Much information that would be invaluable for management of the region’s habitats is not available because of a lack of habitat monitoring. This situation is beginning to change as the importance of monitoring is more widely recognized. Since the early 1990s, habitat restoration projects have become increasingly common in the Gulf of Maine and its watershed. Most experts consider ecological monitoring to be an integral component of habitat restoration. Every habitat restoration project should include pre- and post-restoration monitoring of the project site along with nearby intact habitat areas. Pre-restoration monitoring provides baseline data about the site’s condition, which is invaluable for planning project goals, objectives, and performance indicators.
A combination of pre- and post-restoration monitoring allows accurate assessment of a project’s success. Post-restoration monitoring documents any ecological changes at the site after restoration is completed. Analysis of pre- and post-restoration data is necessary to determine progress toward meeting the project’s goals. The project may be adjusted or augmented if performance targets are not met. If the targets are met, then the monitoring data provide clear evidence of the project’s success. By monitoring similar non-impacted sites over the same timeframe, restoration practitioners can distinguish whether changes at the restored site are due to restoration activity or other causes. Monitoring data from different projects in the same habitat type can be analyzed together to evaluate the effectiveness of specific restoration techniques and to understand the condition and recovery process of the habitat.
The need for salt marsh monitoring
Salt marshes are dynamic places. They change hourly with tides, daily with weather, monthly with seasons, and over years and millennia with changes in sea level and climate. Fish enter salt marshes on flooding tides and depart on the ebb. Migratory birds stop during spring and autumn to feed in salt marshes. The salt marsh plant community shifts in its composition as the physical and ecological conditions change.
Humans are a major agent of change in salt marshes, causing immediate and long-term effects. Disturbances from human activities include the direct impacts of physical alterations such as filling, the indirect impacts of tidal restrictions and land use in the surrounding watershed, and the long-term impacts of a changing global climate. Effects of human activities can be exacerbated by natural disturbances, including severe weather events and biotic, geomorphic, and climatic processes. Collectively, these anthropogenic and natural disturbances produce a multitude of stresses on coastal ecosystems with far-reaching but poorly understood consequences, ranging from degraded habitat structure to major shifts in ecosystem function.
Basic information about the status and trends of salt marshes around the Gulf of Maine–and the causes and consequences of the changes–is vital for identifying and reversing habitat loss and degradation in the region. It is increasingly clear that incorporating long-term change analysis into coastal restoration, management, and conservation can help detect threats to critical habitats, identify sources of problems, and develop management solutions. Current national strategies for comprehensive assessments of natural resources highlight the overwhelming need for an integrated approach to ecosystem monitoring, research, and management (NSTC 1997, Integrating the Nation’s Environmental Monitoring and Research Networks and Programs; CWAP 2000, Coastal Research and Monitoring Strategy) and provide a framework for establishing and implementing monitoring of salt marsh ecosystems in the Gulf of Maine.
Development of a regional monitoring protocol
Regionally coordinated monitoring of impacted, restored, and intact reference marshes will provide an essential cornerstone for integrated salt marsh assessment and management in the Gulf of Maine. Long-term monitoring will identify changes in marsh extent and ecological condition, reveal sources of disturbance, and determine the ecosystem-level effects of human impacts. In addition, it could provide early warning of new threats, allowing proactive management that preserves marshes and reduces the need for restoration in the future.
In 1999, approximately fifty wetland scientists and resource managers from around the Gulf of Maine convened to pursue regional-scale assessment of salt marsh ecosystem characteristics, management priorities, and restoration outcomes. Under the auspices of the Global Programme of Action Coalition for the Gulf of Maine (GPAC), they developed a comprehensive protocol for standardized monitoring of impacted, restored, and natural salt marshes (Neckles and Dionne 2000). In 2004, scientists revised the protocol to make it more streamlined and cost-effective. The GPAC Protocol specifies a set of marsh indicators and data-collection techniques to allow assessment of geospatial attributes, hydrology, soils, plants, and nekton and bird use. Use of the protocol enables the thorough characterization of salt marsh sites. When the data are collected before and after a habitat restoration project, as well as in unimpacted marshes, they can be used to determine the effectiveness of restoration and the degree of natural variability in salt marshes.
Before and after: Tracking effectiveness of restoration
One major goal of monitoring is to measure outcomes of marsh restoration. Do salt marshes recover their natural structure and functions after tidal flooding is restored? How quickly, and how completely? Although people often assume that after a restoration project is implemented nature will do the rest, it is not known yet whether this is true. Consequently, ecological monitoring is an integral part of habitat restoration projects. The definition of successful restoration depends on the goals of the specific project, but usually it means that the species and processes of the restored marsh become more similar to undisturbed salt marshes. In addition, a regional database of monitoring data will allow scientists to understand the natural range of variability of salt marshes in Gulf of Maine—to define what is natural.
Monitoring a marsh for at least one year before restoration provides a baseline against which changes can be measured. Then the marsh must be monitored for several years after restoration actions have been implemented. While some aspects of the ecosystem such as plant species diversity may recover quickly, others such as soil organic content may respond more slowly. The combination of baseline and post-restoration data enables scientists to identify clearly the outcomes of restoration.
Post-restoration monitoring is also necessary for adaptive management and site maintenance. The data might indicate that additional actions are necessary, such as removing new invasive plants or digging more channels to deliver tides to distant portions of the site. Monitoring might also reveal that a restored site needs maintenance efforts such as cleaning culverts or re-planting seedlings washed away by storms.
Results: Five years of regional monitoring data
Five years after the development of the GPAC protocol, Konisky et al. (2004) compiled monitoring datasets from 36 salt marsh restoration projects—completed or planned—and conducted the first regional analysis of monitoring data and restoration practices. The monitoring data confirmed that salt marshes selected for restoration were degraded relative to reference areas. The degraded sites had lower tidal heights, reduced salinity levels, and plant communities with greater coverage of brackish plant species and less coverage of halophytes. After restoration, physical factors tended to rebound quickly. Tidal flow and salinity levels, for example, increased within one year. Biological responses were slower and less discernible. Plant communities seemed to shift toward increased cover of halophyte and lower cover of brackish species by three or more years after restoration. Fish and bird communities were indistinguishable among reference, impacted, and restored marshes. However, this finding may arise from the fact that few monitoring programs collected data on fish and birds, and their sampling methods were inconsistent.
Konisky et al. (2004) found that the 36 monitoring programs typically collected only half of the core measurements specified in the original GPAC protocol and commonly used non-standard sampling methods. Revisions to the protocol include additional acceptable sampling methods and, importantly, identification of a reduced subset of variables that should be monitored for all restoration projects. Refining and streamlining the protocols should lead to greater adherence by monitoring groups. The study by Konisky et al. provides solid support for the widely-held beliefs that (1) degraded marshes differ from reference sites in important ecological characteristics and (2) restoration practices can set degraded marshes on a trajectory toward recovery from human impacts.
Next steps: Monitoring the health of the region's salt marshesExisting monitoring programs around the Gulf of Maine provide the basis for a regional salt marsh monitoring network that is currently being developed by the Gulf of Maine Council on the Marine Environment. Planning of the framework builds on existing monitoring programs at the state (Massachusetts Office of Coastal Zone Management; New Hampshire Coastal Program), Gulf of Maine (GPAC restoration monitoring protocol), and federal (National Park Service Vital Signs Monitoring Program; NOAA National Estuarine Research Reserve biomonitoring protocol; Environment Canada/Environmental Monitoring and Assessment Network) levels, ensuring that complementary and compatible methods are used. By weaving together existing programs, a cost-effective regional monitoring network for salt marshes could be developed while providing a regional context for individual local assessments. The framework adopts the three-tiered approach of the Coastal Research and Monitoring Strategy (CWAP 2000). Indicators will be monitored at scales appropriate for identifying and characterizing problems. Remote sensing and automated data collection will be used to sample over large spatial scales, and particular sites within a region will be examined in detail using rapid-assessment methods. Index sites with high spatial and temporal resolution will allow diagnosis of cause-effect relationships.