By Jenna Gersie
Driving through South Australia doesn’t look like much: mile after mile of flat, dry grassland beneath an endless blue sky; the occasional eucalypt punctuating the farmer’s fields; barbed wire fences lining the roadside and dust rising up from the tires; more sheep than humans. But amidst this vast and barren landscape I stumbled upon a refuge. Near the town of Naracoorte, famous for its caves and fossils of extinct Australian megafauna, the swampy Bool Lagoon provides an oasis for birdlife.
Declared a wetland of international importance under the Ramsar Convention in 1985, Bool Lagoon provides a home to over 150 water bird species, twenty-seven of which are migratory species. The Latham’s Snipe, for example, winters in South Australia before returning to the grasslands of northern Japan to breed. I wasn’t surprised to learn that this refuge hosts so many water birds; among the birds I saw were the Black Swan, White Ibis and Straw-necked Ibis, Australasian Shoveler, White-faced Heron, Australian Shelduck, Black-winged Stilt, White-necked Heron, Australian Bittern, Pacific Black Duck, Purple Swamphen, Magpie Goose, and Eurasian Coot.
Bool Lagoon and the adjacent Hacks Lagoon are set aside to provide habitat for birds such as these, to provide a drought refuge for wetland dependent species, and to represent an inland lagoon system that flows over rich alkaline soils. The basin where Bool Lagoon currently lies began to form 150 million years ago, when Australia began to separate from the larger landmass known as Gondwana. Fifteen to twenty million years ago, high sea levels deposited sand, silt, and marine sediments in layers up to 6,000 meters thick. The sea level dropped, but two million years ago, they rose again, this time depositing shelly, sandy limestone and calcareous sands. When the sea levels dropped again, they eroded away earlier deposits of sediment, creating the siltstone that is found in the lagoon today. The shallow, circular swamps that make up Bool Lagoon were formed within these layers of sediment by rising ground waters that penetrated the substrate and eroded the limestone.
The Bool Lagoon system, which is made up of the lagoon itself and Mosquito Creek, which feeds floodwaters into the lagoon, together make up a 1500 square kilometer catchment area. The wetland, when at full capacity, has water that covers 2530 hectares and forms a chain of shallow, freshwater lagoons about 10 kilometers long. Though the water may be one meter deep during the winter months, it can get quite dry during the summer. When we visited, we saw both dry ground and dark water, where reeds and rushes thrived.
We walked along a boardwalk, past clumps of Swamp Paperbark (Melaleuca halmaturorum), also known as Tea Tree, which provides nesting habitat for thousands of birds. The wind caught the whispers of the reeds that lined the boardwalk, and the sky was clear except for some small clouds, no more than watermarks on the distant horizon. A small Whiskered Tern flew about in the wind like a kite being pulled along by a string and a Swamp Harrier spread its wings in the distance in search of food. Willie Wagtails and Australian Magpies, common in most places, joined the assembly of birds that we watched, up close and through the lenses of our binoculars.
This haven, with its interesting geological, hydrological, and biological features, has relied on the efforts of the community and conservation groups to achieve protection, providing nesting and feeding sites for countless species of birdlife, as well as habitat for threatened animals such as the Southern Bell Frog, Striped Legless Lizard, Yarra Pygmy Perch, and Dwarf Galaxias.
Conservation efforts for Bool Lagoon began as early as 1940, when the Flora and Fauna committee of the South Australian Ornithological Association proposed that it be declared a bird sanctuary. However, landholders and hunters lobbied to oppose this plan; the hunting community also opposed a plan in 1960 to drain the lagoon. But ultimately, it was enthusiasm from the hunting community to declare the area a game reserve that afforded Bool Lagoon its protection. In 1963, the Fisheries and Game Department developed a management plan for Bool Lagoon to hold floodwaters and conserve waterbird habitat, and in 1967, the lagoon was dedicated as a game reserve, while the adjacent Hacks Lagoon was dedicated as a conservation park.
The South Australian Field and Game Association (SAFGA) has been actively involved in conserving the lagoon for years. Beginning in 1978, the South East Branch of SAFGA has implemented projects in Bool Lagoon such as constructing and monitoring nest boxes, conducting weed control projects, repairing fencing destroyed during bushfires, revegetating areas, and planting Melaleuca seedlings. SAFGA members have purchased sections of land to add to Bool Lagoon with funds collected from hunting permit fees, and they regularly conduct wetland and waterfowl surveys to properly manage the area. Today, Bool Lagoon is managed in conjunction with the South-Eastern Drainage Board, which releases floodwaters held within the lagoon at a controlled rate to prevent flooding of the Naracoorte Plains.
Only 11% of wetlands in southeast South Australia remain today, most of which are seasonal and only 14% of which are considered permanent areas of open, fresh water. This decline in wetland habitat makes Bool Lagoon even more significant for the birdlife that it supports. Seeing an Australian Bittern fly across the water to hide in the reeds and watching the elegant Black Swans floating on the dark water make me grateful that such areas have been set aside.