Greengage has worked with both the City of London and London Borough of Tower Hamlets to develop their own evidence bases on the feasibility of a unit per hectare measure rather than % gain, to inform new Biodiversity Net Gain (BNG) policies within their respective individual emerging Local Plans.
The City of London and London Borough of Tower Hamlets are both highly urban in nature, with a high proportion of zero and low baseline sites that will be developed on. Therefore, the mandatory BNG of 10% within the Environment Act 2021 (due to come into force in January 2024) is not considered an appropriate measure for the delivery of meaningful BNG, within new developments. For both Local Planning Authorities, a biodiversity unit per area (BU/ha) measure has been explored for viability.
These studies established the current BNG ‘business as usual’ baseline scenario and then what the BNG would be in scenarios where ecological enhancements followed good practice guidance, providing a maximised scenario.
Both studies looked at a proportion of approved (pipeline and built out) applications that had enough information to be able to determine proposed BNG, and then assessed what units could have been delivered if biodiversity had been maximised on each of the sites.
Through the assessments, it was considered that a 2.5 BU/ha target for London Borough of Tower Hamlets and a 3 BU/ha target for the City of London would provide a challenging but accomplishable target to ask of developers.
Where there is a BNG shortfall, the use of Community Infrastructure Levies (CILs) being imposed on developers is being explored to deliver nature based interventions that will deliver benefits for each borough, and can be tailored to the individual requirements and unique climate induced challenges each face.