Monitoring Vegetation Extent Program
The Monitoring Vegetation Extent Program (MVE) has, as its main objective, the improvement of the State’s ability to report on native vegetation indicators. A particular emphasis is placed on reporting against the sustainability indicators listed in the
Tasmanian Regional Forest Agreement (RFA) and expressed in the five-yearly State of the Forests reporting document.
The MVE program aims to identify areas of native vegetation that are considered to have changed from woody cover to non-woody cover (e.g. from eucalypt forest to pasture, urban or water) within a nominated time period (e.g. five years). Over time, the changes detected by MVE are also used to prioritise areas of TASVEG mapping that require updated community codes.
The MVE program identifies areas of woody change through the automated comparison of satellite imagery, with extensive desktop validation undertaken using higher resolution imagery and ancillary datasets. Whilst field validation is not undertaken, an attempt is made to determine if the change is temporary or permanent, and to what land use category the land is transitioning. Previous iterations of the MVE program were limited to priority areas (largely corresponding to the private land estate of Tasmania) but, as of 2020, the program has been extended to include all land tenures.
The MVE program primarily uses Landsat and Sentinel 2 imagery to identify areas of change. NRE Tasmania has pursued partnerships with the Commonwealth and Queensland governments to secure the future of the MVE program. The tools and outputs generated via these partnerships are based on rigorous scientific research and provide the Tasmanian Vegetation Monitoring and Mapping Program (TVMMP) with the capability to analyse vast quantities of imagery without costly investment in IT infrastructure.
The current method for detecting woody change in Tasmania closely follows the procedures outlined by the Queensland
SLATS program (program partners). Whilst the SLATS techniques are broadly applicable to the Tasmanian environment, they are not perfect, and areas of woody change are not always detected e.g. due to persistent cloud cover. TVMMP utilises its partnership with SLATS to stay up to date with the latest advancements in remote sensing techniques for woody change monitoring.
As MVE change polygons are not field verified or subject to a 'double validation' procedure, the reliability of the outputs aren’t as high as those described by the SLATS methodology. Areas of woody vegetation regrowth are also not mapped under the MVE program and, for these reasons, the MVE change data is not currently published as a stand-alone item. Change data does however flow through to TASVEG, land use and other mapping products.
The picture above highlights woody change detection related to the construction of a new dam and reservoir. The left image was captured by Sentinel 2 on 14/02/2017 and the right image was captured on 21/12/2019. The white polygons highlight areas of woody removal, and the purple polygons highlight areas of woody disturbance (thinning of woody material, without conversion of the TASVEG community). These polygons were detected using Landsat imagery (30m pixel size). Current methods utilise Sentinel 2 imagery (which has a pixel size of 10m) allowing for greater accuracy in delineating woody change boundaries.