Australia's Natural Resources

1997-2002 and beyond
National Land and Water Resources Audit, 2002

Key Findings—Land

Australia's agricultural landscapes have doubled in biological productivity since European settlement.

Agriculture in the higher rainfall, more fertile areas, primarily in the temperate coastal areas has, through addition of nutrients, use of legumes and irrigation, doubled the biological productivity of agricultural landscapes. The importance of further irrigation development, integrated farming systems and nutrient management cannot be underestimated if Australia is to increase its agricultural productivity.

Figure 9. The ratio of biological productivity under current agriculture to the pre-European landscape.

Cropping systems have delivered substantial gains in productivity.

Between 1982 and 1997, cereal grain yields per hectare have improved in most regions, notably where crops are diversified in regions of more reliable rainfall. Improved nutrient management, especially through the use of nitrogen-based fertilisers, has also contributed significantly.

Figure 10. Trends in wheat yields.

Animal husbandry and pasture management systems have also delivered increases in productivity.

During the last 25 years the number of dairy farms has declined consistently (from around 31 000 in 1974/75 to 14 000 in 1999/2000. The size of the national dairy herd has remained reasonably constant and the volume of milk production has more than doubled since 1980/81. Markets for product have also changed (e.g. a markedly increased proportion of milk produced now goes to manufacturing).

Figure 11. Trends in milk production, cow and farm numbers.

Figure 12. Trends in milk production in Australia (1974-1999).

Agriculture remains a significant component of the Australian economy.

Australian agriculture has a reputation for technical efficiency by international standards, 70% of the produce is exported and is extremely important to regional economies. A policy challenge will be to ensure it is increasingly based and be seen to be based on producing high quality commodities through the adoption of sustainable production systems that do not degrade the country's natural resource base. A good example is the continuous improvement in cotton industry practices to meet industry best practice standards.

Table 1. Level of adoption (%) of the industry's best management practice manual by regional cotton growers.

Audit stage	Australia total	Northern Region	Central Border Region	Southern Inland Region
Number of growers	1280	112	1006	162
No progress/don't know (%)	17	46	13	19
Progressing (%)	57	37	60	53
Audit ready (%)	12	12	11	16
Audited (%)	11	5	17	12
Best Management Practices Manual (2nd ed) (%)	70	54	79	26

Australia's soils are variable, but we now have much of the spatial information for their management.

Through the partnerships developed by the Audit, Australia's soil scientists have worked together to develop the Australian Soil Resource Information System. The compilation includes those soil attributes most commonly required to characterise, model or predict land resource processes that drive plant productivity, measure resource sustainability or control the rate of resource degradation.

Figure 13. Australian Soil Resources Information System.

Soil erosion is still occurring.

The types of erosion (Figure 19) and consequent management strategies vary in relative importance in differing parts of Australia (Figure 18).

Hillslope or sheetwash and rill erosion are dominant in tropical northern Australia.

Factors contributing to erosion rates include rainfall erosivity, vegetation cover, slope length and gradient and soil erodibility. Grazing is the main land use contributing to hillslope erosion and the key localities for improved management have been determined through the Audit's analysis. The greatest scope for reducing soil loss is through improved pasture and stock management aimed at maintaining adequate ground cover at all times, (including drought planning, off-stream watering, cell grazing and management of pasture species). These issues are of greatest importance in the northern Queensland grazing lands where the greatest increases in river, suspended sediment loads have occurred and where sediment delivery to the coast is more likely.

Figure 14. Current mean annual sheetwash and rill erosion rate (T/ha/year) (top) and present rate: modelled pre-European erosion ratio (bottom).

Gully erosion is a significant source of sediment delivered to streams, particularly in southern Australia.

Remedial works should focus on those gullies that continue to erode and either threaten structures or yield considerable amounts of sediment. Areas to target across Australia—under programs such as Landcare—are those with high levels of gully erosion (e.g. parts of the Burdekin and Fitzroy, much of the highlands and slopes of the Murray–Darling Basin and parts of the New South Wales north and south coasts). Low to moderate but extensive gully erosion occurs in south-west Western Australia. This is a significant erosion process for the region considering the estimated low natural rates of erosion.

Figure 15. Area of moderate and high gully density in river basin regions.

Figure 16. Area of moderate and high gully density in river basins containing intensive agriculture.

Riverbank erosion is widespread in agricultural landscapes.

Sixty-five percent or about 120 000 km of the river length assessed is cleared of riparian vegetation. At a conservative cost of $10 000 per kilometre for fencing and replanting, rehabilitation would cost about $1.2 billion. This high cost of repair demonstrates the imperative for encouraging conservation in those areas where riparian vegetation is relatively intact (e.g. by encouraging best practice) and, if necessary, backed up by planning controls. For that component of funds under Rivercare allocated to repair rather than protection, this analysis provides estimates of the relative proportions that might need to be invested in each region.

Figure 17. Estimated proportion of native vegetation removed along stream banks in river basins.

The source of sediment delivered to streams varies across Australia.

Allocations for soil erosion control works under the National Action Plan need to be responsive to the varied sources of stream sediments. They will vary in relative proportions for differing regions:
- in far North and North Queensland, much of the available resources would be most effectively allocated to minimise hillslope erosion;
- in Tasmania the majority of works to minimise sediment delivery to streams would be most effectively directed to riparian area re-vegetation.

Figure 18. Reporting regions for erosion and sediment transport assessment.

Figure 19. Estimated amounts of sediment supplied to streams by each erosion process.

Soil erosion varies in locality and type within any basin.

On average across agricultural Australia 90% of the erosion comes from 20% of the area. The mix of soil erosion types also varies within each basin. The Audit assessments need to be used at a basin scale as well as within the broader regional context to determine priorities for works and activities and to set targets (e.g. the relative importance in all subcatchments of bank, hillslope and gully erosion can be determined using information from Figure 20).

Figure 20. Sediment sources in the Fitzroy basin, Queensland. Bank erosion loss is relatively low, there is moderate loss from gully erosion, but there are some areas of high sediment load from hillslope erosion, particularly near the coast.

Nutrients are being lost as a result of some agricultural practices.

Nearly 19 000 tons of phosphorus and 141 000 tons of nitrogen are travelling down Australia's rivers to the estuaries and, in some cases, to near-shore marine environments each year. Yet, much of the land is in negative nutrient balance, with inputs less than exports (Figure 21).
Significant excesses or positive balances in some areas, suggest potential over-investment in phosphatic fertilisers.

Figure 21. Farm-gate phosphorus balance (kg P/ha) with all land use combined (averaged 1992-96) over the intensive land use zone.

Partnerships with agribusiness provide the key to better nutrient management on-farm.

The analysis across all key nutrients was based on on-farm soil testing linked to an understanding of soil properties and production rates. This analysis has demonstrated that Australian agriculture needs to closely examine and finetune fertiliser use and become more skilled in managing legume regimes to achieve optimum plant productivity. These could both reduce input costs and minimise negative impacts to rivers and estuaries (Figure 22).

Figure 22. Conceptual responses of landscape production and environmental cost to nutrient inputs.

Attention to soil management practices to minimise soil acidity needs to be coupled with nutrient management.

In the more intensive agricultural areas, the use of nitrogen-fixing legumes and nitrogenous fertilisers have become common. This has improved soil fertility and plant productivity. Excess soil nitrogen can lead to soil acidification. This looms as a significant soil degradation issue, already affecting up to 25 million hectares, with more to come. By working with agribusiness and its on-farm soil testing activities we will be able to track progress in addressing this issue.

Figure 23. Topsoil pH showing the interpolated surface for measured and derived soil pH (measured in 0.1M CaC12) based on the collation of soil data obtained from agribusiness records of on-farm soil testing.

Australia can now set targets for action on soil acidity.

Information on soil properties detailed in the Australian Soil Resources Information System and land use mapping were used to identify the levels of lime required across agricultural Australia to mitigate against the acidifying effects of current farming systems. These targets will assist agribusiness and farmers in their soil management activities (e.g. approximately 12 and 66 million tonnes of lime are required to adjust existing acidic soils to a typical agricultural production pH of 4.8 and 5.5 respectively). Maintaining soil pH values at 4.8 and 5.5 requires ranges of 0.6 - 3.1 million tonnes and 2.4 - 12.3 million tonnes of lime each year respectively. These estimates for lime application are based on the data for estimated years to reach soil pH* 4.8 at minimum rates of acidification (Figure 24) and a companion data set estimating maximum rates of acidification.

Figure 24. Modelled estimated years for Australia's agricultural soils (pH > 4.8) to reach pH 4.8 at minimum rates of acidity development, and in the absence of lime applications.

Salinity will continue to degrade rural and urban landscapes.

Changes in water balances following tree clearing and loss of perennial grasses, loss of vigour in the remaining and substitute vegetation, and changes in rainfall patterns have all served to increase the amount of water entering watertables. This has raised groundwater levels and brought salt into the plant root zone. Modelling and mapping has determined the location and extent, at approximately 5.7 million hectares of Australia currently at risk of dryland salinity. Predictive modelling suggests that in fifty years time the at-risk area could increase to 17 million hectares. The condition of habitats is declining as a result of increasing pressures of salinity and changes in hydrological regimes. The risk in Victoria is shown below as an example. With this information natural resource managers can target their works, activities and protective measures as part of the National Action Plan for Salinity and Water Quality.

Figure 25. There is a considerable risk of increased salinity in parts of Australia over the next 50 years, as shown in the shaded areas forecast for Victoria.

Northern Australia presents opportunities to avoid the dryland salinity problems of temperate Australia.

Hazard assessment has confirmed that large areas of the tropics and subtropics, particularly in Queensland, have a significant potential salinity problem if changes in water balance occur through clearing. Vegetation management policies to retain native vegetation could ensure that salinity does not develop and are a cost-effective way to minimise the onset of salinity. Queensland agencies are building on this assessment at a finer scale to determine the most appropriate management responses and key areas for protective management of water balance.

Figure 26. Dryland salinity hazard in Queensland 2050.

The mapping of groundwater flow systems provides a basis for defining effective management options and tracking progress.

The responsiveness of groundwater systems to change will dictate what can be effectively achieved within reasonable time frames through groundwater recharge and discharge management which involves minimising the amount of rainfall that drains past the root zone of the vegetation into the groundwater (thereby recharging groundwater levels) while learning to manage any areas where groundwater is being discharged from the soil surface. Options for recharge management, engineering watertable management and use of saline resources have been defined for each of Australia's 12 groundwater flow systems and provide a basis for more intensive local scale mapping. This understanding of hydrogeology, salt and water balance provides a basis for monitoring the activities funded under the National Action Plan for Salinity and Water Quality.

Figure 27. Distribution of groundwater flow systems across Australia.

Increasing salinity presents a risk to public infrastructure.

By understanding the current extent of salinity and its likely extent in 2050, we can implement strategic approaches to minimise the impact on infrastructure. Estimates suggest up to 67 400 km of road, 5 100 km of railway, 41 300 km of streams, two million hectares of native vegetation and the infrastructure of 200 towns could be at risk over the next 50 years. Public costs from the effects on railways, roads and towns could approach $500 million annually over the next 20 years. Planning and implementing works in priority areas will reduce the risk of incurring these costs.

Table 2. Summary of Australian assets at risk from shallow water tables or high salinity hazard.

Asset	2000	2050
Agricultural land (ha)^{*, 1}	4 650 000	13 660 000
Remnant and planted perennial vegetation (ha)^{*, 2, 5}	631 000	2 020 000
Lengths of streams & lake perimeters (km)^{*, 2}	11 800	41 300
Railway (km)²	1 600	5 100
Roads (km)²	19 900	67 400
Towns (number)³	68	219
Important wetlands (number)^{*, 1, 4}	80	130

* uncosted effects
1 data from all States, Queensland only for 2050
2 data from Western Australia, South Australia, Victoria and New South Wales (Queensland only for 2050)
3 data from Western Australia, South Australia, Victoria and New South Wales
4 including Ramsar wetlands
5 much of the remnant and perennial vegetation reported for each State occurs on agricultural lands

Salinity management activities will deliver benefits both on and off farm.

The Audit's assessment of current salinity extent and future salinity hazard coupled with its assessment of the value of infrastructure at risk and the current and future cost to production on-farm provides a basis for determining the relative levels of benefit that are likely to be achieved through investment under the National Action Plan for Salinity and Water Quality.

Figure 28. Present values of increases in dryland salinity induced costs from 2000 to 2020, determined at a 5% discount rate.

Soil acidity is Australia's major on-farm soil management and productivity issue.

Dryland salinity is a significant source of degradation in many areas. However, from an Australia-wide perspective, the economic impact of soil acidity on-farm is five to six times greater than that of dryland salinity. Based on yield gap calculations, a gross benefit of $1.5 billion, equivalent to 24% of profit at full equity, could be secured by addressing acidity. By comparison, salinity results in losses of $200 million on-farm (3% profit at full equity), and is not always treatable. Sodicity, an inherent soil characteristic, was also included in the Audit assessments to demonstrate the relative biophysical limitations to agricultural productivity.

Figure 29. Estimated national gross benefits (additional agricultural profit) attainable from treatment of soil acidity, soil salinity and soil sodicity ($m).

Australia's rangelands provide opportunities for protective management.

Relatively little clearing has occurred in Australia's rangelands-constituting approximately 75% of the country's land area. Protective management to maintain biodiversity values is likely to be cost-effective in these comparatively intact areas of native vegetation.

Figure 30. Current extent of native vegetation by subregion.

Fire is a tool and an imperative for improved management of Australia's rangelands.

Determining and then applying appropriate fire regimes within a multi-objective context to Australia's rangelands is a major challenge.

Figure 31. Remotely sensed image showing fire frequency in the Kimberley.

Understanding total grazing density is part of the information needed for managing Australia's rangelands.

Total grazing density is relatively low and variable across Australia's rangelands. Land condition is improving particularly with reductions in rabbit populations following the spread of calicivirus.

Figure 32. Grazing density (sheep + cattle + kangaroos + goats + rabbits) in the rangelands. Total grazing density was calculated using annual data on sheep and cattle and decadal data on macropods and feral animals (goats and rabbits). Each class of animal was converted to dry sheep equivalents in order to allow total grazing density to be calculated.

Predictive and protective management is essential for Australia's rangelands.

Because of the vast areas and low value per hectare, degradation is potentially much more difficult to reverse in Australia's rangelands. Management should be strongly oriented to minimise any degradation impacts. Working within an understanding of climate variability is a particularly important aspect of decision making (e.g. a wide variation in the feed quantity and vigour can be available in two overlapping twelve-month periods across Australia's rangelands as estimated by the normalised difference vegetation index [Figure 33]).

Figure 33. Minimum greenness (June 1999 to July 2000; top) and maximum greenness (January 2000 to December 2000; bottom) as estimated by the Normalised Difference Vegetation Index.

Management of Australia's rangelands can be improved through coordinated approaches.

Current monitoring is largely oriented to the 'pastoral estate' and prior to Audit activities was uncoordinated between the States and Northern Territory. Improved information capabilities based on Australia-wide coordinated and standardised data sets with broader environmental parameters would be of advantage to management decision making, particularly from a multiple-use perspective.

Figure 34. Components of a comprehensive rangeland monitoring system and associated information products.

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