Costing global biodiversity framework delivery in megadiverse Australia.

Most nations worldwide face substantial funding gaps to halt biodiversity loss, yet many governments lack comprehensive cost estimates essential for effective budget allocation and implementation planning. This study provides a comprehensive estimate of the costs Australian governments would need to bear to deliver the Kunming-Montreal Global Biodiversity Framework in Australia. Using interpretive principles and evidence from peer-reviewed literature, and spatial analysis, we derived actions, unit costs, and cost factors (the amount of each action required to achieve the GBF's targets). We populated an automated model with these inputs to produce national and jurisdictional government cost estimates to inform planning and cost-sharing between national and subnational governments. Our method captures cost efficiencies from actions that benefit multiple targets. Our model estimates that delivering GBF targets in Australia will cost governments approximately AU$28.5 billion per annum from 2025 to 2050. At 1.1 per cent of GDP, this estimate shows comprehensive biodiversity conservation is arguably fiscally realistic. Our cost factor data can be disaggregated at various scales-such as bioregions, ecosystems, or Indigenous nations-to inform biodiversity-inclusive spatial planning. Our analysis and cost model offer a replicable methodology for other national governments to quantify their financial resourcing requirements for GBF implementation.