Butterflies show us that climate change is real

A major study published in Nature on butterflies found in Finland and Sweden over the past 120 years reveals significant changes.
“Butterflies are moving northward, so new species arrive here. They are our most important pollinators, and our environment will be affected, although we can’t fully grasp how yet,” says Nils Ryrholm, professor of biology at University of Gävle.

A study examining the connection between the presence of butterflies and climate change combined with changes in the landscape caused by human activities over such a long period as from 1901 to 2019 has never been conducted before.

“As people have studied butterflies for a very long time, we know a lot about them. The changes are now very apparent. Climate change, coupled with human impact on the landscape, is happening at a faster pace now,” says Nils Ryrholm.

Butterflies act as canaries in the coal mine. As most butterflies have a lifespan of only one year, they disappear if they don't survive, and such changes were just as noticeable a hundred years ago.

“Such changes are much harder to determine if we study birds or vertebrates. Puffin populations in the Atlantic are disappearing because their offspring cannot survive due to overfishing. However, as they have a lifespan of 40 years, their existence appears to be unthreatened, but they are in fact doomed,” Nils Ryrholm says.

The butterflies move north

In Sweden and Finland, butterflies are currently moving northward. However, the most significant difference is observed in areas where the climate is noticeably warmer, and the temperature increase is greater in the north. Butterflies come in from the south and the east, leading to changes in species composition, and several species have been added.

Moreover, extinction rates are starting to increase in Sweden. Some species have gone extinct in recent years, making them the first known butterflies to disappear. However, the change mainly involves migration, and migration has always occurred whenever conditions have allowed.

“Butterflies have always been ready to expand in all directions. But now the change is obvious, and everything is happening much faster.”

“This will impact our environment, but we can't fully grasp how yet. Right now, we are discussing butterflies, the best pollinators, but plants, insects, and parasites will also be affected.

What comes next?

At higher latitudes, there is an increase in the number of species, and the number of incoming species exceeds the number disappearing ones, according to the researchers. The Map Butterfly, which arrived in Sweden in 1982, is now found in Gävle. In the 1960s, its northern range was central Germany. Other butterflies that previously had their northern range in southern Poland can now be found in Hälsingland.

“The landscape is losing its richness, as the newcomers are often very adaptable generalists, like crows and magpies. At the same time, rarer species such as little grebes and horned grebes are disappearing.”

Importantly, Nils emphasizes that we cannot predict which species will come and which species that will go. When new opportunities for life arise, parasites and other lifeforms that we cannot even see will arrive. These can potentially eliminate pollinators, leading to poorer pollination of some of our crops.

“The Siberian tick is a good example of this phenomenon. This tick carries a more pathogenic virus, and many other insects are now moving westward. With a warmer climate, mosquitoes capable of transmitting diseases such as Dengue fever and West Nile fever may also appear.”

“These are very clear facts that demonstrate that climate change is real and has consequences which we cannot yet predict,” Nils Ryrholm says.

Text: Douglas Öhrbom