By Gary Salmon
The mortality figures are astonishing among the three tree species nearly eliminated from our eastern and Midwestern landscape by either chestnut blight (Cryphonectria parasitica), Dutch elm disease (Ophiostoma novo-ulmi), and now emerald ash borer (Agrilus planipennis). Four billion chestnut trees killed since blight introduction in 1904 (most between 1930s and ’50s and continues today). Seventy-seven million American elms killed since the disease appeared in the 1920s and continues today. And the most recent, emerald ash borer, has killed millions of ash since its introduction in Michigan in 2002 and continues today. All three have killed their way through Vermont destroying trees in both the urban and forest landscape. It was the trees within our urban landscape that most raised tree loss awareness and resulted in the investment of money and science aimed at preventing spread, finding “cures” and/or minimizing possible tree extinction. And thanks to those efforts we now have been able to retain and/or restore in some measure all three to our streets.
The difficult part in restoration efforts as a species, however, is returning those species back to the forest environment from which they were eliminated. Over time two restoration efforts are making progress (elms and chestnuts). Both the Nature Conservancy (with U.S. Forest Service assistance) and the American Chestnut Foundation have programs evolving for restoring elms and chestnuts to the forested landscape. Elms were once part of an entire forest type (ash, elm, red maple) with elms often being the larger of the three species. The Nature Conservancy is using a three year effort to plant some 7,000 elms (with some immunity to DED) in floodplain forests within the Connecticut and Champlain River Valleys. Likewise chestnut, although at the northern end of its range in Vermont and thus not as common, was a thriving part of the eastern forest growing to huge sizes and numbers. The American Chestnut Foundation, using blight resistant and locally adapted chestnuts, has established chestnut breeding orchards whose progeny will be reintroduced into eastern forests. The VT/NH chapter of TACF along with Vermont State Parks created a breeding orchard in 2013 at Lake St. Catherine State Park in Poultney and it is thriving with several trees now exceeding 20 feet in height.
Since EAB is a work in progress forest recommendations will change as knowledge about the borer grows. For now don’t cut all ash within a forest but do reduce the ash component if it exceeds 20%. Leave scattered ash growing and retain good quality trees of a variety of species. Manage the forest if possible to encourage as much ash regeneration as possible. Time will tell (measured in decades) if any of these three forest species will ever return or stay in their rightful forest environment. But as the Lorax says, “unless someone like you cares a whole awful lot, nothing is going to get better. It’s not.”
