[Pollinator] How the Bees You Know are Killing the Bees You Don't

[Matthew Shepherd]

An excellent article about bumble bee conservation, featuring several
people known to many of us, including Sam Droege, Sheila Colla, Victoria
Wojcik, Zac Browning, and Rich Hatfield.



Matthew



*****************



FROM: Inside Science

https://www.insidescience.org/news/how-bees-you-know-are-killing-bees-you-don%E2%80%99t



*How the Bees You Know are Killing the Bees You Don’t*

Commercially managed bumblebees and honey bees may be contributing to wild
pollinator decline.



Monday, January 23, 2017 - 11:00

Nala Rogers, Staff Writer





(Inside Science) -- Sam Droege slides a drawer from a tall white cabinet,
releasing an odor of mothballs. Row after row of small bodies stand
skewered on pins, fragile limbs frozen, furry backs­ as bright as
sunflowers. They are all examples of Bombus affinis, most collected from
meadows where this bumblebee species no longer flies. The surrounding
drawers hold nearly 2,000 more.



"Affinis was a dirtball species. It was super common. That's why there's
drawers and drawers of them," said Droege, a biologist with the U.S.
Geological Survey whose job sometimes involves identifying bees here at the
Smithsonian National Museum of Natural History in Washington.



Earlier this month, the insects in the open drawer, more commonly called
rusty patched bumblebees, were listed as endangered under the U.S.
Endangered Species Act of 1973. The International Union for Conservation of
Nature estimates that they have declined by more than 90 percent over the
last decade. According to Rich Hatfield, a senior conservation biologist at
the Xerces Society who helped assess the species for the IUCN, the leading
suspect in their disappearance is disease spread by other bees --
commercial bumblebees raised by humans to pollinate crops.



Most people have heard that pollinators are in trouble, and with them
agricultural products worth more than $200 billion annually. But public and
policy concern largely revolves around western honey bees, a domesticated
species whose population has actually risen worldwide over the past few
decades, despite recent challenges faced by beekeepers. Their success
stands in stark contrast to the more than 20,000 other distinct species of
bees worldwide, many of which are thought to be declining or facing
extinction.



Bees are the most important pollinators on earth, pollinating more plants
than any other group of animals, said Hatfield. In appearance, they range
from glimmering green gemstones the size of a gumball to brownish specks
that could crawl through a cocktail straw. And while losing one bee species
probably won't shatter ecosystems, losing enough of them will, said Droege.
Diverse wild bee communities help buffer ecosystems, ensuring that
something is left to pollinate plants even under the stress of climate
change and other environmental challenges. They also help pollinate crops,
sometimes more efficiently than the commercial bees farmers increasingly
rely on.



Humans raise a small number of bee species commercially, and these managed
bees are crucial for modern food production. But they don't always live in
harmony with the natural world. Managed bees can spread diseases, compete
with wild bees for food, invade new habitats and upset the balance of plant
species.



*Bees as livestock*

Humans first domesticated honey bees, a group that includes several similar
species, around 9,000 years ago. Honey bees are native to Asia, Europe and
Africa, but humans have carried them around the globe, allowing them to
establish feral populations. In most cases, the invasions happened so long
ago that native bees have either adapted or gone extinct.



“We basically have no idea what the native bee fauna looked like prior to
the introduction of honey bees,” said Dave Goulson, an entomologist at the
University of Sussex in England. “It may have absolutely devastated the bee
fauna of the Americas.”



Fewer than 50 years ago, people also began raising other types of bees for
crop pollination, including several species of bumblebees. Bumblebees are
capable of shaking pollen loose from plants such as eggplants and tomatoes
-- crops honey bees can't pollinate. While honey bees still dominate the
beekeeping world, farmers now use bumblebees routinely, most often in
greenhouses.



>From a typical bumblebee colony of a few hundred, only the young queens
survive the winter, hibernating until they can start their own colonies in
spring. Farmers usually buy new colonies from breeders each year. Honey
bees, in contrast, live in colonies of up to 60,000 bees, and these
colonies can persist indefinitely.



Recently, problems such as varroa mites, inhospitable farmland and colony
collapse disorder have made it harder for beekeepers to maintain colonies
and meet the rising demand for bees in agriculture. In the United States,
beekeepers now lose about 40 percent of their colonies each year, four
times the fraction they consider acceptable. They can replace lost colonies
by splitting surviving colonies in two, but this technique can become
unsustainable.



Nevertheless, the total number of managed honey bees worldwide has risen by
45 percent over the last half century. Honey bees are in no danger of
extinction, said Hatfield -- and our reliance on them may come at a cost.



*How bee disease spreads*

Managed bees may transmit new diseases to wild bees, or they may allow
existing diseases to multiply and "spill back" into wild populations.
Commercial beekeeping often involves maintaining bees at high densities,
making it easy for diseases to pass from bee to bee. And companies
routinely feed bumblebees with pollen gathered by honey bees, helping
diseases to spread between species, said Peter Graystock, a conservation
biologist at the University of California, Riverside. Some companies have
started irradiating the pollen to kill pathogens, but others still feed it
to bees as is.



In a 2013 study, Graystock and his colleagues tested imported bumblebee
colonies that had supposedly been screened for disease, and found that more
than three-fourths of them contained disease-causing microbes. When the
researchers experimentally fed pollen and waste from the infected bee
shipments to healthy bumble and honey bees, many of the new bees got sick.



However, flowers are probably the hotspots of disease transmission to wild
bees, said Graystock. With colleagues, he recently demonstrated that two
commercial bee species, buff-tailed bumblebees and western honey bees, can
rapidly spread five kinds of pathogens between flowers. Some of the
pathogens could only infect one of the two bee species, but they often
hitched a ride on the other one.



“Imagine flowers as a dinner plate that you're eating from, but everybody
else is also eating from that dinner plate as well,” said Graystock. “They
could accumulate quite a lot of different microbes.”



Evidence from the field supports the idea that wild bees can catch diseases
from managed bees. In Canada, Ireland and England, researchers have found
elevated disease rates in wild bees living near greenhouses that use
commercial bumblebees.



The lack of data on most wild bee species makes it hard to judge the threat
facing their populations. Some ailments, such as the varroa mites that
infest managed honey bees, appear to be harmless to other kinds of insects,
including wild bumblebees. But other diseases, such as deformed wing virus
and the dysentery-causing fungus Nosema ceranae, are known to harm multiple
species that aren't closely related. Researchers usually have no idea
whether a given wild pollinator can catch a particular disease, or how sick
it would get if it did.



Still, circumstantial evidence suggests that the impacts on wild
pollinators can be devastating. In North America, a species called
Franklin’s bumblebee is thought to have recently gone extinct, and four
other once-common species have suffered estimated declines of more than 70
percent.



*Wiped out by plagues*

While no one knows for sure what’s killing wild American bumblebees, the
dominant hypothesis is one or more diseases introduced by commercial
bumblebees imported from Europe, said Sheila Colla, a conservation
biologist at York University in Toronto. The timing matches up with the
rise of commercial bumblebees for pollinating greenhouse crops. At least
two of the declining species have high rates of a fungal disease called
Nosema bombi, and the strain they carry is genetically similar to the one
found in bees from Europe, suggesting it may have been recently introduced.
And many researchers think that the wild bees have vanished too quickly,
and over too wide an area, for the culprit to be anything except disease.
For example, the rusty patched bumblebees that just received endangered
species protections have disappeared from around three-fourths of their
historic range, according to a study by Colla and her colleagues.



"You can't really chalk it up to something like pesticide use, because that
wouldn't explain why it disappeared in the Smoky Mountains," she said.



In the United States, it's now illegal to import any kind of bumblebee from
overseas. But non-native bumblebees are still pouring into Argentina, even
though two species have already turned invasive there. The second invasive
species, known as the buff-tailed bumblebee, was first introduced to
Argentina in 2006 to pollinate crops. Since then, feral buff-tailed
bumblebees have spread across the region, wiping out native Patagonian
bumblebees as they go.



Patagonian bumblebees are the largest bumblebees in the world, and the only
ones native to the southern part of South America. They used to be a
familiar sight in Chilean and Argentinian gardens, where their deep buzz
and fluffy orange bulk made them hard to miss.



“They look like little bears,” said Marina Arbetman, a molecular ecologist
at the National University of Río Negro and the National University of
Comahue in Bariloche, Argentina.



Patagonian bumblebees have vanished so fast that they are almost certainly
suffering from a disease epidemic, said Arbetman. She has an idea what that
disease might be: Apicystis bombi, a parasite that attacks bees’ fat
stores. The parasite was absent in the region until buff-tailed bumblebees
invaded, but now it is found in native Patagonian bumblebees and feral
buff-tailed bumblebees, as well as another bumblebee species that invaded
earlier. Genetically, the parasites look similar to A. bombi parasites from
Europe, suggesting that, like N. bombi in North America, they too rode in
recently on commercial bees.



The loss of Patagonian bumblebees could have ecosystem-wide impacts, said
Arbetman's adviser Carolina Morales, an ecologist at the National
Scientific and Technical Research Council and the National University of
Comahue. Patagonian bumblebees have longer tongues than the invasive
species, enabling them to pollinate native plants with long, tube-shaped
flowers. Invasive buff-tailed bumblebees can’t reach into long flowers
normally, so they tear holes in them instead, stealing nectar without ever
touching the pollen. One native plant appears to already be suffering
reproductive costs, producing less fruit in landscapes taken over by the
invasive bees, according to unpublished research by Morales and her
colleagues.



Now, a few Patagonian bumblebees are hanging on across their former range,
but sightings in most areas are rare. Arbetman spotted one last fall, but
before then, she hadn't seen any in two years. "And you know I'm looking at
every flower," she said.



*Fighting over flowers*

Competition for food is another source of conflict between managed and wild
bees. Wildflowers are growing scarcer around the world, and wild bee
populations are often limited by how much pollen and nectar they can find.
Commercial beekeepers need places to keep their bees when they’re not on
pollination jobs, and in the United States they sometimes use public land.



Resource competition between managed and wild bees is controversial, and in
some cases, it appears not to be a problem. But in the majority of
experimental studies where scientists have tested specifically for
competition, they have found it, said Victoria Wojcik, research director
for an international nonprofit called the Pollinator Partnership in San
Francisco. Most such studies have focused on bumblebees, so there aren't
enough data to make recommendations on preserving other types of bees. But
if land managers have sensitive bumblebee habitat, they may want to think
twice before allowing commercial honey bee hives on their land, said
Wojcik. "There could be food-based competition, and the bumblebee loses in
that situation," she said.



Bumblebees may be losing out to feral honey bees in a remote nature reserve
in California, even though there are no managed hives around. The site had
hardly any feral honey bees in the late 1990s, probably because of a mite
infestation that swept through honey bee populations shortly beforehand.
But since then, honey bees have recovered, and the native bumblebees have
drastically declined. Diane Thomson, an ecologist and conservation
biologist at the Claremont Colleges in California, monitored their
populations over 15 years.



"I've been able to show, from looking at what plants they're using, that
bumblebees appear to be getting squeezed off of certain floral resources
that are important for them as the number of honey bees has gone up," she
said.



These findings reinforce an earlier experiment Thomson conducted at the
same site. In that study, she brought in honey and bumblebee colonies and
placed them at various distances from each other. Bumblebees placed near
honey bee hives had less reproductive success, producing fewer and smaller
fertile bees capable of starting a new generation.



Now, Thomson's experimental hives are long gone, but native bumblebees are
still being outcompeted. Their disappearance is especially striking because
it happened in a protected area, far from pesticides, development and human
disturbance.



“My site is really buffered from some of the potentially very harmful
causes of bee declines in other places,” said Thomson. “And yet, we're
still seeing a decline in these native bumblebee populations.”



*What can be done to save the bees*

People can reduce the risks to wild bees by not importing managed bees from
other countries, by reducing the use of non-native species, and by
thoroughly screening for diseases, policies that some countries already
employ to varying degrees. Another simple strategy is to put screens on
greenhouse vents before releasing bumblebees inside, a practice that Japan
mandated after suffering its own bumblebee invasion, said UC Riverside's
Graystock. But the most powerful way to help wild and managed bees coexist
may be something beekeepers are already pushing for: creating more habitat
where pollinators can find food.



Farmland used to have lots of rich pollinator habitat, with diverse plant
species flowering at different times. Wild bees took care of most crop
pollination, while honey bees were primarily used for honey, said Zac
Browning, a fourth-generation commercial beekeeper based in Jamestown,
North Dakota, who owns around 27,000 honey bee colonies. Browning said he
has seen agriculture move toward giant, pesticide-soaked fields planted
with a single type of crop -- a landscape hostile to wild and managed bees
alike. Now, he said, farmland is "probably, in many ways, the most
dangerous place to be, if you're a bee."



Since bees often can't survive in modern farmland, farmers now pay
beekeepers to bring in bees just when their crop is flowering. The new
system puts stress on both commercial and wild bees, forcing them to
compete for scarce resources. This stress probably makes them more
vulnerable to disease, said Graystock.



Modern crop pollination may also threaten food security. A growing body of
research shows the crucial role wild insects still play in agriculture,
ensuring stable production from year to year and boosting yields regardless
of whether honey bees are present. And the more a crop relies on a single
kind of bee, the more vulnerable it is to diseases and other crises that
might strike that bee's population.



Project Apis, an agricultural nonprofit focused on honey bee health, is
working to increase pollinator habitat on farmland by providing seeds for
farmers to plant in unused patches of land. Its seed mixes include plants
for native species as well as for honey bees, said Danielle Downey, the
project's executive director.



"It would be great if there were not so much demand for every scrap of
habitat that's left," she said.



Hatfield agrees. He works for the Xerces Society, a nonprofit based in
Portland, Oregon that focuses on protecting wild insects and other
invertebrates. "Our take-home message always comes back to 'if you want to
do something, the right thing to do is to plant habitat,'" he said.
"Habitat is going to support our native bees, and it's also going to
support the honey bees."



Policy makers are also starting to realize that bee-friendly landscapes are
important. The U.S. farm bill has offered incentives for landowners to
restore pollinator habitat since 2008, and several states are starting to
plant pollinator habitat along highways. And while the federal Pollinator
Health Action Plan released last year has been criticized for focusing too
much on honey bees, it does list habitat for all pollinators as a top
objective.



*Backyard Beekeeping Won’t Save the Bees*

Not all managed bees are part of commercial businesses. People also keep
honey bees for fun, often in backyards or on rooftops. The hobby is soaring
in popularity, with major cities such as Los Angeles and New York recently
lifting restrictions on urban beekeeping. In the Washington, D.C. area, so
many people want to be beekeepers that there isn't enough room for them in
beginner classes run by local clubs, said Jan Day, an educational
technology consultant who has raised bees in her backyard for three years.

Like many beekeepers, Day is fascinated by bee society. She uses her bees'
honey to make a fermented drink called mead, and she values the connection
her bees provide to the natural world.

"I'm much more aware of the changing seasons, and what's blooming at any
given time. Now I pay attention to that stuff," she said. "It has been one
of the most thoroughly engaging hobbies I've ever had."

While Day loves her bees, she doesn't view them as a way to help the wild
pollinators she also cares about. But some hobbyist beekeepers may not
understand the distinction, she said. People hear that bees are in trouble,
and they want to help by getting their own colony. Day advises them to
plant wildflowers instead.

The Xerces Society's Hatfield agrees. There are good reasons to raise bees,
he said. Moreover, beekeepers are strong promoters of habitat restoration
and pesticide reduction, policies that help managed and wild bees alike.
But becoming a beekeeper is not a route to pollinator conservation.
According to Hatfield, "That’s kind of like keeping chickens for bird
conservation."



*Unknown populations*

Patagonian bumblebees and rusty patched bumblebees are flashy species that
were once very common, so people noticed when they vanished. But they are
the exception. For the vast majority of wild bee species, no one knows
whether they are in danger, because no one has data on their populations.
Often, we don’t even know they exist. According to one estimate, Earth
holds another 20,000 bee species waiting to be discovered, on top of the
20,000 already described, said Sam Droege.



Droege has spent years trying to fill the knowledge gaps, amidst changing
political landscapes that shuffled him between programs and agencies. He
designed a nationwide monitoring program for U.S. bees, but the funding
dried up before it could bear fruit. Now, he runs the USGS Bee Inventory
and Monitoring Lab in Beltsville, Maryland, which catalogs local bees,
creates identification guides, and helps land managers across the country
conduct their own, small-scale surveys. But despite his efforts, there is
still no comprehensive monitoring effort for U.S. bees.



"There's no program," he said. "There are no real statistics other than
'can't find it anymore.'"



Back at the museum, Droege picks up a tiny black bee by the pin and holds
it in the circle of light at the base of his microscope. He turns the bee
until light glances sideways off of minute pits and hairs, shadows
revealing their arrangement. It is a female Pseudopanurgus, a poorly
described genus, and Droege can’t tell whether this bee represents any
named species. He has no idea whether she came from a thriving population,
or one on the brink of extinction.







­----------



Matthew Shepherd

Communications Director



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