DOI: 10.25919/wt04-0d81
title: HCAS 3.1 (1988-2022) base model estimate of habitat condition (90m grid), National Connectivity Index (NCI) 2.0, 3-year average annually rolling epochs of HCAS and NCI from 1990 to 2022 for continental Australia

description: Please cite as follows: Valavi R, Williams KJ, Liu N, Levick S, Giljohann KM, Johnson S, Botha EJ, Munroe SEM, Lehmann EA, Collings S, Searle R, Van Niel TG, Newnham G, Paget M, Joehnk K, Hosack GR, Harwood TD, Malley C, Gunawardana D, Sivanandam P, Richards AE, Tetreault Campbell S and Ferrier S (2024) HCAS 3.1 (1988-2022) base model estimate of habitat condition (90 m grid), National Connectivity Index (NCI) 2.0, and 3-year average annually rolling epochs of habitat condition from 1990 to 2022 for continental Australia. Data collection 63571. CSIRO, Canberra, Australia. DOI: https://data.csiro.au/collection/csiro:63571. 
 
This data collection derives from Geoscience Australia’s archive of Landsat Earth observation imagery between 1988 and 2022, and comprises for continental Australia:
• the 90 m gridded (Australian Albers projection, EPSG 3577, Geographic Datum of Australia 1994) Habitat Condition Assessment System (HCAS) version 3.1 (1988-2022) base model (HCAS v3.1) estimation of habitat condition for terrestrial biodiversity
• updated National Connectivity Index (NCI) v2.0 (Giljohann et al., 2022) using the HCAS v3.1 base model, and 
• 3-year antecedent average rolling short-term epochs of HCAS from 1990 to 2022 and one experimental 5-year epoch ending 2022 for continental Australia
• long-term epoch of connectivity-adjusted condition (NCIC) derived from the geometric mean of the corresponding NCI and HCAS. 

The HCAS v3.1 short-term epochs derive from the base model. The NCI long-term epoch uses the corresponding long-term HCAS v3.1 epoch as an input (production version 2). The NCI is developed by DCCEEW and included as one of the derivative products. 

The core collection in the HCAS v3.1 product suite comprises 34 datasets of habitat condition (the base model long-term epoch and 33 short-term epochs), and other input, derived and supporting datasets to inform use and interpretation, including the long-term epoch (1988-2022) of the NCI v2.0 and the derived connectivity-adjusted condition, NCIC. The majority are raster datasets in GeoTIFF format (*.tif) at 90 m grid resolution, Geographic Datum of Australia (GDA) 1994 (Australian Albers, EPSG:3577). All GeoTIFFs are provided as Cloud Optimised GeoTIFFs (COGs). In most cases, a corresponding *.png map image is also provided for quick views. Example summary tables by IBRA bioregions are also provided. 

The HCAS v3.1 base model and epoch datasets are habitat condition indices that vary continuously from a theoretical minimum of 0.0 (ecosystem integrity removed) to a maximum of 1.0 (ecosystem integrity in reference condition). The index represents the contribution that a given site (grid cell) makes to the effective area of ecosystem integrity remaining within any given spatial reporting unit, expressed as a proportion of the contribution made by a site in reference condition. 

The data extent of the curated collection is defined by any data pixel that intersected a coastline polygon, as defined by the land fraction dataset developed by Liu (2024). The data and no-data extent of each grid layer encompasses the area within the Australian Continental Exclusive Economic Zone (EEZ) (Alcock et al., 2020), excluding territories of Cocos, Christmas, Norfolk, Macquarie, Heard, and McDonald Islands, as well as Antarctica. 

This HCAS v3.1 product suite builds on the earlier HCAS v3.0 and substantially improves on, and extends, the former HCAS series 2 outputs. HCAS v3.1 uses 14 remotely sensed ecosystem characteristics derived from the Digital Earth Australia Surface Reflectance NBART Landsat Analysis Ready Data Collection 3 derivative products (Commonwealth of Australia, 2021). 

Data descriptions are summarised in the accompanying "Habitat Condition Assessment System (HCAS) version 3.1: A guide to the 90-metre data collection. Publication EP2024-5394" documentation, which can be downloaded separately from CSIRO's publication repository (see related links).