3:15 PM EDT, September 6, 2013
Ginkgo and silver maple, yes. Norway spruce and American linden, no.
Those are among the answers the Chicago Botanic Garden came up with recently when it wondered, through the mechanism of a scientific study, which of its trees will do best under global warming.
The 385-acre horticultural haven in Glencoe is replacing its 400 ash trees, which are succumbing not to climate change but to an invasive insect species, the emerald ash borer.
Woody plants curator Andrew Bell thought it made sense to ask which trees the institution should plant in their place in expectation of the area's climate heating up.
"By 2050, 20 percent of the trees that we modeled will no longer be suitable for growing in the Chicago region," Bell said, and by 2080, 80 percent become unsuitable. "Our plant palette will probably change drastically if we don't make changes to the way we live."
Of about 50 trees analyzed under a global warming scenario used by scientists internationally — looking at key factors including mean and maximum temperature, annual precipitation and driest-quarter precipitation — 10 will no longer thrive in the region by midcentury. They are: American linden, Amur maackia, Black Hills spruce, Greenspire linden, ironwood, Katsuratree, Norway spruce, Sargent cherry, Serbian spruce and shagbark hickory.
In 2050, the American linden, for example, will have 42 percent less suitability to the area climate, expected to be 7.2 degrees warmer than currently, the study found, while the Autumn Gold variety of the ancient ginkgo tree will be 14 percent more suitable.
"The real concern," Bell wrote in a blog post about the study, "sets in when we look at the data for 2080, which projects that only 11 of the initial trees would continue to do well in Chicago and the Upper Midwest."
Those looking for a canopy that will thrive even in 2080 should consider Accolade elm, Autumn Gold ginkgo, Autumn Blaze maple, Bloodgood planetree, Chinese juniper, Eastern red cedar, hardy pecan, Persian ironwood, silver maple, Valley Forge American elm, and Village Green Japanese zelkova.
The full list is at chicagobotanic.org/plantinfo/tree_alternatives.
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