New Study Explores the Secrets of Marsh Happiness
Field data from National Estuarine Research Reserves and the U.S. Geological Survey combined to tell us surprising new things about marsh resilience. Photos courtesy of the Elkhorn Slough Reserve.
What do tidal marshes and families have in common? According to a new study published in Environmental Research Letters, they both follow the “Anna Karenina Principle.”
“We found that happy marshes are all alike, but every unhappy marsh is unhappy in its own way, just like the families in Tolstoy’s story,” says Dr. Kerstin Wasson, Research Coordinator at California’s Elkhorn Slough Reserve and lead author of the study. “We compared one marsh that was falling apart and one that was stable in eight regions to identify the features that these habitats have in common.”
The multi-partner analysis ground-truthed previous marsh resilience findings from the National Estuarine Research Reserve System (NERRS) and the U.S. Geological Survey (USGS). It confirmed that “happy,” or persistent, marshes exhibit common traits, just as happy families often have characteristics like love, health, and financial well-being in common. Vegetation in healthy marshes tends to grow in high areas relative to current water levels; they import (rather than export) sediment; and they exhibit a low ratio of unvegetated to vegetated areas.
By contrast, the new study found that “unhappy” tidal marshes deteriorate in diverse, complex ways. One finding contradicted a previous assumption: namely, that gains in marsh elevation and sediment indicate greater resilience. Marshes with these characteristics performed inconsistently, sometimes deteriorating into the muddy mess that signifies a marsh is falling apart.
“Unhappy” marshes in Rhode Island (left) and California (right) have distinctly different ways of degrading.
Studies like these support coastal communities by helping them make more informed conservation decisions based on which tidal marshes are likely to persist in place and which are likely to degrade.
“This was a great opportunity for USGS and the NERRS to integrate our newest methods of marsh monitoring,” says Neil Ganju, research oceanographer at the U.S. Geological Survey’s Woods Hole Coastal and Marine Science Center and an author on the study. “As a result we discovered that our previous approaches are stronger when combined.”
Other partners in the study included Rhode Island’s Narragansett Bay Reserve, Louisiana State University’s Department of Oceanography and Coastal Sciences, University of Michigan Water Center, Woods Hole Coastal and Marine Science Center, the Patuxent Wildlife Research Center (now the Eastern Ecological Science Center), and the Western Ecological Research Center.