One prominent form of salt marsh loss occurring today throughout Buzzards Bay 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. Increasing surface water on marshes is occurring 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 where the marsh slowly dies ‘from the inside out’.
A management technique called Runnels may provide one answer to this challenge. Runnels are shallow channels originally developed in Australia to control mosquitoes by draining standing water, but recently used to restore marsh vegetation in the USA. 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 northeastern USA have incorporated runnels.
Last month, BBC’s Post-Doctoral Researcher Alice Besterman and VP of Bay Science Rachel Jakuba led a research collaboration which includes the Woodwell Climate Research Center, Buzzards Bay National Estuary Program, Bristol County Mosquito Control District, and Rhode Island’s Save the Bay in publishing their findings in the journal Estuaries and Coasts. The paper synthesizes existing knowledge on runnels used in coastal climate adaptation projects. The team gathered and summarized information from a workshop, stakeholder meetings, literature review, and and a case study where vegetation was restored. The case study and other projects suggest runnels can be effective at mitigating sea level rise and restoring vegetation.
The paper concludes that runnels are a promising technique that when used as a part of holistic climate planning including other management interventions, runnels may “buy time” for salt marshes to respond to other management actions, or adapt to sea level rise.
Check out the full paper in Estuaries and Coasts