Improving the ecological outcomes of compensatory conservation by addressing governance gaps: a case study of Biodiversity Net Gain in England

Abstract

Biodiversity compensation policies have emerged around the world to address the ecological harms of infrastructure expansion, but they have historically experienced weak compliance. The English government is introducing a requirement that all new infrastructure developments demonstrate they achieve a Biodiversity Net Gain (BNG). Previous research has highlighted governance gaps that risk undermining the policy’s ecological outcomes, as well as exploring the risks caused by fundamental capacity constraints in regulators, but the magnitude of their effects on the policy’s potential impacts on biodiversity remains unexplored. We collated BNG information from all new major developments across six early adopter councils from 2020-2022. We quantified the proportion of the biodiversity outcomes promised under BNG which are at risk of non-compliance, explored the variation in strategies that developments use to meet their biodiversity liabilities, and quantified the occurrence of simple errors in the biodiversity metric calculations submitted by project proponents. Large developments and energy infrastructure were more likely to meet their liability within their own development footprint, and small developments more likely to purchase offsets. We estimate that 27% of all biodiversity units fall within governance gaps that expose them to a high risk of non-compliance. Should these units instead be delivered through the off-site biodiversity offsetting market – which is associated with relatively more robust governance mechanisms – we estimate that the demand for offsets could rise by a factor of four, increasing the financial contributions generated by BNG for conservation activities on private land. Lastly, we find that 21% of applications contained conspicuous errors in their BNG calculations, half of which have already been accepted by councils, hinting at under-resourcing in councils assessing developments. Our findings demonstrate that resourcing and governance shortfalls risk undermining the policy’s effectiveness at halting biodiversity loss and require addressing to ensure the policy benefits nature.

Leveraging Biodiversity Net Gain to address invertebrate declines in England

“…Biodiversity Net Gain allows for large areas of either or both low distinctiveness or 'poor' condition habitat to be traded for smaller areas with higher distinctiveness and/or 'good' condition. Trading habitats in this way has been associated with a 38% reduction in green space post-development (Rampling et al, 2023). The tendency to create small and relatively isolated sites, even if their individual biodiversity value is higher, is likely to compromise biodiversity outcomes, for two main reasons.…”

“…To date, sites delivered under early adopter BNG councils have primarily occurred "on site", i.e., within the footprint of the development (Rampling et al, 2023). Smaller areas of post-development green space, such as those within housing developments, will face high levels of anthropogenic disturbance including erosion by footfall, littering, over-management, colonisation by Invasive Non-native Species (INNS), nutrient enrichment from domestic animal waste, pesticide use, and high densities of managed beehives in urban environments (Coleman 1981;De Frenne et al 2022;MacKell et al 2023).…”

“…Most gains made under BNG are likely to be within the built environment (Rampling et al, 2023) where pesticide use is commonplace. Grounds managers regularly use dicamba and glyphosate for the control of 'weeds' in gardens and on hard surfaces and gravel paths (Garthwaite et al 2020).…”

“…The overall reduction in post-development green space incentivised by the current implementation of BNG (Rampling et al, 2023) is a significant challenge that will not be solved by improved condition scoring alone. It is driven by the trading of existing large, low distinctiveness, 'poor' condition habitats for future small higher distinctiveness, 'good' condition habitats under the assumption that newly created habitats will have increased biodiversity value.…”