Poorly designed biodiversity loss-gain models facilitate biodiversity loss in New Zealand

Biodiversity offsetting and compensation proposals are routinely employed through the resource consenting process to address development-induced indigenous biodiversity losses in Aotearoa/New Zealand. Determining the quantum of demonstrable biodiversity gain required to adequately account for development induced losses is a fundamental component of designing a biodiversity offset. However, trading biodiversity is complex and must account for substantial uncertainties. Therefore, biodiversity offset models that account for losses and gains are a necessary tool for determining the adequacy of an offset proposal. Yet there is currently no accepted standard approach to loss-gain calculations. Models of insufficient ecological and mathematical robustness can perpetuate systematic biodiversity losses and distract decision-makers from discussions regarding real-world ecological consequences of development. We discuss these issues and present a case study to demonstrate how poorly designed biodiversity models that are currently in use in Aotearoa/New Zealand facilitate biodiversity loss. Model development and implementation has been hampered by a tension between competing requirements: (1) simple models that are user-friendly and not resource intensive to parameterise, and (2) models that are sufficiently complex to represent ecological values at an appropriate resolution. It is imperative that newly developed models adhere to standards employed in other ecological modelling domains to curb current and future biodiversity loss. Ecological practitioners and decision-makers are often unable to assess the quality of models and a lack of guidance and oversight of biodiversity offset modelling by the wider ecological and academic community is evident. We conclude that biodiversity offset modelling is a critical research area and that advancements within this space are urgently needed to halt ongoing biodiversity declines.