Butterflies as Bellwethers of Climate Change

I am sharing material about butterflies coping with climate change, taking facts from an article titled “Soft-winged Sentinels”, written by Madeleine Finlay, published in New Scientist Magazine, July 11-17, 2020 edition. New Scientist is based in the United Kingdom. Any omissions or errors in the following are mine. L. Glover

Butterflies are cold-blooded animals and thus very sensitive to warming. Their life spans are short, so studying them offers an opportunity to look into how warming affects them and how they are adapting to it. Since butterflies are widely studied by professional and amateur biologists, there is abundant information available.

Logically, some butterflies are seeking cooler environments in which to live. There is a species called the Long-tailed Blue, ​Lampides boeticus, ​native to the Mediterranean, for example. It has been found in England and Wales in greater and greater numbers over the past decade, moving northward in search of a more hospitable habitat.

The Canadian Swallowtail ​Papilio canadensis, ​and Eastern Tiger Swallowtail, ​Papilio glaucus, ​meet and interbreed in a narrow band extending from Minnesota to New England. This region has moved northward 40 km since the 1980s.

Butterflies which rely on moving upwards in elevation to find cooler temperatures could run out of altitude and food. Interestingly, in the Rocky Mountains, Sulphur butterflies, ​Colias philodice, ​have evolved lighter wings and the ability to change their wing colour, depending on temperature during their pupal stage. Both of these abilities are an advantage as temperatures rise.

Butterflies which have multiple breeding cycles have some flexibility as to habitat and some have evolved to feed on different plants. However, for others, emerging too early in the season or arriving in an area before acceptable pollen sources are available can mean death. Specialist butterflies are particularly hard-hit, since they may have only 1 food source and cannot adapt to another.

Around the world, the diversity and sheer numbers of butterflies has declined, due to pesticide use, habitat loss and climate change. Even the generalists may not be able to adapt quickly enough to the changes to survive.

What can we do? Reduce carbon emissions, preserve and expand nature reserves, and make your own garden a pesticide free, native plant habitat.

Submitted by Leslye Glover