Stories From The Field

Assessing Land-Based Threats to Coral Reef Habitats in Laolao Bay, CNMI

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Issue

Land-based sources of pollution, including sediment, are one of the primary threats to coral reef health in many island environments. Research suggests that successful management of fringing coral reefs adjacent to volcanic islands may not be possible without proper land use management in the contributing watersheds. Up-to-date and accurate maps, combined with traditional ecological knowledge, are needed to effectively assess land-based threats to coral reef ecosystems and prioritize management actions.

Process

In Saipan, Commonwealth of the Northern Mariana Islands (CNMI), the Nonpoint-Source Pollution and Erosion Comparison Tool (N-SPECT) and the Habitat Priority Planner (HPP) were used to generate maps to facilitate a community-based watershed assessment process. The Laolao Bay watershed is covered by a mix of non-native forests, grasslands, plantations, and urban areas, with known sediment sources that include unpaved access roads, streambeds, and denuded upland areas. N-SPECT was used to develop graphical interpretations of these sediment source areas, as well as compare the relative changes in sediment flux under different management scenarios, including replanting trees and paving roads. HPP, along with additional techniques and tools, was used to guide the development of strategies to address coral reef ecosystem protection. Elevation data derived from lidar systems and land cover data developed from satellite imagery provided base map information for the erosion analysis of the Laolao Bay watershed. These data sources were combined for this project to match the scale of community interests and management priorities.

Impact

The watershed management planning process in Laolao Bay was greatly aided by up-to-date and accurate maps derived from modern remote-sensing technology. The fusion of traditional ecological knowledge and geospatial data created relevant information to assess current problems. The future efforts of local communities, nongovernmental organizations, and government agencies in the Pacific region to develop ecosystem-based management plans and place-based conservation projects to address the decline in coral reef ecosystem health will benefit from these map products.

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Predicted amounts of sediment originating from different sub-watersheds after revegetation.
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