Buying Time With Runnels: A Climate Adaptation Tool for Salt Marshes
A prominent form of salt marsh loss is interior conversion to open water, which occurs when water becomes stranded on the surface of a marsh, stresses vegetation, and leads to plant death. Surface water is increasing on marshes due to interactions between sea level rise and historic changes made to marshes by people. These areas can expand rapidly, converting salt marsh meadows into unvegetated, shallow water areas.
Runnels are shallow channels originally developed in Australia to control mosquitoes by draining standing water, but they have recently been used to restore marsh vegetation in the United States. Runnels work by draining shallow water from the marsh surface and restoring tidal hydrology, allowing vegetation to regrow.
Documentation on runnel efficacy is not widely available; yet over the past 10 years dozens of coastal adaptation projects in the Northeast have incorporated runnels. In this new paper published in Estuaries and Coasts, a team of scientists and resource managers led by Alice Besterman and Linda Deegan synthesized existing knowledge on runnels used in coastal climate adaptation projects. The team gathered and summarized information from a workshop, stakeholder meetings, literature review, and a runnel case study in which vegetation was restored at a degraded marsh.
The case study and other projects suggest runnels can be effective at mitigating sea level rise and restoring vegetation. However, key questions remain on long-term runnel efficacy in marshes differing in environmental characteristics and management history. The authors recommend future research directions that quantify the conditions under which runnels will be most effective and identify best practices to avoid unintended consequences, while also maximizing ecological benefits and services. This information will benefit managers designing future coastal adaptation projects. This paper concludes that runnels are a promising technique that may “buy time” for salt marshes to respond to management action or adapt to sea level rise when used as part of a holistic climate plan including other management interventions.
