According to the Swedish University of Agricultural Sciences, SLU, this is a dramatic change.  

- There are scientific studies that show butterflies moving north if it gets warmer, so it may be related to a changed climate, says Karin Ahrné, SLU butterfly manager, Uppsala species database. 

The analysis, as the data journalist network J ++ done together with researchers at SLU Artdatabanken, shows that 40 butterfly species have moved more than five miles north in the country. For some relatively common species such as nettle butterfly and forest and meadow whitefly, the observations are made more than 30 miles further north than before.

The journalists and researchers analyzed 1.5 million observations reported to the Art Portal and compared two five-year periods. Only the species observed at least 500 times during both time periods 2005-2009 and 2015-2019 were included in the analysis. 

- If you were to do a scientific study, you would need to analyze the observation pattern a little more. This is not systematically collected data. It is reports to the Art Portal that private individuals do. And there are more and more people reporting, so there may be something in the pattern of how to report that affects where you see different species, Ahrné explains.

Karin Ahrné says that a changing climate means that researchers expect more extreme weather events such as drought or flooding, and it could affect butterfly species with limited distribution.   

- At the same time, the climate can affect other species, making it more favorable to spread over larger parts of the country. It depends on the species you are looking at.  

Butterflies contribute to pollination of plants, and are important food for birds, among other things. The most common butterfly was according to the Swedish Day Butterfly Surveillance's latest annual report 2018, odor grass butterfly, followed by rapeseed butter and lemon butterfly.

In the clip below you can see which five species of butterflies, which according to the data journalist network J ++ and SLU Artdatabanken's analysis, moved farther north in a ten year period.

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