One-third of the food we eat relies on bee-pollinated crops. But in Europe, at least 23% of bee species are in decline.
“What happens to pollinators could have huge knock-on effects for humanity,” says Professor Lynn Dicks from the Department of Zoology. “These small creatures play central roles in the world’s ecosystems, including many that humans and other animals rely on for nutrition. If they go, we may be in serious trouble.”
Help is coming. Mark Brown, Professor of Evolutionary Biology and Ecology, is the new Director of the Museum of Zoology. Mark looks at the reasons behind pollinator decline. The story is a complex one, where pollinators are beset by stressors: emerging diseases, pesticides, disappearing habitats and parasites.
Mark has spent 28 years tracking this story, from Zürich to Dublin, then London and now to Cambridge. His teams have quantified the harmful chemicals that wild bees are exposed to and produced the world’s first regional IUCN Red List for bees – allowing for detailed plans on how to preserve pollinators in the UK.
In rearing bee colonies in his lab, Mark puts his life on the line: “I’m actually allergic to bumblebee stings, so I have to be super careful. I became allergic through working with them and getting stung so many times. If I was stung now and didn’t receive treatment, I’d die.”
To reverse pollinator decline, we need to entwine our lives with the behaviour of these species. Mark, alongside a growing cadre of pollinator researchers at Cambridge, can point the way.
The stressful life of bees
Bees, ants, wasps and termites are special kinds of insects. Biologists sometimes call them ‘eusocial’, to reflect their complex social dynamics. They have specialised roles for individuals, with some members devoted to breeding, while others gather food.
Social insect biologists are still debating the efficiencies of these roles. They create colonies in the lab to test the strengths of different make-ups – where every ant is a worker, for instance – and compare them to each other. Zoology’s Duygu Sevilgen is doing the same with corals, in measuring how lab-grown colonies respond to varying ocean environments.
Likewise, keeping bee colonies in the lab allows Mark to vary the environment and measure how the hive reacts. Mark says, “If you think of a colony as a superorganism, it opens up some fascinating possibilities. We couldn’t take a human, break up their cells, and put them back together in different ways to see how they work. But you can do that with social insect colonies.”
Coupled with bees collected in the wild, Mark can build a picture of how bee populations respond to threats. At sites across Europe, Mark and his collaborators measure environmental toxins, climate data and the number of flowers in a given area, to build a picture of the resources available to bee colonies.
Mark says, “We take all of that information and do some heavy statistical crunching. We come out with a clear picture of what is the main driver of bee decline, and how that varies across space.”
Pesticides driving bee decline
Mark’s team found that pesticides are still a key driver of bee population decline, despite measures being taken to limit the chemicals’ spread. These findings highlight the difficulty in assessing agricultural chemicals: until they are unleashed in the real world, we can’t always foresee how an ecosystem will respond.
In addition to pesticides, Mark’s team identified the potential for pathogens to spillover from managed honeybees to wild bumblebees – something like bee COVID – and ways to stop this from happening. “We need to work with beekeepers to make sure they have the tools and training to keep beehives as healthy as possible,” Mark says. When trying to control the spread of diseases, Mark recommends buffer zones around protected areas that support wild bees, or other measures to prevent spillover.
We can take comfort in wider Cambridge research uncovering bees’ ability to combat disease. Biochemistry’s Dr Eyal Maori has found a new form of social immunity in honeybees, where individuals can share anti-viral RNA with each other. In this way, information on how to fight diseases can spread rapidly across the colony.
To ensure the latest research is put to use in the real world, Mark lobbies policymakers across Europe, letting them know the best ways that we can allow pollinators to recover. “Seeing real-world positive impacts as a result of this work is enormously satisfying,” Mark says. “To make a reliably good change sometimes takes decades, but it’s worth it.”
Using ‘natural pharmacies’ to fight parasites
The degradation of the natural world also affects the delicate balance between bees and their parasites.
Bumblebees have an annual lifecycle. The bigger bumblebees we see in spring are queens freshly out of hibernation (a sleepy state where queens slow their metabolic rate by 99%, and can breathe underwater if their home floods). Queens emerge from slumber ready to start a new colony.
But there’s a catch, Mark says: “If a queen is infected with a particular parasite when she enters hibernation, she’ll produce 40% fewer queens and males in the next colony. For social insects like bees, there’s a huge cost to being parasitised.”
Bumblebees’ most common parasite is a trypanosome. It’s been co-evolving with bees for millions of years, with the parasite trying to exploit the bee, while the bee adapts its defences. Bees catch it when drinking nectar that’s been visited by other infected bees, who leave their poo on the flowers. The parasites then swim through the bee’s stomach and embed themselves in their gut wall.
Bees’ unusual defence mechanism
Mark has first-hand experience in collecting parasitised samples. “Bumblebees use their poo as a defence mechanism,” he says. “When you come towards the nest, many of them lie on their back and shoot their poo at you. I’ve been in the line of fire more times than I care to admit.”
Where floral resources are abundant, bees can use the environment as a ‘natural pharmacy’ – weakening their parasites with chemicals found in nectar and pollen. “There’s a chemical found in heather that stops bees getting infected by the parasite,” Mark explains. “It causes the parasite to lose its tail, meaning it can’t embed in bee guts.”
Land-use change, driven by intensive agriculture and urbanisation, has dramatically reduced the natural resources that bees can call upon to fight their parasites. In the UK, 80% of lowland heaths have vanished, meaning many bees have lost that method of parasite control.
The key to restoration efforts
Mark thinks this is replicated elsewhere: that many flowering plants with antimicrobial benefits to bees and other pollinators are no longer available. These insights are crucial for future restoration efforts, which can aim to rebuild such ‘natural pharmacies’. Mark warns, “We need to give bees their full range of defensive options, which they had access to before we simplified the landscape.”
Here, Mark’s role as Director of the Museum of Zoology comes to the fore. “When it comes to biodiversity, the Museum’s collections underpin our understanding of what the world was like, and what we can aim for the world to be again,” Mark says. “The more museum collections are used in this way, the more important they become.”
Mark is keen for future exhibitions to directly link to current research being done at the Museum, and the wider University. He’ll also reinforce the invitation to people from all over the world to use its collections for their work.
“We want to interrogate our collections, and work together with the communities who collected them, and from whose lands they were collected. I want to remove all barriers to access, and encourage people who’ve never been to a university museum before to visit. We want to make our collections accessible to all, and welcome people from all parts of society.”
This article from the University of Cambridge is republished under a Creative Commons licence (CC BY-NC-SA 4.0). Read the original here.
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