Sea level rise and shorebirds grays harbor national wildlife refuge
Sea Level Rise and Shorebirds: A Look at Grays Harbor, WA
Danika Didur-Tate, Nisqually National Wildlife Refuge Complex
• Members of the avian order Charadriiformes (gulls, auks included). Used to be suborder Charadrii.
Called ‘waders’ everywhere but NA, where term means storks and herons. ‘shorebirds’ in NA.
• ~220 species worldwide, ~50 in NA
• Characterized by long legs for wading in wetland, coastal areas. Typically skinny, varying-lengthed bills
for probing in mud/sand for invertebrates (worms, early planktonic forms of bivalves, crustaceans,
• Fairly small, well camouflaged
• Niche order, only living on shoreline, mudflat “edges”. Each species more niche, length of leg
determines precise depth of water they use. Length of beak relates to which specific organisms they
can eat. GLC does not favor niche sp.
• Long distance migrants. Brief stop overs. Huge energy requirements. Little stint breeds in arctic, over-
winters in s. hemisphere. Greater yellowlegs breeds in northern NA, overwinters tip of SA.
• Shallow gradient estuarine mud flats, forming wide bands of useable habitat.
• Open areas. Too many trees in mud flat make them less maneuverable. Too many birds in small area
make them less maneuverable. Can’t escape predators.
• Open ocean shoreline ok, but less abundant food than mudflats. Also, not all shorebirds are adapted to
coastal wave action.
• Can’t use open ocean. Can’t use enclosed or crowded areas.
SLR and estuaries
• SLR creates estuaries. Coastal plain, or drowned river, estuaries created when ocean fills existing river
valley. GH estuary is drowned river estuary created after last ice age.
• SLR in the short term means current mud flats will be inundated more frequently and for longer
periods of time
• B/c of steep topography surrounding GH, the new mudflats potentially created would be extremely
• As sea continues inland, upland and salt marsh converted to mudflat. Trees in upland die in salt water,
create obstacles blocking in shorebirds and perches for raptors.
• Salt marsh → mudflat → open water (never recedes, even at low tide)
• B/c of topography, mud flat may be created with SLR, but probably not as much as is being lost
SLR in Grays Harbor
• The topography around the harbor is very steep, very quickly. Sheer walls. “Bathtub” effect.
• GHNWR’s mission statement is about conserving shorebirds, specific shorebirds. If/when there is no
longer mud flat in NWR, GHNWR is legally bound to find a way to continue to conserve. General ideas:
o Purchasing more land
o Building dike/impoundment to maintain mudflat (no inflow of nutrients)
Breakwaters influence erosion
o “beach nourishment”, adding sediment and building up mudflat elevation
o Discussion about Chehalis River sediment deposition. Would deposition keep up with SLR? Can
we aid it? Cutting down trees, agriculture, storms. (Chehalis to be dammed, for flood control)
• Filter feeders live in mudflats
• Raptor populations (p. falcon and merlin) eat shorebirds
• Forage fish, significant part of marine food web (eelgrass)
• Coastal shores refuge for shorebirds when mudflats covered at high tide, but SLR will decrease amount
of coastal shore. Narrower band, destabilized dunes, potential “bathtub”
• Shorebirds follow food abundance; “blooms” of planktonic life (DEFINE) related to currents and
temperatures. Sea temp raises, currents change, “blooms” could change too, shorebirds in wrong place
at wrong time.
SLR 0.69 meters (27.3 inches) by 2100. Puget Sound, SW WA and NW OR
• Estuarine beaches will undergo inundation and erosion to the tune of a 65 percent loss.
• As much as 44 percent of tidal flat will disappear.
• 13 percent of inland fresh marsh and 25 percent of tidal fresh marsh will be lost.
• 11 percent of inland swamp will be inundated with salt water, while 61 percent of tidal swamp will be
• 52 percent of brackish marsh will convert to tidal flats, transitional marsh and saltmarsh.
• 2 percent of undeveloped land will be inundated or eroded to other categories across all study areas.
Application of the Sea-Level Affecting Marshes Model (SLAMM 6) to Grays Harbor NWR
Warren Pinnacle Consulting, September 2011