Butterfly Indicators of Ecosystem Change

Butterfly Canaries in the Earth Ecosystem Coalmine

Two-tailed Swallowtail

Two-tailed Swallowtail

Guest post by Leslie Olsen

Predicting the effects of climate change and other human impacts on Earth ecosystems is a critical goal for policy makers, scientists, and environmentalists. Some effects, such as weather extremes and biodiversity decline are becoming clear to everyone. One group of species, the butterflies, is especially sensitive to environmental change, and scientists are using the group to gauge the effects of the changes on other species.

Like canaries in a coalmine, butterflies can serve as valuable indicators of significant changes. Butterflies are easy to see. Moreover, their metabolism and short life span make their numbers an especially sensitive gauge of environmental changes. When a butterfly population falls, other species may follow. Fluctuations in temperature patterns, temperature extremes, droughts, floods, and severe storms affect butterfly populations throughout North America. Studies on the impact of climate changes on insects and butterflies are particularly rare, but recent data and observations are spurring research.

Changes in butterfly emergence, range, life cycle, feeding habits and diversity can indicate harmful environmental changes are occurring. For example, butterfly life cycle stages are tied to the availability of certain plants; even subtle changes in plant species abundance is reflected in butterfly health, color, and number. The animals and birds dependent on butterfly populations are directly affected.

Monarch (Danaus Plexippus)

Monarch (Danaus Plexippus)

A familiar butterfly, the Monarch, migrates almost three thousand miles every year and has suddenly declined because of pesticides (first two references below) and forest thinning in its winter home territory in Mexico.

Another butterfly, the Poweshiek skipperling, once plentiful across the Canadian prairies had declined to fewer than 200 individuals, most of them in Manitoba (Toronto Star).
Last year, the United States Fish and Wildlife Service announced the extinction of two butterfly species, the Zestos skipper and the Rockland grass skipper.

Researchers from the University of British Columbia, the Université de Sherbrooke and the University of Ottawa, in a study of more than 200 species of butterflies and weather data from 130 years “found butterflies possess widespread temperature sensitivity, with flight season occurring an average of 2.4 days earlier per degree Celsius of temperature increase” (UBC. 2013).

Heather Kharouba, lead author noted that butterflies “provide an early warning signal for how other wildlife may respond to climate change” (UBC). The impact of warmer temperatures causes butterflies “to emerge and start their active flight season earlier in the year, and if they emerge too early, they could encounter frost and die. Or they might emerge before the food plants they rely on appear and starve” (Ibid).

As more researchers begin studying butterflies, the links to other species and whole ecosystems will become clearer and will help guide nature conservation plans and policies.  Thus, our floating jewels not only add grace and beauty to our lands, they are on the front line of our battle to save Earth’s wildlife and ecosystems.

Butterfly References

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