Tuesday, October 31, 2017

Die-off on Hornby Island's Helliwell Provincial Park

Catherine Alexander, the observant citizen scientist who first detected the Seward Park sword fern die-off four years ago, has just returned from Hornby Island - just east of Vancouver Island, 135 miles north of Victoria, between Nanaimo and Campbell River:


Catherine spent most of a day exploring Helliwell Provincial Park, and reports:


Much of the park is old forest, Doug Fir, western red cedar, madrona.  Similar to Seward, Sword fern makes up a good part of the understory. I noticed wilted ferns immediately as we started out, and continued seeing them as we explored. In some places it looked as if most of the ferns visible from the trail were affected. In other areas the ferns on one side of the trail looked healthy while the other side of the trail was affected.  Below are a couple of pictures of small groups of dying ferns, as well as a map of the park with our route through the forested areas marked in red. 

Catherine reports that the islanders became aware of the problem only this year, and considered it the result of an unusually hot and dry summer.   We cannot be sure that that is not so - absent a biological marker of the presumed pathogen - but to both Catherine and me this does not look like a drought affect.   Seattle had less that < 0.1 inch of rain this summer, and Seward's sword ferns weathered this without evident damage.   That is: the effects of the putative pathogen - the die-off - are apparently not difficult to distinguish from drought effects.




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