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The route to extinction in variable environments
Author(s) -
Ripa Jörgen,
Lundberg Per
Publication year - 2000
Publication title -
oikos
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.672
H-Index - 179
eISSN - 1600-0706
pISSN - 0030-1299
DOI - 10.1034/j.1600-0706.2000.900109.x
Subject(s) - extinction (optical mineralogy) , carrying capacity , population , population viability analysis , ecology , population growth , per capita , extinction probability , environmental noise , econometrics , population size , environmental science , biology , economics , demography , habitat , endangered species , physics , paleontology , sociology , acoustics , sound (geography)
Estimating the extinction risk of natural populations is not only an urgent problem in conservation biology but also involves some profound aspects of population dynamics. Apart from the obvious case of a continuous decrease in a population's carrying capacity, understanding the extinction process necessarily includes environmental and demographic stochasticity. Here, we build from first principles two stochastic, single‐population models that can account for various routes to extinction via demographic and environmental variability.
The Ricker model of population dynamics generates extinctions from either low or high (around or above carrying capacity) population densities, primarily depending on the growth parameter r . Since extinctions from high densities seem ‘unnatural’, there is either something wrong with the model or with our intuition. Suitable data are scarce.
Environmental variability has its strongest influence on extinction risk via per capita birth rates and is only marginally influencing that risk via per capita death rates if the growth parameter is high. The distribution of the environmental noise and the stochastic structure of the model have quantitative, but not qualitative effects on the estimates of extinction risks.
We conclude that to determine the route to extinction and to estimate the extinction risk require a careful choice of both the deterministic component of the population model (e.g., under‐ or over‐compensation) and the structure of the demographic and environmental variabilities.