effects of climate change on pacific northwest ecosystems dave peterson
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Effects of Climate Change on Pacific Northwest
Ecosystems
Dave Peterson
Climatic Variability and Change – A Brief Introduction
Radiative Forcing Components of Global Warming
1.6 Watts
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Source: IPCC
Average global temperature has increased 0.8°C since 1906.
IPCC (2007)
Average global temperature has increased 0.8°C since 1906.
IPCC (2007)
Warmest 12 years 1998,2005,2003,2002,2004,2006, 2001,1997,1995,1999,1990,2000
Data source: IPCC 2001
IPCC “best estimate” range of global-scale warming by the 2090s:
1.8 - 4.0°C
Warming expected through 21st century even if CO2 emissions end today due to persistence of greenhouse gases
Projected 21Projected 21stst Century Global Warming Century Global Warming
Projected Temperature in Northwest
Changes relative to 1970-1999
7.2°F
3.6°F
0°F
10.8°F
14.4°F
+1.2ºC
+1.9ºC (
+3.3ºC (
°C
Rate of change per decade expected to be 3 times greater through mid-21st century
Rate of change per decade expected to be 3 times greater through mid-21st century
Choice of emissions scenario matter more
after 2050s
Winter windsand pressure over the North Pacific
Summer windsand pressure over the North Pacific
Aleutian Low Subtropical High
HH
LL
El Niño Southern Oscillation
For the Pacific Northwest:Positive (El Niño) = Warm, dry winterNegative (La Niña) = Cool, wet winter
Southern Oscillation IndexSouthern Oscillation Index
Pacific Decadal Oscillation
• An El Niño-like pattern of climate variability
• 20 - 30 year periods of persistence in North American and Pacific Basin climate
Warm, dryWarm, dry
Cool, wetCool, wet
Droughts were more common prior to 1950
Gedalof et al. (2004)
Streamflow for the Columbia River, reconstructed from tree-ring data
Why extremes matter
Standard deviation
1 in 40 yr high range
The distribution of weather events around the climatic average often follows a ‘bell-shaped’ curve.
Climate change can involve change in the average, or the spread around the average (standard deviation), or both.
A shift in the distribution
of temperatures has a much larger relative effect at the extremes than near the mean.
A shift of 1 standard deviation makes a 1 in 40 yr event into a 1 in 6 yr event
3.6°F
2.7°F
1.8°F
0.9°F
cooler warmer
Temperature trends (°F per century) since 1920
Nearly every glacier in Nearly every glacier in the Cascades and the Cascades and
Olympics has retreated Olympics has retreated during the past 50-150 during the past 50-150
yearsyears
Photos courtesy of Dr. Ed Josberger, USGS Glacier Group, Tacoma, WA
South Cascade South Cascade Glacier, 1928 (top) Glacier, 1928 (top)
and 2007 (right)and 2007 (right)
Snow Water Equivalent Trends
• Most PNW stations show a decline in snow water equivalent
• Numerous sites in the Cascades with 30% to 60% declines
Decrease Increase
Altered Streamflow• More winter rain, less snow → higher winter
streamflows• Warmer temperatures → earlier snowmelt and shift in
timing of peak runoff
+3.6 to +5.4°F(+2 to +3°C)
Projected streamflow changes, 2050s
Forest vegetation varies over time
The Disease Spiral
From Manion (1991)
A pathological model is applicable to forest ecosystems
Warmer climate
Soil moisture stress (+)
Growth and vigor (-)
Growth and vigor are affected by human-related factors
Exotic plants, pathogens, insects
Forest harvest practices
Air pollution
Fire exclusion
Critical Threshold
Time
Temperature Increase
Climatic VariabilityCli
mat
eThresholds are important
Pinyon pine - juniper Jemez Mountains, NM
October 2002
Pinyon pine dead Jemez Mountains, NM
May 2004
Climate change and tree growth
Subalpine forests
Westside forests
Low elevation forests
Mid elevation forests
Eastside forests
Subalpine forests: Less snowpack; longer, warmer growing seasons = Growth increase
Mid elevation forests: Warmer summers, less snow pack = Depends on precipitation
Low elevation forests: Warmer summers, less snow pack = Large growth decrease
Species responsesAnnuals & weedy species ↑Deciduous and sprouting species ↑Fire-sensitive species ↓Specialists with restricted ranges ↓
Climate changeWarmer temperatureMore severe droughts
Fire resets succession, alters temporal scale of fire rotation.
Mature trees buffer effects of warmer climate without disturbance.
Habitat changesLandscape homogeneity ↑Fire-adapted species ↑Forest cover ↓Species refugia ↓
New fire regimesFire frequency ↑Extreme events ↑Area burned ↑
Disturbance drives ecosystem change
The disturbance pathway is faster
How will climate change affect wildfire?
Area burned – Western U.S., 1916 - 2007
Area burned – Western U.S., 1916 - 2007
Fire suppression Fire exclusion Fuel accumulation
Cool PDOWarm PDO Warm PDO
Area burned – Western U.S., 1916 - 2007
Fire suppression Fire exclusion Fuel accumulation
Cool PDOWarm PDO Warm PDO
Area burned – Western U.S., 1916 - 2007
Fire suppression Fire exclusion Fuel accumulation
Lots of fire Much less fire Lots of fire
Years with fire area > 80,000 hectares
National Forest data, 1916-2007
Warm-phase PDO Cool-phase PDO
Idaho 15 7
Oregon 14 5
Washington 11 2
TOTAL 40 (74%) 14 (26%)
Future wildfire?
McKenzie et al. (2004), Conservation Biology 18:890-902
Analysis of wildfire data since 1916 for the 11 contiguous Western states shows that for a 2.0oC increase that annual area burned will be 2-3 times higher.
Fire – a component of stress complexes
Lodgepole pine forest
McKenzie et al. (2009)
Effects of temperature increase on mountain pine beetle
• Population synchronized by temperature (onset of spring)
• Rate of generation turnover increases with temperature increase
Tree Mortality
Mountain Pine Beetle
Shaded areas show locations where trees were killed. Intensity of damage is variable and not all trees in shaded areas are dead. www.fs.fed.us/r6/nr/fid/data.shtml
1980 - 2004
Mountain Pine Beetle outbreaks British Columbia
Courtesy of Mike Bradley, Canfor Corporation
Forest carbon budgetsStorage (quantity) vs. uptake (rate)
Young forest Storage Uptake Mg/ha Mg/ha/yr
50-100 5-10
Old forest 400-1000 + 1.0
Options for planners and resource managers???