Butterflies and Climate Change

Adult ETS depend on nectar which will no longer be available if the area’s flowers have bloomed prematurely. Like all 1st instar caterpillars, this freshly emerged ETS (Eastern Tiger Swallowtail) dines on tender young leaves. Higher early spring temperatures may speed up maturation of the host plant and render it inedible.

ETS caterpillars sit unprotected on their host plant’s upper leaf surface where they may suffer death from desiccation if temperatures are too high.

The Impact of Climate Change on Butterflies

Habitat loss and insecticides have long been significant threats to butterflies. Worldwide, including the United States, local populations have been exterminated and even entire species have been forced into extinction. A new threat, climate change, is already having deadly consequences for specific populations. Unless climate change is slowed or halted, many more butterfly habitats and species are at risk.

Plant and Animal Disconnects

Butterflies and their necessary plants evolved together over the past 200 million years. But the plants have adaptable genomes, able to quickly respond to changes in temperature, moisture, and competition for cooler habitats. New plant species may be created in as few as three generations in response to stressors! Animals are not as genetically nimble and may require thousands of years to make genetic adaptations. While butterflies are not as bound to specific flower bloom times as bees, the gravid (egg laden) butterflies have evolved to look for tender new leaf growth that will be appetizing and nutritious for their caterpillars. But when the caterpillar emerges from its egg, climate change may have prompted the foliage to mature earlier and now be tough and less nutritious. If a butterfly evolved in a particular cold zone and its environment is now warmer, the butterfly is no longer in synchrony with the plants that are necessary to its life.

Additional Extreme Weather Effects

Butterfly eggs are small and vulnerable, and may dry up in the higher temperatures. Likewise young caterpillars may dry up and blow away in the hot winds. Or the necessary plant may have died from heat or gone into its usual summer dormancy before the caterpillar has finished feeding. Or preferred flowers may have finished blooming before the butterfly emerges from its chrysalis.

Butterflies need water at all stages of their lives, whether they imbibe directly or through eating living plants. Migrating species are at special risk when droughts occur along their route. In 2020 thousands of Monarchs died on their way to Mexico because the wildflowers had shriveled in the Texas and Oklahoma droughts. Without nectar to fuel their journey, the butterflies also perished.

Storms are more episodic, creating long periods of torrential rain and flooding. Butterflies take shelter from storms by hanging under leaves or under tree bark. Storm surges can destroy these habitats and kill unprotected butterflies.

Warmer Winters

For butterflies adapted to spend the winter in diapause (insect hibernation), the warmer weather may speed metabolism so that the developing butterfly runs out of energy before it has completely transformed. Or the process may go so quickly that the butterfly emerges too soon and is killed by a late frost.

Summary

All life forms are susceptible to the changes in our warming environment, including butterflies. Since we humans are the stewards of this beautiful planet, we need to more aggressively respond to climate change. Our own survival may eventually depend upon our efforts to at least slow the rate of temperature rise.

LENORA LARSON Butterfly Maven

A Marais des Cygnes Master Gardener, Lenora is a member of the Idalia Butterfly Society and Kansas Native Plant Society. She gardens in the clay soil and cruel winds of Paola, KS. She may be contacted at lenora.longlips@gmail.com.