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Pollinator populations have experienced dramatic changes

Pollinators have an essential function, helping numerous plants reproduce, and thus maintaining and protecting a variety of ecosystems. Moreover, since scientists estimate that over three quarters of the most important crops depend on pollinators, a loss of these plant visitors would lead to major economic losses. Unfortunately, human-related influences such as changes in climate and land use may negatively affect these essential creatures.

A new study published in the journal Nature Ecology & Evolution  has investigated changes in pollinator populations in the vicinity of Kittilä in Finland (a village located approximately 120 km north of the Arctic Circle). In this region, between 1895 and 1900, forester Frans Silén systematically recorded which insects visited which flowers and how often. Now, the scientists repeated a similar pollinator census at the same place in 2018 and 2019.

The analysis revealed that, although this region remained sparsely populated, with little changes in land use, it has unfortunately not escaped the consequences of climate change, leading to major changes in the types of pollinators present there. 

“We have noticed drastic changes in the networks of pollinators,” said study lead author Leana Zoller, an ecologist at the Martin Luther University Halle-Wittenburg. In fact, only seven percent of the flower visits observed involved the same species of insects and plants as at the end of the 19th century. “That is surprisingly little,” Zoller said.

For instance, hoverflies and moths – which are particularly effective pollinators – appear less frequently on flowers in the area than they previously used to. While these insects have become rarer, the flowers around Kittilä are currently getting considerably more visits from bumblebees and certain flies. 

This aspect concerns the scientists, since there are now considerably fewer insects that are specialists for specific flower shapes. These have been largely replaced by “generalists” such as flies of the genus Thricorps, which visit many different plants. While such generalists are more resilient to environmental changes, they may provide less effective pollination services, since they usually carry the pollen of various other plant species onto a flower.

Although the pollinator network in the region still seems to be working well, this can change in the future if shifts in the insect communities continue. Moreover, while flies in this area seem to be coping quite well with rising temperatures, further north in the Arctic, fly populations are currently dwindling. “If this also happens in our study area, it could become a problem,” Zoller concluded.

By Andrei Ionescu, Staff Writer

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