The number of butterflies migrating through California has dropped to a forty year low, according to researchers at the University of California, Davis. One-half of the usual species of butterflies have not appeared this season, and other species have been observed in very low numbers. Climate change related to global warming and habitat destruction may be the cause.
Global warming is the increase in the Earth’s average temperature over recent decades primarily attributable to human activities.
Habitat destruction is a change in land use in which one habitat is replaced with another. The plants and animals which previously used the site are destroyed or displaced in the process.
A mild winter in Northern California has caused many species to not end their winter dormancy at the right time. This means that many butterflies emerged too late in the season. The proper climate for breeding was disrupted by a wet spring.
In Southern California, an unusually dry desert left little food for caterpillars of some species to feed on. A late snow in the Sierra Nevada may have killed many insects used for food.
Some species of butterflies that breed several times a year may rebound from these events, but for other species the effects may be devastating for up to a decade.
Read the original press release here.