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The Serianthes tree at Guam’s Ritidian: Leaving behind a legacy of hope
MCB Camp Blaz, Environmental Division
November 22, 2024
Christopher Kane, Naval Facilities Engineering Systems Command and 36th Civil Engineer Squadron natural resources specialist, looks up at the last adult Serianthes nelsonii tree on the island at Andersen Air Force Base, Guam, Feb. 2, 2021. Serianthes nelsonii is a large tree endemic to Guam and Rota of the Mariana Islands. Only one mature tree exists on Guam, while 121 mature trees have been identified on Rota since 1984. (Senior Airman Aubree Owens, U.S. Air Force)
MARINE CORPS BASE CAMP BLAZ - Serianthes nelsonii is a tree species found only on Guam and Rota. The CHamoru name for the Serianthes tree on Guam is Håyun lågu, meaning “wood of the north” or “foreign wood,” and in Rota, Trongkon guåfi, meaning “fire tree.” Specimens were first collected in the late 1800s and again in 1918 by Peter Nelson, from whom the species was described by Elmer D. Merrill. Although there is no remaining knowledge of traditional uses of the tree in CHamoru culture, early navigator Louis Claude de Freycinet listed Håyun lågu as a tree suitable for timber in his travel journals in the 1800s. Given the tree’s full stature and strength, it would have been suitable for shelter construction or canoe-building. In 1987, Serianthes nelsonii was listed as endangered by the United States Fish and Wildlife Service due to its rarity and threats to its survival.
(U.S. Marine Corps video by Lance Cpl. Rey Moreno Marilao)
Serianthes trees occur in limestone forest habitats and also on clay soils of southern Guam. Belonging to the Fabaceae family, Serianthes is a large canopy tree that can reach heights of over 90 feet. The current population is estimated at 48 mature wild trees and 74 outplanted trees on Rota, and 383 seedlings on Guam. The single mature tree on Guam, located at Ritidian Point (also known as Litekyan in CHamoru), succumbed to severe damage sustained during Typhoon Mawar in May of 2023. By September of 2024, there was no living tissue observed on the decomposing remains of the tree. Leading up to the typhoon, the Ritidian tree was already in very poor condition due to a split trunk that led to heart rot (a type of fungal infection) that worsened over two decades and had insect infestations.
Aside from typhoons, major threats to Serianthes trees include introduced insect predators and herbivores. Sucking insects can defoliate young trees within 24 hours. Deer eat the seedlings, and pigs can uproot or disturb the seedlings, causing them to dry up and die. Loss of habitat through urban growth and habitat degradation by ungulates (pigs and deer), fire, forest fragmentation, and human activities all contribute risks to the Serianthes tree’s long-term viability.
Since the 1990s, management projects have been carried out through the collaboration of the Commonwealth of the Northern Mariana Islands’ Department of Lands and Natural Resources, the Department of the Navy, the Government of Guam Department of Agriculture, the University of Guam, and the USFWS. These efforts include barriers to keep ungulates away, maintenance/monitoring of the Ritidian mature tree and its surrounding seedlings, seed collection and storage, development of propagation techniques, and the outplanting and maintenance of propagated seedlings.
More recent management efforts include collecting 176 seedlings at the Ritidian site, stabilizing these collected plants at UOG’s Guam Plant Extinction Prevention Program nursery, followed by the outplanting of healthy seedlings at the Forest Enhancement Site on Marine Corps Base Camp Blaz. To preserve the genetics of the last mature tree on Guam, Joint Region Marianas will continue maintenance of young trees that originated from the Ritidian mother tree: 99 saplings growing at the MCB Camp Blaz Mason Live Fire Training Range Complex, eight saplings growing at Andersen Air Force Base, and 100 saplings outplanted in the MCB Camp Blaz Caiguat Forest Enhancement Site. Through the collection and specialized storage of seeds since 2014, the future propagation of the 4,007 seeds from the Ritidian tree lineage will be utilized to continue the outplanting of trees on Guam in ungulate-free fenced areas.
While not all of the young plants are guaranteed to reach maturity, continued federal and local investment, advances in propagation techniques, and strong stakeholder support offer hope for the species’ recovery on lands under both civilian and military management. Thanks to the efforts of Guam’s conservation managers, plant specialists, and community members, there is hope that Serianthes trees will thrive once again across the island’s forests—standing tall as living symbols of resilience, rooted in the enduring memory of the fallen but unconquered mother tree at Ritidian.