The Boondall Wetlands are located on the edge of Moreton Bay between Nudgee Beach, Boondall and Shorncliffe. They include more than 1000 hectares of tidal flats, mangroves, saltmarshes, melaleuca wetlands, grasslands, open forests and woodlands, have a diversity of wildlife, including flying foxes, possums, squirrel gliders, frogs, reptiles and butterflies and have an amazing variety of birdlife, including black-shouldered and brahminy kites, Australian kestrels, whimbrels, sandpipers, kingfishers and rainbow bee-eaters.
History and environmental significance
Indigenous Australians used to have campsites and ceremonial grounds at Boondall Wetlands and still have strong links to this land. In 1863, the Catholic Church acquired 3,000 acres of 'Nudgee lands' cut timber, grew small crops and grazed cattle. Brisbane City Council acquired the land in the 1960s, planned for wetlands to be developed in the 1970s and 1980s and created the Boondall Wetlands Reserve in 1990 after public concern.
The Boondall Wetlands have ties with the Yatsu-Higata Tidelands of Japan as part of the Narashino Agreement. Large numbers of international migratory shorebirds travel between the City of Narashino, Japan and Moreton Bay each year. They reside in Boondall Wetlands between September and March each year.
Threats to wetlands
Wetlands across the world are under threat from human activities including increasing human population pressure, increased demand for resources and land, particularly in coastal areas, pollution and illegal dumping of waste. Since European arrival approximately 50% of Australia's original wetlands have been cleared.
The healthy and natural balance of the wetlands are disturbed by exotic weeds and feral animals in the area, frequent fires that rarely burn naturally, providing favourable growing conditions for many weeds and unsustainable recreational activities such as over-fishing.
Geology and Water Chemistry
The water that flows through a wetland is the source of nutrient elements for the plants and therefore is ultimately the basis of mineral nutrition for all the inhabitants of wetlands. The most abundant elements in living plants and animals are carbon and oxygen. Both of these elements are present in the atmosphere as the gases carbon dioxide and oxygen, and are also easily dissolved in water, so there is not usually any problem in obtaining them. When the gases are in a dissolved state, however, they move (diffuse) much more slowly than in air, which means that they can be in short supply if the water itself is stagnant, causing problems.
Hydrogen is also an important element in plants and animals, and its concentration in water has an important effect on many other chemical reactions.
Nitrogen is present in the form of the nitrate ions. Nitrates arise as a result of the decomposition of the dead proteins from plant and animal matter.
Calcium is an important element for both plants and animals, but especially for animals that have a bony skeleton (including many fish and amphibians) and also those mollusks that have a shell (such as mussels and snails). Calcium comes from the erosion of rocks in the catchment and has a considerable influence on the types of plants and animals that are found in a wetland.
Phosphorus is another essential element for all living organisms. It is needed for energy storage and exchange in every cell and is also an important component of all the membranes that surround each cell and regulate their movement.
Sodium and potassium are considerably more common in nature than phosphorus, and animals need both. Potassium is needed for muscle and kidney function in animals, and sodium is required for the activity of nerves.
Magnesium is an important component of the pigment chlorophyll, which green plants need to carry out their photosynthesis. Together with calcium, magnesium is responsible for the "hardness" of water. Water rich in calcium and magnesium is said to be "hard," and it is difficult to produce soapy bubbles in such a medium. Water poor in calcium and magnesium, on the other hand, is said to be "soft" and is more suitable for washing.
Geology and Wetland Landscapes
Wetlands can develop only in regions where water accumulates, and this means that the ground underlying the wetland must be impervious to water. Some rocks are much more easily penetrated by water than others. Limestone, for example, absorbs water, so water gradually sinks through it.
Sandstone is made up of numerous sand grains compacted and cemented together, but there are usually tiny spaces remaining between the grains. Therefore water can seep through the rock and drain away. Granite is formed by volcanic activity, which produces a molten rock that subsequently cools and crystallizes. As a result all air spaces in the rock have been sealed, and it is impervious to water.
Unlike sandstone, which has undergone no further process following compaction, shale and slate have been heated to high temperatures because of nearby volcanic activity. The intense heat changes their form by sealing any pores in their structure, making them impervious to water. Where there is standing water in a valley, it is certain that the underlying ground is waterproof, resisting the tendency of water to soak downward under the influence of gravity.
Even porous rocks can be made impervious if fine particles of material block up the pores. This can happen if the waters draining into a valley carry a load of eroded material from the catchment rocks, which settles onto the surface of the porous rocks and forms a layer that seals them. Clay consists of very fine particles, less than 2 mm, so they are easily carried long distances by moving waters. When the water arrives in the valley, some of these particles settle as the speed of the water decreases, and they may block up the pores in the underlying rocks and create a waterproof barrier that allows a wetland to develop.
Underlying geology provides the base on which wetlands can form. But the form of the landscape also has an effect on wetland development. Under conditions of very high rainfall, peat-forming wetlands may develop even on mountain ridges and slopes. However, wetlands are generally more abundant in hollows in the landscape, where water can accumulate. If we consider a region where the underlying bedrock is impervious to water (granite, shale, or slate, for example), then wetlands are most likely to be found in valleys or in hollows in the general landscape. Wetlands of this kind are called topogenous, which means that they are dependent on the topography of the landscape.
A second type of wetland is the soligenous wetland. This is similar to the topogenous wetland in that it lies in hollows, but it is fed by the emergence of water from the ground as a result of porous, water-laden rocks meeting impervious rocks below. Where the two come into contact, the water descending under the influence of gravity through the porous rocks is unable to continue its descent but is forced to move sideways over the surface of the impervious rock until it emerges as a line of springs. These springs then feed the wetland that develops along the line of the rock boundary and in the hollows that lie below that line.
A third type of wetland that is dependent on the general form of the landscape is the floodplain wetland. This occurs in the lower parts of river valleys, where the landscape is broad and flat on either side of a river that often meanders down a gentle slope on its way to the ocean. At this stage in its development a river has often traveled great distances and has been joined by many tributaries, so its water is supplied by a wide catchment. If there are heavy rains over that catchment, or even over a small part of it, floodwater accumulates in the river channel and moves swiftly downriver.
Citation from:
• History and environmental significance: Welcome to the Boondall Wetlands (Brisbane City Council 2015, 2)
• Threats to wetlands: Welcome to the Boondall Wetlands (Brisbane City Council 2015, 4)
• Geology and Water Chemistry: Geology of Wetlands (Peter D. Moore 2006, 46-51)
• Geology and Wetland Landscapes: Geology of Wetlands (Peter D. Moore 2006, 42-46)
Logging the cache
Please email us the results of the following questions. Feel free to log before receiving a permission from us. We'll contact you if anything is unclear.
- Using the information above, what geological materials do you see?
- What's the name of the convention the Boondall Wetlands are listed under as internationally important for the migratory shorebirds?
- How would you describe the importance of wetlands? What are they good for?
- As described what type of wetland do you see?
- Was the water in the wetlands moving during your visit?
- Optional: Post pictures of the wetlands, we'd love to see them! :-)
(photo courtesy of Brisbane City Council)