28
Nov
Behavioral Effects in Bumblebees Linked to Neonicotinoid Insecticides
(Beyond Pesticides, November 28, 2018) Recent research out of Harvard University and published in the journal Science has demonstrated some of the mechanisms through which exposures to neonicotinoid pesticides harm bumblebee populations. The study found that exposure to imidacloprid, a neonicotinoid — the most widely used category of pesticides worldwide — directly impacts social behaviors in bumblebees. These behaviors have serious effects on the functioning and viability of bee colonies.
In the research experiment, worker bees exposed to imidacloprid exhibited reduced general and nurturant activity, and a tendency to locate themselves at the periphery of the nest. The study noted decreased caretaking and nursing behaviors, which in turn harms productivity and thermal regulation in the colony. These tasks are important to colony development; impaired thermoregulation negatively affected the bees’ typical construction of an insulating wax canopy for the nest, and poor caretaking can affect brood growth.
Investigators noted that, “Neonicotinoids induce widespread disruption of within-nest worker behavior that may conribute to impaired growth. . . . These changes in behavior acted together to decrease colony viability, even when exposure was nonlethal.” The authors also observed that many of these dysregulated behaviors were more pronounced at night than during sunlight hours, and were exhibited by queens as well as workers. Prior to the subject study, neonicotinoids were already understood to reduce growth in developing bee broods by impairing adults’ foraging abilities — related to both spatial navigation and so-called “floral learning” (acquiring and remembering how best to secure nectar from a variety of flowers of varying structural complexity).
Neonicotinoids are used frequently as seed coatings, as well as on a great number of agricultural crops. They are systemic pesticides that are taken up by plants and transported to leaves, flowers, roots, and stems, as well as to pollen and nectar; pollinators are at great risk of exposure to these compounds through their foraging activities. (These pesticides also contaminate waterways and are highly toxic to aquatic organisms.) Neonicotinoids affect the central nervous system of exposed target and non-target insects, leading to eventual paralysis and death.
Bees are responsible for nearly one-third of all the pollination that takes place on the planet. For more than a decade, the decline and loss of critical insect pollinators has been of enormous environmental, economic, and scientific concern. For nearly that long, neonicotinoid pesticides have been identified as primary contributors to this decline, which often manifests in reduced colony size through mortality. These compounds have been repeatedly pointed to as a cause of Colony Collapse Disorder. Other contributing factors include habitat fragmentation and destruction, the introduction of non-native species and pathogens, and some land management practices.
In 2013, the European Union voted to ban neonicotinoid pesticides for a two-year period. In May 2018, the General Court of the European Union (EU) banned three chief neonics — clothianidin, imidacloprid, and thiamethoxam — for any outdoor uses across the EU. Here in the U.S., the Environmental Protection Agency (EPA) did adopt, in early January of 2017, a policy to mitigate acute risks to bees from pesticides, and does offer some guidance on assessing risks to pollinators from pesticides. But as Beyond Pesticides noted earlier this year, EPA has been slow to act on neonicotinoids, despite the plethora of independent peer-reviewed, scientific papers demonstrating their hazards to pollinators and other non-target organisms.
In setting allowable uses of pesticides in agriculture, EPA utilizes risk assessment reviews with extreme limitations when it evaluates a food-use pesticide in combination with its non-food uses. The agency has been criticized by Beyond Pesticides because when it evaluates ecological impacts, EPA weighs the “economic, social, and environmental costs and benefits” associated with a given pesticide to determine whether an “unreasonable risk to human health and the environment” will occur. The problem with this approach is that it fails to allow for the prioritization of ecological protection, including protection of non-target pollinators.
Early in 2018, U.S. Representatives Earl Blumenauer (OR) and Jim McGovern (MA) reintroduced HR 5015, Saving America’s Pollinators Act of 2018, which, if enacted, would suspend the registration of certain neonicotinoid insecticides until the U.S. Environmental Protection Agency (EPA) conducts a full scientific review that ensures these chemicals do not harm pollinators. Whether the bill’s chances of passage will improve — with the reconfigured post-midterm election Congressional landscape — remains to be seen.
Protection of pollinators is an important focus of Beyond Pesticides; its work can be followed via its BEE Protective website page. Beyond Pesticides advocates to protect critical pollinators from the ravages that neonicotinoids can cause. It does so through its BEE Protective activities; its work to expose the health and environmental risks of chemical-intensive agricultural practices (including the use of pesticides); and its advocacy for organic agriculture because of its health and environmental benefits. Beyond Pesticides also offers guidance on less harmful, more-holistic approaches to land management. See its information on how to help protect pollinators.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: https://e360.yale.edu/digest/neonicotinoids-impact-bees-nursing-and-social-behaviors-study-finds
