On Thursday July 21st, the IUCN(International Union for Conservation of Nature) placed the monarch butterfly on its Red List of Threatened Species under the status of endangered. After years of population declines due to habitat destruction, climate change, and pesticide use, the iconic orange butterflies are now nearing extinction. We thought it would be interesting to visualize how many butterflies are left.
The graph above shows the decline in the eastern monarchs area during its yearly migration to Mexico.
This graph shows the population of western monarch butterflies by year, according to the Xerces Society yearly count. Despite eastern and western populations having different migration destinations, the pattern is clear: their populations are declining, and fast.
What is the difference between eastern and western monarch butterflies?
Eastern and western monarch butterflies are genetically very similar. However, they have different migration paths and destinations: During winter, eastern monarchs migrate to central Mexico, a trip of about 3,000 miles, while western monarchs fly to California's coast, traveling around 300 miles.