This blog by Professor Katherine Wills for the Oxford Long-Term Ecology Lab assesses some of the key flaws in Natural England's Biodiversity Tool and Environmental Benefits from Nature Tool, which are designed to ensure that housing and infrastructure developments produce biodiversity net gain. She identifies a key loophole that allows developers to claim net gains in biodiversity even with an overall reduction in green space. She proposes a much more robust Net Environmental Gain Tool to provide certainty to developers, ecological consultants, local authorities, and the wider public.