could be lost without any formal record. Seagrass dieback has been recorded in nearby waters of the Torres Strait (Long et al. 1995) and is considered of sufficient concern to be a major focus of the Australian Cooperative Research Centre for the Torres Strait.
A survey of 3,000 kilometers of the northern Australia coastline has just been completed (Roelofs, Coles, and Smit 2005) using a helicopter as a cost-effective way of estimating seagrass area, abundance, and species over a large and remote area. Similar methods could provide an up-to-date map of Papuan seagrass with a precision suitable for quantifying future gains and losses.
What is recorded for Papua suggests distribution patterns of seagrasses are comparable to that found in other parts of the Indonesian archipelago, Papua New Guinea, the western Pacific islands, the Philippines, and northern Australia (Coles and Lee Long 1999; Coles et al. 2003; Green and Short 2003). Subsets of the same suite of tropical species occur and the zonation patterns described can be found in similar locations in all the adjoining countries and islands. The threats to sea-grasses are also relatively generic to the region, with local land clearing and resulting sediment run off, mine tailings, inappropriate fishing methods, and nutrients from sewage likely to be the major problems at a local scale. Population and development levels in Papua are generally low at the present time, but as they increase, transport infrastructure development issues will affect coastal seagrasses as they have elsewhere.
Climate change is likely to be the major variable in the medium to long term. Climate change is predicted to raise sea level and seawater temperatures, and to increase carbon dioxide concentrations in seawater. Rising sea levels could increase the distribution of seagrass because more inland areas will be covered by seawater. However, the sediment erosion that is likely to be associated with sea level rise could destabilize the marine environment and cause seagrass losses. Increasing concentrations of carbon dioxide in seawater could increase the area of seagrass because seagrasses will have more carbon available for growth and could increase photosynthetic rates. Increased seawater temperatures might raise the photosynthetic rate of seagrasses. However, in some places, seagrasses are close to their thermal limit and rising temperatures could cause ‘‘burning’’ and tissue death.
To provide an early warning of change, long-term monitoring and community engagement programs have been established as part of the Global Seagrass Monitoring Network (www.SeagrassNet.org, Short et al. 2002; www.seagrasswatch.org, McKenzie, Campbell, and Roder 2001). Establishing a network of monitoring sites in Papua would provide valuable information on temporal trends in the health status of seagrass meadows in this region and provide a tool for decision makers in adopting protective measures. Monitoring encourages local communities to become involved in seagrass management and protection. For example, one of the recommendations for conservation action after the 2002 ecological Rapid Assessment in Raja Ampat was the establishment of monitoring programs, including seagrass monitoring (Donnelly, Neville, and Mous 2003). Working with both scientists and local communities, this approach is designed to draw attention to the many local anthropogenic impacts on seagrass meadows that degrade coastal ecosystems and decrease their yield of natural resources.
Acknowledgments
We thank the participants of the University of New Hampshire and the David and Lucile Packer Foundation–funded Seagrass 3M Workshop: Mapping, Monitoring and Management of Seagrass Resources in the Indo-Pacific, held at The Nature Conservancy, Southeast Asia Center for Marine Protected Areas, Sanur, Bali, 9th to 12th May 2005, for their assistance. We also thank Yayu La Nafie and the members of the Indonesian Seagrass Association ([email protected]) for their encouragement and support.
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