28
Jul
Degradation of Color Discrimination Associated with Glyphosate Exposure Impairs Bees’ Foraging Ability
(Beyond Pesticides, July 28, 2023) A study published in Science of the Total Environment finds glyphosate can adversely impact sensory and cognitive processes in bumblebees (Bombus terrestris). Glyphosate exposure impairs bees’ learning of aversive stimuli like electric shocks paired with specific color discrimination. Additionally, the pesticide reduces attraction to UV (ultraviolet) light, specifically the color blue, and temporarily impacts locomotion and phototaxis (movement in response to light). These impairments to sensory and cognitive processes render foraging difficult for these glyphosate-exposed pollinators and vulnerable to unavoidable predators. The study highlights that symptoms of widespread chemical exposure may reduce foraging efficiency and adversely affect ecosystems, especially those dependent on insect pollinators.
Pollinator decline directly affects the environment, society, and the economy. Without pollinators, many plant species, both agricultural and nonagricultural, will decline or cease to exist as U.S. pollinator declines, particularly among native wild bees, limit crop yields. In turn, the economy will take a hit, since much of the economy (65%) depends upon the strength of the agricultural sector. As the science shows, pesticides are one of the most significant stressors for pollinators. In a world where habitat loss and fragmentation show no sign of abating, scientists have concluded that the globe cannot afford to continue to subject its critically important wild insects to these combined threats. Therefore, studies like these emphasize the need to establish monitoring and conservation to assess fluctuations in ecosystem services of essential species. The study notes, “The high-throughput paradigm presented in this study can be adapted to investigate sublethal effects of other agrochemicals on bumblebees or other important pollinator species, opening up a critical new avenue for the study of anthropogenic stressors.”
Glyphosate-based herbicides (GBHs) are the most common herbicides used globally. Previous studies evaluating chronic glyphosate or GBH exposure assessed the survival, development, physiology, colony thermoregulation, or gut microbiota specific to honey bees. However, few studies have tested field-realistic exposure to glyphosate on non-honey bees’ (i.e., bumble bees) cognitive performance. Thus, the study investigates how long-term glyphosate exposure affects locomotion, movement in response to light, and learning in bumblebees using an automated high-throughput assay with a control UV and green or blue light.
Control bumblebees in the study prefer UV light to blue light. Yet, glyphosate-treated bumblebees’ attraction to UV light decreases, with these treated bees having no preference between UV light or an alternative color. Additionally, control bees who experienced electric shocks when paired with blue wavelengths (CS+) v. UV light always chose UV light. In contrast, glyphosate-treated bees could not differentiate between blue and UV light regardless of electric shock when in blue light. The study highlights, “Our results raise the question of whether an impairment in the detection of the sky compass could also have played a role. Furthermore, UV reflectance and UV patterns are important parameters of flower coloration, strongly influencing the foraging efficiency and flower choices of bees. To sum up, even a slight shift in UV sensitivity could have broad implications for these pollinators.”
Clean air, water, and healthy soils are integral to ecosystem function, interacting between Earth’s four main spheres (i.e., hydrosphere, biosphere, lithosphere, and atmosphere) to support life. However, toxic pesticide residues readily contaminate these spheres, frequently in soils, water (solid and liquid), and the surrounding air at levels exceeding U.S. Environmental Protection Agency (EPA) standards. The scientific literature demonstrates pesticides’ long history of adverse environmental effects, especially on wildlife, biodiversity, and human health. Most notably, pesticides are immensely harmful to pollinators. Over the last decade and a half, increasing scientific evidence shows a clear connection between the role of pesticides in the decline of honey bees and wild pollinators (e.g., wild bees, butterflies, beetles, birds, bats, etc.).
The agricultural industry relies on insect pollinators for plant pollination and crop productivity. Globally, the production of crops dependent on pollinators is worth between $253 and $577 billion yearly. Hence, pesticide use fails to support sustainability goals, decreasing agricultural and economic productivity and social (human/animal) and environmental well-being.
Almost five decades of extensive glyphosate use has put animal, human, and environmental health at risk as the chemical’s ubiquity threatens 93 percent of all U.S. endangered species. Although the direct effects of pesticides on pollinators are concerning, the indirect impacts on pollinator habitats are equally troublesome. Glyphosate use in mono-crop agriculture and genetically engineered crops can drift onto and destroy adjacent habitats. Habitat destruction results in the loss of species biodiversity and stable ecosystem processes integral to sustainability.
When looking at pesticide exposure, glyphosate represents only one class out of thousands of agrichemicals that pollinators may encounter. Pesticide use poses one of the most significant threats to bumblebees and places their entire life cycle at risk. A 2018 study found that commonly used neonicotinoid insecticides begin to kill off bumblebees during their nest-building phase, as exposure makes it more difficult for a queen to establish a nest. Exposure to neonicotinoids results in bumblebee colonies that are much smaller than colonies not exposed to these systemic insecticides. Moreover, a 2017 study finds that neonicotinoid exposure decreases pollination frequency and results in fewer social interactions. That is likely because neonicotinoids alter bumblebee feeding behavior and degrade the effectiveness of bumblebee’s classic “buzz pollination” process. Research published in 2017 determined that fungicides also play an essential role in bumblebee declines by increasing susceptibility to pathogens. Moreover, EPA assesses the toxicity of individual active ingredients on bees through various testing methods when regulating pesticides. However, EPA does not require the testing of multiple active or inert ingredients to the same degree, despite evidence demonstrating these chemicals harm pollinators.
While it is evident that factors like pesticides, parasites, habitat destruction, and poor nutrition contribute to the decline of the American bumblebee, the combined stressors can act together (synergistically) to increase the risk of bee mortality.
The study shows chronic exposure to glyphosate can reduce bumblebee’s ability to connect aversive stimuli like an electric shock with visual indications when partaking in learning tasks. The inability of bumblebees to learn these warnings puts these pollinators at risk of predation and disease when looking for food. However, this study only adds to the scientific literature on the adverse effects of chemical exposure on pollinator health, especially in sublethal concentrations. A lack of fine-color discrimination skills can threaten bumblebee survivability through a decrease in colony fitness and individual foraging success. Much research attributes the decline of insect pollinators (e.g., commercial and wild bees and monarch butterflies) over the last several decades to the interaction of multiple environmental stressors, from climate change to pesticide use, disease, habitat destruction, and other factors. In the U.S., an increasing number of pollinators, including the American bumblebee and monarch butterfly, are being added or in consideration for listing under the Endangered Species Act, with specific chemical classes like systemic neonicotinoid insecticides putting 89% or more of U.S. endangered species at risk.
Furthermore, this study shows the potential of a fully automated, high throughput assay for sublethal effects testing on wild and solitary bees for chemical exposure, not just honey bees. The study concludes, “Glyphosate exposure impacted bumblebee physiology and nervous system function in several ways, from sensory perception to cognition. This could result from a broad disruption of brain maturation or function. Further research will be needed to elucidate glyphosate’s mechanism of action on insect cognition, as well as to evaluate if this effect is temporary or permanent.”
Pollinator protection policies need improvements, to safeguard not only all pollinators but the crops they pollinate as well. Beyond Pesticides holds that we must move beyond pesticide reduction to organic transition and commit to toxic pesticide elimination in our agricultural system to prevent the crop loss presented in this study. Pesticide elimination can alleviate the effect of these toxic chemicals on humans and wildlife. With EPA failing to take the most basic steps to protect declining pollinators, it is up to concerned residents to engage in state and community action and demand change. Moreover, the government should pass policies that eliminate a broad range of pesticides by promoting organic land management. Habitat in and of itself may assist, but it must be free of pesticides to protect wild pollinator populations. To protect wild bees and other pollinators, check out what you can do by using pollinator-friendly landscapes and pollinator-friendly seeds, engaging in organic gardening and landscaping, and supporting organic agriculture through purchasing decisions. Learn more about the science and resources behind the adverse effects of pesticides on pollinators and take action against the use of pesticides. Buying, growing, and supporting organic will help eliminate the extensive use of pesticides in the environment. Organic land management and regenerative organic agriculture eliminate the need for toxic agricultural pesticides. For more information on the organic choice, see the Beyond Pesticides webpages, Health Benefits of Organic Agriculture, Lawns and Landscapes, and Parks for a Sustainable Future.
Learn more by registering for the virtual 40th National Forum Series, Forging a Future with Nature: The existential challenge to end petrochemical pesticide and fertilizer use, starting on September 14, 2023. Go to Forum website.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Science of the Total Environment
People have been attempting to save the bee for many, many years. No one listens. No one cares … until it’s them or their loved ones. Yet government is allowing this to happen. What will we eat once the bats, birds and bees have vanished? With the way the world seems to be going I guess each other. YUCK.
August 2nd, 2023 at 7:10 pm