Appendix 2 - Vegetation Communities and Regional Ecosystems

Island Remnants of the Southern Papuan Lowlands: The Fly platform is the largest tract of
low lying country in Papua New Guinea (Loffler 1977), occupying nearly a third of the mainland.
Flat areas are poorly drained and swampy, terminating with extensive estuarine swamplands on
the southern coast. The islands of Boigu and Saibai represent remnants of this coastal plain,
possibly separated from the mainland through the erosive actions of major PNG river systems,
which include the Pahoturi, the Mai Kussa, and the Wassi Kussa Rivers. Saibai Island forms the
most elevated expression of this remnant coastal plain with gently domed inner alluvial regions
broken by tidal swamplands and marshes. Profiles in the alluvial system indicate up to a metre of
grey silty clay loam at surface, often with vertic nature (cracking clays) passing into mottled
heavy clay soils at depth. On Saibai, a well-developed lateritic profile is exposed on the northern
coastline of the island on which the major settlement is developed. This laterite is suffering
extreme erosion on the coastal fringe.
Boigu represents a lower and swampier version of Saibai, with suppressed and fragmented
alluvial remnants scattered across the islands interior, as well as on the developed northern
coastal fringe. The majority of Boigu comprises marine swamplands with limited land available
for development or settlement.
Suppressed beach ridges occur on both Boigu and Saibai Islands. These are scattered around
islands fringes forming low rises in mangrove forests. They are most extensive on the exposed
southern coast of Boigu, and the south-eastern and north-western coast of Saibai.
Coral Cays: This grouping represents a large number of smaller islands coral sand islands,
mostly (although not restricted to) the central group of islands. The most prominent of these are
Masig, Poruma, Aureed and Warraber although a large number of smaller cays are scattered
throughout the island chain. These islands are formed on coral platforms and are extremely low
lying, generally not more than 6m high (Willmott 1972). Heights for Warraber are reported as 2-
8m above mean sea level (Hart et al. nd). In contrast to the continental and volcanic islands, the
sand cays are relatively dynamic, shaped by prevailing tidal currents and subject to shifting
shorelines in response to extreme weather events.
Mangrove Islands: This is an interesting island grouping which is poorly referenced in available
literature. The mangrove Islands of Buru and Zagai are built on coral platforms, although unlike
coral cays, the islands are subject to complete tidal inundation. These Islands in the central island
group have no land elevated above the higher tidal ranges and their entire above tidal expression
is as a mangrove forest. Sassie Island has areas of elevated coral rubble and calcareous sand,
although the interior is swampy and frequently inundated within the normal tidal range.
2. Aims and Scope
The study aims to document the nature of vegetation communities in the Torres Strait Island
Group through the provision of detailed description and mapping and placement of these
communities into Queensland’s regional ecosystem framework. The developed dataset provides
baseline information suitable for sustainable land use planning and for broader natural resource
management planning, as well as providing a means to assess the regional conservation status of
Torres Strait vegetation communities under relevant state and federal legislative process.
The project scope extends to assessment of all islands with terrestrial biodiversity values. This
includes documentation of the floristic composition, structure, and extent of all vegetation
communities which have coverage under suitable remotely sensed imagery.
3d Environmental – Torres Strait Regional Ecosystem Mapping Project – August 2008
6