Editing Small population size (section)

== Island populations ==
[[File:Galapagos Islands topographic map-en.svg|thumb|The Galapagos Islands are home to a high level of endemism due to its natural history and geography. However, many of its species are endangered due to introductions of exotics, habitat loss and climate change.]]

Island populations often also have small populations due to geographic isolation, limited habitat and high levels of endemism. Because their environments are so isolated [[gene flow]] is poor within island populations. Without the introduction of genetic diversity from gene flow, alleles are quickly fixed or lost. This reduces island populations' ability to adapt to any new circumstances<ref name="villemereuil">{{cite journal |last1=de Villemereuil |first1=Pierre |title=Little Adaptive Potential in a Threatened Passerine Bird |journal=Current Biology |date=2019 |volume=29 |issue=5 |pages=889–894 |doi=10.1016/j.cub.2019.01.072 |pmid=30799244 |ref=villemereuil|doi-access=free |bibcode=2019CBio...29E.889D }}</ref> and can result in higher levels of extinction. The majority of mammal, bird, and reptile extinctions since the 1600s have been from island populations. Moreover, 20% of bird species live on islands, but 90% of all bird extinctions have been from island populations.<ref name=":2" /> Human activities have been the major cause of extinctions on island in the past 50,000 years due to the introduction of exotic species, habitat loss and over-exploitation.<ref>World Resources Institute, International Union for Conservation of Nature, & Natural Resources. (1992). ''Global biodiversity strategy: Guidelines for action to save, study, and use earth's biotic wealth sustainably and equitably''. World Resources Inst.</ref>

The [[Galapagos penguin]] is an endangered endemic species of the Galapagos islands. Its population has seen extreme fluctuations in population size due to marine perturbations, which have become more extreme due to climate change. The population has ranged from as high as 10,000 specimens to as low as 700. Currently it is estimated there are about 1000 mature individuals.<ref name=":3" />