Tidal marsh restoration: trends in vegetation change using a geographical information system (GIS)

Published source details Barrett N.E. & Niering W.A. (1993) Tidal marsh restoration: trends in vegetation change using a geographical information system (GIS). Restoration Ecology, 1, 18-28.
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This study is summarised as evidence for the following.

	Action	Category
	Facilitate tidal exchange to restore degraded brackish/salt marshes Action Link

Facilitate tidal exchange to restore degraded brackish/salt marshes

A before-and-after study in 1946–1988 of a coastal salt marsh in Connecticut, USA (Barrett & Niering 1993) reported that after installing culverts across a dyke to restore tidal exchange, coverage of salt marsh plant communities increased and coverage of fresh/brackish plant communities decreased. Statistical significance was not assessed. Salt marsh plant communities covered 88% of the site in 1946 (before tidal exchange was blocked), 4% of the site in 1976 (after 30 years without tidal exchange) and then 63% of the site in 1988 (after 10 years with restored tidal exchange). Twenty-eight percent of the site was covered by the same salt marsh community type in 1988 as it was in 1946. Vegetation dominated by smooth cordgrass Spartina alterniflora was more abundant in 1988 (51% coverage) than in 1946 (40% coverage). Mixed saltgrass Distichlis spicata and saltmeadow cordgrass Spartina patens was less abundant in 1988 (<1% coverage) than in 1946 (37% coverage). Stands dominated by narrowleaf cattail Typha angustifolia and common reed Phragmites australis (36% coverage in total) persisted in 1988 after restoration of tidal exchange (vs 80% coverage in 1976 and 0% coverage in 1946). Methods: The study compared three vegetation maps: before, during and after tidal restriction. A dyke built across the mouth of the marsh in 1946 stopped tidal exchange. Culverts built in 1978 and 1982 restored it.

(Summarised by: Nigel Taylor)