Climate change and high elevation
aquatic species
Kathleen R. Matthews
US Forest Service Research
Sierra Nevada Research Center
What do we know about climate change impacts
on fish and amphibians?
•
•
•
•
•
No major assessment of predicted changes on aquatic organisms
in the California or Sierra Nevada
For aquatic systems, most work is directed towards describing
physical changes to snowpack, temperatures, flow, etc,
We need to begin understanding how these physical changes will
affect the biological species
Because there is considerable uncertainty, we need risk
assessments of how different predicted changes may affect native
and non-native species
Many of the predicted changes may favor invasive & non-native
species
Climate change: predicted impacts for aquatic
species at high elevation
• Decreased snowpack —may be more dramatic at lower
elevation (<9000 ft)
• Earlier snowmelt some year-round mountain streams
going dry by summer
• Less water availability
• Increased lake/pond drying —may be a problem for
species that have multiple year tadpoles, if lakes dry
tadpoles die
• Water temperature increases
• Winter and spring temperatures warmer
Important considerations
• Will need to assess interactions between climate
change and the ongoing disturbances—invasive
species, habitat modification, water diversions, etc
• Consider unique life histories of impacted species
• Many amphibians and fish species are already in
trouble so climate change impacts may exacerbate
• Resource managers need this information
Evidence for regional changes
that have already occurred:
Warming trends in climate
correlate with earlier flows
From Stewart, Cayan, Dettinger J.Climate 2004
Earlier run-off & decreased fraction
as snowmelt (more rain than snow)
Sierra Nevada High Mountain Lakes
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>10,000 lakes & ponds above 2500 m
•
Primarily found in federally protected Wilderness of
national parks and forests
•
Typically small (<10 ha), shallow (<10 m), and clear
•
Most (99%) historically fishless
•
Most lakes > 1 ha stocked with non-native trout
Stocking continues in Forest Service
Wilderness lakes;
¾ National Park Service ended stocking in 1970s
¾
What’s in the lakes and streams of the
High Sierra
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•
•
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Golden trout endemic to streams of the southern
Sierra meadows
Several amphibians endemic to water bodies that
were naturally fishless
Zooplankton and benthic invertebrates
Mountain garter snakes
Rana muscosa, mountain yellow-legged frog
• Endemic to Sierra Nevada, California
• Declined throughout most of its range
primarily due to exotic trout stocking
• High elevation species--Short active period
from snowmelt until lakes freeze
• Found warranted for ESA listing
Rana muscosa Life Cycle
Froglet/Tailed Frog
Subadult/
Recent
Metamorph
Adult
Legged Tadpoles
Tadpole phase
lasts 3-4 years
and requires
perennial water
Tadpoles
Eggs
Interaction of Climate Change and an
Introduced Predator in the recruitment
dynamics of Rana muscosa
Igor Lacan, Kathleen Matthews, Krishna
Feldman
Climate change: reduced snowpack in
Sierra Nevada?
From: Knowles, N., and D. R. Cayan, Potential effects of global warming on the Sacramento/San
watershed and the San Francisco estuary, Geophys. Res. Lett., 29(18), 1891, 2002.
Joaquin
Max Snow Water Content (cm)
Dusy Basin snowpack
120
100
80
60
40
20
0
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
MaxSWE (wet summer)
MaxSWE (dry summer)
Some lakes dry
All lakes wet
Avg. MaxSWE (1930-2006)
>>80% of egg masses
Maxmum number of metamorphs (MaxMets)
400
300
200
100
0
1
2
3
4
P e rm a n e n c e ra n k
(1 - p e rm a n e n t, 5 - d rie s e a c h ye a r)
5
Maximum number of metamorphs
400
300
200
100
0
1
2
3
4
Drying Code
(1 - wet last 2 yrs;
2 - wet last yr;
3 - wet 2 yrs ago;
4 - dry last 2 yrs)
Climate change + introduced predator = ?
Effects of Climate Change
•
Loss of high-snowpack yrs (highest egg
production)
•
Increased summer drying of breeding
lakes and all tadpoles lost
Æ Reduced breeding success
Effects of Fish predator
•
Breeding restricted to small, shallow
lakes
Æ Limited breeding sites
Exotic/Invasive Trout in Sierra Nevada Lakes
• Most lakes were naturally fishless
• As a result of stocking, >80% of lakes larger
than 1 hectare now have exotic trout
• Warmer winters could increase trout survival if
lakes don’t freeze
Hyla regilla, Pacific treefrog
• Tadpoles metamorphose in one summer
• Frogs leave water bodies and return only for
breeding
• May be less influenced by climate change
compared to Rana muscosa
• Important to look at different species
California Golden Trout
• California’s state fish; one of few native fish
>8000 ft
• Native to South Fork Kern River and Golden
Trout Creek; not native to any lakes
• Most of its native range now within Golden
Trout Wilderness
• Threatened by degraded habitat and introduced
brown and rainbow trout
• Petitioned for federal ESA listing
Golden Trout
Wilderness
encompasses
most of the
subalpine
meadows of
the Kern
Plateau
Overgrazed Stream
Habitat in the Golden
Trout Wilderness:
shallow, wide, and little
streamside vegetation
prone to high water
temperature
Overgrazed
Stream
Habitat in
the Golden
Trout
Wilderness
Cattle grazing in Golden Trout Wilderness
meadow streams results in:
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Reduced streamside vegetation
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Collapsed streambanks
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Shallower, wider stream sections—vulnerable to increased water temperature
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Increased sediment
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Reduced habitat for adult fish—overhanging banks, deep pools
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Increased spawning habitat and spawning success-population stunted
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Unless overgrazed areas are rested and restored, climate change could
exacerbate
California Golden Trout Conservation
& Assessment Strategy
• One task is to monitor stream temperatures
• Previous work in early 1990s found water temperatures in Mulkey
meadow often reached 24oC primarily in impacted stream areas with
little vegetation
• Temperatures above 24oC are considered stressful
• Analysis of current water temperature info is critical
• Some meadow streams currently rested from grazing—managers
need to carefully assess whether recovery is adequate to
accommodate warmer temperatures & other predicted climate change
factors
What now?
• A basic assessment of what’s known and predictions for
how climate change will impact Sierran aquatic species
• We need to begin understanding how these physical
changes will affect the biological species
• Risk assessments of how different predicted changes may
affect native and non-native species under a range of
predictions
Dusy Basin July 15, 1998