New Studies Confirm Pesticide Exposure Major Contributor to Declining Honey Bee Populations
Researchers at the U.S. Department of Agriculture (USDA) and University of Maryland have found that low levels of pesticide exposure from crop pollination make honey bees more susceptible to the deadly gut parasite Nosema ceranae, contributing to declines in bee populations.
The study’s findings, released July 24 in the journal PLoSONE, expand on a recent report released by the USDA that found parasites, disease, genetics, poor nutrition and pesticide exposure as synergistic factors in the observable nationwide honey bee decline, but focused on technological stopgap measures without questioning the sustainability of widespread systemic neonicotinoid pesticide use. Adding urgency to USDA’s research, another study released July 22 in the Proceedings from the National Academy of Sciences shows that pollinator losses can have a detrimental effects on plant reproduction.
Pesticide Exposure and Susceptibility to Disease
The newest USDA research adds to the growing body of evidence that shows pesticide exposure weakens honey bees’ immune system making them more susceptible to parasites and pathogens. Researchers took pollen samples from crops that honey bees are known to pollinate including apples, watermelons, pumpkins, cucumbers, blueberries and cranberries to determine exposure levels and Nosema infection.
In sum, researchers found 35 different pesticides in pollen, with samples containing, on average, nine different pesticides ranging in classes from oxadiazines, neonicotinoids, carbamates, cyclodienes, formamidines, organophosphates and pyrethroids. Of these, the report links eight pesticides as increasing the risk of Nosema gut parasite infestations. Researchers most frequently found fungicides in pollen samples, particularly chlorothanlonil, which is a broad spectrum fungicide ubiquitously used on apples and other crops. The presence of fungicides is of particular concern. Not only do fungicides increase risks of infection with deadly Nosema parasites, but they also generally do not carry warning labels to tell farmers to refrain from application while crops are blossoming and bees are foraging, that is, when bees are most susceptible to pesticide poisoning.
Lead researcher Jeff Pettis, PhD at the Bee Research Laboratory in Beltsville, MD explained that honey bees that were fed pollen containing the fungicide chlorothalonil and collected at the hive entrance were almost three times more likely to become infected when exposed to the parasite Nosema, compared with control bees, which were not fed contaminated pollen.
The study shows that honey bees cannot sustain regular exposure to the vast array of agricultural chemical combinations that weaken honey bee immune systems and make them more susceptible to Nosema infestation. The majority of studies up to this point have examined honey bee exposure to only one chemical at a time.
Surprisingly, researchers also found that pesticides were evident in every single pollen sample, even those that were collected from nearby wildflowers that were not sprayed. Co-author Dennis vanEngelsdorp, PhD at the University of Maryland explained “It could be drift from when they sprayed their crop, but it also could be that the bees are picking it up and contaminating the pollen on the forage trip.” Whatever the cause, he continued, we “need to better understand how pesticides are getting into the hive. Clearly it is not just from collecting pollen from the crops that bees are being used to pollinate.”
Pollinator Loss and Impacts on Plant Populations
Adding to the growing body of research on pollinator declines, another study published last week shows that the decline of a single pollinator species significantly impairs plant reproduction. The study, Single pollinator species losses reduce floral fidelity and plant reproductive function, was published in the Proceedings of the National Academy of Sciences, out of the Rocky Mountain Biological Laboratory in Crested Butte, CO.
Researchers examined 20 plots of meadow in the region, removing the most populous bumblebee species out of each plot, and patrolling them regularly to determine whether other pollinator species could fill the shortage for wildflower pollination. Instead, researchers found that in the absence of bumblebees, pollinator species foraged more widely, becoming less devoted to one flower species. Researchers specifically focused on the purple larkspur wildflower, and found that with broader foraging patterns, larkspurs were less likely to receive pollen from the same species, which is required for successful pollination. Because of changes to pollinator assemblages, larkspurs then produced 30 percent fewer seeds. These results demonstrate the wider consequences that loss of pollinators to pesticides can have on plant reproduction as well as ecosystem health.
Since 2006, honey bees nationwide have suffered ongoing and rapid population declines, from hive abandonment and bee die-off in a phenomenon known as colony collapse disorder (CCD). The causes are numerous, however, recent scientific evidence points to the role of a systemic class of pesticides, neonicotinoids, which contaminate pollen, nectar and the wider environment, causing lethal exposure to honey bees and threatening our food systems. An extensive overview of the major studies showing the effects of neonicotinoids on pollinator health can be found on Beyond Pesticides’ What the Science Shows.
In response to massive pollinator declines, recent legislation proposed by Reps. John Conyers (D-MI) and Earl Blumenauer (D-OR), H.R. 2692, The Save America’s Pollinators Act, has called upon the U.S. Environmental Protection Agency to suspend the use of neonicotinoids and to conduct a full review of scientific research before allowing the entry of other neonicotinoids into the market. Tell your Representative to Save America’s Pollinators.
Visit EcoWatch’s BIODIVERSITY page for more related news on this topic.
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By Naomi Larsson
For centuries, the delicate silver dove has been a symbol of love and fidelity.
Biodiversity and Habitat Loss<p>Their near extinction is a symbol of the <a href="https://www.dw.com/en/global-biodiversity-outlook-targets-extinction-summit-new-york-pledge/a-54932895" target="_blank">biodiversity crisis</a> in the UK, largely driven by habitat destruction. Britain is now one of the countries with the most <a href="https://www.wwf.org.uk/future-of-UK-nature#:~:text=The%20UK%20is%20one%20of,than%20half%20are%20in%20decline" target="_blank">depleted nature</a> in the world according to the World Wildlife Fund. Half its plant and animal species are in decline and more than <a href="https://www.rspb.org.uk/about-the-rspb/about-us/media-centre/press-releases/let-nature-sing-wales/#:~:text=a%20natural%20tragedy.-,Over%2040%20million%20birds%20have%20vanished%20from%20UK%20skies%20in,unaware%20of%20the%20impending%20danger" target="_blank">40 million birds</a> have vanished in just half a century.</p><p>"[Turtle doves] are the canary in the [coal] mine because there are all these other species before it and after it," said Tree. "It's an umbrella for all the other species that are heading that way."</p><p>Turtle doves migrate south through Europe to sub-Saharan Africa between July and September, ending up in dry woodland and farmland areas of countries like Mali and Senegal for winter. </p><p>Droughts in West Africa and the Sahel region are believed to have contributed to the fall in turtle dove species recorded in northern Europe, with low rainfall reducing supplies of the seeds and insects the birds rely on for energy for the long journey home.</p>
Conservation and Farming<p><a href="https://www.operationturtledove.org/" target="_blank" rel="noopener noreferrer">Operation Turtle Dove,</a> a partnership project of charities including the Essex Wildlife trust, works with landowners and farmers to actively build turtle dove habitat.</p><p>Outten works with <a href="https://www.ebws.org.uk/birdsites/blue-house-farm-ewt-north-fambridge" target="_blank">Blue House Farm</a>, a 660-acre nature reserve in the UK county of Essex, where they have replicated weedy fallow plots. </p><p>"We work on it every year to make sure it's in the condition it needs to be with plants such as clovers and black medic," Outten said. "These plants are native to the landscape and produce the seed the birds feed on." </p><p>The birds eat a wide range of seeds from various plants that would have been abundant 50 or 100 years ago, added Guy Anderson, program manager for species recovery with The Royal Society for the Protection of Birds (RSPB). </p><p>"But it's simply true that with the gradual process of <a href="https://www.dw.com/en/farming-without-pesticides-how-can-we-make-agriculture-greener/a-52216796" target="_blank" rel="noopener noreferrer">intensifying our agricultural production</a>, the availability of those seeds has dropped and dropped," said Anderson.</p><p>Part of the project includes supplementary feeding — providing sources of food in the form of seed or grain. Under the Countryside Stewardship Scheme in England, farmers can receive financial support to create a turtle dove habitat. </p><p>Though they haven't recorded an increase in doves across the sites in the four years of working on the project, Outten said they are seeing improvements in how landowners and farmers manage habitat for the birds. </p>
A Turtle Dove Haven<p>The 3,500-acre Knepp Estate in West Sussex is another project taking a different approach and one of the few places where turtle dove numbers are increasing.</p><p>Isabella Tree and her husband Charlie Burrell converted their intensively farmed land into a rewilding project almost 20 years ago. They have let the land return to nature.</p><p>Just one year after they'd finished <a href="https://www.dw.com/en/uks-most-talented-architects-are-not-human/a-35952128" target="_blank">rewilding</a> the southern part of their property, they heard turtle doves for the first time. It's now a breeding hotspot for the birds with an estimated 19 pairs. Knepp is also home to <a href="https://www.rewildingbritain.org.uk/rewilding/rewilding-projects/knepp-estate" target="_blank" rel="noopener noreferrer">2% of the UK's population</a> of nightingales. </p><p>Tree is critical of supplementary feeding schemes that, in her view, are short term. She questions the chances of turtle doves getting to feed on scattered seeds before other mammals eat them first.</p>
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