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Nature Notes: Insects at Risk

Ed Robinson
March 9, 2022

Almost daily we are presented with more evidence of significant changes taking place around the globe. The big news items often refer to global warming, the status of the ozone hole, deforestation in the Amazon and rising CO2 emissions. Close to home we regularly hear about rapid warming of the Gulf of Maine and the impact on shellfish and lobsters. In the last two years we have been confronted with shocking news about the decline in songbird populations. 

Equally serious are changes that occur out of sight, and therefore generally out of mind. You have probably read about the decline of bee populations and the rise of invasive pests like the emerald ash borer. Scientists are beginning to pay closer attention to the decline of critical zooplankton species in the ocean that affect the food chain right up to the endangered right whales. In this article I will present some information about the growing incidence of pesticides in our environment and the impacts we are beginning to understand regarding the health of insects, aquatic species and mammals. 

The startling headline is this: in a 2019 report the Journal of Biological Conservation stated that 40% of insect species around the world are declining and that as many as one third of those species are already endangered. While underreported, the authors also stated that the losses included as many as one third of aquatic insects. Unless you are inclined to study insects you might dismiss this as no big deal, but it is a very big deal indeed. Insects play a huge role in our world in a myriad of ways, many of which we have yet to fully understand. Those bees and hundreds of other insect species are vital to the pollination of flowering plants, critical by some estimates to as much as 60% of our food supply. Insects are key players in removing wastes from our environment and recycling complex compounds into basic nutrients like carbon and nitrogen. That big decline in songbird populations is directly related to the loss of insects since fledgling birds are to a large extent dependent upon insects for their early nutritional needs.  

While organic farming techniques have progressed considerably in recent years, the vast bulk of the food we eat is produced using industrial farming practices – huge farms with sophisticated mechanization and liberal application of fertilizers, herbicides and pesticides. Farmers have massive investments for which they carry heavy mortgage payments. They are driven to produce as much food as possible for a given acreage and they seek to remove variability in their crop yields, in part by limiting insect populations that may damage those crops. Competing in global markets and impacted by unpredictable weather patterns, farmers go to great lengths to keep their production costs as low as possible. While consumers consistently say they want their foods to be as nutritious and safe as possible, when it comes time to select their products at the supermarket they often vote with their wallets and choose cheaper foods that may carry chemical residues.

The upshot is that most farmers today use insecticide coated seeds and then spray their crops with additional chemicals as necessary to control outbreaks of weeds and insects. While those chemicals may boost yields and limit insect damage to crops, they have other impacts that may be widespread and long lasting for other species. An article in the Winter 2022 issue of Trout, published by conservation group Trout Unlimited, focused on one class of insecticides, the neonicotinoids. These were developed in the 1990’s to replace organophosphate and carbamate insecticides known to have dangerous side effects for mammals including humans. 

A mayfly lands on the surface tension of a still pond creating a smooth ripple.
Photo by Sean Beckett, iStock.

Unfortunately, the neonicotinoids do not discriminate in killing just one or two species of insects. As the insecticides leach into the soil, or are washed into streams and ground water by the rain, they can impact a wide variety of species many miles away from the point of application. Studies in Japan regarding the use of insecticides in rice fields showed significant impacts on crustaceans and zooplankton, and commercial losses of eels and smelt. Studies in the US found 53% of water samples from 48 different streams carried neonicotinoids, particularly in the grain belt of the Midwest. Scientists are finding that some species of aquatic insects of great importance to salmonids (mayflies, caddisflies and stoneflies) are highly sensitive to chemical contamination and when the insects die off, trout and salmon cannot thrive. 

Closer to home, neonicotinoids are found in products like the sprays used in our gardens, on the flea collar worn by your cat, even in plants encouraged for pollinator gardens. Groundwater tests in Iowa and Minnesota found the chemicals in over 70% of samples. The Trout article went on to note that municipal wastewater treatment facilities are a year-round source of neonicotinoids in discharge water. Of particular concern is that the water treatment chemicals used in those municipal plants is contributing to transforming the basic neonicotinoids to more dangerous by-products. 

It is difficult to determine how extensive the problem of insecticide pollution is around us but the numbers are significant. Looking at industry data, the Xerces Society has estimated that over five million pounds of neonicotinoids were used in just one year, 2011. Usage clearly has grown since then and it is estimated that over 125 million acres of fields are treated each year. Crops affected include corn, soy, wheat, rice, cucumbers, cotton, grapes and citrus products. It is disturbingly ironic that the chemical makers, including giants Bayer and Syngenta, label their products with names like Malice, Venom, Scorpion and Assail. Unfortunately, we are as much at risk as the target insects. 

The Trout article relates the story of an organic farmer who could not understand why his grain crop failed chemical tests necessary for him to export to European markets. He had long steadfastly refused to use treated seeds, herbicides, insecticides or fungicides. After checking his irrigation system, his planting and harvest equipment he could find no reason for the contamination that caused the test failure. Then he tested rainwater falling on his fields and found it contained residues of glyphosate, the chemical more commonly known as RoundUp. 

Evidence is mounting that potentially dangerous insecticides and other chemical classes are accumulating in our environment just as they are accumulating in our food and our bodies. Whether the eventual damage is the loss of delicate mayflies in a tributary of the Androscoggin River, reproductive problems in northern leopard frogs, or fewer lightning bugs on a summer evening, there is a price to be paid for ongoing additions of persistent synthetic chemicals to our environment. 

In the last few decades environmentalists and academic researchers have pushed back on the chemical industry, farmers and government officials who are responsible for the manufacture, application and regulation of insecticides. There are literally thousands of agricultural chemicals in use around the world for which relatively little scientific testing has been done to fully characterize their impact not just on the intended target insects but also broader ecosystems and the full range of creatures within them. The US Environmental Protection Agency (EPA) has been under pressure to improve the licensing and regulation of pesticides but they have a long way to go to meet their obligations even under current legislation. As one example, the EPA has a deadline of October 1 to evaluate over 1,000 licensed pesticides coming up for their 15 year renewals but the EPA will not meet that deadline.

Historically the vast majority of data used by EPA to evaluate a potential new pesticide has come from the manufacturer of the product in question. While the EPA sets the requirements for that data, it would not be surprising to find that the manufacturers would do no more testing than necessary before filing for approval. The focus of that testing has typically been the target insect, for instance, a corn borer or cotton weevil. But the federal Endangered Species Act requires the EPA to consider, in consultation with other federal agencies, the potential harm to other species, particularly those listed as endangered or threatened and living in the same area as the target insects. According to a February 28, 2002 article in Chemical and Engineering News, the EPA has chronically failed to take such steps unless forced to do so in response to lawsuits filed by environmental groups. 

Finally, the EPA has taken steps to hire more staff for these reviews and intends to work with the US Fish and Wildlife Service (FWS) and the National Marine Fisheries Service (NMFS). If it appears that a new pesticide poses a threat to endangered species, the EPA would insist on mitigation steps before the pesticide could be licensed. That will shift the spotlight to FWS and NMFS, both of which are also lagging in their studies. There is the need for all of the agencies to agree on study protocols and benchmarks for consideration. As one example, when the agencies reviewed the risks of the insecticide malathion, used for mosquito control, FWS stated the product was dangerous for only five percent of endangered species while the EPA stated it would impact nearly all endangered species. 

While we need to focus on the potential loss of insects and other species due to insecticide usage, there are serious considerations for humans as well. The short-term effects of exposure to these chemicals can include irritation of the nose, throat, eyes and skin. Nausea, dizziness and diarrhea may follow. Some people are highly sensitive to insecticides including young children and asthma sufferers. Long term effects from ongoing exposure may include brain and nervous system damage, birth defects, reproductive problems, organ damage and various cancers. Clearly it behooves us to understand these chemicals before we apply them and to take proper precautions to protect human health. 

Many of us are concerned about growing human health issues like food allergies, autism, dementia and cancer. The US Centers for Disease Control and Prevention (CDC) reports that diagnoses of autism spectrum disorder grew from 6.7 out of 1000 eight-year-old children in 2000 to 23 out of 1000 in 2018. Over half of those diagnosed have significant issues with gastrointestinal illness. Diagnosed food allergies have risen from three percent of the world’s population in 1960 to seven percent in 2018. There were an estimated five million patients with dementia in 2014 but that number is estimated to reach 14 million by 2060. In 2018 there were more than 18 million new cases of cancer worldwide but that is estimated to exceed 29 million by 2040. Doctors and researchers have been struggling for years to identify the causes behind these trends but there is growing evidence that the foods we eat and the chemicals to which we are exposed during our lifetimes may be part of the problem. 

In one response to the concerns highlighted in this article, Maine Audubon has begun looking at insect populations in our state and building partnerships with groups that have useful historical data. The Maine Entomological Society is involved and the Maine Outdoor Heritage Fund has committed funding to support the project. A preliminary review of limited data available from the Department of Inland Fisheries and Wildlife pointed to recent declines of dragonflies, butterflies and hoverflies but much more work is needed. Audubon expects to engage citizen science volunteers in the patient work of gathering data over time. Let us hope that we can get our arms around the problems before they have mushroomed beyond any hope of mitigation and control.