A shrinking mountain pond in northern Maine last October starkly reveals dry late summer conditions that forest researchers say will be common by 2100. (Photos by C. Parrish)
A shrinking mountain pond in northern Maine last October starkly reveals dry late summer conditions that forest researchers say will be common by 2100. (Photos by C. Parrish)
Red spruce and balsam fir are the two key trees associated with the cold northern forest of moose, blackflies, deep shade, and logging roads that covers much of Canada and makes up the top half of the state of Maine.

But the iconic Maine north woods, which foresters refer to as the spruce/fir forest, is among the forest types most vulnerable to a changing climate, according to researchers at the U.S. Forest Service.

That provides both opportunities and challenges, according to Maria Janowiak of the Northern Institute of Applied Climate Science.

Janowiak, a U.S.?Forest Service ecologist whose role is to provide forest land managers across the Northeast with scientific information that helps them adapt forests to changing conditions, spoke at the Schoodic Institute at Acadia National Park in Winter Harbor on Monday, March 6.

Schoodic Institute, a non-profit, is the flagship scientific field research institute for the National Park Service system and is closely allied with Acadia National Park.

It’s not all bad news. Red spruce has thrived in the wetter conditions over the past few decades and carbon dioxide, a greenhouse gas that cars spew out and trees suck up as a sort of fertilizer, has increased tree growth, said Janowiak. 

But as warmer temperatures over time create conditions in northern Maine similar to what used to be found in Portland and farther south, red spruce is likely to find more favorable conditions in Canada. 

Janowiak said which parts of the northern forest thrive and which don’t depends on a variety of natural and economic factors, including whether the landowner seeks to grow valuable logs to sell to existing and future markets,  or has non-economic goals, such as creating songbird or deer habitat.

While red spruce is vulnerable, balsam fir is expected to adapt more easily to warming conditions, she said.

Janowiak summarized the climate research results on Northeast forests based on three forest impact models, hundreds of scientific papers, and two climate models: one with low greenhouse-gas emissions and one with high emissions.  

Temperatures are predicted to increase in the Northeastern U.S. under both climate models, with a range from two to eight degrees by the end of the century. While the degree of warming is debatable, the fact of it is not. Globally, the ten hottest years in the past century occurred since 1998, she said.

 

Locally, Maine has already warmed three degrees on average over the past century, with precipitation increasing six inches, according to Janowiak. Most warming happens in winter, resulting in shorter duration of lake ice, earlier flowering, longer growing seasons, and earlier migrations of some bird species.

The increased precipitation mostly comes as summer and fall rains, with more rain falling in severe storms, washing away soil. 

Longer growing seasons can provide more tree growth, but earlier flowering and water-soaked tree roots can also be susceptible to late freezes that damage or kill trees.

El Nino and La Nina weather effects may change snowfall year-to-year moving forward, so that Maine could once again have a winter like 2014, but the longer-term climate models indicate a lot less winter snow, with a 40-percent decline in December and January snowfall predicted on the Maine coast and somewhat less than a 20-percent decline in northern Maine.

 Rain and ice will likely replace it. 

Researchers predict dryer summers, resulting in drier soils that create unfavorable growing conditions for some trees.

Trees of the northern Maine forest, including red spruce, paper birch, tamarack and black spruce, will likely suffer most as the north woods warms. Trees now at the northern extent of their range — like elm, basswood, black cherry, white pine, red and white oak, silver maple, and service berry — could move in and thrive. 

Or they could be planted in advance.

Forest managers interested in commercial forestry have the option to introduce native Southerners into the mix now before red spruce and other species start to decline.

 Irving manages three million acres of forest in Maine and is a long-term industrial player. They have embraced the climate message and are researching how to adapt the forest for the future, said Janowiak.

Some forest managers are focusing on increasing forest complexity.

One thing is clear, said Janowiak: the more types of trees and associated plants, the more diverse their ages, the healthier the individual trees, and the more genetic variability in the soil — basically, the more complex a forest stand is — the more resilient it will be.