|U.S. Geological Survey
Open File Report 2005-1070
Moloka'i Benthic Habitat Mapping
By Susan A. Cochran-Marquez
In order to provide evidence of change in any ecosystem, one must first have a starting point, or "baseline" inventory of resources. Thematic maps providing this baseline inventory are an important tool in assessing change in coral reef ecosystems, allowing scientists to spatially document the location of corals, percentage of coral cover, and relative overall health of the system. In the last decade, scientists and managers have recognized the lack of thematic maps for coral reefs worldwide. In 1998, the President of the U.S. issued Executive Order 13089 establishing the U.S. Coral Reef Task Force (CRTF). Comprised of several Federal agencies, including the U.S. Geological Survey, the primary duty of the CRTF is mapping and monitoring of coral reefs in the U.S. and U.S. Trust Territories.
Moloka'i is one of the main eight Hawaiian Islands (Figure 1). The south shore of Moloka'i is home to the most continuous fringing coral reef in U.S. waters. Prior to 1998, the University of Hawai'i Marine Options Program undertook the only coral reef mapping effort of the south Moloka'i reef for the U.S. Army Corps of Engineers (Manoa Mapworks, 1984). Qualitative field data were collected over a two-week period using SCUBA and snorkel, and maps were plotted using 1:6K and 1:24K black and white aerial photography from 1975 as a base layer. These maps provide a useful background to the reef ecosystem, however the aerial photographs were not georectified, and thus no true quantitative measurements of scale and distribution can be made from the 1975 imagery.
Figure 1. Map of the main eight Hawaiian Islands. Some areas of known coral reef growth are shown in pink. The arrow denotes the location of the island of Moloka'i.
In 1999, in response to the mandate set forth by Executive Order 13089, The National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) implemented a program to provide digital maps of our nation's coral reefs for use in a geographic information system (GIS). The south Moloka'i reef was mapped using orthorectified aerial photography, hyperspectral remotely sensed images, and quantitative field observations (Coyne et al., 2003). The classification scheme used to produce these maps documented 9 out of a possible 23 distinct benthic habitat types on the south Moloka'i reef, and 10 out of a possible 14 morphological reef zones. However, under the restrictions of a 1 acre minimum mapping unit (MMU) at a 1:6K scale, many smaller details of the reef system were overlooked.
One of the strategic goals of the U.S. Geological Survey is to assist land-use managers by establishing the geologic framework for ecosystem structure and function. Here we provide a detailed high-resolution map and habitat characterization of a critical coral reef in Hawai'i that is of concern to resource managers and the public. The threats to the reef off the south shore of Moloka'i, including excessive sedimentation and pollution concerns, were a few of the major influences for selecting this site to develop procedures for producing these maps. Without the NOAA 1 acre MMU and 1:6K scale restrictions, the USGS is in a position to provide higher-resolution benthic habitat maps of the Moloka'i reef. These maps can be used as stand-alone or in a GIS, and provide useful information to scientists, managers and the general public.
Next section: Methods
URL of this page: http://pubs.usgs.gov/of/2005/1070/
Date created: 18 February 2005
Created by: Susan A. Cochran
Maintained by: Mike Diggles
Date last modified: 5 July 2007 (sac)
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