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

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