Have you noticed that spotting a butterfly in Metro Vancouver almost seems like a rare occurrence? Well, a UBC expert suggests you’re not alone in thinking there are fewer butterflies in the sky.
According to Dr. Michelle Tseng, a UBC assistant professor, butterfly sightings have dropped 60% this spring.
Considering many insects living in cities play a tremendous role in creating a healthy environment, “a drop in butterflies is something to pay attention to.”
Why are there fewer butterflies?
Tseng explains that a cooler and wetter spring could be one factor contributing to the decrease in butterfly sightings.
Because butterflies don’t like flying in the rain, we’re less likely to see them when the region experiences showers.
“Butterfly species that ‘overwinter,’ or spend the colder months in their pupal stage as a chrysalis, require a certain amount of heat to continue developing into adults,” she continued in a UBC post. “This is usually prompted as the seasons turn, but if the spring has been cooler, it takes the insects longer to develop and consequently, the adults emerge later in the spring.”
It’s been partially “unusual“ how widespread the absence of butterflies has been, like in regions from North Vancouver to Burnaby to central Vancouver, Tseng pointed out.
“Another factor could be the spraying of insecticides to combat invasive pest insects,“ Tseng added. “These could also have the potential to harm butterflies.”
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Tseng admits it’s a challenging balance keeping invasive or pest insects and plants out of an area while protecting native insects and plants.
Tseng suggested that, with the warmer weather, people might start seeing cabbage whites flying around the region.
Why are butterflies important?
Dr. Michelle Tseng/UBC
In our world, butterflies are exceptionally important as they play a role. Tseng explained they are one of many insect pollinators that 75% of the world’s crops depend on.
Additionally, because butterflies are sensitive to environmental conditions, Tseng said they can be one of the first indicators if something is off in an environment.
“It’s possible something happened last fall,“ Tseng said. “Something that has been worrying ecologists for a while is that summers are staying warmer later due to climate change. Is it the case that instead of starting their winter hibernation or diapause, the caterpillars were tricked by these long, warm summers into not preparing for winter correctly by turning into a chrysalis?”
What can we do?
In a recent paper, Tseng said that in Vancouver, native street trees support five times as many native butterfly species as non-native trees.
“So we could start to use our city trees for multiple purposes: not just shade and heat control, but to also increase insect diversity in our urban areas,“ she suggested.
In addition, people can reduce their use of insecticides and plant more native plants for the caterpillars to eat and flowers that produce nectar for the adults.
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