How Insect Pests React to Climate Change: Museum Specimens Reveal Future for Trees

Climate change is affecting species across our globe. Yet to find out exactly how changing temperatures might impact animals, scientists are taking a look to the past. They've examined century-old museum specimens in order to learn how global climate change will affect a common insect pest that can weaken and kill trees.

"Recent studies found that scale insect populations increase on oak and maple trees in warmer urban areas, which raises the possibility that these pests may also increase with global warming," said Elsa Youngsteadt, one of the researchers, in a news release. "More scale insects would be a problem, since scales can weaken or kill the trees they live on. But cities are unique, so we wanted to know whether warming causes scale insect population explosions in rural forests, the way it does in cities."

In order to find out how these insects might be influenced by the changing climate, the researchers examined more than 300 museum specimens of red maple branches that were collected between 1895 and 2011 in rural areas of North Carolina, South Carolina and Georgia. They evaluated the scale insect remains attached to each specimen, and then estimated scale population density and compared it to the temperature of each year.

So what did they find? It turns out that scale insect populations weren't as dense in rural areas as they were in the city. In addition, scale insects were more populous during warm historical time periods.

The scientists then examined 20 sites where historical specimens were collected and sampled the modern scale insect populations. They found that scale abundance had increased at 16 of the 20 sites.

"Overall, we found a total of about five times more scale insects in 2013 than on the historical specimens from the same locations," said Youngsteadt. "The urban and historical data are so well-aligned that we can view scale insect populations in cities as a preview of what to expect elsewhere."

The findings reveal that these insects may just be a problem if temperatures continue to warm. This could spell disaster for trees in the future.

The findings are published in the journal Global Change Biology.