Wednesday, June 12, 2013

Loss of Honeybee Biodiversity: What is Killing Them?

Loss of Honeybee Biodiversity: What is Killing Them?
By Daniel Straub

A recent TED conversation and trip to the University of Oregon’s Urban Farm made me aware of an alarming fact, and I must believe many others, were not yet aware of. This is the fact that bees are dying at a terrifying rate. This got me extremely interested in what exactly this was and why it is happening. Colonies of bees are suffering from what is called Colony Collapse Disorder (CCD).  CCD was first noticed in 2006 when beekeepers observed a disappearance of their worker honeybees that would later be found dead, or most often, not at all (Walsh 2013, Kaplan 2013). CCD can result in the loss of 30-90 percent of a particular colony dying (Kaplan 2013). Honeybees are extremely vital to our agriculture. They are responsible for about one third of pollination in the United States agriculture business; pollinating a lot of good and healthy food such as apples, melons, onions, almonds, and broccoli to name a few (Holland 2013). What is also truly scary, is the fact that no one knows what is causing CCD to happen. However, over the past few years, through research, a few ideas have come to the forefront on what might be causing CCD. In this blog post I intend to summarize my findings from what is available and causing this devastating destruction to our bees.

Figure 1: Typical Honey Bee (Apis Mellifera)
Photo Credit: John Kimbler. National Geographic
Through researching many articles it seems that a very talked about cause of CCD is the use of pesticides, specifically, the neonicotinoid family. I should say this is talked about for most people in the scientific community however, not the US government (Ullrich 2013, Kaplan 2013). In a recent study, experimenters exposed honeybees to what is thought to be the leading culprit, neonicotinoid pesticides. They found that not only did the honeybees that were exposed to the pesticides have higher mortality rates but that their memory and learning abilities were also impacted, compared to those not exposed (Williamson and Wright. 2013). Honeybees must perform very elaborate behaviors for finding food and for signaling the other bees of the colony where the food is. If their learning and memory is affected by these pesticides then not only is the individual at risk, the whole colony could be at risk as well. Another study also found that bees exposed to neonicotinoids were more easily infected with the gut parasite Nosema (Holland 2013). The European Union has implemented a two-year ban on such neonicotinoids to investigate the pesticide and its effects. While it took a lawsuit filed against the EPA to accelerate its research into this category of pesticides (Walsh 2013, Holland 2013).

Figure 2: Farmers with Insufficient Bee Coverage on Hive from CCD
Photo Credit: vanEnglesdorp et al. 2009. PLoS ONE 
Another highly investigated topic is the role of pathogens and parasites in CCD (vanEnglesdorp et al. 2009, Kaplan 2013 and Walsh 2013). Dennis vanEnglesdorp (who gave the below TED talk) and his team of experimenters conducted a study where they looked at the virus load (amount of viruses present) of different hives that were experiencing CCD and compared those to control hives that did not experience CCD. What they found was that the bees that had experienced the CCD had higher amounts of virus loads, particularly the parasite Nosema spp. (a parasitic fungus) and Israeli Acute Paralysis Virus (a deadly virus)  (vanEnglesdorp et al. 2009).  The study found, and the USDA agrees, that there is no specific pathogen or parasite that was found with enough frequency to be the specific cause of CCD. The study goes on to state that pathogens play a crucial but secondary role in CCD, finding the primary factor is the holy grail. They believe that the higher viral loads and the co-infection with other disease agents (i.e. Nosema and Israeli Acute Paralysis Virus) seen in the CCD hives shows that this is something that cannot be ignored. The study along with the USDA states the lack of knowledge in this area and the further need for research. Since this study, not much more has been found that widely differs from this in role of pathogens and parasites other than the parasite, Varroa mites, which also have been known about for sometime (Comman et al. 2012). Not much is known yet about these mites, which are found in the honeybee hives and may play a role in CCD and which little is known and like the other pathogens/parasites, more investigation is needed (Kaplan 2013). 

A study that I found extremely interesting that related to the class was a study about the microbes that are associated with honeybee CCD (Cox-Foster et al. 2007).  The study looked at the bacteria that were found on honeybees over a three-year period. They looked at hives that had been affect with CCD and used those that had not been affected by CCD as the control. The study found that the bacteria that were found on the CCD hive and the non-CCD hives differed (Figure 3). Also, they found that the non-CCD hives had higher amounts of new bacteria that were not present at the beginning of the experiment (Figure 3). This led the researchers to the conclusion that the different bacteria and different amounts of bacteria found on the non-CCD were doing something to protect them from diseases that the CCD colonies were unable to do. The CCD colonies were found to have high amounts of Israeli Acute Paralysis Virus.
Figure 3: Different Bacteria Found On Bees
Photo Credit: Cox-Foster et al. 2007. Science 
The USDA and National Geographic articles also bring up the new stressors that the honeybees now face as a factor of CCD. The USDA breaks the stressors into two categories. First, is management stressors; these are caused by poor-nutrition due to overcrowding and new migratory stressors they now face. The second is environmental stressors; these are caused by lack of diversity of pollen/nectar, availability of pollen/nectar and the availability water. All of these could be factors that have a role in CCD and in which there is little knowledge of how these stressors may affect honeybees.

From what I have found, this seems to be where the current state of the troubled honeybee is. Still, colonies are collapsing and still we do not know why. The one bright spot seems to be that this issue is gaining momentum. Though we still do not know why this is happening to the bees, it appears there is a narrowing of ideas and researchers are targeting specific areas. From certain reoccurring pathogens and parasite to a family of pesticides to the bee’s own microbiom, it seems that research is heading in the right direction. However, more still needs to be done. The importance of bees cannot be understated, as I have recently learned. Bees are vital for agriculture, being responsible for pollinating one third of crops, valued at 200 billion dollars (Walsh 2013). This problem is not only one seen blaring here in the United States but the disappearing of honey bees is happening globally as well, further adding to the importance (Holland 2013). Good ideas for the future have been put forth like the urban beehives as we have discussed. But to me this does not fix the problem at hand. It seems paramount that we figure out what is causing CCD so we can save future honeybee generations and our food.

Video: Dennis vanEngelsdorp Ted Talk. Good Summary About The Plea For Bees

Primary Literature

Cox-Foster, Dianna, S. Conlan, E. Holmes, G. Palacios, J. Evans, N. Moran, P. Quan, T. Briese, M. Hornig, D. Geiser, V. Martinson, D. vanEngelsdorp, A. Kalkstein, A. Drysdale, J. Hui, J. Zhai, L. Cui, S. Hutchison, J. Simons, M. Egholm, J. Pettis, W. Lipkin. A Metgenomic Survey of Microbes in Honey Bee Colony Collapse Disorder. Science. (2007) 10. (1126). 283-284.

Williamson, Sally, G. Wright. Exposure to multiple cholinergic pesticides impairs olfactory leaning and memory in honeybees. The Journal of Experimental Biology. (2013) 216 (10). 1799-1821.

vanEngelsdorp, Dennis, J. Evans, C. Saegerman, C. Mullin, E. Haubruge, B. Nguyen, M. Frazier, J. Frazier, D. Cox-Foster, Y. Chen, R. Underwood, D. Tarpy, J. Pettis. Colony Collapse Disorder: A Descriptive Study. PLoS ONE. (2009). 4(8) e6481

Comman, Scott, D. Tardy, Y. Chen, L. Jefferys, D. Lopez, J. Pettis, D. vanEngelsdorp, J. Evans. Pathogen Webs in Collapsing Honey Bee Colonies. PLoS ONE. (2012). 7(8) e43562

 Popular Media

Walsh, Brian. Beepocalypse Redux: Honeybees Are Still Dying-and We Still Don’t Know Why. Time. May 07, 2013.

Holland, Jennifer. The Plight of the Honeybee: Billions of dollars-and a way of life-ride on saving pollinators. National Geographic. May 10, 2013.

Ullrich, Christy. Are Honeybees Losing Their Way? National Geographic. February 13, 2013.

Kaplan, John. Honeybees and Colony Collapse Disorder. United States Department of Agriculture (Agriculture Research Division). 2013.