Provisions in the Environment Bill would place a requirement on developers to ensure habitats are left in a measurably better state than they were pre-development, delivering at least a 10% improvement in habitat biodiversity.
However, the paper, published in the journal the Society for Conservation Biology, which evaluated local authorities that are implementing net gain early, found that mandatory biodiversity net gain (BNG) as currently implemented at the local level risks poor outcomes for biodiversity when implemented nationally, “unless key aspects receive additional attention”.
One of the authors of the paper, ecological economist Sophus zu Ermgassen, noted that under biodiversity net gain “we lose open green space, traded for promises to deliver smaller, higher quality habitats in future”.
Of the BNG projects evaluated there was on average a 34% reduction in the area of non-urban habitats, “generally compensated by commitments to deliver smaller areas of higher quality habitat years later in the development project cycle,” he said.
One problem highlighted was that 95% of biodiversity units delivered in the sample came from habitats “within or directly-adjacent to the development footprint managed by the developers”.
The authors argue that these gains fall within “a governance gap whereby they risk being unenforceable”.
They claim that if the majority of biodiversity units are likely to be delivered on site, “current planning system mechanisms for monitoring and enforcing compliance are poorly suited for ensuring these materialise in reality”.
“Therefore as currently implemented, mandatory BNG risks not only delivering little for biodiversity, but also missing a major opportunity to finance investments in regional biodiversity priorities that can help restore biodiversity at a landscape scale,” they said.
The research was published the day after environment minister Lord Goldsmith told the House of Lords that BNG requirements may be applied to nationally significant infrastructure projects, which so far have been excluded from the proposals.