Many councils have been applying BNG to planning decision-making prior to it becoming mandatory. However, they are now bound to do so. Once planning permission has been granted, unless exempt, a BNG plan must be submitted to the Local Planning Authority (LPA) and approved prior to the commencement of that development. 

Practically, this will entail the developer instructing their planning consultant to produce the BNG assessment alongside the usual suite of documents submitted as part of a planning application. This should contain the policy background, followed by a condition assessment of the current site. 

The condition assessment should provide calculations for each distinct habitat within a development site, based upon the size of the area, its distinctiveness, and its condition. This provides a numerical value for the current habitat. This can then be compared against the potential future habitat be retained, lost, or enhanced. 

The next part of the assessment should set out the various ways in which the scheme will (hopefully) enhance on-site biodiversity, ranging from window boxes and border shrubs at the lower end of the scale, to green walls/roofs at the other. 

Finally, the BNG assessment should confirm the % net gain for the habitats as a whole, as well as the total biodiversity units delivered by the proposal. If the existing site is an urban or brownfield site, then it’s not uncommon for the % uplift to be in the millions, which can appear somewhat jarring. 

However, with undeveloped, greenfield sites, it’s likely that development will result in a net loss to biodiversity. The applicant will have to demonstrate how the uplift will be met by way of on-site measures, and where that’s not possible, through off-site measures. As a last resort the uplift can be achieved through purchasing statutory biodiversity credits from the government. 

While planning conditions can help secure a range of measures to make a planning application acceptable to the LPA, these usually relate to materials, methods of construction or hours of use. They are less appropriate for securing long term objectives. Planning conditions must also be directly relevant to the property in question, which as we have seen above, may not always be the case when it comes to BNG obligations. 

As a result, ongoing obligations to provide BNG may now be included in Section 106 agreements and unilateral obligations. These may include covenants given by the owner to:

• Meet and maintain the agreed BNG threshold through measures set out in a management plan, and provide calculations to the LPA
• Not occupy or permit occupation in circumstances where the agreed BNG threshold is not achieved    
• Where it fails to meet the agreed BNG threshold, to implement other specific on-site measures to ensure that it is met
• Where not possible, agree to implement off-site measures, usually payment of a contribution to the LPA, again usually prior to occupation 

To assist with the implementation of BNG regulations, the Government has simultaneously introduced the concept of conservation covenants. It was recognised that where a developer seeks to meet its BNG obligations through off-site contributions, tracts of land would have to be set aside for re-wilding. As BNG requirements seek to secure the 10% uplift for the required 30 years, this land must be conserved and maintained for the duration of that period, to ensure that the gain is realised. 

The use of conservation covenants would move us to a more regimented system for legally binding private agreements between a conservation body and the landowner. These obligations will then bind all subsequent landowners either until the specified term of the conservation covenant expires or in perpetuity.