Humans have been drawn to the beauty and metamorphosis of the butterflies throughout time. Almost everywhere butterflies have been incorporated as cultural symbols. Today, these winged insects have now also become early indicators of climate change.
A study in Melbourne, Australia, done by Dr. Michael Kearny, has reported that over the past 65 years, butterflies have begun emerging from their pupa 1.6 days earlier each decade. Like many animals, the butterflies’ life cycle is highly dependent on the temperature they are experiencing. When Kearny looked into the average temperature in Melbourne, he noted that each decade, the temperature rose approximately 0.14° C and tied the change to the increase of greenhouse gases [Source: The Melbourne Newsroom]. In order to test his hypothesis, Kearny and his associate raised 1000 caterpillars of the Common Brown Butterfly in various temperatures associated throughout the past 65 years and see if the emergence matched up to the documented numbers. According to Kearny, “…it matched extremely well” [Source: ABC News]. Shifts in seasonal cycle could directly alter the food and competition during hatching time for the species, though it is unknown whether females are laying eggs earlier than before [Source: ABC News]. In order to directly link the increase in temperature to the increase in greenhouse gases, scientists applied a general circulation models to the Melbourne region, taking into account local factors that influence climate. According to Karoly, “regional temperature changes observed over the decade were unlikely to be observed without the influence of human greenhouse emissions” [Source: ABC AU].
For other species of butterflies around the world, the increase in climate change has forced them to move further north. Over the past 35 years researchers have documented butterflies in the Sierra Nevada moving further north to escape rising temperatures. Butterflies in general are excellent indicators of global warming due to their extreme sensitivity to temperature and short life span. So for butterflies living in high altitudes, they cannot adapt quickly to the temperatures, similar to the American Pika, as they already live in extreme climates [Source: USA Today]. Even lower altitude butterflies have moved northward in Europe and North Africa. Camille Parmesan studied 35 species of the two regions and noted that 22 of those species had move northward over the past century due to the 0.8°C increase in temperature [Source: University of California]. Since butterflies are important pollinators, this shift in distribution could greatly affect plant life and something similar to the bee disappearance could happen, though the effects have yet to be studied.
One well-noted species, the Monarch Butterfly, has been listed by the WWF as a critically endangered species. These majestic butterflies are most known for their mass migration from Canada and US to Mexico. In the 1990s, the butterflies occupied an average of nine hectares of forest, currently hthey are down to 1.92 hectares [Source: Treehugger]. While the butterflies are not in danger of extinction, their mass migration and overwintering is listed as an endangered biolgical phenomenon, which states that: “the species per se need not be in peril, rather, the phenomenon it exhibits is at stake” [Oxford Journals]. Unseasonal changes in temperatures on route caused a large drop in monarch population along with habitat loss from poor land use, forest degradation and increased herbicides [Source: Treehugger].
Our fascination with butterflies has allowed us to record an very detailed history of their movement as well as their emergence. While we may not have originally studied them for the purposes of supporting global warming, the current climate concern has made us look at butterflies in a different light.