The Evergreen State without the Evergreens?

Long, dry summers can kill evergreen trees, and dead trees increase the risk of forest fires.  

Most climate models predict there will be a shift to hotter, drier and longer summers in Thurston County and all of western Washington. We’ve been seeing it play out in the summer months for the last several years, 2016 being the exception.

If June and September become hotter and drier than they currently are we would begin to see a dramatic shift in vegetation begin to occur quite quickly.  Within a decade there could be substantial changes to our forests. A shocking thought considering we are one of the rainiest parts of the United States.

The Remarkable Reversal

It’s a fact. The Pacific Northwest goes from the wettest part of the United States from November through March, to the driest part of the Country July through September.

There are other parts of the U.S. that get about the same overall amount of rain as we do here (about 52 inches per year) but it is distributed during the spring and summer months, for most other parts of the nation.  It comes mostly in the form of monsoon rains, tropical storms or thunderstorms almost everywhere else in the country.

As we know too well, the rain comes for us between October and May in variable doses every month. October through April is when we get 90 to 95 percent of our average 52 inches of annual precipitation in Olympia.  In the summers we go dry. As dry as any desert.

The effects of drought on forests in Northern California


Thurston County: Fifty + Days Without Rain and as Dry as a Desert

If measured on a monthly amount.  July is typically the driest and has been getting drier, followed by August and September.  In 2014, 2015 and 2017 July yielded an average on one hundredth of an inch of rain.  That is comparable to ten minutes of light rain the entire month. August is also arid and close behind July with an average of less than a quarter inch of rain.  That is about 45 minutes of light rain the whole month.  In 2014, 2015 August scored almost no rain at all.

It is not uncommon for Thurston County and all of Western Washington to be entirely without rain for fifty days or more.

If this trend of almost-no-rain, low humidity and high temperatures lasted for more than a couple of months, the western side of the state would look dramatically different than it does now in a very short amount of time.

Forest Fires More Likely in a Hotter and Drier Pacific Northwest Summer 

If June and September do get drier and hotter as predicted by the climate models there could be a full scale retreat of the Douglas fir forests around the whole Northwest and Alaska. Dead and weekend trees become a substantial fire hazard and an insect infestation bonanza.  The fir forests are critical habitat for all of our native birds and animals.  The sudden loss of the fir forests would result in the loss of many species of animals that inhabit the forests.

Dry weather contributes to fire on Rock Candy Mountain in the Capitol Forest in Olympia, Washington. Photo courtesy: The Olympian.

Rapid Loss of Forests and Animals

This change does not take decades but can begin in one season of prolonged drought or extraordinary heat and low humidity. We saw a glimpse of this in 2014 and especially the drought of 2015. Thousands of Douglas fir trees died in the forests around western Washington during those hot and dry summers.  If these events begin to occur more frequently and if the climate predictions are accurate, then the loss of these great forest giants becomes a real possibility of a hotter drier Pacific Northwest climate.

The loss of the Douglas fir forests in the Pacific Northwest would be an immediate and devastating loss of critically important resource and icon of our region.  Everything from our economy to agriculture and wildlife depend on the products and the habitat provided by our evergreen forests.

So keep in mind that the massive Douglas firs that fill in the spaces between our homes and cities and dominate our evergreen forests are at risk of sudden decline if we do warm up and dry off any more than we are currently experiencing.

If the summers are one or two months longer or 3 or 4 degrees warmer or just a little bit drier for a little bit longer we could witness the beginning of the end of the great evergreen forests of the Evergreen State.  What comes next is a new type of climate and a new type of ecology with different species of plants and animals. Some plants and animals we may like but many we may very well wish they had never moved into our neighborhoods; in the places where our once majestic icons stood for thousands of years.

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