Monarch Butterflies and Climate Change
Monarch butterflies, or Danaus Plexippus, are commonly found in North America and may be found in South America, East and Southeast Asia, Australia, New Zealand, Western Europe, and some Pacific Islands. These butterflies are extremely sensitive to climate change; they migrate at the beginning of autumn, hibernate during winter, and fly back to northern regions at the start of spring. Changes in climate would greatly disrupt this pattern and cause damage in the critical stages of a butterfly’s life cycle.
A butterfly determines when to migrate based on natural changes in the environment. Currently, they are labeled as “near threatened” by climate change and are classified an endangered species, have a medium sized population, and have a medium temperature tolerance. Temperatures above 29° C would stunt a caterpillar’s growth, and if the migrating population is exposed to temperatures above 36° for a long period of time, mortality rates would significantly increase. Long-term exposure to heat could reduce a monarch butterfly’s lifespan and the number of eggs - which are laid on milkweed - a female butterfly can lay. Exposure to extreme cold is lethal to monarch butterflies and the population of milkweed. A change in temperature could also affect the parasitoid population and cause monarch butterflies to develop diseases.
Monarch butterflies are currently exposed to severe weather conditions, such as droughts, fires, heat waves, floods, freezing temperatures, and severe rain. An increase in temperature and cases of dry weather decreases the population and quality of milkweed, a source of food for monarch caterpillars. Caterpillars use milkweed as a shield due to the plant being distasteful to predators. As milkweed is the primary food source of monarch caterpillars, a reduction in the population leaves caterpillars hungry and reduces chances of survival. Scientists predict that milkweed populations would need to grow further north for ideal growing conditions, but it is unknown whether monarch butterflies are capable of adapting to the changes. If the range expanded further, then monarch butterflies would need to migrate for longer periods of time, reducing the time spent on breeding grounds.
Additionally, an increase in precipitation also reduces the amount of time monarch butterflies spend on breeding grounds. Moisture combined with low temperatures make it difficult for monarch butterflies to stay in their overwintering grounds for more than a few hours. Droughts hinder the growth of the milkweed population and other severe weather conditions are able to kill large portions of migrating monarch butterflies.
There are many ways that we can help monarch butterflies adapt to climate changes and preserve the population. One solution is to restore the butterfly’s habitat and provide stepping stones, movement corridors, and climate refugia to guide them on their migratory path. The improvements made to their habitats could facilitate resilience within monarch butterflies. The second part is to increase monitoring of changes in population range, phenology, population abundance, behavior, and the connection the changes have with climate change. The third and final step is to reduce pressure from other threats, such as the loss of milkweed and nectar sources and an increase in deforestation and herbicides or pesticides. To preserve the milkweed population, it is necessary to plant the correct type of milkweed at the correct time of year in large areas. This raises the need for backyard habitats, as milkweed can be planted in a larger range and nectar sources can thrive. The maintenance and restoration of forests and reduction in the use of chemicals in backyard habitats and forests are equally important.
Works Cited
James, David G. "Monarch Butterflies in Western North America: A Holistic Review of Population Trends, Ecology, Stressors, Resilience and Adaptation." Insects, vol. 15, no. 1, 7 Jan. 2024, p. 40. Proquest, https://doi.org/10.3390/insects15010040. Accessed 15 Dec. 2024.
"Monarch Butterflies & Climate Change." The Convention on the Conservation of Migratory Species of Wild Animals, Dec. 2024, www.cms.int/en/publication/fact-sheet-monarch-butterflies-and-climate-change. Accessed 14 Dec. 2024.
"Overview." World Wildlife Fund, www.worldwildlife.org/pages/monarch-butterflies-and-climate-change. Accessed 14 Dec. 2024.
Slyngstad, Ben. How Climate Change Affects the Life Cycle of Monarch Butterflies. United States Geological Survey, USGS, 31 May 2023, www.usgs.gov/media/images/how-climate-change-affects-life-cycle-monarch-butterflies. Accessed 15 Dec. 2024.