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Scientists Find Unexpected Response to Climate Change in Northern Moths

US Forest Service

Fairbanks, AK - The world’s northern-most moths may be dealing with a changing climate more effectively than some scientists expected.  In fact, they may be surviving rising temperatures better than their southern counterparts. That’s according to a study out Tuesday in the journal Global Change Biology.

There are lots of moths in the forests of the far north. “You have to look a little close and care a bit to notice,” says Matt Ayres.  He is a biology professor at Dartmouth College in New Hampshire.  He admits moths, or Lepidoptera as they are known generally in Latin, are pretty non-descript.  “Most of them are brown or gray moths as adults.  But there are lots of them.  They exceed in biomass the moose and other things that you may be familiar with in plant eating animals.” As caterpillars, Lepidoptera are voracious plant-eaters.  They’re also a main source of food for birds.  As moths, they are nocturnal, so bats like to eat them too.  Because of their abundance and diversity, Ayres says they’re prime candidates for climate change research.  He and colleagues looked at long-term data for more than 300 species of moths in Finland.  They found widespread response to rising temperatures. “We also found that they didn’t all respond uniformly," explains Ayres.  "Some species fly at the same calendar day each year, regardless of temperature, probably because they’re controlled by how long the days are - the photo-period.  And some have a mix of those two control systems.  And some seem to have some control systems that we don’t know what they are yet.”

Ayres says the most surprising results involved the farthest-north moth populations. “We found that the northern species were actually somewhat less sensitive to the temperatures than southern species.  Although the timing of their biology also changes a lot from warm years to cold years, not by as much as if they were the southern population.”  Essentially, the northernmost moths are buffered from the effects of rapid climate warming.   Initially, Ayres says the research team expected the opposite response, but he’s since given the results some thought.  “It makes sense to us now, even if we were surprised initially.  At high latitudes where temperatures are frequently cooler, there’s strong selection for organisms like caterpillars to be able to accomplish more metabolism at relatively low temperatures. ”

The team used information from a unique monitoring database run by the Finnish Environmental Institute.  “It’s called Nocturna, which is now a 20 year program," Ayres says.  "It’s a moth monitoring scheme, with a network almost 100 forest sites, distributed over the length and breadth of Finland, which extends form about the latitude of Anchorage to about Barrow, so it’s a good match with Alaska.” Nocturna involves a large network of volunteers who use black lights and stale beer to trap, identify and count Lepidoptera.  Ayres says the next step is to find out how other organisms might respond to climate change.
“Now we want to know even more than before," he says.  "We don’t know of comparable insect data that could be brought to bear on this yet.”

He’s not sure if studies already exist that compare temperature sensitivities among plants in the north.  Ayres says he’d be interested to compare patterns among Lepidoptera species and plants they might feed on to find out how climate change might affect those relationships. The research done by Ayres and colleagues appears in the latest issue of Global Change Biology. It was funded by Finland’s Joensuu University Foundation.