Bigging up biodiversity

Climate Change and Sustainability February 06, 2020

Steph Wray,  RSK Biocensus Managing Director, on the subject of biodiversity net gain.

Biodiversity is important because each species plays an important role in keeping the world turning. For example, biodiversity can help with water purification, flood regulation, provision of food, fuel and minerals, climate regulation and pest control. Basically, if you like breathing, having water to drink or a climate that’s survivable, then biodiversity is important to you.

Biodiversity net gain is an approach to development that leaves biodiversity in a better state than before. It is crucial, as we are now seeing an unprecedented rate of species’ extinction. ‘No net loss’ is no longer enough.

The idea of biodiversity net gain however is sometimes confusing, like comparing apples and pears. So how can we know if what we are proposing really demonstrates a gain?

Steph Wray

Steph Wray 

The upcoming change in the law proposes a target of 10% gain for all development projects, which will be enacted through the Environment Act this year. To deliver this 10% gain, developers will need an understanding of what biodiversity exists pre-development by measuring how much of each habitat type there is, and the condition it is in. This is given a numerical total in ‘Biodiversity Units’. Developers must then apply the mitigation hierarchy; predicted biodiversity impacts should be avoided or minimised as far as possible before considering mitigation and compensation methods. The value of the biodiversity retained, enhanced and created as a result of the development is then calculated, and any loss or gain measured.

Trees 18 months after planting

Trees 18 months after planting (image provided by the Woodland Trust) 

Under the new law, any shortfall in the number of Biodiversity Units post-development will need to be created along with the Biodiversity Units for a 10% increase. This total in Biodiversity Units can then be interpreted as areas of different habitat types appropriate to the area.

Developers will be able to meet this target by revisiting the design to preserve or create more habitat or creating additional habitat nearby. If all other avenues have been exhausted, biodiversity loss on-site can be offset elsewhere, either on the developer’s own landholdings or through a mitigation banking scheme. At present, off-site compensation is valued lower than on-site using Defra’s methodology. However, where off-site measures contribute to wider Nature Improvement Areas or rewilding projects, they may have much wider biodiversity benefits, so it is important to consider all options.

The coming change in the law is not well understood, so if you are unsure how changes in environmental law will affect you or your clients (including housing developers, planning consultants and local authorities) post-Brexit, RSK Biocensus can offer advice.

Steph will be talking further about biodiversity net gain at the Planning Summit on 19 May 2020.

For more information, or enquiries, please contact Steph Wray,