In Michigan, sugar maple tree populations are rising and eastern redbud trees are making their way north while coniferous trees, like the black spruce, continue to decline.
Conservationists suspect there are a multitude of causes for this changing composition, including climate warming, and the authors of a new study say it's just shown a direct link between changing plant communities and heat.
Kara Dobson at the University of Michigan's Institute for Global Change Biology was one of the authors on this study. She said previous studies examining the link between climate warming and the effects on species were only observational.
“We wanted to look and see how climate warming specifically affects plant species in their communities and we did that using data from warming experiments,” Dobson said. “With those experiments, we're able to directly link our findings to warming specifically, versus if you use just observational data from out in nature, It's hard to kind of pinpoint what could be driving your trends.”
Plant communities in some places, including Michigan, are shifting to favor warm-loving plants over their cold-loving counterparts, said Dobson. While the state may see an overall decrease in cold-loving species in regions where they previously flourished, she said this doesn’t necessarily mean a reduction in plant biodiversity.
“Under a warmer climate, if we lose those cold species faster than the community is gaining warmer species, we could see subsequent declines in species richness or biodiversity in that community,” Dobson said. “Alternatively, we could also see that we are gaining warm species faster than we're losing cold species and that could be an example of where species richness actually increases.”
She said the study can be a tool for conservationists and land managers to consider to help them create resilient plant communities. There are some plant species which drive the change in their communities, populating faster and pushing cold-loving species out.
Whether conservationists are looking to preserve native, cold-tolerant species in a community or looking to prepare that area for climate warming, Dobson said the new research means they will have more guidance on how to do so.
Senior conservation specialist at the Nature Conservancy, Doug Pearsall, said Michiganders can already see the effects of warming on plant communities in the state.
“Sugar maple is what one might call a climate change winner in northern forests,” he said. “Whereas we’re seeing a decline in some of the conifers. Black spruce has been really declining in southern Michigan because of the warming climate presumably and other stresses.”
Eastern redbud trees, which are native to Michigan but used to only populate southern counties, have been expanding northward along with many other species as the climate becomes more suitable for them, Pearsall said.
This migration north can be alarming as warm-loving invasive species may also expand their reach. Pearsall said the Bradford pear, an invasive recently added to the restricted species list in Michigan, is one of these species.
“With the climate warming it is able to become invasive here in Michigan, where in the past it wasn't, it was more restricted to the south — and there are other species like that,” he said. “Kudzu has been slowly creeping northward over time, for example.”
Pearsall said research like this along with other resources like the Nature Conservancy’s Resilient Land Mapping Tool can inform conservation strategies like assisted migration, mentioned in Dobson’s study.
Assisted migration is the intentional movement of species to places they are more likely to thrive.
Pearsall said Michigan municipalities are already using these resources in their land management plans and can offer guidance to residents.
He also has some tips.
“If we're talking about planting and managing natural areas and backyards, native species are generally more adapted to climates and soils and provide better services for wildlife, insects, plants, insects, and birds,” Pearsall said.
