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Oliver Bussell

Partner - Sevenoaks and Ashford

27th February 2020

Planning permission – Biodiversity requirements to be imposed on all future developments

Provisions in the Environment Bill are likely to bring about radical changes to the way planning consent is granted in England and Wales.

At present Local Planning Authorities may only impose planning conditions on development in compliance with the National Planning Policy Framework – guidance is provided via caselaw; and there are also special rules for the imposition of certain ‘conditions precedent’. Imposing conditions is at the discretion of the Local Planning Authority. And it is based on the planning officer’s assessment of a proposal in the context of the local plan and other material considerations including the representations of consultees.

Now a blanket condition is to be imposed on all development.

The Environment Bill requires that 10% biodiversity net gain in the development site should be established before any work is carried out on the site. That means before the planning permission is implemented. That assessment – of the baseline and of what 10% net gain would amount to – must be set out in a report submitted by the developer and agreed with the LPA. Provision ought to be on site but there are options which would allow for provision off-site but nearby; or in default for the purchase of conservation credits.

This poses a number of questions. How is 10% calculated? Where does that figure actually originate? What off-site land is covered? Are there any exemptions? And can any net gain over 10% be credited against future development?

How is 10% Biodiversity Net Gain calculated?

The 10% Biodiversity Net Gain is calculated by reference to a fairly well established set of metric data published by DEFRA and to be maintained by the Secretary of State. The metric attaches a value to each type of habitat on site, its condition, its strategic significance at a national and local level and its connectivity, i.e. the extent to which it connects to on-site or off-site habitats. So in theory we are looking at an ecology report based on set criteria which are hopefully free of too many subjective judgments.

The risk, legally, is that any plan which suggests a route to 10% which is not robust and achievable could either render a proposal unviable, or a consented development unlawful and subject to enforcement.

Where does the Biodiversity figure actually originate?

As to where the 10% figure comes from, it does not seem to have any very strong basis. Biodiversity Net Gain requirements are being piloted in various parts of the country with mixed aims and startlingly varied results. Take Lichfield District Council whose 20% target is typically exceeded with an average 60% Biodiversity Net Gain achieved! Some of the larger housing developers are piloting their own Biodiversity Net Gain programmes on a voluntary basis so while the principle and working of Biodiversity Net Gain appears to be achievable it may be that Government has decided to set the bar somewhere which sounds low and therefore achievable rather than gong too high and falling flat.

What off-site land is covered when considering Biodiversity Net Gain?

Looking at off-site land, remember that the starting position is that Biodiversity Net Gain should all be provided on site. If that cannot happen then provision off-site is permissible, as close as possible to the development. But how is such land bound? The developer is quite unlikely to own it himself. This is where the newly created legal mechanism known as ‘conservation covenants’ come in.

Conservation covenants are described in some detail in the draft Environment Bill. They look very much like s106 covenants in that they envisage positive or negative covenants, they run with the land and so remain enforceable after a landowner has disposed of its interest in land, and many but not all the tools of enforcement are the same as regards breach. But they are materially different in terms of who enforces them. Instead of being the geographically static local planning authority they may be granted to “designated bodies” which are defined as either the Secretary of State, local authority, a charity or a public body whose main purpose or functions relate to conservation of the natural environment, places of archaeological, architectural, artistic, cultural or historic interest– such as Natural England or the Environment Agency. That has the advantage that a developer could achieve their Biodiversity Net Gain across a county boundary. But it presumably suggests that the covenantees are going to be robust in policing the betterment of the sites for which they are responsible. For an untested system that may be difficult to establish which could quickly put in question the benefits actually accruing. It would probably be neater if the Local Planning Authority was also the enforcer of the conservation covenant – which is a possibility in the current draft. That would locate the development control and enforcement function in one place and give confidence that the scheme was working. The main problem with Local Planning Authorities running the system is that they may not in all cases have the ecology expertise in-house and therefore they may be reliant on external ecology consultants and there could be significant delays.

Biodiversity Net Gain Exemptions

Biodiversity Net Gain exemptions are thin on the ground at this stage. Crown land is exempt and so is land consented under a development order. There is ample provision made in the Environment Bill for regulations to give further nuance but nothing beyond that.. In fairness the Government policy response from July 2019 makes clear that DEFRA are recommending exemptions for brownfield development, minor development (defined at 1-9 dwellings on a site of less than 1 hectare), marine development and householder extensions. But the lack of that detail in the Bill seems all the more curious as a result, not less so. If they are prepared to put it in policy why not so far in law?

Can any Biodiversity Net Gain over 10% be credited against future development?

It is unclear from the bill whether any additional Biodiversity Net Gain can be credited to future developments. It seems unlikely that this would be the case unless the additional percentage could be on land subject to a conservation covenant. It would certainly seem that development would then need to offer the off-site land as its contribution – ie. to that development’s 10% Biodiversity Net Gain. The planning authority would then need to agree to the allocation of that land towards the 10%.


Despite obvious benefits to the environment and human health by systemic conservation and enhancement of biodiversity, there will be many challenges. The way forward is unclear due to the very general nature of the draft Bill and the inherent difficulty in converting biodiversity into simple numbers on a spreadsheet.

What seems clear is that:

  • Assessment of on-site ecology will need to be determined at the earliest opportunity, perhaps even as early as site selection to ensure the financial viability of the development. Design for Biodiversity Net Gain will have to be ‘baked in’ to the proposal.
  • Further amendment may include additional exemptions. Developers of schemes with less than 10 dwellings will in particular be keen to know if exemption or modification of the 10% gain will be allowed for these projects.
  • The concept of off-site biodiversity creates a new market in land to be utilised, and to have value, for the express purpose of conservation as it facilitates development elsewhere.

Whether you are a landowner or a developer looking for legal advice on conservation covenants or Biodiversity Net Gain within the planning process please don’t hesitate to contact either Oliver Bussell or Jo Bryan in Rix & Kay’s Planning & Environment team.

Read our introduction to Biodiversity net gain and land development

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