The status and future of tidal marshes in New Jersey faced with sea level rise

Abstract

Salt marshes are key coastal ecosystems that provide habitats for wildlife, including invertebrates, fishes, and birds. They provide ecosystem services such as protection from storm surges and waves, attenuation of flooding, sequestration of pollutants (e.g., blue carbon), and nutrient removal. They are currently under great threat from sea level rise (SLR). We collected information about trends in the horizontal extent (acreage) of New Jersey salt marshes and recent elevation changes compared with the current local rate of SLR in New Jersey, which is between 5 and 6 mm year−1. We found pervasive, although variable, rates of marsh loss that resulted from both anthropogenic disturbance as well as edge erosion and interior ponding expected from SLR. Elevation trends suggest that the current rates of SLR exceed most marsh elevation gains, although some Phragmites-dominated marshes keep pace with SLR. Four potential remedies to address current coastal trends of marsh loss were described in the context of New Jersey’s regulatory and management environment: protection of marsh inland migration pathways, altered management of Phragmites, thin layer sediment placement, and living shoreline installations. Proactive steps are necessary if coastal wetland ecosystems are to be maintained over the next few decades.

Coastal marshes provide valuable protection for coastal communities from storm-induced wave, flood, and structural loss in a changing climate

“…Thus, the marsh may be entirely inundated by the extreme SLR and lose its buffering capacity in 2100. However, recent findings of high accretion rate (> 10 mm/year) and continued growth associated with Phragmites marshes [19][20][21] suggest that Piermont marsh could keep up with SLR and retain some buffering capacity. Therefore, the potential restoration plan to restore part of Piermont marsh with Typha during 2020-2025 would not affect the marsh's buffering capacity.…”

Observations of Wave Height Amplification Behind an Oyster Castle Breakwater System in a High-Energy Environment: Gandys Beach, NJ

“…Marsh edges have sharp scarps at this site, another indicator of marsh retreat (Mariotti and Fagherazzi, 2010). Estimated shoreline retreat at Gandys Beach is about 500 feet between 1930 and 2007 (Conrad, 2015;Weis et al, 2021). Superstorm Sandy accelerated marsh edge erosion in 2012 causing significant loss of wetlands and shoreline regression in this area (Walling et al, 2017).…”

“…The site is located relatively close to the mouth of the Delaware Bay and is exposed to both wind-wave generated across the local fetch and to ocean waves propagating into and through the bay (Kukulka et al, 2017). Field observations and historic images at the Gandys Beach Preserve indicate significant shoreline erosion with reduced acreage of beach and salt marshes (Conrad, 2015;Weis et al, 2021). Marsh edges have sharp scarps at this site, another indicator of marsh retreat (Mariotti and Fagherazzi, 2010).…”

“…TNC's Gandys Beach Preserve (Gandys Beach) is located on Delaware Bay on the Southwestern coast of New Jersey and has been experiencing loss of marsh through edge erosion since measurement began in 1930 (Conrad, 2015;Weis et al, 2021). The site has large intertidal mud flats, sandy beaches, tidal creeks, and salt marshes.…”

“…Delaware Bay wetlands are thought to be more resilient to sea level rise due to their large tidal and plant growth range, sediment supply, low slope, and the availability of open space to migrate inland. At the same time, the Delaware Bay marsh edges are eroding and converting to open water with marsh loss rates of 1.1%-1.9% per decade (Weis et al, 2021). This marsh edge erosion appears to be worsening with sea level rise.…”