Question 1

What is Biodiversity Net Gain?

Accepted Answer

BNG is a mandatory planning condition in England requiring most new developments to deliver at least a 10% increase in biodiversity value, measured using the DEFRA Statutory Biodiversity Metric 4.0. Habitats must be secured and managed for a minimum of 30 years. It's been mandatory since February 2024.

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Question 2

Does BNG apply to my development?

Accepted Answer

BNG applies to most developments in England that require planning permission. Current exemptions include householder applications, sites impacting less than 25 sqm of habitat, permitted development, and biodiversity gain site developments.

Question 3

When did BNG become mandatory?

Accepted Answer

BNG became mandatory for major developments on 12 February 2024 and for small sites on 2 April 2024. It will become mandatory for Nationally Significant Infrastructure Projects (NSIPs) from May 2026.

Question 4

Does BNG apply in Wales, Scotland, or Northern Ireland?

Accepted Answer

No. Mandatory BNG under the Environment Act 2021 applies to England only. The devolved nations have their own environmental legislation.

Question 5

What is a Biodiversity Gain Plan?

Accepted Answer

A Biodiversity Gain Plan is a document you must submit to your LPA showing how you will achieve at least 10% net gain. It is a pre-commencement condition — you cannot lawfully start construction until it is approved.

Question 6

How much does BNG add to development costs?

Accepted Answer

For most developments where on-site delivery is maximised, BNG adds roughly 1-3% to total project cost. Costs escalate significantly if off-site units or statutory credits are required.

Question 7

What is the difference between biodiversity units and statutory credits?

Accepted Answer

Biodiversity units are purchased on the private market from registered habitat banks and directly create real, local habitat. Statutory credits are purchased from the government as a last resort and are deliberately priced 2-4x higher than private market units.

Question 8

How much do biodiversity units cost?

Accepted Answer

Off-site biodiversity units on the private market typically cost £20,000–£35,000 per unit. Statutory credits start at an effective £84,000 per unit with the 2x spatial risk multiplier.

Question 9

What is the spatial risk multiplier?

Accepted Answer

The spatial risk multiplier (SRM) is a factor applied to off-site gains to reflect ecological risk of compensating at a distance. For statutory credits, it is a flat 2x — you must buy two credits for every one unit of shortfall.

Question 10

Can I get a refund on statutory credits?

Accepted Answer

No. Statutory credit purchases are non-refundable, except in the rare case where planning permission is revoked by the LPA. Credits are tied to a specific planning permission and cannot be transferred.

Question 11

What happens if I clear my site before the ecology survey?

Accepted Answer

If you clear habitats before the baseline assessment, the LPA may require you to demonstrate what was there before — using the pre-clearance biodiversity value as your baseline. This almost always results in a much higher BNG obligation.

Question 12

Can I start building before the Biodiversity Gain Plan is approved?

Accepted Answer

No. The Biodiversity Gain Plan is a pre-commencement planning condition. Development cannot lawfully begin until the LPA has approved it.