Australian rangelands and climate change – remotely sensed ground cover Citation Bastin G (2014) Australian rangelands and climate change – remotely sensed ground cover. Ninti One Limited and CSIRO, Alice Springs. Copyright © Ninti One Limited 2014. Information contained in this publication may be copied or reproduced for study, research, information or educational purposes, subject to inclusion of an acknowledgement of the source. Disclaimer The views expressed herein are not necessarily the views of the Commonwealth of Australia, and the Commonwealth does not accept responsibility for any information or advice contained herein. ISBN: 978-1-74158-252-9 Contents Acknowledgements ..................................................................................................................................................... 4 Key points ................................................................................................................................................................... 5 1. Introduction ............................................................................................................................................................ 6 2. Setting a cover target .............................................................................................................................................. 8 3. Method ................................................................................................................................................................. 11 4. Data source ........................................................................................................................................................... 11 5. Caveats ................................................................................................................................................................. 12 6. Findings ................................................................................................................................................................. 12 6.1 Broken Hill Complex, Western CMA as an example ........................................................................................... 12 6.1.1 Bare-soil targets for Western CMA bioregions .......................................................................................... 14 6.2 Bare soil targets for other Rangelands Cluster bioregions .................................................................................. 15 7. Key adaptation strategies ...................................................................................................................................... 16 Abbreviations ............................................................................................................................................................ 33 Glossary .................................................................................................................................................................... 34 References ................................................................................................................................................................ 36 List of Tables Table 2.1 Assignment of bioregions and NRM regions to summer and aseasonal rainfall zones. Bare soil levels in mid-September are analysed for summer-rainfall regions, and mid-March image dates are used elsewhere. ................................................................................................................................................................ 11 Table 6.1 Nominated bare-soil thresholds for Western CMA bioregions and the percentage area exceeding each threshold in mid-March 2001 to 2013. .............................................................................................................. 14 List of Figures Figure 1.1 Locations of the ~1500 ground sites used to calibrate and validate remotely sensed fractional cover. .......................................................................................................................................................................... 6 Figure 1.2 The autumn 2010 seasonal composite of fractional cover for Australia derived from MODIS imagery. ...................................................................................................................................................................... 7 Figure 1.3 The percentage bare soil within 500 m MODIS pixels, mid-September 2009 (a particularly dry time for much of inland Australia). NRM regions within the Rangelands Cluster are also shown. .................................. 8 Figure 2.1 Temporal variation in the fraction of bare soil within MODIS pixels for a 1° block (approximately 2 10,000 km ) centred on Broken Hill. ............................................................................................................................ 9 Figure 2.2 NRM regions and IBRA v7 bioregions in the Rangelands Cluster. ................................................................ 10 Australian rangelands and climate change – remotely sensed ground cover 2 Figure 6.1 Spatially averaged March-February rainfall between 2001 and 2013 for the Broken Hill Complex, Western CMA, and corresponding percentage areas of the bioregion exceeding specified thresholds of fractional bare soil. ................................................................................................................................................... 12 Figure 6.2 (a) Fractional bare soil in March 2009 for the Broken Hill Complex, Western CMA, (b) categories of bare soil mapped from the same image and (c) the location of the Broken Hill Complex in the Western CMA. ......................................................................................................................................................................... 13 Figure 6.3 The percentage area of bioregions in the Western CMA exceeding nominated target levels of bare soil in mid-March 2001 to 2013. ........................................................................................................................ 15 Australian rangelands and climate change – remotely sensed ground cover 3 Acknowledgements This project was funded by the Australian Government and was part of a collaboration between the Rangelands NRM Alliance, CSIRO, University of Canberra and Ninti One. Thanks to the following NRM regions for their review and input: Rangelands WA, Territory NRM, Alinytjara Wilurara NRM, SA Arid Lands NRM, Desert Channels Qld, South West NRM Qld and Western Local Lands Services. Thanks also to the members of the project’s Scientific Advisory Panel for their advice and guidance: Steve Morton, Craig James, Stephen van Leeuwin, Ian Watterson, Colleen O’Malley and Daryl Green. Australian rangelands and climate change – remotely sensed ground cover 4 Key points • Targets specifying the maintenance of minimum demonstrated here for setting and monitoring levels of ground cover are a common feature of maximum allowable levels of bare soil has merit, regional NRM plans. Setting realistic targets for then these targets should be further investigated broadly different land types within each region is a before being accepted. challenge. Targets should be set and reviewed with • Targets should be periodically reviewed, as they climate variability, and change, in mind. may need to be adjusted under continuing climate • National remote sensing capability now means that variability and projected change. This will be the fractional cover derived from 500 m MODIS case where perennial grasses with the C4 imagery, extending back to late 2000, is available. photosynthetic pathway (including buffel grass) The bare soil component of fractional cover can displace existing C3 herbage species due to potentially assist in setting, monitoring and atmospheric CO2 enrichment and continued reviewing regional cover targets. Knowing how warming. Elsewhere in the near to medium term, amounts of bare soil have varied under recent strategies such as patch burning to reduce extensive climate variability, fire regime and grazing wildfire, improved grazing land management and management provides some basis for specifying control of feral herbivores should increase appropriate targets for broadly different land types vegetation cover in most years. Both scenarios under continuing rainfall variability and possible (climate change and improved land management) long-term change. should warrant a regional lowering of the • Fractional cover images for mid-March and mid- permissible level of bare soil. September 2001 to 2013 were analysed to determine how the percentage area of bioregions Gary Bastin within NRM regions varied for different threshold levels of bare soil. Threshold values of bare soil CSIRO 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