This article was published in the January 2007 Minnesota Sustainable Communities Network (MnSCN) newsletter.
“Trees are the Earth’s endless effort to speak to the listening heaven,” wrote Rabindranath Tagore, winner of the 1913 Nobel Prize in literature. The National Arbor Day Foundation decided last year that the trees had spoken on global warming. They revised their map of which trees can survive in different areas of the U.S. You can view it at http://www.arborday.org/media/zones.cfm.
The new interactive map reflects that roughly half of Minnesota, and the country, has average winter low temperatures that are higher than in 1990, when the last USDA hardiness zone map was published. Significant portions of many states have shifted warmer by at least one full 10 degree hardiness zone.
“A mixed blessing” is how Minneapolis Park and Recreation Board forestry director Ralph Sievert put it in the Minneapolis Tribune recently. While warmer winters now allow cities and citizens to plant more tree species, if global warming continues as expected in Minnesota, more tree-killing insects are expected to survive winters and to expand their ranges in the state.
Tree planting is among the positive actions organizations and citizens can take to combat global warming. See the web site above for an animation of the zone shifts, for hardiness zones by zip code, for the multiple benefits of trees, and for which trees are best for planting throughout the country.