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Open Letter to Government Calls for Biodiversity Net Gain

An open letter to George Eustace, Defra Secretary of State and Tony Juniper at Natural England, written by a group of senior academics, essentially calls for the recently mandated biodiversity net gain (BNG) initiative to focus on delivering nature recovery as its primary aim. I have been saying for over a decade that developments should deliver gains for nature which is what prompted me to set up the Environment Bank in 2006, as I was disillusioned by the treatment of biodiversity in the planning and development control sector. Fiddling with relatively small fragments of ‘habitat’ (really just landscaping and planting, within, say, a housing scheme), has no chance of providing nature recovery at scale. The open letter provides much needed academic weight to that reasoning.

A debate has been running about the relative merits of providing BNG on-site versus off-site, with the ‘mitigation hierarchy’ used to pressure developers to place as much of the BNG requirement on-site as possible, without understanding the full ecological implications of doing so. Some planning authorities have erroneously refused planning permission unless the developer puts all of the BNG requirement into the development site, using up highly costly development land, compromising the masterplan, and reducing net developable area.

There is an inherent lack of evidence of success of on-site mitigation approaches (in fact they almost always fail a) because they are small fragments, b) because of a lack of enforcement by planning authorities once a development has been permitted and c) because developers move on and fail to properly fund on-site delivery).

For this reason I always was, and remain, of the view that off-site provision is the only viable means of accounting for impacts of development on biodiversity. That this has now been supported by a range of senior academic ecologists and economists who have researched the differential value or otherwise of on-site BNG versus off-site BNG, is most welcome. They call on Government to ensure that emphasis is given to off-site habitat creation rather than placing reliance on on-site which usually gets transformed to lower quality land cover (such as amenity grassland) once a development is occupied.

Of course, many developments will be unable to provide much if any BNG within the development site boundary – commercial warehousing and logistics schemes, some linear infrastructure, ports etc., are often large areas of concrete or tarmac. Off-site areas such as large-scale habitat banks, that we at Environment Bank are providing as our business model because of poor performance and value of on-site BNG, will enable large, strategic, biodiversity-rich sites and networks to be created, something unachievable with on-site BNG.



The authors of the open letter call for monitoring, reporting and enforcement of on-site as well as off-site BNG delivery (and for both to be placed on the Government’s BNG register) and for local planning authorities to be properly resourced to deliver the BNG system. They recommend making it a condition of the developments’ consent that funding is ring-fenced to deliver BNG for the full duration of the BNG requirement ie 30 years. It is critically important that management is properly funded in order to maintain the condition of the on-site BNG area otherwise the biodiversity gain plan, on which a planning permission depends, will be flawed.

The authors stress that any dominance of on-site over off-site BNG delivery will result in opportunities for ambitious coordinated nature recovery failing to be realised. They state that  ”If off-site actions represented the majority of offsets ……… all sorts of opportunities for synergy with wider nature restoration efforts could be catalysed, including using offsets to support the connectedness of conservation areas and to contribute to the Local Nature Recovery Networks”.

The market for BNG Credits (a registered product of Environment Bank) is expected to be between £500m - £1.2bn per year (Ecosystem Markets Taskforce supporting research 2013), for a fully mandated system where delivery is largely through large-scale off-site habitat banks. It would therefore be a woeful shame if constraints placed on developers to deliver BNG on-site, being the obverse of the Lawton principles of bigger, better and joined, and leading to small fragments of short-lived ‘habitat’, led to this funding failing to restore biodiversity at scale in the natural environment.

Only through diverting BNG delivery to off-site provision into large habitat banks will the Government’s and society’s ambition for nature recovery, as enshrined in the 25-year Environment Plan and Environment Act 2021, be realised. I therefore truly hope that Government takes the view of the authors of the open letter seriously.


Professor David Hill CBE
Chairman, Environment Bank

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David Hill