25 years later - Summary

Jacek Kazimierczak

CEO of Lepidopterra

Today we would like to present the results of last year's research on the number and diversity of butterflies, titled "25 Years Later". For those who haven't had the chance to familiarise themselves with the study, let us explain that the aim was to revisit the same locations at the same time to compare our observations from 25 years ago with the current number and diversity of butterfly species. Although the study was conducted only six times during the season, we can still draw some significant conclusions. We divided the results into two categories: urban and suburban, as we observed different trends in each.

It transpired that urban areas which were suburban 25 years ago have not only seen a decrease in the number of butterflies from 158 to 135 but also a reduction in their diversity by 3 species. Meanwhile, formerly rural areas with mono culture crops such as rapeseed, corn, and rye are now suburban, resulting in improved indicators, particularly the number of butterflies, which increased from 39 to 105. Diversity has also slightly increased by 1 species.

What conclusions can we derive from our research? Firstly, suburban housing estates, despite the prevalence of non-native plants, still serve as excellent habitats for butterflies, especially those areas that have retained their mosaic character. The proximity of old orchards, parks, gardens with native perennial species, remnants of river valleys, and so-called wastelands provide a solid food base for butterflies.

However, the transformation of former urban outskirts into fully urbanised areas with the simultaneous introduction of large quantities of non-native plants and manicured lawns not only leads to a decline in the number of butterflies but also a significant decrease in diversity. Simultaneously, with the process of suburbanisation, areas located further from the city centre are thriving. Former arable fields, particularly mono cultures, transformed into gardens, often planted with nectar-producing plants, become attractive habitats for many species. It's also important to highlight the potential impact of pesticides and herbicides, both in the case of fields with mono culture crops and in manicured urban green spaces.

The conclusion of our spontaneous research after 25 years is, above all, an encouragement to maintain landscape diversity, preserve native vegetation, old migration corridors, and refrain from using plant protection products where unnecessary.

Finally, we believe it would be valuable to highlight which species have not been recorded after 25 years and which have appeared during this time. In urban areas, the absence of the following species has been noted: N.polychloros, N.urticae, P.brassicae, A.levana, I.lathonia, C.argiolus and L.tityrus. New species for urban areas include: N.antiopa, P.aegeria, O.sylvanus, and C.hyale. In the case of former rural areas, the following species have not been recorded: P.brassicae, N.urticae, and L.tityrus. New species include: C.pamphilus, O.sylvanus, and P.napi.

Host plant analysis supports our conclusions. Species typical of old gardens are disappearing from former suburban areas, while larger trees and grasses are thriving. This results in a significant difference in butterfly species diversity. Grasses also begin to dominate in post-cultivated areas, but due to the previously low diversity of butterflies, the difference is not as noticeable. Nonetheless, the species composition of these areas is changing.

25 years later - after overwintering

On April 10, 2023, we conducted our first field visit as part of the „25 years later” series. Read more to see the results.

25 years later

Have you ever wondered if the loss of biodiversity is real or how much we have already lost? Let see how it all changed in Łódź, Poland!

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