Title: The causes of mangrove death on Yap, Palau, Pohnpei and Kosrae [Chapter II]
Author: Cannon, Phil G.; Falanruw, Margie; Ruegorong, Francis; MacKenzie, Rich; Friday, Katie; Ross-Davis, Amy L.; Ashiglar, Sara M.; Klopfenstein, Ned B.; Liu, Zhangfeng; Golabi, Mohammad; Iyekar, Chancy Thomas;
Source: In: Cannon, Phil. 2014. Forest pathology in Yap, Palau, Pohnpei, Kosrae, Guam and Saipan, Sept. 2013. Trip Report. Vallejo, CA: U.S. Department of Agriculture, Forest Service, Region 5, Forest Health Protection. p. 13-37.
Publication Series: Miscellaneous
The area of a massive mangrove dieback in Yinuf Mn Island, Yap, was selected as the first location to study mangrove dieback problems. Seawater and soil samples were collected from plots where the mangrove trees were dead/dying and these samples were analyzed for eight different seawater and soil floor properties. Seawater and soil properties from dead/dying/missing mangrove samples were then compared with these same eight properties for seawater and soil samples collected in nearby plots where mangrove trees appeared healthy. For these eight properties, no apparent differences were found that might help explain why mangroves had died or stayed healthy. Consequently, other possible explanations for mangrove dieback were sought, based on current stand conditions and a consideration of extenuating circumstances in the recent history of this site. At this Yinuf Mn island site, a plausible explanation for the massive mangrove dieback was that Typhoon Sudal, which had struck 9 years earlier (in April, 2004) with both strong winds and a powerful storm surge, had pushed over about 100 acres (40.5 ha) of trees on the seaward edge of this mangrove stand. These trees may also have been heavily butt rotted or impacted by an oil spill, factors which could have rendered trees more prone to toppling during Typhoon Sudal. In a separate incident, Typhoon Bopha (December, 2012), caused minor but still measurable damage to a mature mangrove stand in Babeldaob, Palau. Other potential contributors to mangrove-stand dieback in this region include girdling of trees along channels to improve boat navigation through mangroves (in Airai, Palau), the undercutting of coastlines by wave action and rising seas (in Yap, Saipan, and Kosrae), and, of course, some harvesting of mangrove trees for poles and timber (in Pohnpei and Palau). Extensive butt rot was observed in many older mangrove stands, especially in stands with high proportions of Sonneratia alba and Xylocarpus granatum.
Keywords: forest pathology, mangrove dieback, butt rot
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Cannon, Phil G.; Falanruw, Margie; Ruegorong, Francis; MacKenzie, Rich; Friday, Katie; Ross-Davis, Amy L.; Ashiglar, Sara M.; Klopfenstein, Ned B.; Liu, Zhangfeng; Golabi, Mohammad; Iyekar, Chancy Thomas. 2014. The causes of mangrove death on Yap, Palau, Pohnpei and Kosrae [Chapter II]. In: Cannon, Phil. 2014. Forest pathology in Yap, Palau, Pohnpei, Kosrae, Guam and Saipan, Sept. 2013. Trip Report. Vallejo, CA: U.S. Department of Agriculture, Forest Service, Region 5, Forest Health Protection. p. 13-37.
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