Life on a sandy edge: conserving

beach ecosystems in the face of rising

seas

Jenny DuganMarine Science InstituteUniversity of California

Santa Barbara

Beaches = ~75% of open coast

• Recreation

• Coastal economy

• Aesthetics

• Cultural identity

Iconic Assets

Beach ecosystems are more than sand

Beaches as Ecosystems

Beach Ecosystem Functions & Services

• Water filtration• Nutrient cycling

Water filtration

Nutrient cycling

Beaches can absorb wave energy

Beach Ecosystem Functions & Services

Accumulate & Store Sand

Linked Dunes & Beaches as resilient buffers to climatic forcing

C. Bowdish

High Biodiversity & Rich Prey Resources for Birds & Fish

Beach Fisheries:

Pismo Clams

Surf Fishing

California Grunion

Grunion.orgJ. Flannery

A Special Fish

Critical Habitat & Prey for Shorebirds

Western Snowy Plover young chick with prey

C. Bowdish

Northern Elephant Seals

Beach EcosystemsHighly mobile animals and no attached plants

Unconsolidated sedimentsExtremely dynamic zonation

Variation in elevation & widthStrong influence of: – Wave exposure– Sediment supply– Habitat alteration

Beach Management: Grooming

S. Cal. Groomed Beaches = ~45% (>100 miles)

Post Hurricane Beach Filling: Galveston, Texas

Goleta Beach fill & sediment plume February 2011

Sandy Beaches

• Animals adapted to frequent disturbance of sand by waves & wind

• Rapid recovery from impacts assumed• Ecological monitoring absent

Coastal Squeeze Development Sea level rise

The Last BeachPilkey &

Cooper 2014

Predicted loss of up to 67% of beaches by 2100Vitousek et al 2017

Coastal Ecosystem Vulnerability Assessment:

Sandy Beaches Santa Barbara County

Jenny Dugan, Dave Hubbard, Alex Snyder*, Kyle Emery, Patrick Barnard*, Dan Hoover*

Marine Science Institute, UC Santa BarbaraUSGS Pacific Coastal & Marine Science Center, Santa Cruz*

Objectives:

• Integrate ecology & geomorphology of beaches

• Project ecosystem responses• Assess vulnerability of sandy beach

ecosystems to climate change

Upper/”dry”

High Tide

Strand HTS

Beach

Zones

Mid/damp

Low/wet

Water Table

Outcrop WTO

Upper beach zones

• Nesting Habitat• Ecotone - coastal

strand vegetation• Wrack deposition &

processing• 40% of biodiversity

• Buffer zone for mobile intertidal life during storms

ApproachGeo-referenced beach profiles,

widths & coastal

processes

Projected responses of beach ecosystem features

CoSMoS 3.0 Runup &

Shoreline Change

Ecological Framework & Validation

Total Water Level (TWL) as an Ecological Datum

• TWL = Predicted tide level + wave runup (incl wave setup)

• Approximation of high tide strand line (HTS),= lower bound upper intertidal zone

• Key beach taxa and functions e.g. talitrid amphipods, wrack, sand accumulation

• Critical boundary for beach nesting wildlife e.g. snowy plovers, sea turtles & grunion

• Annual peak TWL sets lower edge of coastal strand zone

Vulnerability of Beaches to Climate Change

Landward boundary determines scope for migration of ecosystem

– Bluffs

– Dunes

– Armoring and infrastructure

– Habitat alteration

Bluff-Backed Beaches85% loss of

upper beach zone

Armored Beaches99% loss of upper zone

Coastal SqueezeArroyo Quemado Seawall

•Upper beach zones already lost on many armored beaches

Dune-backed Beaches~ 60% loss of upper zone at 50 cm SLR

15% remains at 150 cm

Landward intertidal boundary moves inland:Erosion of dunes - Fall 2014

• Dune habitat area declines as beach retreats

Groomed Beaches 50% loss of upper zone at 50 cm SLR

< 5% remains at 150 cm

Beach Ecosystems Highly Vulnerable Tipping Point ~50 cm SLR

CoSMoS 3.0 Projections

Groomed Beaches

• Ecosystems degraded by grooming• Potential for restoration & conservation

Beaches as wetlands

Conserving Sandy Beach Ecosystems

• Manage more beaches for biodiversity & ecological function

• Restore resiliency: provide space for beaches to move

• Minimize impacts and interventions

• Maintain/enhance connectivity with land & sea

• Identify and restore beaches with scope for retreat

Made possible by support from:

• NOAA Climate Program Office• Sea Grant (National Office)• Santa Barbara Coastal LTER• National Science Foundation• United States Geological Survey• UCSB Coastal Fund

Beach Ecosystem Vulnerability Assessment

Questions?

Thank you!

Example

Bluff-backed beach

Arroyo Burro

SLR = 0 cm

SLR = 50 cm

SLR = 100 cm

SLR = 150 cm

SLR = 200 cm

SLR = 500 cm

•90% loss of upper beach zone with 50 cm SLR

Upp

er B

each

Zon

e W

idth

(m)

West East

CoSMoS 3.0 Model projectionsUpper Beach Zone

Armored beachSanta Claus Lane

•99% loss of upper beach zone with 50 cm SLR

Upp

er B

each

Zon

e W

idth

(m)

SLR = 0 cm

SLR = 50 cm

SLR = 100 cm

SLR = 150 cm

SLR = 200 cm

SLR = 500 cm

West East

CoSMoS 3.0 Model projectionsUpper Beach Zone

Dune-backed Beach

Sands/Ellwood

Upp

er B

each

Zon

e W

idth

(m)

SLR = 0 cm

SLR = 50 cm

SLR = 100 cm

SLR = 150 cm

SLR = 200 cm

SLR = 500 cm

West East

CoSMoS 3.0 Model projectionsUpper Beach Zone

•>60% loss of upper beach zone with 50 cm SLR•Much reduced upper beach zone, 9%, remains with 200 cm SLR

Groomed/Filled East Beach

•50% loss of upper beach zone with 50 cm SLR•Greatly reduced upper beach zone <5 m width persists with 150 cm SLR

Upp

er B

each

Zon

e W

idth

(m)

SLR = 0 cm

SLR = 50 cm

SLR = 100 cm

SLR = 150 cm

SLR = 200 cm

SLR = 500 cm

West East

CoSMoS 3.0 Model projectionsUpper Beach Zone

Key Axes of Influence