JoAnne Skelly: Butterflies and climate change

People are talking about climate change, particularly after the recent presidential election. As areas warm, vegetation patterns change, with less heat-tolerant plants moving up to higher elevations as more heat-tolerant species replace them. Water supplies can be affected. Habitat modification and fragmentation causes distribution changes not only in vegetation, but also in birds, animals and insects, such as butterflies.

Dr. Arthur Shapiro, butterfly expert and professor of evolution and ecology at University of California, Davis, has been observing and recording data on butterflies for more than 35 years. Twice monthly, he has been making observations at 10 sites in north-central California from sea level to tree line. His butterfly database is exceptional for its long-term data collection by one person at multiple sites covering over 150 species of butterflies. It includes climatological data. Six years ago, he and his colleagues analyzed the data he had collected and reported:

“Butterfly diversity (the number of different species present) is falling fast at all the sites near sea level. It is declining more slowly or holding roughly constant in the mountains, except at tree line.”

“At tree line, butterfly diversity is actually going up, as lower-elevation species react to the warming climate by moving upslope to higher, cooler elevations.”

“Diversity among high-elevation butterflies is beginning to fall as temperatures become uncomfortably warm for them.” (https://phys.org/news/2010-01-butterflies-reeling-impacts-climate.html#jCp)

Butterflies are particularly sensitive to climate change and the ensuing habitat alterations. Some species respond by moving northward or up to higher elevations where their preferred food source may exist. Changes in climate affect “species’ life cycles, flight times, essential interactions and ultimately survival,” (Caldas, Spring 2012. American Butterflies). Climate change also can influence timing and amount of reproduction, flight times and have multiple cascading effects (Caldas).

Monarch migration patterns are changed by warmer-than-normal temperatures on either end of their seasonal journeys with delayed departures from the north or premature flights northward in the spring from Mexico (February 2013, Narayanan, Scientific American). Ill-timed migrations can result in high mortality rates.

However, the changing diversity of butterfly species is not solely determined by climate change; the issue is more complex than that. In addition to changing weather patterns, development has played a significant role as well, causing a substantial loss in habitat and food sources. Degradation of native habitat reduces a species capacity to respond to climate change. There is need for better understanding of how climate affects butterflies and moths.

JoAnne Skelly is Associate Professor & Extension Educator, Emerita at University of Nevada Cooperative Extension. She can be reached at skellyj@unce.unr.edu.