As for our land, well we have done our best to stuff it up. Mostly through ignorance we have attempted to turn a fragile and ancient landscape into European farming pastures and the impact has been dramatic. The ability of our land to function properly has been affected. Our land has been degraded.
What is Land Degradation?
Damaging changes to our land happen because of how we use and develop it. These changes are on top of what occurs naturally, are unwanted and mostly brought on by us. Our land suffers reduced production capacity and reduced economic value.
Ecosystems continue to function but have a greatly reduced capacity to provide crops, food, grazing and habitat for native plants and animals.
More than half of Australia’s agricultural land is considered ‘severely degraded.’ Rising salinity (due to over- irrigation and loss of native vegetation) costs Australia hundreds of millions in lost agricultural production every year, and the direct costs of salinity are heading the same direction. Salinity kills farmland, spoils drinking water and destroys natural ecosystems.
Former Murray Darling Basin Commission chair Professor John Lovering reckons that parts of our country are already stuffed and that salinity could not be beaten. Australia had to learn to live with it.
‘This is not a copout but a recognition that the scale of the problem is so large that we can’t turn back the clock,’ he said.
The bad news, it seems, is that so many of the things that we do everyday cause pollution. While poor farming and land management practices are difficult to turn back.
There is good news. In many farming communities, the replanting of native forests are bringing wildlife back. Trees planted along riverbanks are reducing erosion, and vast plantings of strategically placed saltbush are drawing salt from the soil. Reduced irrigation is leaving salt deep in the soil rather than bringing it to the surface where it kills crops.
Cool Australia has planted 20,000 trees on degraded farmland in the Habitat 141 project in Western Victoria.
Salinity has been called Australia’s silent flood. There has even been a documentary series made by the ABC called – you’ll never guess – Salinity, Australia’s Silent Flood.
Here are some questions that have been answered by some very clever experts in the area of salinity.
How did so much salt get from the oceans and seas onto the land?
We think most of it has come in from wind blown accession from the oceans. Something like 20 to 200 kilograms per hectare per year. Because Australia wasn’t swept clean by the ice sheets 10,000 years ago like in the northern hemisphere, we’ve had soils that have been accumulating salts for hundreds of thousands of years. If you do your sums you can soon account for a lot of the salt that’s in the Australian landscape simply from wind blown accession from the oceans. – Dr David Chittleborough, Adelaide University
How much salt is in Australia’s landscape?
Salt has been accumulating at a rate of about 20 kilograms per hectare for probably 30 to 100,000 years. In areas like the south west of Western Australia there is probably 5,000 to 10,000 tonnes of salt stored under every hectare. – Richard George, Agriculture WA
Is the salt in the ground the same as the salt I put on my fish and chips?
Yes. Principally its sodium chloride, something you put on your food every night or perhaps not if you are health conscious. It’s principally sodium chloride, there are other ones but that’s principally the one. – Dr David Chittleborough, Adelaide University
New Zealand has no problems with salinity because its rivers take the salt off the land and back out to sea. Why doesn’t that happen here?
Australia is so different from any other land. Rivers normally build on high ground and run briskly down slopes and disappear into the sea. When rivers behave like that around the coastal parts of Australia any excess salts that get into river systems is carried back into the sea. However most of our major rivers rise on the western flanks of the Great Dividing Range and they don’t run briskly down slopes and into the sea, they run into a very flat landscape. In the case of the Murray Darling it’s our major river system and it travels mainly westward and then it has one very small exit to the sea. So you’ve got inward flowing rivers in a continent with a sunken centre. You end up with a very flat land, it gets flatter and flatter retaining its sediment and it becomes a land of flood plains and at the same time of course it is retaining its salt. – Mary White, Palaeobotanist
How did Australian plants deal with this salt prior to European colonisation?
Prior to clearing nearly all rainfall would have gone into the ground and been used by plants and trees. The roots of some trees go down 30 to 40 metres. They are very hungry for water so they don’t let anything drain through the root chain. Around about a cup of water per square metre was all that ever made it through and that would have been on an occasional basis. The salt was still there but it was kept at a depth where it wasn’t a great problem. – Richard George, Agriculture Western Australia
Why has salinity become such a problem in Australia recently?
What we have done since European settlement is we’ve actually changed profoundly the water balance in the landscape. The vegetation, the woody trees and shrubs and perennial grasses had come to one way of living with the salt. What they have done is they have used all the water possible through evaporation or through runoff and so very little water in the native vegetation moved past the root zone. Now when we came along we tended to take out the deep-rooted trees and shrubs and perennial native grasses and now a great deal more water dribbles past the roots zones of our pastures and our annual crops.
To give you some indication of the size of that, in terms of numbers, before we interfered with the system the amount of water that dribbled beneath or leaked beneath the native root system was between half a millimetre and maybe five millimetres a year. Now, under our agricultural system, under our annual crops and annual pastures, that number can be as high as 50 or in some cases even as high as 150 millimetres, so we have seen a 10 fold change in the amount of water that is being pushed into the landscape. So if you can push water into the landscape in large rate compared to the small rate it can get out, it must fill up and bring the salt into our rivers and into the lower parts of the landscape as you see behind me here.– Dr John Williams, CSIRO Land & Water
When will Australia’s hydrology again be balanced?
On a broad scale approach current estimates are maybe between 100 and 200 years. Obviously in certain catchments they may achieve that early on and some may take a lot longer but broad scale estimates are 100 to 200 years. – Hugh Middlemis, Institution of Engineers
When did science make the link between land clearing and dryland salinity?
The first evidence in Western Australia of salinisation as a consequence of land clearance goes back to the 1890s when railway engineers started to notice that their water supplies and dams they had developed for the rail had been salinising, and they began to link it causally to land clearance. The landmark scientific paper that established it beyond all reasonable doubt of that link between land clearing and salinisation was published in 1925 – so for 75 years we have known what causes salinity. Whether we have heeded that advice is another question. – Dr Tom Hatton, CSIRO Land & Water
What causes rivers to go salty?
The salt is getting into the water through two main mechanisms. It is coming from overland flow where we’ve got rain falling on salt affected land, and it’s also coming into the rivers from groundwater – especially where the rivers are low. For instance, when the Darling is especially low, the groundwater starts to flow in and that puts salty water into the river. – Professor Peter Cullen, Co-operative Research Centre for Freshwater Ecology
Why does irrigation cause salinity?
When we decided to move to irrigation, not only did we take the deep-rooted trees and shrubs out we, also allowed more water to leak below the root zone. No matter how well and how skilfully we irrigate it’s very hard to stop water moving past the root zone of our irrigated crops – whether they are fruit trees or rice paddies. Under irrigation we have increased it not 10 fold but sometimes 100 fold, and thus we have all the driving force for irrigated salinisation. – Dr John Williams, CSIRO Land & Water
How does salinisation affect fish, birds and other species that rely on wetlands?
Too much salt in our rivers is just like another pollutant such as oil or pesticides. As we increase that level of pollution in our rivers the species retreat more and more into smaller areas and refuges away from salinity. A good example is the Macquarie Marshes – a wonderful wetland where the salinity level predicted to hit the marshes in 30 years is 1500 EC units, which is the level at which we are set to lose whole plant communities. Fish species are in real trouble, and invertebrates are well and truly disappeared in many of the river systems. – Dr Stuart Blanch, Australian Conservation Foundation
What does salinity do to agricultural crops?
What we are doing essentially is making the plant suffer a drought. The salt has an osmotic effect. By osmotic, I mean it dries out the water in terms of the plant’s ability to extract it. Now the plant essentially suffers a drought under salting. Also the excess amount of sodium causes an imbalance in the other nutrients in the plant needs such that the plant suffers nutrient deficiency as well. – John Williams, CSIRO Land & Water