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1301.0 - Year Book Australia, 2003  
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Environmental impacts of agriculture

This article looks at the impact of agricultural activities on the Australian environment. In particular it examines land and water use, salinity and the adoption of various land management practices.

Land and water are essential for agricultural production. Since European settlement of Australia around 100 million hectares (ha) of forest and woodland have been cleared, mostly for agricultural production (NFI 1998), and land continues to be cleared for agriculture. Today around 456 million ha, or 59% of land in Australia, are used for agriculture, making it the dominant form of land use. Agriculture is also the largest consumer of water in Australia; in 1996-97 it accounted for 15,502 gigalitres or 70% of total water use (graph 16.4).

Graph - 16.4 Water use - 1996-97



The combined impacts of land and water use for agricultural production have been substantial. For example:
  • The removal of native vegetation and the introduction of exotic species have contributed to the extinction and decline of many species of Australian wildlife (Hamblin 2001).
  • The construction of dams and diversion of water from rivers have greatly altered water flows, reducing the amount of water flowing down rivers, and have changed the times of peak flows (ABS 2001b).
  • There has been a deterioration of soil and water quality in many areas.

Tables 16.5 and 16.6 show the area affected by three types of land degradation, as well as their estimated annual cost to agricultural production. Water quality is discussed in an article following Environment, and hence it will not be considered here.


16.5 EXTENT OF SALINITY, SODICITY AND ACIDITY - 2000

NSW
Vic.
Qld
SA
WA
Tas.
NT
ACT
Aust.
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha

Saline soils
89
287
62
472
2,169
26
-
-
3,206
Sodic soils
24,713
8,008
42,191
7,635
14,615
504
11,533
1
109,219
Acidic soils
4,095
2,754
6,192
20
4,602
677
2,973
4
21,317

Source: NLWRA 2002.


16.6 ANNUAL COST(a) TO AGRICULTURE OF SALINITY, SODICITY AND ACIDITY - 2000

NSW
Vic.
Qld
SA
WA
Tas.
NT
ACT
Aust.
$m
$m
$m
$m
$m
$m
$m
$m
$m

Saline soils
6.3
18.5
10.2
39.1
111.0
1.9
-
-
187.0
Sodic soils
280.3
342.5
180.3
126.4
89.7
12.3
3.0
-
1,034.6
Acidic soils
378.7
471.1
232.5
2.9
226.1
214.8
58.2
0.2
1,584.5
Combined cost(b)
624.1
757.4
392.9
162.0
341.6
220.3
61.1
0.2
2,559.5

(a) For a description of method used to derive see NLWRA 2002.
(b) Salinity, sodicity and acidity constraints often coincide, so the aggregate affect is less than sum of each constraint.

Source: NLWRA 2002.


Salinity, sodicity and acidity are all naturally occurring conditions of Australian soils, but these have been exacerbated by agricultural activities. Sodicity is a condition in which the sodium levels of the soil increase to the extent that they affect the physical properties of the soil. Sodic soils are prone to waterlogging. Acidity is a condition in which the concentration of hydrogen ions increases in the soil, which can cause the death of many plant species. Salinity is the build-up of salts in the soil, which also can kill plants.

In recent years salinity has gained prominence as a national environmental issue (see for example, MDBC 1999; Commonwealth of Australia 2000; NLWRA 2001). Early results from the 2001 ABS Agricultural Census show that around 26,000 farmers have salinity and/or are managing salinity on their properties. Table 16.7 shows that the proportion of farms reporting managing for salinity is greater than those reporting salinity, which is an indication that farmers are taking action to prevent or reduce the impact of salinity on agricultural land.


16.7 FARMERS REPORTING SALINITY OR SALINITY MANAGEMENT - 2000-01

Salinity
Salinity management
%
%

New South Wales
6
16
Victoria
11
20
Queensland
3
8
South Australia
13
21
Western Australia
37
37
Tasmania
5
8
Northern Territory
3
6
Australian Capital Territory
3
10
Australia
10
17

Source: ABS data available on request, preliminary data from the 2000-01 Agricultural Census.


Various activities have been used by farmers to manage or prevent salinity. The type of management adopted depends on the nature of the farm: cattle farmers adopt practices different from those used by orchardists. Three commonly promoted salinity management actions are the planting of lucerne, salt-tolerant pastures and trees. Others include pumping groundwater (to lower water tables) and digging drains, especially where the salinity is severe or high value crops (e.g. grapes) are involved.

The impacts of salinity extend beyond the agriculture sector. Roads, houses and water supply infrastructure can all be degraded by it. Over four states (New South Wales, Victoria, South Australia and Western Australia) the road, buildings and/or water supply infrastructure of 68 towns are at risk of damage from salinity. Biodiversity is also at risk through the loss and degradation of native vegetation. Across Australia around 630,000 ha of native vegetation and 80 wetlands, including wetlands of international importance, are at risk (NLWRA 2001).

One factor contributing to salinity is the rise in water tables due to increased amounts of water entering underground water bodies from irrigated land. This ultimately results in increased salt loads entering river systems. Reduced river flows, brought about by the construction of dams, weirs and water diversions, compound the problem as the flow is insufficient to dilute saline groundwater inflows (ABS 1996).

In recent years the area irrigated has increased substantially. Between 1990 and 2000 the area of irrigated land increased by more than half a million ha or 30%. The growth in irrigated area was greatest in Queensland, where an additional 236,000 ha (or 76%) were irrigated in 2000, compared to the area irrigated in 1990 (table 16.8).


16.8 IRRIGATED AREA

NSW
Vic.
Qld
SA
WA
Tas.
NT
ACT
Aust.
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha

1990
820
526
312
99
29
44
-
-
1,832
2000
944
626
548
159
39
62
6
-
2,384

Source: ABS 1991; ABS 2001a.


Irrigation can also cause a decline in soil structure and water quality, while the method of irrigation used influences the efficiency of water use and impact on the environment (Smith 1998). Impacts on water quality result from the high levels of fertiliser use in conjunction with some irrigation methods. Continued awareness of the need for greater efficiency and technological advancements can be expected to improve land management practices and reduce the decline in the health of land and water assets. For example, there has been a growth in the use of irrigation methods that are more efficient in terms of water delivery. In 2000 around 30% of irrigators reported using spray, micro spray or drip irrigation methods compared to 23% in 1990 (table 16.9).


16.9 IRRIGATION METHODS

NSW
Vic.
Qld
SA
WA
Tas.
NT
ACT
Aust.
%
%
%
%
%
%
%
%
%

1990

Spray method (excluding micro spray)
13
8
43
51
26
77
(a)
(a)
20
Drip or micro spray
1
2
4
13
18
3
(a)
(a)
3
Furrow or flood
84
90
46
33
48
11
(a)
(a)
74
Other
2
-
7
3
8
8
(a)
(a)
3
Irrigation methods reported(b)
100
100
100
100
100
100
(a)
(a)
100

2000

Spray method (excluding micro spray)
11
12
37
44
23
86
26
58
22
Drip or micro spray
3
5
8
33
38
6
68
42
8
Furrow or flood
85
82
54
21
35
8
-
-
70
Other
*1
*-
1
1
4
-
5
-
1
Irrigation methods reported(b)
100
100
100
100
100
100
100
100
100

(a) Not collected. (b) Percentages may not add to 100 due to rounding individual values.

Source: ABS 1991; ABS 2001a.


A number of factors affect the choice of irrigation methods used by farmers. These include cost, available technology, soil type, type of crop, climate and topography. In 1999-2000, furrow or flood irrigation methods were used for nearly 70% of all irrigated land. Flood irrigation, used on the majority of pastures and cereal crops, is popular probably because it is cheaper than the other methods available (Vic SoE 1991). If not managed correctly, furrow and flood irrigation can be highly inefficient and have detrimental effects on the water table and surrounding water bodies. However, for some crops, like rice, it is essential.

In 1999-2000, the spray method was used on approximately 22% of irrigated land. Spray irrigation has a higher installation cost and can be used for the application of slightly more saline water (generally from groundwater sources). The spray method produces less waterlogging than the flooding method, but is ineffective in high winds and can sometimes wash fertilisers from crops. Drip irrigation, also know as micro or trickle irrigation, is used on a smaller scale than other methods, and accounted for approximately 8% of irrigated land in 1999-2000. It is used on high value crops like grapes, citrus and tomatoes. Although the drip method is highly efficient, as evaporation losses are substantially reduced, it has higher installation and maintenance costs. Other technological innovations, such as laser levelling, have improved water efficiency (Smith 1998).

Many other land management practices can have environmental benefits. The planting of trees and fencing of native vegetation are two obvious examples (see ABS 2001a; Environment). These protect land and water quality as well as creating habitat for native animals and plants. Less obvious practices also help to make a difference. For example, stubble management methods can influence rates of soil erosion and the amount of organic matter retained in the soil (stubble is what remains of plants after crops have been harvested). In 2000-01 around 5 million ha of stubble were left intact (table 16.10). This stubble would have protected the soil from erosion by wind and rain.


16.10 USE OF STUBBLE MANAGEMENT PRACTICES - 2000-01

NSW
Vic.
Qld
SA
WA
Tas.
NT
ACT
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha
'000 ha

Most stubble removed by baling or heavy grazing
315
168
167
337
804
7
1
-
Stubble left intact (no cultivation)
862
257
592
545
2,756
3
-
-
Stubble ploughed into soil
1,600
487
740
511
357
13
-
-
Stubble removed by cool burn
745
248
60
263
393
4
-
-
Stubble removed by hot burn
841
466
23
389
469
3
-
-
Stubble mulched
378
290
279
467
105
2
-
-
All other methods
152
70
85
147
216
1
-
-
Total area treated
4,893
1,987
1,948
2,659
5,099
33
-
-

Source: Agricultural Commodities, Australia, 2000-01 (7121.0); ABS data available on request, preliminary data from the 2000-01 Agricultural Census.


The increasing use of more efficient irrigation methods, the implementation of salinity management activities and adoption of other land use practices are an indication that farmers are more aware of the environmental impact of their activities than in the past. Much of the impact on the environment is the result of historical land management decisions, and has taken decades to manifest. The impact of agriculture on the environment can be reduced and there are a number of community groups and government programs dedicated to achieving this. However, it is likely that the damage already done will take decades to abate and repair.

References

ABS (Australian Bureau of Statistics) 1991, Summary of Crops, Australia, cat. no. 7330.0, ABS, Canberra.

ABS 1996, Australian Agriculture and the Environment, cat. no. 4606.0, ABS, Canberra.

ABS 2000, Water Account for Australia, 1993-94 to 1996-97, cat. no. 4610.0, ABS, Canberra.

ABS 2001a, Agriculture Australia 1999-2000, cat. no. 7113.0, ABS, Canberra.

ABS 2001b, Australia's Environment: Issues and Trends, cat. no. 4613.0, ABS, Canberra.

ABS 2002, Australia's Environment: Issues and Trends, 2002, cat. no. 4613.0, ABS, Canberra.

AGO (Australian Greenhouse Office) 2001, Australian National Greenhouse Gas Inventory: Land Use Change and Forestry Sector 1990-1999, AGO, Canberra.

Commonwealth Department of the Environment and Heritage 2001, Australia State of the Environment Report 2001, CSIRO Publishing, Canberra.

Commonwealth of Australia 2000, National Action Plan for salinity and water quality (Information Booklet), Commonwealth of Australia, Canberra.

Hamblin A 2001, 'Land', Australia State of the Environment Report 2001 (Theme Report), CSIRO Publishing on behalf of the Department of Environment and Heritage, Canberra.

MDBC (Murray-Darling Basin Commission) 1999, The Salinity Audit of the Murray-Darling Basin - A 100 Year Perspective, MDBC, Canberra.

NFI (National Forest Inventory) 1998, Australia's State of the Forests Report, National Forest Inventory, Bureau of Rural Sciences, Canberra.

NLWRA (national Land and Water Resource Audit) 2001, Australian Dryland Salinity Assessment 2000, NLWRA, Canberra.

NLWRA 2002, Theme Six Report, NLWRA, Canberra.

Smith DI 1998, Water in Australia, Resources and Management, Oxford University Press, Melbourne.

Vic SoE (State of the Environment Committee) 1991, Agriculture and Victoria's Environment. Resource Report, Office of the Commissioner for the Environment, Melbourne.

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