Populations

2021 ◽  
pp. 25-69
Author(s):  
Vaclav Smil
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Demographic Transition ◽  
Fossil Fuels ◽  
High Growth ◽  
Replacement Level ◽  
The 1960S ◽  
Productivity Gains

Demographic transition has been completed everywhere except for large parts of Africa. Steady decline of traditionally high fertilities and mortalities brought temporarily high rates of population growth (globally peaking during the 1960s), as the worldwide count rose from about 1 billion in 1800 to more than 7.8 billion by 2020. The new prevailing pattern of population dynamics is characterized by very low infant mortalities, fertilities well below the replacement level, increasing longevities, and aging, even decline, of many populations. Generations of high growth rates and productivity gains in agriculture and abundance of fossil fuels led to an unprecedented pace of urbanization. More than half of humanity now lives in cities, including a rising number of megacities, each with more than 10 million people.

Life history and environmental influences on population dynamics in sockeye salmon

2014 ◽  
Vol 71 (8) ◽  
pp. 1198-1208 ◽  
Author(s):  
Douglas C. Braun ◽  
John D. Reynolds
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Environmental Conditions ◽  
Sockeye Salmon ◽  
Life History Traits ◽  
Relative Importance ◽  
Population Growth Rates ◽  
Habitat Variables

Understanding linkages among life history traits, the environment, and population dynamics is a central goal in ecology. We compared 15 populations of sockeye salmon (Oncorhynchus nerka) to test general hypotheses for the relative importance of life history traits and environmental conditions in explaining variation in population dynamics. We used life history traits and habitat variables as covariates in mixed-effect Ricker models to evaluate the support for correlates of maximum population growth rates, density dependence, and variability in dynamics among populations. We found dramatic differences in the dynamics of populations that spawn in a small geographical area. These differences among populations were related to variation in habitats but not life history traits. Populations that spawned in deep water had higher and less variable population growth rates, and populations inhabiting streams with larger gravels experienced stronger negative density dependence. These results demonstrate, in these populations, the relative importance of environmental conditions and life histories in explaining population dynamics, which is rarely possible for multiple populations of the same species. Furthermore, they suggest that local habitat variables are important for the assessment of population status, especially when multiple populations with different dynamics are managed as aggregates.

scholarly journals Weather influences M. arvalis reproduction but not population dynamics in a 17-year time series

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Patrick Giraudoux ◽  
Petra Villette ◽  
Jean-Pierre Quéré ◽  
Jean-Pierre Damange ◽  
Pierre Delattre
Keyword(s):  
Time Series ◽  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Demographic Data ◽  
Common Vole ◽  
Empirical Work ◽  
Weather Conditions ◽  
Female Reproduction ◽  
Population Growth Rates

Abstract Rodent outbreaks have plagued European agriculture for centuries, but continue to elude comprehensive explanation. Modelling and empirical work in some cyclic rodent systems suggests that changes in reproductive parameters are partly responsible for observed population dynamics. Using a 17-year time series of Microtus arvalis population abundance and demographic data, we explored the relationship between meteorological conditions (temperature and rainfall), female reproductive activity, and population growth rates in a non-cyclic population of this grassland vole species. We found strong but complex relationships between female reproduction and climate variables, with spring female reproduction depressed after cold winters. Population growth rates were, however, uncorrelated with either weather conditions (current and up to three months prior) or with female reproduction (number of foetuses per female and/or proportion of females reproductively active in the population). These results, coupled with age-structure data, suggest that mortality, via predation, disease, or a combination of the two, are responsible for the large multi-annual but non-cyclic population dynamics observed in this population of the common vole.

scholarly journals Evolutionary effects of density-dependent selection in plants

1993 ◽  
Vol 62 (1) ◽  
pp. 57-62 ◽  
Author(s):  
G. Namkoong ◽  
J. Bishir ◽  
J. H. Roberds
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Energy Allocation ◽  
Gene Frequencies ◽  
Population Growth Rates ◽  
Stable Periodic ◽  
Density Dependent Selection ◽  
Allocation Strategies ◽  
Periodic Changes

SummaryThe evolution of traits that affect genotypic responses to density regulated resources can be strongly affected by population dynamics in ways that are unpredictable from individual viability or reproduction potentials. Genotypes that are most efficient in utilizing energy may not always displace less efficient ones, and the evolution of energy allocation strategies may not always favour reproductive fitness because of their effects on destabilizing population growth rates. Furthermore, genetic polymorphisms in single loci that affect such traits can be maintained in populations with stable, periodic changes in population size and gene frequencies in the absence of heterozygote superiority. In fact, in the models investigated in this paper, the polymorphism is maintained, even in the absence of equilibrium genotypic frequencies.

scholarly journals Population growth rates: issues and an application

2002 ◽  
Vol 357 (1425) ◽  
pp. 1307-1319 ◽  
Author(s):  
H. Charles J. Godfray ◽  
Mark Rees
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Population Growth Rate ◽  
Population Change ◽  
Evolutionarily Stable Strategy ◽  
Model Systems ◽  
Population Growth Rates

Current issues in population dynamics are discussed in the context of The Royal Society Discussion Meeting 'Population growth rate: determining factors and role in population regulation'. In particular, different views on the centrality of population growth rates to the study of population dynamics and the role of experiments and theory are explored. Major themes emerging include the role of modern statistical techniques in bringing together experimental and theoretical studies, the importance of long-term experimentation and the need for ecology to have model systems, and the value of population growth rate as a means of understanding and predicting population change. The last point is illustrated by the application of a recently introduced technique, integral projection modelling, to study the population growth rate of a monocarpic perennial plant, its elasticities to different life-history components and the evolution of an evolutionarily stable strategy size at flowering.

scholarly journals Pattern of variation in avian population growth rates

2002 ◽  
Vol 357 (1425) ◽  
pp. 1185-1195 ◽  
Author(s):  
Bernt–Erik Sæther ◽  
Steinar Engen
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Growth Rates ◽  
Specific Growth ◽  
Population Projections ◽  
Stochastic Effects ◽  
Density Regulation ◽  
Population Growth Rates ◽  
Specific Growth Rates

A central question in population ecology is to understand why population growth rates differ over time. Here, we describe how the long–term growth of populations is not only influenced by parameters affecting the expected dynamics, for example form of density dependence and specific population growth rate, but is also affected by environmental and demographic stochasticity. Using long–term studies of fluctuations of bird populations, we show an interaction between the stochastic and the deterministic components of the population dynamics: high specific growth rates at small densities r 1 are typically positively correlated with the environmental variance σ e 2 . Furthermore, θ, a single parameter describing the form of the density regulation in the theta–logistic density–regulation model, is negatively correlated with r 1 . These patterns are in turn correlated with interspecific differences in life–history characteristics. Higher specific growth rates, larger stochastic effects on the population dynamics and stronger density regulation at small densities are found in species with large clutch sizes or high adult mortality rates than in long–lived species. Unfortunately, large uncertainties in parameter estimates, as well as strong stochastic effects on the population dynamics, will often make even short–term population projections unreliable. We illustrate that the concept of population prediction interval can be useful in evaluating the consequences of these uncertainties in the population projections for the choice of management actions.

scholarly journals Revisiting the “City Life Cycle”: Global Urbanization and Implications for Regional Development

2020 ◽  
Vol 12 (3) ◽  
pp. 1151 ◽  
Author(s):  
Sirio Cividino ◽  
Rares Halbac-Cotoara-Zamfir ◽  
Luca Salvati
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Spatial Heterogeneity ◽  
Growth Rates ◽  
Regional Scale ◽  
Population Expansion ◽  
City Size ◽  
Low Fertility ◽  
Time Interval ◽  
Demographic Dynamics

A comparative, diachronic analysis of urban population dynamics allows for the identification of specific demographic trajectories influencing metropolitan expansion worldwide. However, a wide-ranging characterization of long-term population trends in metropolitan areas identifying sequential urban cycles with distinctive demographic dynamics is still incomplete. By hypothesizing a trade-off between ‘fast’ and ‘slow’ population dynamics that reflect ‘high’ and ‘low’ fertility regimes in both advanced and emerging economies, the present work investigates the relationship between city size (considering absolute population) and population growth rate in 1857 metropolitan agglomerations (>300,000 inhabitants in 2014) of 154 countries across the globe. Analysis covers a relatively long time period (1950–2030) and uses descriptive statistics (average and coefficient of variation) of the spatial series of population growth rates derived from United Nations demographics by metropolitan agglomeration and time interval. The results of our study indicate that metropolitan growth was associated with highly variable rates of population growth, being highly positive before 2000 and declining progressively in the subsequent decades. Despite important differences at the regional scale, an inverse relationship between population growth and city size was observed up to the late 1990s, with a higher spatial heterogeneity reflecting a moderate slowdown in demographic dynamics during recent years. Rapid population expansion dependent on city size and a higher spatial heterogeneity in growth rates insensitive to city size, evidence distinct metropolitan cycles reflecting worldwide transition from high to low fertility, ageing, and more unpredictable migration patterns.

scholarly journals Cohort fertility changes and period fertility in 1960-1990 in Finland

1995 ◽  
pp. 19-31
Author(s):  
Irma-Leena Notkola
Keyword(s):  
Total Fertility Rate ◽  
Demographic Transition ◽  
European Countries ◽  
Second Demographic Transition ◽  
Replacement Level ◽  
Calendar Time ◽  
Fertility Trends ◽  
Fertility Data ◽  
Cohort Fertility ◽  
The 1960S

In Finland, like in most European countries, the total fertility rate declined from a level of 2.5 births per woman in the middle of the 1960s below the replacement level of 2.1 births during the late sixties. This change has been called Europe’s second demographic transition. This paper aims to describe the changes in cohort fertility during and after this transition. The cohorts whose fertility is examined include the cohorts of women bom between 1923-24 and 1961-62. The cohort fertility data are from unpublished tables of Statistics Finland. Total fertility decreased from 2.6 births per woman in the cohort 1923-24 to the level of 1.8-1.9 births per woman in the cohorts 1943-44 and has stayed at this level in younger cohorts. The most prominent change in fertility behavior in recent years has been delaying births later in life. This transformation has been going on since the cohorts born in the middle of the 1940s. In calendar time this transformation started in the late sixties which suggests that the new contraception methods played an important role in it. Cohort fertility results are used in interpreting period fertility trends and variability in the last decades.

scholarly journals Age-structured Jolly-Seber model expands inference and improves parameter estimation from capture-recapture data

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0252748
Author(s):  
Nathan J. Hostetter ◽  
Nicholas J. Lunn ◽  
Evan S. Richardson ◽  
Eric V. Regehr ◽  
Sarah J. Converse
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Age Structure ◽  
Growth Rates ◽  
Lifetime Reproductive Success ◽  
Polar Bears ◽  
Population Growth Rates ◽  
Age Dependent ◽  
Capture Recapture ◽  
Age Structured

Understanding the influence of individual attributes on demographic processes is a key objective of wildlife population studies. Capture-recapture and age data are commonly collected to investigate hypotheses about survival, reproduction, and viability. We present a novel age-structured Jolly-Seber model that incorporates age and capture-recapture data to provide comprehensive information on population dynamics, including abundance, age-dependent survival, recruitment, age structure, and population growth rates. We applied our model to a multi-year capture-recapture study of polar bears (Ursus maritimus) in western Hudson Bay, Canada (2012–2018), where management and conservation require a detailed understanding of how polar bears respond to climate change and other factors. In simulation studies, the age-structured Jolly-Seber model improved precision of survival, recruitment, and annual abundance estimates relative to standard Jolly-Seber models that omit age information. Furthermore, incorporating age information improved precision of population growth rates, increased power to detect trends in abundance, and allowed direct estimation of age-dependent survival and changes in annual age structure. Our case study provided detailed evidence for senescence in polar bear survival. Median survival estimates were lower (<0.95) for individuals aged <5 years, remained high (>0.95) for individuals aged 7–22 years, and subsequently declined to near zero for individuals >30 years. We also detected cascading effects of large recruitment classes on population age structure, which created major shifts in age structure when these classes entered the population and then again when they reached prime breeding ages (10–15 years old). Overall, age-structured Jolly-Seber models provide a flexible means to investigate ecological and evolutionary processes that shape populations (e.g., via senescence, life expectancy, and lifetime reproductive success) while improving our ability to investigate population dynamics and forecast population changes from capture-recapture data.

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