restoration plan for submerged aquatic vegetation provides an example of how to relate performance criteria to
goals using a conceptual model (Batiuk et al., 1992;
Batiuk et al., 2000).
Geographic information system models
GIS-based models use knowledge of the spatial variability
of factors that drive or limit species distribution, habitat
quality, or ecosystem services. GIS-based models and
applications are generally used during the project planning
phase to assist with site selection. However, approaches,
models, and applications vary widely. Process-based GIS
models, such as the Wave Energy Model (WEMo;
Malhotra and Fonseca, 2007), calculate quantitative
physical parameters so that local data can be used to
identify zones that meet thresholds or ranges of suitable
values. Optimization routines, such as those within
Marxan, examine different clusters of potential conservation areas to meet targets and minimize costs (Airame
et al., 2003; Ball et al., 2009).
Models based on expert knowledge and ranked quantitative assessments of environmental stressors and functions are used to prioritize restoration areas (Diefenderfer
et al., 2009). Participatory GIS approaches (e.g., NOAA’s
Habitat Priority Planner) use stakeholder criteria to visualize alternative scenarios (Bamford et al., 2009).
Recently, GIS models have been integrated with other
software to expand visualization and analytical capabilities. For example, the Marine Geospatial Ecology Tools
(MGET, Roberts et al., 2010) links ArcGIS with the statistical software R thereby enabling planners to predict
spatial occurrences of sites and environmental conditions.
The Gulf of Mexico Regional Collaborative integrates
web models with conceptual model creation software
(www.gomrc.org). With Envision, plug-ins enable development of future land-use scenarios that feed into habitat
assessment models (Hulse et al., 2008). Finally,
NatureServe’s Ecosystem-Based Management Tools Network provides one of the most comprehensive interfaces
to learn about and access spatially aware tool sets (www.
natureserve.org).
Operational numerical models
Numerical models can help the planning process by facilitating sensitivity analysis and prediction of controlling
factor conditions such as hydroperiod (e.g., Burdick,
2000; Yang et al., 2010). Hydrology is of critical importance to water resource projects and the science is well
developed. Hydrologic modeling is frequently conducted
during restoration project planning such as in the
restoration of the Florida Everglades (Fitz et al., 1996).
Numerical ecological models are less frequently used
because the relationships among ecological parameters
and the physical – chemical environment often are not
well understood. However, ecological models have
provided tools to describe predicted trajectories of
ecosystem development under variable conditions.
Modeling can complement field studies by improving
the understanding of the relative effects of processes
operating at different scales and thus improve project
design, implementation, and adaptive management
(Twilley et al., 1998). Models can also be used to help
select performance criteria.
Population models
Population models of focal plant or animal species are
used to help decide which processes are critical to
explaining population and community dynamics, what
form those processes take, and the value of parameters
such as reproductive and survival rates. The process of
developing a numerical model serves to formalize the current state of knowledge about the system along with critical uncertainties. Once developed, the model can predict
the outcomes of management actions and support decisions. Finally, numerical models provide a mechanism
for prioritizing research according to what will most
improve the understanding of the system and the strength
of the decision-making process.
Prioritization of restoration projects
Programs to restore habitats and ecosystems often have to
prioritize which projects to undertake, what level of effort
to devote to the projects, and where they should be
located. Factors often included in systematic prioritization
efforts include rare habitats that were once abundant, habitats that are critically important to and that allow direct
access by endangered or threatened species, habitats that
provide functions critical to an ecosystem (e.g., waterquality improvement), and habitats that would buffer
disturbances from storm damage, flooding, etc. Ideally,
projects are located at or near where these priority habitats
once existed. Projects can be evaluated for their net
improvement of the ecosystem. For example, projects to
restore floodplain and surge plain habitats in the Columbia
River estuary are prioritized by the habitat accessibility to
juvenile salmon, capacity to support these fish onsite and
offsite, and probability of restoration success (Thom
et al., 2011b). The latter factor relates to the ability of the
habitat to be resilient to withstand and recover from normal levels of natural disturbances (e.g., pulsed flood
events). Cost can enter into these prioritization efforts,
where the largest increase in function over the largest area
would be realized for the lowest cost.
Costs of habitat restoration
Habitat restoration involves far more than planting vegetation. As noted above, it involves assessing, acquiring, and
preparing the restoration site, addressing related safety
considerations and permitting needs, and managing the
project from start to finish. If a marsh does not exist at
a site, there must be a reason why (Borde et al. in preparation). Often, restoring a marsh requires physical manipulations of a site. Heavy equipment may be necessary to
remove obstructions to hydrology, reshape the ground,
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ESTUARINE HABITAT RESTORATION
goals using a conceptual model (Batiuk et al., 1992;
Batiuk et al., 2000).
Geographic information system models
GIS-based models use knowledge of the spatial variability
of factors that drive or limit species distribution, habitat
quality, or ecosystem services. GIS-based models and
applications are generally used during the project planning
phase to assist with site selection. However, approaches,
models, and applications vary widely. Process-based GIS
models, such as the Wave Energy Model (WEMo;
Malhotra and Fonseca, 2007), calculate quantitative
physical parameters so that local data can be used to
identify zones that meet thresholds or ranges of suitable
values. Optimization routines, such as those within
Marxan, examine different clusters of potential conservation areas to meet targets and minimize costs (Airame
et al., 2003; Ball et al., 2009).
Models based on expert knowledge and ranked quantitative assessments of environmental stressors and functions are used to prioritize restoration areas (Diefenderfer
et al., 2009). Participatory GIS approaches (e.g., NOAA’s
Habitat Priority Planner) use stakeholder criteria to visualize alternative scenarios (Bamford et al., 2009).
Recently, GIS models have been integrated with other
software to expand visualization and analytical capabilities. For example, the Marine Geospatial Ecology Tools
(MGET, Roberts et al., 2010) links ArcGIS with the statistical software R thereby enabling planners to predict
spatial occurrences of sites and environmental conditions.
The Gulf of Mexico Regional Collaborative integrates
web models with conceptual model creation software
(www.gomrc.org). With Envision, plug-ins enable development of future land-use scenarios that feed into habitat
assessment models (Hulse et al., 2008). Finally,
NatureServe’s Ecosystem-Based Management Tools Network provides one of the most comprehensive interfaces
to learn about and access spatially aware tool sets (www.
natureserve.org).
Operational numerical models
Numerical models can help the planning process by facilitating sensitivity analysis and prediction of controlling
factor conditions such as hydroperiod (e.g., Burdick,
2000; Yang et al., 2010). Hydrology is of critical importance to water resource projects and the science is well
developed. Hydrologic modeling is frequently conducted
during restoration project planning such as in the
restoration of the Florida Everglades (Fitz et al., 1996).
Numerical ecological models are less frequently used
because the relationships among ecological parameters
and the physical – chemical environment often are not
well understood. However, ecological models have
provided tools to describe predicted trajectories of
ecosystem development under variable conditions.
Modeling can complement field studies by improving
the understanding of the relative effects of processes
operating at different scales and thus improve project
design, implementation, and adaptive management
(Twilley et al., 1998). Models can also be used to help
select performance criteria.
Population models
Population models of focal plant or animal species are
used to help decide which processes are critical to
explaining population and community dynamics, what
form those processes take, and the value of parameters
such as reproductive and survival rates. The process of
developing a numerical model serves to formalize the current state of knowledge about the system along with critical uncertainties. Once developed, the model can predict
the outcomes of management actions and support decisions. Finally, numerical models provide a mechanism
for prioritizing research according to what will most
improve the understanding of the system and the strength
of the decision-making process.
Prioritization of restoration projects
Programs to restore habitats and ecosystems often have to
prioritize which projects to undertake, what level of effort
to devote to the projects, and where they should be
located. Factors often included in systematic prioritization
efforts include rare habitats that were once abundant, habitats that are critically important to and that allow direct
access by endangered or threatened species, habitats that
provide functions critical to an ecosystem (e.g., waterquality improvement), and habitats that would buffer
disturbances from storm damage, flooding, etc. Ideally,
projects are located at or near where these priority habitats
once existed. Projects can be evaluated for their net
improvement of the ecosystem. For example, projects to
restore floodplain and surge plain habitats in the Columbia
River estuary are prioritized by the habitat accessibility to
juvenile salmon, capacity to support these fish onsite and
offsite, and probability of restoration success (Thom
et al., 2011b). The latter factor relates to the ability of the
habitat to be resilient to withstand and recover from normal levels of natural disturbances (e.g., pulsed flood
events). Cost can enter into these prioritization efforts,
where the largest increase in function over the largest area
would be realized for the lowest cost.
Costs of habitat restoration
Habitat restoration involves far more than planting vegetation. As noted above, it involves assessing, acquiring, and
preparing the restoration site, addressing related safety
considerations and permitting needs, and managing the
project from start to finish. If a marsh does not exist at
a site, there must be a reason why (Borde et al. in preparation). Often, restoring a marsh requires physical manipulations of a site. Heavy equipment may be necessary to
remove obstructions to hydrology, reshape the ground,
282
ESTUARINE HABITAT RESTORATION