scholarly journals Population regulation of African buffalo in the Mara–Serengeti ecosystem

2015 ◽  
Vol 42 (5) ◽  
pp. 382 ◽  
Author(s):  
Holly T. Dublin ◽  
Joseph O. Ogutu
Keyword(s):  
Land Use ◽  
Population Dynamics ◽  
Population Growth ◽  
Density Dependence ◽  
Food Limitation ◽  
Land Use Changes ◽  
African Buffalo ◽  
Regulatory Factor ◽  
Density Dependent ◽  
Serengeti Ecosystem

Context The processes regulating ungulate populations have been the focus of numerous studies. For the African buffalo (Syncerus caffer Sparrman) population inhabiting the Mara–Serengeti ecosystem, rinderpest was the primary regulatory factor up to the mid-1960s. Following reduction of rinderpest and buffalo population increase, interspecific competition for food, notably with cattle and wildebeest (Connochaetes taurinus Burchell), was thought to be the primary regulatory factor in the ecosystem. Aims We analysed buffalo population trends and the relationship between buffalo population growth and rainfall and density dependence in the Mara–Serengeti ecosystem and discuss the findings in the context of the key ecosystem processes governing buffalo population dynamics in African savannas, namely, food limitation, competition, predation, disease and land use changes. Methods We analysed buffalo population dynamics in the Mara–Serengeti ecosystem in relation to rainfall and density dependence feedback between 1984 and 2010. Key results Buffalo population growth was both significantly density-dependent and positively correlated with the dry season rainfall after, but not before, a severe drought in 1993. Buffalo numbers crashed by 48.6% in 1984–85 and by 76.1% in 1993–94 during severe droughts when food availability was lowest and competition with the more numerous cattle and wildebeest was highest. Conclusions Recovery of buffalo numbers to pre-drought levels took 8–9 years after the 1984–85 drought but was much slower, with buffaloes numbering merely 36% of their 1993 population (12 895 animals) 18 years after the 1993–94 drought despite intermittent periods of high rainfall, probably due to demographic and/or reproductive factors, heightened competition with livestock, land use changes in the adjoining pastoral ranches, lion predation and recurrent severe droughts. Implications Our findings demonstrate how food limitation caused by droughts associated with the hemispheric El Niño–Southern Oscillation can cause severe declines in and threaten the persistence of large ungulate populations. The findings also portray how density-dependent food limitation, competition, predation, land use changes and other factors can accentuate the effect of droughts and greatly prolong population recovery.

scholarly journals Increased natural mortality at low abundance can generate an Allee effect in a marine fish

2014 ◽  
Vol 1 (2) ◽  
pp. 140075 ◽  
Author(s):  
Anna Kuparinen ◽  
Jeffrey A. Hutchings
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Density Dependence ◽  
Gadus Morhua ◽  
Allee Effect ◽  
Population Regulation ◽  
Atlantic Cod ◽  
Adult Mortality ◽  
Natural Mortality ◽  
Density Dependent

Negative density-dependent regulation of population dynamics promotes population growth at low abundance and is therefore vital for recovery following depletion. Inversely, any process that reduces the compensatory density-dependence of population growth can negatively affect recovery. Here, we show that increased adult mortality at low abundance can reverse compensatory population dynamics into its opposite—a demographic Allee effect. Northwest Atlantic cod ( Gadus morhua ) stocks collapsed dramatically in the early 1990s and have since shown little sign of recovery. Many experienced dramatic increases in natural mortality, ostensibly attributable in some populations to increased predation by seals. Our findings show that increased natural mortality of a magnitude observed for overfished cod stocks has been more than sufficient to fundamentally alter the dynamics of density-dependent population regulation. The demographic Allee effect generated by these changes can slow down or even impede the recovery of depleted populations even in the absence of fishing.

scholarly journals Population dynamics and land-use changes in a Miang (Chewing Tea) village, Northern Thailand

Tropics ◽  
2007 ◽  
Vol 16 (2) ◽  
pp. 75-85 ◽  
Author(s):  
Ayako SASAKI ◽  
Shinya TAKEDA ◽  
Mamoru KANZAKI ◽  
Seiichi OHTA ◽  
Pornchai PREECHAPANYA
Keyword(s):  
Land Use ◽  
Population Dynamics ◽  
Land Use Changes ◽  
Northern Thailand

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.

scholarly journals Linking individual phenotype to density-dependent population growth: the influence of body size on the population dynamics of malaria vectors

2011 ◽  
Vol 278 (1721) ◽  
pp. 3142-3151 ◽  
Author(s):  
Tanya L. Russell ◽  
Dickson W. Lwetoijera ◽  
Bart G. J. Knols ◽  
Willem Takken ◽  
Gerry F. Killeen ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Body Size ◽  
Population Growth ◽  
Vector Control ◽  
Anopheles Gambiae ◽  
Phenotypic Expression ◽  
Phenotypic Traits ◽  
Density Dependent ◽  
Individual Fitness ◽  
The Impact

Understanding the endogenous factors that drive the population dynamics of malaria mosquitoes will facilitate more accurate predictions about vector control effectiveness and our ability to destabilize the growth of either low- or high-density insect populations. We assessed whether variation in phenotypic traits predict the dynamics of Anopheles gambiae sensu lato mosquitoes, the most important vectors of human malaria. Anopheles gambiae dynamics were monitored over a six-month period of seasonal growth and decline. The population exhibited density-dependent feedback, with the carrying capacity being modified by rainfall (97% w AIC c support). The individual phenotypic expression of the maternal ( p = 0.0001) and current ( p = 0.040) body size positively influenced population growth. Our field-based evidence uniquely demonstrates that individual fitness can have population-level impacts and, furthermore, can mitigate the impact of exogenous drivers (e.g. rainfall) in species whose reproduction depends upon it. Once frontline interventions have suppressed mosquito densities, attempts to eliminate malaria with supplementary vector control tools may be attenuated by increased population growth and individual fitness.

scholarly journals Determination of The Effects of Alucra Forest Planning Unit's Population Dynamics on Land Use Changes

2019 ◽  
pp. 35-46
Author(s):  
Günay ÇAKIR ◽  
Latif Gürkan KAYA ◽  
Cengiz YÜCEDAĞ ◽  
Sıtkı BAYRAM
Keyword(s):  
Land Use ◽  
Population Dynamics ◽  
Land Use Changes ◽  
Forest Planning

scholarly journals LAND USE CHANGES WITH POPULATION GROWTH

1975 ◽  
Vol 48 (1) ◽  
pp. 27-42
Author(s):  
Yasuyuki NISHIWAKI
Keyword(s):  
Land Use ◽  
Population Growth ◽  
Land Use Changes

scholarly journals Evolution of stochastic demography with life history tradeoffs in density-dependent age-structured populations

2017 ◽  
Vol 114 (44) ◽  
pp. 11582-11590 ◽  
Author(s):  
Russell Lande ◽  
Steinar Engen ◽  
Bernt-Erik Sæther
Keyword(s):  
Life History ◽  
Population Growth ◽  
Density Dependence ◽  
Population Size ◽  
Structured Populations ◽  
Environmental Stochasticity ◽  
Trade Off ◽  
Density Dependent ◽  
Fluctuating Environment ◽  
Stochastic Demography

We analyze the stochastic demography and evolution of a density-dependent age- (or stage-) structured population in a fluctuating environment. A positive linear combination of age classes (e.g., weighted by body mass) is assumed to act as the single variable of population size, N, exerting density dependence on age-specific vital rates through an increasing function of population size. The environment fluctuates in a stationary distribution with no autocorrelation. We show by analysis and simulation of age structure, under assumptions often met by vertebrate populations, that the stochastic dynamics of population size can be accurately approximated by a univariate model governed by three key demographic parameters: the intrinsic rate of increase and carrying capacity in the average environment, r0 and K, and the environmental variance in population growth rate, σe2. Allowing these parameters to be genetically variable and to evolve, but assuming that a fourth parameter, θ, measuring the nonlinearity of density dependence, remains constant, the expected evolution maximizes E[Nθ]=[1−σe2/(2r0)]Kθ. This shows that the magnitude of environmental stochasticity governs the classical trade-off between selection for higher r0 versus higher K. However, selection also acts to decrease σe2, so the simple life-history trade-off between r- and K-selection may be obscured by additional trade-offs between them and σe2. Under the classical logistic model of population growth with linear density dependence (θ=1), life-history evolution in a fluctuating environment tends to maximize the average population size.

Population dynamics of stage-structured sequential hermaphrodites

2013 ◽  
Vol 70 (9) ◽  
pp. 1296-1305
Author(s):  
Masami Fujiwara ◽  
Can Zhou
Keyword(s):  
Population Dynamics ◽  
Density Dependence ◽  
Sex Change ◽  
Fishing Mortality ◽  
Matrix Population Models ◽  
Density Dependent ◽  
Offspring Production ◽  
Male Density ◽  
Red Grouper ◽  
Ratio Dependent

The population dynamics of sequential hermaphrodites were investigated using three-stage matrix population models. A simple hermaphrodite model with density-dependent reproduction exhibited monotonic asymptotic growth or decline depending on parameter values. After incorporating density-dependent survival and sex change, the model was parameterized for red grouper (Epinephelus morio), which exhibit protogynous life history, and the model was used to investigate the effects of fishing mortality on offspring production and population density. The sensitivity of offspring production to fishing mortality was less when sex change depended on the relative density of female to male (ratio-dependent sex change) or male density alone compared with either female density alone or no density dependence. Although strong ratio-dependent sex change also resulted in less sensitivity of equilibrium abundance to fishing mortality, it caused the population to fluctuate chaotically. This suggests that the strength and type of density dependence on sex change affect reproductive output, equilibrium abundance, and the types of dynamics exhibited.

scholarly journals Problems seeded in the past: lagged effects of historical land-use changes can cause an extinction debt in long-lived species due to movement limitation

2022 ◽  
Author(s):  
María V. Jiménez-Franco ◽  
Eva Graciá ◽  
Roberto C. Rodríguez-Caro ◽  
José D. Anadón ◽  
Thorsten Wiegand ◽  
...  
Keyword(s):  
Land Use ◽  
Population Dynamics ◽  
Land Use Change ◽  
Animal Movement ◽  
Land Use Changes ◽  
Time Lag ◽  
Demographic Variables ◽  
Extinction Debt ◽  
Agricultural Abandonment ◽  
Historical Land Use

Abstract Context Land-use change is one of the main threats to biodiversity on the global scale. Legacy effects of historical land-use changes may affect population dynamics of long-lived species, but they are difficult to evaluate through observational studies alone. We present here an interdisciplinary modelling approach as an alternative to address this problem in landscape ecology. Objectives Assess effects of agricultural abandonment and anthropisation on the population dynamics of long-lived species. Specifically, we evaluated: (a) how changes in movement patterns caused by land-use change might impact population dynamics; (b) time-lag responses of demographic variables in relation to land-use changes. Methods We applied an individual-based and spatial-explicit simulation model of the spur-tighed tortoise (Testudo graeca), an endangered species, to sequences of real-world landscape changes representing agricultural abandonment and anthropisation at the local scale. We analysed different demographic variables and compared an “impact scenario” (i.e., historical land-use changes) with a “control scenario” (no land-use changes). Results While agricultural abandonment did not lead to relevant changes in demographic variables, anthropisation negatively affected the reproductive rate, population density and the extinction probability with time-lag responses of 20, 30 and 130 years, respectively, and caused an extinction debt of 22%. Conclusions We provide an understanding of how changes in animal movement driven by land-use changes can translate into lagged impacts on demography and, ultimately, on population viability. Implementation of proactive mitigation management are needed to promote landscape connectivity, especially for long-lived species for which first signatures of an extinction debt may arise only after decades.

scholarly journals Klasifikasi Visual on Screen Citra Satelit untuk Penggunaan Lahan (Studi Kasus: Kota Lhokseumawe)

2020 ◽  
Vol 4 (1) ◽  
pp. 677-681
Author(s):  
Ulfayani Ulfayani ◽  
Syakur Syakur ◽  
Muhammad Rusdi
Keyword(s):  
Land Use ◽  
Population Growth ◽  
Green Space ◽  
Land Use Changes ◽  
Rapid Population Growth ◽  
Survey Techniques ◽  
Spatial Use ◽  
Study Case ◽  
The City ◽  
Descriptive Method

Abstrak.  Perencanaan dan penataan kembali penggunaan lahan diperlukan dengan pertumbuhan penduduk yang cepat. Penggunaan lahan yang bersifat dinamis serta pertumbuhan jumlah penduduk mendorong untuk dilakukannya perencanaan dan pemantauan pemanfaatan ruang di suatu lokasi daerah yang berdekatan dengan kota. Hal tersebut sangat mempengaruhi tingkat kepadatan penduduk dan perubahan penggunaan lahan yang terjadi. Adapun tujuan penelitian adalah untuk memetakan penggunaan lahan di Kota Lhokseumawe. Metode yang digunakan dalam penelitian ini adalah metode deskriptif dengan teknik survey. Hasil kajian menunjukkan penggunaan lahan yang terbesar yaitu RTH (Ruang Terbuka Hijau) dengan luas 5.613,92 ha (38,64%) dan penggunaan lahan yang paling kecil yaitu PPI (Pangkalan Penampungan Ikan) dengan luas 3,23 ha (0,02%) dari luas keseluruhan wilayah.(Visual Classification on Screen Satellite Imagery for Land Use (Study Case: Lhokseumawe City)Abstract. Planning and realignment of land use is needed with rapid population growth, dynamic land use and population growth encourage planning and monitoring of spatial use in a location near the city. This greatly affects the level of population density and land use changes that occur. The research objective is to map the land use in Lhokseumawe City. The method used in this research is descriptive method with survey techniques. The results of the study show the largest land use namely green space with an area of 5,613.92 ha (38.64%) and the smallest land use namely fish shelter base with an area 3,23 ha (0,02%) of the total area.

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