Biodiversity Net Gain – Now And Into The Future

Biopersity net gain (BNG) has become a central feature of the planning system for developers, landowners and local planning authorities.

Since February 2024,Biopersity net gain has been a mandatory requirement for most developments in England, requiring each development to deliver a measurable improvement to the natural environment.

It now plays a decisive role in planning strategy, land use and long-term site management. As it continues to evolve, understanding both the current requirements and the direction of travel is essential for anyone involved in development or land ownership. This article sets out how BNG operates in practice, what it means for developers and landowners, and what changes may lie ahead.

BNG is an increase in biopersity associated with development. This increase is measured by the statutory metric tool provided by Defra. This is set at a gain of at least 10%, some local authorities (LPA) have adopted a higher level.

As part of a planning application a biopersity metric calculation and a biopersity plan are required. This usually includes a Habitat Management and Monitoring Plan (HMMP) setting out who will be responsible for creating, maintaining and monitoring the BNG.

It is up to the LPA to consider and determine the biopersity gain and to approve the plan. Development cannot commence until this is approved. The approval is usually subject to a legal agreement: a Section 106 agreement between the LPA and a landowner and/or a conservation covenant between a responsible body and a landowner.

BNG management is for at least 30 years monitored by the developer and to a lesser extent the LPA.

Failure to meet BNG requirements may trigger enforcement action by the LPA.

Delivery:

Developers are expected to follow the biopersity hierarchy of 'Avoid', 'Mitigate', 'Compensate'. Ideally all of the BNG should be met on-site. If this is not feasible, BNG can be delivered offsite or a mixture of both. Off-site BNG can be on a developer's own land outside the development site or by buying off-site biopersity credits on the market. As a last resort statutory credits must be purchased. These credits are only available after planning permission has been granted and other options exhausted and are more expensive.

1 biopersity unit required = 2 biopersity credits.

For developers:

The main advice is to assess the requirements early in site selection and design to give a more cost-effective solution. Any red line plan for a planning application should (where possible) exclude areas of higher biopersity as this would increase the base metric.

BNG can be an asset. There is a public concern about the environmental impact of new developments. The BNG system offers a structured way to meet environmental responsibilities and offers:

• different or cheaper funding streams – Investors and lenders are increasingly looking for evidence of sustainable practices;
• reputation – a commitment to BNG can help build trust with the local community and customers;
• (for on-site BNG) developments surrounded by well-maintained green spaces are more attractive and can command higher prices or rental yields.

For landowners:

BNG offers landowners new opportunities to secure additional income. Items to consider are:

• whether or not to enter into a direct agreement to deliver BNG or to go through a habitat bank provider which may mean less return but also less risk;
• using a different entity to manage the land under a HMMP;
• constraints that such agreements place on successors in title and forward sale or dealing with other natural capital;
• whether entering into such agreements will trigger existing overage arrangements;
• tax implications as to when and how sums received are taxed (income or capital).

The future – BNG consultation:

There have been critics of BNG that state the metric can oversimplify complex ecosystems and place value on species and habitats that are in less need of saving. The reliance on off-site compensation could lead to the loss of valuable local ecosystems in exchange for biopersity gains in remote locations.

The Government published a consultation paper in summer 2025 looking at the proposal to fund strategic interventions rather than smaller bespoke plans.

On 16 December 2025 it was announced that:

• an area based exemption will be introduced for sites up to 0.2 hectares;
• measures to deal with offsite BNG delivery; and
• a further consultation on exemptions for residential brownfield development.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.