Population Inertia Research Articles

Характеристики демографічної резильєнтності населення України у період пандемії Covid-19

The full-scale military invasion of Ukraine by the Russian Federation came at a time when our country had been weakened by a series of shocks in a relatively short historical period. Shocks such as a prolonged pandemic and war can disrupt and, in some cases, halt demographic development. In this context, the study of demographic resilience on the eve of a full-scale war, which became a new powerful shock for Ukraine, is relevant and necessary. The complexity of this issue does not allow us to provide all the answers in one article. The purpose of our paper is to determine the main parameters of the demographic resilience of the population of Ukraine in the Covid-19 period and to compare them with the characteristics of resilience in other periods of the greatest shocks experienced by our country, as well as with the indicators of other countries. In our study the main indicators of transient dynamics (convergence time, reactivity, population inertia, damping ratio) were calculated for the first time for the population of Ukraine. The influence of the contribution of different age groups of women to total fertility on the age structure of the population (with the same total fertility rate) was also determined for the first time. The calculations were based on the stable population model, the Leslie matrix, fertility tables, and life tables. The resilience indicators were calculated using the popdemo package. Methods of comparison, generalisation, and analogy were also used. Among the characteristics of demographic resilience, the half-life indicator stands out for its simplicity of calculation and interpretation. In Ukraine, the halving time for the population is decreasing, but it is still higher for the real population than for its stable equivalent. The age structure of the real population, formed under more favourable conditions, mitigates the negative consequences of shock periods, but the long-term preservation of the current regime of mortality and fertility will inevitably worsen the characteristics of the population. In Ukraine, advanced motherhood is an element of the adaptive cycle and requires a rethinking of its meaning and role, as it can be one of the internal mechanisms aimed at the resilience of the system in shock periods. In the conditions of the lowest-low fertility and mortality regime in Ukraine in 2021, advanced maternal age contributed to some increase in the number of births and a certain rejuvenation of the age structure of the population.

The impact of threshold decision mechanisms of collective behavior on disease spread

Humans are a hyper-social species, which greatly impacts the spread of infectious diseases. How do social dynamics impact epidemiology and what are the implications for public health policy? Here, we develop a model of disease transmission that incorporates social dynamics and a behavior that reduces the spread of disease, a voluntary nonpharmaceutical intervention (NPI). We use a "tipping-point" dynamic, previously used in the sociological literature, where individuals adopt a behavior given a sufficient prevalence of the behavior in the population. The thresholds at which individuals adopt the NPI behavior are modulated by the perceived risk of infection, i.e., the disease prevalence and transmission rate, costs to adopt the NPI behavior, and the behavior of others. Social conformity creates a type of "stickiness" whereby individuals are resistant to changing their behavior due to the population's inertia. In this model, we observe a nonmonotonicity in the attack rate as a function of various biological and social parameters such as the transmission rate, efficacy of the NPI, costs of the NPI, weight of social consequences of shirking the social norm, and the degree of heterogeneity in the population. We also observe that the attack rate can be highly sensitive to these parameters due to abrupt shifts in the collective behavior of the population. These results highlight the complex interplay between the dynamics of epidemics and norm-driven collective behaviors.

Spatiotemporal effects of Hurricane Ivan on an endemic epiphytic orchid: 10 years of follow-up

ABSTRACTBackground: Hurricanes have a strong influence on the ecological dynamics and structure of tropical forests. Orchid populations are especially vulnerable to these perturbations due to their canopy exposure and lack of underground storage organs and seed banks.Aims: We evaluated the effects of Hurricane Ivan on the population of the endemic epiphytic orchid Encyclia bocourtii to propose a management strategy.Methods: Using a pre- and post-hurricane dataset (2003–2013), we assessed the population asymptotic and transient dynamics. We also identified the individual size-stages that maximise population inertia and E. bocourtii’s spatial arrangement relative to phorophytes and other epiphytes.Results: Hurricane Ivan severely affected the survival and growth of individuals of E. bocourtii, and caused an immediate decline of the population growth rate from λ = 1.05 to λ = 0.32, which was buffered by a population reactivity of ρ1 = 1.42. Our stochastic model predicted an annual population decrease of 14%. We found an aggregated spatial pattern between E. bocourtii and its host trees, and a random pattern relative to other epiphytes.Conclusion: Our findings suggest that E. bocourtii is not safe from local extinction. We propose the propagation and reintroduction of reproductive specimens, the relocation of surviving individuals, and the establishment of new plantations of phorophytes.

Evaluation of Maternal Penning to Improve Calf Survival in the Chisana Caribou Herd

Evaluation of Maternal Penning to Improve Calf Survival in the Chisana Caribou Herd

Comparison of transient and asymptotic perturbation analyses of three epiphytic orchid species growing in coffee plantations in Mexico: effect on conservation decisions

ABSTRACTBackground: Epiphyte removal forms part of routine management in shade coffee plantations.Aims: Assess the current status of three population orchids growing in Mexican shaded coffee plantations and evaluate the effect of perturbing the transient behaviour of different life stages.Methods: We modelled the short-term response of eliminating I) non-reproductive juveniles, or II) reproductive adult plants from coffee bushes, on populations of Oncidium poikilostalix, Lepanthes acuminata and Telipogon helleri (Orchidaceae). First, we calculated the transient dynamics per se and second, we made a perturbation analysis on population inertia. Finally, we made a comparison with a traditional sensitivity analysis.Results: All three species showed different positive asymptotic growth rate: O. poikilostalix (λmax = 1.106), L. acuminata (λmax = 1.209), and T. helleri (λmax = 1.012). The effect of eliminating the major part of the juvenile or adult orchids gave population inertia in relation to steady state, respectively, (+19%, -24%) for O. poikilostalix, (+17%, -28%) for T. helleri and (+57%, -35%) for L. acuminata.Conclusions: Eliminating juveniles or adults affects in different ways the short-term dynamics due to differential impact on size stages that have the non-linear effects associated with important disturbances that currently affect orchids growing in coffee plantations.

Impact of hunting along the migration corridor of pink‐footed geeseAnser brachyrhynchus– implications for sustainable harvest management

SummaryHunting can potentially affect population size, age composition, sex‐ratio, behaviour and distribution of natural populations, and understanding its impacts is a prerequisite to manage quarry species sustainably. Harvest management relies strongly on the existence of both strictly regulated hunting efforts and efficient monitoring of populations, their demography and harvest. These conditions are rarely met in practice.For the Svalbard‐breeding population of the pink‐footed gooseAnser brachyrhynchus, an internationally coordinated adaptive harvest management framework enables a flyway‐based assessment of harvest impact. Based on 25 years of population assessment and harvest data, we evaluate the differential impact of harvest along the migration corridor of the population.The analysis reveals that (i) total harvest and harvest rate (proportion of the population killed by hunting) have increased substantially in recent years, (ii) compared to adult geese, juveniles were overrepresented in the hunting bag by a factor of 3·7, (iii) the proportion of juveniles in the hunting bag differed between the two countries (Norway and Denmark) with an open season, and was more than twice as high in the former compared to the latter, and (iv) the increase in harvest rate seemed to be driven by increased hunting mortality of juvenile birds, with no clear impact on the growth rate of the population. However, this may partly relate to the transient dynamics and population inertia commonly seen in long‐lived species such as geese, and a 3‐year consecutive decline towards the end of our study period might be the first signs of an impending decline.Synthesis and applications. Our findings highlight that the impact of harvest varies along the migration corridor and between age classes of a single species and suggest that allocation of hunting effort in time and space is important to optimise harvest. Our example demonstrates the need for internationally coordinated, detailed population and harvest data which are essential for sustainable harvest management.

Optimization of pumping policy using coupled finite element-particle swarm optimization modelling

An optimal pumping policy during groundwater extraction ensures the sustainability of groundwater resources. In this paper, a coupled finite element-particle swarm simulation–optimization model is implemented to assess the optimal pumping policy in a confined heterogeneous anisotropic synthetic aquifer. Pumping wells are set up in the aquifer to meet a specified water demand. The objective is to find the optimum number and pumping discharges of these wells such that their collective drawdown is minimized while meeting the demand at a reasonable cost. Constraints on the maximum allowable pumping discharge and the location of the wells are also imposed. After analysing the aquifer behaviour in the presence of 8, 9 and 10 pumping wells, the optimal number of wells is selected. The coupled FEM-PSO model also predicts the spatial distribution of the wells that incur the minimum cost for installation and pumping to a specified storage location. Adequate tuning of the PSO parameters involving population size, inertia weight, acceleration constants and number of iterations is performed to arrive at their optimal values.

The role of population inertia in predicting the outcome of stage-structured biological invasions

Deterministic dynamic models for coupled resident and invader populations are considered with the purpose of finding quantities that are effective at predicting when the invasive population will become established asymptotically. A key feature of the models considered is the stage-structure, meaning that the populations are described by vectors of discrete developmental stage- or age-classes. The vector structure permits exotic transient behaviour—phenomena not encountered in scalar models. Analysis using a linear Lyapunov function demonstrates that for the class of population models considered, a large so-called population inertia is indicative of successful invasion. Population inertia is an indicator of transient growth or decline. Furthermore, for the class of models considered, we find that the so-called invasion exponent, an existing index used in models for invasion, is not always a reliable comparative indicator of successful invasion. We highlight these findings through numerical examples and a biological interpretation of why this might be the case is discussed.

Beyond sensitivity: nonlinear perturbation analysis of transient dynamics

Summary1. Perturbation analyses of population models are integral to population management: such analyses evaluate how changes in vital rates of members of the population translate to changes in population dynamics. Sensitivity and elasticity analyses of long‐term (asymptotic) growth are popular, but limited: they ignore short‐term (transient) dynamics and provide a linear approximation to nonlinear perturbation curves.2. Population inertia measures how much larger or smaller a non‐stable population becomes compared with an equivalent stable population, as a result of transient dynamics. We present formulae for the transfer function of population inertia, which describes nonlinear perturbation curves of transient population dynamics. The method comfortably fits into wider frameworks for analytical study of transient dynamics, and for perturbation analyses that use the transfer function approach.3. We use case studies to illustrate how the transfer function of population inertia may be used in population management. These show that strategies based solely on asymptotic perturbation analyses can cause undesirable transient dynamics and/or fail to exploit desirable transient dynamics. This highlights the importance of considering both transient and asymptotic population dynamics in population management.4. Our case studies also show a tendency towards marked nonlinearity in transient perturbation curves. We extend our method to measure sensitivity of population inertia and show that it often fails to capture dynamics resulting from perturbations typical of management scenarios.

A framework for studying transient dynamics of population projection matrix models

Empirical models are central to effective conservation and population management, and should be predictive of real-world dynamics. Available modelling methods are diverse, but analysis usually focuses on long-term dynamics that are unable to describe the complicated short-term time series that can arise even from simple models following ecological disturbances or perturbations. Recent interest in such transient dynamics has led to diverse methodologies for their quantification in density-independent, time-invariant population projection matrix (PPM) models, but the fragmented nature of this literature has stifled the widespread analysis of transients. We review the literature on transient analyses of linear PPM models and synthesise a coherent framework. We promote the use of standardised indices, and categorise indices according to their focus on either convergence times or transient population density, and on either transient bounds or case-specific transient dynamics. We use a large database of empirical PPM models to explore relationships between indices of transient dynamics. This analysis promotes the use of population inertia as a simple, versatile and informative predictor of transient population density, but criticises the utility of established indices of convergence times. Our findings should guide further development of analyses of transient population dynamics using PPMs or other empirical modelling techniques.

POPULATION INERTIA AND ITS SENSITIVITY TO CHANGES IN VITAL RATES AND POPULATION STRUCTURE

Because the (st)age structure of a population may rarely be stable, studies of transient population dynamics and population momentum are becoming ever more popular. Yet, studies of "population momentum" are restricted in the sense that they describe the inertia of population size resulting from a demographic transition to the stationary population growth rate. Although rarely mentioned, inertia in population size is a general phenomenon and can be produced by any demographic transition or perturbation. Because population size is of central importance in demography, conservation, and management, formulas relating the sensitivity of population inertia to changes in underlying vital rates and population structure could provide much-needed insight into the dynamics of populations with unstable (st)age structure. Here, we derive such formulas, which are readily computable, and provide examples of their potential use in studies of life history and applied arenas of population study.

For whom the bell tolls: ecological perspectives on industrial decline and resurgence

Over the last twenty-five years, research in organizational ecology has given rise to a proliferation of mechanisms that seek to explain processes of decline and resurgence in mature industries. In this article, I consider four of these mechanisms--including arguments concerning competitive intensity, temporal heterogeneity, population inertia, and community ecology--and apply them to explain the evolution of US medical schools between 1765 and 1999. For this population, mechanisms relying on organizational variation in competitive intensity--especially, mass dependence accounts--perform poorly in terms of theoretical and empirical adequacy. Models that incorporate temporal heterogeneity in industrial competition and legitimation explain more variation in patterns of growth and decline, but are sensitive to right-censoring and model specification. Ecological mechanisms that explicitly analyze population inertia or community ecology seem to be the most promising in terms of theoretical and empirical consistency. Ironically, this finding seems to vindicate the model of population growth advanced in Hannan and Freeman's seminal article, which has sometimes been discounted as failing to represent the evolution of mature industries in a realistic manner. Copyright 2004, Oxford University Press.

Regional Dynamics of Plants: A Review of Evidence for Remnant, Source-Sink and Metapopulations

Despite a long tradition in plant ecology of studies of patch dynamics, recent developments of models for large scale dynamics in source-sink and metapopulations have largely focused on animals. In contrast to mobile unitary animals, many plants resist extinction. even under conditions where only a part of the life cycle can be maintained. This model of remnant population dynamics adds to the two commonly recognized source-sink and metapopulations dynamics. A review of the literature suggests that all three types of dynamics are common in plants. Regional dynamics are related to life-cycle characteristics determining dispersal ability and longevity of life cycle stages. Short-lived or highly habitat specialized plants with good dispersal tend to build up metapopulations, i.e. systems of local populations and non-occupied but potentially suitable sites, interconnected with dispersal. and in a continuous flux of local colonization and extinction. At the other extreme, long-lived plants with clonal propagation. or plants with extensive seed banks, tend to build up remnant population systems, in which many local populations persist over periods long enough to bridge unfavourable phases of successional development, intervening periods of favourable conditions. Source-sink populations are a special case of metapopulations, in the sense that they comprise both persistent refuge populations and ephemeral populations maintained by dispersal. It is suggested that a concept of local population inertia in remnant population systems, scales to higher level phenomena of vegetation inertia, and to community stabilization (through enhanced recovery after perturbations). Such an inertia may contribute to explain cases of exceptionally high species diversity, and lack of pronounced mass extinctions of plants in the fossil record.

Further analysis of Clark's delayed recruitment model

I explore the nonlinear behavior of a model in which the number of adults in each year is the sum of recruitment (which depends nonlinearly on adult abundanceT years in the past) and a constant fraction (survival) of adults in the previous year. Adding even a small amount of age structure to the semelparous version of this model (by increasing adult survival from zero) is stabilizing in that: (1) it shifts the value of slope at which the linearized model becomes unstable about the equilibrium to a lower value; and (2) it stretches the pattern of period doubling bifurcations so that bifurcations occur at much lower values of the slope. For the iteroparous case with a maturation and survival pattern reasonably typical of long-lived organisms, the period of cycles or quasi-cycles produced increases continuously as the slope of the stock-recruitment function decreases. The possibility of arbitrarily long cycles is not predicted by the linear theory, and has important practical implictions for analyses of cyclic populations. Both truncation of the age structure and an upper limit on recruitment seem to remove this gradual increase in period. However, the former can give rise to doubling of the period. Although the nonlinear behavior is not analysed in detail, a qualitative interpretation of the behavior of this model in terms of population inertia seems to explain the behavior observed in these numerical simulations.

Basin-scale coherence of population dynamics of an exploited marine invertebrate, the bay scallop: implications of recruitment limitation

Direct effects of a red tide (Ptychodiscus brevis) outbreak on bay scallops Argopecten irradians concentricus in North Carolina, USA, from October 1987 to February 1988 were necessarily limited to the 2 generations then present (adults of the year-class fished in winter 1987-88 and their progeny harvested in 1988-89), yet the 3 subsequent year-classes of bay scallops (those fished in the 1989-90, 1990-91, and 1991-92 winter seasons) also have been extremely depressed. The fishery crashed to about 10 to 15 % of the recent (25 yr) historical average harvest: no recovery has yet begun. This inability to recover quickly along with evidence of a previous gradual (5 to 12 yr) though erratic recovery from low population size in the early 1970's implies that this scallop population may be recruitment-limited at low density. Sampling of adults in August just before spawning and of new recruits surviving until early December in both 1988 and 1989 revealed that recruitment was positively related to adult abundance. This relationship was assessed across 9 bay scallop grounds in North Carolina. Settlement onto spat collector bags deployed at these sites dur~ng early autumn also tended to follow the same patterns of adult and recruit abundance among sites in 1988 but not in 1989. Patterns of adult and recruit abundance were broadly coherent across water bodies, with densities in Core Sound high, Back Sound relatively low, and Bogue Sound extremely low. Compared to identical sampling conducted during 3 years just preceeding the red tide outbreak, average autumn recruitment rates of bay scallops for 1988 and 1989 were normal in Core Sound, about 29 % of normal in Back Sound, and about 5 U/o of normal in Bogue Sound. This pattern continues to conform to the documented pattern of immediate direct effects of the red tide. Changes in area of its seagrass habitat appear incapable of explaining the sound-specific pattern of bay scallop declines following the red tide. This coherence of population dynamics on a basin scale implies that the bay scallop may be recruitmentlimited at low density by mesoscale or sound-wide abundance of spawning adults, creating lasting effects of the red tide propagated through basin-scale population inertia. Recruitment limitation for an exploited species would have important consequences for sustainability of harvest, if based on an effective stock-recruitment relationship, and may imply need for management intervention to enhance spawning stock within depleted basins.

Population regulation in the intertidal limpet Patelloida alticostata (Angas, 1865).

Subpopulations of the limpet, Patelloida alticostata, converged slowly toward a density of about 75 per linear meter of vertical rocky shore two years after experimental alteration of densities of adult animals. The changes in number of limpets in subpopulations occurred because large limpets suffered considerable mortality, while recruits experienced almost none. Neither migration, cannibalism, selection of settlement site by the limpets, nor predation by a whelk, acted in a density-dependent manner.Growth rates were density-dependent, and juveniles and recruits reached a much larger size in the absence than in the presence of adult limpets. Increasing the density of adult limpets did not increase the extent of grazing areas and subpopulations of different size compositions utilized similar grazing areas. Food may have been in short supply.These limpets have a great deal of population inertia, accommodating sporadic good recruitment by compensations in growth rates.

Population Regulation and Population Inertia

Regulation is defined as the return of a population to equilibrium density. An operational definition of regulation is convergence to a single density by subpopulations which have been manipulated previously to different densities. The equilibrium density may be fixed or variable. If the equilibrium is variable then regulation may produce instability (numerical inconstancy) and non—density—dependence. Population inertia is the tendency for a population to resist changes away from its current density. If speed of regulation is defined as |s|, the speed of convergence to equilibrium, then inertia is 1/|s|. The evolution of mechanisms of inertia involves changes in the demographic functions, mediated through physiology or behavior, which keep the rate of numerical change low. It is not clear if populations are control systems or non—control systems, which makes the convergence experiment difficult to interpret theorectically. Experiments and observations are needed which will try to distinguish, among stable populations, between those with tight regulation and those with high inertia.