Multi-scale functional mapping of tidal marsh vegetation using object-based image analysis

Nearly half of the world’s natural wetlands have been destroyed or degraded, and in recent years, there have been significant endeavors to restore wetland habitat throughout the world. Detailed mapping of restoring wetlands can offer valuable information

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K. Tuxen, M. Kelly Geospatial Imaging and Informatics Facility, College of Natural Resources, University of California-Berkeley, Berkeley, California, USA, [email protected]

KEYWORDS: tidal wetlands, San Francisco Bay-Delta, estuary, restoration, monitoring ABSTRACT: Nearly half of the world’s natural wetlands have been destroyed or degraded, and in recent years, there have been significant endeavors to restore wetland habitat throughout the world. Detailed mapping of restoring wetlands can offer valuable information about changes in vegetation and geomorphology, which can inform the restoration process and ultimately help to improve chances of successful restoration. We performed an object-based image analysis using color infrared aerial photography, which maps specific wetland functions at multiple scales. The combined results of our work highlight important trends and management implications for monitoring wetland restoration using remote sensing, and will further enable restoration ecologists to use remote sensing for tidal marsh monitoring. Restoration objectives, ecosystem function, and scale can be integrated into monitoring techniques using remote sensing for improved restoration monitoring.

1 Introduction 1.1 Tidal marsh mapping Effective tidal marsh restoration necessitates (1) the statement of specific restoration goals and objectives; (2) an understanding of how marshes will

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evolve as they are restored, which can inform the restoration process; and (3) monitoring during and after restoration (Williams and Faber 2001). Restoration goals and objectives include improvements to the habitat and ecosystem services that tidal marshes provide (Baird 2005), which include biologically rich and diverse habitat, as measured by vegetation composition, configuration, and diversity, and the provision of adequate habitat for endangered species (Philip Williams & Associates Ltd. and Faber 2004). Monitoring changes in ecosystem function after restoration can help managers understand how a marsh is evolving, which can inform the restoration process and ultimately improve changes of successful restoration. Effective monitoring should be objective, cost-effective, and as automated and non-invasive as possible (Andresen et al. 2002). Remote sensing technologies meet these requirements, and have been used to monitor wetlands around the world, allowing for the detailed mapping of restoring wetlands. The mapping of tidal marsh vegetation and habitat is a necessary and important part of wetland restoration monitoring. The heterogeneous landscape provides habitat for numerous organisms as well as the productive basis for the estuarine food web. Monitoring the pattern of vegetation communities over time can help track changes in both the pattern of a wetland landscape and the underlying biological processes to which it contributes, and thus it is important to accurately map vegetation for measurement of cover, complexity, and habitat use. There are numerous ways to map and delineate continuous