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1370.0 - Measuring Australia's Progress, 2002  
Previous ISSUE Released at 11:30 AM (CANBERRA TIME) 19/06/2002   
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Contents >> The headline indicators >> Land degradation

Salinity, assets at risk in areas affected or with a high potential to develop salinity(a) - 2000
Graph - Salinity, assets at risk in areas affected or with a high potential to develop salinity(a) - 2000



This commentary focusses on a form of land degradation in Australia of particular concern: dryland salinity. At the end of the 1990s, about 5.7 million hectares (ha) of Australia were assessed as having a high potential to develop dryland salinity through shallow or rising watertables.

Our soil resources are an important natural asset, and their degradation is a significant concern to Australian farmers, governments and the general public. When left untreated, degraded soil reduces agricultural productivity, while salinity can damage buildings and infrastructure such as water pipes, roads and sewers. Degradation can also damage habitat for wildlife, kill micro-organisms that live in the soil, and harm the quality of our inland waters.

There are several forms of soil degradation in Australia. The natural acidity and salinity of some of our soils have been exacerbated by the way we use the land. Soil is eroded by wind and water or can be compacted. Ideally, the headline indicator would measure the land area affected by different types of degradation, and perhaps place a dollar value on the cost of degradation to agriculture, infrastructure and the environment. It might also measure whether the ways we use the land that lead to degradation are continuing. But many forms of degradation overlap one another, and there is no single measure of the area of degraded land in Australia. Moreover, some of these concerns (such as acidity) predominantly affect farm profits and so are primarily a financial concern to one part of the economy. (SEE FOOTNOTE 2)

We focus here on dryland salinity, the impacts of which are wider than lost agricultural production and include damage to water resources, biodiversity, pipelines, houses and roads. (SEE FOOTNOTE 1) Dryland salinity is a widespread form of soil degradation. It is linked to other forms of degradation such as soil erosion, is expensive to rectify and adversely affects agricultural or pastoral yields on about 3.3 million ha, (SEE FOOTNOTE 2) compared to 5.7 million ha judged to have a high potential to develop salinity. (SEE FOOTNOTE 1)

Some of the practices that have led to salinity have raised agricultural production and brought economic benefits. But, once established, salinity can have adverse effects on agriculture. The cost to agricultural productivity from salinity, estimated at $187m in 2000, is less than the cost of some other forms of degradation such as acidity, estimated at over $1b in 2000. But the cost of salinity goes further. (SEE FOOTNOTE 2) Salinity harms flora and fauna (primarily through loss of habitat), while saline water damages bitumen and concrete. (SEE FOOTNOTE 2) In 2000 some 1,600 km of rail, 19,900 km of roads and 68 towns were at risk of damage from salinity.

By 2050 some 5,100 km of roads, 67,400 km of rail and 219 towns are predicted to be at risk. A further 11,800 km of streams and lake perimeters are at risk now, a figure predicted to rise to 41,300 km by 2050. (SEE FOOTNOTE 1)


SALINITY

Australia's soils are old and shallow, and are susceptible to degradation by agricultural activities. Salinity occurs when the water table rises, bringing natural salts to the surface (in sufficient quantity, these salts are toxic to most plants). When trees or other deep-rooted vegetation are replaced with vegetation that uses less water, the water table may rise to cause dryland salinity. (If the water table rises through increased irrigation then irrigation salinity can occur. While irrigation salinity is well understood and managed, dryland salinity is more difficult to remedy. (SEE FOOTNOTE 1))

Analysts often discuss the on- and off-farm costs of degradation. The NLWRA estimates lost yield from dryland salinity to be about $190m in 2000. Off-farm costs are much more difficult to estimate, but the NLWRA suggests that by 2020 the annual costs of salinity arising from damaged infrastructure and declining water quality might amount to some $700m, without attempting to take account of any costs associated with damage to biodiversity. (SEE FOOTNOTE 2)


Areas with high potential to develop dryland salinity

High potential 2000
High potential 2050
State
ha
ha

NSW
181,000
1,300,000
Vic.
670,000
3,110,000
Qld
not assessed
3,100,000
SA
390,000
600,000
WA
4,363,000
8,800,000
Tas.
540,000
90,000
Other
minor
unknown
Aust.
5,658,000
17,000,000

Source: National Land and Water Resources Audit. (SEE FOOTNOTE 1)


SOME DIFFERENCES WITHIN AUSTRALIA

More than half of Australia's dryland salinity problems are predicted to occur in Western Australia (the south-west of the State in particular, a third of which is predicted to be at risk by 2050). (SEE FOOTNOTE 1) Much less land is currently affected by salinity in Victoria and Queensland, although in both States it could rise to over 3 million ha by 2050. Northern Australia has far less dryland salinity than temperate Australia, although experts believe it is not necessarily immune to the problem. (SEE FOOTNOTE 1)


FACTORS INFLUENCING CHANGE

Australia's soils are, in places, naturally saline. But salinity has been exacerbated by human activity, mainly agriculture. In some regions, problems originated over 100 years ago, from factors including excessive land clearance and large scale planting of pasture and crops that used relatively little water, pressures which remain today. In other areas salinity is coming to light after more recent land use changes. Because some of the problems began so long ago it is very unlikely that they can be repaired easily. Salinity problems, for instance, only become apparent after long time lags, often 100 years or more (depending on the soil type). (SEE FOOTNOTE 1)


LINKS TO OTHER DIMENSIONS OF PROGRESS

Some forms of agricultural production, land clearance and other factors such as the weather can all contribute to salinity. National income and wealth are also affected, not just through the loss of agricultural production but also because of damage to roads, rail and buildings (the severity of these effects varies considerably from region to region).

Salinity is a major threat to the health of many inland water systems. (Soil erosion, another form of degradation, can affect inland waters too, as well as estuaries and inshore marine environments, such as the Great Barrier Reef.)

Some 630,000 ha of native vegetation are at risk already from salinity, and this is predicted to rise to more than 2 million by 2050. (SEE FOOTNOTE 1) This degradation of both water and native vegetation will impact upon biodiversity in affected areas. In Western Australia for example, some 450 endemic plant species are threatened with extinction from salinity, (SEE FOOTNOTE 2) while Western Australia's Conservation and Land Management department has estimated that there has already been a 50% decline in waterbird species using wetlands in the Western Australian wheatbelt because of the death of vegetation due to salinity. (SEE FOOTNOTE 3)

Land clearance can lead to soil erosion and, when it results in a changing water balance, it leads to dryland salinity. Soil erosion, which is also linked to overgrazing from both livestock and invasive species such as rabbits and goats, can cause fine particle air pollution.

See also the commentaries National income, National wealth, Biodiversity, Inland waters, Land clearance, Invasive species, and Air quality.


IMPACTS OF SALINITY

For many farms affected, dryland salinity has meant loss of productivity and income. There are many off-farm impacts, the most significant of which appears to be the salinisation of rivers, which affects drinking and irrigation water (e.g. in Western Australia some surface water is already too saline for domestic use). (SEE FOOTNOTE 2)

Rising groundwater levels and the salt contained in the water damage road pavement, bitumen and concrete, while pipelines and other structures can also be affected. Wagga Wagga is one of the worst affected towns in New South Wales, where salinity is damaging roads, footpaths, parks, sewerage pipes, housing and industry. Other provincial towns in New South Wales and Victoria (such as Dubbo and Bendigo), as well as Western Sydney, are also affected. Predictions suggest that about 30 rural towns in Western Australia will be threatened by rising water tables by 2050. (SEE FOOTNOTE 1)

Dryland salinity also threatens biodiversity, through loss of habitat on land and in water. Areas near water are often worst affected because they occupy the lowest parts of the landscape where saline groundwater first reaches the surface. Areas of remnant and rehabilitated native vegetation are under threat in Western Australia, South Australia, New South Wales and Victoria. (SEE FOOTNOTE 1)


AUSTRALIA's RESPONSES TO SALINITY

Salinity is difficult to slow, halt or reverse. (SEE FOOTNOTE 1) In southern Australia key responses include improving the water balance (through farming techniques or revegetation), draining or intercepting and evaporating salty groundwater, or living with salinity and implementing saline agriculture and aquaculture. Different strategies suit different regions because salinity control invariably involves trade-offs between social, financial and environmental goals. And better understanding of salinity provides an opportunity for forestalling problems in northern Australia.


FOOTNOTES

1 National Land and Water Resources Audit (NLWRA) 2001, Australian Dryland Salinity Assessment 2000, NLWRA, Canberra. The NLWRA's salinity projections are based on a range of assumptions and data including an assumption of a continued rate of increase and no change to water balances.

2 National Land and Water Resources Audit (NLWRA) 2002, Australians and Natural Resource Management 2001, NLWRA, Canberra.

3 Dillon, B., Lewis, S., Holmes, A., McNamara, K., Burley, J., Hofman, H., Briggs, S., Lyon, P., Scott, A., Loan, L. and Saunders, D. 2001, Implications of Salinity for Biodiversity Conservation and Management, Task force report for ANZECC Standing Committee on Conservation.

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