How is the percentage mapped as previously comprehensively cleared calculated?
The percentage of previously comprehensively cleared land is calculated using published spatial data on native vegetation extent.
For projects outside NSW, the data comes from the National Vegetation Information System (v6.0), specifically a national 100m grid of major vegetation groups. Grid cells assigned major vegetation group 25 - cleared, or 29 - regrowth are treated as comprehensively cleared land.
For projects in New South Wales, the Explorer primarily uses the NSW Statewide Vegetation Type data, generalised from a 5 m to a 100 m grid, where cells not classified as a native Plant Community Type, or classified as one of several native Plant Community Types derived by clearing, are treated as previously comprehensively cleared.
Note that these datasets are not error free, but they are the best publicly available national data. Areas that have substantially regrown from previous clearing will generally not be identified as previously cleared. Similarly, areas that have experienced more subtle forms of clearing such as selective fodder harvesting or thinning will not generally be classified as previously comprehensively cleared. The data also have variable temporal currency, which is generally at least a few years old, so clearing in recent years is unlikely to be captured. The imagery provided in the mapping window can provide additional information about past clearing in the project area and surrounds.