Different Climate – Fire Relationships
on Forested and Non-Forested
Landscapes in California
Jon E. Keeley
Alesandra Syphard
Photo: Chris Doolittle
U.S. Geological Survey
Western Ecological Research
& UCLA
Ecology & Evolutionary Biol
Conservation Biology Institute
USFS lands in California
Extent to which 20th & 21st century
fires have burned at frequencies similar
to pre-Euroamerican settlement
(Safford & van DeWater in review)
U.S. Forest Service Cal Fire 1919‐2010 USFS 1910‐2010
California
CalFire
280
210
2
(1000-ha / million ha)
120
Area burned
(1000-ha / million ha protected)
Area burned
350
r = 0.70
P = 0.005
140
70
USFS
90
60
r2 = 0.62
P = 0.021
30
1920 1940 1960 1980 2000
1920 1940 1960 1980 2000
Decade
Decade
(Keeley & Syphard in preparation)
CalFire
2000
1500
1000
500
1910 1930 1950 1970 1990 2010
YEAR
(# of fires / million ha)
750
Fire frequency
(# of fires / million ha)
Fire frequency
2500
USFS
600
450
300
150
1910 1930 1950 1970 1990 2010
YEAR
Fire ignitions do not track area burned and although fire ignitions were several times higher on lower
elevation CalFire lands, the historical patterns were remarkably similar on both USFS and CalFire lands,
showing peak in fire frequency in the later quarter of the 20th century.
U.S. Forest Service North Coast
North Interior
40
30
20
10
0
1920 1940 1960 1980 2000
40
30
20
10
1920 1940 1960 1980 2000
50
Central Coast
40
Sierra Nevada
40
30
20
10
0
1920 1940 1960 1980 2000
30
50
20
10
0
1920 1940 1960 1980 2000
Area burned
(1000-ha / million ha protected)
0
Area burned
(1000-ha / million ha protected)
50
Area burned
(1000-ha / million ha protected)
Area burned
(1000-ha / million ha protected)
50
Area burned
(1000-ha / million ha protected)
50
Southern California
40
30
20
10
0
1920 1940 1960 1980 2000
400
North Interior
North Coastal
300
300
200
r2 = 0.70
P = 0.005
200
r2 = 0.82
P < 0.001
100
100
0
0
1920
1940 1960 1980
1920
1940 1960 1980
2000
2000
400
Sierra Nevada
300
r2 = 0.56
P = 0.020
200
400
Area burned
(1000-ha / million ha protected)
Area burned
(1000-ha / million ha protected)
400
Central Coast
100
300
0
2
r = 0.60
P = 0.014
200
1920
1940 1960 1980
Decade
2000
400
Southern California
100
300
0
1920
1940 1960 1980
Decade
2000
200
100
0
1920
1940 1960 1980
Decade
2000
One approach to evaluating the role of global warming in driving future fire regimes is through the historical relationship between annual fire activity and climate 12
1
Ash Mountain
Winter
0
11
Lodgepole
Winter
-1
Average temperature (oC)
Over the last century
seasonal temperatures have
varied from year to year by
as much 4–5 oC
10
-2
9
-3
r2 = 0.03
P = 0.203
8
r2 = 0.11
P= 0.046
-4
7
-5
1945 1958 1971 1984 1997 20101965 1974 1983 1992 2001 2010
29
16
28
Ash Mountain
Summer
Lodgepole
Summer
15
27
14
26
25
r2 = 0.02
P = 0259
13
r2 = 0.08
P= 0.088
24
12
1945 1958 1971 1984 1997 20101965 1974 1983 1992 2001 2010
Year
Average winter and summer temperatures at a non‐forested foothill site (Ash Mt) and a forested montane site (Lodgepole) in the Sierra Nevada
Sierra Nevada region
5. Sierra Nevada El Dorado Amador San Joaquin Calaveras Stanislaus Tuolumne Mariposa Merced Madera Inyo‐Mono Fresno Kings Tulare Kern
5. Sierra Nevada )
El Dorado NF
Stanislaus NF
Inyo‐Mono NF
Sierra NF
Sequoia NF
Sierra Nevada region
A) USFS
Area burned (log ha / million ha)
5.0
5.0
Winter
4.2
4.2
3.4
3.4
2.6
2.6
1.8
r2 = 0.00 1.8
r2 = 0.15
P = 0.648
P < 0.001
1.0
1.0
3.0 4.5 6.0 7.5 9.0 10.5 7.5 9.0 10.5 12.0 13.5 15.0
5.0
5.0
Summer
Autumn
4.2
4.2
3.4
3.4
2.6
2.6
1.8
B) Cal Fire
Area burned (log ha / million ha)
5.0
5.0
Winter
4.2
4.2
3.4
3.4
2.6
2.6
1.8
1.0
3.0 4.5 6.0
5.0
Summer
r2 = 0.00 1.8
P = 0.814
1.0
7.5 9.0 10.5 7.5
5.0
4.2
4.2
3.4
3.4
2.6
2.6
1.8
1.0
21
22
23
r2 = 0.01 1.8
P = 0.367
1.0
24 25 26
14
1.0
21
Spring
Spring
22
23
r2 = 0.12 1.8
P < 0.001
1.0
24 25 26
14
r2 = 0.00
P = 0.687
15
16
17
Average temperature (oC)
r2 = 0.00
P = 0.938
9.0 10.5 12.0 13.5 15.0
Autumn
r2 = 0.00
P = 0.644
15
16
17
Average temperature (oC)
18
19
18
19
A) USFS
Sierra Nevada region
Area burned (log ha / million ha)
5.0
5.0
Winter
4.2
4.2
3.4
3.4
2.6
2.6
Spring
1.8
r2 = 0.04 1.8
r2 = 0.22
P = 0.062
P < 0.001
1.0
1.0
0 125 250 375 500 625
0 125 250 375 500 625
5.0
5.0
Summer
Autumn
4.2
4.2
3.4
3.4
2.6
2.6
1.8
1.0
0
r2 = 0.05 1.8
P = 0.021
1.0
125 250 375 500 625
0
r2 = 0.00
P = 0.555
125 250 375 500 625
Precipitation (mm)
B) Cal Fire
5.0
Winter
4.2
4.2
3.4
3.4
2.6
2.6
Spring
1.8
1.8
r2 = 0.00
r2 = 0.01
P = 0.921
P = 0.521
1.0
1.0
0
125 250 375 500 625
0
125 250 375 500 625
5.0
5.0
Summer
Autumn
4.2
4.2
3.4
3.4
2.6
2.6
1.8
2
r = 0.00
P = 0.956
1.0
0
1.8
1.0
125 250 375 500 625
0
2
r = 0.00
P = 0.665
Area burned (log ha / million ha)
Areaburned(logha/ millionha)
5.0
5.4
5.4
A) USFS
4.5
4.5
3.6
3.6
2.7
2.7
1.8
r2 = 0.14
P < 0.001
0.9
0
B) Cal Fire
1.8
0.9
600 1200 1800 2400 3000 0
r2 = 0.00
P = 0.999
600 1200 1800 2400 3000
Snow depth in April (mm)
125 250 375 500 625
Precipitation (mm)
Forested vs Non-Forested
(USFS)
(Cal Fire)
Differences:
1
2
3
4
5
Elevation
Vegetation
Area burned and fire frequency
Population density
Climate – fire relationship
Cal Fire – weak relationship
USFS multivariate r2 = 0.32
6 USFS vs Cal Fire Management
USFS
350
60
r2 = 0.62
P = 0.021
30
Area burned
90
(1000-ha / million ha protected)
Area burned
(1000-ha / million ha)
120
CalFire
280
210
r2 = 0.70
P = 0.005
140
70
1920 1940 1960 1980 2000
1920 1940 1960 1980 2000
Decade
Decade
The Poetry of D.H. Rumsfeld
—Feb. 12, 2002, Department of Defense news briefing
The Unknown
As we know,
There are known knowns.
There are things we know we know.
We also know
There are known unknowns.
That is to say
We know there are some things
We do not know.
But there are also unknown unknowns,
The ones we don't know
We don't know.