Updated: May 5
Migratory Monarch Butterflies have been put on the endangered list since June 2020
The population of Western Migratory Monarch Butterflies (MMB) has decreased by over 99% since the 1980s. That’s a massive jump from about 10 million to just a little under 2,000 left in the span of around 40 years. The Eastern population which is larger has also decreased a huge amount, 84%, according to Monarch Butterflies are now an endangered Species National Geographic.
Why Are They Endangered?
MMB are endangered due to three main causes: climate change, threats from pesticides, and urban development. It affects their migration from Mexico and California in winter to throughout the U.S. and Canada in the summer and reproduction.
MMB heavily depend on the temperature being consistent for their hibernation and reproduction. Climate change is disrupting this, it has caused their direction of migration to be northward instead of southward.
MMB need cold temperatures to keep their metabolism less demanding so they can hibernate and the high fluctuation in temperature has been ruining this. If it’s too warm they’ll be hungry and if it’s too cold they'll end up freezing to death.
It has also been preventing MMB from reproducing because high temperatures cause milkweed to grow slower and of poor quality. For more and better quality milkweed to grow, it’ll have to be planted more towards the poles but that creates a new problem. The MMB will have to migrate further, meaning they’ll have less time to lay eggs and will reproduce less.
The number of extreme weather events has been becoming more frequent and killing a lot of MMB when they happen. Even just the increase in the rain has impacted MMB because it reduces the amount of time they have to lay eggs, according to Monarch Butterflies & Climate Change.
THREATS OF PESTICIDES
Pesticides, specifically glyphosate, which is in a commonly used product called Round-Up are incredibly harmful to MMB because it kills Milkweeds. MMB has tended to lay more eggs on farms than anywhere else which wouldn’t be an issue if farmers don't use glyphosate.
Glyphosate rose in the late 90s because farmers could use it without harming their crops but it has killed all of the milkweeds that were in the Midwest.
The Midwest is important because that’s where MMB go to have their annual migration, according to Report: Monarchs, Other Species Endangered by Pesticides.
Due to logging and deforestation creating more space for buildings, it’s taken away significant shelter areas for MMB to hibernate during the winter.
This is another factor that messes with their chances of surviving the winter, according to Migratory Monarch Butterfly Now Endangered - IUCN Red List.
Why Are They Important?
MMB are both important for the environment and for cultural reasons. MMB are pollinators which means they play a role in pollinating many flowers, fruits, and vegetables. They also are essential for many ecosystems.
As for cultural reasons, MMB has significance in Mexico. They can be seen in stone carvings and paintings of indigenous groups. MMB can be seen in songs, dances, and their colors in different things. They’re also included in legends about how MMB can tie those to their ancestors, according to Monarch Butterflies Bring Together Conservation and Culture Between U.S. and Mexico.