DOI: 10.25919/73vy-sc68
title: Environmental covariates stack for biodiversity and ecosystem modelling at 90m and 250m for continental Australia

description: These stacks of 125 environmental covariates are a subset of those compiled by TERN, with the addition of new covariates developed by TERN, Geoscience Australia and CSIRO. These data were pre-processed and standardised for use in the Habitat Condition Assessment System version 3, at 250m and 90m grid resolutions. The covariates are equally applicable to biodiversity and ecosystem modelling where the conceptual framework requires that the signature of anthropogenic land use be minimised. That is, the environmental covariates represent, as far as possible, the equilibrium state of the environment prior to industrialisation of the landscape following European colonisation of the Australian continent (c.1750). While the temporal window associated with source data used in developing many of these covariates varies, each covariate is intended to represent the long-term (multi-decadal) equilibrium state, approximating pre-1750. The careful selection of covariates that meet this conceptual framework requirement of 'non-anthropogenic' distinguishes this covariate stack from other compilations. 

The 250 m dataset is published in a geographic reference system (0.0025 degrees of latitude and longitude) in GDA94 (EPSG: 4283). The 90 m dataset is published in a projected reference system (Australian Albers in GDA94; EPSG: 3577). Each dataset is published as a cloud-optimised GeoTIFF (COG) in its original units and as the z-score standardised version, for the convenience of different applications. The z-score parameters for each covariate are included in the collection. 

Dataset names do not change, only the folder in which they are contained distinguishes the resolution and whether the data are standardised or not. 

Each dataset is also published with the expanded coastline and hole-filled, as described in Liu et al. (2025) to ensure all continental data pixels have a value. This ensures flexibility for other uses in making decisions about where to set the coastline. The original data compiled by TERN (Searle et al., 2022) shows where data holes were filled, as this varied between datasets. The input and output mask datasets used in developing the 250m and 90m versions of HCAS are therefore also supplied to facilitate use in different applications. 

All compiled covariates are potentially relevant in a range of ecosystem and biodiversity modelling applications, including HCAS, and represent a subset of the hundreds of covariates in the original TERN compilation (Searle et al., 2022). Descriptions and citations associated with each dataset were reviewed, checked against sources, and updated for accuracy. The updated descriptions and source citations are provided for the 125 datasets included in this collection. 

For method details, see Liu et al. (2025): Liu N, Williams KJ, Searle R, Wilford J, Botha E, Johnson S, Read A, Valavi R, Lehmann E, Giljohann KM and Joehnk K (2025) Environmental covariates for predicting the reference state of ecosystems in the Habitat Condition Assessment System (HCAS). Technical Report EP2025-2352. CSIRO, Canberra, Australia.