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A new study led by the University of Helsinki examined how climate change is altering moth communities across Finland. The researchers wanted to understand whether communities are undergoing thermophilization—a shift towards species that prefer warmer conditions—as the climate warms.

The team drew on a long-term dataset built through decades of dedicated volunteer monitoring. It includes more than 224,000 moth observations collected across Finland's 1,200 km length over two 30-year periods. This extraordinary effort made it possible to uncover how climate change is reshaping moth community composition across the country.

Their findings confirm that Finnish moth communities are becoming increasingly dominated by warm-adapted species. While the community warming was consistent across the country, the mechanisms that lead to it were strikingly different. The results are in Nature Communications.

In northern Finland, thermophilization was primarily driven by the disappearance of cold-adapted species. In contrast, southern Finland experienced thermophilization through the arrival of new warm-adapted species, while most resident species persisted.

These findings suggest that cold-adapted species in northern Finland are particularly vulnerable under climate change, as the communities face more species losses than additions. This pattern points to a greater risk for communities at the cold edge of species' climatic ranges.

"The rate of change in the composition of moth communities was twice as fast in the North compared to the South," says lead author Dr. Emilie Ellis from the Research Center for Ecological Change. "That rapid pace makes northern biodiversity especially vulnerable to the harmful effects of climate warming."

Recognizing that cold-adapted species are at risk will help to inform conservation strategies to support Finnish biodiversity. Continued monitoring and research are therefore crucial to tracking how these species are changing over time.