DOI: 10.25919/zhfq-1x80
title: HCAS 3.3 (1988-2024) base model estimate of habitat condition (90m grid), National Connectivity Index 2.0 (NCI) and annual time series for continental Australia

description: Citation: Valavi R, Levick SR, Lehmann EA, Liu N, Giljohann KM, Williams KJ, Collings S, Johnson S, Botha EJ, Munroe SEM, Van Niel TG, Newnham G, Paget M, Malley C, Carlile P, Gunawardana D, Lyon P, Richards AE, Tetreault Campbell S and Ferrier S (2025) HCAS 3.3 (1988-2024) base model estimate of habitat condition (90m grid), National Connectivity Index 2.0 (NCI) and annual time series for continental Australia. Data collection 65549. CSIRO, Canberra, Australia. DOI: https://data.csiro.au/collection/csiro:65549.

The data collection utilises Geoscience Australia’s archive of Landsat Earth observation imagery over 37 years from 1988 to 2024, and comprises for continental Australia:
• the 90 m gridded (Australian Albers projection, EPSG 3577, Geographic Datum of Australia 1994) HCAS v3.3 base model (1988-2024) estimation of habitat condition for terrestrial biodiversity
• Annual epochs of habitat condition derived from 3-, 5- and 10-year rolling averages of remotely sensed ecosystem characteristics (condition variables) from 1990, 1992 and 1997 to 2024, respectively
• model-based uncertainty quantification as 95% confidence interval limit estimates of Habitat Condition for the long-term epoch (1988-2024) and selected short-term epochs, applying the method developed by Lehmann et al. (2025)
• classification of long- and short-term epochs of Habitat Condition into six modification levels based on experts’ best estimate of condition (Giljohann et al., 2024) for each category of the Vegetation Assets, States and Transitions (VAST) narrative framework (Thackway and Lesslie, 2006; 2008)
• National Connectivity Index (NCI) v2.0 (Giljohann et al., 2022) for the long-term epochs and short-term epochs using the corresponding HCAS v3.3 epoch
• long- and short-term epochs of Connectivity-adjusted Condition (NCIC) derived from the geometric mean of corresponding NCI and HCAS epochs
• several other datasets to support use and interpretation of the long- and short-term epochs of HCAS and NCI products, and related derivatives, including reference sites and the input remotely sensed ecosystem characteristics (i.e. Condition Variables). 

HCAS v3.3 (production version 3) was derived using 'ClassicHCAS' software version 0.2.0 and 'HCAS-workflow' software version 1.2.1. The NCI and NCIC are developed by DCCEEW and included in the data collection along with other derivative products, for end user convenience. The NCI has been updated using HCAS v3.3 epochs. 

Raster datasets (*.tif) are Cloud Optimised GeoTIFFs at 90 m grid resolution, GDA 1994 (Australian Albers, EPSG:3577). 

HCAS v3.3 Habitat Condition indices vary continuously from a theoretical minimum of 0.0 (ecosystem integrity removed) to a maximum of 1.0 (ecosystem integrity in reference condition). NCI also ranges continuously from 0.0 (unconnected removed habitat) to a maximum of 1.0 (fully connected intact habitat), as does the NCIC: from 0.0 (landscape ecosystem integrity functionally extinguished) to a maximum of 1.0 (landscape ecosystem integrity functionally intact and in reference condition). Both the HCAS and NCIC represent the contribution that a given site (grid cell) makes to effective area of ecosystem integrity remaining within a spatial reporting unit, as a proportion of the contribution made by a site in reference condition. 

Data extent is defined by any data pixel intersecting 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 3.3: A guide to the 90-metre data collection. Technical report EP2025-2979" (available from CSIRO's publication repository, see related links).