Threatening processes facing the region include altered hydrology, degradation of soils, loss of habitat and ecological communities, plant diseases such as Phyophthora cinnamomi (dieback), weeds and feral animals, altered fire regimes, degredation of waterways and wetlands, and climate change.
Some of the perceived social and economic threats include an increasing reliance on a decreasing number of volunteers for on-ground actions, withdrawal of government resources (skills and funds) and institutional, legislative, and market arrangements that either undervalue or actively degrade natural resources.
 Animal Pests
In Australia, pest animals including wild populations of foxes, pigs, rabbits, mice, goats, carp, dogs, cane toads, camels, cats and horses have major economic, environmental and social impacts. Many pest animals cause significant damage to crops and seriously affect Australia's livestock industries by preying on stock and competing for pasture. Pest animals also cause severe land degredation by promoting soil erosion, stream turbidity and the spread of weeds. Competition, habitat destruction and predation by pest animals threaten the survival of many of Australia's native plants and animals.
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.JPG) Weed Pests
A major threat to the fragile biodiversity of the South Coast NRM region is the invasion of weeds. Weeds degrade the habitats of indigenous plants and animals. They are among the most serious threats to Australia’s natural environment and primary production industries.
The region houses approximately 1000 species of weeds, with 300-400 species having significant impacts socially, environmentally and agriculturally. Weeds cost the economy over 10 billion each year. With ongoing climate change, the 600 species that are currently of little concern may become problematic.
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 (2).JPG) Salinity
According to hydrological zone mapping carried out by South Coast NRM, about 10 per cent of cleared land on the South Coast is thought to be affected by salinity to some extent. This area will increase to about 17 per cent in the next 15 to 25 years before stabilising at almost 24 per cent, unless high water use farming systems are adopted. The high rainfall south west will reach equilibrium earlier than the low rainfall north east.
.JPG) Wind erosion
Wind erosion is a very significant problem on the South Coast, particularly on the sandplains where the fine sands are often water repellent in autumn (inhibiting germination) and waterlogged in late winter (restricting cover over summer). Landsat images have been used to measure the extent of the problem since the early 1980s. Some areas were severely eroded up to four times between 1988 and 1993 with up to 32 per cent of some locations being affected at any one time. Increasingly, dunes are being stabilised and farmers are adopting minimum tillage or no-till and stubble retention. Increasing the area under perennials in sustainable farming systems (eg tree wind breaks, perennial pastures, fodder shrubs) is the only reliable way to reduce both wind erosion and salinity.
Water erosion
While water erosion is not perceived to be as big a threat as salinity and wind erosion in most of the region, it is very significant on a local basis. The fact that most of the phosphate entering estuaries and wetlands is particulate in form has increased the need to prevent sheet erosion through the region (almost all runoff eventually enters either a wetland or estuary). Some tracer work has shown that about 3 tonnes of soil has been lost per hectare under grazed paddocks and between 5 and 7 tonnes per hectare under cropping. Increases in the area under crops may therefore increase erosion rates unless minimum tillage or no-till methods are used. As well as sheet erosion, the erosion of river channels can cause problems such as loss of top soil, increased turbidity of river water, channel widening and deepening.
.JPG) Waterlogging and inundation
Waterlogging and inundation (surface ponding) are major problems throughout the region because of high winter rainfall, shallow clay subsoils and low relief. As a consequence the yields of most crops and pastures are well below their potential and the range of species that can be grown is limited. Almost all commercial tree plantings are on mounds to overcome the problem. Surface drainage is only effective where there is sufficient slope and there is a physically and environmentally safe disposal point.
Duplex soils have been found to be harder to drain on the sandplain than elsewhere in Western Australia, possibly because of the fineness of the sand, high volume of gravel and low slopes. This means agronomic methods rather than engineering works need to be used in most cases. Waterlogged areas contribute greatly to recharge because the accumulated water infiltrates through cracks in the subsoil and deep roots are killed.
Waterlogging will also contribute to increased flooding and could become a serious problem on the South Coast in the future. This would result in the loss of crops on adjacent farmland and riparian vegetation that is not adapted to prolonged inundation. Loss of vegetation further impacts on the ecology of rivers and wetlands through reduced bank stability and increases in erosion. Increased intensity of flooding can also result in damage to or loss of property, bridges, roads, power and other infrastructure along waterways.
.JPG) Nutrient enrichment
Nutrient enrichment is a problem for many waterways in the western part of the South Coast region where development and agriculture are more intense. Good catchment management and the targeting of point source polluters can improve waterway condition as has been demonstrated in Albany Harbours where significant decreases in the phosphorus and nitrogen loads have been recorded over the past 10 years.
 Soil acidity
The western part of the South Coast has some of the most acidic soils in the state. The high rainfall and low buffering capacity of the sandy soils has resulted in peaty soils forming in the Denmark and west Albany muncipalities. In contrast, the Mallee (Dundas Shire) has some of the most alkaline soils in the state. Lime deposits along the coast are increasingly being used to treat acidic soils. There are some planning conflicts with using these deposits, which need to be well managed. Increasing use of legumes (both pasture and grain) and nitrogenous fertilisers, may result in increased rates of acidification on South Coast soils if nitrates are allowed to leach below the root zone of plants. Deeper rooted plants will help to overcome this problem.
Soil structure decline is a widespread problem because most soils in the region are sodic or strongly sodic which causes them to set hard upon drying. In addition, sandplain soils are liable to compaction and require deep ripping to remove plough layers if cultivated with wheeled machinery. Poor structure is a cause of runoff (particularly from Moort soils) and poor root growth into subsoils (increasing recharge). Gypsum is becoming a limited resource in the Region and reduced tillage and stocking of soils in winter is a longer term solution. Some interest is being shown in using lucerne to open up clayey subsoils while intercepting waters, which have drained below the root zone of annual crops and pastures.
More than one million ha of the sandplain are water repellent when dry, resulting in poor germination (affecting yields), and causing erosion and runoff. The degree of repellence on the South Coast is greater than that on the West Coast and is exacerbated by some plant species (eg veldt grass, legumes). Given that almost all runoff eventually ends in wetlands or estuaries, and sheet erosion is exacerbated by waterlogging, water repellence and sodicity, eutrophication is a widespread problem in the region.
Vegetation decline
Clearing, stock grazing, invasion of weeds and salinisation are major causes of remnant vegetation decline in the region, that is being tackled on a number of fronts. Clearing approvals have decreased dramatically since tougher guidelines have been progressively introduced over the past six years. Funds for fencing out remnants has increasingly become available under programs such as Southern Incentives.The effect of salinity on remnants, particularly on riparian vegetation, is a major problem. |
