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.
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:
- retention of existing private and public remnants of native vegetation (including linear strips of habitat, or corridors);
- reconstructed habitat patches; and
- reconstructed corridors.
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.
Source: Data from McArthur (1992)provided by the Spatial Resource Information Group, Agriculture Western Australia.
| 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.
Note: Soil types match those listed in Table 4.
Source: Modified from data provided by Agriculture Western Australia.
| 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).
- Monotonically rising water levels: Sand plains, lateritic duricrust and basement outcrops in the watershed zones of the catchment were identified by Salama et al. (1993) as being the most significant recharge areas. In these areas, water levels are rising uniformly at up to 1.6 mm/day (Figure 15a).
- Continuously rising water levels with seasonal fluctuations: In the midslopes of the catchments water levels fluctuate in response to rainfall but display a long-term rising trend. The short-term fluctuations result from seasonal recharge by winter rainfall accompanied by lateral groundwater movement. In periods of high rainfall the recharge rate exceeds the rate of lateral flow resulting in a build up in groundwater storage and a subsequent rise in water levels (Figure 15b).
- Seasonally fluctuating water levels: Water levels in the lower areas of the catchments near streams show seasonal fluctuations with water reaching a peak following winter rains and falling to a minimum in summer (Figure 15c).
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.
Note: a) monotonically rising; b) continuously rising; c) seasonally fluctuating
Source: Modified from Salama et al. (1991).
| 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.
| 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 11Â14) 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).
In this section
Key
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