Download Slide 1 - MidCoast Watersheds Council

BEAVERS
and Watershed Restoration
on the Oregon Coast
Wayne Hoffman
MidCoast Watersheds Council
Acknowledgments
• Bio Surveys LLC of Alsea Oregon collected much
of the data presented here, and have provided
much insight into Beaver biology.
• OWEB funded Beaver Pond surveys through its
program of disaster aid to salmon trollers.
• Pacific States Marine Fisheries Commission is
providing financial support for this outreach
project.
Coastal Perspective
• Beaver Ponds Provide Multiple
Ecosystem Services:
– Habitat for salmon, trout, wildlife
– Primary, Secondary Productivity
– Nutrient cycling, Nutrient distribution
– Hydrology / Flow moderation
How Beaver are tightly linked to Coast Range Fish Abundance
Salmonid rearing habitat
• Coho and Cutthroat summer rearing in
Beaver Ponds vs stream pools:
↑ growth rate in Ponds = Bigger Smolts
↑ Carrying Capacity in Ponds = More Smolts
• Coho Winter Habitat Needs
– Cover
– Refuge from current
– Off-channel or ponded habitat
Recognition of Salmonid Habitat
Role
• Oregon Coastal Coho Recovery Plan
• Salmon Essential Habitat
• OC Coho Native Fish ConservationPlan
– Increasing the number of beaver dams in
areas where dams are limited…
Food Web productivity
• Beaver ponds have higher aquatic
primary productivity
– Both Algae and Vascular Plants
– More surface area
– More retained nutrients
– More sun
• Ponds support more invertebrate biomass
(secondary production)
Nutrient Retention / Cycling
• Detritus is primary organic nutrient source
for woodland streams:
– Fallen leaves
– Conifer needles
– Salmon carcasses
– Other organics
Nutrient Retention / Cycling
• Nutrient distribution in stream network
affects ecosystem health, function.
– Headwaters comparatively sterile
– Upper reaches nutrient poor (oligotrophic)
– Lower reaches nutrient rich (eutrophic)
• Beaver ponds can retain detritis, flatten
nutrient distribution.
Stream Hydrology
• Beaver Ponds slow, extend drainage of
ground water into streams.
– Increases summer flow rates.
• Ponds support water table.
– Benefits riparian vegetation.
• Hydraulic head from ponds may create
hyporrheic (underground) flow.
Can these Ecosystem Services
be Sustained?
• We have Documented a Decline in Beaver
Dams and Ponds.
• Major declines since 1990s
• Fewer Dams, Ponds
• Smaller Dams, Ponds
• Fewer Dams that survive winter high flows
• Overall Beaver population trend not
known, just dams and ponds.
Trends in Number, Size of Beaver
Ponds in the Coast Range
• A major decline over the past two decades
• Loss of large winter-persistent ponds
POSSIBLE CAUSES OF DECLINE
•
•
•
•
•
•
•
Natural Population Fluctuations
Forest Succession
Disease – Tularemia, perhaps others
Trapping and Shooting
Increased Cougar depredations
Reduced food supply
Reduced supply of building materials