'Ata Island (24509)
Tonga, Oceania
Site overview
KBA status: confirmed
Global KBA criteria: D1a
Year of last assessment: 2012
National site name: 'Ata Island
Central coordinates: Latitude: -22.9667, Longitude: -176.2833
System: marine, terrestrial
Elevation (m): 0 to 355
Area of KBA (km2): 1.84069
KBA classification: Global
Legacy site: Yes
Site details
Site description: The ‘Ata IBA comprises the whole of the 2.3 sq.km. volcanic island of ‘Ata, the southernmost island of the Tongan archipelago. The island is mostly forested and is currently uninhabited and very rarely visited by people. ’Ata has some of the largest seabird colonies in Tonga especially wedge-tailed shearwaters, masked, red-footed and brown booby, and black and brown boobies. Together these are believed to number over 50,000 birds.
Rationale for qualifying as KBA: This site qualifies as a Key Biodiversity Area of international significance that meets the thresholds for at least one criterion described in the Global Standard for the Identification of KBAs.
Additional biodiversity: ‘Ata is renowned for its seabird colonies but these remain very poorly documented. Apart from the collectors of the Whitney South Sea Expedition who visited the island 13-14 July 1925, only Rinke (1991) has published ornithological observations. The apparent loss of the Pacific harrier and the exotic European starling between the visits of the WSSE and Dieter Rinke’s visit is of great interest. The island indubitably supports over 10,000 pairs of seabirds (A4iii), probably comprising 15 species. Whilst the breeding populations of the three species of booby and the two species of noddy both fulfill IBA criteria (A4ii). In addition, the Polynesian starling is a ‘central polynesian’ restricted range species (A2). Non-bird biodiversity: Rinke (1991) records the abundance of Ficus spp.in the forest on the plateau, as well as the presence of Inocarpus edulis and coconuts and pawpaw. Other species noted include Wedelia biflora thickets, Pisonia grandis, Hibiscus tiliaceus and Casuarina equisetifolia. He confirmed the presence of the Polynesian rat Rattus exulans and three skinks. Emoia cyanura, E.pheonura and Cryptoblepharus eximius.
Delineation rationale: 2012-12-17 (BL Secretariat): original polygon clipped to hi-res coastline following identification in October 2012 of new marine IBA offshore this site; site area consequently changed from 230 ha to 184 ha.
Habitats
Summary of habitats in KBA: Site description The ‘Ata IBA comprises the whole of the island of ‘Ata, a volcanic island that rises to 355 m. The island is very isolated being over 140 km SSW of Tongatapu. Rinke (1991) visited the island (5-9 April 1990) and provides the following description. The island is comprised of a ‘plateau’ bordered by two mountains in the west and two lower peaks in the east, almost completely surrounded by steep cliffs between 60-100 m high but there is a single landing place on a short sand beach on the NW coast. The plateau is heavily forested but vegetation on the cliffs is sparse. The island is uninhabited and is very rarely visited by people today, however, it was once inhabited but the population was removed to live in ‘Eua in the 1860s. Evidence of their former presence is found in lingering populations of fruit trees and crops.
| IUCN Habitat | Coverage % | Habitat detail |
|---|---|---|
| Forest | 100 |
Threats
Summary of threats to biodiversity at KBA: The remotest of Tonga’s islands and rarely if ever visited by people. Habitat destruction, poaching for food and feathers, and introduced species are the principal threats to remaining Tongan biodiversity (WWF 2001). Introduced pigs, rats and cats can have catastrophic impacts on breeding seabirds and passerines. There are no national parks in Tonga and Rinke (1986) has suggested that the greatest potential for conservation lies in the protection of uninhabited, forested, and predator-free islands such as ‘Ata, Tofua and Late that are stocked with threatened flora and fauna from inhabited islands. Paleoecology studies suggest many of the target species once occurred on these refuge islands and this approach may offer the best chance for conservation of many threatened species.
Additional information
References: Jenkins, J.A.F. 1980. Seabird records from Tonga-an account based on the literature and recent observations. Notornis 27:205-235. Prescott, N. and P. S. Folaumoetu’i (Editors). 2004. Tonga Biodiversity Stocktaking. Technical Report 1 for the National Biodiversity Strategy and Action Plan. Dept. of Environment, Nuku’alofa. Rinke, D. 1986. The status of wildlife in Tonga. Oryx 20:146-151. 1991. Birds of ‘Ata and Late, and additional notes on the avifauna of Niuafo’ou Island, Kingdom of Tonga. Notornis 38: 131-151. Stattersfield, A.J., M.J. Crosby, A.J. Long, and D.C. Wege. 1998. Endemic Bird Areas of the World: Priorities for biodiversity conservation. BirdLife Conservation Series no. 7, BirdLife International, Cambridge, UK. 846 pp. WWF 2001. www.worldwildlife.org/wildworld/profiles/terrestrial/oc/oc0114_full.html