Warmer climate, ash borer change St. Louis County tree optionsYou can’t order an ash tree any more from the South St. Louis County Soil and Water Conservation District, thanks to the discovery in Superior this summer of the deadly emerald ash borer.
By: John Myers, Duluth News Tribune
You can’t order an ash tree any more from the South St. Louis County Soil and Water Conservation District, thanks to the discovery in Superior this summer of the deadly emerald ash borer.
But for the first time ever you can order white oaks, cottonwoods, hackberry, black cherry and red cedar — all trees our grandparents said would never grow in the Northland but which now may thrive thanks to rising temperatures.
While the district sells almost all local, native species, there’s also a growing movement to plan ahead and make sure trees planted now will thrive in the future climate of the region.
The 2014 native tree and shrub sale will feature “five new tree species common just to our south, and heading our way with gradual warming trends,” the conservation district’s recent newsletter notes. “We’re looking ahead to the changing ecology of northern Minnesota.”
Lisa McKhann, program specialist for the conservation district, said state conservation leaders participated in a Web conference in recent months, where experts explained what warmer-climate species might do better as some cold-climate species begin to decline.
“We went with trees off that list of what might thrive in the future here, but also ones that are probably already here to some extent or are pretty close,” McKhann told the News Tribune in an interview. “They are also species that we can get from nurseries, trees that are available.”
Kelly Fleissner, Duluth’s maintenance operations manager, who oversees Duluth’s forestry, said the city is planting several varieties of oak as well as basswood when replacing boulevard or other dead or diseased trees. But officials also are planting hackberry, a southern species, and are even looking at a tree called Kentucky coffeetree.
“We’re starting to take a look at species that we probably wouldn’t have years ago. But now, with our warming climate we can probably do well with,” Fleissner said.
That growing zones have been changing as our climate warms is not new. In 2012 the U.S. Department of Agriculture released its first new zone hardiness map since 1980, with a clear northward migration of southern zones. The new map reflected temperature data from the 1980s to 2005, with the early 1970s dropped off, which reflects higher average temperatures for many months in many areas.
The zones moved, for the most part, because the lowest winter temperatures, which can freeze less hardy species, aren’t as low any more for many areas.
The average winter temperature (December-February) in Grand Rapids, for example, rose from about 9.5 degrees 30 years ago to 12.5 degrees by 2010. (Areas immediately adjacent to Lake Superior did not move zones because of the already warming influence of the big lake.)
Climate and tree experts warn against getting too crazy on planting — no banana trees just yet — because we still will see very cold spells and some long winters. But species that once were limited to the southern half of Minnesota probably can make it in the north now.
Because emerald ash borer are likely to quickly spread into Northeastern Minnesota from their stronghold across the bay, and because the Chinese-native pest is so lethal to all native ash trees, the conservation district as well as other tree experts say there’s no point in planting any additional ash in the region.