New publication: The extent of yellow-cedar decline along the US and Canadian Pacific coast

Photo credit: Lauren Oakes

Our research which compiled and compared mortality along the outer coast of both the US and Canada is now accepted, and will appear in the journal Global Change Biology.  The research, which was the first to unify both Canadian and US records of both yellow-cedar mortality and occurrence, is notable because it documents this widespread phenomena which is directly tied to climate warming.

Map of the range and decline of yellow-cedar along the outer coast.  Around 70% basal area is dead the few studies that have quantified mortality.

 

The range of the species had never been outlined at this fine of a scale, and we show the species occurring from Prince William Sound, in south central Alaska, to northern California and eastern Oregon - quite the range.  But the mortality has quite the range also, from northern southeast Alaska to southern BC (about 10 degrees latitude, adding up to about 8% of the total range). The mechanistic understanding of how this mortality occurs, developed from fine scale studies, appears to hold up - mortality is concentrated in areas of the range where winter temperatures are clustered around 0 degrees; places where a little warming causes massive changes in snowpack.  Areas of the range well below this threshold are healthy, as are the few areas well above (as there is no risk of winter freezing).

Distribution of dying and healthy stands of yellow-cedar as a function of latitude.  Width of the boxplot is relative to the proportion either alive or dead, but not for comparison between live and dead.

We also looked at protected areas, to see if areas "safe" in the future (i.e., cold enough) are protected.  It doesn't appear so; very little of the range is both protected and safe.  In fact most of the range will be above the winter freezing threshold in the future (about half is already and thus exposed to mortality, and about half will be in the next few decades).

The outer coast is a good test case for future warming elsewhere, as it is a long latitudinal band that is crossing the freezing threshold sooner than most places around the world.  But those places will likely cross that boundary too, so perhaps this is an early warning of other changes to come.

Current range and areas which are currently below freezing (precipitation as snow in winter) which are likely to shift to rain in the future.

Buma B, Hennon PE, Harrington CA, Popkin JR, Krapek J, Lamb M, Oakes LE, Saunders SC, Zeglen S.  Emerging broad-scale mortality driven by climate warming and loss of snowpack.  Global Change Biology.  In press.