Aspects of each of these recommendations have been
implemented by nongovernmental organizations such as
Restore America’s Estuaries (RAE and NOAA, 2002);
however, the implementation of an integrated strategy
remains a work in progress. The US Army Corps of Engineers has identified ecosystem restoration as one of its
three primary missions and has the regulatory role and
technical expertise to make a significant contribution to
a national strategy (USACE, 2007a).
The realization that estuarine habitats provide significant ecosystem services (i.e., provisioning, regulating,
cultural, and supporting benefits to people) has reinforced
global efforts to protect, conserve, and restore these habitats (MEA, 2005). It has been long understood that estuarine habitats support fisheries resources. Many habitats
produce vast amounts of organic matter that support the
food web and serve as feeding, rearing, and refuge habitat
for many fisheries species. Further, coastal and estuarine
habitats have contributed to the resilience of coastlines to
withstand and recover from storm surge and other natural
disturbances that could harm coastal communities, coastal
resources, and infrastructure. Wetlands are well known for
their ability to trap suspended sediments, process organic
matter and inorganic nutrients, and attenuate floods. Estuarine and near-coastal shallow-water habitats can be major
sinks of carbon dioxide, thus capable of mitigating anthropogenic carbon dioxide emissions contributing to global
warming and ocean acidification (MEA, 2005). Therefore,
restoring habitats to restore ecosystem services has
become another goal of programs in many countries.
Elements of successful estuarine habitat restoration
The establishment of clearly articulated restoration goals and
selection of the right restoration strategy to meet those goals
are critical to successful habitat restoration. The results of
actions taken on habitat restoration sites increasingly inform
our understanding of ecosystems and enhance our ability
to accurately predict how well-planned actions will meet
restoration goals. Successful estuarine habitat restoration
considers the characteristics and processes of the overall
landscape within which the restoration site is found, as well
as an array of restoration actions. Solid project management
from planning through implementation and project evaluation ensures success; restoration projects typically involve
well-conceived monitoring, data management, dissemination of results, and adaptive management to continuously
improve processes and understanding. The use of a variety
of models helps prioritize projects, develop performance
criteria from goals, improve project design, assist with site
selection, etc. Each restoration effort aims to ensure longterm habitat viability and stability in the face of disturbances
often relative to reference (control) sites that represent the
targeted natural condition. Beyond the costs of habitat revegetation, restoration involves the costs of site assessments,
site acquisition, site preparation, safety considerations,
permitting, and project management.
Defining restoration goals
The general intent of tidal marsh restoration is a net
improvement of the ecological functions and services of
the marsh. This suggests that upon completion of a
restorative action, a marsh will exhibit quantified
improvement in size, structural features (e.g., vegetative
cover, species richness), and function (e.g., productivity,
use by wildlife). Practitioners have learned that satisfying
this intent generally requires far more than simply
installing marsh plants at a site.
The effect an ecosystem has on restoring habitats is
exemplified by how tidal wetlands depend upon processes
in their landscape for support. For example, the accretion
of the marsh plain depends on a supply of inorganic
sediment from the surrounding upland. If the sediment is
not available, marshes tend to subside (i.e., sink), which
forces changes in their structure and function. Ideally,
the landscape provides the sediment, hydrology, and nutrients that form and help sustain the tidal wetland. It is well
documented that the probability of successful restoration
is largely dependent on the degrees of site and landscape
disturbance (NRC, 1992). Consideration of the health of
landscape processes is essential in the planning phase of
a site-specific restoration project.
Goals for a habitat restoration project must be specific
enough for the proper restoration strategies and actions
to be identified and implemented. Goals can be defined
in terms of the structural (i.e., species composition and
abundance) or functional (e.g., productivity, nutrient
processing, organic matter production) state that the project site will reach after implementation of restorative
actions. The theory behind ecosystem-based approaches
to aquatic ecosystem restoration was outlined by the
NRC (1992). A general model for ecosystem state
(Figure 1) is a way to visualize the present and historical
states of the system, as well as identify restoration goals.
This model assumes there is a positive relationship
between the structure and the function of an ecosystem.
To simplify the model, the axes can be divided into low,
moderate, and high ecosystem functioning to define nine
system states. Dividing the matrix into three levels
(1) acknowledges the uncertainty about the relationship
between structural and functional ecosystem components
and (2) recognizes the natural dynamic variability associated with structural conditions and functional conditions
within a state. The natural climax structure (upper righthand box) of an ecosystem, habitat, or community has
a corresponding and predictable functional condition.
The targeted end state, then, would represent a system that
is fully developed, optimally biodiverse, self-maintaining,
and resilient enough to withstand and recover from
disturbances.
For example, the upper right-hand box labeled desired
ecosystem state might represent the pre-disturbance conditions of the lower Columbia River and estuary
(Johnson et al., 2003). It can also represent the desired
state of the system after restoration. The present condition
ESTUARINE HABITAT RESTORATION
275
implemented by nongovernmental organizations such as
Restore America’s Estuaries (RAE and NOAA, 2002);
however, the implementation of an integrated strategy
remains a work in progress. The US Army Corps of Engineers has identified ecosystem restoration as one of its
three primary missions and has the regulatory role and
technical expertise to make a significant contribution to
a national strategy (USACE, 2007a).
The realization that estuarine habitats provide significant ecosystem services (i.e., provisioning, regulating,
cultural, and supporting benefits to people) has reinforced
global efforts to protect, conserve, and restore these habitats (MEA, 2005). It has been long understood that estuarine habitats support fisheries resources. Many habitats
produce vast amounts of organic matter that support the
food web and serve as feeding, rearing, and refuge habitat
for many fisheries species. Further, coastal and estuarine
habitats have contributed to the resilience of coastlines to
withstand and recover from storm surge and other natural
disturbances that could harm coastal communities, coastal
resources, and infrastructure. Wetlands are well known for
their ability to trap suspended sediments, process organic
matter and inorganic nutrients, and attenuate floods. Estuarine and near-coastal shallow-water habitats can be major
sinks of carbon dioxide, thus capable of mitigating anthropogenic carbon dioxide emissions contributing to global
warming and ocean acidification (MEA, 2005). Therefore,
restoring habitats to restore ecosystem services has
become another goal of programs in many countries.
Elements of successful estuarine habitat restoration
The establishment of clearly articulated restoration goals and
selection of the right restoration strategy to meet those goals
are critical to successful habitat restoration. The results of
actions taken on habitat restoration sites increasingly inform
our understanding of ecosystems and enhance our ability
to accurately predict how well-planned actions will meet
restoration goals. Successful estuarine habitat restoration
considers the characteristics and processes of the overall
landscape within which the restoration site is found, as well
as an array of restoration actions. Solid project management
from planning through implementation and project evaluation ensures success; restoration projects typically involve
well-conceived monitoring, data management, dissemination of results, and adaptive management to continuously
improve processes and understanding. The use of a variety
of models helps prioritize projects, develop performance
criteria from goals, improve project design, assist with site
selection, etc. Each restoration effort aims to ensure longterm habitat viability and stability in the face of disturbances
often relative to reference (control) sites that represent the
targeted natural condition. Beyond the costs of habitat revegetation, restoration involves the costs of site assessments,
site acquisition, site preparation, safety considerations,
permitting, and project management.
Defining restoration goals
The general intent of tidal marsh restoration is a net
improvement of the ecological functions and services of
the marsh. This suggests that upon completion of a
restorative action, a marsh will exhibit quantified
improvement in size, structural features (e.g., vegetative
cover, species richness), and function (e.g., productivity,
use by wildlife). Practitioners have learned that satisfying
this intent generally requires far more than simply
installing marsh plants at a site.
The effect an ecosystem has on restoring habitats is
exemplified by how tidal wetlands depend upon processes
in their landscape for support. For example, the accretion
of the marsh plain depends on a supply of inorganic
sediment from the surrounding upland. If the sediment is
not available, marshes tend to subside (i.e., sink), which
forces changes in their structure and function. Ideally,
the landscape provides the sediment, hydrology, and nutrients that form and help sustain the tidal wetland. It is well
documented that the probability of successful restoration
is largely dependent on the degrees of site and landscape
disturbance (NRC, 1992). Consideration of the health of
landscape processes is essential in the planning phase of
a site-specific restoration project.
Goals for a habitat restoration project must be specific
enough for the proper restoration strategies and actions
to be identified and implemented. Goals can be defined
in terms of the structural (i.e., species composition and
abundance) or functional (e.g., productivity, nutrient
processing, organic matter production) state that the project site will reach after implementation of restorative
actions. The theory behind ecosystem-based approaches
to aquatic ecosystem restoration was outlined by the
NRC (1992). A general model for ecosystem state
(Figure 1) is a way to visualize the present and historical
states of the system, as well as identify restoration goals.
This model assumes there is a positive relationship
between the structure and the function of an ecosystem.
To simplify the model, the axes can be divided into low,
moderate, and high ecosystem functioning to define nine
system states. Dividing the matrix into three levels
(1) acknowledges the uncertainty about the relationship
between structural and functional ecosystem components
and (2) recognizes the natural dynamic variability associated with structural conditions and functional conditions
within a state. The natural climax structure (upper righthand box) of an ecosystem, habitat, or community has
a corresponding and predictable functional condition.
The targeted end state, then, would represent a system that
is fully developed, optimally biodiverse, self-maintaining,
and resilient enough to withstand and recover from
disturbances.
For example, the upper right-hand box labeled desired
ecosystem state might represent the pre-disturbance conditions of the lower Columbia River and estuary
(Johnson et al., 2003). It can also represent the desired
state of the system after restoration. The present condition
ESTUARINE HABITAT RESTORATION
275