If murder hornets attack U.S. honey bees, wild bees may serve as critical backup pollinators, Stanford experts say

The Asian giant hornet, also known as the “murder hornet,” isn’t likely to sting a human unless provoked, but its presence in North America could seriously impact access to our food supply. Murder hornets have an appetite for honey bees, which are the most important source of pollination for the majority of our crops. Rebecca Chaplin-Kramer and Eric Lonsdorf, scientists at the Natural Capital Project, study the contributions – such as pollination – that bees provide to people.

Their research focuses on the benefits of wild bees, which are less social than honey bees, to ecosystems and the importance of valuing those contributions so that they may be used to create more sustainable agricultural landscapes.

Below, Chaplin-Kramer and Lonsdorf discuss the threat that murder hornets pose to U.S. honey bees and why it is so important to protect the habitats of more resilient wild bee species in our agricultural lands.

 

Why are bees in North America so vulnerable to the murder hornet?

Chaplin-Kramer: Asian giant hornets are most threatening to social bees – bees that nest together in hives. When a murder hornet enters an Asian honey bee hive, the bees have learned to gather together in a ball-like swarm around the hornet, vibrating their wings to create heat and carbon dioxide until the hornet suffocates. But here in the U.S., our honey bees haven’t adapted the defenses that Asian honey bees have, because they’ve never faced this enemy before. Once a European honey bee hive (which is the type of honey bee we have here in North America) is targeted by an Asian giant hornet, the whole colony is at risk of being destroyed and the bees really don’t have any way to stop it.

Lonsdorf: All bees aren’t equally vulnerable to murder hornets, however. Out of the almost 20,000 bee species in the world, honey bees and bumblebees are some of the only bees that nest in colonies and have workers. Most wild bees are solitary nesters, which makes them less vulnerable to murder hornets. A hornet may still attack a single wild bee, but the impact is much smaller when compared to the loss of an entire honey bee colony.

Solitary wild bees are also less vulnerable to a lot of diseases, like those that contribute to colony collapse disorder. They’re very similar to humans in this way – high population and dense social groups lead to more susceptibility to disease transmission. As we know all too well in the midst of this current pandemic, there are pros and cons to social living, and susceptibility to disease is a big con. For wild bees, their practice of nesting as individuals provides them with added resilience to social threats like the Asian giant hornet.

 

Why is it important to protect bees – both wild and domesticated?

Lonsdorf: Bees are the main pollinators for our crops; without them, our agricultural system would be dramatically different. Seventy percent of our food diversity is dependent on pollination in some way. We’d be eating a lot of tapioca and ground corn without our pollinating bees.

Chaplin-Kramer: If we didn’t have bees, so many of the foods we love to eat – and depend on for nutrition – would be missing from our plates. A striking example is the availability of Vitamin A in our diets, which is a vitamin that’s heavily dependent on pollination. A lot of people are deficient in Vitamin A, and food is the easiest way to deliver that nutrient to them. For much of the developing world, taking vitamin supplements really isn’t a feasible option. To access those vitamins, we need well-pollinated crops.

That’s why protecting wild bee habitats is so critical. For social bees, the murder hornet is just the latest threat to come along, and it won’t be the last. But wild bees can provide a much-needed backup source of pollination when social bee populations are under attack. Wild bees are much harder for people to directly manage because they don’t live in dense colonies, so we probably won’t ever be able to domesticate them like honey bees. But we can manage and support their natural habitats.

 

How do farms use bees in our current agricultural system? Isn’t that working well enough?  

Lonsdorf: It depends on the farm and where you are in the country. In much of California, farmers use bees as a very precise input, similar to other inputs like fertilizer. And honey bees are actually considered livestock by the United States Department of Agriculture. Large-scale farms bring in boxes of honey bees to pollinate an area, then move them along to the next crop when they’re finished. It gets the job done, but it may not be a sustainable strategy for the long term, and it definitely doesn’t factor in the benefits of wild bees. There is a growing movement to make sure that a constant supply of wild bees is embedded in our landscapes, so they can provide that critical pollination backup if and when honey bees are threatened.

Chaplin-Kramer: While they’re resilient in many ways, wild bees are still vulnerable to chemicals. So, we’re making it really difficult for them to survive in a lot of farms because we’re not providing adequate habitat, and then we’re over-spraying the habitat that does exist with pesticides. It’s a fatal one-two punch for wild bees.

 

How can we foster and protect wild bee habitats to get the most out of their crop pollination? 

Londsorf: If you’re managing landscapes and farmlands sustainably, the ecosystem itself provides a permanent “hive” for wild bees. Planting pollinator-friendly habitat in and around farms is the best approach. You don’t need a lot of wild area to support a lot of bees – a little bit goes a long way. I live in Pennsylvania, where we’ve seen a lot of success in farms that incorporate wild areas into their management plans. There’s been such a resurgence of wild bees that Penn State Agriculture Extension often suggests that honey bee hives aren’t needed for pollination on most of the state’s apple farms – there are now enough wild bees here naturally.

Chaplin-Kramer: The kind of progress that Eric describes in Pennsylvania is really exciting to see. Much of those farms in the Northeast U.S. are similar to those in Europe, with hedgerows and other natural elements that act as microhabitats for pollinators. In the more heavily industrialized fields like in the Central Valley of California, it’s a much less hospitable habitat. Agricultural landscapes there are often less diverse and don’t leave much room for “wildness.”

 

What are some steps farmers, policymakers, and conservation organizations can take to protect the habitats of wild bees and restore this natural pollinator backup system?

Lonsdorf: Recognizing the economic and environmental value of wild pollinators is the first step. We need to incorporate the supply of wild bees into our decision-making so that they’re part of the management equation. Then, we can work with farmers to take steps that bring wild bees back onto their lands. Neighboring farmers can work together to plant pollinator-friendly habitats, treating bees as a common pool resource that benefits the group.

Chaplin-Kramer: Incentives are key because there’s a reason that farmers like to keep their fields clear of plants that aren’t their crops. There’s a perception that agricultural weeds and pests come from natural areas on the edges of farms. Farmers are worried about foodborne pathogens and pests that destroy their crops. So, we have to really think about the main goal of agriculture, which is to provide us with healthy food. It’s more than just telling farmers, “keep your fields wild.” We need to give them the tools to promote pollinators and reduce other risks.

 

So, what’s the outlook for the future of murder hornets in North America? Can we do anything as individuals to stop their spread? 

Lonsdorf: It’s important that we’re aware that the murder hornets are here and we have experts actively dealing with them. We need to recognize that their presence isn’t just an issue for the areas where they’re appearing right now, like in Washington State. Hornets don’t pay attention to state lines, so we need to think about it as a management issue nationwide.

Chaplin-Kramer: Citizen science is a really important role that everyone can play. If you see a murder hornet, report it to your state’s Department of Agriculture. That’s how things get caught and managed quickly – people educate themselves and their observations can then help officials act. And, please don’t kill wild bees! There’s been some reaction to the recent murder hornet news coverage that has led people to put out traps that kill all kinds of important flying insects, not just hornets. It’s useful to report an Asian giant hornet if you see one, but let’s leave their management to the experts. Our wild bees are too valuable to risk killing in the crossfire.