Warming temperatures could alter the flight season timing of a range of butterfly species, according to a new study.
The study, published in Global Change Biology, used data from Canadian museum collections of more than 200 species of butterflies and looked at these species’ sensitivity to temperature changes. When lined up with 130 years of weather station data, the researchers found that the butterflies’ flight seasons — which begin either when butterflies emerge from hibernation in the spring or when the first butterflies of the season emerge from their chrysalises, depending on the species — started an average of 2.4 days earlier for each degree Celsius in rise in temperature.
That early emergence can be bad news for butterflies, the researchers found. “With warmer temperatures butterflies emerge earlier in the year, and their active flight season occurs earlier,” says Heather Kharouba, lead author of the paper published this week in Global Change Biology. “This could have several implications for butterflies. 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.”
The study isn’t the first to document the effect warmer weather and earlier springs can have on butterflies. In February, a study from Boston University yielded similar results, with researchers determining that flight season began an average of two days early for each degree Fahrenheit increase in temperature. The Boston study found the sensitivity of butterflies to temperature was similar in degree to bees’ and plants’ sensitivity, with both bees and plants arriving or flowering early in response to warmer temperatures. But it was much greater than birds’ sensitivity, with many birds responding to changes in day length or other signals to determine when to migrate — meaning there’s a bigger risk of birds arriving to their spring grounds after flowers and insects are at their peak as temperatures warm.
Another study found climate change could affect the migration of monarch butterflies, which migrate from Mexico to the southern U.S. when weather gets warm, where they lay their eggs. The study found that monarchs needed a cold trigger in order to continue migrating south to Mexico in the fall — without those cold conditions, monarchs in the midst of migrating south can actually reorient themselves and fly north.
“How many days of the low temperature are needed or the actual temperatures themselves are just not known. All we know is that for 24 days, day and night, if we mimic temperatures in Mexico, on top of the mountains there, the butterflies then start traveling north,” author Steven Reppert said.
Extreme weather could also pose a major threat to monarchs. in 2002, a severe storm in Mexico killed nearly 80 percent of the monarch butterfly population there.
“That was a very extreme and unusual weather event. It’s usually the dry season; there aren’t big storms there, but they just had a lot of precipitation. That was followed by cold temperatures, so that juxtaposition of precipitation and cold just killed all the butterflies,” Karen Oberhauser, a professor in the Department of Fisheries, Wildlife and Conservation Biology at the University of Minnesota told ClimateWire. “Clearly, that kind of storm is predicted to be more common under climate change scenarios.”