impacts of climate change on salmon, part ii nate mantua ingrid tohver, and alan hamlet jisao cses...
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Impacts of Climate Change on Salmon, part II
Nate MantuaIngrid Tohver, and Alan Hamlet
JISAO CSES Climate Impacts GroupUniversity of Washington
Harley Soltes/Seattle Times
What we did
• Hydrologic models were forced by downscaled precipitation and surface temperature data for “historic”, 2020s, 2040s, and 2080s (Elsner et al.)
– Using the “VIC model” at 1/16˚ resolution; with multimodel composite A1B and B1 scenarios, respectively
• We analyzed simulated streamflow records at 97 locations for monthly average patterns, daily peak flows, and 10 day average summer low flows (base flows)
Why we chose these factors
• Peak flows: large flood events reduce egg-to-fry and parr survival rates
• Summer low flows = rearing habitat for fish with stream type life histories
• Seasonal runoff patterns are closely related to life history types and the biodiversity of salmon
3 basic streamflow
patterns1. rain-dominated
2. “transient” basins with an early winter peak from rainfall, and a spring peak from snowmelt
3. snowmelt-dominated basins, where streamflow peaks in late spring and early summer
HistoricalHistorical2080s A1B2080s A1B
Dramatic changes in snowmelt Dramatic changes in snowmelt systemssystems
• Snowmelt rivers become transient basins• Transient basins become rainfall dominant
• Models project more winter floodingmore winter flooding in sensitive “transient runoff” river basins that are common in the Cascades– Likely reducing survival rates for
incubating eggs and rearing parr
• Summer base flows are projected to Summer base flows are projected to drop substantiallydrop substantially (5 to 50%) for most streams in western WA and the Cascades– The duration of the summer low flow season duration of the summer low flow season
is also projected to increase in snowmelt is also projected to increase in snowmelt and transient runoff riversand transient runoff rivers, and this reduces rearing habitat
Cool water, weak stratificationhigh nutrients, a productive “subarcticsubarctic” food-chain with abundant forage fish and few warm water predators
Warm stratified ocean, fewnutrients, low productivity “subtropicalsubtropical” food web, a
lack of forage fish and abundant predators
Recently, warm ocean years have generally been poor for NW chinook, coho and sockeye, but good for Puget Sound pink and chum salmon.
Upwelling food webs Upwelling food webs in our in our
coastal oceancoastal ocean
The future will not present itself in a The future will not present itself in a simple, predictable way, as natural simple, predictable way, as natural variations will still be important for variations will still be important for
climate change in any location climate change in any location
Overland and Wang Eos Transactions (2007)
Box1
oC
Deg
rees
C
• Reduced calcification rates for calcifying (hard-shelled) organisms and physiological stress
• Shifts in phytoplankton diversity and changes in food webs
• Reduced tolerance to other environmental fluctuations
• Potential for changes to fitness and survival, but this is poorly understood
What are the biological implications of What are the biological implications of ocean acidification?ocean acidification?
Barr
ie K
ovis
h
Pacific Salmon
Coccolithophores
Vic
ki F
ab
ry
Pteropods
Copepods
AR
CO
D@
ims.
uaf.
ed
u
(Slide provided by Dick Feely, NOAA)
Warmer lower
flows in summe
r
Floods
Acidification, warming,
winds?
Warm, lowstreamflow
Impacts summary for salmonImpacts summary for salmon
Impacts will vary depending on life history and watershed types
• Low flows+warmer water = increased pre-spawn mortality for summer run salmon and steelhead – Clear indications for increased stress on
Columbia Basin sockeye, summer steelhead, summer Chinook, also Lake Washington sockeye and Chinook
• Increased winter flooding in Puget Sound streams– an increased stressor on egg-to-fry
survival rates for fall spawners, and overwinter survival rates for yearling parr (steelhead, coho, and stream-type chinook)
Impacts of Climate Change on Salmon Recovery in the Snohomish River (Battin et al. 2007: PNAS)
Climate Change will make salmon restoration more difficult:
• Decreasing Summer/Fall Low Flows
• Increasing Winter Peak Flows
• Increasing water temperatures in critical periods
Decreasing Spawning Flows
Increasing Winter Flows
Mitigating projected impacts
• Reduce existing threats caused by land/water use that impair natural hydrologic processes
– Protect and restore instream flows in summer– Identify and protect thermal refugia– Reconnect, restore and protect off-channel habitat in floodplains
Glines Canyon Dam, Elwha River
Increased conflict over use of surface water in summer
• Human demands on surface water are projected to increase during times of high salmon vulnerability