Spanning the border between Papua New Guinea and the Indonesian province of Irian Jaya, this EBA encompasses the lowlands south of and bordered by the Digul, Fly and Aramia rivers-one of the most extensive areas of low relief in New Guinea.

The southern region of New Guinea has a strongly seasonal climate and the dominant vegetation types are savanna and monsoon forest which are comparable to those of northern Australia. A wide variety of habitats is present within the EBA including significant expanses of savanna and woodland, seasonally inundated grassland, marsh, reedbeds, monsoon forest, gallery forest, mangroves and tidal mudflats.

The restricted-range species occur in a variety of wetland, savanna and forest types. Five are confined entirely to this EBA and the Aru Islands (treated separately as Secondary Area s112). The sixth species, Cinclosoma ajax, has a very patchy distribution in this EBA and in other EBAs and Secondary Areas.

Megalurus albolimbatus has a particularly small range, being known from a few localities only-including Lake Daviumbu on the middle Fly river, the Bensbach river and Wasur National Park in Irian Jaya-although much potential habitat is unsurveyed and it could therefore occur more widely. It appears to be highly specialized in its wetland habitat requirements, birds in the Wasur National Park being confined during the breeding season to stands of tall, coarse sedges (N. Stronach in litt. 1996).

As with other regions of New Guinea, this EBA is inhabited by a large number of sparsely distributed tribal groups which depend on local biological resources for sustenance. Access is mostly poor and consequently the region has suffered little disturbance overall (WWF/IUCN 1994-1995). However, the population in the Indonesian part of the EBA has been increased through transmigration settlement, and the resulting increase in hunting pressure, trade in birds, conversion of natural habitats for agriculture, and unsustainable cutting of forest trees for timber have affected some wildlife habitats in general and as well as reducing populations of particular species (N. Stronach in litt. 1993, 1996). The building of new roads into the region, e.g. the Trans-Irian Highway between Jayapura and Merauke, will also result in the local depletion or extinction of some species (K. D. Bishop in litt. 1993, P. Gregory in litt. 1996).

Additional threats come from introduced rusa deer Cervus timorensis which overgraze and trample reedbeds, especially in the Bensbach area-although, according to local people, there has been a recovery of wetland habitats following major reductions in the deer population over the past ten years. Though little studied, the effects of introduced animals are likely to be much wider than just those due to deer. As a further example, grasslands in general appear to be under threat by encroachment of swamp woodland, itself possibly promoted by the activities of both deer and pigs, which cause changes in hydrology favouring tree establishment (N. Stronach in litt. 1993, 1996). There are recent rumours of monkeys (presumably macaques) in the lower Fly/Irian border region, probably brought here by Javanese migrants (P. Gregory in litt. 1994); if these animals become established they could cause an ecological disaster throughout New Guinea, predating on nests and perhaps even out-competing fruit-eating birds which have evolved in the absence of primates.

The mining activities of Porgera Joint Venture Ltd and (particularly) Ok Tedi Mining Ltd (at Tabubil) have been the focus of significant national and international attention, and an appraisal of the long-term implications of development activities within the whole catchment has been undertaken (IUCN 1995). Although silt from the mine workings at Ok Tedi has spread from the riverbanks killing all vegetation in places, only relatively small areas are affected and fish stocks in the mid and lower Fly appear much as in the past; the situation along the Strickland river, where the gold mine waste from Porgera enters, is less well known, and toxicity may be higher (P. Gregory in litt. 1996).

The region has been identified by Beehler (1993) as important for terrestrial and wetland biodiversity in Papua New Guinea. As well as being important for restricted-range species, three widespread threatened birds occur there-Southern Cassowary Cassuarius cassuarius, Southern Crowned-pigeon Goura scheepmakeri and New Guinea Harpy Eagle Harpyopsis novaeguineae (all classified as Vulnerable)-and it is a famous haven for widespread wetland birds, including large numbers of wintering Australian and Palearctic waders and waterfowl. In Australian drought years the Trans-Fly becomes an important refuge for Australian wetland birds.

There is a protected area on the Irian Jayan side, Wasur National Park (3,080 km²), and contiguous with this on the Papua New Guinea side is Tonda Wildlife Management Area (5,900 km²) which includes the floodplains of the Bensback and Morehead rivers. Within Wasur National Park there is pressure to manipulate water-levels by engineering projects, canalization, etc., to supply water to Merauke, and in both protected areas grassland is changing to woodland at a rapid rate (N. Stronach in litt. 1996). The Danau Bian Wildlife Sanctuary (694 km²), to the north of Wasur, and Pulau Kimaam (6,000 km²), an island separated from the mainland by a narrow channel, both cover extensive swamps, freshwater lakes and associated marshes, and monsoon and alluvial forests (Scott 1989, Sujatnika et al. 1995).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Trans-Fly. Downloaded from https://datazone.birdlife.org/eba/factsheet/179 on 22/11/2024.