Biodiversity Net Gain - will it be worth the wait?

, 14 February 2024
Biodiversity Net Gain - will it be worth the wait?
House Sparrows © Roger Wilmshurst

By Laura Brook 

Conservation Officer

Finally, after many setbacks, Biodiversity Net Gain (BNG) has become mandatory. It’s been in development since the new Environment Act came into force in November 2021, with a commitment to delivering BNG through the planning process. As of this week, the new guidance means that wildlife habitat must be left in a better state than it was before a development took place.

While the term ‘Biodiversity Net Gain’ has been bandied about for many years and its presence has been noted in planning policy and guidance as a ‘measurable’ net gain, no firm figure against the term ‘measurable’ had been made. But from Monday 12th February, all major developments in England must deliver a minimum of 10% BNG (with minor sites in England obliged to do so from April this year). Put simply, this new duty will require developers to deliver measurably more for nature than is lost through development.

For decades, building development has been a significant cause of nature loss. But the new legal requirement to deliver BNG in England offers the potential for developers to take a more positive approach and contribute to nature’s recovery, rather than drive its decline.

It’s important to note that these new BNG obligations do not replace existing requirements to avoid causing damage to wildlife and wild places. Nor do they give developers free rein to damage habitats on the promise that harm can be rectified elsewhere. But where, as a last resort, damage to habitats cannot be avoided, developers will be required by law to ensure an overall increase in biodiversity of at least 10%, on top of any work required to compensate for any damage done. The 10% gain is intended to be achieved through the enhancement, restoration, or creation of new habitats, with an obligation to ensure these gains are managed and maintained for at least 30 years.

But will this result in meaningful gains for wildlife? If BNG is truly going to contribute to halting the nature crisis, we’ll need to see high standards and ambitious targets set for delivery. Done well, BNG could make a positive contribution towards nature’s recovery and help address the climate emergency in the process.

As it stands, we are concerned that BNG is not currently on track to play its part in addressing the severity of the continuing nature crisis, and that current ambition is set too low. In response, The Wildlife Trusts have outlined a series of measures to raise that ambition. We believe:

  • Developers and Local Planning Authorities should go beyond the minimum 10% requirements and aim for at least 20% BNG for nature.
  • Local Planning Authorities must be resourced with the right level of skills and capacity across departments to oversee the BNG process, making sure it is properly implemented, monitored, and enforced.
  • BNG must be ‘additional’ to existing mechanisms for nature conservation and enhancement.
  • UK Government should change policy and guidance to prevent the sale of excess biodiversity units.

Here in Sussex, we have been working to support Local Planning Authorities with emerging BNG policies in their Local Plans for many years. Last week saw the Wildlife and Countryside Link Coalition publish a briefing paper, which highlighted that 10% BNG might not be enough to stem the loss of wildlife. It went on to highlight how Worthing Borough Council is one of only two Local Authorities (0.6%) in England with an adopted Local Plan policy that goes above the mandatory 10% BNG. Sussex Wildlife Trust was directly involved in shaping and pushing that policy to be more ambitious. This demonstrates the breadth of work we must now engage with if we are to work actively to defend and restore nature.

Read more in The Wildlife Trusts’ briefing: A New Era for Nature Positive Development (PDF) 

Leave a comment


  • Kevin Lerwill:

    Having recently been in a conversation with staff from a Local Authority about BNGs, I have two main concerns; Firstly, that most Council’s don’t have an (in-house) Ecologist that would ideally regularly survey and know what species they have on their sites and therefore there is little or no base-line information for what is there already…which then makes it very difficult to know if there has been any increase in bio-diversity or not (as a result of the BNGs). Councils are also reluctant to pay freelance Ecologists to carry out surveys because of the costs involved.
    Secondly, knowing the local green spaces in my area as well as I do, I strongly believe that greater emphasis should be put first on improving existing nearby habitats, rather than looking for new ones, as existing sites will already have established flora and fauna that can be improved for bio-diversity far quicker than completely new ones, but many existing sites are currently severely under-managed and in sharp decline/poor condition as a result. Otherwise, developers will just take the easy option again and just randomly plant more trees wherever they can, which is little more than a box-ticking/quota filling exercise that fulfils their legal obligation, but with minimal effort on their part and has minimal benefits for bio-diversity in most cases…We need more wild flower verges/meadows, not more rows of plastic tree tubes.

    15 Feb 2024 19:10:00

  • Colin Sharp:

    Fundamentally building has to now be confined to brown field sites!, towns in East Sussex have been expanding out into the countryside resulting in for instance the situation of Eastbourne, Pevensey, Westham, Polegate, Stone cross and Hailsham now virtually joined together with the loss of farmland, woodland, wetlands and water courses built over. The losses are on a grand scale with so much wildlife losing their habitats, besides the Birds and Mammals losing their wildlife corridors there is the loss of rivers and streams with their own populations of fish, newts, frogs etc. every single new home built is another net loss for wildlife!. We simply cannot sustain the rate of loss of habitat and a defining line has to be drawn.

    16 Feb 2024 00:34:00

  • Becky Evans:

    What is classed as a ‘minor site’?

    16 Feb 2024 14:20:00

  • Christopher drake:

    Currently ecologists will oversee a PEA/PRA for agriculture land which simplified scores a BNG score because agriculture is deemed low in the field parcel and not the boundaries. 10% gain for agriculture would simply be a diverse margin containing 150 different species of flowers and grasses. This indicates that 10% does not go far enough and poperty development can still build high density housing without wildlife corridors!

    17 Feb 2024 09:11:00