Climate Change Hidden Impacts Detailed In New Moth Study
April 15, 2014

Moths And The Masking Of Climate Change

Brett Smith for - Your Universe Online

A new climate change study conducted on sub-Arctic moths living in Finland has revealed mixed results: moths seem to be thriving despite a warmer, wetter climate – while an as-yet-unknown force is apparently masking the expected effects of this localized climate change.

"You see it getting warmer, you see it getting wetter and you see that the moth populations are either staying the same or going up. So you might think, 'Great. The moths like this warmer, wetter climate.' But that's not what's happening," said study author Mark Hunter, an ecologist at the University of Michigan, in a recent statement.

In the study, researchers looked at communities of 80 moth species and discovered that 90 percent were either steady or rising during the entire study period, from 1978 to 2009. Throughout the study, average annual temperatures rose 3.5 degrees F and winter precipitation increased as well, the researchers found.

"Every time the weather was particularly warm or particularly wet, it had a negative impact on the rates at which the populations grew," Hunter said. "Yet, overall, most of these moth populations are either stable or increasing, so the only possibility is that something else other than climate change — some other factor that we did not measure — is buffering the moths from substantial population reductions and masking the negative effects of climate change."

The study, published Tuesday in the journal Global Change Biology, was performed at the highly-remote Värriö Strict Nature Reserve, 155 miles north of the Arctic Circle and less than four miles from the Finnish-Russian border. The study team used light traps at night to catch nearly 390,000 moths from almost 460 species. Eighty of the most common moth species were analyzed using a statistical technique that determines how ecological forces affected population growth.

The study team said they were shocked to discover that 90 percent of the moth species in the study were in populations that were either steady or on the rise. In their report, the authors concluded, "Simple temporal changes in population abundance cannot always be used to estimate effects of climate change on the dynamics of organisms.”

"The big unknown is how long this buffering effect will last," Hunter said. "Will it keep going indefinitely, or will the negative effects of climate change eventually just override these buffers, causing the moth populations to collapse?"

He added the study could indicate that a similar mysterious masking effect is happening elsewhere for other species. If so, scientists could be underestimating the negative effects of climate change on numerous species.

"We could be underestimating the number of species for which climate change has negative impacts because those effects are masked by other forces," he said.

Finnish members of the study team said they have seen a slow increase in tree and shrub density, increased rates of tree growth and a rise in the tree line over the course of the study. Additional plant life could be offering shelter from predators and weather and the possibility that these changes are offsetting the negative effects of warmer temperatures and greater precipitation was not considered in this study, the researchers noted.