Linn Anette Haug and about 40 other citizen scientists have spent parts of their summer investigating the status of the Norwegian bumblebee population.
Linn Anette Haug is a secondary school teacher by day. Every summer for ten years, she has been out helping researchers map insects in Eastern Norway. "I love all insects, but there's something special about bumblebees," she says.(Photo: Private)
Many bumblebees have had their habitats dramatically reduced south of Scandinavia. This is shown in a study published in the journal Nature.
Belgian researchers found that European bumblebee populations have experienced a sharp decline over the last century.
By 2080, researchers believe that many bumblebee species in Europe could lose large portions of their habitat.
In Norway, too, there is growing concern about the fate of bumblebees.
But according to the Belgian researchers, it is to Norway and Scandinavia that the bumblebees will be heading in the future.
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Bumblebees need flowers to thrive.(Photo: Ola Moen)
React to environmental changes
Norwegian bumblebee researchers find it very exciting to follow this development.
So, how are the bumblebees actually doing in Norway?
A total of 27,000 different species have been recorded by the national monitoring programme run by the Norwegian Institute for Nature Research (NINA).
But for certain species, like bumblebees, NINA has a dedicated monitoring effort.
That’s because bumblebees are especially quick to respond to environmental changes.
Expanding the monitoring
Every year, researchers at NINA work closely with Sabima on a citizen science project.
For the past 11 years, Sabima has coordinated about 40 volunteers who head out into the field to gather data on bumblebees and other insects. They do this three times over the course of the summer.
A citizen scientist heading out to search for insects needs to bring the right equipment.(Photo: Ola Moen)
Kristoffer Bøhn from Sabima leads the team of volunteers. He explains that there are many people out there with extensive knowledge of bumblebees and other insects.
In addition to their own expertise, volunteers also receive training in species identification and are given updated handbooks they can bring into the field.
"They’re also trained in a standardised method, where they follow the same route three times throughout the season," he says.
The data collected helps researchers track changes in insect populations over time.
So far, bumblebee populations have been monitored in Eastern Norway, Southern Norway, Western Norway, and Trøndelag.
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This year, the project has expanded to Northern Norway as well.
"We’ve had great success recruiting volunteers up there too," says Bøhn.
What do they find?
The trends in bumblebee populations are complex, says Jostein Gohli, who is responsible for the 2024 report summarising the monitoring results.
"The patterns vary across regions," he says.
In Trøndelag, researchers have seen a steady decline in bumblebee numbers during the monitoring period.
In Eastern Norway, numbers initially dropped but later began to rise again.
Are there any bumblebees here? For the third year, Ola Moen, who works as a state pilot by day, is out looking for bumblebees and butterflies in Western Norway. "I've always been interested in nature. It started with birds, and then one thing led to another," he says.(Photo: Ola Moen)
Southern Norway shows the opposite pattern: an increase followed by a decline. However, this trend is less pronounced than what’s seen in Eastern Norway.
In Western Norway, the project only started in 2022. It is therefore too early to say anything about population trends there, he says.
Flowers are very important
One of the biggest challenges for bumblebees, and insects in general, is the loss of areas where they can live and find food, says Gohli.
The number of flowers in an area is a key factor in whether bumblebees can thrive and survive.
When flowers are plentiful, there tend to be more bumblebees and a greater diversity of species.
In Trøndelag, the amount of flowers initially increased during the data collection period, but this increase stabilised midway through.
In Southern and Eastern Norway, flower coverage first declined, then rose again.
Bumblebees must be caught in a jar before Ola Moen can be sure what species they are.(Photo: Ola Moen)
"We want to study whether the availability of habitats and changes in land use can explain the patterns we see in the bumblebee monitoring," says Gohli.
In general, researchers know that widespread development and construction are major drivers of biodiversity loss.
What was it like 100 years ago?
There’s something that frustrates the researchers working on this monitoring project.
"We know little about how many bumblebees and which species existed in Norway a long time ago, before human impact on nature became as significant as it is today," says Gohli. "We would really like to know what things were like when nature was more untouched and pesticides were used less."
Although they now have good data on populations, it only covers a short timeframe.
Jostein Gohli wishes we knew how many insects existed back when nature was untouched and pesticides were rarely used.(Photo: NINA)
"We're observing changes, but we know that the starting point – that is, the populations at the beginning of our time series – is unlikely to reflect what things looked like before human impact," he says.
Insects are heavily affected by climate.
"And I'm not talking about climate change, but climate variation. If we get a cold spring or a cold summer, we see far fewer insects. It's important that we take this into account in our analyses," says Gohli.
More butterflies
Butterflies are also being closely monitored in Norway.
Here, there has actually been an increase from 2011 and throughout the entire observation period. This seems to apply to all three regions studied, says Gohli.
"This suggests that different factors are affecting bumblebees and butterflies. But it's risky to draw strong conclusions from short-term data. We have to consider all possible explanations," he says.
Why action matters
European studies looking at overall insect trends show that total insect biomass has dropped dramatically in recent decades.
"That's not surprising. All animals need a suitable place to live. When the habitats they depend on disappear, it's only natural that insect numbers go down," says Gohli.
So far, Norway’s monitoring doesn’t show a clear trend of either growth or decline in bumblebee populations.
The fact that flower cover is so important suggests that it's still possible to reverse the trend if habitats are preserved, says Gohli.
There is growing awareness of how important roadsides are for biodiversity. This could have a significant impact on how insect populations fare, says researcher.(Photo: Ola Moen)
He points to large-scale efforts, like the Norwegian Public Roads Administration’s recent focus on managing roadside areas and green spaces to support biodiversity. These areas can be crucial for species like bumblebees and butterflies.
"And the fact that more people are now letting parts of their private gardens grow wild probably contributes in a positive way as well," he adds.
More bumblebee species expected in Norway
As Norway's climate grows milder and southern Europe becomes too warm, several new bumblebee species are likely to move north.
The Norwegian Biodiversity Information Centre predicts that four new species could establish themselves in Norway in the coming years. These are the vestal cuckoo bumblebee (Bombus vestalis), the golden bumblebee (Bombus schrenki), Barbut's cuckoo-bee (Bombus barbutellus), and the sand bumblebee (Bombus veteranus).
The vestal cuckoo bumblebee is already widespread in Finland, Denmark, and Sweden.
Sand bumblebees are found in our neighbouring countries. This one is from Finland. Will we soon see it in Norway?(Photo: Norwegian Biodiversity Information Centre / Pekka Malinen CC BY 4)
The golden bumblebee has spread from Russia and the Baltics to Finland.
Barbut's cuckoo-bee is widespread in Europe and was first spotted in southern Sweden during the 1970s. It is expected to soon arrive in Norway.
The sand bumblebee can be found in Denmark, Finland, and Sweden.
"None of these bumblebees have been detected in Norway yet," Frode Ødegaard tells Science Norway. He is a senior researcher at NINA.
Ghisbain et al. 'Projected decline in European bumblebee populations in the twenty-first century', Nature, 2023. DOI: 10.1038/s41586-023-06471-0 (Abstract)
