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Poison Ivy: A Growing Menace in the Era of Climate Change
Sarah Joy Stauber
Lake Forest College
Lake Forest, Illinois 60045
Poison Ivy, often associated with the rhyme “leaves of three, let it be” is a plant commonly known for its ability to cause blistering itchy rashes. The oily chemical that causes contact dermatitis in 2 out of 3 individuals is known as urushiol; it is also found in poison ivy’s less common relatives, poison oak and poison sumac. For some, a mere 1 ng of urushiol can induce severe allergic reactions. Known to grow up trees and creep over the ground around forested areas, poison ivy (Toxicodendron radicans) has been becoming increasingly common in suburban areas in recent years (Ziska et al., 2007).
Figure 1: Poison ivy distribution in the United States (Jonsachs, 2016)
Many scientists agree that human production of greenhouse gases like CO2 are associated with global warming trends, as well as an increase in storm frequency and severity. Since 1900, humans have emitted nearly a 10-fold increase in carbon form fossil fuels.
Figure 2: Visual representation of carbon emission increase since 1900 (Hayhoe et al., 2018).
During the last century, Earth has already experienced rising temperatures, and depending on human behavior over the next century, they could continue rising by as much as 3.6-12°F by the year 2100. While some argue that this is primarily caused by natural drivers, research has shown otherwise (Hayhoe et al., 2018).
Figure 3: Sophisticated climate models simulating temperatures and their causes from 1880-2020. The average (black line) is calculated based on the average global surface temperature as a difference from the average value for 1880-1910 (Hayhoe et al., 2018).
According to Ziska et al., these increasing levels of CO2 can be associated with a likewise growth in poison ivy, literally. In this study, they grew Toxicodendron radicans rhizomes in a controlled environment and exposed them to different quantities of CO2 that simulated levels during the mid-20th century (300 μmol mol-1), 2007 (400 μmol mol-1), and those projected for 2050 (500 μmol mol-1) and 2090 (600 μmol mol-1). They then simulated animals (deer, rabbits, etc.) eating the plants in these groups by periodically removing leaves and measuring regrowth. Upon analysis, the researchers discovered that the increases in CO2 could be associated with similar increases in leaf, rhizome (figure 4), and stem growth, as well as increased production of urushiol. Even when leaves were removed, poison ivy plants grown in higher concentrations of CO2 still grew back larger and heavier (Ziska et al., 2007).
Figure 4: Measurements of rhizome length per plant grown with different levels of atmospheric CO2. (Ziska et al., 2007).
While poison ivy is thriving from the conditions of our changing world, many crucial organisms are suffering. According to the recently released National Climate Assessment, warming weather, changing atmospheric conditions, fires, landslides and droughts have already resulted in a significant impact on forests and croplands. As depicted by figure 5, trees nationwide have been decimated by fires and new invasive insects, in addition to forest harvesting (Vose et al., 2018).
Figure 5: Primary sources of forest disturbance across the United States (Vose et al., 2018).
Furthermore, research also indicates that crop production will diminish by the end of the century, and in some places, be almost completely decimated.
Ultimately, while forests and crops are projected to dwindle as a result of climate change, the growth of other organisms like poison ivy are expected to explode. So, don’t forget, “leaves of three, let it be.” As best phrased in the NCA4, “Climate change is altering ecosystem productivity, exacerbating the spread of invasive species, and changing how species interact with each other and with their environment. These changes are reconfiguring ecosystems in unprecedented ways” (Lipton et al., 2018).
Hayhoe, K., Wuebbles, D.J., Easterling, D.R., Fahey, D.W., Doherty, S., Kossin, J.,… Wehner, M. (2018). Our changing climate. Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. doi:10.7930/NCA4.2018.CH2
Jonsachs. (2016). Eastern Poison Ivy. Retrieved from https://www.poison-ivy.org/eastern-poison-ivy
Lipton, D., Rubenstein, M.A., Weiskopf, S.R., Carter, S., Peterson, J., Crozier, L.,… Weltzin, J.F. (2018). Ecosystems, Ecosystem Services, and Biodiversity. In Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. doi:10.7930/NCA4.2018.CH7
Vose, J.M., Peterson, D.L., Domke, G.M., Fettig, C.J., Joyce, L.A., Keane, R.E.,… Halofsky, J.E. (2018). Forests. In Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. doi:10.7930/NCA4.2018.CH6
Ziska, L. H., Sicher, R. C., George, K., & Mohan, J. E. (2007). Rising Atmospheric Carbon Dioxide and Potential Impacts on the Growth and Toxicity of Poison Ivy (Toxicodendron radicans). Weed Science, 55, 288-292. doi:10.1614/WS-06-190.1
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