Prioritizing marsh restoration needs throughout Chesapeake Bay
A new USGS study estimates potential losses of Chesapeake Bay salt marshes that could occur in the next 80 years if no marsh restoration is undertaken. Using a suite of models, USGS researchers identified how future potential marsh changes can be used to prioritize present-day site-specific planning and restoration needs.
Issue
Salt marshes are critical parts of Chesapeake Bay, providing habitat for fish and wildlife, storm protection for coastal communities and infrastructure, and recreational opportunities such as hunting, fishing, and boating. These important benefits are already being lost as changes in sediment supply, vertical land movement, and sea-level rise are converting the Bay’s marshes to open water (background photo). In response, federal, state, and local agencies are working to protect and restore the Bay’s salt marshes. Critical to this effort is having detailed information about marsh topography, hydrology, and plant diversity. This detailed information is, however, time-intensive and expensive to collect. Therefore, a landscape-level approach that identifies the timelines and risk of marsh transition to open water can be used to prioritize marsh restoration opportunities.
USGS Study
In partnership with Audubon, the USGS merged three separate salt-marsh models and used future sea-level rise scenarios to guide landscape-level planning and restoration. This new management-focused information provides detailed estimates about current Chesapeake Bay marsh conditions and when marshes begin to cross thresholds that limit their ecosystem services. A restoration-decision model was then used to estimate restoration needs for marshes in Maryland. This model considered interventions that include placing sediment to increase marsh elevation and improving hydrology to increase marsh vegetation.
Background photo: An aerial photograph of Blackwater National Wildlife Refuge. In this area of the refuge, vegetated marsh plain has been converted to open water due to sediment deficits, vertical land movement, and sea-level rise. Both sediment placement and hydrologic restoration can assist in increasing elevation and vegetation cover, thereby increasing resilience and ecosystem services. Credit: Chesapeake Bay Program.
Major Findings
- Across Chesapeake Bay, an overall marsh loss of 37% (404 km2) is predicted by 2110 under an accelerating 3-12 mm/year sea-level rise scenario (fig. 1). Predicted marsh loss increases to 89% (962 km2) by 2110 under an “upper limit of likely” sea-level rise scenario.
- Over half of the marshes in Maryland (400 km2) may currently require either no intervention or low effort hydrologic intervention, based on current elevation and vegetative cover.
- If no restoration actions are taken, about 94% (700 km2) of marshes in Maryland may require high effort interventions by 2070.
- The findings of this study demonstrate how multiple models with markedly different processes can be merged to guide marsh restoration needs.
Management Implications
Although salt marsh restoration ultimately requires a “boots-on-the-ground” approach to evaluate microtopography, small-scale hydrologic conditions, and plant diversity within a marsh before taking action, it is technically impossible to evaluate entire marsh complexes using such approaches. Therefore, a tiered, triage-like approach is often more appropriate. The models and approach described by this study represent a landscape-level assessment that enables practitioners to quickly identify marsh areas that are likely to require sediment or hydrologic interventions in the near future.
Incorporating additional information in decision making, such as distance to dredging operations or tidal restrictions, can help practitioners expand their decision matrices or create decision trees to determine whether restoration is appropriate and feasible. Efforts to incorporate the two restoration techniques considered by this study, sediment placement and hydrologic intervention, will be subject to sediment availability (ostensibly from dredging), access, and regulatory statutes. By mapping the proximity of focal marshes to dredged channels, tidal restrictions, access roads, and land ownership, practitioners can reach an important next level in a decision framework that aids landscape-level planning.
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Explore Web App: Marshes for Tomorrow
A new USGS study estimates potential losses of Chesapeake Bay salt marshes that could occur in the next 80 years if no marsh restoration is undertaken. Using a suite of models, USGS researchers identified how future potential marsh changes can be used to prioritize present-day site-specific planning and restoration needs.
Issue
Salt marshes are critical parts of Chesapeake Bay, providing habitat for fish and wildlife, storm protection for coastal communities and infrastructure, and recreational opportunities such as hunting, fishing, and boating. These important benefits are already being lost as changes in sediment supply, vertical land movement, and sea-level rise are converting the Bay’s marshes to open water (background photo). In response, federal, state, and local agencies are working to protect and restore the Bay’s salt marshes. Critical to this effort is having detailed information about marsh topography, hydrology, and plant diversity. This detailed information is, however, time-intensive and expensive to collect. Therefore, a landscape-level approach that identifies the timelines and risk of marsh transition to open water can be used to prioritize marsh restoration opportunities.
USGS Study
In partnership with Audubon, the USGS merged three separate salt-marsh models and used future sea-level rise scenarios to guide landscape-level planning and restoration. This new management-focused information provides detailed estimates about current Chesapeake Bay marsh conditions and when marshes begin to cross thresholds that limit their ecosystem services. A restoration-decision model was then used to estimate restoration needs for marshes in Maryland. This model considered interventions that include placing sediment to increase marsh elevation and improving hydrology to increase marsh vegetation.
Background photo: An aerial photograph of Blackwater National Wildlife Refuge. In this area of the refuge, vegetated marsh plain has been converted to open water due to sediment deficits, vertical land movement, and sea-level rise. Both sediment placement and hydrologic restoration can assist in increasing elevation and vegetation cover, thereby increasing resilience and ecosystem services. Credit: Chesapeake Bay Program.
Major Findings
- Across Chesapeake Bay, an overall marsh loss of 37% (404 km2) is predicted by 2110 under an accelerating 3-12 mm/year sea-level rise scenario (fig. 1). Predicted marsh loss increases to 89% (962 km2) by 2110 under an “upper limit of likely” sea-level rise scenario.
- Over half of the marshes in Maryland (400 km2) may currently require either no intervention or low effort hydrologic intervention, based on current elevation and vegetative cover.
- If no restoration actions are taken, about 94% (700 km2) of marshes in Maryland may require high effort interventions by 2070.
- The findings of this study demonstrate how multiple models with markedly different processes can be merged to guide marsh restoration needs.
Management Implications
Although salt marsh restoration ultimately requires a “boots-on-the-ground” approach to evaluate microtopography, small-scale hydrologic conditions, and plant diversity within a marsh before taking action, it is technically impossible to evaluate entire marsh complexes using such approaches. Therefore, a tiered, triage-like approach is often more appropriate. The models and approach described by this study represent a landscape-level assessment that enables practitioners to quickly identify marsh areas that are likely to require sediment or hydrologic interventions in the near future.
Incorporating additional information in decision making, such as distance to dredging operations or tidal restrictions, can help practitioners expand their decision matrices or create decision trees to determine whether restoration is appropriate and feasible. Efforts to incorporate the two restoration techniques considered by this study, sediment placement and hydrologic intervention, will be subject to sediment availability (ostensibly from dredging), access, and regulatory statutes. By mapping the proximity of focal marshes to dredged channels, tidal restrictions, access roads, and land ownership, practitioners can reach an important next level in a decision framework that aids landscape-level planning.