“If you think back a few decades ago and feel like winters were colder, the plant hardiness zones would suggest that’s right,” said Susan Erich, an agriculture professor at the University of Maine.
Hardiness zones, calculated by the U.S. Department of Agriculture using the average lowest winter temperatures, have been moving north in recent decades. In the latest update in 2006, much of central and southern Aroostook County moved from zone 3 to zone 4, based on data going back to 1976.
They’ll probably keep moving in the coming decades, said Erich, one of several researchers at a recent conference in Presque Isle organized by the Aroostook Band of Micmacs. By 2100, climate scientists expect a five to 10 degrees Fahrenheit increase in average temperatures — with a host of changes for farms, forests and other ecosystems, as well as the people of northern Maine.
While 10 degrees may not seem like much, “Maine could look like Connecticut, or by the end of the century, New Jersey, heaven forbid,” said George Jacobson, a UMaine biology professor emeritus.
Studies and historical writings suggest that growing seasons have grown longer in northern Maine and elsewhere, according to the UMaine Climate Change Institute, and local researchers are finding wildlife in migration. University of Maine Presque Isle biologist Jason Johnston is leading a Birds Moving North study following species at the northern end of their range in Aroostook County, such as the wood thrush and cardinal.
Erich, who specializes in soil science, said that farmers in northern Maine should expect more of what they’re used too — unpredictability.
“Changing, erratic conditions aren’t anything new for farmers,” she said. “What’s new is the expected trend of warmer, slightly wetter weather, and the potential impacts.”
Warmer weather bodes well for warm crops like tomatoes, pumpkins and squash, but may be a “mixed bag” for many crops.
Long cold winters have usually been an advantage for potato farmers, with frigid temperatures keeping populations of a range of insects, bacteria, funguses and other pests under control — especially for seed potato growers, who sell to farmers in other states.
Maine berry growers, including Circle B Farms in Caribou, are increasingly on the watch for the spotted wing drosophila, a fruit fly from Asia that’s relatively new to northern New England. The fly leaves its larva inside berries and is proving that it can survive Maine winters.
Maine sheep and goat farmers are also concerned about the barber pole worm, a major ruminant parasite that causes anemia and loss of blood. The stomach parasite normally doesn’t survive the cold winters typical of northern Maine, which has been a benefit for fiber farmers, Erich said.
Across Maine, a state that’s home to many kinds of ecosystems within a relatively compact region, there will be many local adaptations to the warming weather, said Jacobson, the professor emeritus, who helped start UMaine’s Climate Change Institute.
“We have a tremendous amount of variation within our small state,” he said, noting the range of coastal and inland regions within four degrees of latitude, over some 300 miles north to south.
“We have the same range of climate conditions here as occur from southern Poland to northern Finland in 20 degrees of latitude,” over more than 1,300 miles. It’s also the same as from northern North Dakota to northern Kansas, over 650 miles, Jacobson said.
Along with research into the human causes of climate change and the warming trends, there also scientists looking back in the geologic record to understand what the future might be like, said Jacquelyn Gill, a UMaine paleo-ecologist and assistant professor.
“We have a series of natural experiments,” Gill said. “We might not notice the difference. The planet notices.” Ten degrees F is about the difference between average global temperatures today and during the last ice age that ended around 12,000 years ago, she said.
Fossils from 35 million years ago, during a rise in global carbon dioxide and temperatures similar to projections for the next century, show plants moving north and with “massive increases in insect damage,” Gill said.
“We don’t know if that’s because the heat and the CO2 changes the physiology of the insects, or increases the nutrition of the leaves and makes them more attractive to insects, or if climate change caused new insects to move into the area and the plants didn’t have time to respond.”
But the insects’ collective feasting on plants suggests that one potential agricultural benefit of climate change — more carbon dioxide acting as a fertilizer for plants — may come with other costs.
Despite many unknowns, said Gill, one lesson from studying the evolution of the climate and its impacts is that nature is always changing.
“The idea of a baseline becomes very fraught when you start to look at change through time,” Gill said. “People often say, well, ‘Let’s bring the environment back to what it was like before Europeans arrived.’ But there’s also a lot of change that has gone on for thousands of years before.” It was only within the last 1,000 years that boreal trees like spruce and balsam fir expanded south into modern-day Maine, Gill said.
For the Aroostook Band of Micmacs, climate change in their homeland of northern Maine and eastern Canada is not new, said Simon Nevin, the tribe’s cultural director. Adapting to climate change is something that tribal members are thinking about, including in the potential uses of their forestlands.
“We believe that the earth comes in cycles,” said Nevin said at the conference. “It’s like the seasons. We went through the ice age, and that was our winter. We went through spring, and now we’re headed into the summer.”
