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(Narrator) Salt -- white death.
All over Australia it's rising out of the ground
and destroying our farms, homes, and towns.
To understand why we have this problem
we need to go way, way back in Australia's history.
Australia was once part of a huge super continent called Gondwana.
It was joined to Antarctica, India, Africa, and South America.
Since then a lot has happened to the land that became Australia.
During a severe ice age part of it was covered by an ice sheet.
As the ice moved across the land it ground up rock to make new soil.
It was the last time new soil was made that way in this continent.
Later, India broke away.
The climate was much wetter than today,
and parts of Australia sank under the weight of river sediments.
Still later, when the sea level rose, a lot of the land went under water.
Then the east coast tilted up
when it broke from the New Zealand subcontinent,
and at the same time parts sank, and continued to sink.
When Australia finally broke free of Antarctica,
large areas were still sinking.
One of those areas forms the Murray Darling River Basin,
which is the site of our biggest river system and major farming lands.
Today the sinking continues,
and Australia is shaped like a giant shallow saucer.
If you look at a cross section from east to west
you can see that Lake Eyre, near the centre, is well below sea level.
This means that rain falling on much of the country drains inwards.
For millions of years clouds have dumped salt on the earth in rain.
Because of the shape of the country
the salt hasn't been able to get back to the sea,
it's had nowhere to go but into the ground.
The water that took it there forms a layer of salty underground water.
The top of that layer is called the water table.
Australia's native vegetation
has evolved in harmony with the water cycle.
Many trees and grasses are deep rooted,
so they can take up most of the rain that falls on the ground.
Because they grow all year there's no time that water isn't soaked up.
Not much water gets through to the groundwater below,
so the water table stays at pretty much the same level.
We've disrupted the water cycle in two ways,
by clearing vegetation,
and by pouring more water on the land when we irrigate for farming.
When European farmers cleared the land,
they planted shallow rooted crops that grew for only part of the year,
taking up a mere fraction of the water falling as rain.
The excess water moved down to the subsoil.
Eventually the water table rose, bringing salt to the surface.
This salt kills most plants, and makes it impossible to grow crops.
Without plant roots to hold the soil in place
the soil washes or blows away, terrible erosion results.
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One of the ways to reverse the problem is to plant deep rooted trees,
grasses, or crops that can suck up the water out of the ground.
This will lower the water table
and allow the salt to go back down into the ground,
below the root zone.
Irrigation presents another problem.
Many of our crops are grown using water that's poured onto the land.
Water seeps from irrigation channels
and from over watered crops into the water table.
It's important to add just enough water to the soil
to grow the plants, because any extra water
causes the water table to rise.
Every year Australia loses large areas of farming lands to salt.
If we don't turn this situation around quickly
we'll have difficulty feeding ourselves.
We need to change our land use patterns, and start gaining income
from the native plants that grow so well in our landscape.
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It's not only plants that are affected by salt.
Homes across Australia
are crumbling as salt eats away at the foundations and walls.
Houses built to last 25 years are surviving only two years.
By growing native trees and shrubs around homes,
and reducing the size of the lawn,
the need to water the garden can be reduced.
This stops water seeping into the water table.
Roads, too, crumble when attacked by salt.
Roads need four times the amount of maintenance
where water tables are high.
Playing fields, footpaths, swimming pools,
and the whole infrastructure of towns and cities, is damaged by salt.
We're all in this together.
Australia was made rich
from the agricultural exports of the last two Centuries.
The wealth in the towns and cities
flowed from government initiatives to clear and use the land.
History has caused the problem we face -- the future is up to us.
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