Constraints on Adjustment of Tidal Marshes to Accelerate Sea Level Rise

Tidal marshes are among the most vulnerable of the world's ecosystems. Throughout human civilization, tidal marshes have been reclaimed for agriculture and settlement, and the pace of loss has accelerated in concert with burgeoning coastal populations on all inhabited continents over the past century. To this pressure has been added the threat of accelerating sea level rise.

Potential tidal marsh loss with sea level rise threatens a range of ecosystem services valued at approximately US $27 trillion per year, extending to fisheries production, recreation, cultural heritage, coastal protection, water quality enhancement, and carbon sequestration.

Studies have shown that some marshes are gaining elevation, making them remarkably resilient to rising seas; however, results vary across locations and between contemporary and Holocene records.

In a new study recently published in Science and co-authored by the Natural Resources Research Institute (NRRI) at the University of Minnesota Duluth, researchers compared data from 97 sites on four continents and found that the relationship between sediment accretion and marsh subsidence explains the variable responses to sea-level rise.

Specifically, the research shows marshes accrete, or accumulate, more sediment, keeping up with sea-level rise up to a point, but sediment subsidence increases nonlinearly with accretion such that at higher rates of sea-level rise, marshes begin to sink. Marshes are unlikely to keep up with rising seas under current climate change projections.

"This research took several decades of data collection across the world and more than 5000 hours of fieldwork," said study co-author Katya Kovalenko, a research associate at NRRI. "The findings show the importance of limiting global warming to below 1.5°C so that tidal marshes can keep up with sea level rise."

Other research team members include Neil Saintilan from Macquarie University in Australia; Glenn Guntenspergen from the U.S. Geological Survey; Kerrylee Rogers from the University of Wollongong in Wollongong, NSW, Australia; James C. Lynch from the National Park Service; Donald R. Cahoon from the U.S. Geological Survey; Catherine E. Lovelock from the University of Queensland in Australia; Daniel A. Friess from the National University of Singapore; Erica Ashe from Rutgers University; and Nicole Khan from the University of Hong Kong.

As part of the University of Minnesota system research enterprise, the Natural Resources Research Institute at the University of Minnesota Duluth employs over 140 scientists, engineers, technicians, staff, and students in two industrial research facilities. Through collaborative partnerships, NRRI delivers the innovative tools and solutions needed to utilize and sustain Minnesota's valuable natural resources.