What the data is already telling us about biodiversity net gain planning policy

This post is by Sophus zu Ermgassen of the Durrell Institute for Conservation and Ecology (DICE) at the University of Kent.

Although the government has acknowledged the need for ambitious action to prevent loss of biodiversity, it is committed to the rapid expansion of potentially environmentally damaging infrastructure under Project Speed. This is central to its plan to level up and stimulate the post-coronavirus recovery. But can these two ambitions be reconciled? Is it possible to improve the UK’s nature whilst also expanding infrastructure’s footprint across the country?

One of the government’s main mechanisms for reconciling these two policy objectives is the desire, embedded in the Environment Bill, to make it mandatory for new developments in England under the Town and Country Planning Act to achieve ‘net gain’ in biodiversity.

Planning projects must now improve biodiversity
Last week, the government announced the net gain requirement will also be extended to nationally significant infrastructure projects. In short, the amendment introduces a new component of the planning process: all planning applications will need to demonstrate they improve biodiversity by at least ten per cent, measured using the government’s ‘biodiversity metric’. So new developments will need to leave biodiversity better off than they found it. Who could argue with this?

Naturally, hidden beneath the surface of this apparent ten per cent increase in the multidimensional concept that is ‘biodiversity’ is a complex story, underpinned by assumptions and, in some cases, serious flaws requiring urgent attention.

At DICE, we have conducted the first evaluation of the outcomes of the biodiversity net gain policy, working together with six local councils already implementing policies equivalent to biodiversity net gain, in advance of the national roll-out expected in 2023. Our analysis has uncovered, in unprecedented detail, what is being delivered under the banner of this policy and has revealed a number of pointers for policy improvements that could help it to catalyse a genuine recovery of English nature.

Net gain is leading to a loss of green spaces
Our first finding is that the policy is leading to quite large losses of open green space (34 per cent of the area of different non-urban land use types in our dataset was converted into urban land use under biodiversity net gain). Yet this counts as a net gain in biodiversity overall because, to compensate, developers are promising to improve the ecological quality of the remaining, smaller areas of non-urban habitats, so that, overall, the developments in our sample have led to a reported 20 per cent increase in ‘biodiversity units’. However, these losses in open green spaces are occurring today, and a large chunk of the promised units will be delivered in the future. This means that if there is a failure to deliver those ecological improvements in the future, biodiversity will be lost overall; so it is essential that the governance mechanisms regulating these future gains are watertight. Unfortunately, they are not; more on that later.

One promising finding was that the majority of construction was occurring on non-urban habitats with quite low biodiversity value to begin with, such as croplands or pasture. This is preliminary evidence that biodiversity net gain might be promoting construction on land of lower nature value, which is important for protecting high value wildlife sites throughout the landscape.

Small, disjointed areas for nature are being created
Another notable result is that the volume of biodiversity units being purchased ‘off-site’ (ie from local authorities or private providers via ‘biodiversity offsetting’) is much smaller than many predicted, including Defra. Off-site purchases applied to just five per cent of all biodiversity units in our sample. Ninety five per cent of all the biodiversity units delivered under biodiversity net gain have come from landscaping measures and habitat enhancements within the footprint of developments, or from directly adjacent land. This means that, instead of delivering biodiversity gain in line with the Lawton principles of “more, bigger, better, more joined up”, it is, in general, creating small, disjointed areas of habitat within developments.

Furthermore, the off-site market for biodiversity units has been touted as a potential important source of funding for restoring nature in England, especially in the Local Nature Recovery Networks, also to be set up through the Environment Bill. However, our data suggests this funding source might be small; although as the market for biodiversity units matures, it could be that developers start purchasing more from the market, instead of delivering the biodiversity units themselves.

Most net gain promises are legally unenforceable
One aspect we have learnt from this study is the importance of governance. The policy documentation we studied shows that the government is putting a lot of effort into monitoring and regulating biodiversity units delivered off-site via the biodiversity offsetting market; but our data reveals this might be only a tiny fraction of all the biodiversity gains delivered through the policy. As 95 per cent of the gains in our sample were through on-site habitat enhancements, robust mechanisms are needed to ensure compliance of on-site habitat enhancement according to promises made.

However, when we reviewed all the policy’s governance documentation, we found the opposite is true. In fact, failure to create habitat of a certain condition, promised in the initial planning application, may fall below the threshold used by local government to decide whether or not to pursue planning enforcement action. So it looks like 95 per cent of the promised nature ‘benefits’ of biodiversity net gain might be unenforceable. This is a critical gap to address.

Opportunities for improvement
Another issue is the quality of the biodiversity metric itself. We surveyed a sample of grassland experts and found they were unable to replicate the judgements about grassland type and quality reported in a set of biodiversity net gain assessments associated with planning applications. This indicates that the metric might not be a reliable guide to the biodiversity quality of a site.

Additionally, although the government’s biodiversity net gain consultation revealed that most stakeholders agree with the idea of delivering gains on-site, our data explores these on-site gains in high resolution, and it is highly questionable whether they are going to be sufficient to improve England’s nature significantly. For example, 27 per cent of all the biodiversity units delivered by the policy in our sample come from grasslands and scrub habitats within housing developments.

We propose a solution whereby the total biodiversity liability that developers can meet within their own development footprint is capped at some level, and the rest is paid into funds directly invested in improvements in Local Nature Recovery Networks. Such a strategy might give people the on-site nature they need to improve their wellbeing, without relying on these potentially ecologically questionable on-site habitats to improve England’s biodiversity.

Biodiversity net gain has the potential to help mitigate the impacts of Project Speed on nature, but it will require serious further work before it lives up to its name and delivers tangible improvements. The good news is there is still time to change it, as long as there is the political will.

The report associated with this study can be found in the journal Conservation Letters.

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