One of the last Franklin’s bumble bees pollinates a composite flower.
Photo by James P. Strange, USDA-ARS Pollinating Insect Research Unit (PD USDA ARS)
How often do you think about fuzzy bumble bees? For a long time, we’ve been able to take them for granted, we haven’t needed to consider them when we make decisions or plant gardens, but things are changing. Bee populations are plummeting and many bumble bees could soon be facing extinction. For one of our precious pollinators, it may even be too late.
The Franklin’s bumble bee (Bombus franklini) possibly has the most restricted range of any Bombus, and this year it was designated as an endangered species by the United States Fish and Wildlife Service (1). It has been listed as critically endangered by International Union for Conservation of Nature (IUCN) Red List since 2008 (2). Bombus franklini was once not an uncommon sight in its tiny range in Southern Oregon and Northern California. When Robbin Thorp, professor emeritus of entomology at the University of California Davis, started surveying the populations of Franklin’s bumble bee in 1998, he found several dozen of the bees. Over the next few years, the Franklin’s population declined steeply. There were no sightings in 2004 or 2005, according to IUCN. One day in 2006, Thorp found one. The species was never seen again. That August day, as he watched the large fuzzy, yellow and black, bee pollinate the flowers of Sulfur Buckwheat (Eriogonum umbellatum), Thorp likely saw the last Franklin’s bumble bee that would ever be observed. Thorp continued searching for the rest of his life, but to no avail.
The sudden demise of the Franklin’s bumble bee is blamed in large part on the virus Nosema bombi, which is suspected to have been introduced into the US in the 1990s through the transportation of bumble bees between the US and the EU. Nosema bombi is thought to have also decimated the Franklin’s sister species, Bombus occidentalis, the Western bumble bee along with several others.
The Franklin’s was not the only bumble bee to have its population collapse in recent years. “The rusty patched bumble bee has declined by 87 percent in the last 20 years. The species is likely to be present in only 0.1% of its historical range,” says the US Fish and Wildlife Service, which declared the species endangered in 2017 (3). IUCN listed it as critically endangered in 2015. “Our analysis found B. affinis has exhibited a 92.54% relative abundance decline over the past decade,” notes IUCN. Habitat loss/fragmentation, pesticides, and climate change are all blamed for their decline.
After a 90% decline and its disappearance from many US states, another bee, the American bumble bee (Bombus pensylvanicus) may soon be added to the endangered species list (4). Cameron et al. found that, like B. franklini, Bombus pensylvanicus is susceptible to Nosema bombi. Habitat loss and fragmentation are also likely culprits.
With each bee lost, we lose not only a unique and irreplaceable species, but also one of the pollinators on which human civilization depends. We can no longer rely on the non-native honey bee (Apis mellifera) to support our crops and wild plants, as many of their colonies have been obliterated in recent years by a mysterious illness known as Colony Collapse Disorder (CCD). Pesticides and, to a lesser extent, varroa mites (Varroa destructor) have also damaged honey bee populations.
These problems have highlighted the fact that balancing human society on a single non-native species is very dangerous. If honey bees are wiped out and our wild pollinators are not taken care of, human civilization could collapse. Food production would plummet, prices would skyrocket, and many people would starve. That is why we mustn’t turn a blind eye to these pollinators’ plight. Sadly, solitary native bees (which make up most of our native pollinators) are very understudied, but for the most part, the threats to bees outlined here apply to them as well as to social bees.
Pesticides are one reason for our pollinators’ decline. According to Cornell University, studies have found that neonicotinoids (one of the most common and most toxic pesticide classes in use today) can cause increased mortality, reduced colony growth, reduced brood production, reduced nest construction, and impaired feeding in bumble bees.
Habitat loss and fragmentation are also quite problematic. It is thought that habitat fragmentation can isolate populations and deplete gene pools. Habitat loss can reduce and eliminate populations altogether.
Introduced parasites and diseases, like the Nosema bombi that may have wiped out the Franklin’s bumble bee, can also be very problematic. The declining populations of the Western bumble bee and the American bumble bee have been shown to be more heavily infected with N. bombi than stable species (5).
Though their situation seems quite hopeless, there are still glimmers of light for them. As of now, there is no reasonable way to fight N. bombi infection. However, pesticide use is not so difficult to deal with. According to the Environmental Protection Agency, 14 million pounds of insecticides were used in the “Home & Garden” sector in 2012 alone (6) This is very detrimental to native bees, as well as honey bees. Simply eliminating pesticide use in your own yard can help save our pollinators. If you use a lawn care company, they are likely treating your yard with insecticides, despite many companies claims that they are environmentally responsible. It is a good idea to contact them about whether they use pesticides, especially because many of the most common chemicals are highly toxic and carcinogenic (7).
How do we fight habitat loss? It seems like such a huge issue to confront, but one of the biggest ways you can help is very simple and easy: plant native! Native plants support many more pollinators than non-natives. Many non-natives are also cultivars bred for beauty that have lost their ability to supply nectar to our bees. By planting native, we can stitch back together the fragmented habitats of isolated nature preserves in our human-dominated world. As renowned Entomologist Douglas Tallamy says, if we all pitch in, we can create a “Home Grown National Park”. By planting natives, we can ensure a better future for pollinators as well as beautiful gardens!
In my garden, I have implemented the use of native plants and elimination of pesticides. Within a year, American bumble bees were regularly visiting! This summer, the garden was full of them at all times. I have also recorded 27 other bee species in our yard, many of which are year-round residents.
An American bumble bee visits a Liatris bloom in our yard.
Photo by Brice Claypoole
Bees have an amazing ability to bounce back when given an opportunity. Despite the dire situation of our native bees, we cannot give up on them. We must adapt so that bees and humans can thrive.
Maybe it’s not time to give up on the Franklin’s bumble bee, either. As an article by National Geographic notes, the Wallace’s Giant bee (Megachile pluto, the world’s largest bee) was lost for over a century before being rediscovered. It hasn’t even been 20 years for the Franklin’s, and surveys of their former range are still conducted every year in the hope that a colony might still exist, deep in the Oregon mountains.
4 Cameron, S.A., Lozier, J.D., Strange, J.P, Koch, J.B., Cordes, N., Solter, L.F. and Griswold, T.L. 2011. Patterns of widespread decline in North American bumble bees. Proceedings of the National Academy of Science (USA) 108(2): 662-667. https://www.pnas.org/content/108/2/662
5 Cameron, S.A., Lozier, J.D., Strange, J.P, Koch, J.B., Cordes, N., Solter, L.F. and Griswold, T.L. 2011. Patterns of widespread decline in North American bumble bees. Proceedings of the National Academy of Science (USA) 108(2): 662-667. https://www.pnas.org/content/108/2/662