Thursday, October 13, 2016

For the Love of Bees



            There’s something inspiring about the work ethic of bees, something artistic in their design and something magical about their existence.  Perhaps that’s why the bee has permeated our society in a way that no other creature has. From our art to our food, bees have become a part of our culture.  In fact, it seems that we’ve always intuitively sensed our deep connection to bees. Now, however, science is proving that our connection goes much deeper than we might have thought. That, for better or worse, our species have become irreversibly connected.

For Better or Worse:
           
For most humans, our connection to bees has been for the better. Bees are pollinators, which means that they help to move pollen around, aiding in the fertilization of many plants. Of course, fertilization allows for the continued lifecycle of a plant, making pollination an essential part of our food system. In fact, a Cornell University study (Ramanujan, 2012) estimated the value of the U.S. honey bee pollination at around $12.6 billion for “directly dependent crops” such as apples and $6.8 billion for “indirectly dependent crops” such as alfalfa.  Other insects and bees such as bumble bees were valued at around $4 billion for directly dependent crops and $5.9 billion for indirectly dependent crops. But, while bees have often provided us with a relationship that is for the better, sometimes their ties to us are for the worse.

It’s All About Chemistry:

            There’s a famous incident in which a royal beekeeper wrote that “bees are exquisite chemists.” He certainly had a point, but it is really the impact of human chemistry that has many people concerned about the future health of bees. Today, the internet is swarming with news stories about the negative relationship between the bee population and the use of pesticides. There is a lot of debate about what bees are impacted and what chemicals are impacting them, but at this point there does seem to be evidence that some of these chemicals are having a negative impact on bee population.
            While studies investigating these impacts are taking place all around the world, UW-Madison graduate Dr. Rachel Mallinger has been at the forefront. Though she is currently completing post doctorate work outside of Wisconsin, her graduate research showcased the challenges that native bees are facing.

Native Bees:
           
            So what’s a native bee you might ask?  Native bees, which include bumble bees and sweat bees among others, are called native bees, because, well, they are native to the United States.  While honey bees are absolutely amazing (and so well loved that they will be covered in their very own Curious Columnist post on Sunday), they are not actually native to the United States. In fact, honey bees are thought to have been brought here in the early 1600s by European settlers. There are currently seven species of honey bees recognized around the world, but native bees are much more pervasive with more than 500 species present in Wisconsin alone. With such great numbers, there’s no denying that these native bees contribute a great deal to our ecosystem. Unfortunately, while native bees have been good to us, our practices haven’t always been good to them.

Pesticide Pollution:

Though honey bees are most commonly associated with the negative impact of pesticides, Dr. Mallinger was fascinated by the diversity of bees and their social structures. Interested in studying the native, wild bees in the United States and their role in pollinating crops and wild plants, Dr. Mallinger took part in a number of related studies. As her academic career moved along, however, she became more and more interested in the ways “we can support native bee populations through various things like planting native habitat for them and reducing pesticide use.”

“Just like honey bees, native bees can be affected by pesticides,” said Dr. Mallinger. “One difference, however, is that honey bees are managed and moved around. They tend to be placed in agricultural settings. Wild bees, on the other hand, tend to live where they want to live. Some of them might be more common in urban settings, some more so in agricultural settings and then you might have some that are really not present in either and might only live in a wetland or a forest. So, the impact of pesticides on wild bees is going to depend on where the bees are found.”
  
In order to investigate the impact of pesticides on native bees, Dr. Mallinger, along with her professors and colleagues, began a three year research project that looked at the correlation between pesticide treated pollinator-dependent crops and the abundance of native bees in Wisconsin.

To study this, Dr. Mallinger and her team decided to study the bees frequenting apple orchards in Wisconsin. Apples are an excellent example of a pollinator -dependent crop, so Wisconsin’s plethora of orchards made this the ideal place to study these impacts. Of course, calculating the impact was more difficult.  In order keep an eye on the population, Mallinger and her team employed a weight system and a bee sampling system. To calculate the amount of pesticides, Dr. Mallinger and her team created a formula for calculating a “toxicity” score for each orchard. This was particularly important because pest management practices range from orchard to orchard, so her team needed to try to find a number that represented a range of factors including the date and amount of each pesticide, fungicide or herbicide used, as well as its known impact on bees.

It’s important to note here that the orchards in this study were not sprayed while the apple blossoms were in full bloom. Many farmers choose to abide by this rule because it limits the bees exposure to chemicals. As Dr. Mallinger explained, however, “even if farmers spray outside of the bloom they are risking exposure. They are spraying their orchard which might have flowing weeds and the spray ends up on the weeds and then the bees visit those flowers.”

In any case, the toxicity score was used in conjunction with the bee population scoring to determine that the overall impact of pesticides depended greatly on the species of wild bee. In particular, the study found that there was a significant negative effect on sweat bees, or more specifically Lasioglossum spp. While the reason for this distinct impact on one group of species is not fully understood, Dr. Mallinger hypothesizes that the size and foraging range of sweat bees are determining factors.

“These are bees that are very small when compared to other bees,” Dr. Mallinger said. “So, I think one of the reasons we found negative effects on these bees is because their populations are probably pretty confined to the orchard, whereas a lot of the larger bees have larger foraging ranges, so their exposure is less so than sweat bees. Additionally, these varieties of sweat bees have a very long foraging period compared to other bees so that long activity period also increases exposure.”

While sweat bees are fairly small, and perhaps seem irrelevant to some, research from Dr. Mallinger and others is beginning to show that diversity is key when it comes to successful pollination.

“One of my other papers found that the diversity of bees, not just abundance, resulted in higher fruit set and higher yield in these apple orchard.  These higher yields translate to higher income, and ultimately, to more food for people,” said Dr. Mallinger. “Other research has also found that particular wild bees are actually better pollinators for crops like apples and blueberries when compared to honey bees. That could be because they are more faithful to that crop or that they carry more pollen or work more flowers in a particular span of time.”  
Further proof that our connection to these native bees is not only deeply rooted, but deeply necessary. 

For more on this research see:
Mallinger, R. E., Werts, P., & Gratton, C. (2015, October). Pesticide use within a pollinator-dependent crop has negative effects on the abundance and species richness of sweat bees, Lasioglossum spp., and on bumble bee colony growth. Journal of Insect Conservation J Insect Conserv, 19(5), 999-1010. doi:10.1007/s10841-015-9816-z https://www.researchgate.net/publication/283467545_Pesticide_use_within_a_pollinator-dependent_crop_has_negative_effects_on_the_abundance_and_species_richness_of_sweat_bees_Lasioglossum_spp_and_on_bumble_bee_colony_growth

Ramanujan, K. (2012, May 22). Insect pollinators contribute $29 billion to U.S. farm income | Cornell Chronicle. Retrieved October 12, 2016, from https://www.news.cornell.edu/stories/2012/05/insect-pollinators-contribute-29b-us-farm-income

Where can I learn more about our native bees?

“Bee Basics, An Introduction to Our Native Bees”
By Beatriz Moisset, Ph.D. and Stephen Buchmann, Ph.D.

Wisconsin Native Bee Guide:

“Rusty patched bumble bee proposed for U.S. endangered species status”


JOIN US SUNDAY: Bekah Loves Bees Week continues with a special article on honey bees.

No comments:

Post a Comment