Mandatory BNG is finally here…why is today important?

After many years in the making, Mandatory Biodiversity Net Gain (BNG) comes into force in England from today, Monday 12 February 2024.[1]

Because Mandatory BNG only attaches to new planning applications made after today, there are not anticipated to be any immediate fireworks and this week will likely not feel a great deal different to many people who have been and will be involved in the delivery of Mandatory BNG. However, today does mark an important step in the development of environmental law in England and it is right to reflect on how and why we have reached this point and sketch out where we might be going.

Biodiversity declines and the need for nature recovery

Mandatory BNG is a flagship component of the Environment Act 2021, one of the most important pieces of legislation ever produced in this country on the natural environment. For this reason the passage into law of the Environment Act 2021 is often rightly compared to the struggle by environmental NGOs to get the Wildlife and Countryside Act 1981 into law for the protection of habitats and species or the groundbreaking National Parks and Access to the Countryside Act 1949, which after decades of campaigning by environmental groups dating back to the 19th century was introduced in the wake of the Second World War to protect our most beautiful landscapes and to open up access to nature for a war weary public.

The Environment Act 2021 is so important because it marks an important paradigm shift in natural environment law in England from nature conservation to nature recovery. Up until now the focus of natural environment law and policy has, rightly, been aimed at protecting the remnants of biodiversity left in our landscape by protecting certain habitats and species which are seen as representative of the abundant wildlife which used to surround us. The hope was that by doing this at least some parts of the natural environment, though far from pristine, would not be entirely lost and could be handed down to future generations. The problem, however, is that this approach, often likened to a “museum collector piece” approach to nature, did not stop biodiversity declines, which became particularly deep and rapid in the second half of the twentieth century.

Alarmingly, the UK is now one of the most nature-depleted countries in the world. According to a study by the Natural History Museum in 2020, the UK has only half of its entire biodiversity left, putting it in the bottom 10% of the world’s countries for biodiversity and according to the State of Nature Report 2023, is continuing to decline. It has the lowest level of biodiversity in Europe.

As a result of outstanding ecological science in this country, particularly outstanding citizen science, we have marked that decline with frightening precision. A study released by the British Trust for Ornithology last year, for example, found that there are 73 million fewer wild birds in the UK since 1970

We have also lost 97% of our wildflower meadows and 90% of our wetland habitats in the past 90 to 100 years. Bringing that into human-sized perspective, as a boy my father remembers flocks of lapwings in the fields behind his house. He has not seen any in the same fields for the past 40 years. My youngest son’s favourite animal is a hedgehog; he has never seen one in the wild. As a result of growing concerns over declining biodiversity levels, the Government commissioned Professor Sir John Lawton to carry out an extensive review of protected sites, which reported in 2010. The report, Making Space for Nature, said that: “The essence of what needs to be done to enhance the resilience and coherence of England’s ecological network can be summarised in four words: more, bigger, better and joined”. Doing this ought to be comprised of five key approaches:

  1. Improve the quality of current sites by better habitat management.
  2. Increase the size of current wildlife sites.
  3. Enhance connections between, or join up, sites, either through physical corridors, or through ‘stepping stones’.
  4. Create new sites.
  5. Reduce the pressures on wildlife by improving the wider environment, including through buffering wildlife sites.[2]

Despite the virtual unanimous agreement in the environmental sector with the recommendations of the Lawton Review, precious little happened in terms of environmental law and policy in the years that followed its publication. That changed, however, when (unexpectedly) Michael Gove MP was given the role of Secretary of State for Defra in 2017, bringing some much needed political competency, drive and vision to the Department and in 2019, when Boris Johnson became Prime Minister who, unlike previous Prime Minister’s, took a genuine interest in environmental matters and made space in the Parliamentary timetable for ambitious primary legislation to shape the future of wildlife law post-Brexit.

The Environment Act 2021

The result of this rare political alignment of the stars led to the drafting of the Environment Bill, an ambitious piece of legislation which aimed to place nature recovery at the centre of political decision-making at both a national and local level. Aside from Mandatory BNG, discussed below, the Environment Act 2021 does this by:

  • Introducing into law the duty to create legally binding environmental targets and for the Government to produce regular environmental improvement plans explaining how those targets will be achieved.
  • Imposing an enhanced “biodiversity duty” on public authorities to both actively conserve and enhance the natural environment and for local authorities to publish “biodiversity reports” in which they must record and report on the action they are taking locally to conserve and enhance the natural environment.
  • Requiring local authorities to produce Local Nature Recovery Strategies, which will act as a sort of spatial planning for nature, by ensuring that key habitats and the connections between them are mapped out and plans put in place to promote nature recovery. Collectively these local strategies will in time combine to create a landscape-scale national nature recovery strategy, very much in the image of the Lawton Review recommendations.
  • Creating the Office for Environmental Protection to act as a watchdog for environmental law and policy post-Brexit to ensure that environmental commitments and obligations are met.
  • Creating a new legal mechanism called “conservation covenants” to legally secure the management of land for the conservation and enhancement of nature, if necessary, in perpetuity.

Mandatory BNG

At the core of the Environment Act 2021 is the requirement for Mandatory BNG, which more than anything else has taken the new focus on nature recovery from the public to the private sector. It does this by making it a condition of new planning permissions under the Town and Country Planning Act 1990 that developers must secure “at least” 10% biodiversity net gain for nature for each development (subject to exemptions). In contrast with the previous approach in the planning system of “no net loss”, doing this would ensure that every time planning consent is granted for a new development[3] in England, nature would stand to benefit. These net gains for nature can be delivered:

  • on-site, within the redline boundary of the proposed development;
  • off-site, by developers creating their own off-site habitats or by purchasing the required “biodiversity units” directly from landowners in the local area (or via intermediaries acting on behalf of those landowners); or
  • as a last resort, purchasing statutory biodiversity credits as part of a national scheme provided by the Government.

For many developers Mandatory BNG will not be a seismic shift because they have been dealing with BNG for some time now though national and local planning policy. This is because the National Planning Policy Framework says: “… planning policies and decisions should contribute to and enhance the natural and local environment by…minimising impacts on and providing net gains for biodiversity…” (see para 180(d) of the National Planning Policy Framework). For this reason, many local development plans already encourage or require BNG. Although Mandatory BNG does not replace local planning policy, it will regularise and standardise the approach to BNG for developers across England. This will now ensure a consistent approach for developers, but will inevitably place strain on local authorities in those parts of the country which are not yet currently familiar with BNG.

Will Mandatory BNG enable nature recovery?

As to whether Mandatory BNG will have a major impact on nature recovery, the simple fact is that, as at April 2022, only 8.7%[4] of England is currently of developed use and therefore the potential gains for nature generated by new development will always be marginal. In contrast, agriculture comprises 63.1% of land use. Accordingly, the proposed changes to agricultural subsidies post-Brexit to encourage more environmentally sensitive farming which will arguably have a greater benefit for nature.

However, three points are important to note. First, by making environmental gains a mandatory part of new development, the Government has consciously created a regulatory burden which will require millions of pounds to be injected into habitat creation schemes across England. Without that regulatory burden in the form of Mandatory BNG, that investment would simply not have happened and, it is hoped, it will create a cascade effect within the environmental sector which could advance projects which have so far been shelved through a lack of investment. I know from speaking with the landowners I have been working with over the past year in preparation for Mandatory BNG that they are genuinely excited about the things they will be doing for nature now as a result of this new source of investment.

Second, it is too simplistic to view the environment as a “problem” that can be fixed through a clever piece of policy or technology. We have, and always will, live in a relationship with nature, relying on it as both our life-support system and as the primary basis of our shared collective culture and history. Trying to “solve” issues relating to nature is a bit like trying to “solve” aspects of our relationships with the people we know. Our relationships are constantly evolving, ongoing, and form a part of our daily lives.  You make them work through trying your best to minimise the worst parts of yourself by trying to habituate better and more productive behaviours. Similarly, we will become better stewards of the natural environment when we habituate more sustainable attitudes towards it and in that respect Mandatory BNG will help do that by making it habitual to make space for nature in and around our built environment.

Finally, doing this ought to make things better for people and nature. It is increasingly known that access to the natural environment is of benefit both to our physical and mental well-being.  As we have seen from developments such as the Kingsbrook development at Aylesbury where the RSPB worked closely with Barratt Homes to create a wonderful development, people do tend to want to live in places where they can feel a connection with nature. I know from my conversations with developers that for these reasons many of them are already carefully integrating nature into their developments and are thinking about these issues from the earliest design stages.

What will happen next?

Mandatory BNG has only come about because of a rare alignment of political forces. Without that it is unlikely that such an ambitious policy would have been made law. Whilst Defra officials and Natural England staff have clearly worked exceptionally hard, the rollout of Mandatory BNG has been far from perfect with lengthy delays and periods of uncertainty. Furthermore, many of the local authorities I have worked with still feel unprepared for Mandatory BNG and have real concerns over important issues such as enforcement of on-site and off-site net gains when their resources are already so stretched. Indeed, the lack of designated responsible bodies by the Secretary of State means that one of the legal mechanisms to secure Mandatory BNG, conservation covenants, cannot yet be used. With economic clouds never far from the horizon, it may be tempting for political back-sliding and drift if things seem too difficult. The success of Mandatory BNG is therefore by no means certain.

If that is the case then this would also have potential negative implications for the success of the next step in nature recovery law and policy, which will be to apply net gain principles to the marine environment, beyond the low water mark. This is because the Government recently responded to the consultation on the principles of marine net gain – an emerging area of marine policy which offers the opportunity to accelerate marine nature recovery in English waters, building from first principles. 

That would be a shame given the urgent need for nature recovery. Now that the net gain policy has finally become law in England it will be down to the developers, ecological consultants, local authorities and landowners to make it work. A lot will depend on how the next 12 months play out and many of us will have front row seats to that.

If you need training on Mandatory BNG then please get in touch with Please also find out more about our Natural Capital Team.

[1] Please note that “small sites” will are given a longer transition period until 2nd April 2024. See here: Biodiversity net gain: exempt developments - GOV.UK (

[2] Lawton, J.H., Brotherton, P.N.M., Brown, V.K., Elphick, C., Fitter, A.H., Forshaw, J., Haddow, R.W., Hilborne, S., Leafe, R.N., Mace, G.M., Southgate, M.P., Sutherland, W.J., Tew, T.E., Varley, J., & Wynne, G.R. (2010) Making Space for Nature: a review of England’s wildlife sites and ecological network. Report to Defra, p. viii.

[3] Mandatory BNG is not yet in place for Nationally Significant Infrastructure Projects granted under the Planning Act 2008.  It is anticipated that Mandatory BNG will apply to such development from November 2025. 

[4] Land use statistics: England 2022 - GOV.UK (

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