title: Spatially integrative metrics reveal hidden vulnerability of microtidal salt marshes.
abstract: Salt marshes are valued for their ecosystem services, and their vulnerability is typically assessed through biotic and abiotic measurements at individual points on the landscape. However, lateral erosion can lead to rapid marsh loss as marshes build vertically. Marsh sediment budgets represent a spatially integrated measure of competing constructive and destructive forces: a sediment surplus may result in vertical growth and/or lateral expansion, while a sediment deficit may result in drowning and/or lateral contraction. Here we show that sediment budgets of eight microtidal marsh complexes consistently scale with areal unvegetated/vegetated marsh ratios (UVVR) suggesting these metrics are broadly applicable indicators of microtidal marsh vulnerability. All sites are exhibiting a sediment deficit, with half the sites having projected lifespans of less than 350 years at current rates of sea-level rise and sediment availability. These results demonstrate that open-water conversion and sediment deficits are holistic and sensitive indicators of salt marsh vulnerability.
authors.affiliation: U.S. Geological Survey, Woods Hole Coastal and Marine Science Center, 384 Woods Hole Road, Woods Hole, Massachusetts 02543, USA.
authors.forename: Neil K
authors.identifier: 0000-0002-1096-0465
authors.initials: NK
authors.lastname: Ganju
authors.affiliation: U.S. Geological Survey, Woods Hole Coastal and Marine Science Center, 384 Woods Hole Road, Woods Hole, Massachusetts 02543, USA.
authors.forename: Zafer
authors.identifier: 0000-0003-4544-4310
authors.initials: Z
authors.lastname: Defne
authors.affiliation: Virginia Institute of Marine Science, Department of Physical Sciences, 1375 Greate Road, Gloucester Point, Virginia 23062, USA.
authors.forename: Matthew L
authors.identifier: 0000-0002-0658-3038
authors.initials: ML
authors.lastname: Kirwan
authors.affiliation: Boston University, Department of Earth and Environment, 685 Commonwealth Avenue, Boston, Massachusetts 02215, USA.
authors.forename: Sergio
authors.initials: S
authors.lastname: Fagherazzi
authors.affiliation: University of Padua, Department of Civil, Environmental, and Architectural Engineering, Via 8 Febbraio, Padua 2-35122 Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: D'Alpaos
authors.affiliation: University of Padua, Department of Civil, Environmental, and Architectural Engineering, Via 8 Febbraio, Padua 2-35122 Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Carniello