The Metzger marsh restoration: A vegetation-centric look after 27 years

Abstract

We investigated wetland vegetation before, during, and after dike construction at the Metzger Marsh project in western Lake Erie, which was designed to restore a 300-ha wetland that had been degraded following the loss of a protective barrier beach. A dike was constructed in 1995 to replace the function of the eroded barrier beach, but it contained a water-control structure to allow managed hydrologic connection to the lake. The control structure contained a fish passageway to allow movement of fish across the dike, while restricting entry of large common carp. Color-infrared aerial photos from project start in 1994 through 2010 (and 2022) were analyzed to track vegetation changes, and major vegetation types were sampled quantitatively. Drawdown of water levels in 1996 after dike construction elicited a response of mudflat species from the seed bank, as well as tree seedlings. Over half of the marsh was vegetated then and in subsequent years. The water-control structure was opened in 1998, and by 2000, invasive Phragmites australis had gained dominance. Most trees were eventually eliminated by herbicide treatment and flooding, and extent of Phragmites was reduced by management actions. Typha spp. and emergents Sagittaria latifolia and Schoenoplectus tabernaemontani became dominant by 2022. This restoration project increased habitat values for fish and wildlife; it also provided lessons for future projects on lands managed by multiple agencies with differing missions. More importantly, it showed that long-term monitoring data are critical for assessing wetland restoration projects and guiding management decisions.