Towards strategic offsetting of biodiversity loss using spatial prioritization concepts and tools: A case study on mining impacts in Australia

Governments and industries increasingly use offsets to compensate for the unavoidable impacts of development on biodiversity. However, high uncertainty about the biodiversity outcomes of offsetting strategies has led to significant criticism in the academic and policy literature, while the ad-hoc application of offset rules within a region may lead to offsets favouring some species and communities at the expense of others. Here we explored opportunities to improve offsetting outcomes through strategic regional offset approaches, underpinned by concepts of complementarity and irreplaceability from the conservation planning literature, in comparison to more commonly used like-for-like approach. We assessed different offsetting strategies in the Hunter Valley, NSW, a rapidly developing region in Australia with an active mining industry. We quantified regional-level biodiversity losses arising from minimal to extensive mining expansion, along with species-specific impacts for 569 flora and fauna species, and prioritized areas for protection, restoration or both to offset the anticipated losses. Accounting for how well the offsets would complement existing protected areas, we compared the area needed for offsetting and the expected biodiversity outcomes among the different strategies. Our results highlight the benefits of a more systematic approach to offsetting in terms of an enhanced understanding of regional-scale impacts, more efficient identification of offset sites and improved biodiversity outcomes. Our approach encourages forward thinking about impending threats to, and opportunities for, biodiversity conservation and could serve as a template for strategic regional offset planning based on plausible scenarios of future biodiversity loss.