Australian rangelands and climate change – remotely sensed ground cover

Australian rangelands and climate change – remotely sensed ground cover Report

Climate Change in Australia – Impacts & Adaptation Information for Australia’s NMR Regions

  • Author(s): Bastin, G.
  • Published: 2014
  • Publisher: Rangelands NMR Cluster, Ninti One Limited and CSIRO

Abstract: Targets specifying the maintenance of minimum levels of ground cover are a common feature of regional NRM plans. Setting realistic targets for broadly different land types within each region is a challenge. Targets should be set and reviewed with climate variability, and change, in mind. National remote sensing capability now means that fractional cover derived from 500 m MODIS imagery, extending back to late 2000, is available. The bare soil component of fractional cover can potentially assist in setting, monitoring and reviewing regional cover targets. Knowing how amounts of bare soil have varied under recent climate variability, fire regime and grazing management provides some basis for specifying appropriate targets for broadly different land types under continuing rainfall variability and possible long-term change. Fractional cover images for mid-March and mid-September 2001 to 2013 were analysed to determine how the percentage area of bioregions within NRM regions varied for different threshold levels of bare soil. Threshold values of bare soil within 25 ha MODIS pixels were ≥0.7, ≥0.6, ≥0.5, ≥0.4 and ≥0.3.The mid-March date represents likely maximal yearly bare soil in the southern part of the Rangelands Cluster, and the mid-September date is its equivalent in the central and northern cluster region. Using the former NSW Western CMA as an example, the analysis suggests that threshold levels of allowable bare soil should vary with land type (e.g. bioregion).A blanket target for an entire NRM region is not appropriate, particularly where mean annual rainfall, soil and vegetation type vary spatially within the region. Maximum allowable levels of bare soil should be lower in areas receiving higher or more reliable rainfall and where more perennial vegetation should be present. Conversely, more bare soil is permitted in arid parts of the Rangelands Cluster and where predominantly annual vegetation naturally occurs. Maximum threshold levels of bare soil are nominated for major bioregions within all NRM regions of the Rangelands Cluster. If the method demonstrated here for setting and monitoring maximum allowable levels of bare soil has merit, then these targets should be further investigated before being accepted. Targets should be periodically reviewed, as they may need to be adjusted under continuing climate variability and projected change. This will be the case where perennial grasses with the C4 photosynthetic pathway (including buffel grass) displace existing C3 herbage species due to atmospheric CO2 enrichment and continued warming. Elsewhere in the near to medium term, strategies such as patch burning to reduce extensive wildfire, improved grazing land management and control of feral herbivores should increase vegetation cover in most years. Both scenarios (climate change and improved land management) should warrant a regional lowering of the permissible level of bare soil.

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Suggested Citation
Bastin, G., 2014, Australian rangelands and climate change – remotely sensed ground cover, Report, viewed 13 August 2022, https://www.nintione.com.au/?p=2827.

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