Sunday, March 21, 2010

This is your wake up call

A study to be published in Biology Letters out of the University of Melbourne reports that the mean emergence date for adult Common Brown Butterflies (Heteronympha merope) has shifted 1.6 days earlier per decade. That means that over the course of this 65 year study the emergence date is over 10 days earlier. This shift in date was found to be simulaneous to the increase in air temperatures around Melbourne (about 0.14°C per decade).

Now this might not sound like a huge deal. I mean, its only 10 days. Well, can you go 2 weeks without food? In a story like this one you always have to think about what else is affected. Here, the shift in dates potentially alters things such as food (the butterflies eatting and being eaten) and competition.

Additionally, the researchers raised caterpillars of the Common Brown Butterfly in the lab. In this setting they were able to control for the various environmental factors (such as temperature) and measure the impact on the butterflies' rate of development. Then they modeled the results to observe the effect of historical climate trents on the rate of development. With this model they were also able to use global climate model outputs for Melbourne over the time period of the study to test whether what they were observing in the field was due to human influence on climate or natural temperature variations. The work was able to very strongly tie the date shift to temperature increases that, in turn, were tied to human-caused greenhouse gas increases.

Here's the article:
and here's a write-up in Science Daily:

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