Biodiversity Net Gain: The Construction Industry’s Environmental Promise

Biodiversity is the animals and plants we see around us every day, the variety of which in some habitats is incredible. Environmental concern has been growing with the construction industry about the number of habitats that are disappearing through processes like deforestation and the construction of new developments. Biodiversity net gain is the promise of the construction industry to limit these environmental concerns whilst still being able to complete all these important projects, some of which will benefit society enormously like the building of new houses and hospitals.

What is Biodiversity Net Gain (BNG)?

Like humans, animals and plants need homes; these homes are all around us- our back gardens, local lakes, parks, and forests. The construction industry is tasked with building new homes for us but during this process the homes of animals and plants are being eradicated, this is where biodiversity net gain comes in. The aim of biodiversity net gain is to ensure that when a new development is completed that there are more potential habitats for animals and plants to thrive than before the development began, hence a gain in biodiversity.

Why is BNG so important?

The world is ever changing in both positive and negative facets, a negative facet is the continuous decline in biodiversity due to habitat destruction caused by new developments. By 2050, 90% of animals are expected to lose some of their natural habitat due to agricultural processes like deforestation and disappearance of waterways, the effect of new developments further increases habitat loss. The effects of the changes in the environment and the way animals live are evident with the extinction of species rate 10,000 times higher than the historical level.Woodland- BNG

Eye-opening statistics like these are exactly why biodiversity net gain is so important to be able to retain habitats for animals and plants to live alongside us in society and prevent extinction levels from increasing any further than this already alarmingly high level.

How is Biodiversity Net Gain currently measured?

On the 7th of July 2021, Natural England launched a new Biodiversity Net Gain metric called Biodiversity 3.0 metric as part of a new sustainable development toolkit. A Small Sites Metric was created alongside the 3.0 to allow for easier calculations of BNG on smaller development sites.

More Useful information of how the new BNG measurement metric works can be found here.

When does BNG become mandatory?

On the 30th of January 2020, The Environmental Bill was first read in the House of Commons and parliamentary proceedings began to instigate new laws surrounding protecting the environment in the UK. One of these laws that would be introduced would be mandatory biodiversity net gain among new construction developments. The bill is currently at the report stage within the House of Lords having already been passed through the Commons.

If the bill is successfully passed through the House of Lords and gets through the final stages without any problems as expected, the Town and Country Planning Act would be amended to include mandatory net gain as one of the requirements that needs to be met when granting planning permission. This is likely to come into effect in 2023.

What does mandatory Biodiversity net gain mean for developers?

Quite simply, the mandate of BNG means that developers must ensure that they are forward thinking when it comes to the development of habitats for plants and animals. Thus, meaning they must prove they’re taking the right initiatives and practices to advance biodiversity rather than aid its continuous decline when applying for planning permission for a new development or construction project.

Some of the potential rules and regulations that need to be complied with by developers include:

  • A minimum of 10% net gain in the biodiversity created calculated using Biodiversity metrics.
  • Habitats that can be secured for at least 30 years
  • Habitats can be produced on the development site, offsite or via statutory biodiversity credits
  • Registration on a national register for net gain delivery sites

What are the pros and cons of the impending Biodiversity Net Gain mandate?


  • An improved perception of the construction industry in the UK by contributing to the development of an improved environment
  • Less habitats being destroyed, less deforestation
  • More green spaces for communities to enjoy
  • A minimum 10% increase in biodiversity with every new development
  • New habitats created aiding animal and plant life
  • New still bodies of water being created helping with surface water and flood water management
  • More trees being planted lowers the carbon in the air we breathe


  • Longer planning permission processes for new developments with the new BNG regulations
  • Project costs could increase with the added cost on the preservation and advancement of habitats
  • Build times for developments could be increased due to more work to complete impacting developers and the people waiting for property
  • There may be a lack of knowledge among people within the construction industry over what Biodiversity is and how they’re going to take actions to improve it.
  • There needs to be awareness spread by the people enforcing Biodiversity net gain to ensure that the industry is aware.
  • There is no indication, at present, of how the measures are going to be regulated and enforced.

Will there be any exemptions for BNG?

The government’s response to the initial DEFRA consultation document suggests that there will be several exemptions which will include:

  • major infrastructure projects and marine sites
  • certain urban brownfield sites if they don’t contain protected or priority habitats
  • smaller ‘minor’ development sites(fewer than 10 residential units or an area of less than 0.5 hectares) will be offered a more simplified requirement and potentially lower than 10% gain
  • building extension projects


Are there any alternatives when biodiversity net gain on the original site is not viable?

The option for offsite compensation is also likely to be included where it is not possible to avoid, minimise or remediate habitat damage on site. In this instance a developer may opt for offsite compensation or as a last resort purchase biodiversity credits. For certain irreplaceable habitats such as ancient woodland, ancient and veteran trees, blanket bog, limestone pavement, sand dunes, salt marsh and lowland fen, this mitigation approach will not be applied, and they will continue to be protected in accordance with the National Planning Policy Framework (p.68-9, 2019) and the Conservation of Habitats and Species Regulations (2017).