National Intertidal-Subtidal Benthic NISB Habitat Distribution Map Series

Brief description

The National ECM Key Habitat Distribution Map Series were derived from the NISB Habitat Map created by the University of Tasmania for a partnership between the Department of Climate Change and the National Land and Water Resources Audit. It supports the DCC/Audit partnership by providing a nationally consistent set of the available mapping data that show the distribution of habitats that occur between the approximate position of the highest astronomical tide mark (HAT) and the location of the outer limit of the photic benthic zone (approximately at the 50-70 m depth contour). This area is broadly equivalent to the “inner” and “mid-shelf” regions identified by Geoscience Australia. The resulting map data set forms a core component of the ECM National Habitat Map Series. The habitat classes include: coral reef, rock dominated habitat, sediment dominated habitat, mangroves, saltmarsh, seagrass, macroalgae and filter feeders (e.g. sponges), as defined in the NISB Habitat Classification Scheme. The scheme is designed to support the development of marine ‘ecoregions’ or bioregional subregions. Details of the scheme and the process of its development are available in National Intertidal/Subtidal Benthic (NISB) Habitat Classification Scheme Version 1 (Mount, Bricher and Newton, 2007). The 10 km and 50 km tiles distribution maps that form the National ECM Key Habitat Distribution Map Series were derived from the NISB Habitat Map in order to produce maps at resolutions that are easy to interpret at state and national extents. For each state, two layers were produced, one with 10 km and one with 50 km tiles. In each layer, new fields were created listing the presence, absence, unknown distribution or nonapplicability of the Habitats of Interest (HOI). The HOI are rock substrate (Class 1.2), unconsolidated substrates (Class 2.0), coral habitat (classes 1.1 and 1.2.2.3), sediment dominated habitats (Class 2.0.1), seagrass dominated habitats (Classes 1.2.2.4 and 2.0.2.1), mangrove dominated habitats (Class 2.0.2.2) and saltmarsh dominated habitats (Class 2.0.2.3). There are technical geographic and cartographic issues that arise when comparing mapped data sets of multiple scales, as is the case for this compiled and derived data set. The two derived information products were generated to provide a simplified spatial representation of the broad distribution patterns of each of the key habitats National ECM Habitat Map Series User Guide_v7.doc 30/04/2008 Page 32 of 156 across large areas. These derived products are designed to enable the visualisation of the habitat distributions at the regional and national extents. It is extremely important to note that they are definitely NOT able to be used to calculate areas of habitat types.

Lineage

Statement: The National ECM Key Habitat Distribution Map Series are derivatives from the NISB Habitat Map. The NISB Habitat Map is a composite data set of the best available habitat mapping data for Australia’s intertidal and subtidal benthos. Using ArcGIS 9.2, all the input layers were imported into geodatabases for processing. Fields were added to each layer’s attribute table, listing the data source (DSource), original file name (DOrig_File), metadata file name (DMeta_File) and ANZLIC ID number (ANZLIC_ID). Each layer then had NISB fields added, which correspond to the four tiers in the NISB Habitat Classification Scheme (2007). NISB_Sub01 and NISB_Sub02 refer to the first two tiers of the classification, which are based on the substrate. NISB_Dom01 and NISB_Dom02 refer to the dominant land cover, as described in the third and fourth tiers. The scheme is hierarchical, so where insufficient information was available to fully classify a polygon, it was classified to the finest tier possible. The NISB Habitat Classification Scheme includes decision rules that describe the limits of each habitat class. For example, for a polygon to be described as class 1.2.2 Structural Macrobiota Dominated, SMBs (Structural Macrobiota such as seagrass or mangrove) must cover more than 10% of the substrate. However, many of the source data sets do not include information on percent cover, and so the original classifications were accepted on face value. That is, if the data provider identified a polygon as seagrass dominated sediment, we classified it as 2.0.2.1 Seagrass Dominated, without information about how precisely the original category fit the NISB classes. Microsoft Access was used to reclassify the layers. Where habitat types extended inland (e.g. saltmarsh or mangrove), a buffer was used to select those that are “coastal”. The coastal zone is defined here as being within 500 m of the coast or less than 10 m above sea level. A 500 m buffer was created around the coastline as defined by the Geodata Coast 100k (Geoscience Australia 2004). The Shuttle Radar Topography Mission (SRTM) v2 Digital Elevation Model was used to determine all areas below 10 m ASL. These two areas were merged to create the coastal zone buffer. Once all the layers for a state had been converted to the NISB Habitat Classification scheme, they were merged into a single layer. Where layers overlapped, a decision was made as to which was considered to be more reliable. This decision was based on a combination of the metadata records and a visual inspection of the data sets. Then, the erase and merge functions were used to combine the layers. The layers were then tested to ensure that the classifications were translated correctly from the source data and that there were no overlapping polygons. Overlaps were discovered in some of the source data for Victoria and were left as they were. The layers were not tested topologically. The maps were not independently ground-truthed. To create the tile layers, tessellated grids with tiles of 10km and 50km that cover the extent of state coastal waters were created using Jenness Tools’ Repeating Shapes tool (www.jennessent.com). Then, we used a script written by Dominik Jaskerniak and Luke Wallace, from the University of Tasmania, to classify these grids according to the habitat types found within them, as defined in the layer _NISB_PLUS.shp. National ECM Habitat Map Series User Guide_v7.doc 30/04/2008 Page 34 of 156 The logic of the script was as follows: If a habitat of interest (HOI) occurs anywhere within a tile, that HOI is listed as Present. If the entire tile has been mapped and the HOI does not occur anywhere within that tile, it is labeled Absent (Note: due to the patchy nature of coastal habitat mapping, this is a very rare class). If the tile covers an area where it is extremely unlikely that the HOI exists (e.g. rock, sediment, coral, seagrass and macroalgae are only mapped below the high tide line, and are therefore unlikely to occur on land) then the tile is labeled N/A. If the tile is incompletely mapped, but the area that is mapped does not include any of the HOI, the tile is labeled Unknown. The contributing agencies must be acknowledged with each use of this derived data set are: Contributors to the National Intertidal/Subtidal (NISB) Habitat Map: Department of Natural Resources, Environment and the Arts, Northern Territory Government of Australia Queensland Department of Primary Industries and Fisheries Queensland Parks and Wildlife Services Environmental Protection Agency Great Barrier Reef Marine Park Authority National Oceans Office Western Australia Department of Environment and Conservation South Australian Department of Environment and Heritage New South Wales Department of Environment and Conservation New South Wales Department of Primary Industries: Fisheries Conservation Commission of the Northern Territory Land Conservation Unit Victorian Department of Primary Industries Parks Victoria Tasmanian Aquaculture and fisheries Institute