DOI: 10.25919/a3h3-bs84
title: HCAS 3.1 (1988-2022) base model estimate of habitat condition (90m grid) and National Connectivity Index (NCI) 2.0, annual epochs of HCAS from 1990 to 2022 for continental Australia with uncertainty

description: Citation: Valavi R, Lehmann EA, Liu N, Levick S, Giljohann KM, Williams KJ, Johnson S, Botha EJ, Munroe SEM, 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 (2025) HCAS 3.1 (1988-2022) base model estimate of habitat condition (90m grid) and National Connectivity Index (NCI) 2.0, annual epochs of HCAS from 1990 to 2022 for continental Australia with uncertainty. Updated data collection 63571. CSIRO, Canberra, Australia. DOI: https://data.csiro.au/collection/csiro:63571. 

This updated HCAS v3.1 data collection derives in part from Geoscience Australia’s archive of Landsat Earth observation Collection 3 Analysis Ready Data (Commonwealth of Australia, 2021) Derivative Products version 3.1.0 (Geoscience Australia, 2022) and version 3.0.0 (Lymburner, 2022) 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 version 3.1 (1988-2022) base model (HCAS v3.1) estimation of habitat condition for terrestrial biodiversity
• 33 annual short-term epochs of HCAS from 1990 to 2022, formed using 3-year antecedent rolling averages of remotely sensed variables. 
• model-based uncertainty quantification as 95% confidence interval limits for the estimates of habitat condition for the long-term epoch (1988-2022) and selected short-term epochs (Lehmann et al., 2025)
• a classification of long- and short-term epochs of habitat condition into six modification levels based on experts’ best estimate of condition for each category of the Vegetation Assets, States and Transitions (VAST) narrative framework (Thackway and Lesslie, 2006; 2008)
• updated National Connectivity Index (NCI) v2.0 (Giljohann et al., 2022) for the long-term epoch using the HCAS v3.1 base model 
• long-term epoch of connectivity-adjusted condition (NCIC) derived from the geometric mean of the corresponding NCI and HCAS outputs (1988-2022)
• several other datasets to support use and interpretation of the long- and short-term epochs of HCAS habitat condition products and derivatives, including reference sites and remote sensing inputs. 

The HCAS v3.1 short-term epochs derive from the base model. The NCI and NCIC are developed by DCCEEW and published in this HCAS data collection, for the convenience of end users. 

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 habitat condition data varies 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. 

Data extent is defined by any data pixel that intersected a coastline polygon as defined by the land fraction dataset (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 (Liu and Newnham, 2024). 

Data are described in "Habitat Condition Assessment System (HCAS) version 3.1: A guide to the 90-metre data collection with uncertainty. Technical report EP2025-1549" (published in 2025, available from CSIRO's publication repository, see related links).