Authors: Jasmine Howorth, Lucy Randall and Jane Stewart
The Future Drought Fund is using ground cover (total vegetation cover) as an environmental indicator to monitor resilience. These ground cover metrics build on monitoring work under the National Landcare Program (Regional Land Partnerships).
This dashboard allows you to assess, by Natural Resource Management (NRM) Region, when and where agricultural land was likely protected from soil erosion. Users can compare areas protected under different cover thresholds, from 2001 to current, against regional targets.
Most soil degradation is caused by erosion during droughts, or when the breaking rains come at the end of a drought when the least protective vegetation cover remains.
Dashboard structure
The dashboard has two tabs:
- National summary – Summary of regions against erosion protection targets, by year. This is an annual overview of which Natural Resource Management (NRM) Regions are protected from wind and/or water erosion each year. There are four maps – one for each of the 3 erosion risk types considered and a combined summary map – plus a bar chart indicating the number of NRM Regions meeting all their targets each year.
- Time series by region – Erosion protection metrics for Australia and NRM Regions, by month. Select a region of interest and an associated target to see if sufficient vegetation has been maintained each month to minimise soil erosion on agricultural land. The map shows the location of the selected region, the heat map shows which months this region was above its target and the line graph charts the monthly time series of the percentage area protected from erosion.
The following cover thresholds are used:
- 50% or more to minimise wind erosion
- 70% or more minimise water erosion
- 80% or more to minimise water erosion on high-risk areas.
In regions with low rainfall soil erosion will be dominated by wind and therefore targets to protect agricultural land from water erosion may not be needed or achievable.
Further details on the contents of the dashboard can be found by selecting the ‘Information’ icon or hover over the ‘more information’ box.
Targets are not part of any current assessment of Future Drought Fund activities.
The Future Drought Fund (FDF) is the key investment by the Australian Government to build drought resilience in Australia’s agriculture sector, the agricultural landscape, and communities. The FDF Monitoring Evaluation and Learning (MEL) Framework, outlines the rationale, scope and approach for monitoring and evaluating the FDF, including setting a range of high-level indicators to monitor drought resilience.
The goals of the ground cover indicator and other high-level national resilience indicators are to:
- measure change compared to an appropriate baseline over long term FDF Funding Plans
- monitor trends and regional overviews, to support development and potentially targeting FDF program interventions.
It is acknowledged that ground cover and other resilience indicators will be impacted by other factors broader than FDF interventions. Changes are not expected to be attributed directly to the FDF but may be influenced by the FDF.
Indicators for economic and social resilience developed by ABARES can be accessed here.
Why ground cover?
Ground cover is a recognised important biophysical process indicator that can suggest landscape health, function and soil condition. Greater levels of ground cover reduce drought sensitivity by enabling rain infiltration, protecting soil from erosion, and supporting recovery from drought and linked environmental stresses.
This indicator can be interpreted as a measure of environmental drought sensitivity: in periods when ground cover is low the landscape is likely to be more sensitive to future drought events. Current ground cover levels are influenced by historical weather conditions, farming management practices, and natural resource management activities.
Source data
Remotely sensed Total Vegetation Cover (photosynthetic plus non-photosynthetic vegetation) is used to infer soil erosion risk. Monthly data is processed from 500 metre resolution MODIS satellite imagery.
Spatial data can be accessed via the Rangelands and Pasture Productivity online monitoring tool (RaPP Map). Regional monthly reports are also available.
Methods and metrics are based on Leys et al. (2020).
Agricultural land is as defined in Leys et al. (2020). Natural Resource Management (NRM) Regions are the 2017 boundaries. Fifty-four (54) of the 56 mainland NRM regions contain land used for agriculture.
Cover thresholds
The amount of Total Vegetation Cover (TVC) to reduce erosion is a minimum of:
- 50% to control soil loss by wind (Leys 1999)
- 70% to control soil loss by water (Lang 1979)
- 80% to control soil loss by water on steep slopes (>12%, or 7 degrees), erodible soil types and high rainfall areas (Leys et al. 2020).
These cover thresholds are applied to each 500 metre MODIS pixel. The number (or proportion) of pixels within an NRM region achieving a cover threshold gives the area protected from erosion. The area protected is assessed for each cover threshold and land use (agriculture). The area protected refers to the number (or proportion) of pixels within an area that are achieving a cover threshold. The soil is assumed to be protected from substantial erosion events in pixels where the TVC is equal to or above the cover threshold. Achieving these thresholds of TVC will reduce, but not entirely stop soil erosion.
Target
The target is to maintain the area protected from soil erosion by keeping the Total Vegetation Cover above the 10th percentile of the area exposed to erosion during the baseline period. Each NRM region, and land use, has its own target.
The metric reported is the area protected each month for each Total Vegetation Cover, 50%, 70% or 80%.
For annual reporting, for an NRM Region to show as blue, all appropriate targets must be met for all months (January to December). The focus is agricultural land. Because of the large climatic variation across Australia’s NRM regions it is not appropriate that every region has a target for area protected for every Total Vegetation Cover Threshold. Targets are only included in the regional overview when the 10th percentile for area protected is above 3 percent and below 97 percent of the total area of the region.
Baseline time period
Regional Total Vegetation Cover Targets are calculated using the baseline time-period of January 2001 to December 2019.
This baseline spans from the beginning of the MODIS archive up to the commencement of the Future Drought Fund. It includes a range of climatic conditions including the Millennium drought (spanning from 1997 to 2009) and the 2017 to 2019 drought.
References
Lang RD 1979, The effect of ground cover on surface runoff from experimental plots, Journal of the Soil Conservation Service of NSW 35: 108–114.
Leys JF 1999, Wind erosion on agricultural land, In: Aeolian Environments, Sediments and Landforms, Goudie AS, Livingston I, Stokes S (eds). John Wiley and Sons, England, pp. 143–166.
Leys JF, Howorth JE, Guerschman JP, Bala B, Stewart JB 2020, Setting targets for National Landcare Program monitoring and reporting vegetation cover for Australia, NSW Department of Planning and the Environment.