Researcher Anna Braswell samples soil from an estuary during her dissertation research on \u2018tipping points\u2019 for wetland preservation. (Credit: Megan Fork)<\/figcaption><\/figure>\nAs the researchers took more of an estuary\u2019s surrounding geography into account, the depth, size, shape and latitude of the estuary became increasingly important predictors for determining the extent of wetlands it could support, Braswell said. The shape and orientation of the nearby coastline and the depth of near-shore waters mattered, too.\u00a0And the amount of replenishing sediment being carried into the estuary by rivers or incoming tides became a key indicator of marshes\u2019 resilience to change.<\/p>\n
\u201cThese macro-scale coastal and watershed characteristics accentuated or limited the stabilizing impacts of the local feedbacks,\u201d she said. \u201cBut they weren\u2019t really evident until we took a few steps back and viewed the estuaries from broader spatial perspectives.\u201d<\/p>\n
\u201cWhat this tells us is that salt marshes everywhere probably have tipping points,\u201d said co-author James B. Heffernan, assistant professor of ecosystem ecology and ecohydrology at the Nicholas School.<\/p>\n
\u201cKnowing what causes these tipping points to vary from location to location is an important step in identifying where we should expect marshes to be especially vulnerable to future change,\u201d he said. \u201cIt also provides a framework for understanding where wetland restoration is likely or not likely to succeed.\u201d<\/p>\n
Coastal salt marshes provide a long list of ecosystem services that benefit humans, including shoreline protection, pollution filtration, flood prevention, fishery habitat and carbon sequestration.<\/p>\n
Braswell and Heffernan published their peer-reviewed findings Jan. 31 in the journal Ecosystems<\/em>.<\/p>\nUsing existing geospatial data, they analyzed hundreds of estuaries on the U.S. Atlantic and Gulf coasts from Maine to Mexico to determine the fraction of each estuary that was occupied by wetlands and identify the factors that controlled the extent of the wetlands\u2019 spread and their resilience to change.<\/p>\n
Each site was analyzed at five different geographic scales \u2013 from macro-analyses that covered the entire estuary and its adjacent coastline and watersheds, to fine-scale analyses that zeroed in on what was happening in small, individual tributaries.<\/p>\n
\u201cIntegrating data from five different scales allowed us to see patterns and linkages that we would have missed otherwise,\u201d said Braswell, who now works as a research scientist in the Earth Lab at the University of Colorado at Boulder. \u201cThis information will be vital for future preservation and restoration efforts.\u201d<\/p>\n
Braswell and Heffernan used data from the National Wetlands Inventory and other publicly accessible sources to do their analyses. The five spatial scales they used \u2013 sub-region, basin, sub-basin, watershed and sub-watershed \u2013 correspond to standard U.S. Geological Survey hydrological units.<\/p>\n
The research was supported by grants from the National Science Foundation Geomorphology and Land-use Dynamics program (#1530233) and North Carolina Sea Grant (#R\/MG-1504).<\/p>\n
CITATION: \u201cCoastal Wetland Distributions: Delineating Domains of Macroscale Drivers and Local Feedbacks,\u201d Anna E. Braswell and James B. Heffernan. Ecosystems, Jan. 31, 2019. DOI: 10.1007\/s10021-018-0332-3<\/p>\n
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Sea-level rise, sediment starvation and other environmental woes pose increasing threats to coastal wetlands worldwide. But a massive new Duke University study, with funding from North Carolina Sea Grant, could help stem these losses by giving scientists a broader understanding of which wetlands are most at risk, and why.<\/p>\n","protected":false},"author":56,"featured_media":19003,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"ncst_custom_author":"","ncst_show_custom_author":false,"ncst_dynamicHeaderBlockName":"","ncst_dynamicHeaderData":"","ncst_content_audit_freq":"","ncst_content_audit_date":"","ncst_content_audit_display":false,"ncst_backToTopFlag":"","footnotes":""},"categories":[1391],"tags":[],"_ncst_magazine_issue":[],"class_list":["post-10782","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"displayCategory":null,"acf":[],"yoast_head":"\n
Study Yields New Clues to Predict Tipping Points for Marsh Survival - North Carolina Sea Grant<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n