How To Achieve Biodiversity Net Gain: A Guide for Homebuilders

As of 12th February 2024, biodiversity net gain (BNG) has become a legal requirement for property developers.  ‘Applications for new schemes in England of more than nine dwellings will now need to achieve an uplift in BNG of at least 10%,’ advises Housebuilder magazine. 

So, what will homebuilders need to do to ensure they are meeting their requirements?

In this blog, we explore the subject of BNG, and give advice to property developers on how to increase the biodiversity on their developments.

Understanding Biodiversity

Biodiversity refers to the variety of plant and animal life in a particular location, with a high level of biodiversity being most desirable.  Unfortunately, the building of new housing developments produces a great deal of carbon emissions, can destroy the area’s natural habitats and reduce its biodiversity.  In addition to the destruction of habitats, noise and light from construction sites also impacts the behaviour of wildlife nearby.  These disturbances may cause wildlife to relocate to a newer and quieter area, reducing biodiversity around the construction site.  This is particularly the case when housing developments are constructed in areas that previously saw little footfall.

What is biodiversity net gain (BNG)?

Biodiversity net gain or BNG is a specific approach to the construction of new housing developments that aims to improve and add to the environment and biodiversity in an area, more than it takes away.  The state that the environment is left in should be measurably better than it was before the development was built, and actions should have been taken to ensure that habitats are safe and thriving.

Who has put these laws in place?

Having at least a 10% BNG increase has recently become a mandatory legal requirement for most newbuild developments.  Under the Environment Act 2021, to be given planning permission, you must be able to detail how your development is going to make a positive contribution to the environment and increase biodiversity rather than take away from it.

Why is BNG important?

According to the 2019 State of Nature report, data suggests that there has been a 13% decline in the average abundance of wildlife in the UK since the 1970s.  This decline has occurred despite current legislation protecting wildlife and biodiversity.  Certain sites and species are protected, but beyond that, there are limited resources in place to protect other habitats and wildlife.  This means that they could become lost to development and destroyed.  BNG aims to create new habitats as well as improve existing ones, and therefore serve as an additional form of protection for precious wildlife.

BNG is also important because it links to a range of existing agendas including place-making, improving air quality, green infrastructure, mental and physical health and well-being, addressing the climate emergency, flood resilience, and access to green space and nature.  BNG helps prevent animals from becoming endangered, helps with flood management and creates increased soil stability.

Who can we work with to achieve BNG?

Developers can work with a variety of groups to help conserve the environment and produce a BNG.  ‘Collaboration between landscape architects and ecologists is fundamental to designing BNG,’ says Natural England.  They advise that, ‘Establishing this early makes for a much better design process.   Collaborating to prioritise feasible habitat creation and enhancement, ensuring viability over 30 years.’ 

Homebuilders can also work with local governments, wildlife groups, landowners, environmentalists, and other stakeholders to ask for support and guidance on the best methods for constructing their development sustainably and with a BNG. 

What factors need to be considered?

It is crucial to understand how the size of your development will impact the number of measures you need to take in order to achieve a BNG of 10%.  Larger developments will rely on the implementation of many more strategies to achieve a 10% BNG when compared to what will be required of smaller developments of a few houses.  Therefore, it is crucial, particularly for larger developments, to plan the measures you will take to mitigate impacts on biodiversity before too much damage is done.

What are the mitigation and conservation hierarchies?

The mitigation hierarchy is a widely used framework and set of guidelines that was established to help developers prepare for environmental impacts.  It helps them in their aim to achieve no net loss of biodiversity, and to manage risks and potential impacts related to biodiversity and ecosystems.

The conservation hierarchy is a similar framework, but instead of reacting to the negative impacts on the environment and biodiversity, it is proactive, going beyond mitigating impacts and planning for the future and how we can conserve wildlife.  There are four main sequential steps in both hierarchies, and these include avoidance, minimisation, rehabilitation/restoration and offset.

Avoidance is the first, and arguably the most important step, and includes measures that should be taken to avoid damaging impacts to the environment from the initial construction of a development.  All other decisions and impacts on biodiversity stem from here.

The initial impacts that should be avoided could be direct, indirect, or cumulative impacts.  For example, when planning a development and deciding on the placement of different features, roads could be laid outside of locations that contain rare habitats.  An area could also be chosen for a development based on the number of trees that would need to be chopped down to make space.  If there is an option to choose an area that needs fewer trees chopped down for the land to be clear, this should ideally be the chosen location.

Minimisation is the next step and involves taking precautions and measures to reduce the intensity, duration and/or extent of the impacts that cannot be avoided completely.  For example, measures can be put in place to help reduce noise pollution or pollutant run-off from construction work.  Powerlines can also be designed to reduce the likelihood of birds being electrocuted and wildlife crossings could be built on roads to allow animals to safely roam about the area.

Rehabilitation/restoration involves taking measures to repair ecosystems that have been impacted by the building work taking place.  Restoration aims to return an area’s ecosystem to the way it was before it was impacted by development, whereas rehabilitation focuses on restoring the ecosystem in the area.  This can be achieved through measures such as planting trees to help stabilise bare soil that is left after a development has been built.  The trees also need to be planted, wherever possible, to replace any that had to be cut down to clear the land for the development to be built on. The difference with the conservation hierarchy is that degraded habitat areas and locations where trees have been chopped down would be actively restored, not restored because of the damage from construction work.

Offset, lastly, is the final step in both hierarchies, and involves making sure that any larger impacts on biodiversity are compensated for after all the other steps are completed.  There are two main types of biodiversity offsets: restoration offsets and averted loss offsets.  Restoration offsets try to rehabilitate or restore habitats that have degraded because of the development being built.  Averted loss offsets target reducing or stopping biodiversity loss in areas where this is expected to occur over time.  It is important to note that it is normally preferable if appropriate measures can be taken at an earlier stage in the mitigation hierarchy than at the offset stage.  This is because offset measures can be expensive and quite complex in comparison to other earlier steps.

What is wildlife conservation?

This concerns on-site measures that are taken to ensure that wildlife and their habitats can be kept safe both during construction and after the development is built and lived in.  Creating a nature reserve is the largest form of wildlife conservation that a development could include.  This would provide residents with a great location for going on enjoyable walks whilst also protecting wildlife and conserving biodiversity.

Other measures that could be implemented to help conserve wildlife include hedgehog highways, bat boxes, bird boxes, bug hotels and planting flowers to encourage bees and other wildlife.  A hedgehog highway is a series of holes in fences and walls that allow hedgehogs to pass freely between gardens, allotments and parks.  This protects hedgehogs because they don’t have to cross busy roads to move around.  A bat box is an artificial roost that is designed to encourage bats into an area, and a bird box/birdhouse is designed to be a space for birds to nest in.  A bug hotel is a manmade structure designed to be a shelter for various bugs and insects.  These hotels can be made in different shapes and sizes to cater to different types of insects.  All of these features also make charming additions to both gardens and shared outdoor spaces on new housing developments.

What are on-site and off-site measures?

BNG can be achieved through measures which are either off-site, on-site or a combination of both.  On-site measures include setting emission reduction targets, minimising the discharge of pollutants, creating and/or enhancing existing habitats, compensating for the loss of one type of biodiversity by providing another one and nature conservation.

Off-site measures are often overlooked because they are not prioritised over on-site measures.  However, some off-site measures that can be taken include sourcing materials such as timber from a sustainable company.  Habitats can be destroyed when trees are chopped down, so a sustainable timber company needs to think about their impact on biodiversity when chopping down trees.  Urban areas may rely more on off-site measures to help them reach a 10% BNG, as many of the developments in these areas may not have gardens or any of their own private green space.

What can we conclude?

Biodiversity net gain is a challenge, but it is crucial to achieve in developments built now and in the future.  It is incredibly important that we ensure we’re operating sustainably, and that the construction of new homes does not have a detrimental impact on the environment or biodiversity.  Planning ahead will allow you to implement measures on your developments to ensure that you reach the minimum of a 10% BNG.  In time, this percentage could increase to an even high figure, so it's a good idea to think ahead and stay up-to-date with changes made to environmental laws.