The Hornsby Vegetation Map 2017 provides current information on the native vegetation in the study area. Previous Hornsby Vegetation mapping was completed in 2008. There are substantial changes in the mapped polygons on the urban-bushland boundary based on the updated imagery and map rules. New mapping thresholds are designed to address Council’s information needs arising from new regulations governing vegetation management in NSW, in particular the 10/50 bushfire protection rule. These were developed in consultation with Council and tested in a trial area prior to mapping.
The map has been compiled using visual aerial photo interpretation of 2014 imagery and botanical review. New field work has included collect rapid floristic data at selected survey locations. The update incorporates other sources of field survey and vegetation mapping completed between 2008 and 2017. The map is approximately 1:25,000 scale.
The Hornsby Vegetation Map 2017 applies the existing, accepted vegetation classification established in Smith and Smith Hornsby Vegetation Map 2008 Update. Two updates are provided with the addition of a new code for mixed ‘urban native/ exotic’ patches (consistent with Sydney Metropolitan vegetation mapping that overlaps part of the study area (OEH 2015)) and an updated classification equivalence table necessitated by changes to NSW plant community types. Modified, predominantly native vegetation has been attributed with the closest, applicable native vegetation and denoted as disturbed. In areas identified as ‘urban native/ exotic’ the proportion of exotics is highly variable. Field validation is recommended to support land management decisions in these areas.
The 2017 map has identified 17,005 ha of vegetation including 664 ha of EEC and 653 ha of ‘urban native/ exotic’ vegetation in the study area. In addition, the map includes 231 ha of potential relictual EEC subject to field validation. A direct comparison of changes to vegetation extent between 2008 and 2017 are not possible due to differing map methods.
All maps have limitations and field validation is recommended for detailed site planning and to verify the presence of vegetation types, particularly communities or species listed under the NSW Threatened Species Conservation Act 1994 or Commonwealth Environmental Protection and Biodiversity Conservation Act 1996. Air photo interpretation is limited to a ‘birds eye view’ and may not detect changes in vegetation composition observable from field survey. Approximately 21% of the map has been validated by current and previous authors.
It is recommended that the Hornsby Vegetation Map 2017 is reviewed after one year in circulation. This will provide an opportunity to collate user feedback and identify minor edits required and any major revisions arising. Changes to the NSW PCT database may be incorporated at that time.
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