The benefits of extreme cold in Minnesota

My dad used to say our cold Minnesota winters "keep out the riffraff."

That wouldn't win him any PC awards these days. But it's true in the bigger context I now understand to include critters like invasive insect species that can harm Minnesota's forests.

626 EmeraldAshBorer_lg
Emerald Ash Borer. Image: David Cappaert, Michigan State University

Minnesota's extreme cold has benefits. My conversations with renowned University of Minnesota Center for Forest Ecology director Lee Frelich have taught me that extreme cold in Minnesota is critical to forest health.

Lee says extreme cold is critical for achieving high insect mortality rates. The cold is good news for ash trees who are under attack from the emerald ash borer.

626 ash range

When temperatures hit minus 36 to minus 40 in Minnesota, up to 99 percent of ash borer larvae can die.

Table 1. Coldest temperatures recorded in largest and smallest diameter logs used in larval COLD HARDINESS OF EMERALD ASH BORER, AGRILUS PLANIPENNIS: A NEW PERSPECTIVE Robert C. Venette1 & Mark Abrahamson2 However

Extreme cold in Minnesota keeps away other invasive pests too. But climate change in Minnesota is making temperatures like minus 40 up north and minus 20 in the Twin Cities less frequent.

CC winter hardiness zones Twin Cities 2015
Image via Minnesota Rose Gardener.

So when you see extreme cold in the forecast, there are reasons for Minnesotans to celebrate.


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