Classics: Declining and small population paradigms

23 08 2008

‘Classics’ is a category of posts highlighting research that has made a real difference to biodiversity conservation. All posts in this category will be permanently displayed on the Classics page of

image0032Caughley, G. (1994). Directions in conservation biology. Journal of Animal Ecology, 63, 215-244.

Cited around 800 times according to Google Scholar, this classic paper demonstrated the essential difference between the two major paradigms dominating the discipline of conservation biology: (1) the ‘declining’ population paradigm, and the (2) ‘small’ population paradigm. The declining population paradigm is the identification and management of the processes that depress the demographic rate of a species and cause its populations to decline deterministically, whereas the small population paradigm is the study of the dynamics of small populations that have declined owing to some (deterministic) perturbation and which are more susceptible to extinction via chance (stochastic) events. Put simply, the forces that drive populations into decline aren’t necessarily those that drive the final nail into a species’ coffin – we must manage for both types of processes  simultaneously , and the synergies between them, if we want to reduce the likelihood of species going extinct.

CJA Bradshaw

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4 responses

27 09 2017
Four decades of fragmentation |

[…] We can also attribute our general understanding of how population dynamics respond to fragment instability to the BDFFP, for we now know that population fluctuations within them lead to greater variability from extreme weather events or other stochastic phenomena, thus increasing the probability of populations dipping below minimum viable sizes and becoming locally extinct. […]


26 06 2015
The extinction vortex |

[…] were labelled by Gilpin & Soulé, the concept was subsequently simplified by Caughley (1994) in his famous paper on the declining and small population paradigms, but only truly quantified for […]


18 10 2011
Not magic, but necessary «

[…] 2007, 2010; Clements et al. 2011) – a minimum viable population size is the point at which a declining population becomes a small population (sensu Caughley 1994). In other words, it’s the point at which a population becomes […]


22 12 2008
Classics: the Allee effect «

[…] than expected by chance alone because of self-reinforcing feedbacks (see also previous post on the small population paradigm). Thus, ignorance of potential Allee effects can bias everything from minimum viable population […]


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