Environmental stochasticity
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Environmental stochasticity is a concept of population dynamics that describes random environmental chance events that result in the variation of population size. The fluctuation of population sizes is a result of changes in mortality and reproduction rates of all individuals in the population.[1]
Extinction
The fluctuating population sizes puts a population at more risk of extinction. Furthermore, environmental stochasticity influences both small and large populations significantly. However, smaller populations are naturally more vulnerable to extinction.
Environmental stochasticity cannot stop or change a population that is trending toward extinction. However, it can either exacerbate or lower the vulnerability of the population - resulting in speeding up or lowering of the rate of extinction depending on the intensity of stochasticity.[2]
There is a negative correlation between population levels and the intensity of environmental stochasticity when the population are under weak Allee effects (i.e. higher intensity of stochasticity leads to lower population levels).[2] This puts the said population at risk of extinction. On the other hand, populations under strong Allee effects risk of extinction are dependent on the initial population level.[2]
Growth Rate
Annual growth rate equation with only environmental variation considered [3]:
Where:
= growth rate dependent on state of the environment
= annual project matrices dependent on state of the environment
=population number in the different ages or stages
In comparison to the basic population growth model:
Relation to Demographic Stochasticity
Unlike demographic stochasticity, the effects of environmental stochasticity is independent of population size.[4] The environmental changes influence each individual through the same mechanism, resulting in the whole population being affected positively or negatively in the same way [5]. Environmental stochasticity has greater influence over demographic stochasticity concerning the risk of extinction in sufficiently large population sizes.[6]
Example
Environmental events can consist of modification to abiotic or biotic factors. Examples include but are not limited to changes in temperature, floods, droughts, heatwaves, soil erosion, disease, predation, and food availability.
In environments where populations do not suffer from predation from large carnivores, populations of moose and red deer have a higher neonatal mortality rate in the summer than during the winter.[7]
An increased variance in annual rainfall in combination with significant years of drought resulted in reduced viability of the population of Asiatic wild ass.[8]
References
- ^ Lande, Russell; Engen, Steinar; SÆther, Bernt-Erik (2003-04-03), Lande, Russell; Engen, Steinar; Saether, Bernt-Erik (eds.), "Demographic and environmental stochasticity", Stochastic Population Dynamics in Ecology and Conservation, Oxford University Press, p. 0, doi:10.1093/acprof:oso/9780198525257.003.0001, ISBN 978-0-19-852525-7, retrieved 2025-02-17
- ^ a b c Feng, Tao; Zhou, Hongjuan; Qiu, Zhipeng; Kang, Yun (2022-11-01). "Impacts of demographic and environmental stochasticity on population dynamics with cooperative effects". Mathematical Biosciences. 353: 108910. doi:10.1016/j.mbs.2022.108910. ISSN 0025-5564.
- ^ Knape, Jonas; Paquet, Matthieu; Arlt, Debora; Kačergytė, Ineta; Pärt, Tomas (2023). "Partitioning variance in population growth for models with environmental and demographic stochasticity". Journal of Animal Ecology. 92 (10): 1979–1991. doi:10.1111/1365-2656.13990. ISSN 1365-2656.
- ^ Xu, Kuangyi; Vision, Todd J.; Servedio, Maria R. (2023-10-01). "Evolutionary rescue under demographic and environmental stochasticity". Journal of Evolutionary Biology. 36 (10): 1525–1538. doi:10.1111/jeb.14224. ISSN 1010-061X.
- ^ Dallas, Tad; Melbourne, Brett A.; Legault, Geoffrey; Hastings, Alan (2021). "Initial abundance and stochasticity influence competitive outcome in communities". Journal of Animal Ecology. 90 (7): 1691–1700. doi:10.1111/1365-2656.13485. ISSN 1365-2656.
- ^ Lande, Russell (1993-12). "Risks of Population Extinction from Demographic and Environmental Stochasticity and Random Catastrophes". The American Naturalist. 142 (6): 911–927. doi:10.1086/285580. ISSN 0003-0147.
{{cite journal}}: Check date values in:|date=(help) - ^ Xu, K; Vision, T. J.; Servedio, M. R. (2023). "Evolutionary rescue under demographic and environmental stochasticity". Journal of Evolutionary Biology. 36 (10): 1525–1538 – via Trends in Ecology & Evolution.
- ^ "The Impact of Increased Environmental Stochasticity Due to Climate Change on the Dynamics of Asiatic Wild Ass". doi:10.1111/j.1523-1739.2006.00486.x. ISSN 1523-1739.
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