A review of environmental and economic values and baseline scientific survey of the south west region

An extensive literature review and additional field surveys have revealed the diverse environmental and socio-economic values of Exmouth Gulf. Exmouth Gulf contains globally significant features including: a humpback whale nursery; an extensive undisturbed and unique arid zone mangrove ecosystem; subterranean stygofauna and fossil Pleistocene coral reefs.

The Gulf and North West Cape are a biogeographic feature separating the North West Shelf from the Dirk Hartog Shelf, which has interacted with sea level changes over geological timescales and is thought responsible for the speciation of Western Australia’s endemic marine fauna and flora. The gulf encompasses a diversity of habitats including subterranean karst limestone waterways of Outstanding Universal Value, a Threatened samphire wetland Ecological Community, extensive mangroves, modern coral reefs, seagrass beds, high intertidal cyanobacterial mats, macroalgae-dominated reef flats, intertidal sand flats, soft coral and sponge beds, oyster beds, undisturbed islands and sandy beaches. This diversity of habitats supports a high biodiversity of invertebrate and vertebrate fauna.

This report has revealed that the Exmouth Gulf contains the following biodiversity attributes:

• 8 known marine mammal species and a further 20 marine mammal species likely to occur there; including nursery habitat for Western Australian Humpback whale population; feeding and mating habitat of the north Western Australian dugong population; and populations of coastal dolphins (including the Australian snubfin, Australian Humpback and inshore Bottlenose dolphin).

• > 63 species of elasmobranch (sharks and rays) have been officially recorded including two Critically Endangered sawfish and their pupping habitats, juvenile habitat for the Giant Shovelnose ray and Leopard Whipray, and manta ray aggregations. The Exmouth Gulf Mantas migrate to Shark Bay and are the same population that support ecotourism on Ningaloo Reef and Coral Bay.

• > 15 species of sea snakes including endemic, undescribed and Critically Endangered species.

• Globally unique subterranean stygofauna assemblage associated with underground subterranean karst limestone waterways.

• Five species of sea turtles including juvenile feeding habitat for Critically Endangered Hawksbill turtles and other Endangered and Vulnerable species

• 790 species of teleost fish, including juvenile habitat for commercial and recreational species, newly described species, range extensions and a diverse, yet poorly understood seahorse and pipefish assemblage.

• 831 species of gastropods, bivalves and cephalopods, 143 species of echinoderms, and 173

  species of crustaceans characterized by significant instances of endemism such as the Cowrie Zoila species complex, Endangered and Vulnerable holothurians (sea cucumber species); and commercially valuable panaeid prawns and crabs.

• The world heritage inscribed Karst Limestone Stygofauna consisting of at least 11 endemic fauna including the Blind Cave Eel (Ophisternon candidum) and Blind Gudgeon (Milyeringa veritas).

• 95 species of migratory and resident shorebirds, waterbirds and seabirds and important nesting, feeding and roosting habitat for 36 Migratory, four Endangered, 11 Near Threatened and two Vulnerable species.

In some instances, we understand the importance of Exmouth Gulf to maintaining these species. In other cases species are known from just one or a few records and the importance of the Exmouth Gulf’s habitats to the maintenance of these species is not yet well understood. This ecosystem also sustains economically and socially important commercial and recreational fishing, ecotourism and recreation sectors worth tens of millions of dollars annually.

In 1994 the WA Government Marine Parks and Reserves Authority recommended that the Gulf be considered for marine park zoning; and in 2004 the World Heritage Consultative Committee recommended the area should be proposed for world heritage status. Despite this importance, relatively little is understood of the baseline conditions or processes maintaining this unique ecosystem’s productivity, biodiversity and values.

In particular, we do not have adequate knowledge to assess the potential environmental impacts of industrial coastal development within this unique ecosystem. A number of proposed and approved large scale coastal industrial developments within Exmouth Gulf have previously been discontinued or rejected.

It has generally been viewed that there is inadequate knowledge available for environmental assessments within Exmouth Gulf and that the large and negative impacts of any large scale coastal industrial developments would not be consistent with conserving its ecological and socio-economic values.

However, currently there are a number of large-scale industrial developments proposed, including a pipeline fabrication facility, at the southern end of the Gulf concurrent with proposed rezoning of land for industrial use along the western coast. To ensure the maintenance of this unique ecosystem’s productivity, biodiversity and values, and to address the many knowledge gaps on ecosystem function, there is an immediate need to implement a large scale multidisciplinary Exmouth Gulf Marine Research Program.

This should inform a Strategic Assessment, as defined under the Environmental Protection and Biodiversity Conservation Act, Commonwealth, 1999 (EPBC Act), of past, current and future cumulative impacts. This will enable the implementation of a spatial management plan and set limits on development.