An integrative approach to implementing biodiversity net gain at the regional level

Biodiversity offsetting has emerged as an increasingly popular policy tool aiming to ensure that housing development associated with urban expansion can benefit nature. Offsets compensate for biodiversity losses from development by creating, restoring, or enhancing habitats, aiming to achieve either no net loss or a net gain in biodiversity. The effectiveness of this approach depends not only on the quantity and condition of the offsets but also on their spatial placement, which can be either on the development site or elsewhere. We present a spatially explicit modelling framework designed to explore how offset location affects biodiversity outcomes and ecosystem service co-benefits at the regional scale - the scale at which infrastructure planning decisions are generally made - using an English region (Buckinghamshire and Oxfordshire) undergoing significant housing growth as a case study. Findings reveal that closest proximity-driven offsetting underperforms in terms of biodiversity outcomes (species richness) and opportunity costs of agriculture. In contrast, regional prioritisation aligned with strategically planned conservation networks (i.e., regional Nature Recovery Networks), delivers the greatest increase in species richness (12%) and lower opportunity costs. In separate scenarios, restricting offsets to administrative planning boundaries yielded even lower opportunity costs and higher values for co-benefits (carbon sequestration and flood damage avoided costs), although this restriction resulted in a smaller percentage increase in species richness. These results demonstrate the value of strategic planning in guiding biodiversity offsetting implementation and highlight the potential for Nature Recovery Networks or similar conservation networks to enhance biodiversity outcomes at the regional scale.