Bees Face ‘a Perfect Storm’ — Parasites, Air Pollution and Other Emerging Threats
By Jodi Helmer
Bees are facing a pandemic of their own.
A collection of threats — habitat loss, pathogens, pesticides, pollution and poor nutrition — have led to widespread decline in bee health and pollinator populations.
The threats add up: The number of commercial honeybee colonies declined by more than quarter million between April and June 2020, according to the latest data from the U.S. Department of Agriculture. Native bees are at risk, too, with 1 in 4 native species in North America at risk of extinction.
"Things are not going so well for bees," says Arthur Grupe, a postdoctoral researcher at the University of Colorado. "There's been a lot of research looking into the causes, and usually, humans try and look for the magic bullet — what is the one thing causing this problem that we can stop? And the research has shown that it's actually a collection of things."
A single-cell fungal pathogen called Nosema is one of the latest threats.
Nosema reproduces in the gut, where it ruptures, spreads out and then infects the cells of the digestive tracts. It leads to lethargy, reduced foraging ability, poor sense of direction and, often, death.
Although Nosema apis and Nosema ceranae — two strains of the fungi — have been regularly recorded in Europe, North America and Southeast Asia, the pathogen is now more widespread than ever, according to recent research published in the journal PLOS Pathogens. Grupe was the lead author.
Grupe notes that N. apis, once the dominant strain affecting commercial bee colonies, was observed to be seasonal, which helped protect against total colony collapse. The increasing export of commercial beehives from Europe, however, has expanded the distribution of the problematic pathogen.
USDA photo by David Kosling
At the same time, reports of N. ceranae have increased dramatically — and it infects hives all year long.
"Historically, it was thought that Nosema ceranae wasn't so much of a problem because its spores can't survive freezing or near-freezing temperatures," he explains. "But as winters have become milder these spores are able to persist and then cause infection, and Nosema ceranae has overtaken Nosema apis as the predominant infect of European honeybees."
Once a bee is infected with Nosema, it can contaminate entire colonies — where social distancing is not an option — and spread that infection to the wild. Infected honeybees can leave spores on flowers, transmitting the pathogen to other susceptible pollinators, including native bees. This "community spread" has led Grupe and his co-author C. Alisha Quandt to declare it a "pandemic" in their paper.
Research published this July in the journal Nature Ecology and Evolution illustrates the threat. Field studies in upstate New York found that one in 11 flowers carried disease-causing parasites, including Nosema ceranae, N. bombi, Crithidia bombi, C. expoeki and neogregarines that were linked to declines in bee populations. Social bees, including honeybees and bumblebees, were more likely to be infected with parasites than solitary bee species.
"Bees visit hundreds of flowers a day and act as a 'shared food source' between the other foraging bees in the area which will feed from the same flowers," explains study co-author Peter Graystock, now a research fellow at Imperial College in London. "If a bee has been in contact with parasites or is suffering from an infection, they may shed some contagious parasite cells on the flower when they visit it, and then when a subsequent bee visits the same flower, the bee may become infected with those parasite cells or spores."
An endangered rusty patched bumble. USGS Bee Inventory and Monitoring Lab
Air pollution might also contribute to bee declines.
To understand more about that air-quality risk, Barbara Smith, associate professor at the University of Coventry, is working with beekeepers in the United Kingdom to set up sensors in their hives to record the level of air pollution and incidents of disease to determine whether there is a correlation.
"We know that air pollution is bad for humans and mammals, and we're interested to see if the same is true for invertebrates," Smith explains. "We have reason to believe that it could have an impact, because we know that we can record air pollution particulates in honey."
Indeed, previous research found that pollutants lingered on the bodies of honeybees in areas with high levels of air pollution; exposure to diesel exhaust interfered with their foraging ability; and that air pollution may affect the heart and immune systems of wild honeybees.
Smith hopes her research, funded through the British Beekeepers Association, will provide more data about the impact of air pollution on bee health and population decline. Even if the results are conclusive, she knows it's just one of the issues that needs to be addressed to restore pollinator populations.
"I don't think that these declines in pollinators are down to one thing," she says. "It's about a suite of things that are happening. It's like a perfect storm."
Addressing the Threats
The fact that bees are facing multiple threats to their health and survival means that coming up with a single solution is impossible, especially when researchers are still trying to collect data.
Grupe notes that most of the research on Nosema infections has focused on European honeybees. The pathogen also affects native bees, but few researchers have done environmental surveys to capture wild bees from native ecosystems and screen them for Nosema.
"There's only a handful of studies that have documented Nosema infections in native bees and the problem that needs to be addressed in the future," he says. "More work needs to be done to understand Nosema infections in native bee species and the potential consequences to native ecosystems, and if native bees suffer a similar fate as honeybees when infected."
To complicate matters, the manufacturer that made a chemical control for Nosema, which the company called its "bread and butter," went out of business in 2018, leaving beekeepers without access to a treatment. Grupe cites a mix of high prices and a complex supply chain that led to the discontinuation of the product.
But the cost for bees could be higher.
"All of a sudden we have these pathogens that are globally distributed, that are negatively impacting agricultural crops and negatively impacting native plant communities, and we don't really have any way to treat it." This could further imperil native bees if the pathogens continue to spread from commercial hives.
In the absence of treatment, Graystock promotes prevention. Increasing floral abundance and diversity, he says, could offer some protection against parasite transmission. His research showed that the incidence of parasites was higher when floral numbers were low and decreased as the number of floral resources increased.
Diverse plant communities may be especially important in urban areas where higher human populations are linked with fewer species of wild bees, according to a 2020 study published in the journal Landscape and Urban Planning.
Rick Brohn / USFWS
Planting strips of native pollinator plants on farmland could even improve crop yields. Another study published this summer found that five out of seven crops in major crop-producing areas had lower yields and production due to pollinator limitations. Attracting wild bees and honeybees, especially in intensive production areas, could help bolster food security, the research showed.
All of this backs up Graystock's points.
"It's important to appreciate the vast diversity of our pollinator communities, not just in terms of bee diversity but also floral diversity," he says. "Frequently in ecology we find the solutions for maintaining the health of our wildlife are simply to support and promote our native wild communities above others."
Reposted with permission from The Revelator.
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By Robert J. Orth, Jonathan Lefcheck and Karen McGlathery
A century ago Virginia's coastal lagoons were a natural paradise. Fishing boats bobbed on the waves as geese flocked overhead. Beneath the surface, miles of seagrass gently swayed in the surf, making the seabed look like a vast underwater prairie.
Why Didn’t Seagrasses Recover Naturally?<p>Development, nutrient runoff and other human impacts have damaged marshes, mangroves, coral reefs and seagrasses in many bays and estuaries worldwide. Loss or shrinkage of these key habitats has reduced commercial fisheries, increased erosion, made coastlines more vulnerable to floods and storms and harmed many types of aquatic life. Rapid climate change has compounded these effects through <a href="https://theconversation.com/ocean-warming-has-fisheries-on-the-move-helping-some-but-hurting-more-116248" target="_blank">rising global temperatures</a>, more <a href="https://theconversation.com/more-frequent-and-intense-tropical-storms-mean-less-recovery-time-for-the-worlds-coastlines-123335" target="_blank">frequent and severe storms</a> and <a href="https://theconversation.com/as-climate-change-alters-the-oceans-what-will-happen-to-dungeness-crabs-61501" target="_blank">ocean acidification</a>.</p><p>In the late 1990s, local residents told two of us who are longtime students of seagrasses (Robert "JJ" Orth and Karen McGlathery) that they had spotted small patches of eelgrass in shallow waters off Virginia's eastern shore. For years the conventional view had been that seagrasses in this area had not recovered from the events of the 1930s because human activities had <a href="https://doi.org/10.1016/j.aquabot.2005.07.007" target="_blank">made the area inhospitable for them</a>.</p><p>But studies showed that water quality in these coastal bays was <a href="https://doi.org/10.1007/BF02782971" target="_blank" rel="noopener noreferrer">comparatively good</a>. This led us to explore a different explanation: Seeds from healthy seagrass populations elsewhere along the Atlantic coast simply weren't reaching these isolated bays. Seagrasses are underwater flowering plants, so seeds are among the main ways they reproduce and spread to new environments.</p>
Eelgrass beds were restored in four bays at the southern tip of Virginia's eastern shore on the Atlantic coast. David J. Wilcox/VIMS, CC BY-ND
Sowing a New Crop<p>From our <a href="https://doi.org/10.2307/1941597" target="_blank">earlier research</a>, we knew that when eelgrass seeds fall from the parent plant, they sink to the sea bottom quickly and don't move far from where they land. We also knew that these seeds don't germinate until late fall or early winter. This meant that if we collected the seeds in spring, when eelgrass flowers, we could hold them until the fall, helping them survive over the months in between.</p><p>We decided to try reseeding eelgrass in the areas where they were missing. Starting in 1999, we collected seeds by hand from underwater meadows in nearby Chesapeake Bay – plucking the long reproductive shoots, bringing them back to our laboratory and holding them in large outdoor seawater tanks until they released their seeds naturally. After about 10 years we started gathering the grasses using a custom-built underwater "lawn mower" to collect many more of the reproductive shoots than we could by hand.</p><p>In 2001 we sowed our first round by simply tossing seeds from a boat. Our first test plots covered 28 acres of mud flats in waters 2 to 3 feet deep. Returning the following year, we saw new seedlings sprouting up.</p><p>Each year since then, the <a href="https://www.vims.edu/" target="_blank">Virginia Institute of Marine Science</a> and the <a href="https://www.nature.org/en-us/about-us/where-we-work/united-states/virginia/" target="_blank" rel="noopener noreferrer">Nature Conservancy's Virginia Coast Reserve</a>, along with staff and students from the <a href="https://www.vcrlter.virginia.edu/" target="_blank" rel="noopener noreferrer">University of Virginia</a>, have led a team of scientists and citizens to collect and seed a combined 536 acres of bare bottom in several coastal bays.</p><p>These initial plots took off and rapidly expanded. By 2020 they covered 9,600 acres across four bays. Several factors helped them flourish. These bays are naturally flushed with cool, clean water from the Atlantic Ocean. And they lie off the tip of Virginia's eastern shore, where there is little coastal development.</p>
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="a482c2146febd6782c99960c2b55feb8"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/K9NyfPLINtk?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
Sheltering Marine Life and Storing Carbon<p>Since eelgrass disappeared from these bays in the 1930s, human understanding of seagrass ecosystems has evolved. Today people don't pack their walls full of seagrass insulation but instead value different services they provide, such as habitat for fish and shellfish – including many <a href="https://doi.org/10.1111/conl.12645" target="_blank" rel="noopener noreferrer">commercially and recreationally important species</a>.</p><p>Scientists and government agencies also have recognized the importance of coastal systems in capturing and storing so-called "<a href="https://oceanservice.noaa.gov/facts/bluecarbon.html" target="_blank" rel="noopener noreferrer">blue carbon</a>." In fact, we now know that seagrasses constitute a globally significant <a href="https://doi.org/10.1038/ngeo1477" target="_blank" rel="noopener noreferrer">carbon sink</a>. They are a key tool for reducing carbon dioxide in the atmosphere and <a href="https://doi.org/10.1038/s41598-020-64094-1" target="_blank" rel="noopener noreferrer">slowing climate change</a></p><p>We are working to understand the valuable services that our restored seagrass beds provide. To our surprise, fish and invertebrates returned within only a few years as the meadows expanded. These organisms have established extensive food webs that include species ranging from tiny seahorses to 6-foot-long sandbar sharks.<br></p><p>Other benefits were equally dramatic. Water in the bays become clearer as the seagrass canopy trapped floating particles and deposited them onto the bottom, burying significant stocks of carbon and nitrogen in sediments bound by the grasses' roots. Our research is the first to verify the overall net carbon captured by seagrass, and is now being used to issue carbon offset credits that in turn <a href="https://vaseagrant.org/eelgrass-carbon-credits/" target="_blank">create more funds for restoration</a>.</p><p>One big question was whether restoring seagrasses could make it possible to bring back bay scallops, which once generated millions of dollars for the local economy. Since bay scallops no longer existed in Virginia, we obtained broodstock from North Carolina, which we have <a href="https://chesapeakebaymagazine.com/return-of-the-bay-scallop/" target="_blank">reared and released annually</a> since 2013. Regular surveys now reveal a growing population of bay scallops in the restored eelgrass, although there is still some way to go before they reach levels seen in the 1930s.</p>
Restored seagrass beds (dark areas) along Virginia's Atlantic coast, with sunlight reflecting from a small island. Jonathan Lefcheck, CC BY-ND
A Model for Coastal Restoration<p>Repairing damaged ecosystems is such an urgent mission worldwide that the United Nations has designated 2021-2030 as the <a href="https://www.decadeonrestoration.org/" target="_blank">U.N. Decade on Ecosystem Restoration</a>. We see the success we have achieved with eelgrass restoration as a prime model for similar efforts in coastal areas around the world.</p><p>Our project focused not only on reviving this essential habitat, but also on charting how restoring seagrasses affected the ecosystem and on the co-restoration of bay scallops. It provides a road map for involving scholars, nonprofits organizations, citizens and government agencies in an ecological mission where they can see the results of their work.</p><p>Recent assessments show that the restored zone only covers about 30% of the total habitable bottom in our project area. With continued support, eelgrass – and the many benefits it provides – may continue to thrive and expand well into the 21st century.</p>
EcoWatch Daily Newsletter
By Jessica Corbett
Leaders of climate and conservation groups on Tuesday welcomed House Democrats' introduction of landmark legislation that aims to address the ocean impacts of human-caused global heating and reform federal ocean management—recognizing that, as Rep. Raúl M. Grijalva put it, "a healthy ocean is key to fighting the climate crisis."
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