Evidence to inform selection of Oxfordshire’s biodiversity net gain target

Report

This document compiles evidence to inform selection of targets for the level of Biodiversity Net Gain (BNG) that should be delivered through new developments in Oxfordshire.

Analysis shows that Oxfordshire is very nature-deprived compared to the average for England as a whole. It contains:

• Only 62% of the area of priority habitats per hectare (ha) compared to England as a whole
• Only 21% of the area of SSSIs per ha compared to England
• Only 18% of the area of nationally protected areas per ha (SACs, SPAs, Ramsar sites, IBAs, LNRs, NNRs and SSSIs) compared to England.

This analysis is based on national datasets. Further analysis is recommended using higher quality local habitat and species data for Oxfordshire from TVERC.

In addition, Oxfordshire’s remaining semi-natural habitats face intense pressure from housing and infrastructure development. Over 9,000 ha have been allocated for development in Local Plans, including over 1,200 ha of semi-natural habitats (grassland, woodland, scrub and parkland with scattered trees). This does not include the land lost to windfall developments. Analysis of Ordnance Survey Mastermap shows that over 2,700 ha of natural or agricultural land was converted to sealed surfaces and buildings in just the six years between 2014 and 2020.

Recent analysis has shown that most biodiversity units are delivered on site, with only around 7% currently being delivered off-site. While this conforms to the mitigation hierarchy, it is also very challenging to monitor and enforce delivery of many of these on-site units. It has been suggested that a target of 36% would be required to guarantee delivery of a net gain of 10%, given these enforcement problems.

Preliminary analysis indicates that a target of 10% BNG would only generate enough off-site biodiversity units to fund a maximum of 11% of the estimated costs of reaching the 30x30 nature recovery target (30% of land protected and managed for nature by 2030). This is an optimistic estimate because it includes only the costs of creating habitats and maintaining them for 30 years, not the additional costs of purchasing land or compensating landowners for opportunity costs. It also assumes that no semi-natural habitats that could contribute to the 30x30 target would be lost to development (otherwise the target would need to be even higher).

Therefore we conclude that the national minimum target of 10% BNG will not be sufficient to reverse the historic losses caused by development in Oxfordshire during the current local plan periods, and play a significant role in delivering the national and local biodiversity targets for 2030. Other councils in similar positions have chosen higher targets (e.g. 20% in Surrey) in order to increase confidence that genuine gains for biodiversity can be delivered.

Authors: Smith, A

• Publication status: Published
• Peer review status: Reviewed (other)
• Publisher: Oxfordshire Local Nature Partnership
• Place of publication: Oxford, UK
• Publication date: 2023-04-01
• Language: English
• Keywords: biodiversity net gain