pollution in this region. Our results showed that machine learning models performed better (area under the receiver operating characteristics curve: 0.91–0.98) in predicting antibiotic hotspots than classic linear models. Our findings highlight the regional disparities in underlying mechanisms for antibiotic pollution in the soils of urban agglomerations, and demonstrate that machine learning algorithms based on spatially available predictors can be extended to other regions.

An evolutionary case for plant rarity: Eucalyptus as a model system

AbstractSpecies rarity is a common phenomenon across global ecosystems that is becoming increasingly more common under climate change. Although species rarity is often considered to be a stochastic response to environmental and ecological constraints, we examined the hypothesis that plant rarity is a consequence of natural selection acting on performance traits that affect a species range size, habitat specificity, and population aggregation; three primary descriptors of rarity. Using a common garden of 25 species of Tasmanian Eucalyptus, we find that the rarest species have 70% lower biomass than common species. Although rare species demonstrate lower biomass, rare species allocated proportionally more biomass aboveground than common species. There is also a negative phylogenetic autocorrelation underlying the biomass of rare and common species, indicating that traits associated with rarity have diverged within subgenera as a result of environmental factors to reach different associated optima. In support of our hypothesis, we found significant positive relationships between species biomass, range size and habitat specificity, but not population aggregation. These results demonstrate repeated convergent evolution of the trait‐based determinants of rarity across the phylogeny in Tasmanian eucalypts. Furthermore, the phylogenetically driven patterns in biomass and biomass allocation seen in rare species may be representative of a larger plant strategy, not yet considered, but offering a mechanism as to how rare species continue to persist despite inherent constraints of small, specialized ranges and populations. These results suggest that if rarity can evolve and is related to plant traits such as biomass, rather than a random outcome of environmental constraints, we may need to revise conservation efforts in these and other rare species to reconsider the abiotic and biotic factors that underlie the distributions of rare plant species.

The Delineation and Characterisation of Chinese Urbanised Areas Using Micro-Scale Population Census Data

The definition of cities from the physical view in China is lacking. Most research regarding Chinese cities relies on the definition from the administrative view, which is often inconsistent as there are serious discrepancies between the administrative boundaries and the physical extent of Chinese cities. This study aims to delineate Chinese urbanised areas using population census data at the township level and analyse the identified urbanised areas’ characteristics. The results show that the numbers of Chinese urbanised areas in 2000, 2010, and 2020 were 758, 942, and 1058, respectively, indicating there are several ‘cities outside the system’ that meet the requirements of urban agglomeration but are constrained by the city designation system. The degree of population aggregation and the growth rate of urbanised areas are greater than those of administrative cities. This indicates that the geographical scopes of administrative cities cannot accurately reflect the ‘real’ urban areas. Additionally, the city-size distribution follows Zipf’s law, with the Zipf coefficient moving closer to one if we fit the Zipf model based on the urbanised areas. It is necessary to establish official urbanised areas and publish statistical data based on urbanised areas, which could have significant implications both for policymakers and researchers.

Calibration Estimation of Population Total in Two-Stage Sampling Design under unavailability of Population Level Auxiliary Information for the selected PSUs

Calibration approach is a popular technique in sample surveys which incorporates auxiliary information in the estimation process assuming that population aggregates of auxiliary variable are available. Many often under two-stage sampling design, such population aggregates of auxiliary variable, i.e., population mean or total are unavailable and under such situations, estimation of population total has been limited to the use of two phase sampling. Therefore, in the present study, efficient estimator of population total is developed under two-stage sampling design when population aggregates of auxiliary variable are unavailable for the selected psu’s. The calibrated estimator is developed using the information on known population aggregates of additional auxiliary variable which is less linearly related to the study variable through two step calibration approach. The approximate variance and variance estimator of the proposed calibrated estimator has also been developed. Empirical evaluations using both real and simulated data shows the superior performance of the developed calibrated estimator in comparison to the existing estimators.

Vanishing giants: An assessment on the population status of giant clams across Malaysia

The iconic giant clams are known for its multifaceted importance throughout the Indo-Pacific –for functional, ecological, or cultural purposes. In Malaysia, habitat destruction and illegal poaching were main reasons behind the declining populations of giant clams. As previous surveys date back to 1990 s, an update on the status of giant clam populations in Malaysia is overdue. Using the extensive monitoring data from Reef Check Malaysia, we analysed and provided an assessment of population trends of giant clams between 2007 and 2021 in Malaysia. This study showed a decline in giant clam population in the east coast Peninsula and Sabah, while their abundances have always been low in the west coast Peninsula and Sarawak. In the east coast Peninsula, Tridacna maxima and T. crocea were most common (2.7 ± 7.3 and 1.4 ± 7.6 clams per 100 m2, respectively), followed by T. squamosa (0.7 ± 1.4 clams per 100 m2), and Hippopus hippopus (0.3 ± 2.5 clams per 100 m2). The boring species, T. maxima and T. crocea, typically displayed highly aggregated populations, reaching densities of 41.5 and 70 clams per 100 m2, where a reciprocal abundance shift between both species was observed between northern and southern sites of east coast Peninsula. The demography of T. maxima and T. crocea is either positively skewed or normally distributed, indicating abundant recruits that correspond to their higher densities. In contrast, T. squamosa showed a negative skew, suggesting poor recruitment rates. Findings here underscore the need to tailor conservation strategies for respective giant clam species in Malaysia. Proposed initiatives include establishing conservation zones in key areas like Perhentian, Lang Tengah, Redang, and Tioman Islands, which have significant T. maxima and T. crocea recruit populations. Also, targeted restocking efforts are necessary for T. squamosa and H. hippopus to ensure long-term viability of populations.

Spatio–Temporal Dynamic Characteristics and Driving Mechanisms of Urban Compactness in Central China

As a result of rapid urbanization in China, the spatial restructuring of towns and cities has significantly impacted urban compactness. The study of the spatio–temporal characteristics and driving mechanisms of urban compactness in central China is a strategic imperative and conducive to promoting regional sustainable development that is based on easing the contradiction between land resource supply and demand and reducing energy consumption. Therefore, this study focused on 80 prefecture-level cities in central China, utilizing barycenter model and GTWR model, among others, to analyze the spatio–temporal evolution pattern of urban compactness from 2006 to 2020 and its driving factors, with the aim of uncovering the intrinsic mechanisms behind enhancing urban compactness in the area. The results show the follows: (1) The urban compactness in central China has generally shown an upward trend, with a pronounced spatial clustering around provincial capital cities and the spatial changes in compactness predominantly concentrated in the north–south direction. (2) Various factors have influenced urban compactness, where government intervention and population aggregation present as bi-directional driving factors, while the effective use of land resources and high-quality industrial development, among others, present as positive driving factors. The spatio–temporal heterogeneity and agglomeration features of each driving factor are significant. (3) Further analysis indicates that the effective use of land resources is the primary factor in enhancing urban compactness, followed by technology. Therefore, we should adhere to the concept of compact cities and gradually promote the compactness of cities in central China based on the impact of the driving factors.