Endemic to Vanuatu where, although it is not directly threatened, the population is small with perhaps less than 1000 mature individuals.
Description
Taxonomic notes
This species has previously been misidentified as Agathis macrophylla, which occurs on the three southernmost islands of Vanuatu, not on Espiritu Santo.
Distribution
Endemic in Vanuatu on the west coast of Espiritu Santo (Cumberland Peninsula and Mt. Tabwémasana ('Santo Peak')) It has an estimated extent of occurrence (EOO) of about 104km² and an area of occupancy (AOO) estimated to be about 12km². It occurs at altitudes between 450 and 760m above sea-level. The occurrence of large trees of Agathis in the interior mountains of the island of Espiritu Santo in Vanuatu has long been known, both to native islanders and at least since 1963 to visitors. In April 1987 G. Bourdy collected numerous herbarium specimens from 'Santo Peak' (Mt. Tabwémasana), where the trees were observed to be abundant, with several very large individuals seen. This was thought to be the only station of the species, but an earlier collection (specimen at K) dating from February 1979 was made at the nothern end of the mountain range on the Cumberland Peninsula on the "top western slopes" (ca. 600m above sea-level.) and so there are at least two sub-populations of this species.
Currently this species is known from four localites/subpopulations along the west coast of Espiritu Santo. Stands are localized. Population trends are uncertain as its distribution (and population size) are incompletely known. To date logging has been limited in extent and duration and it is uncertain if this has caused a decline
Habitat and Ecology
Agathis silbae occurs as an emergent large tree in tropical lower montane rainforest on the wetter, western and northwestern slopes of the central mountain range. It has been recorded to occur with Calophyllum neo-ebudicum, Cryptocaya turbinata, Dysoxylum sp., Myristica fatua, Podocarpus sp. and Syzygium spp. (Baldwin et al., 1993; Siwatibau et al., 1998). Average annual rainfall is estimated to be about 4,500 mm.
Human Uses
This species appears to be planted in or near villages on the west coast of the island. Traditionally, the resin has been used for lighting and to caulk canoes, and its soot for tattoos; the bark for medicines; and the root tips for "fattening babies" (Siwatibau et al., 1998; Wheatley, 1992). Some trees are cultivated in coastal villages. Santo kauri was commercially logged by a local operator between 1995 and 1997, and the wood is much in demand. Logging is the principal threat to the species, and Corrigan et al. (2009), who work with the Vanuatu Department of Forests, present detailed recommendations for its management.
Conservation Status
Global status and rationale
Near Threatened
Agathis silbae is currently only known from a very limited area on Espiritu Santo. The extent of occurrence (estimated at 2,200 km²), the area of occupancy (estimated to be more than 10 km² but less than 100 km² and the number of locations (4) are within the thresholds for Endangered under the B criteria. However there is still insufficient evidence of recent or ongoing decline to fully meet the requirements for such an assessment. The recent surveys also indicate that listing as Vulnerable under the D1 or D2 criteria would be inappropriate. Due to its limited distribution, logging is a potential threat unless carefully managed. Unrestricted exploitation would warrant an immediate listing as Endangered. In the meantime, an assessment of Near Threatened is probably the best indicator of its conservation status (it almost qualifies for a threatened listing under criterion B1ab(iii)+2ab(iii)).
Global threats
The known stands are located in relatively inaccessible areas that are unsuited to agriculture. A limited amount of logging occurred from 1995-1997 in one area. Land disputes and benefit sharing disputes led to a suspension of logging activities. Despite this there is still considerable interest in exploiting this species.
Conservation Actions
There are no protected areas established in the mountains of Espiritu Santo as all land is locally owned. Decisions related to resource use and extraction requite the approval of the landowner. One of the constraints on sustainable use of the kauri forests is the lack of knowledge concerning their distribution and ecology. Further field work is essential.
References and further reading
Baldwin, P., Hidson, J., Siebur, J. & Pedro, F. (1993). Forest resources of Vanuatu. A summary of the forest resources of Vanuatu derived from the National Forest Inventory. Brisbane, Queensland Department of Primary Industries: 196pp.
Beveridge, A.E. (1975). Kauri forests in the New Hebrides. Philosophical Transactions of the Royal Society of London (B.) 272: 369-383.
Corrigan, H., S. Naupa, R. Likiafu, J. Tungon, C. Sam, L. Kalamor, L. Viji, L. Mele, and L. Thomson. ( 2009). A strategy for investigating, conserving, and managing the genetic resources of Santo kauri (Agathis silbae). Pp. 383-390 In: Bieleski, R.L. & Wilcox, M.D. (eds.), Araucariaceae: Proceedings of the 2002 Araucariaceae Symposium, Araucaria-Agathis-Wollemia. Dunedin, New Zealand: International Dendrology Society.
de Laubenfels, D.J. and Silba, J. (1987). The Agathis of Espiritu Santo (Araucariaceae), New Hebrides. Phytologia 61: 448-452.
Siwatibau S, Bani C, & Kaloptap J. (1998). SPRIG Rapid Rural Appraisal Survey of selected tree species in Vanuatu. Report by Island Consulting to CSIRO Division of Forestry/SPRIG Project.
Thomson, L.A.J. (2006). Agathis macrophylla (Pacific kauri). Species Profiles for Pacific Island Agroforestry. Available at: Http://www.Traditionaltree.Org/ 6 August 2007. (Accessed: 27 July 2010).
Wheatley, J.J. (1992). A guide to the Common Trees of Vanuatu. Department of Forestry. Republic of Vanuatu
