AMPHIBIANS
AND
CLIMATE CHANGE
Stephen Corn
USGS Northern Rocky Mountain Science Center
Aldo Leopold Wilderness Research Institute
Missoula, Montana
Global Amphibian Declines
•
•
•
•
Queensland
Central America
Western US
Global Amphibian Assessment
(Stuart et al. 2004)
– 32% of all species Threatened
(compared to 12% for birds)
– 7.6% classified as rapidly
declining
A Deteriorating Situation in the West
• Federal Threatened & Endangered
Species (western US)
– 5 species listed since 1990
– 2 more species proposed for listing
– 3 candidate species
• Montane species in “protected” areas
– Boreal toads in the Rockies
– Yosemite toads and mountain yellowlegged frogs in Sierras
Bufo boreas, Flathead Co, MT
Causes of Amphibian Declines
• Habitat alteration/destruction
• Disease
• ??? (about half of rapidly declining
species in the GAA have “enigmatic”
causes)
• What is the role of climate change?
Climate Change
• Extreme weather & local extinctions
– Freeze in Brazil (Heyer et al. 1988); drought in
Colorado (Corn and Fogleman 1984).
• Central & South American montane frogs
– Costa Rican (Monteverde) frogs, lizards, and birds declines coincident with ENSO events (Pounds et al.
1999).
• Drying and warming, less dry-season mist.
– Many species of Harlequin Frogs (Atelopus) last seen
following warm years (Pounds et al. 2005).
• Warming night-time temperatures (more clouds); more
favorable environment for Chytrid fungus?
Climate Change
• Interactions between El Niño, UV,
& disease in Oregon (Kiesecker et
al. 2001).
– Low snow in El Niño years causes
Boreal Toad eggs to be laid at
shallower temperatures, resulting in
increased UV-B radiation and
increased mortality from water mold.
However
• Amphibians breed earlier
in low snow years, resulting
in lower UV (Corn and
Muths 2002)
• Egg mortality has low
elasticity – less effect on
population persistence
(Biek et al. 2002)
• Declines of Boreal Toads in
the Cascades not shown
(Olson 2001)?
90
70
98
89
60
86
97
00
92
99
88
91
01
50
87
40
30
10 May
30 May
19 June
Day of maximum breeding activity
Corn and Muths 2002
Climate Change
• Thomas et al. (2004) predicted extinctions
based on shifts in climate envelope
– 13-68% of Queensland frogs
– However, low % extinctions in boreal & cool
coniferous forests.
• How might climate change affect a species’
distribution?
– Effects on breeding phenology has been the
most studied feature.
Effects of Variable Phenology
• Breeding earlier can be beneficial,
– More time for growth, earlier maturity
• Or not…
– Increased risk of exposure to extreme
temperatures
• Breeding later is often not good
– Increased risk of pond drying/freezing
– Less time for growth
Breeding Phenology
• Breeding in snow-dominated landscapes
is determined by snowmelt
Days since Vernal Equinox
90
80
Lily Pond, 1986 to 2003
P < 0.001
70
60
15
20
25
30
35
40
Maximum Snow Water Equivalent (in)
Breeding activity
of Boreal chorus
frogs (Pseudacris
maculata) in
northern Colorado
has been
monitored
annually since
1986
Long-term Data
(8 populations)
Rana luteiventris
Corn & Blake Hossack (MT)
Deb Patla (WY)
David Pilliod (ID)
Bufo boreas
Corn & Erin Muths (CO)
Dede Olson & Andrew Blaustein (OR)
Pseudacris
maculata
Corn & Erin Muths
Relationship Between Breeding
and SWE is Consistent
Days since Vernal Equinox
150
Site*SWE: P = 0.80
Mean Slope = 1.0
100
Species
50
0
0 10 20 30 40 50 60 70 80 90
Maximum Snow Water Equivalent (in)
BUBO, Colorado
PSMA, Colorado
RALU, Wyoming
RALU, Montana
BUBO, Oregon
BUBO, Oregon
BUBO, Oregon
RALU, Idaho
BUBO = Bufo boreas; PSMA = Pseudacris maculata; RALU = Rana luteiventris
• Used all Snow Course stations with at least
a record from 1950*-1999 (N = 557)
• Calculated the slope of Maximum Snow
Water Equivalent (SWE) vs Year
*37 stations began 1951-1953
Maxim um Snow Water Equivalent (in)
The station with the largest slope?
1 50
Mt Hood
1 00
50
0
1 940 1 950 1 960 1 970 1 980 1 990 2000
Northern Rockies
Northwest
Predicted change in breeding,
1950 to 1999
Days =
50 yr * slope (inches SWE/yr)
* 1.00 (days/in)
N Gr Basin
Sierra
Nevada
S Gr Basin
Central Rockies
Southern Rockies
Mogollon
Predicted Change in Breeding
1950-1999
Region
N
Days Earliest
Latest
Northwest
93
-7.7
-24.9
8.7
N Rockies
79
-5.3
-16.2
1.0
N Gr Basin
62
-4.1
-16.4
8.0
C Rockies
78
-2.1
-13.3
9.2
Sierras
32
-1.0
-13.3
7.7
S Rockies
146
-0.5
-10.1
6.9
S Gr Basin
51
0.2
-11.3
13.2
Mogollon
16
1.0
-1.9
2.5
Complexity
• Effects vary with
elevation
10
Change in breeding 1950-1999
– Greater changes at
lower elevations
– Less chance for
shift to higher
elevations?
Northwest: P = 0.047
0
-10
-20
-30
2000
4000
6000
Elevation (ft)
8000
Does Temperature Limit Range Shifts
to Higher Elevations?
• Permanent
snowfield
disappeared in
1920s
• Amphibians have
not colonized yet
Boulder Pass, Glacier NP
Temperature Effects on Life History
1920 m
Glacier National Park
1326 m
Fewer Freezing Nights
Mean May-Sept Temperature
May-Sept Days with Tmin < 0
60
50
40
30
20
10
25
20
Tmax
15
10
5
0
1990
1995
2000
2005
Tmin
1990
1995
2000
2005
Flattop Mountain
Emery Creek
• A large increase in
degree•days would
likely alter vital rates
– Largely beneficial?
• Effect of temperature
change so far?
– Less stress?
– Warmer nights
promote chytrid
fungus?
Mean Developmental Degree•Days
Relatively Little Change in Available Heat
10
8
6
4
2
0
1990
1995
2000
2005
Flattop Mountain
Emery Creek
What About Hydrology?
• Low snow years = reduced
breeding habitat
• Earlier runoff = earlier
drying of seasonal
wetlands?
• Most important
consequence of climate
change for mountain
amphibians?
Drying Columbia Spotted Frog eggs, Ravalli Co, MT, April
2001. BR Hossack, photo.
Other Landscape Effects
Pond Occupancy Before and After the
2001 Moose Fire, Glacier NP
Occupancy (Mean ± 2SE)
1.0
Long-toed Salamander
0.6
Columbia Spotted Frog
0.5
0.9
0.4
0.8
0.3
0.7
Prior After
Unburned
Prior After
Burned
0.2
Prior After
Unburned
Prior After
Burned
Hossack and Corn, in review, Ecol Appl.
Pond Occupancy Before and After the
2001 Moose Fire, Glacier NP
Boreal Toad
10
0.15
8
Occupied Ponds
Occupancy (Mean ± 2SE)
0.20
0.10
0.05
burned
unburned
6
4
Moose
Fire
2
0
0.00
Prior After
Unburned
Prior After
Burned
1999 2000
2001
2002
2003
2004
Hossack and Corn, in review, Ecol Appl.
Conclusions
• Little evidence for current effects on populations
• Mountain amphibians have a predictable relationship
between breeding and snow and in some areas are
likely breeding earlier now than in 1950
• Effects of warming temperatures are difficult to
detect
• Change can both benefit and harm populations, but
overall effects are difficult to predict
• Changing hydrology probably has the greatest
potential for harm
References
Biek R, Funk WC, Maxell BA, Mills LS. 2002. What is missing in amphibian decline research: insights from
ecological sensitivity analysis. Conservation Biology 16:728–734.
Corn PS, Fogleman JC. 1984. Extinction of montane populations of the northern leopard frog (Rana pipiens)
in Colorado. Journal of Herpetology 18: 147–152.
Corn PS, Muths E. 2002. Variable breeding phenology affects the exposure of amphibian embryos to
ultraviolet radiation. Ecology 83:2958–2963.
Heyer WR, Rand AS, da Cruz CAG, Peixoto OL. 1988. Decimations, extinctions, and colonizations of frog
populations in southeast Brazil and their evolutionary implications. Biotropica 20:230–235.
Kiesecker JM, Blaustein AR, Belden LK. 2001. Complex causes of amphibian population declines. Nature
410:681–684.
Olson DH. 2001. Ecology and management of montane amphibians of the U. S. Pacific Northwest. Biota
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