Australian Wetlands Database

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Forrestdale and Thomsons Lakes

Overview

Key facts and figures:

Date of listing:

07 June 1990

The lakes provide important habitat for waterbirds on the Swan coastal plain,  Photo: J. Lane

Australian Ramsar site number:

35

Criteria: 

1, 3, 5, 6

State/Territory:

Western Australia

Area:

Forrestdale Lake: 246hectares
Thomsons Lake: 538hectares

Drainage Division or IMCRA  region:

South-West Coast

Wetland type: 

  • P - Seasonal/intermittent freshwater lakes (over 8 ha); includes floodplain lakes

Key features of the site:

Forrestdale Lake is located in the City of Armadale and Thomsons Lake is located in the City of Cockburn both of which lie within the southern Perth metropolitan area, in Western Australia. The lakes are surrounded by medium density urban development and some agricultural land. The sediments of Thomsons Lake are between 30,000 and 40,000 years old, which are the oldest lake sediments discovered in Western Australia to date.

Forrestdale and Thomsons Lakes are fresh/brackish, seasonal wetlands, predominately fed by groundwater. Forrestdale Lake usually dries out by mid-summer whereas Thomsons Lake retains water longer and in some years does not dry completely. These lakes are the best remaining examples of brackish, seasonal lakes with extensive fringing sedgeland, typical of the Swan Coastal Plain.

Forrestdale and Thomsons Lakes are situated in sand dune systems and contain large areas of open water fringed by rushes and bulrushes, behind which are trees tolerant of seasonal waterlogging. The higher ground around the lakes supports open woodland. The lakes provide important habitat for waterbirds on the Swan Coastal Plain with 72 species of waterbird occurring at the two lakes and 21 of them breeding. Twenty-one species of migratory birds protected by international migratory bird conservation agreements have been recorded at the lakes.

Thomsons Lake is one of the last remaining Swan Coastal Plain refuges for the Australasian Bittern, and the only remaining wetland within the Perth metropolitan area where the Marsh Harrier still breeds.

Forrestdale Lake was traditionally an important tortoise hunting site for indigenous peoples from as far away as Pinjarra, 50 kilometres to the south. Contemporary uses of the Ramsar site include bird-watching, nature walks, horse riding and general recreation.

Justification of the listing criteria:

The Forrestdale and Thomsons Lakes Ramsar site meets four of the nine criteria:

Criterion 1: Forrestdale and Thomsons Lakes are the best remaining examples of wetlands of their type on the Swan Coastal Plain. Although formerly common, extensive development has resulted in the loss of many wetlands of this type, and most remaining examples have been degraded through drainage, excessive nutrients and the loss of fringing vegetation.

Criterion 3: Thomsons Lake is one of the last remaining refuges within the Swan Coastal Plain for the Western Australian-listed threatened Australasian Bittern. It is also one of few known breeding localities for Baillon's Crake, and is the only remaining wetland within the Perth metropolitan area where the Swamp Harrier still breeds.

Criterion 5: More than 20,000 waterbirds have been recorded on both Thomsons and Forrestdale Lake. Research indicates that conditions at both lakes are suitable for use by more than 20,000 waterbirds at least several times within a 25 year period.

Criterion 6: Thomsons Lake regularly supports more than 1% of the national population of four shorebirds: Red-capped Plover, Black-winged Stilt, Red-necked Avocet and Curlew Sandpiper. Forrestdale Lake regularly supports more than 1% of the national population of five shorebirds: Red-capped Plover, Black-winged Stilt, Red-necked Avocet, Long-toed Stint and Curlew Sandpiper.

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.