What Will Climate Change Bring To
Bark Beetles in the Western and
Southwestern US?
Barbara J. Bentz
Rocky Mountain Research Station
USDA Forest Service
Photo Wally Macfarlane
Forest and Woodland
Ecosystem Research
12
Million Acres
10
8
Alaska
6
4
2
0
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Year
Native bark beetles have affected
> 56 million acres in the western
US over the past 10 years (USDA
Forest Health Protection).
Colorado
High elevation ecosystems
Southwestern US
Native Western US Bark Beetle Species That Can Cause
Landscape-Wide Tree Mortality
Mountain pine beetle
Dendroctonus ponderosae
Douglas fir beetle
D. pseudotsugae
Spruce beetle
D. rufipennis
Arizona fivespined ips
Ips lecontei
Roundheaded pine beetle
D. adjunctus
Jeffrey pine beetle
D. jeffreyi
Pinyon ips
Ips confusus
Western pine beetle
D. brevicomis
Southern pine beetle
D. frontalis
Pine engraver
Ips pini
Western balsam bark beetle
Droycoetes confusus
Ips calligraphus, Ips latidens and Ips knausi – complex in the SW
Precipitation
Atmospheric Gases
Temperature
Natural Enemies
Beetle development
& survival
Associated fungi
& bacteria
Pheromone production
& release
Host tree defenses
(inducible & constituitive),
Tree growth,
Distribution
Precipitation
Atmospheric Gases
Temperature
Natural Enemies
Beetle development
& survival
Associated fungi
& bacteria
Pheromone production
& release
Host tree defenses
(inducible & constituitive),
Tree growth,
Distribution
Temperature has a direct relationship to
bark beetle development rate & survival
Powerful pheromone communication system
• Temperature-dependent
‘adaptive developmental
timing’
• Evolved strategies to
reduce temperature
induced mortality
For the majority of bark beetle species in the western US,
very little is known about temperature-dependent
physiological response. Lifecycle information is limited to
observations on flight timing:
Ips confusus – 2 or more generations per year
Ips leconti – 3 generations per year
Ips pini – 2 or 3 generations per year
Ips calligraphus, Ips latidens and Ips knausi - ?
Western pine beetle – 2 to 4 generations per year
Fir engraver, western balsam bark beetle – 1 generation per year
Douglas fir beetle – 1 generation per year
Southern pine beetle – 3 to 6? generations per year
Roundheaded pine beetle - 1 generation per year
Mechanistic response to temperature - bark beetle
development rate & survival
50
140
Egg
Instar III
120
40
100
30
60
20
40
10
20
0
0
Spruce beetle
0
5
10
15
20
25
30
120
0
5
10
15
20
25
30
300
Instar IV
Instar I
100
Time (days)
Mountain pine
beetle
80
250
80
200
60
150
40
100
20
50
0
Prepupal diapause
0
0
5
10
15
20
25
30
0
5
10
15
20
25
30
100
70
Instar II
60
Pupae
80
50
60
40
30
40
20
20
10
0
0
0
5
10
15
20
Spruce Beetle
Mountain Pine Beetle
25
30
0
5
Temperature
10
15
20
25
30
Mountain pine beetle development rate curves
Bentz, Powell, Regniere unpublished data
Mountain pine beetle Cold Tolerance
Lifestage-specific direct effects of cold temperature on mortality
‘Supercooling point’ is the temperature at
which tissues freeze and death occurs, and
can be used as the lethal temperature.
30
20
10
Max
Microhabitat temperature varies
within and among years and
geographic locations.
Min
0
-10
-20
SCP, Max and Min Phloem Temperatures ( oC)
-30
Upper SCP
Mean SCP
Lower SCP
---
---
---
-40
---
---
---
South Utah
Larval supercooling point (SCP)
also varies.
30
20
10
0
-10
-20
---
-----
---
-30
---
---
-40
Cold tolerance is dynamically
dependent on temperature
regime experienced.
Central Idaho-1
30
20
10
0
-10
-20
-30
---
---
---
---
---
Simple low temperature threshold
can not explain the role of
temperature in mountain pine
beetle survival/mortality.
---
-40
Central Idaho-2
Aug 12 Oct 1 Nov 20 Jan 9 Feb 28 April 19 June 8
Date
From Bentz and Mullins (1999)
Field and lab data describing bark beetle response to
temperature
2
∂u
∂u ∆t 2
2 ∂ u
,
σE +σG
+ r [T (t ); ρ ] =
2
∂t
∂a 2
∂a
(
)
λ (t ' ) = f ( An (t ' )) = bn max( An (t ' ) − an , 0 )
30
20
10
Xi =
Max T.
0
SCP, Max and Min Phloem Temperatures ( oC)
-30
−(T −α i ) / βi
βi 1 + e −(T −α ) / β 
i
Min T.
-10
-20
e
Upper SCP
Mean SCP
Lower SCP
---
---
---
---
---
-40
2
i
---
South Utah
30
20
10
0
-10
---
---
-20
-----
---
-30
---
-40
Central Idaho-1
30
S= R ρS
G (t ,τ ) =
− ( τ−TS ) / σ S
e
σ S (1 + e − ( τ−TS ) / σS ) 2
20
10
0
-10
-20
---
---
---
-30
---
---
Central Idaho-2
224
274
324
9
59
Julian Date
4πν ( t −τ ) 3
e − ( τ−TL ) / σL
L= R ρ L
σ L (1 + e − ( τ−TL ) / σL ) 2
t
---
-40
1
  1− ∫t r (T ( s )) ds 
τ
exp −  4ν ( t −τ ) 


109
159
pout (t ) = ∫ G (t ,τ ) pin (τ )dτ .
0
dC / dt =−
(1 C ) S − C L
2




Jesse Logan
Jacques Régnière
Jim Powell
Temperature-driven process models –
Provide a filter between temperature
and beetle population success
Models Describing Beetle Response to Temperature
Mountain pine beetle
Lifestage specific development = f (temperature)
Logan & Amman 1986
Bentz, Logan & Amman 1991
Logan & Bentz 1999
Powell, Jenkins, Logan, & Bentz 2000
Logan & Powell 2001
Jenkins, Powell, Logan, & Bentz 2001
Gilbert, Powell, Logan & Bentz 2004
Powell & Bentz 2009
Probability of cold temperature survival = f (temperature)
Bentz & Mullins 1999
Régnière & Bentz 2007
Spruce beetle
Probability of univoltine lifecycle = f (temperature)
Hansen et al. 2001
Hansen & Bentz 2003
From Mike Dettinger & Dan Cayan:
http://geochange.er.usgs.gov/program/workshop/Dettinger.ppt
How will the trend in warming temperature
influence trends in mountain pine beetle
population success?
Landscape projections of Cold
Tolerance and developmental
timing across 12 contiguous
western US states.
Régnière & St-Amant. 2007
•
•
•
•
Generate 10,000 random points from a DEM of the western US.
Climate normals were used to run the simulations:
-actual monthly climate normals for the period 1961-1990
-climate-changed normals for the periods 2001-2030, 2041-2070,
2071-2100 (based on CRCM, v. 4.2.0, runs ADJ and ADL, a
moderate scenario).
The model is replicated 30 times at each point using a stochastically
determined normals temperature file.
Average output for each point is spatially interpolated (krigged)
back across the DEMs.
Probability of Survival
Mountain pine
Beetle
Cold Tolerance
1961-1990
Probability of Survival
Mountain pine
Beetle
Cold Tolerance
2001-2030
Probability of Survival
Mountain pine
Beetle
Cold Tolerance
2071-2100
Relate mountain pine beetle development
time to fitness (adaptive seasonality):
• Timing: Adult emergence
occurs at appropriate time of
year
• Synchrony: Peak adult
emergence occurs during a
relatively short period of
time to facilitate mass attack
Beetle wins
• Univoltine: 1 year lifecycle
Beetle loses
Mountain pine
Beetle
‘Adaptive
Seasonality’
1961-1990
2001-2030
2071-2100
1.0
22.5˚C
0.9
Cumulative Emergence
Mountain pine beetle
development parameters
Common Garden Rearing Experiments
0.8
0.7
0.6
0.5
0.4
0.3
ID
MT
UT
0.2
0.1
0.0
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
Emergence Date
1.0
0.8
CA3
ID
UT2
Cumulative Emergence
MT
OR
22 C
SD
0.6
ID
0.4
OR
CA3
UT
0.2
CA
CA1
AZ
0.0
0
25
50
CA
AZ
125
150
175
200
225
250
0.8
Cumulative Emergence
CA1
100
Days from Infestation
1.0
UT1
75
0.6
0.4
ID
CA1
CA2
SD
0.2
0.0
40
60
80
100
120
140
160
180
200
220
Emergence time
From: Bentz, Logan and Vandygriff 2001; Bracewell et al. 2009; Bentz et al. unpublished data.
MT
CA3
ID
UT2
UT1
CA1
CA
AZ
SD
22 C
0.8
Cumulative Emergence
OR
1.0
0.6
ID
0.4
OR
CA3
UT
0.2
CA
CA1
AZ
0.0
0
25
50
75
100
125
150
175
200
225
250
Days from Infestation
• Strong local selection for development time among
geographically separated D. ponderosae populations, and the
response varies with temperature.
• Slower total development at more southern latitudes (warmer
environments) and faster development at more northern
latitudes (colder environments) potentially facilitate the same
strategy, univoltinism.
From: Bentz, Logan and Vandygriff 2001; Bracewell et al. 2009; Bentz et al. unpublished data.
What lifestage(s) are responsible for the significant
phenotypic differences in total development time
among populations?
ID
AZ
Lifestage-specific development
time using “phloem
sandwiches”. Measure number
of days required to complete
each lifestage at several
constant temperatures from
4.0 to 27.5˚C.
Median development time (days)
ID (blue) & AZ (red) populations
Median Development Time
80
60
40
20
Threshold temperature and rate for pupation:
0
80
Median Development Time
Instar 2
Instar 1
Egg
ID
AZ
Instar 4
35%
64%
52%
81%
100% 100%
Instar 3
15.0˚C
17.5˚C
20.0˚C
60
40
Pupae
20
0
5
10
15
20
Temperature C
25
30
5
10
15
20
Temperature C
25
30
5
10
15
20
25
30
Temperature C
From: Bentz et al. 1991 & Bentz unpublished data
Cumulative Emergence
Teneral Adult Development
300
15C
AZ
ID
250
200
150
AZ: 64% pupation
ID: 35% pupation
100
50
Cumulative Emergence
0
300
250
17.5C
AZ: 81% pupation
ID: 52% pupation
200
150
100
50
Cumulative Emergence
0
300
20C
AZ & ID: 100% pupation
250
200
150
100
50
0
120
140
160
180
Time
200
220
240
2500
Cumulative Hours > 12C
2000
1500
1000
Lassen - Sugar pine
Tahoe - Western White & Lodgepole pine
Tahoe - Whitebark pine
San Bernardino - Pinyon pine
500
0
June 21 July 12
Aug 2
Aug 23 Sept 12
Oct 3
Oct 24
Nov 14
Date
San Bernardino NF - Pinyon pine - 2079 m
80
80
60
60
40
40
20
Attacks
20
0
June 29 July 19
Aug 8
Aug 28
Sept 17
Date (2009)
Oct 7
Oct 27
0
Nov 16
Number MPB Attacks
Emergence
Tree 2
MPB Emergence
Mountain pine beetle in CA
WC-EM-09-02
Summary
• Mountain pine beetle is adapted to local environments. This
knowledge informs tools for predicting population trends.
What about other species with large geographic ranges?
• A mechanistic understanding of bark beetle response to
temperature is needed for development of adaptive forest
management tools. We are working on a variant of our
phenology model for mountain pine beetle in southern
latitudes. Data is needed for other species.
• Can bark beetle species adapt to rapidly changing
environmental conditions?
• Potential local expansions or extinctions?
Potential for Mountain Pine Beetle Range Expansion North
and East
Jack pine
Western pines
Eastern pines
Potential for Mountain Pine Beetle Range Expansion North and
East
Cold tolerance
1961-1990
2001-2030
2071-2100
Development timing
Summary cont.
• Tree species will also adapt or migrate.
Current
Chihuahua Pine
Projected Distribution
2030
How will bark beetles adapted to
this and other tree species in
Mexico respond to climate
change?
2090
From: http://forest.moscowfsl.wsu.edu/climate/
Acknowledgements
Matt Hansen, Jim Vandygriff, Kim
Huntzinger, Jim Powell, Ryan
Bracewell, Ann Lynch
USDA Forest Service, Forest Health
Protection, Forest Health Monitoring
Photo: Deems Burton