Do predators have a role to play in wetland restoration? An experimental study in New England coastal salt marshes

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Alexandria C. Moore and Oswald Schmitz

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Traditional approaches to wetland restoration often emphasize reestablishing native vegetation and engineering the correct hydrology along with other environmental features, thereby setting the stage for nature to do the rest. With this bottom-up focus, the biotic diversity of wetlands and their related trophic interactions are treated as measures of restoration success rather than factors that may influence it. However, recent studies have shown that the loss of predators in coastal salt marshes can lead to significant reduction of wetland extent due to overgrazing by herbivores. Such studies indicate that consumers may play a much larger role in the maintenance of wetland ecosystems than was previously thought. Therefore, the objective of this study was to evaluate whether altering top-down control by manipulating the presence of predators can lead to measurable changes in salt marsh ecosystem properties. Between May and August of 2015 and 2016, we established exclosure and enclosure cages within three coastal wetlands and manipulated the presence of green crab predators to assess how consumers affect changes in ecosystem functions. Predator presence was associated with changes in aboveground biomass and the rate of soil nitrogen absorption at one study site, while changes in other ecosystem processes were largely driven by bottom-up factors. These results challenge the recent consensus that consumers have strong effects, instead indicating that predator effects may instead be context-dependent and therefore may not be required for improved restoration outcomes.

Resource Type:
Conference Presentation, SER2021

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