Endangered Species in the Pacific Islands
Recovery Plan for the Serianthes nelsonii
Serianthes nelsonii is one of the largest native trees in the Mariana Islands and is found no where else in the world. During a survey on Rota, trees were found with heights of up to 118 feet (36 meters) and trunks of up to 6 feet (1.83 meters) in diameter. There are two known populations of this endangered tree on Rota and Guam. As of 2010, there is 1 tree on Guam, above Ritidian Poin,t and 60-80 trees on Rota.
S. nelsonii has two Chamorro (local) names. In Rota it is referred to as tronkon guafi, which means "fire tree." In Guam, it is called hayun lagu, which means "foreign wood" or "wood of the north."
This tree was federally listed as endangered on February 18, 1987; and is listed as endangered on the Red Data List for Plants, the Commonwealth of the Northern Mariana Islands Endangered Species List, and the Guam Endangered Species List.
Serianthes nelsonii - Photo credit
Habitat & Distribution:
All surviving Serianthes nelsonii trees on Rota and Guam occur on limestone-derived soils. Most of the trees on Rota grow on or near steep hillsides and cliffs at elevations of 490-1,380 feet (150-420 meters) on the western side of the island. Trees on Guam were known to grow at elevations of 400-575 feet (120-175 meters).
The current population estimate for both islands is 60-80 trees with little successful regeneration occurring. Many trees were damaged or killed by typhoons in 2003 and 2004. It is unlikely that significant numbers of additional trees remain to be discovered on either island. However, continued surveys on Rota and Guam may find a few more individual trees or subpopulations.
There is no historical data of the status of distribution on this endangered tree on Rota, and data on the Guam population is poor. It is believed, however, that S. nelsonii was rare at the time of its discovery in the late 1800s.
A number of factors are involved in the decline of Serianthes nelsonii, however, these causes are poorly studied. Based on initial investigations and field observations, the primary threat on both Rota and Guam is a lack of regeneration probably caused by the browsing of seedlings by deer and by predation on seeds by insects.Other threats to S. nelsonii include browsing by pigs, cattle, and deer; typhoon damage; habitat loss; inbreeding; wild fires; and insect infestations.
Cultivation of small numbers of S. nelsonii seedlings has been attempted by the Commonwealth of the Northern Mariana Islands Department of Land and Natural Resources, Guam Division of Forestry and Soil Resources, the University of Guam College of Agriculture and Life Sciences, and the Waimea Arboretum. Success was generally poor, with most seedlings succumbing within a few months to one or two years. The primary cause of mortality was mealybugs on Guam and black twig borers in Hawai`i. However, the Guam National Wildlife Refuge has successfully outplanted a handful of individuals.
Habitat protection and management is necessary for the recovery of this tree. Augmentation of existing populations and outplanting may also be necessary for its recovery.