Pesticides Threaten Species Survival and Biodiversity

By Jenevra Wetmore

In December of 2020 the U.S. Fish and Wildlife Service determined that “listing the monarch as endangered or threatened under the Endangered Species Act is warranted.” Planting and promoting the growth of milkweed and halting the use of pesticides are both critical steps if this iconic species is to recover. (Photo: Michael J. Caduto)

When I was young my mother, sister, and I would venture out in July and August in search of monarch caterpillars. On the bank above our pond, we always found plenty of monarchs eating milkweed–the only plant they feed on. We collected a few caterpillars along with stalks of milkweed, and put them in a large glass jar with cheesecloth stretched over the top. Soon enough of the caterpillars formed chrysalises, and then–seemingly miraculously–unfurled wet wings to become adult butterflies. Many of us who grew up Vermont remember having this experience in our classrooms or home. 

Unfortunately, it is getting harder to find monarch caterpillars than it used to be. Over the past two decades, eastern monarchs have declined by more than 80%. In human terms, this would be like losing every living human in the US except those in Ohio and Florida. The US Fish and Wildlife Service estimates that there is a high probability–up to 80%– that the eastern monarch population will collapse within 50 years. Beyond the monarch butterfly, we are seeing massive decreases in other species that were once abundant. In 2019 the United Nations issued a report warning that one million species were currently at risk of extinction. Many of those species could go extinct within the next few decades. 

Why are monarchs, and so many other lesser-known creatures, disappearing? There are many answers to this question, including: climate change, habitat loss, invasive species, pollution, population growth, overutilization and exploitation. One important piece of this extinction puzzle is pollution, including the ubiquitous presence of pesticides in our environment. According to the EPA, a pesticide is any substance or mixture of substances intended for preventing, destroying, repelling or mitigating any pest. But these chemicals have impacts far beyond their intended target.

More than one-quarter of agricultural pesticides used in US are banned in other countries. This means that annually, the US uses tens to hundreds of millions of pounds of pesticides that have been banned in the EU, China, and Brazil. For example, the US continues to allow the use of neonicotinoid pesticides, despite their toxicity to wildlife. Various studies have found that neonicotinoids impair bees’ natural defense systems, limit their reproductive success, reduce their chance of survival, and are a leading cause of bee die-offs. In 2018 the European Commission banned the outdoor use of three of these pesticides because of their potential to harm bees, and France has banned an additional two neonicotinoids. The US has imposed some restrictions around their use, but has not banned them.

Pesticides not only effect pollinators, but cause harm to the smallest lifeforms, such as soil microorganisms, as well as large animals like killer whales. In response to this danger, there is a growing push to ban these pesticides or limit their use. New York is the nation’s largest city to ban toxic pesticides from routine use by city agencies. This charge was led by a group of kindergarten students, now in seventh grade, who worked for years pushing the City Council to pass the ban. With a few exceptions including areas on median strips and targeted use on invasive species, the city will now be using organic, biological land management practices. This is an inspiring model for not only our cities, but our small rural towns as well.  

If we want monarch butterflies and other threatened species to survive, we will need to take action—now. According to the Center for Biological Diversity, scientists foresee that over 1 million species of plants and animals could be facing extinction in the coming decades. The key phrase, however, is “could be.” We still have the power to make change. This is a biological and ecological imperative for other species, for the health and integrity of the environment, and for humankind. And it is a moral obligation to future generations.

What you can do:

  • Buy organic food when possible, and local food if you are able. Conventional agriculture uses harmful pesticides, which in turn damage soil health and impact insects and other animals.
  • Re-evaluate your pesticide use. Research no-till organic gardening practices and methods of naturally repelling insects.
  • Plant native milkweed and other plants for pollinators. Use to find the right plants for your area.
  • Visit to find out how you can help to preserve monarch butterflies.
  • Take political action. Visit to view national campaigns that you can support to stop pesticide use.
  • Ask your town, school, place of worship, or workplace to stop using pesticides.
  • Support locally-based organizations that are working to enhance our understanding of the natural world and preserve biodiversity through research, conservation, science education and activism, including the Vermont Center for Ecostudies, Vermont Institute of Natural Science, Montshire Museum of Science, and Sea Shepherd.


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