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.
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