Abstract

Tidal marsh restoration and creation is growing in popularity due to the many and diverse sets of services these important ecosystems provide. However, it is unclear what conditions within constructed settings will lead to the successful establishment of tidal marsh. Here we provide documentation for widespread and rapid development of tidal freshwater wetlands for a major urban estuary as an unintended result of early industrial development. Anthropogenic backwater areas established behind railroad berms, jetties, and dredge spoil islands resulted in the rapid accumulation of clastic material and the subsequent initiation of emergent marshes. In one case, historical aerial photos document this transition occurring in less than 18 years, offering a timeframe for marsh development. Accretion rates for anthropogenic tidal marshes and mudflats average 0.8-1.1 and 0.6-0.7 cm year−1, respectively, equivalent to two to three times the rate of relative sea level rise as well as the observed accretion rate at a 6000+ year-old reference marsh in the study area. Paired historical and geospatial analysis revealed that more than half of all the tidal wetlands on the Hudson River were likely triggered by anthropogenic development since the onset of the industrial era, including two-thirds of the emergent cattail marsh. These inadvertently constructed tidal wetlands currently trap roughly 6% of the Hudson River's sediment load. Results indicate that when sediment is readily available, freshwater tidal wetlands can develop relatively rapidly in sheltered settings. The study sites serve as useful examples to help guide future tidal marsh creation and restoration efforts.

About this article

This article, published in Earth Surface Processes and Landforms in 2020, describes findings from a research project that was conducted in collaboration with the Hudson River National Estuarine Research Reserve. It presents sediment accumulation rates in marshes along the Hudson and reveals the rapid growth of marshes associated with anthropogenic structures. To learn more, read this press release or this research summary fact sheet.

Data from sediment cores that were collected in association with this article are archived at https://doi.org/10.7275/dh3v-0x33. A pre-print of this article is available at EarthAirXiv.