Factors influencing the persistence of created tidal marshes are the subject of a new DUC-led study
Fraser River Estuary
Daniel Hennigar, DUC conservation technician and co-author of the report
Surrey, BC, March 31, 2022 (GLOBE NEWSWIRE) — Over the past 40 years, more than 100 tidal marsh restoration projects have been constructed in the Fraser River estuary to mitigate habitat loss due to human activities and to maintain the ecological integrity of the area. Other projects continue to be proposed. However, reports have shown that the success of these restoration projects varies.
A new in-depth report from Ducks Unlimited Canada (DUC) – the most comprehensive analysis of tidal marsh projects in the Fraser River estuary to date – sheds light on the factors that make some projects more successful than others. ‘others.
Beginning in the spring of 2021, local wetland plant ecologist Daniel Stewart and DUC conservation technicians undertook a study to assess 27 marsh restoration projects and nine natural reference marshes in the Fraser River estuary and combined these results with similar data from a 2016 report. These data were used to model the potential causes of marsh retreat, the dominance of native plant species and the species richness of these sites. Among their findings detailed in their report, titled Factors Influencing the Persistence of Created Tidal Marshes in the Fraser River Estuary:
Marsh retreat was observed in 40 of the 78 created marshes studied (51%), resulting in an estimated loss of 23,553 square meters, or 9.3% of the total area of created marshes sampled.
There is no single factor that can determine the loss of the swamp recession. Emphasis is placed on site design, boat wakes and the impact of grazing by feeding Canada geese; however, altered sedimentary processes, sea level rise, shading, and monitoring efficiency are all possible causes and warrant further investigation.
Although protective infrastructure, particularly debris fences and offshore structures such as marina docks and log storage booms may be mitigating the downturn, sites built in the North Arm of the Estuary Fraser River experienced an average of 12% additional recession, and the recession increased at an average rate of 1%. cent per kilometer upstream between sites.
The dominance of native vegetation declined at an average rate of 1% per km upstream in created marshes. This reflects an eastward increase in the dominance of non-native plants, including invasive species such as yellow iris, purple loosestrife, and reed canarygrass.
Contrary to this trend, the invasive cattail dominates several sites in the outer estuary. When present, cattails often outgrow native vegetation.
DUC conservation program specialist and co-author of the report, Eric Balke, notes that “there are several sites that date back to the early 1990s that show no signs of recession and are free of invasive species. This suggests that projects can be successful and somewhat resilient for decades if a site is properly designed, implemented and monitored.
“It is important that we learn from the past so that future restoration projects are executed in a way that acceptably compensates for habitat loss,” said Sarah Nathan, DUC’s Provincial Operations Manager for British Columbia.
Balke says the report suggests managers should plan for the inherent risks and trade-offs that come with designing a project’s location. “For example, sites built further upstream may be more vulnerable to recession and the dominance of non-native plants. Closed scallop designs may be more vulnerable to cattail invasions. And low-lying sites may be more resistant to species invasions but may be more vulnerable to recession.
Nathan notes that the report’s findings will strengthen DUC’s ongoing efforts to apply its conservation knowledge to find solutions that will protect the vital habitats of this essential estuarine ecosystem.
“Working with our partners, we have focused on restoring key wetland habitats, such as the lost tidal marsh surrounding the Fraser River, with the goal of replenishing salmon stocks and improving habitat for a wide variety of marine life and waterfowl,” says Nathan. “We believe the Fraser River Estuary’s ability to thrive is aided by our commitment to on-the-ground conservation.
Factors Affecting the Persistence of Coastal Marshes Created in the Fraser River Estuary report marks the start of a longer investment by DUC over the next two years to restore coastal marshes throughout the estuary to support sequestration carbon and restore salmon habitat. CIC will use the findings of the report to inform restoration work and identify some unsuccessful offset sites to restore.
The study was funded by the BC Wildlife Federation Wetlands Workforce Project and supported by the Provincial Healthy Watersheds Initiative led by the Real Estate Foundation of BC and Watersheds BC with financial support from the Province of British Columbia as part of its $10 billion COVID-19 response. .
To request a copy of the report and learn more about DUC’s conservation work in the Fraser River estuary, visit ducks.ca/fraser-river-estuary
Fraser River Estuary – importance and threats:
Within Western Canada’s largest urban metropolis lies a vital ecosystem known as the Fraser River Estuary: an extensive network of channels, marshes, eelgrass meadows and mudflats and mud flats.
The estuary is an important wintering area for waterfowl, a site of hemispheric importance for migrating shorebirds, and home to hundreds of millions of migrating juvenile salmon smolts that depend on these brackish ecosystems to prepare their bodies for life in the ocean.
Urban and industrial expansion continues to reduce the estuary’s ability to sustain its diversity of life. Pollution, widespread dredging and diking, urban sprawl, climate change, and many current and future large-scale industrial developments threaten the ability of the estuary to support the biodiversity that depends on it.
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Ducks Unlimited Canada (DUC) is the leader in wetland conservation. As a registered charity, DUC partners with government, industry, not-for-profits, Indigenous peoples and landowners to conserve wetlands critical to waterfowl, wildlife and wildlife. ‘environment. To learn more about CIC’s innovative environmental solutions and services, visit www.ducks.ca
CONTACT: Ashley Lewis Ducks Unlimited Canada [email protected]