Reducing light pollution should be central to the protection of insects, says the professor.
Even weak exposure to light pollution at night prevents growing butterfly larvae from developing into wintering cocoons at the right time, an international team of researchers led by the University of Oulu found in their study.
Light pollution causes individuals to metamorphose into adult butterflies too late in the fall, instead of developing into winter-hardy cocoons.
Many insects use the length of the day to pace their life cycles in relation to the changing of the seasons. The shorter days at the end of summer cause butterflies to go into hibernation.
The short days, which indicate the approaching autumn, make the butterfly caterpillars prepare for wintering as a cocoon. The long days, on the other hand, indicate that the new generation still has time to go through its life cycle before winter. If the days are long or light pollution causes the larvae to mistakenly interpret the days as long, the cocooned individual immediately develops into an adult butterfly.
However, butterflies mistaken for light pollution are unable to reproduce in autumn conditions, and they do not survive the winter.
In research tested how light pollution affects the square meter (Chiasmia clathrata) for the development of larvae into overwintering cocoons. The study also compared populations from urban and rural environments.
The purpose was to find out whether there have been adaptations in urban populations through evolution. The comparison was carried out in both Central Europe and the Nordic countries.
According to the study, butterflies in urban and rural populations react to light pollution in the same way. Thus, urban populations do not seem to have adapted to the light-polluted environment of cities.
Central European populations were more sensitive to light pollution than Nordic populations, which emphasizes the need to reduce the harms of light pollution, especially at more southern latitudes.
However, it is worth noting that light pollution also had a negative effect on Nordic populations, so reducing light pollution is also beneficial for Finnish butterfly populations.
“Light pollution affects nature more and more, and according to our research, it seems that light pollution may also endanger the successful wintering of insects. In the future, it is necessary to investigate how widely insects are susceptible to this kind of adverse effect of light pollution, and to what extent it explains the decline of insects”, academy researcher at the University of Oulu Sami Kivelä says in the announcement.
“Insects living in both urban and rural environments are sensitive to light pollution. Reducing light pollution should be a key priority in insect protection,” says the professor Thomas Merckx from the Free University of Brussels.
In addition to the universities of Oulu and Brussels, the Czech University of Life Sciences in Prague also participated in the study.
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