What is happening to the bees?

As a scientist that studies bees, I am often asked by people I meet – “What is happening to the bees? Is there really a pollination crisis?” Having seen headlines in the news over the past several years people are aware that bees may be in trouble but they usually don’t know why or the extent of the problem.

Generally the bee crisis refers to Colony Collapse Disorder (CCD) which affects honey bees. Honeybees are probably the bee species that most people think of when they think of bees. Honeybees are highly social organisms living in colonies with one queen, many female workers and male drones. Named for their ability to make honey and used widely for pollination, honeybees were one of the first organisms domesticated and are still managed for pollination around the world. In managed (as opposed to wild) colonies, honeybees live in hives that can be moved from place to place depending on which crops need pollination. They are also managed for honey production. Although honey is a delicious treat for humans and other animals, bees make it as the primary food source for their offspring. Honey is made by adult worker bees, from pollen and nectar, that the bees obtain from plants. When visiting flowers to gain these food resources, bees assist plants in reproduction through pollination.

“Honeybee landing on milkthistle02” by Fir0002 – Own work. Licensed under GFDL 1.2 via Wikimedia Commons – https://commons.wikimedia.org/wiki/File:Honeybee_landing_on_milkthistle02.jpg#mediaviewer/File:Honeybee_landing_on_milkthistle02.jpg

Many plants that humans use as food sources and for other products require pollination assistance from animals. Insects, especially bees, are the most important animal pollinators. Dr. Alexandra-Maria Klein and colleagues estimated that 70% of the main crops used by humans globally are dependent on insect pollination. Another study by Dr. Gallai and colleagues found that all pollination services from animals worldwide is worth an estimated €153 billion (~$177 billion). In other words, in 2005, almost 10% of the total economic value of all global food production came from pollination services. More importantly than just the economic value, without bees and other pollinators we would have few fruits and vegetables. Imagine a world with no apples, cherries, grapes, onions, eggplants or broccoli! And these are just a few of my favorites; there are many other foods that require insect pollination.

Image from Whole Foods: https://media.wholefoodsmarket.com/news/bees


And this is why people are so concerned about Colony Collapse Disorder (CCD). Due to CCD, many beekeepers in the US found that they were losing large numbers of bees, essentially whole hives, over winter. Although some losses over winter are normal, in these cases the losses were extremely high and often no bee bodies were present, adding to the mystery. Such extreme losses of honeybees, the primary managed pollinator in the United States (and globally), are scary because they could lead to a pollination crisis where there are not enough managed bees to meet the pollination needs of farms. The causes of CCD are still not completely understood but parasites and disease (or some combination of both) are likely at fault with other stressors related to the management of hives, the management of farms and environmental changes being other possible contributory factors.

Although CCD may be in decline for now (although this is also debated), it has increased public awareness of how vulnerable we are to a loss of pollinators. Bees are integral to our global food system and have great economic value. However, honeybees, are just one species of bee. In fact, there are over 20,000 species of bees worldwide, with estimates by bee expert Dr. John Ascher of around 400 bee species in New Jersey alone. People may be familiar with bumblebees, sweat bees and carpenter bees, but there are many other bee species that people have never heard of, some of which may look very different than you would expect (click here to see some amazing photos by Sam Droege as featured in National Geographic).


“Bumblebee 05” by I, Tony Wills. Licensed under CC BY-SA 3.0 via Wikimedia Commons – https://commons.wikimedia.org/wiki/File:Bumblebee_05.JPG#mediaviewer/File:Bumblebee_05.JPG
“Iridescent.green.sweat.bee1”. Licensed under Public Domain via Wikimedia Commons – https://commons.wikimedia.org/wiki/File:Iridescent.green.sweat.bee1.jpg#mediaviewer/File:Iridescent.green.sweat.bee1.jpg
“Carpenter bee” by Daniel Schwen – Own work. Licensed under CC BY-SA 4.0 via Wikimedia Commons – https://commons.wikimedia.org/wiki/File:Carpenter_bee.jpg#mediaviewer/File:Carpenter_bee.jpg

Although many species of bees globally are social, most bee species, especially those in the US, are solitary, meaning that just one female bee raises her young alone instead of cooperatively with other adult bees. These wild solitary bees live in holes in wood as well as in the ground and are important pollinators of both crops and wildflowers. In fact honeybees are not the best pollinators for all crops, as some plants have evolved with insects that are specialized to pollinate that plant. A recent study by Dr. Lucas Garibaldi and colleagues found that wild bees increased production in crops regardless of whether honeybees were present. The same study found that honeybees and wild bees are complementary in their pollination efforts meaning that the presence of one does not substitute for the presence of another. This research is part of an increased effort to learn more about how wild, unmanaged, pollinators benefit crops and other plants.

Although CCD is a significant threat to managed honeybees, it is just one of the many threats facing all wild insect pollinators. Insect pollinators, like other animals, are at risk from many different, often human-caused threats, including loss of habitat, pollution, and climate change. Scientists are increasingly trying to understand how bee diversity relates to pollination services and what environmental and human factors are influencing the health of bee species worldwide. Such research will help in efforts to protect and restore bee populations to agricultural and natural ecosystems.   Small personal efforts to support wild pollinators are also important. For example, I advocate for planting flowers that are local to ecosystems near your home or business as well as reducing pesticide usage.

For more information on ways you can support pollinators, here are a few websites:

Great Pollinator Project: https://greatpollinatorproject.org

The Xerces Society: https://www.xerces.org/pollinator-resource-center/

Additional information about Colony Collapse Disorder and honey bees can be found at https://www.ars.usda.gov/News/docs.htm?docid=15572.

Studies mentioned in the text:

Gallai, N, J-M Salles, J Settele & BE Vaissière. 2009. Economic valuation of the vulnerability of world agriculture confronted with pollinator decline. Ecological Economics 68: 810-821. https://www.sciencedirect.com/science/article/pii/S0921800908002942

Garibaldi, LA, I Steff-Dewenter, R Winfree, MA Aizen, R Bommarco, SA Cunningham, C Kremen, LG Carvalheiro, LD Harder, O Afik, I Bartomeus, F Benjamin, V Boreux, D Cariveau, NP Chacoff, JH Dudenhöffer, BM Freitas, J Ghazoul, S Greenleaf, J Hipólito, A Holzschuh, B Howlett, R Isaacs, SK Javorek, CM Kennedy, K Krewenka, S Kirshnan, Y Mandelik, MM Mayfield, I Motzke, T Munyuli, BA Nault, M Otieno, J Peterson, G Pisanty, SG Potts, R Rader, TH Ricketts, M Rundlöf, CL Seymour, C Schüepp, H Szengyögyi, H Taki, T Tscharntke, CH Vergara, BF Viana, TC Wanger, C Westphal, N Williams & A-M Klein. 2013. Wild pollinators enhance fruit set of crops regardless of honey bee abundance. Science 339: 1608-1611. https://www.sciencemag.org/content/339/6127/1608.abstract?sid=1425a326-217a-4b6a-b9f0-1faa960b8d9c

Klein, A-M, BE Vaissière, JH Cane, I Steffan-Dewenter, SA Cunningham, C Kremen & T Tscharntke. 2007. Importance of pollinators in changing landscapes for world crops. Proceedings of Royal Society B 274: 303-313. https://rspb.royalsocietypublishing.org/content/274/1608/303.short