Australian Wetlands Database

Ramsar wetlands

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Hosnies Spring

Overview

Key facts and figures:

Date of listing:

11 December 1990

Stand comprising some of the largest Mangrove Trees ever recorded,  Photo: Max Orchard

Australian Ramsar site number:

40

Criteria: 

1,3,4

State/Territory:

External Territories

Area:

202 hectares

Drainage Division or IMCRA  region:

Christmas Island Province

Wetland type: 

  • 6 - Water storage areas; reservoirs/barrages/dams/impoundments (generally over 8 ha)
  • C - Coral reefs
  • D - Rocky marine shores; includes rocky offshore islands, sea cliffs
  • Xf - Freshwater, tree-dominated wetlands; includes freshwater swamp forests, seasonally flooded forests, wooded swamps on inorganic soils
  • Y - Freshwater springs; oases

Key features of the site:

Christmas Island is an Australian External Territory located in the Indian Ocean approximately 2800 kilometres west of Darwin and 500 kilometres south of Jakarta, Indonesia. The Island is approximately 13 500 hectares in size, 63 per cent of which is national park, including two Ramsar wetlands: Hosnies Spring and The Dales. Christmas Island National Park is managed by Parks Australia.

Hosnies Spring is a small area of shallow freshwater streams and seepages, 20-45 metres above sea-level on the shore terrace of the east coast of the island. The Ramsar site consists of a stand of two species of mangroves of the usually tidal genus Bruguiera. The Ramsar site includes surrounding terrestrial areas with rainforest grading to coastal scrub, and includes an area of shoreline and coral reef.

Whilst mangroves of this group are distributed widely across the region, on Christmas Island the species are rare. The stand represented at Hosnies Spring is most unusual in that it occurs high above sea level (24-37 metres) on an inclined surface, the mangroves are unusually tall (up to 30-40 metres high) and because it appears that the stand has persisted at the site for approximately 120 000 years. The stand is maintained by the permanent freshwater spring.

The structure of the stand is also unusual in that it consists of a few very large individuals and abundant saplings and seedlings, typical of a population of long-lived trees where few individuals reach full height. The site is an example of a specific type of wetland unique to Christmas Island and perhaps unique worldwide.

The Ramsar site also provides part of the restricted habitat of the blue crab which is protected on the island. Other crab species that occur in the site are the red crab and robber crab.

Hosnies Spring is isolated and relatively inaccessible so there is minimal human impact on the area.

Justification of the listing criteria:

The Hosnies Spring Ramsar site meets three of the nine criteria:

Criterion 1: Hosnies Spring Ramsar site is an example of a highly unusual wetland that is unique to Christmas Island. The mangrove stand grows at a height of 24-37 metres above sea level, it has trees that are unusually tall along with abundant saplings and seedlings, and it is estimated that the stand has persisted for 120 000 years.

Criterion 3: The mangrove forest present at the site is unique within the bioregion and possibly worldwide. The stand comprises two mangrove species both of which usually occur in intertidal zones. It is thought that the stand is a relict of times when the site was inundated by the sea more than 120 000 years old ago.

Criterion 4: The site is important for the blue crab, which is reliant on the freshwater provided by the spring to maintain respiratory function. The spring is one of the few permanent sources of freshwater on Christmas Island and acts as a dry season refuge for a number of species. In addition, the site is a likely migratory route for endemic red crab during breeding migrations.

Please see the More Information page for additional information on this Ramsar site and access to the Ramsar Information sheets and other associated site documents.