According to the World Wildlife Fund, butterflies like the monarch have been decreasing in population due to climate change. This decrease is evident in areas like Canada and Mexico.
The WWF's 2013 report showed that monarch butterflies wintering in Mexico have decreased to a 20-year low. The lower migration rate stems from the death of adult butterflies during the summer in the United States, caused by abnormal rainfall. More butterfly deaths translates to less plant food for caterpillars. The WWF also cites that herbicide use on the milkweed plant has reduced the monarch's primary food source. Although it considers the butterfly population to be an issue, the WWF classifies butterflies as only near-threatened. Similarly, the U.S. Fish and Wildlife Service's 2008 report on the Karner blue butterfly indicated threats of habitat degradation driven by commercial development, grazing and illegal collection. To mediate the reduction, the Fish and Wildlife Service federally listed the Karner blue butterfly as an endangered species in 1992 and supported their reintroduction into the wild from zoos. Additionally, the WWF supports tree nurseries that help restore Mexican forests to maintain monarch populations. Local populations have assisted in preventing deforestation; 2012 was the first year in which no illegal logging was conducted.