Land Management Issues

When managing a landscape for sustainability and productivity, land management practices need to consider the effects on the native flora and fauna.  The introduction of agriculture practices has resulted in land degradation, which affects the health of the landscape.  Some of the major land degradation issues of the SA MDB are listed below;

Wind Erosion

Wind erosion is a major problem with the sandy soils of the Murray Mallee and Murray Plains and is caused by the displacement of soil particles, a result of the removal of native vegetation and inappropriate land management practices.  Maintaining adequate groundcover through conservation farming methods and increasing the organic content of the soil will help minimise wind erosion.

Water Erosion

Water erosion occurs on the landscape when rainfall intensity is higher than soil infiltration rates, resulting in the displacement of soil particles.  The key factors contributing to water erosion are soil type, land slope and rainfall intensity.  As with wind erosion, maintaining an adequate cover of vegetation and groundcover will assist in reducing the velocity and energy of the runoff water.

• Gully erosion occurs when intense flows of water cause deep trenches along watercourses - a major problem in the SA MDB Rangelands, Mount Lofty Ranges and Murray Plains
• Sheet and rill erosion occurs when rain drops and surface flows cause shallow stripping of the soil

Lakeshore Erosion

Lakeshore erosion, caused by wave action, stock access, loss of protective reed beds and the maintenance of high lake levels, is a major problem around the shorelines of Lake Alexandrina and Lake Albert. The removal of the protective shoreline vegetation has resulted in the loss of considerable areas of adjacent land and is accelerated by the grazing by stock on the unprotected shoreline.  Soil washed into the lakes reduces water quality thus impacting on the aquatic ecosystems of the lakes and Coorong.  Fencing to exclude stock from the shoreline and re-establishing native vegetation will help reduce the impact.

Dryland Salinity

Salinity is a natural feature of the Murray-Darling Basin due to its geological history.

Prior to the clearing of native vegetation, all rainwater was effectively intercepted, preventing it from moving through the landscape. Salinity that has occurred as a result of agricultural practices is known as secondary salinity, of which there are two types;

• Dryland salinity occurs when deep-rooted native vegetation is cleared and replaced with shallow rooted annual crops, resulting in water tables rising as recharge increases.
• Irrigated salinity is a result of groundwater rising through irrigation drainage.

The Murraylands and parts of the eastern Mount Lofty Ranges are the areas within the SA MDB, which have the highest recharge potential.  Ground water recharge can be managed through the planting of deep-rooted perennial in areas of recharge and improving the water use efficiency of crops and pastures.

Major Issues Biodiversity

Inappropriate land management practices not only reduce sustainability and productivity but can also have a detrimental effect on biodiversity.

Habitat Fragmentation & Isolation

The broadscale clearance of native vegetation has resulted in the loss of habitat for flora and fauna.  Much of the landscape across the SA MDB consists of small blocks of isolated native vegetation surrounded by agricultural land.  While larger blocks of native vegetation are able to withstand impacts due to their size and isolation, smaller blocks of native vegetation are vulnerable to weed invasion, feral animals, grazing and chemical drift.  Establishing native vegetation around smaller blocks will increase their size, providing habitat and reducing negative impacts from surrounding landuse.

Grazing particularly overgrazing has resulted in the degradation of large areas of the native vegetation in the SA MDB.  Overgrazing can have a number of detrimental impacts on biodiversity, such as preventing the regeneration of certain species, a depletion of the seed bank and changes to the water surface flow.  Reducing stocking rates and changing management practices can assist in reducing land degradation.

An Environmental weed is a weed which has a detrimental effect on native vegetation.  An environmental weed competes with the native plants for light and nutrients and can potentially change the composition of the soil.  They also have a negative effect on native fauna, as many rely on native vegetation for food source and habitat.  To prevent further loss to biodiversity it is essential that environmental weeds are managed and controlled.