Three Out of Four Rare Butterflies Are Missing

Mazarine blue (Cyaniris semiargus). Credit: Emil Blicher Bjerregård

Over a period of 26 years, Eastern Denmark has seen a 72% decline in the presence of rare butterflies. There are many species now they are on the verge of disappearing. Despite conservation efforts, conservation measures have not had positive results. This is the conclusion of a comprehensive study from the University of Copenhagen.

They’re like Danish summer staples like cold butter soup, sweet strawberries, and dandelions — but we’re terrible at taking care of them. Many of Denmark’s butterfly species have been in sharp decline for decades, a trend that continues at a rapid pace according to research from the University of Copenhagen. Furthermore, current conservation efforts do not seem to be helping rare species, as intended.

Data collected over a period of six years by biologist Emil Blicher Bjerregård determines the extent of the decline in twenty-two species of rare butterflies across Eastern Denmark. Many of these species are endangered.

Northern checkered skipper (Carterocephalus silvicola). Credit: Emil Blicher Bjerregård

“The distribution of twenty-two species of butterflies that we have been monitoring in Zealand, Lolland, Falster and Møn has decreased by 72 percent since 1993. left. I wouldn’t be surprised if at least eight species become extinct within a few years. These include pearl-bordered fritillary, mazarine blue, and Northern checkered skipper,” says Emil Blicher Bjerregård.

Bjerregård, a newly minted biologist at the University of Copenhagen, is the lead author of the research paper on the study, alongside contributing researchers from the University of Copenhagen’s Department of Biology and Department of Mathematical Sciences.

Lack of primary residence

The researchers compared the number of so-called “occurrence areas” in Eastern Denmark, areas where one or more individuals of the target butterfly species were present, with the situation before 1993, when the last butterfly distribution map was made. In 1993, twenty-two species were distributed in 565 places in Eastern Denmark, while only 158 places remained in 2019 – a reduction of 72%.

“The data is strong and reveals large numbers that seem worse than in neighboring countries. Many species that were once common and common in Denmark have become rare. And once they leave, they will not come back,” said Professor Hans Henrik Bruun, the main author of the study.

Pearl-bordered fritillary (Boloria euphrosyne). Credit: Emil Blicher Bjerregård

Studies show that decline works in every type of butterfly habitat. These habitats include open woodland, peat bogs, and grasslands.

“Butterflies are a good indicator of the quality of nature. The studied species cannot live in habitats, fertile pastures, or the borders of agricultural fields. They need many natural habitats. There were many such settlements. This is no longer the case,” says Emil Blicher Bjerregård.

Conservation efforts are ineffective

“Most of the butterfly habitats are legally protected and have been for decades. But we don’t see any signs that official site protection – not national or EU’s Natura2000 – has had a positive impact on exotic butterfly species in the last 30 years,” says Hans Henrik Bruun.

According to Bruun and Bjerregård, this is most likely because current conservation efforts are insufficient:

“Legally protected areas are not really well protected from human activities. For example, plantation forests continue to occur in Natura 2000 areas and Danish national parks are “paper parks” with supermarkets and parking lots. At the same time, flowers important to butterflies are rare in natural habitats – partly because farmers are subsidized to graze summer pastures with too much or no forage. In our protected forests, timber production and drainage are causing the destruction of butterfly habitats,” says Emil Blicher Bjerregård, and continues:

“Secondly, Denmark’s protected natural areas are small, parcels of postage stamps isolated, while species require large contiguous natural areas, where populations are less vulnerable to climate and climate change than they are now. Today, for example, they cannot simply fly to a wet area if there is a drought.”

The main solution does not depend on reducing agriculture

Converting more agricultural land is not a priority, as the researchers say:

“Many voices in the public debate argue that the most important thing we can do for biodiversity is to reduce the area of ​​farms. It may be necessary in the long term, but it is very difficult to restore habitats from agricultural land. The most important thing now is to take the areas that are already legally protected and where the species still live and to improve the quality of the habitats by protecting them properly – that is, from all the important threats,” says Hans Henrik Bruun.

This includes activities such as sports management and sports pursuits, as he explains: “Some people may be concerned about whether there is room for horse riding, mountain biking, and hiking. “It is clear that we cannot make areas into wilderness and improve the habitats of rare animals without some people giving up their rights,” says Hans Henrik Bruun.

Emil Blicher Bjerregaard agrees with the ‘cure’: “In Denmark, we had to trade some nature to make a fortune.” I think it’s a good thing. Our situation will never be the same as it was 200 years ago, but there is no reason to lose more than necessary. And now, we are not doing things in the most efficient way. In fact, a lot can be achieved if we do things intelligently,” says Emil Blicher Bjerregård.

Hans Henrik Bruun concludes: “There are no rare animal species that are important to the material well-being of humans. But a world with only two species of butterflies rather than twenty or thirty is duller and poorer. At least, for me. “

Reference: “Rapid and continuous decline in the butterfly area in eastern Denmark 1993-2019” by Emil Blicher Bjerregård, Lars Baastrup-Spohr, Bo Markussen and Hans Henrik Bruun, 22 July 2023, Biological Conservation.
DOI: 10.1016/j.biocon.2023.110208

Sequally of the i the majority threatening

Of the 22 species of butterflies, these seven are among the most endangered in Eastern Denmark:

1. Cranberry blue (Agriades optilete)
2. Mazarine blue (Cyaniris semiargus)
3. Small marbled fritillary (Brenthis has it)
4. Cranberry fritillary (Boloria aquilonaris)
5. Pearl-bordered fritillary (Boloria euphrosyne)
6. High brown fritillary (Fabriciana Adippe)
7. Northern brown argus (Arya Artashashta)

This project started with a bicycle when he was 16 years old

Emil Blicher Bjerregård graduated in biology from the University of Copenhagen in 2023. He began collecting information on rare butterflies with his friend Magnus Vest Hebsgaard as a 16-year-old butterfly enthusiast. The two decided to visit all the butterfly sites in Zealand, Lolland, Falster, Møn, and a few small islands.

With both bicycles and public transport, they visited all these places once a year from 2014 to 2019, collecting data on twenty-two rare butterfly species. With the help of researchers from the Department of Biology and the Department of Mathematical Sciences, the result of the year-long project has now resulted in a scientific article published in the journal Biological Conservation.

Butterflies in Denmark

• There are currently 66 different species of butterflies in Denmark. 37 of them are red listed, endangered or threatened. Since the 1960s, 12 species of butterflies have been lost in Denmark.
• Among Denmark’s most common species: Common Brimstone, Red Admiral, Small Tortoiseshell, and Peacock Butterfly.
• Butterflies make up about 10% of the world’s 180,000 species of butterflies and moths.

About the study

• The study was conducted on 22 site-specific butterfly species, which are relatively rare in Denmark and specialize in habitat types such as open woodland, peat bog, and coastal grassland.
• Data from this study were compared with data from a systematic mapping of the same species between 1989-1993.
• A list of 22 species can be seen in a research article published in the scientific journal Biological Conservation.
• The authors of this article are Emil Blicher Bjerregård, Lars Baastrup-Spohr, and Hans Henrik Bruun.