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Word of the Week: Extirpation
July 08, 2022 by High Park Nature Centre

Welcome to Word of the Week! Stay tuned for a new word each week to amp up your nature vocabulary!

The word of the week is extirpation [uhk-stur-pay-shn] (noun): a species of plant or animal ceasing to exist in a specific georgraphic area while still existing elsewhere.

This biological term is also commonly called local extinction. Extirpation of species have been taking place for as long as there have been living beings on Earth. This can be due to natural causes, like physical changes in nature, or due to human presence and activity.

An example of a natural event which resulted in local extinction was the extirpation of many native North American species of earthworm in areas that were covered by glaciation during the "ice age." Other natural events that have caused extirpation include volcanic eruptions or seperation of islands from the mainland.

A noteable example of an extirpated species which used to be found in High Park are Karner Blue butterflies (pictured above). They were last seen in High Park in 1926 and they haven't been seen in Ontario since 1991. In 2003, Karner Blue was listed as an extripated species in Canada. Today, they can still be found in the United States in some states in the Great Lakes and the Northeast.

While there are examples of successful reintorductions of other extirpated species, there are several specific challenges to reintroducing some types of species like the Karner Blue. According to the Canadian Species at Risk Act's recovery strategy for Karner Blues and similarly extirpated butterflies, the species' specialized habitat requirements, narrow environmental tolerances, dependence on environmental cues that are disrupted by climate change, dependence on interactions with particular species, poor ability to disperse to or colonize suitable new habitats, and small population size, area of occupancy, or extent of occurrence, are some of the factors that limit reintroduction efforts.

Wild Lupine, for instance, is crucial to the survival of Karner Blue butterflies. They lay their eggs only on Wild Lupine and their caterpillars feed only on Wild Lupine leaves. The loss of the Karner Blue butterflies in North America concides with the loss of their oak savannah habitats. While restoration efforts in High Park have benefited Lupines, there's still a long way to go before this species is butterfly can be restored in the park.

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