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A Conservation Assessment of West Coast (USA) Estuaries

TitleA Conservation Assessment of West Coast (USA) Estuaries
Publication TypeReport
Year of Publication2011
AuthorsGleason, MG, Newkirk, S, Merrifield, MS, Howard, J, Cox, R, Webb, M, Koepcke, J, Stranko, B, Taylor, B, Becker, MW, Fuller, RG, Dye, P, D. Schaaf, V, Carter, J
Tertiary AuthorsConservancy, TNature
InstitutionThe Nature Conservancy
CityArlington, VA
KeywordsGIS and oceanography, estuaries, classification, Restore America's Estuaries (RAE)

The land-sea interface is one of the most ecologically rich
and complex areas on Earth. Occupying the unique zone
where terrestrial, freshwater, and marine realms converge,
estuaries are shaped by complex exchanges of energy,
water, nutrients, sediments, and biota. They are enormously
productive areas, providing habitat for an extraordinary
array of fish, shellfish, birds, and mammals.
Coastal areas where estuaries are found are also home
to more than sixty percent of humanity. This isn’t a
coincidence: people gravitate toward coastal areas
because they provide numerous ecosystem services
upon which we depend. However, dense human
habitation comes with a cost—temperate estuaries
are some of the most degraded environments on the
planet, making their protection and restoration a top
conservation priority.

While significant progress has been made over the past
few decades in improving estuarine water quality, restoring
wetland habitats, and incorporating estuarine habitats into
managed areas, estuarine conservation efforts along the
United States (U.S.) West Coast—including Washington,
Oregon, and California—have generally proceeded on a
bay-by-bay basis, with relatively little coordination among
sites or across the region. In addition, conservation
planning for estuaries has not historically been well
integrated across terrestrial, freshwater, and marine realms
to address cross-realm threats to estuarine health. Given
the strong similarities in basic ecology and threats faced
by many of the region’s estuaries, a coordinated effort to
assess regional patterns and develop integrated multi-site
strategies is likely to improve conservation effectiveness at
both the local and regional scales.

This assessment outlines an enhanced planning approach
for West Coast estuaries that incorporates an evaluation
of the regional context for estuarine conservation and
recommends an approach to site-scale planning with
more focus on ecological processes and functions. At
the regional scale, conservation planning should seek to
provide context (status of conservation targets, distribution
of threats, management and ownership patterns,
conservation opportunities) supporting conservation
investment at individual estuaries, as well as to identify
groupings of estuaries that share similar features
(conservation targets, threats, ownership patterns, type
of estuary) for multi-site conservation strategies. At the
site scale, conservation plans should aim to maintain
the full spectrum of estuary zones, processes and
functions; safeguard critical connections among terrestrial,
freshwater, and marine realms; and safeguard ecosystem
service values. At the same time, site-scale efforts should
be grounded in a regional context and geared toward
delivering conservation outcomes that have relevance at
scale. Further, ecological linkages should be considered
when developing conservation action plans to promote
the long-term viability of estuaries. Rather than using
only species- and habitat-level conservation targets, an
enhanced conservation planning approach for estuaries
should incorporate ecological processes, functions, and
other system-level conservation targets that integrate
across terrestrial, freshwater, and marine realms.
Understanding how different stressors act to alter those
processes and functions is critical to developing effective
conservation strategies.

This assessment is based, in part, on a geographic
information system (GIS) database that contains spatial
data for 146 estuaries and their associated catchments
(adjacent watersheds) in California, Oregon, and
Washington. The West Coast Estuary Database provides
regional data for characterization of spatial patterns of the
distribution of selected biodiversity targets and threats.
This database, available to both technical and nontechnical
users (go to
for more information), includes 27 variables that
characterize some key biophysical and human use
parameters of these estuaries.