Editing Small population size (section)

==Environmental effects==
The environment can directly affect the survival of a small population. Some detrimental effects include [[stochastic]] variation in the environment (year to year variation in rainfall, temperature), which can produce temporally correlated birth and death rates (i.e. 'good' years when birth rates are high and death rates are low and 'bad' years when birth rates are low and death rates are high) that lead to fluctuations in the population size. Again, smaller populations are more likely to become extinct due to these environmentally generated population fluctuations than the large populations.

The environment can also introduce beneficial traits to a small population that promote its persistence. In the small, fragmented populations of the [[acorn woodpecker]], minimal immigration is sufficient for population persistence. Despite the potential genetic consequences of having a small population size, the acorn woodpecker is able to avoid extinction and the classification as an endangered species because of this environmental intervention causing neighboring populations to immigrate.<ref>{{Cite journal|last1=Stacey|first1=Peter B.|last2=Taper|first2=Mark|date=1992-02-01|title=Environmental Variation and the Persistence of Small Populations|journal=Ecological Applications|language=en|volume=2|issue=1|pages=18–29|doi=10.2307/1941886|pmid=27759195|issn=1939-5582|jstor=1941886|bibcode=1992EcoAp...2...18S |s2cid=37038826}}</ref>  Immigration promotes survival by increasing genetic diversity, which will be discussed in the next section as a harmful factor in small populations.