scholarly journals Population Dynamics and Agglomeration Factors: A Non-Linear Threshold Estimation of Density Effects

2020 ◽  
Vol 12 (6) ◽  
pp. 2257 ◽  
Author(s):  
Mariateresa Ciommi ◽  
Gianluca Egidi ◽  
Rosanna Salvia ◽  
Sirio Cividino ◽  
Kostas Rontos ◽  
...  
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Population Distribution ◽  
Negative Impact ◽  
Population Decline ◽  
Temporal Analysis ◽  
Time Interval ◽  
Density Dependent ◽  
Urban Dynamics ◽  
Population Growth Rates

Although Southern Europe is relatively homogeneous in terms of settlement characteristics and urban dynamics, spatial heterogeneity in its population distribution is still high, and differences across regions outline specific demographic patterns that require in-depth investigation. In such contexts, density-dependent mechanisms of population growth are a key factor regulating socio-demographic dynamics at various spatial levels. Results of a spatio-temporal analysis of the distribution of the resident population in Greece contributes to identifying latent (density-dependent) processes of metropolitan growth over a sufficiently long time interval (1961-2011). Identification of density-dependent patterns of population growth contributes to the analysis of socioeconomic factors underlying demographic divides, possibly distinguishing between the effects of population concentration and dispersion. Population growth rates were non-linearly correlated with population density, highlighting a positive (or negative) impact of urban concentration on demographic growth when population is lower (or higher) than a fixed threshold (2800 and 1300 inhabitants/km2 in 1961 and 2011, respectively). In a context of low population density (less than 20 inhabitants/km2), the relationship between density and growth was again negative, contrasting with the positive and linear relationship observed in denser contexts. This result evidences a sort of ‘depopulation’ trap that leads to accelerated population decline under a defined density threshold. An improved understanding of density-dependent mechanisms of population growth and decline contributes to rethinking strategies of sustainable development and social policies more adapted to heterogeneous regional contexts.

Testing the potential for supplementary water to support the recovery and reintroduction of the black-footed rock-wallaby

2017 ◽  
Vol 44 (3) ◽  
pp. 269 ◽  
Author(s):  
Rebecca West ◽  
Matthew J. Ward ◽  
Wendy K. Foster ◽  
David A. Taggart
Keyword(s):  
Population Growth ◽  
Threatened Species ◽  
Population Decline ◽  
South Australia ◽  
Camera Traps ◽  
Limiting Factor ◽  
Population Growth Rates ◽  
Introduced Predators ◽  
Predation Effects

Context Supplementary resource provision is increasingly used by conservation managers to manipulate habitat conditions that limit population growth of threatened species. These methods are popular in reintroduction programs because they can assist released individuals to adapt to novel environments. In situ management and reintroductions are being used to recover warru (black-footed rock-wallaby, Petrogale lateralis MacDonnell Ranges race) on the arid Anangu Pitjantjatjara Yankunytjatjara (APY) Lands of South Australia. Direct predation by introduced predators is thought to be the main cause of population decline, but indirect predation effects reducing access to water resources has also been proposed as a limiting factor. Aims To determine whether warru would use supplementary water and so provide a tool to alleviate resource pressure for in situ (wild) and reintroduced warru populations. Methods We provided supplementary water to a wild and reintroduced warru population across 12 months. Drinking rates were calculated by monitoring water points with camera traps and modelled against plant moisture content and total rainfall. We also examined whether number of visits to water points by warru predators and competitors was significantly different to control points (no water present). Key results Wild and reintroduced warru used water points within 0–10 days of installation. No significant increase in visits by predators or competitors was observed at water points. Drinking rates were significantly higher during dry winter months (March–October) for both wild and re-introduced populations. Conclusions Supplementary water is readily utilised by warru. Water could be provided in this manner to warru populations where predators are present, particularly during drier months (generally March–October on the APY Lands), periods of drought or after fire, when food resources will have a lower water content and/or be less abundant. This may increase breeding rates and recruitment of young, and improve the probability of persistence for populations of this threatened species, and should be further investigated. Implications Supplementary water provision may be a useful tool to increase population growth rates for threatened mammalian herbivores in arid habitats. Experimental trials of the uptake of supplementary water and effects on population dynamics will provide important data for implementing adaptive management frameworks for conservation.

Density-Dependent Population Growth

2020 ◽  
pp. 29-46
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Density Dependence ◽  
Multiple Equilibria ◽  
Dynamical Behavior ◽  
Logistic Growth ◽  
Density Dependent ◽  
Per Capita ◽  
Discrete Time Models ◽  
Complex Dynamical Behavior

The observation that no population can grow indefinitely and that most populations persist on ecological timescales implies that mechanisms of population regulation exist. Feedback mechanisms include competition for limited resources, cannibalism, and predation rates that vary with density. Density dependence occurs when per capita birth or death rates depend on population density. Density dependence is compensatory when the population growth rate decreases with population density and depensatory when it increases. The logistic model incorporates density dependence as a simple linear function. A population exhibiting logistic growth will reach a stable population size. Non-linear density-dependent terms can give rise to multiple equilibria. With discrete time models or time delays in density-dependent regulation, the approach to equilibrium may not be smooth—complex dynamical behavior is possible. Density-dependent feedback processes can compensate, up to a point, for natural and anthropogenic disturbances; beyond this point a population will collapse.

Using population dynamics modelling to evaluate potential success of restoration: a case study of a Hawaiian vine in a changing climate

2014 ◽  
Vol 42 (1) ◽  
pp. 20-30 ◽  
Author(s):  
TAMARA M. WONG ◽  
TAMARA TICKTIN
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Key Management ◽  
Demographic Data ◽  
Population Decline ◽  
Management Strategies ◽  
Survival Rates ◽  
Population Modelling ◽  
Population Growth Rates

SUMMARYDemographic comparisons between wild and restored populations of at-risk plant species can reveal key management strategies for effective conservation, but few such studies exist. This paper evaluates the potential restoration success ofAlyxia stellata, a Hawaiian vine. Stage-structured matrix projection models that compared long-term and transient dynamics of wild versus restoredA. stellatapopulations, and restored populations under different levels of canopy cover, were built from demographic data collected over a four year period. Stochastic models of wild populations projected stable or slightly declining long-term growth rates depending on frequency of dry years. Projected long-term population growth rates of restored populations were significantly higher in closed than open canopy conditions, but indicated population decline under both conditions. Life table response experiments illustrated that lower survival rates, especially of small adults and juveniles, contributed to diminished population growth rates in restored populations. Transient analyses for restored populations projected short-term decline occurring even faster than predicted by asymptotic dynamics. Restored populations will not be viable over the long term under conditions commonly found in restoration projects and interventions will likely be necessary. This study illustrates how the combination of long-term population modelling and transient analyses can be effective in providing relevant information for plant demographers and restoration practitioners to promote self-sustaining native populations, including under future climates.

Trapping as a means of controlling tsetse, Glossina spp. (Diptera: Glossinidae): the relative merits of killing and of sterilization

1986 ◽  
Vol 76 (1) ◽  
pp. 89-95 ◽  
Author(s):  
P. A. Langley ◽  
D. Weidhaas
Keyword(s):  
Population Growth ◽  
Population Growth Rate ◽  
Population Decline ◽  
Cost Effective ◽  
Life Stages ◽  
Age Classes ◽  
Tsetse Control ◽  
Population Growth Rates ◽  
History Analysis ◽  
Population Numbers

AbstractA deterministic simulation model for Glossina spp. based upon a simple life-history analysis was used to test a variety of effects designed to cause a decline in population numbers. Average daily survival values for pupae were varied to make populations grow at different rates. All age classes were then updated for all life stages each day for a 12-month period. As expected, the population remained stable when Ro = 1·0, and the population doubled in 105 days when Ro = 2·0. Sub-routines were added to test the effects of trapping 0·5 to 2·5% of the population per day and killing both sexes, sterilizing and releasing both sexes or sterilizing and releasing males only, the females not being trapped. Results suggest that killing or sterilizing both sexes is always superior to sterilizing males only and leaving the females unharmed but that this superiority is diminished when either population growth rates are low (<1·0) or trapping rates are high (>2·0% per day). As population growth rate increases or trapping rates decline, there is a proportionately greater advantage to be gained by sterilizing both sexes than by adopting either of the other two strategies. A situation is illustrated where for a trapping rate of 1% per day within a population that is doubling at close to its optimal rate (Ro = 2·0) sterilization of both sexes is the only strategy which will cause a population decline. Results are discussed in terms of development of low technology, cost-effective methods of tsetse control which are non-polluting and therefore environmentally acceptable.

scholarly journals An Improved Global Analysis of Population Distribution in Proximity to Active Volcanoes, 1975–2015

2019 ◽  
Vol 8 (8) ◽  
pp. 341 ◽  
Author(s):  
Sergio Freire ◽  
Aneta Florczyk ◽  
Martino Pesaresi ◽  
Richard Sliuzas
Keyword(s):  
Population Growth ◽  
Southeast Asia ◽  
Central America ◽  
Population Distribution ◽  
Global Analysis ◽  
Population Growth Rates ◽  
Worldwide Distribution ◽  
Close Proximity ◽  
Global Population ◽  
Recent Volcanism

Better and more detailed analyses of global human exposure to hazards and associated disaster risk require improved geoinformation on population distribution and densities. In particular, issues of temporal and spatial resolution are important for determining the capacity for assessing changes in these distributions. We combine the best-available global population grids with latest data on volcanoes, to assess and characterize the worldwide distribution of population from 1975–2015 in relation to recent volcanism. Both Holocene volcanoes and those where there is evidence of significant eruptions are considered. A comparative analysis is conducted for the volcanic hot spots of Southeast Asia and Central America. Results indicate that more than 8% of the world’s 2015 population lived within 100 km of a volcano with at least one significant eruption, and more than 1 billion people (14.3%) lived within 100 km of a Holocene volcano, with human concentrations in this zone increasing since 1975 above the global population growth rate. While overall spatial patterns of population density have been relatively stable in time, their variation with distance is not monotonic, with a higher concentration of people between 10 and 20 km from volcanoes. We find that in last 40 years in Southeast Asia the highest population growth rates have occurred in close proximity to volcanoes (within 10 km), whereas in Central America these are observed farther away (beyond 50 km), especially after 1990 and for Holocene volcanoes.

scholarly journals Monitoring of Urban Sprawl and Densification Processes in Western Germany in the Light of SDG Indicator 11.3.1 Based on an Automated Retrospective Classification Approach

2021 ◽  
Vol 13 (9) ◽  
pp. 1694
Author(s):  
Gohar Ghazaryan ◽  
Andreas Rienow ◽  
Carsten Oldenburg ◽  
Frank Thonfeld ◽  
Birte Trampnau ◽  
...  
Keyword(s):  
Population Growth ◽  
Urban Areas ◽  
Urban Expansion ◽  
Population Data ◽  
Observation Data ◽  
Time Step ◽  
Urban Dynamics ◽  
Random Forest Classification ◽  
Population Growth Rates ◽  
High Level

By 2050, two-third of the world’s population will live in cities. In this study, we develop a framework for analyzing urban growth-related imperviousness in North Rhine-Westphalia (NRW) from the 1980s to date using Landsat data. For the baseline 2017-time step, official geodata was extracted to generate labelled data for ten classes, including three classes representing low, middle, and high level of imperviousness. We used the output of the 2017 classification and information based on radiometric bi-temporal change detection for retrospective classification. Besides spectral bands, we calculated several indices and various temporal composites, which were used as an input for Random Forest classification. The results provide information on three imperviousness classes with accuracies exceeding 75%. According to our results, the imperviousness areas grew continuously from 1985 to 2017, with a high imperviousness area growth of more than 167,000 ha, comprising around 30% increase. The information on the expansion of urban areas was integrated with population dynamics data to estimate the progress towards SDG 11. With the intensity analysis and the integration of population data, the spatial heterogeneity of urban expansion and population growth was analysed, showing that the urban expansion rates considerably excelled population growth rates in some regions in NRW. The study highlights the applicability of earth observation data for accurately quantifying spatio-temporal urban dynamics for sustainable urbanization and targeted planning.

scholarly journals Projecting the future of Canada's population: assumptions, implications, and policy

2003 ◽  
Vol 30 (1) ◽  
pp. 1 ◽  
Author(s):  
Roderic Beaujot
Keyword(s):  
Population Growth ◽  
Gender Equity ◽  
International Migration ◽  
Population Distribution ◽  
Labour Force ◽  
Population Decline ◽  
Age Groups ◽  
Relative Size ◽  
Natural Increase ◽  
The Future

After considering the assumptions for fertility, mortality and international migration, this paper looks at implications of the evolving demographics for population growth, labour force, retirement, and population distribution. With the help of policies favouring gender equity and supporting families of various types, fertility in Canada could avoid the particularly low levels seen in some countries, and remain at levels closer to 1.6 births per woman. The prognosis in terms of both risk factors and treatment suggests further reductions in mortality toward a life expectancy of 85. On immigration, there are political interests for levels as high as 270,000 per year, while levels of 150,000 correspond to the long term post-war average. The future will see slower population growth, and due to migration more than natural increase. International migration of some 225,000 per year can enable Canada to avoid population decline, and sustain the size of the labour force, but all scenarios show much change in the relative size of the retired compared to the labour force population. According to the ratio of persons aged 20-64 to that aged 65 and over, there were seven persons at labour force ages per person at retirement age in 1951, compared to five in 2001 and probably less than 2.5 in 2051. Growth that is due to migration more so than natural increase will accentuate the urbanization trend and the unevenness of the population distribution over space. Past projections have under-projected the mortality improvements and their impact on the relative size of the population at older age groups. Policies regarding fertility, mortality and migration could be aimed at avoiding population decline and reducing the effect of aging, but there is lack of an institutional basis for policy that would seek to endogenize population.

scholarly journals Density-dependent selection and the limits of relative fitness

2017 ◽  
Author(s):  
Jason Bertram ◽  
Joanna Masel
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Competitive Ability ◽  
Relative Fitness ◽  
Density Dependent ◽  
Volterra Models ◽  
Selection Behavior ◽  
Novel Model ◽  
Stable Populations ◽  
Density Dependent Selection

AbstractSelection is commonly described by assigning constant relative fitness values to genotypes. Yet population density is often regulated by crowding. Relative fitness may then depend on density, and selection can change density when it acts on a density-regulating trait. When strong density-dependent selection acts on a density-regulating trait, selection is no longer describable by density-independent relative fitnesses, even in demographically stable populations. These conditions are met in most previous models of density-dependent selection (e.g. “K-selection” in the logistic and Lotka-Volterra models), suggesting that density-independent relative fitnesses must be replaced with more ecologically explicit absolute fit-nesses unless selection is weak. Here we show that density-independent relative fitnesses can also accurately describe strong density-dependent selection under some conditions. We develop a novel model of density-regulated population growth with three ecologically intuitive traits: fecundity, mortality, and competitive ability. Our model, unlike the logistic or Lotka-Volterra, incorporates a density-dependent juvenile “reproductive excess”, which largely decouples density-dependent selection from the regulation of density. We find that density-independent relative fitnesses accurately describe strong selection acting on any one trait, even fecundity, which is both density-regulating and subject to density-dependent selection. Pleiotropic interactions between these traits recovers the familiarK-selection behavior. In such cases, or when the population is maintained far from demographic equilibrium, our model offers a possible alternative to relative fitness.

scholarly journals Changing Patterns of Population Density in the Jammu and Kashmir

2020 ◽  
Vol 7 (4) ◽  
pp. 315-321
Author(s):  
Javaid Ahmad Andrabi
Keyword(s):  
Population Density ◽  
Human Resources ◽  
Population Growth ◽  
Population Distribution ◽  
Temporal Variations ◽  
Economic Activities ◽  
Jammu And Kashmir ◽  
Changing Patterns ◽  
Special Approach ◽  
Density Pattern

The population growth and distribution has attracted increasing attention from geographers and planners in India from two or three decades to make the special approach in them to solve the human problems, which is a great task to handle. Here an attempt has been made on demographic dimensions of human resources to examine spatial and temporal variations in population growth and density during the last four decades (1981-2011). Density of population in the state is 124 persons per km2 (Census 2011). The study indicates that Srinagar and Jammu districts recorded high density of population of 2860 and 674 persons per km2 respectively, mainly on account of being the state’s administrative capitals which have made them the hub of socio-economic activities. The lowest population density is found in the Ladakh division with only 3 persons per km2 in Leh district. The population distribution and density pattern indicates an overwhelming influence of geo-physical disposition across the different regions of the Jammu and Kashmir state.

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