Marshes on the move; A manager's guide to understanding and using model results depicting potential impacts of sea level rise on coastal wetlands

The scientific community is generally in agreement that global sea level is rising and coastal wetlands are changing as a result. Depending on local conditions, coastal wetlands may disappear under the rising seas, persist in their current locations, or migrate inland. In many places, these changes have important ramifications for the ecosystem and economy. Understanding where and how coastal environments could change in response to sea level rise, however, is a complex challenge dependent upon many factors—from interdependent ecological processes to data quality and availability. As a result, resource managers and other coastal decision-makers need appropriate tools that can help them to anticipate and prepare for the future effects of sea level rise on coastal wetlands.Many models and methods are being used for this purpose. Managers and other professionals with oversight responsibility for coastal resources are often presented with model outputs in the form of maps that illustrate projected sea level rise and potential loss or migration of coastal wetlands. These maps or visualizations may appear to provide a definitive picture, when in fact each represents a collection of assumptions, compromises, and simplifications based on the amount and quality of available data and information and on the model’s purpose. As a result, it can be challenging to interpret model results and to use the information appropriately.This document is intended for people who need to use model outputs for decision-making but who do not build models themselves. It provides a basic understanding of the parameters and uncertainties involved in modeling the future impacts of sea level rise on coastal wetlands. This is a first step toward informed use and communication of these models to support a range of sea level rise adaptation activities—from stakeholder education to habitat management to land conservation. Equipped with this conceptual understanding, managers and planners will be able to more effectively• ask the right questions of technical specialists regarding modeluse and results,• evaluate the real-world implications of model results, and• incorporate modeling results into management initiatives.