Biodiversity publications archive

Landscape planning for biodiversity conservation in agricultural regions: A case study from the Wheatbelt of Western Australia

Biodiversity Technical Paper, No. 2
Robert J. Lambeck, CSIRO Division of Wildlife and Ecology
Commonwealth of Australia, 1999
ISBN 0 6422 1423 9

Chapter 3 - Integrating biodiversity conservation with other land uses (continued)

3.5 Land uses and land suitability

For each of the nominated issues the stakeholders were required to identify the range of relevant land uses and to specify the suitability/capability of different land units for those uses.

3.5.1 Biodiversity land uses

The ongoing decline in abundance of species that require large patches of habitat indicates that the existing remnant vegetation is inadequate for retaining the plants and animals in the catchment. It was therefore considered necessary to not only protect the existing remnant vegetation but also to increase the amount of available habitat. Because all stakeholders involved in the current study agreed that the existing remnant vegetation in the catchment is inadequate there was no need to specifically deal with issues of further clearing. Consequently all existing native vegetation was considered suitable for retention. Figure 12 shows the current distribution of remnant vegetation in the Wallatin Catchment.

Figure 12: The distribution of remnant vegetation in the Wallatin Catchment.

Figure 12: The distribution of remnant vegetation in the Wallatin Catchment.

Note: Data courtesy of M.G.Brooker (CSIRO Wildlife and Ecology) and the Spatial Resource Information Group, Agriculture Western Australia

Source: (Beeston et al. 1994)

The land uses that were considered appropriate for addressing nature conservation objectives in the Wallatin Catchment were therefore considered to be:

Because it is yet to be demonstrated whether it is possible to reconstruct all of the complexity of natural habitat, it was considered that habitat reconstruction should initially be based on the re-establishment of the dominant species which make up the main vegetation types that occur in the catchment. Land suitability for re-establishing these different habitat types was derived from a knowledge of the relationships between vegetation assemblages and landforms (Beard 1983). Maps of these landform types (Figure 13) enable an assessment of the suitability of different parts of the landscape for different reconstruction actions. The landform types which occur in the catchment and their corresponding vegetation types are listed in Table 3.

Figure 13: The distribution of landforms in the Wallatin Catchment.

Figure 13: The distribution of landforms in the Wallatin Catchment.

Source: Data from McArthur (1992)provided by the Spatial Resource Information Group, Agriculture Western Australia.

Table 3: Land suitability for addressing biodiversity objectives. Landform units are those described in Figure 2 (Section 1.2.2)
Land unit Land use
Existing public reserve Remnant protection
Existing private remnants Remnant protection
Landforms
  Ulva Heath
  Booraan Wandoo woodland
  Collgar Mallee
  Merredin/Belka Salmon gum/gimlet woodland
  Danberrin York gum woodland
  Rock Jam wattle/York gum woodland
Gutless sands Banksia woodlands

The focal species approach described in Section 2.5 provided guidelines for the minimum area of each vegetation type that is required to meet the needs of the most demanding species that utilise that patch type. A Geographic Information System (GIS) was used to identify all existing patches which were less than the desired size and to identify suitable adjoining areas that would need to be added to these patches in order to meet the specified minimum sizes (See Figure 11 in Chapter 2).

3.5.2 Agricultural land uses

Land capability assessment has been the basis for agricultural planning since the wheatbelt was first cleared. Lower lying soils supporting York gum and salmon gum woodlands were recognised at an early stage as being the most productive for growing wheat (Burvill 1979). Other soil types, such as the upland sandy soils, were originally considered less suitable for cropping until it was realised that the addition of trace elements improved their capability.

Soil types for the study area and their relationships with landform units were described by Hawkins (1990). The classification produced by Hawkins was used by farmers in the catchment to produce soil maps for each farm. These maps were digitised and incorporated into the regional Agriculture Western Australia GIS at Merredin (Figure 14). The suitability of these soil types for agriculture, as perceived by the landholders, is shown in Table 4.

Figure 14: Soil map of the Wallatin Catchment.

Figure 14: Soil map of the Wallatin Catchment.

Note: Soil types match those listed in Table 4.

Source: Modified from data provided by Agriculture Western Australia.

Table 4: Suitability of different soil types for agricultural land uses. Terminology follows Hawkins (1990)
  Land unit Hawkins classification Land use
Ulva Deep yellow sand Sa Lupins/Cereals
Pasture/Cereals
Gravelly uplands Sg Lupins/Cereals
Gravelly uplands St Lupins/Cereals
Pasture/Cereals
Gravelly sands Sgt Pasture/Cereals
Pasture/Pasture/Cereals
Sandy loams Sp Lupins/Cereals
Pasture/Cereals
Booraan Breakaways Bd Revegetation with perennial vegetation
Shallow clays Bgc Revegetation with perennial vegetation
White gum soils Be Pasture/Cereals
Collgar Shallow gravelly duplex Dug Pulses/Cereals
Deep duplex Dud Lupins/Cereals
White gum duplex Duw Pasture/Cereals
Shallow grey duplex Dusg Pulses/Cereals
Merredin/Belka Salmon gum/gimlet BE Pasture/Cereals
Pulses/Cereals/Cereals
Pulses/Cereals/Canola/Cereals
Salmon gum/gimlet soils Msl Pasture/Cereals
Pulses/Cereals/Canola/Cereals
Pulses/Cereals/Canola/Cereals/Pasture
Salmon gum/gimlet soils Mgc Pasture/Cereals
Pulses/Cereals/Cereals
Pulses/Cereals/Canola/Cereals
Danberrin York/Jam Y/J Pulses/Cereals/Pasture/Cereals
York Y Pulses/Cereals/Pasture/Pasture/Cereals
Jam/Rock J/R Revegetation with perennial vegetation
Rock     Revegetation with perennial vegetation

The land uses nominated by the farmers in this exercise tend to reflect traditional cropping rotations based on cereals, pulses and pasture. Annual rainfall is insufficient to support a timber industry based on Tasmanian blue gums (Eucalyptus globulus) as is the case in the wetter areas to the south-west. Other timber species such as maritime pine (Pinus pinaster) and eucalypt mallees for producing oil may be potential crops in the future. The recent nomination of this catchment as a 'Focus Catchment' in the State Government Salinity Action Statement (Government of Western Australia 1996) may provide an impetus for exploring a wider range of agricultural land-use options.

3.5.3 Hydrological land uses

The increase in land and stream salinisation throughout the south-west of Western Australia is caused by increasing groundwater discharge as a result of the clearing of native vegetation (Salama et al. 1993, 1994). Possible responses to this increased discharge include the re-establishment of woody perennial vegetation, development of high water-use crops, and implementation of drainage strategies. The nature of the response will depend on the level of understanding of the factors that influence catchment hydrology.

The Wallatin Catchment represents a relatively complex hydrological system. It is bordered in the higher parts of the landscape by lateritic duricrust and granitic outcrops. The remainder of the catchment is dissected by dolerite dykes with associated basement highs, quartz veins and faults (Salama et al. 1993). Thin sedimentary deposits occur throughout the catchment, particularly in the alluvial channels. Each of these features differs in its recharge and discharge characteristics and in its influence on salt storage.

Three different patterns of recharge can be identified within the catchment (Figure 15).

The distribution of soluble salts varies throughout the catchment. Total soluble salt levels are highest in the area covered by thin sediments and in the channel deposits. Salt storage increases from divide to valley floor with higher salt storage occurring in the relict channels and palaeochannels. Salinity stores can vary from 10 t/ha in the divides to 350 t/ha in the valleys with levels as high as 4000 t/ha upstream of geological structures (Salama et al. 1993).

There are two revegetation responses that can be adopted in the face of this complexity. The first of these is to acquire a detailed knowledge of recharge and discharge characteristics and strategically target revegetation to those areas where it will have the greatest impact. In situations where this knowledge is not available, an alternative response is to distribute revegetation throughout the catchment in order to intercept water regardless of where it falls. On the basis of the hydrological characteristics of the Wallatin Catchment a number of broad hydrological 'land uses' were identified. These ranged from dense planting of perennial species, through alleys of perennial tree or shrub species interspersed with agricultural rotations and drains, to scattered plantings of perennial species around local recharge features. The circumstances under which each of these options is most appropriate are listed in Table 5.

Figure 15: Long-term water level trends.

Figure 15: Long-term water level trends.

Note: a) monotonically rising; b) continuously rising; c) seasonally fluctuating

Source: Modified from Salama et al. (1991).

Table 5: Suitability of different land units for hydrological land uses
  Land unit Land use options
Ulva   Revegetation to deep rooted perennial vegetation
Gravelly uplands (Sg) Plantation perennials
Gravelly uplands (St) Plantation perennials
Booraan   Alleys of deep-rooted perennials planted along the contour, interspersed with deep-rooted annuals
Breakaways (Bd) Revegetation with perennial species
Shallow clays (Bgc) Revegetation with perennial species
Collgar   Alleys of deep-rooted perennials planted along the contour, interspersed with deep-rooted annuals
Shallow gravelly duplex (Dug) Alley farming with drains
Deep duplex (Dud) Alley farming with drains
White gum duplex (Duw) Alley farming with drains
Shallow grey duplex (Dusg)  
Merredin/Belka   Cropping, interspersed with perennials around recharge features
Danberrin (York/Jam)   Revegetation for hydrology
  Deep-rooted perennials planted along the contour, interspersed with deep-rooted annuals
Jam/Rock Revegtation with perennial species
Rock   Alleys of deep-rooted perennials planted along the contour, interspersed with deep-rooted annuals where soils are sufficiently deep

3.5.4 Interactions between land uses

As outlined in the previous sections, the objectives of any land-allocation exercise are most likely to be achieved where there is a good understanding of the suitability of different parts of the landscape for different land uses. In many instances, however, a given land unit may be suitable for more than one use. Where this is the case, it will be necessary to either (i) allocate the land unit to one or other of the competing uses or (ii) seek ways to integrate the uses so that the same land unit can be managed for both objectives simultaneously. Where the first option is taken it is likely that one objective will suffer at the expense of the other with the risk that one may not be met. In the second scenario neither objective may attain maximum performance but an adequate result may be achieved for both.

By comparing the land uses which contribute to nature conservation, agriculture and hydrology objectives, it was possible to identify new combinations of land uses which address two or more objectives simultaneously. For example, the requirement for dense plantings of perennial species on some recharge areas to manage hydrology can be combined with a nature conservation objective by selecting native plants of local provenance which may provide resources required by the native biota. Alternatively, hydrological and production goals can be merged by planting timber producing species or oil mallees in areas where they contribute most to managing recharge. This could be achieved either through block plantings of timber species or by alley farming. Both of these strategies can bring further benefits including shelter for stock and reduced wind and water erosion.

Table 6 lists composite land uses which were identified by looking for correspondence between the recommended uses for nature conservation, hydrology and agriculture objectives. Such melding of land uses can only be carried out where the various stakeholders acknowledge mutual benefit. If such an agreement cannot be reached, then the individual land uses should be used in the planning exercise. By using decision support tools such as LUPIS it is possible to explore the implications of combined versus separate guidelines by including both the original individual guidelines as well as the combined ones and exploring the outcomes that result from changing the relative weightings applied to each. Failure to recognise these potential interactions could result in land uses being considered to be competing and mutually exclusive when they are in fact compatible, if not complementary.

Table 6: Compatible land uses which can potentially be combined into new composite uses.
Land unit Compatible land uses Composite land uses
Ulva
Deep yellow sand (Sa) Deep rooted perennial vegetation  
Lupin/cereal rotation Lupin/cereal rotation between alleys of deep rooted perennials
Pasture/cereal rotation Pasture/cereal rotation between alleys of deep rooted perennials
Gravelly uplands (Sg) Deep rooted perennial vegetation  
Lupin/cereal rotation Lupin/cereal rotation between alleys of deep rooted perennials
Gravelly uplands (St) Deep rooted perennial vegetation  
Lupin/cereal rotation Lupin/cereal rotation between alleys of deep rooted perennials
Pasture/cereal rotation Pasture/cereal rotation between alleys of deep rooted perennials
Gutless sands (Sgt) Deep rooted perennial vegetation  
Revegetation with Banksia woodland Banksia revegetation
Pasture/cereal rotation Pasture/cereal rotation between alleys of deep rooted perennials
Pasture/pasture/cereal rotation Pasture/pasture/cereal rotation between alleys of deep rooted perennials
Sandy loams (Sp) Deep rooted perennial vegetation  
Lupin/cereal rotation Lupin/cereal rotation between alleys of deep rooted perennials
Pasture/cereal rotation Pasture/cereal rotation between alleys of deep rooted perennials
Booraan
Breakaways (Bd) Revegetation with perennial vegetation  
Revegetation with Wandoo woodland spp. Wandoo revegetation
Shallow clays (Bgc) Revegetation with perennial vegetation  
Revegetation with Wandoo woodland spp. Wandoo revegetation
White gum soils (Be) Alleys of deep rooted perennials  
Pasture/cereal rotation Pasture/cereal rotation between alleys of deep rooted perennials
Collgar
Shallow gravelly duplex (Dug) Alley farming with drains  
Pulse/cereal rotation Pulse/cereal rotation with drains and alleys of deep rooted perennials
Deep duplex (Dud) Alley farming with drains  
Lupin/cereals rotation Lupin/cereals rotation with drains and alleys of deep rooted perennials
White gum duplex (Duw) Alley farming with drains  
Pasture/cereal rotation Pasture/cereal rotation with drains and alleys of deep rooted perennials
Shallow grey duplex (Dusg) Alley farming with drains  
Pulses/cereal rotation Pulses/cereal rotation with drains and alleys of deep rooted perennials
Merredin
Salmon gum/gimlet soils (Msl) Perennials around recharge features  
Pasture/cereal rotation Pasture/cereal rotation with perennials around recharge features
Pulses/cereals/canola/cereals rotation Pulses/cereals/canola/cereals rotation with perennials around recharge features
Pulses/cereals/canola/cereals/pasture rotation Pulses/cereal/canola/cereals/pasture rotation with perennials around recharge features
Salmon gum/gimlet soils (Mgc) Perennials around recharge features  
Pasture/cereal rotation Pasture/cereal rotation with perennials around recharge features
Pulses/cereals/cereals rotation Pulses/cereals/cereals rotation with perennials around recharge features
Pulses/cereals/canola/cereals rotation Pulses/cereal/canola/cereals rotation with perennials around recharge features
Salmon gum/gimlet soils (BE) Perennials around recharge features  
Pasture/cereals rotation Pasture/cereals rotation with perennials around recharge features
Pulses/cereals/cereals rotation Pulses/cereals/cereals rotation with perennials around recharge features
Pulses/cereals/canola/cereals rotation Pulses/cereal/canola/cereals rotation with perennials around recharge features
Danberrin
York/Jam Alleys of deep rooted perennials  
Pulses/cereals rotation Pulse/cereals rotation between alleys of deep rooted perennials
Pasture/cereals rotation Pasture/cereals rotation between alleys of deep rooted perennials
York Alleys of deep rooted perennials  
Pulses/cereals rotation Pulse/cereals rotation between alleys of deep rooted perennials
Pasture/pasture/cereals rotation Pasture/pasture/cereals rotation between alleys of deep rooted perennials

Maps reflecting land suitability for all of the different land uses (Figures 11­14) were overlayed, using standard GIS procedures. This resulted in a composite map in which the different polygons represent the land units to which different land uses can be allocated (Figure 16).