Types of Land Degradation

1. ISSUES IN THE AUSTRALIAN
ENVIRONMENT
Land Degradation
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2. Land Degradation
• Definition:
• Causes:
Any change that decreases
productivity of the land
-Land clearing
-Poor land management
practices
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3. • Poor land management practices include
grazing of stock that has hard hooves,
growing of crops that require large amounts
of fertilisers and pesticides especially
superphosphate and nitrogen, and irrigation
for crops on sandy soils.
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4. Water Erosion
• Definition:
removal of soil particles by
heavy rainfall or running water
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6. • Soil is washed downhill beneath the surface with
a resultant collapse of the unsupported surface
soil which results in an undermining and
subsidence of the banks of flooding rivers and
creeks.
• Under normal conditions, where slopes have
vegetation cover; there is less surface runoff and
more water is infiltrated into the soil. The
vegetation forms a layer of humus (leaf litter) on
top of the top soil layer and this helps to stabilise
soil movement.
• Under conditions where there is no vegetation
cover, there is major surface runoff, and this
carries loose soil with it, as there is no humus
layer to stabilise the soil. Also making rills and
channels. The soil particles can be washed into
waterways and deposited at the base of slopes.
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7. Sheet Erosion
• Caused by soil particles being transported
with runoff on a downhill slope causing
other layers of soil and rock to be exposed.
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8. Rill Erosion
• Caused by no vegetation cover and increased water
movement downslope. The movement carries loose soil
and also makes rills into the side of the slope.
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9. Gully Erosion
• As major volumes of water moves downslope, channels
form and the soil is deposited at the base of the slope.
This is caused by no vegetation cover.
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10. • If soil is washed into waterways it increases
the turbidity (muddiness) of the water. This
is because the sediments are suspended in
the water.
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11. Wind Erosion
• Definition: This is when loose soil particles are
collected by the wind and transported to another
location.
• It happens in areas which have sandy soils and low
rainfall
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12. Strategies for reducing wind erosion
• minimising the amount of time that the soil has
no vegetation cover
• increasing vegetation cover and decreasing
stock rates
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13. • Eliminating introduced animals which strip
vegetation eg. rabbits
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14. • Building contour banks (raised areas of soil along
slopes to reduce water downslope)
• Ploughing across slopes not down the slope
• Planting trees to form windbreaks
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15. Salinity
•
Primary Salinity
CAUSE:
low, erratic rainfall
high evaporation rates
When there is not enough water to leech out salts from soil, (which
occur naturally), the salt forms a crust and rises to the surface as
the moisture in the soil is evaporated. Usually in this situation
there is no waterways to help flush the salty areas.
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16. • Secondary Salinity
CAUSES:
-Man made activities that alter the natural
balance of the catchment area.
-There is movement of the soil profile (the
layers of different types of soil and
minerals) and groundwater.
-There is extra water added to the
groundwater by irrigation or vegetation is
cleared.
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17. Dryland Salinity
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18. Indicators:
Seeps (seepage areas)
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19. • Scalds
Occur when water or wind erosion removes
the topsoil exposing the salty subsoil
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20. When the native vegetation has been removed, and crops
and pastures that have shallow root systems, the
subsoils have been destabilised.
Watertables have risen bringing dissolved salts to the
surface.
Rivers are experiencing salinisation by the dissolved salts
being collected in surface runoff and washed into the
waterways and therefore polluting them.
Major filtration has to occur to make it palatable (able to
be used for drinking water).
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21. • Irrigation Salinity
The water seeps through the soil causing the water table
to rise. The dissolved salt in the soil makes it’s way into
the vegetation root system, and therefore causing it to
die.
Salination can also occur through salty surface runoff,
caused by too much irrigation.
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23. How can salinity be managed?
• Plant deep rooted vegetation to reduce
groundwater recharge and increases
evaporation through plants
(evapotranspiration).
• Proper drainage and pumping of irrigation
• The problem can not be looked at in isolation
from other land management problems. Total
Catchment Management needs to be employed.
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24. Total Catchment Management
AIM: To reduce degradation of soils and water in a
catchment area.
This takes into account all available resources and uses in
the area.
The decisions are made by government agencies, services,
farmers, industries, communities and recreational
users. Each group must work to achieve the best
decision.
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