reclamation, and even mitigation. Yet, each of these terms
has distinctly different meanings as defined in the literature. Unless otherwise specified, the term restoration
refers to any form of human intervention with the intent
of improving upon the existing condition of an ecosystem
or habitat.
The term “habitat” generally refers to a more or less
discrete biophysically structured element of an ecosystem.
A habitat can also be defined as the portion of an ecosystem where a species lives, feeds, and reproduces.
Commonly referred to estuarine habitat types include tidal
forested swamps, shrub scrub wetlands, emergent
marshes, seagrass meadows, seaweed beds, and
unvegetated channels and flats (Cowardin et al., 1979).
An estuarine ecosystem generally includes a complex of
several habitat types that interact within a geomorphic setting along the estuarine gradient.
Introduction
Restoring estuarine habitats generally means repairing
damages caused by humans and natural forces. Because
of the extensive human occupation, development, and
use of coastal areas for centuries, the extensive estuarine
habitats have been either destroyed or significantly
impaired.
Estuarine habitat alteration
Of the prehistoric area of natural habitats in estuaries,
a large but poorly quantified portion has either been
destroyed or highly altered (NRC, 1992). In the United
States, much of this change occurred from the late 1800s
with the development of ports, commerce, and agriculture.
Alterations and losses continued at a rapid pace until
approximately the late- 1960s with the advent of environmental laws (e.g., US National Environmental Policy
Act). Loss of estuarine habitat is common on most major
continents (MEA, 2005). Estuaries in Europe showed
alterations and loss. Extensive estuarine modifications in
East Asia have been ongoing for millennia but estuaries
have suffered rapid losses over the past several decades
because of development actions. Estuaries in the Middle
East, Africa, and Australia have also suffered habitat
losses.
In general, coastal and estuarine habitats have undergone rapid losses in most regions of the world, largely
because of human development in coastal areas. The
worldwide decline in seagrasses has been termed
a “global crisis” (Orth et al., 2006). Similar degrees of
losses have been estimated for mangrove and tidal
swamps (Mitch and Gosselink, 1993). Tidal marshes
may be the most documented estuarine habitats in terms
of ecology and changes. Data show that the total tidal
marsh area in the United States has decreased from an estimated 2,023,000 ha in 1950 to about 1,850,000 ha in 2004
(Dahl, 2006). Currently, the greatest rates of tidal marsh
loss exist in the Gulf of Mexico region where it is
estimated that approximately 2,331 ha are lost per year
(Dahl, 2006). Between 1986 and 2004, the United States
lost 0.9 % of estuarine emergent wetlands on an annual
basis (Dahl, 2006). Many bays and estuaries have lost
more than 90 % of their tidal wetland area, especially in
urban areas, and many others are in a state of poor or
declining health (Borde et al., in preparation). Human
alterations often associated with urban development, such
as the construction of infrastructure, can have permanent
and irreversible effects on tidal marshes. Other humanrelated alterations, such as dredging, filling, ditching, diking, chemical contamination, and hydrologic changes, are
potentially reversible with restoration. Natural stressors to
estuarine habitats include climate variability, catastrophic
storm events, sea-level rise, unexplained marsh dieback,
and invasive species.
Advent of estuarine habitat restoration
Restoration of tidal wetlands in the United States has one
of the longest histories among all restoration efforts
(NRC, 1992). Planting of Spartina marshes in the eastern
United States commenced in earnest during the 1970s
and demonstrated that marshes could be created and
restored. With the development of wetland regulations as
part of the US Clean Water Act, wetland mitigation projects were designed to compensate for damages associated
with development, which triggered development of tidal
wetland restoration science. Over a century ago, Ducks
Unlimited and other organizations developed strategies
to conserve and restore tidal wetlands. In 1990, the
National Oceanic and Atmospheric Administration
(NOAA) established its Office of Restoration and
published a book of case studies for restoration of marine
habitats that included tidal wetlands (Thayer, 1992). One
encouraging strategy is the focus on community-based
projects that have strong local support. The NOAA conducts workshops and publishes guidance documents
(Thayer, 1992; Hackney, 2000; Thayer et al., 2003; Thayer
and Kentula, 2005) to foster the underlying science.
The National Research Council (1992) recommended
to the Congress that any redirection of federal policies
and programs for aquatic ecosystem restoration should
consider the following:
• The use of a landscape perspective in restoration efforts
• The use of adaptive planning and management
• Evaluating and ranking restoration alternatives based
on assessment of opportunity–cost rather than on traditional benefit–cost analysis
• Incorporating the definition of restoration as the return
of an ecosystem to a close approximation of its condition prior to disturbance
• Reliance on nonfederal and federal units of government
to coordinate restoration programs in local areas
• Initiating an interagency and intergovernmental process
to develop a unified strategy for aquatic ecosystem
restoration
274
ESTUARINE HABITAT RESTORATION
has distinctly different meanings as defined in the literature. Unless otherwise specified, the term restoration
refers to any form of human intervention with the intent
of improving upon the existing condition of an ecosystem
or habitat.
The term “habitat” generally refers to a more or less
discrete biophysically structured element of an ecosystem.
A habitat can also be defined as the portion of an ecosystem where a species lives, feeds, and reproduces.
Commonly referred to estuarine habitat types include tidal
forested swamps, shrub scrub wetlands, emergent
marshes, seagrass meadows, seaweed beds, and
unvegetated channels and flats (Cowardin et al., 1979).
An estuarine ecosystem generally includes a complex of
several habitat types that interact within a geomorphic setting along the estuarine gradient.
Introduction
Restoring estuarine habitats generally means repairing
damages caused by humans and natural forces. Because
of the extensive human occupation, development, and
use of coastal areas for centuries, the extensive estuarine
habitats have been either destroyed or significantly
impaired.
Estuarine habitat alteration
Of the prehistoric area of natural habitats in estuaries,
a large but poorly quantified portion has either been
destroyed or highly altered (NRC, 1992). In the United
States, much of this change occurred from the late 1800s
with the development of ports, commerce, and agriculture.
Alterations and losses continued at a rapid pace until
approximately the late- 1960s with the advent of environmental laws (e.g., US National Environmental Policy
Act). Loss of estuarine habitat is common on most major
continents (MEA, 2005). Estuaries in Europe showed
alterations and loss. Extensive estuarine modifications in
East Asia have been ongoing for millennia but estuaries
have suffered rapid losses over the past several decades
because of development actions. Estuaries in the Middle
East, Africa, and Australia have also suffered habitat
losses.
In general, coastal and estuarine habitats have undergone rapid losses in most regions of the world, largely
because of human development in coastal areas. The
worldwide decline in seagrasses has been termed
a “global crisis” (Orth et al., 2006). Similar degrees of
losses have been estimated for mangrove and tidal
swamps (Mitch and Gosselink, 1993). Tidal marshes
may be the most documented estuarine habitats in terms
of ecology and changes. Data show that the total tidal
marsh area in the United States has decreased from an estimated 2,023,000 ha in 1950 to about 1,850,000 ha in 2004
(Dahl, 2006). Currently, the greatest rates of tidal marsh
loss exist in the Gulf of Mexico region where it is
estimated that approximately 2,331 ha are lost per year
(Dahl, 2006). Between 1986 and 2004, the United States
lost 0.9 % of estuarine emergent wetlands on an annual
basis (Dahl, 2006). Many bays and estuaries have lost
more than 90 % of their tidal wetland area, especially in
urban areas, and many others are in a state of poor or
declining health (Borde et al., in preparation). Human
alterations often associated with urban development, such
as the construction of infrastructure, can have permanent
and irreversible effects on tidal marshes. Other humanrelated alterations, such as dredging, filling, ditching, diking, chemical contamination, and hydrologic changes, are
potentially reversible with restoration. Natural stressors to
estuarine habitats include climate variability, catastrophic
storm events, sea-level rise, unexplained marsh dieback,
and invasive species.
Advent of estuarine habitat restoration
Restoration of tidal wetlands in the United States has one
of the longest histories among all restoration efforts
(NRC, 1992). Planting of Spartina marshes in the eastern
United States commenced in earnest during the 1970s
and demonstrated that marshes could be created and
restored. With the development of wetland regulations as
part of the US Clean Water Act, wetland mitigation projects were designed to compensate for damages associated
with development, which triggered development of tidal
wetland restoration science. Over a century ago, Ducks
Unlimited and other organizations developed strategies
to conserve and restore tidal wetlands. In 1990, the
National Oceanic and Atmospheric Administration
(NOAA) established its Office of Restoration and
published a book of case studies for restoration of marine
habitats that included tidal wetlands (Thayer, 1992). One
encouraging strategy is the focus on community-based
projects that have strong local support. The NOAA conducts workshops and publishes guidance documents
(Thayer, 1992; Hackney, 2000; Thayer et al., 2003; Thayer
and Kentula, 2005) to foster the underlying science.
The National Research Council (1992) recommended
to the Congress that any redirection of federal policies
and programs for aquatic ecosystem restoration should
consider the following:
• The use of a landscape perspective in restoration efforts
• The use of adaptive planning and management
• Evaluating and ranking restoration alternatives based
on assessment of opportunity–cost rather than on traditional benefit–cost analysis
• Incorporating the definition of restoration as the return
of an ecosystem to a close approximation of its condition prior to disturbance
• Reliance on nonfederal and federal units of government
to coordinate restoration programs in local areas
• Initiating an interagency and intergovernmental process
to develop a unified strategy for aquatic ecosystem
restoration
274
ESTUARINE HABITAT RESTORATION