Protected Areas and World Heritage Programme

NAME Wetlands of Aunu'u

LOCATION 14^o17'30"S, 170^o33'E; on the island of Aunu'u, 1.6 km off the southeastern tip of Tutuila.

AREA 45 ha.

ALTITUDE Sea level to 6 m.

OVERVIEW A freshwater marsh in a dormant volcanic crater; a unique "mud" lake with fringing mangrove forest; a large area of taro fields in a former freshwater marsh; and a small area of mixed mangrove forest. These wetlands include the largest and least disturbed freshwater marsh in American Samoa and one of only two stands of the "puzzlenut" tree Xylocarpus moluccensis.

PHYSICAL FEATURES Aunu'u Island is a small volcanic island (2.6 sq.km) with a 61 metre cone. There are four significant wetlands on the island a large freshwater marsh (Faimulivai Marsh) in Aunu'u Crater; an area of taro fields in a former marsh near Aunu'u village; a mud lake (Pala Lake) with fringing mangroves near the north end of the island; and a small patch of mixed mangrove forest on poor rocky soils on the south coast of the island. With an area of 14.9 ha, Faimulivai Marsh is the largest freshwater wetland in American Samoa. The wetland is about six metres above sea level, and consists of several open-water ponds surrounded by extensive marshes. It is drained by a stream that flows out of the eastern end of the crater. Faimulivai Marsh is somewhat anomalous in that it was formed not by sedimentation in a lagoon but from poor drainage in a low-lying crater. The Aunu'u taro fields, covering about 11.0 ha, are situated in a large depression between the western slope of the crater and the village of Aunu'u. This area was formerly an extensive coastal marsh, but little of the original marsh vegetation remains. Pala Lake is an area of "quicksand" inland from the north coast of the island. It is slightly above sea level, and consists of reddish-brown mud covering an area of about 1.2 ha. The mud is totally devoid of vegetation, and is completely surrounded by a narrow strip of tall mangrove trees. The mangrove forest extends in a northwesterly direction, and becomes mixed with trees of the coastal and lowland forests. The whole wetland covers an area of about 18.1 ha.

ECOLOGICAL FEATURES Faimulivai Marsh has two main zones of vegetation. The western half is composed almost entirely of two species, Eleocharis dulcis and Cyclosorus interruptus, which form a dense vegetation 1.0-1.5 m high. On the eastern side and around the margins of the central pond, the vegetation is dominated by large clumps of Acrostichum aureum up to 3 m in height. Along the edges of the marsh, there is a dense thicket of Hibiscus tiliaceus trees which separates the marsh from the coconut groves and secondary forest on the inside slopes of the crater. Ludwigia octovalvis and Rhynchospora corymbosa appear in disturbed portions of the marsh. The marshy depression near Aunu'u village is largely under cultivation for taro (Colocasia esculenta). Some Acrostichum, Cyclosorus, Eleocharis, Rhynchospora and Ludwigia persist, along with a number of weeds that have invaded the area, such as Canna indica, Alternanthera sessilis, Paspalum conjugatum, Mikania micrantha and Commelina diffusa. The fringe of mangrove around Pala Lake consists of tall Bruguiera gymnorrhiza trees (up to 15 m high) with small Rhizophora mangle trees around the edge. The mixed mangrove forest on the south coast consists of B. gymnorrhiza mixed with a few Xylocarpus moluccensis trees and several species of the littoral forest. The surrounding open forests contain typical littoral species such as Hernandia sonora, Pisonia grandis and Barringtonia asiatica, as well as a coastal ridge species, Planchonella costata.

LAND TENURE No information.

CONSERVATION MEASURES TAKEN Part of Aunu'u Island (123 ha), including Faimulivai Marsh, was designated a National Natural Landmark in 1972 (Amerson et al., 1982; IUCN, 1991).

CONSERVATION MEASURES PROPOSED Whistler (1976) considered the marsh inside Aunu'u Crater to be a unique type of wetland vegetation, and recommended that any proposal for nature reserves in American Samoa should give this site priority. He also identified the mud lake as a unique type of wetland worthy of special protection. Dahl (1980), Amerson et al. (1982) and Engbring and Ramsey (1989) recommended the establishment of a reserve at Faimulivai Marsh, and the conservation of this wetland was identified as a national priority in the SPREP/IUCN Action Strategy for Nature Conservation in the South Pacific (SPREP/IUCN, 1989). Faimulivai Marsh (14.9 ha) is currently being considered for designation as a Special Management Area under the Coastal Management Act of 1990.

LAND USE There is one small village on the island. The marshy depression near Aunu'u village is intensively cultivated for taro. These taro patches are probably the best in Samoa, with extensive canals and a paved walkway crossing the area (Whistler, 1976).

DISTURBANCES AND THREATS The mixed mangrove forest on the south coast of the island has been degraded by severe cutting for firewood by local villagers. The disappearance of the Pacific Black Duck has been attributed to hunting, rat predation and human disturbance in the marshes (Amerson et al., 1982). Purple Swamphens are both hunted for food and killed as pests on crops.

HYDROLOGICAL AND BIOPHYSICAL VALUES No information.

SOCIAL AND CULTURAL VALUES No information.

NOTEWORTHY FAUNA The Pacific Black Duck (Anas superciliosa) formerly occurred as a breeding species in the wetlands. Seven were observed in Faimulivai Marsh in November 1976 (Amerson et al., 1982), but there do not appear to have been any records on the island since about 1980, and the species may now be extinct as a breeding bird in American Samoa (Engbring & Ramsey, 1989). The Purple Swamphen (Porphyrio porphyrio) remains fairly common despite some persecution. Engbring and Ramsey (1989) observed seven at one time in Faimulivai Marsh in 1985. These birds belong to the subspecies P. p. samoensis, endemic to the high islands of American Samoa and Western Samoa. Other waterfowl recorded on Aunu'u include Pacific Reef Heron (Egretta sacra), Banded Rail (Rallus philippensis) and three species of migratory shorebirds Pacific Golden Plover (Pluvialis fulva), Wandering Tattler (Heteroscelus incanus) and Ruddy Turnstone (Arenaria interpres) (Amerson et al., 1982; Engbring & Ramsey, 1989). Collared Kingfishers (Halcyon chloris) and Wattled Honeyeaters (Foulehaio carunculata) frequently forage in the mangrove areas.

The Polynesian Rat (Rattus exulans) and Brown Rat (R. rattus) are common on the island and both occur in the freshwater marshes. Other mammals include the flying fox Pteropus samoensis and the Sheath-tailed Bat (Emballonura semicaudata), the latter frequently foraging in the mangroves.

The Marine Toad (Bufo marinus) was introduced in 1953 by the U.S. Department of Agriculture as a general control on insect pests, and is now common in the wetlands (Amerson et al., 1982).

NOTEWORTHY FLORA Faimulivai Marsh is the only site in American Samoa with an intact Eleocharis dulcis marsh community. The mangroves of Aunu'u are at the extreme eastern limit of natural mangrove distribution in the Central Pacific. The Xylocarpus moluccensis trees at the south end of the island comprise one of only two stands of this rare species in American Samoa.

SCIENTIFIC RESEARCH AND FACILITIES The wetland flora has been surveyed by Whistler (1976) and Cole et al. (1988). The wildlife has been investigated by Amerson et al. (1982), and detailed surveys of the bird fauna have been conducted by Engbring and Ramsey (1989).

MANAGEMENT AUTHORITY AND JURISDICTION No information.

REFERENCES Amerson et al. (1982); Cole et al. (1988); Dahl (1980); Engbring & Ramsey (1989); IUCN (1991); SPREP/IUCN (1989); Whistler (1976).

REASONS FOR INCLUSION 1a, 1d, 2b. Faimulivai Marsh is the largest area of freshwater marsh in American Samoa, and the only one which remains in a relatively undisturbed condition. Pala "Mud" Lake is a unique type of wetland. The mangroves are of interest as the easternmost stands in the Central Pacific.

SOURCE See references.