This repository contains an interactive web map showing a grazing pressure index across the Living Landscape study region in the South Australian mallee.
The map represents inferred relative livestock grazing pressure associated with artificial water points. It was developed from pastoral dam locations, remote-sensing estimates of water persistence, dam decommissioning information, and a distance-decay model of grazing pressure away from water.
Higher values indicate areas expected to experience greater grazing pressure because they are closer to more persistent pastoral water sources. Lower values indicate areas farther from persistent water points, or areas associated with decommissioned or less reliable dams.
The grazing pressure index was developed to support spatial mapping of understorey condition across the Living Landscape case study area. Artificial water points can concentrate livestock and herbivore activity in semi-arid rangelands, producing gradients of vegetation modification that generally decline with distance from water. This map converts pastoral dam persistence into a continuous grazing pressure surface, then classifies that surface into ordinal understorey condition classes.
The final map is intended as a broad-scale decision-support product for visualising relative grazing pressure and its likely influence on mallee understorey condition. It should be interpreted alongside field validation, local ecological knowledge, management history and the assumptions of the grazing-pressure model.
The map covers the Living Landscape case study region in the South Australian mallee, including the Calperum landscape where related State-and-Transition Model and habitat-suitability work was undertaken.
Pastoral dam data were sourced from Gillespie (2025), which provided an inventory of dams in the study area and an assessment of their capacity to retain water. These data were originally derived from Sentinel-2 satellite imagery using the Normalised Difference Water Index, or NDWI, to estimate the persistence of standing water across a 10-year period.
The dataset included both active dams and dams that had been decommissioned before or during the study period.
A dam-specific grazing pressure index, or GPI, was calculated by combining water availability with the expected recovery of vegetation following dam decommissioning. Water availability was calculated as the proportion of study-period days in which standing water was detected:
water availability = days with water / total study-period days
For decommissioned dams, this value was reduced using a recovery multiplier based on the number of years since closure and an assumed 30-year recovery timeframe:
GPI = (days with water / total study-period days) × (1 − years since decommissioning / 30)
A 30-year recovery period was adopted as a pragmatic benchmark for substantial understorey recovery after dam decommissioning. This recognises that some recovery in semi-arid rangelands can occur within 5–10 years, but that more complete structural and compositional recovery may take several decades. For dams decommissioned before 1999 where the closure year was unavailable, 1995 was assigned as the decommissioning year.
For each dam, a distance-weighted grazing pressure surface was created by multiplying the dam-specific GPI by an exponential decay function of distance. The decay function was scaled so that the grazing pressure associated with a permanently watered dam declined from 1 at the dam to approximately 0.01 at 8 km from the dam.
Less persistent dams, or dams that had been decommissioned, had proportionally lower values across the full distance gradient. Dam-specific decay rasters were then combined using a cell-wise maximum, so that each pixel was assigned the highest grazing-pressure value exerted by any dam.
Gillespie, C. (2025) Standing Water in the Living Landscape: A decision support tool for developing a grazing pressure release strategy for conservation in the South Olary Plain. (ed. Murraylands and Riverland Landscape Board). Technical Report, Murraylands and Riverland Landscape Board, MRLB, Murray Bridge, South Australia.
Maisey, A. C. & Radford, J. Q. 2026. Living Landscape mallee grazing pressure index map. Interactive web map. GitHub repository.
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This project was supported by funding from the Australian Government’s National Environmental Science Program through the Resilient Landscapes Hub.
We acknowledge the Traditional Owners of Country throughout Australia and their continuing connection to land, sea and community, and pay our respects to Elders past and present.
Unless otherwise stated, written content and map outputs in this repository are provided under a Creative Commons Attribution 4.0 International licence.