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ScienceDaily (Mar. 19, 2010) -- Butterflies are emerging in spring over 10 days earlier than they did 65 years ago, a shift that has been linked to regional human-induced climate change in a University of Melbourne- led study. The work reveals, for the first time, a causal link between increasing greenhouse gases, regional warming and the change in timing of a natural event.

The study found that over a 65 year period, the mean emergence date for adults of the Common Brown butterfly (Heteronympha merope) has shifted 1.6 days earlier per decade in Melbourne, Australia. The findings are unique because the early emergence is causally linked with a simultaneous increase in air temperatures around Melbourne of approximately 0.14°C per decade, and this warming is shown to be human-induced (anthropogenic).

Lead author of the study Dr Michael Kearney from the Department of Zoology, University of Melbourne says the findings could help our ability to forecast future impacts of climate change on biodiversity.

"Shifts in these seasonal life cycle events represent a challenge to species, altering the food and competition present at the time of hatching. Studies such as ours will allow better forecasting of these shifts and help us understand more about their consequences," says Dr Kearney.