14 August 2007
Alpine Butterflies Getting Squeezed Out
by Kate Melville
The warming climate is expanding forests in the Canadian Rocky Mountains and inexorably isolating groups of alpine butterflies from each other, making extinction a distinct possibility, says a new study from the University of Alberta (UA).
UA's Jens Roland said the rising tree line in the Rockies due to global warming (see related articles below), and a policy not to manage growth through prescribed burns, have combined to create the increasingly tenuous environment. Alpine butterflies, like the Parnassius, inhabit open meadows because they need sunlight to generate enough body heat in order to fly, and forests are generally too shady for them and inhibit their ability to move. This effectively isolates them from their neighbors in nearby meadows.
"The risk of local extinction and inbreeding depression will increase as meadows shrink, the population sizes decrease and the populations become more isolated," Roland explained. "The gene pool of this species is getting more and more fragmented, and gene flow is reduced, which means these populations are more vulnerable."
In his paper, appearing in the Proceedings of the National Academy of Sciences, he speculates that a single particularly cold winter or summer season may be enough to wipe out an entire meadow of Parnassius. He also noted that smaller species native to Rocky Mountain meadows, including some insects and rodents, will suffer "several consequences" if forests continue to expand unchecked.
"Often forest management practice is led by the needs of larger species, such as mountain sheep, elk and grizzly bears, while the interests of the smaller species, such as butterflies, are overlooked," Roland said. "It's important to study movement among populations that are becoming more and isolated due to shrinking habitats; but, ultimately, we need to study the population dynamics to find out if the habitat allows the species to reproduce and persist," he concluded.
Source: University of Alberta