The tragic driver behind monarch decline

Studies suggest that neonics are a likely driver of the precipitous monarch butterfly decline and highlight the threat they pose to a wide range of species and ecosystem services.

Studies Link Neonicotinoids to Monarch Butterfly Collapse

The Pollinator Stewardship Council has long been advocating for a ban on the outdoor use of neonicotinoids (neonics), highly toxic pesticides with documented harmful effects on bee colonies. Studies also suggest that neonics are a likely driver of the precipitous monarch butterfly decline and highlight the threat they pose to a wide range of species and ecosystem services (Goulson 2015; Jeschke et al. 2011). Neonics were commercially introduced in the early 1990s and have since become the most widely used pesticides in the world. Neonic-treated crops now cover nearly 150 million acres of American farmland – an area about the size of Texas (Tooker 2018). A recent study finds that U.S. agriculture is “48 times more toxic to insect life than it was two decades ago” and that neonics “account for 92 percent of the increase in toxicity” (DiBartolomeis et al. 2019). In that same period, North American monarch populations have declined by nearly 90 percent since the introduction of these pesticides, sinking to an historic low in 2018 and prompting a petition to list them as a threatened species under the Endangered Species Act (FWS Report 2020). 
Research has demonstrated that neonics are extremely poisonous to monarchs. Exposure to neonics can result in symptoms ranging from reduced size, limited wing length, impaired directional ability and paralysis to death (Krishnan et al. 2020). Neonic-coated seeds, which account for the bulk of neonic use, are not considered a ‘pesticide application’ by the Environmental Protection Agency, effectively exempting them from federal pesticide laws and allowing them to avoid compliance with mandatory safety standards. This must change. The migratory monarch population is facing potential extinction. A recent report on monarch populations considers “the effects of insecticides to be the primary driver in monarch population impacts due to pesticides” (FWS Report 2020). In the face of this emergency, and of mounting evidence linking neonics to migratory monarch death and decline, the Pollinator Stewardship Council calls for an immediate ban on the outdoor use of neonics in the United States.
The pine forests of the mountains of central Mexico are unrecognizable in winter. The oyamel firs shiver with butterflies, tens of millions of them alighting on trees in clusters of rustling black and orange, seeking warmth and protection during the cold months. This striking phenomenon – the only one of its kind in the world – may not exist in thirty years (FWS Report 2020). The extreme and rapid decline of the monarch population has been impossible to ignore. Scientists have typically hypothesized that the collapse of monarch numbers is due to the deterioration of their milkweed habitat, which has been devastated by the widespread use of herbicides in large-scale agriculture. The migratory monarch has a very particular breeding cycle. In order to complete the transcontinental migration, several generations of monarchs must reproduce in one season. Monarch larvae feed exclusively on milkweed before they pupate into a chrysalis, to later emerge as a butterfly. The expansion of weed-free cropland has destroyed milkweed habitats across the country and research suggests that neonic contamination of remaining milkweed habitats is a likely a cause of monarch decline.
Nearly all neonics currently in use are applied via seed coating – a method which farmers find attractive because it is preemptive, requires no further action on their part, and protects the plant for months (Jeschke et al. 2011). The seed-coating approach anticipates a pest which has not yet arrived. It runs completely counter to established principles of integrated pest management, which are predicated on minimizing pesticide use, applying pesticides only when necessary, and avoiding broad and persistent compounds (Metcalf & Luckmann 1994).  Neonics are absorbed into a crop plant’s system, rendering the entire plant – root, stem, pollen, nectar – toxic to all insects, pests and pollinators alike. But for the average coated seed, only 2-5 percent of the active neonic ingredient is taken up by the crop.  The rest remains in the ground (Goulson 2013). Neonics are water-soluble and leak into groundwater, bleeding far beyond field boundaries, contaminating water supplies and nearby plants. They have a half-life of up to three years, and persist and accumulate in soil. Moreover, studies have found that while neonic-coated seeds lead to extensive environmental contamination, they provide no net income benefit to farmers (Mourtzinis 2019). The use of neonic-coated seeds, in the words of one study, “has no place in sustainable agriculture” (Sánchez-Bayo 2019).
Neonics do not remain in the field: they leach and spread into surrounding vegetation that is often a key habitat for non-target species – including migratory monarchs. One study asserts that “most organisms inhabiting arable environments will be exposed” to them (Goulson 2013). They have already been associated with the decline of dragonflies in Japan; butterflies in Europe (Gilburn et al. 2015); and butterflies in California’s Central Valley (Forister et al. 2016). The agricultural belt of the Midwest – where neonic use is the highest in the country – is the breeding range for approximately 38 percent of the eastern monarch population. Data is relatively limited, but early evidence suggests that all milkweed growing in agriculture-heavy areas is likely contaminated, and contains on average 1.4 parts per billion of active neonicotinoid (Pecenka and Lundgren 2015). Sublethal effects of neonic toxicity are documented in monarchs at exposure to less than one part per billion. 
A number of recent studies have examined the effects of neonics on migratory monarchs, and have clearly found that neonic exposure is associated with stunted growth, impaired development, and death. In one study, larvae raised on highly concentrated neonic-treated milkweed were unable to pupate and all larvae died within three to four days. The larvae had grown adult features but their wings had never budded (Krishnan et al. 2020). At lower concentrations, 70 percent of the larvae died and surviving larvae were substantially underweight. Another study tested neonic exposure at field-realistic concentrations of 23.5 parts per billion; monarchs exposed to neonic-treated milkweed were nearly four times as likely to die than monarchs that had ingested uncontaminated milkweed (James et al. 2019). The researcher noted that prior to death, the butterflies showed signs of severe poisoning, “uncontrollably flapping their wings and vibrating their bodies”.
Neonicotinoids are a neurotoxin. They are extremely poisonous to insects in minute quantities – ten thousand times more toxic than DDT – and permanently bind to receptors in insect nervous systems, causing convulsions, paralysis, physiological damage, and death (Halsch et al. 2020). A groundbreaking study recently determined that the toxicity of neonicotinoids increases not only with dose or concentration, but also with exposure time, in what is known as “time-cumulative toxicity” (Sánchez-Bayo et al. 2020). Their research explains why monarchs don’t always die immediately, but often after prolonged exposure to neonics. The effects of neonic toxicity are chronic and often delayed – a characteristic which has allowed them to elude scientific scrutiny for decades, but which make them no less lethal. The researchers conclude that the use of neoninicotinoids is incompatible with the imperatives of biodiversity protection, environmental conservation, and ecologically sound pest management. 
There is abundant scientific evidence linking neonic use to monarch butterfly decline and all efforts to rehabilitate the monarch population will be ineffective without an immediate ban on the outdoor use of neonicotinoids. Persistent, systemic, and broadly toxic poisons like neonicotinoids cannot be used safely without destroying species populations and impacting ecosystems in ways we do not yet understand. We are now witnessing the legacy of decades of unregulated neonicotinoid use. The regulations in place today are simply inadequate and have not prevented catastrophic damage to our environment, to species biodiversity, to our food security, and to the monarch population. The European Union, in recognition of this urgent imperative, banned their use in 2018. Regulatory bodies in Canada are preparing to limit neonicotinoid use. 
The near-collapse of the migratory monarch population represents a serious and unnecessary regulatory failure.  It also represents a serious opportunity to take action, to remedy considerable ecological harm rather than leave a legacy of contamination and extinction. Is this the legacy YOU want to leave for your children and grandchildren?  We must make the monarch migratory path safe for monarchs again by banning neonics. By banning the outdoor use of neonicotinoids, we will be more in step with a changing world – one in which we take seriously our role as stewards of our environment. Help us ban neonics and save migratory monarchs from extinction today!  
Join our call to ban neonics and to save migratory monarchs.
Donate to the PSC by clicking here. 
100% of donations will directly fund action towards banning neonic use.

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