Bark beetle outbreaks in North America
and climate change
These slides illustrate the extent, causes, and consequences of bark beetle-caused tree mortality in North America, with an emphasis on the role of climate change.
The focus is on my research. However, to make important points, I include reviews of others’ research and results of other studies. Of course, there are additional studies that make similar points, sometimes better.
The slides are divided into three parts: 1) extent of outbreaks; 2) causes of outbreaks, including climate change; and 3) consequences of outbreaks.
Notes below each slide provide additional information and references.
Please retain photo and figure credits.
Feel free to contact me with feedback or requests (jhicke@uidaho.edu).
1. Extent of outbreaks
The next slide shows “affected area”, which includes live trees and is what is commonly reported.
Hicke et al., Global Change Biology, 2012
Insect outbreaks are major forest disturbances in North America
affected area reported by aerial surveys, 1997-2010
The next (remaining) slides show “mortality area” as developed in my lab (credit to Arjan Meddens). Mortality area is the area occupied by killed trees only, and is a better representation of the impact than affected area.
Bark beetle outbreaks are widespread and extensive in western North America
Meddens et al., 2012; Hicke et al., 2016
Central Colorado, 2007
Bark beetles are significant forest disturbances
Meddens et al., Ecological Applications, 2012 (updated)
Cumulative mortality area, 1997-2010
Mortality area
Bark beetle outbreaks are significant forest disturbances in western North America
Hicke et al., Forest Science, 2016
Major bark beetle outbreaks, 1997-2010
Meddens et al., Ecological Applications, 2012
Mountain pine beetle from Landsat satellite imagery
Meddens et al., FEM, 2014
Mountain pine beetle outbreak
Central Colorado
August 2007
QuickBird satellite imagery
100 km/62 miles north-south
Mountain pine beetle outbreak
Central Colorado
August 2007
QuickBird satellite imagery
100 km/62 miles north-south
Breckenridge
I70
Keystone
Granby
Fraser Experimental Forest
Fraser
Winter Park
Rocky Mountain
National Park
Grand Lake
2. Causes of outbreaks
Although there are many causes of and factors influencing bark beetle outbreaks (see Raffa et al., Bioscience, 2008 for more information), two main ones exist for large outbreaks: stand structure and climate.
Factors related to beetles:
Factors related to trees:
Factors influencing mountain pine beetle epidemics
Photo courtesy USDA Forest Service, www.forestryimages.org
Safranyik et al. 1975; Shore and Safranyik 1992; Carroll et al. 2004; Logan and Powell 2001
stand structure
climate
Forest stand structure influences outbreaks
Hicke and Jenkins, Forest Ecology and Management, 2008
The next slide is for a talk that doesn’t want details, only an overview of the role of climate change and outbreaks.
Note that mountain pine beetle attacks a variety of pine species. Outbreaks in lodgepole pole have been attributed to climate change, though with less certainty given that extensive outbreaks were recorded early in the 1900s. Outbreaks in high-elevation whitebark pine seem to be a good signal of recent warming.
Photos by J. Hicke
Roles of climate in recent outbreaks of mountain pine beetle: warming, drought
The following slides illustrate several clear cases of the role of recent warming causing bark beetle outbreaks in North America:
Photo Jeff Hicke
red = mortality
Weed et al., Ecol. Monographs, 2013; Buotte et al., Ecol. Apps., 2016
Whitebark pine mortality from beetles 1997-2010: Winter warming, drought in early 2000s
Future projection of climate suitability for mountain pine beetle outbreaks in whitebark pine
Buotte et al., Ecol. Applications, 2016
Suitability of winters for beetles in Greater Yellowstone Ecosystem
J. Hicke
Weed et al., Ecol. Monographs, 2013
Weed et al., Ecological Monographs, 2013
Warm, dry summers promoted spruce beetle outbreaks in southern Alaska
Weed et al., Ecological Monographs, 2013
Warming winters facilitate range expansion of southern pine beetle into New Jersey
Hotter drought caused extensive tree mortality in Southwestern US
Meddens et al., New Phytologist, 2015
Bark beetles were present and amplified mortality, but exact role unknown
3. Consequences of outbreaks
Economic impacts of forest disturbances
Dale et al., BioScience, 2001
“Climate Change and Forest Disturbances”
www.realvail.com
trib.com
“Every day across the West, an estimated 100,000 lodgepole pines fall in the forest…” USFS
Trees killed by bark beetles:
impacts on infrastructure, recreation
J. Hicke
J. Hicke
Photo by Matt Stensland
www.steamboatpilot.com/news/2008/aug/17/dying_forests_increase_wildfire_danger_across_west
Do beetle-killed trees affect forest fires?
J. Hicke
Conceptual framework of effects of beetle outbreaks on subsequent wildfire
Hicke et al., Forest Ecology and Management, 2012
Fuel characteristics
Fire characteristics
Fuel characteristics
Fire characteristics
Effects of bark beetle-caused tree mortality on wildfire
1-4 yr: red phase
J. Hicke
Hicke et al., Forest Ecology and Management, 2012
Fuel characteristics
Fire characteristics
Effects of bark beetle-caused tree mortality on wildfire
5-10 yr: gray phase
J. Hicke
Hicke et al., Forest Ecology and Management, 2012
Fuel characteristics
Fire characteristics
Effects of bark beetle-caused tree mortality on wildfire
decades: old phase
J. Hicke
Hicke et al., Forest Ecology and Management, 2012
Consequences of tree mortality:
future climate change via carbon cycle feedbacks
J. Hicke
Forest carbon stocks affected by beetle outbreaks
1997-2010
bark beetles: 289 Tg C
wildfires: 197 Tg C
BB+fires ≈ harvest
Hicke et al., ERL, 2013
%C in trees killed by beetles (by ecoregion)