Building ecosystem resilience starts with condition: Applying the Habitat Condition Assessment System (HCAS) to Australia

Healthy ecosystems underpin biodiversity persistence, climate resilience, and human wellbeing. Yet decision-makers often lack consistent, repeatable information on where habitats are intact, where they are degrading, and how those patterns are changing through time. In Australia—a continent-scale country with diverse ecosystems, frequent natural disturbances, and multiple governance jurisdictions—this challenge has historically limited national environmental reporting and coordinated action.

The Habitat Condition Assessment System (HCAS) addresses this gap by providing Australia with a national, satellite-based capability for monitoring ecosystem condition. Developed through a long-term partnership between Australia’s National science agency, CSIRO, and the Australian Government Department of Climate Change, Energy, the Environment and Water (DCCEEW), HCAS integrates Earth observation (EO) data, environmental variables, and field-based ecological knowledge to deliver consistent ecosystem condition information across the entire continent.

The most recent version of HCAS delivers a coherent time series from 1988 to 2025, mapped at 90-metre resolution, yielding a single, common metric across all terrestrial ecosystems. By accounting for rainfall, fire, and other natural variability, HCAS helps distinguish ecosystem dynamics from human-driven impacts.

Today, HCAS underpins national environmental reporting, supports climate risk and resilience assessments, and provides critical inputs to Australia’s emerging Nature Repair Market. HCAS has progressed from an experimental research tool to an operational national monitoring system, informing decisions on conservation, restoration, and climate adaptation at scale.

Australia’s ecosystems support globally significant biodiversity, but they are subject to widespread pressures from land use change, altered fire regimes, invasive species, and climate extremes. Governments and land managers need to prioritise resources and evaluate conservation and restoration outcomes.

Some jurisdictions have developed ecosystem condition products, but differing methods and uneven coverage limit national comparability, especially for biodiversity and matters of national environmental significance that cross boundaries.

Before HCAS, there was no cost-effective, repeatable national method that could assess ecosystem condition while also accounting for Australia’s strong natural variability. This gap significantly constrained the capacity of land managers and policy makers to respond flexibly to environmental change and strategically deploy policy, regulations and funding.

HCAS was developed to meet this need. From early on, DCCEEW partnered closely in its design, ensuring that the system evolved in response to real policy and reporting requirements. HCAS has since become an annually updated operational system embedded in national decision processes.

HCAS expresses ecosystem condition as a score between 0.0 (removed or highly modified habitat) and 1.0 (high-integrity habitat that supports native species and ecological processes). HCAS integrates multiple ecosystem characteristics.

Three types of spatial data are combined:

For each pixel, HCAS compares observed ecosystem characteristics with those expected under reference conditions. The closer the match, the higher the condition score.

For example, increased tree cover may indicate recovery in a wet forest but degradation in a semi-arid grassland. Additionally, ecosystems naturally fluctuate in response to rainfall, fire, and climate variability—changes that should not be confused with loss of integrity.

HCAS addresses these challenges using a multivariate statistical framework that:

The result is a more realistic assessment across heterogeneous landscapes.

HCAS delivers:

HCAS has evolved alongside EO capability, moving from coarser MODIS inputs (250 m) to higher-resolution Landsat-based variables (90 m), improving its ability to capture finer-scale patterns relevant to management. The method can be adapted to higher-resolution or regional applications where suitable data are available.

All project datasets and inputs are published to an open repository (https://doi.org/10.25919/zhfq-1x80).

HCAS uses analysis-ready Landsat Annual Geomedian and Fractional Cover percentile data from 1988–2025 from the Geoscience Australia archive, processed on CSIRO’s Earth Analytics Science Innovation (EASI) platform.

Climate and soil layers provide ecological context for assessing conditions against local expectations; provided as Open Source infrastructure through Australia’s Terrestrial Ecosystem Research Network (TERN).

Reference sites are identified through multiple lines of evidence, including field-based monitoring, protected area data, land-use and infrastructure layers and vegetation extent. Experts and local knowledge holders are an important source of information, contributing assessments via workshops and the online Habitat Condition Assessment Tool (HCAT) that anchors the model in real-world ecological understanding.

HCAS continues to evolve as new EO capabilities emerge. Planned EO enhancements include:

These developments will further strengthen the role of EO in guiding ecosystem-scale decisions under climate change.

HCAS demonstrates how long-term EO data can be translated into actionable environmental intelligence. Its beneficiaries include national and state governments, land managers, researchers, and emerging environmental markets.

Key impacts include:

Beyond formal reporting, HCAS has revolutionised how decision-makers see and talk about ecosystems, shifting the conversation from isolated sites to connected landscapes observed consistently through time.