Most of the issues and problems involved in attempting to halt the complete annihilation of the ecosystems of the Victorian Volcanic Grasslands relate to a worldwide movement to conserve the ‘biodiversity’ of the planet’s natural resources. Biodiversity refers to the number of species, the variety of species, the relationships between them and the habitat they occupy in any given ecosystem, which could be the plains of Keilor, the Victorian Volcanic Plains, or the south-east corner of Australia. The term ‘biodiversity’ or ‘biological diversity’ came from a movement called Conservation Biology which arose last century in a response to the relatively rapid rate of extinction of species on the planet in the current historical period. Many scientists believe we are now in the sixth major extinction event of species in the history of biology on earth. Locally it might seem to be just the unfortunate loss of a few bandicoots and other small mammals we never knew the name of, but the destruction that has and is continuing to occur here and just about everywhere is part of an international tidal wave of extinction. There is a fear that we are destroying the biological fabric of the earth without really understanding the implications of this destruction. Wikipedia has a very thorough and well curated section on ‘biodiversity’.
Wetlands
Wetlands are a significant feature of the plains and originally covered up to a sixth of the land area when full of water. Wetlands are broadly defined as those naturally occurring depressions or floodplains that are covered temporarily or permanently by fresh, brackish or saline water, often determined by seasonal rains. Many of these depressions were created by volcanic activity which re-shaped the topography of the land over the last million years. These are called Gilgais, which are small ephemeral soggy depressions formed usually in clay soils under wetter weather conditions. The wetland areas have high biological diversity - they support a wide variety of native indigenous plants and animals, which are adapted to the special conditions of these wetlands and their highly variable water levels. Some plants grow at the edges; some prefer shallow water or deep water, others under the water or on the surface with dangling roots. Most of them can survive drying out and revive when water returns. The apparent extremes of wet and dry on the plains were a challenge to agriculture and settlement, so to make water supplies more predictable dams and tanks were built, shallow wetlands were drained and others made deeper and more permanent. All of this has interrupted the evolved wetland ecology and reduced habitat for many species. It has also interrupted the ability of species to travel from one water habitat to another because the distances are further. These practices isolate gene pools and threaten species survival. Furthermore, draining wetlands effectively means draining the landscape so water no longer lies around to recharge the ground water, a potential problem as we have become more reliant on ground water with the drying trend in our climate.
Shield Shrimp
One important creature of the ephemeral wetlands is the Shield Shrimp, so called because of a dorsal exoskeleton on its back shaped like a shield. Also known as the Tadpole Shrimp, this creature has not changed much in about 500 million years and is well adapted to the tough climate conditions of the plains. Shield Shrimps can be found in fresh water lakes, temporary wetlands, farm dams, drainage ditches, even rain pools or virtually any pool of freshwater. The eggs of the Shield Shrimp go through a drying out phase and can last up to ten years or even longer in this desiccated state. They can also survive very high temperatures and are blown around by the wind until water comes again and they hatch out. The shrimps grow very quickly from microscopic hatchlings and can go through several moults in 24 hours, feeding on microscopic animals in the mud and plants, eventually growing to about six centimetres when fully grown. They are an important part of the food chain and provide many of the meals for the birds that flock to these wetlands when the rains come.
Charophytes
Charophytes are primitive water plants found throughout the wetlands on the plains and are closely related to algae, although they grow out of the sediment like ordinary plants and produce seeds or spores. They date back to the Silurian era and are the closest living relatives to the ancestors of land plants. Charophytes provide habitat and food for invertebrates and water birds and are found in association with other algae. They absorb nutrients from the water and their presence is an indicator of a healthy ecosystem because they require high quality water to thrive. On the other hand Charophyte spores can remain dormant for many years and, like the eggs of shield shrimps, can survive extended periods of drought in a dessicated state, germinating when the environment becomes favourable. By studying the Charophytes that exist today, we may be able to understand the climate and water availability of the past.
