The human population of Minneapolis is on the rise again, but our city’s most deeply rooted inhabitants, American elms, dwindle every year. When the elms leaf out, I wonder how many of them will make it through another season. The dreaded orange rings recently showed up around a number of stately elms around the corner from my block (my street has the rather ungraceful, but also apparently unkillable ginkgos) so I decided to get an elm disease report from the city’s top tree guy, Ralph Sievert, forestry director for the Minneapolis Park and Recreation Board.
As of mid-July, the elm death toll this year reached 1,000 – evenly divided on public and private property. It turns out that as elm loss goes, 2012 is shaping up as a 2,000-tree-death year, no worse than recent years, Sievert said. Still, it’s more than shade and a carbon sink that are lost. The spreading limbs and immense crowns lend texture and depth to the streetscape that no other tree can really match. It’s hard to appreciate what an elm does for a place until it’s gone.
Sievert gave me more elm statistics. Back in 1963, Minneapolis was home to 212,300 elms. There are about 35,400 left. Dutch elm disease arrived with a vengeance in the 1970s, killing as many as 20,000 in a year. It slowed in the 1990s, but flared up anew in 2004, when 5,300 trees were affected.
Dutch elm disease is a fungus that’s spread by elm bark beetles. For years, the city’s policy has been to slow the spread of the disease by quickly identifying and chopping down infected trees. Inspectors go street to street, looking for brown leaves at the very top of the elm. They confirm it by peeling back a section of park – if there are brown streaks, instead of the usual creamy complexion, then the tree is infected.
I asked Sievert why they didn’t let the elms die at their own pace, given that we would eventually lose all of them anyway. He said the city’s policy actually prolonged the elm population by slowing the epidemic. “We’re kind of a success story when it comes to Dutch elm disease,” he said.
The park board plants 500 to 600 elms each year – three of them Asian strains, and one disease-resistant variety of the American elm called the “Princeton Elm.”
Here's the eight-year breakdown on trees lost planted in Minneapolis, courtesy of the park board.
|Trees lost to Dutch Elm Disease||-5324||-3065||-1821||-2877||-2013||-1732||-1253||-1224|
|Other Trees Lost||-1855||-2859||-2118||-2256||-2258||-2868||-2332||-3402|
|Ash trees removed||-1410||-818|
|Total Trees Lost||-7179||-5924||-3939||-5133||-4271||-4600||-4995||-5444|
|Total Trees Planted||4004||2665||3638||3546||3589||4206||5382||5589|
|Net Loss of Trees||-3175||-3259||-301||-1587||-682||-394||387||145|
Here' are more elms we’re losing this year.