Off-site BNG could be more effective

A new report, "the Comparative value of on-site vs off-site biodiversity net gain for restoring nature" has been published, which suggests that encouraging more off-site biodiversity net gain (BNG) could see better results for nature restoration.

BNG was introduced under the Environment Act 2021 via amendments to the Town and Country Planning Act 1990. The system is designed to ensure developers leave biodiversity in a better state than it was before the development took place. To achieve this, developers must leave biodiversity at least 10% better off. There is currently, however, a preference that the biodiversity gains are delivered on the site of the development rather than enhancing off-site biodiversity.

The new report was written by a variety of contributors including Bellway Homes and was led by David Hill, former Deputy Chair of Natural England and founder of the Environment Bank. The report concluded that the "original objectives of faster development, facilitating growth and contributing substantial funding into nature restoration at limited cost to the developer, is being hampered by a preference for on-site delivery." Evidence suggests that focusing on biodiversity gains within the development site is actually poor for biodiversity and financially inefficient, partly because many developments are too small to deliver proper on-site biodiversity gain. 

In addition, the report found that:

• on-site BNG units can cost more than off-site units. Off-site units cost around £27,000 each. However, on-site delivery could cost four times the amount;
• any BNG on-site is rarely monitored or enforced. Liability for upkeep is often passed to residents or management companies. However, off-site BNG is achieved through legal agreements which include formal oversight arrangements.

With this in mind, the report suggests that:

• greater support is given to off-site BNG delivery. This could result in "larger-scale nature restoration, reduce costs and complexity for developers, and accelerate housebuilding";
• local planning authorities should promote off-site BNG delivery through local plans and nature strategies;
• local planning authorities should be given the tools to monitor and enforce on-site BNG. This should help to ensure delivery and fix any on-site BNG that fails;
• on-site BNG should have to meet the same standards as off-site delivery, such as a requirement to secure 30-year funding and professional management.

Overall, it suggests that moving to off-site BNG would actually result in more biodiversity gains. 

Mr Hill said "Most developments are too small to deliver any meaningful on-site biodiversity value through BNG, and such areas have a short shelf life because the 30-year management liabilities on developers are usually handed over to ill-equipped management companies. But, led by the policy, developers have been favouring on-site solutions".

"However, research shows this is high cost (if development land value and loss of development potential are considered) and flawed in terms of biodiversity delivery. Removing this preference, as is proposed in the recent government consultation on BNG and nationally significant infrastructure, will make it easier for developers to deliver their legal compliance by purchasing off-site BNG units. This is far better for biodiversity and cheaper for the developer. Housing residents would still benefit from managed landscaping and planting (through landscaping conditions), but without conflating this with biodiversity uplift."

For more information, see the:

• Comparative value of on-site vs off-site biodiversity net gain for restoring nature.