“Hosts for the blacklegged tick (Ixodes scapularis) include mammals, birds, and reptiles. When feeding, infected ticks transmit the bacterium that causes Lyme disease (Borrelia burgdorferi) to humans and animals.” Photo credit: Centers for Disease Control/Jim Gathany.
It is tick season. Most Vermonters know to spray themselves with repellent before going out, wear protective clothing, and do regular tick “checks.” This message has become second nature to those of us who spend time outdoors, but it wasn’t always this way. I grew up in Hartland, Vermont, and had a tick-free childhood. Most of us who have lived here since the 1990s can say the same. What happened? Though the full response to this question is more nuanced, the simple answer is: climate change.
Ticks love warm weather, and climate change is making Vermont winters shorter and warmer. Vermont’s average annual temperature has gone up by 2.6 degrees Fahrenheit since 1895, and Vermont winters are warming faster than our summers. Since 1960, summers have been warming by .4 degrees per decade, while winters have been warming by .9 degrees. Rather than be killed off by the cold, ticks are surviving year-round. Ticks are not active when the temperature falls below freezing so, as winters warm, tick activity increases and the season when they are active lengthens. This means more opportunities for humans and other animals to come into contact with them.
There is medical proof of our growing tick problem. In the early 1990s, reports of Lyme disease were rare, but in 2025, Vermont reported 2,226 probable cases of Lyme disease, with 323 of those cases occurring in Windsor County. Most of those cases were reported in the month of July. The blacklegged tick, commonly referred to as the “deer tick,” is responsible for nearly all (99%) of cases of tick-borne diseases in Vermont. According to VT’s Tick Pathogen Surveillance Report covering the period between 2018 and 2022, over half of all blacklegged ticks tested were infected with at least one pathogen, and Lyme disease was the most common.
When we think about climate change, we often think about the possible future effects—rising sea levels, hotter temperatures, and more extreme weather events, to name a few. While these dangers are very real (and happening as you read this column), they can make it easy to miss the effects of climate change that are already here in plain sight. In Vermont, ticks are one of the signs of global warming that we have become somewhat accustomed to. Children today will never know a spring walk in Vermont’s woods without ticks.
Climate change is a slow-onset disaster, which is a term used by the United Nations to describe environmental degradation processes such as sea level rise and droughts. “Slow-onset” is not to say that climate change is not dangerous or an imminent threat, but rather to distinguish climate change from rapid-onset disasters such as hurricanes and floods. When Tropical Storm Irene hit our state in 2011, we were able to see the washed-out roads, flooded houses, and massive erosion. This was a rapid-onset disaster with an emergency response. It is more difficult to see the larger patterns caused by climate change, including warmer average temperatures, more intense storms, less snow cover, and shorter winters. We are living in the midst of a climate emergency, but it can be easy to forget. Only when we step back to look at a larger timescale can we fully appreciate the catastrophe that global warming is, and will become.
Think back to the Vermont of your childhood, or ask elders what changes they have noticed. In addition to ticks and warmer winters, we have already seen the range of some species expand northward, such as the possum–an animal my grandmother never encountered until late in life. Red-bellied woodpeckers and Carolina wrens, once a rare sight, are now common. These are changes I would not have been aware of if not for the elder Vermonters in my life. This will be our role in the future–to act as a living memory of changes in the landscape, and to advocate for policies and daily actions to reduce carbon emissions and mitigate climate change.
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WHAT YOU CAN DO:
• Visit the CDC website for precautions you can take to prevent tick bites and Lyme disease: https://www.cdc.gov/ncezid/dvbd/media/lymedisease.html
• To monitor the distribution of ticks in the state of Vermont, the VT Agency of Agriculture offers free identification of ticks. Learn more here.