The benefits of climate change?

I was reading the other day on Science Daily about the positive effect of climate change on the range and population of a species of butterfly in Great Britain, the Brown Argus (left). The article stated that the butterfly had increased it's range over the last thirty years much further north than it had been previously known, all the way into Scotland.

The article then went on to explain how this extension of range had allowed the caterpillars of the butterfly to escape their usual parasites, which were not present in the more northerly habitat. Now obviously for the Brown Argus butterfly, this is largely a beneficial outcome, and as the geographic shift was allowed by warmer temperatures, at least in part due to climate change then surely this is a "benefit of climate change"?

I can't say I agree with the assessment of Science Daily that "some species benefit". If all species are affected by climate change, the likelihood of predicting the ecological impact of the changes is minimal. In this case, for example, removal of the natural predators of the butterfly also removes the selection pressure on the butterfly to resist them. This means that if interbreeding occurs between individuals from the new range and those from the old, those in the old range have an increased risk of being less fit for their environment. This kind of genetic pollution is at least possible, and at worst could result in the species becoming endangered, or even extinct in it's original range.

More disturbing a prospect, though, is the effect of the caterpillars in their new environments. With no predation, caterpillar numbers could reach much larger numbers than in their old feeding grounds, and could have adverse effects on natural vegetation, or even agricultural crops. The caterpillars may out-compete the local species of larvae, which could lead to their predators being reduced in number. This in turn could lead to serious implications in boom and bust cycles of caterpillars, and their effects on local vegetation.

There is simply no way anyone can claim that an increase in population of any single species is a benefit, no matter what it's cause. All change may be either good or bad, but without appropriate analysis, there is no way to predict which.