Bottle Bend Lagoon lies beside the Murray River near Red Cliffs. Naturally, the lagoon would flood, dry and flood again in a regular cycle. But in the 1920s a weir was built downstream on the Murray.
For the next 75 years, the lagoon was covered with water. It finally dried out in 2002, during the drought, and things quickly turned bad. The chemistry of the soils changed for ever. The dry lake bed turned to acid.
Wetlands like Bottle Bend rely on natural cycles of flooding and drying. They degrade when kept flooded for too long and, at the other extreme, when kept dry for too long. The only way we can prevent this problem is to manage environmental flows so important wetlands can continue to flood, dry and flood again in regular cycles.
All natural ecosystems are supported by natural processes and disturbance regimes. Wetlands rely on cycles of flooding and drying; coastal estuaries depend on the waxing and waning of the tides; forests, heathlands and other ecosystems rely on specific fire regimes.
Many animals rely on, or are most common in, forests that have not been burnt for long periods of time. We must not destroy their habitats by burning too often.
We must always make sure that human activities do not constrain these important ecological processes. Sound planning policies are critical. For example, local, state and federal governments must continue to: guarantee water for the environment, control the spread of housing in bushland areas, use fire regimes that promote biodiversity, minimise development in flood-prone coastal areas, and more.
Sound land-use planning underpins a healthy and vibrant economy, society and environment.
Natural areas will change as climate change intensifies and the natural processes and disturbance regimes that support them, like fires and floods, will also change.
Current regimes (and regimes from the past) may not create diverse, sustaining ecosystems in the future; they will, however, provide lots of valuable information to guide us. Regardless of changes, we must always ensure that natural processes operate in ways that sustain natural ecosystems and promote natural diversity.
In recent years, Manna Gums have died across thousands of hectares on the Monaro Tableland in southern NSW. No young trees have replaced them. Tree deaths were most severe where the least rain fell.
This devastation has triggered a lot of discussion: if Manna Gums will not survive in this region under a new climate, then what (if any) species should we plant in their place?
One obvious way to promote biodiversity is to replace the dead trees with species from nearby dry regions that perform similar functions to Manna Gums. Functions like:
More broadly, we can help plants and animals by replenishing key habitat features, especially features that create cool and moist micro-habitats: like shady trees, hollow branches, logs and leaves on the ground, and reeds and rushes around dams and wetlands. We may never replace Manna Gums on the Monaro but we can replenish the habitat that Manna Gums used to provide.
Banner image: Black Saturday fire aftermath at Wilsons Promontory National Park. Credit Phil Ingamells.
This content is adapted with permission from text written by Dr Ian Lunt for the VicNature2050 booklet 10 things we can all do to help nature adapt to a new climate.
VicNature2050 was organised by the Victorian National Parks Association, The Royal Society of Victoria and The University of Melbourne’s Bio21 Institute, and supported by the Victorian Department of Environment, Land, Water and Planning and Parks Victoria.
Other organisations who have participated in the VicNature2050 partnership include La Trobe University; Deakin University; Greening Australia; and the Arthur Rylah Institute for Environmental Research.