Biodiversity Net Gain (BNG) is a conservation policy model that requires development projects to leave nature measurably better than before. By mandating a net increase in habitat quality, BNG creates a market where ecological restoration, including rewilding, becomes a funded land use.
10%+Minimum net gain required in England
30yrMinimum habitat maintenance period
2024Mandatory for major developments in England
Quick Facts
What it isA planning requirement that habitat must end up better off than before development
Measured inBiodiversity units, based on habitat type, condition, and strategic importance
Who can sellLandowners, farmers, and conservation or rewilding projects creating qualifying habitat
Regulator (England)Natural England, via the statutory BNG register
Key debateWhether off-site credits risk greenwashing or location mismatch
How Biodiversity Net Gain works
Biodiversity Net Gain is a rule that says when new buildings, roads, or other development projects are built, nature must end up better off than it was before. If a project damages wildlife habitat, the developer has to create or restore even more habitat somewhere else, enough to leave a net increase in biodiversity.
In simple terms
If a project takes away 10 acres of healthy habitat, it must create more than 10 acres of equal or better habitat in return.
To make this work, ecologists measure the value of habitats using a standardized scoring system. Developers then have to replace what was lost and add extra value on top. If they cannot do it on the construction site, they can pay for habitat restoration on other land.
This creates a new way to fund rewilding and ecological restoration, because landowners and conservation groups can be paid to restore wetlands, woodlands, grasslands, and other high-value habitats that boost biodiversity. In effect, BNG turns nature recovery into something that can be planned, measured, and financially supported, helping wildlife and ecosystems rebound even as communities grow.
On-site
habitat improvements occur within the development boundary itself
Off-site
gains are delivered on separate land, often through rewilding or conservation projects
Frequently asked questions
Biodiversity Net Gain (BNG) is a policy approach that requires development projects to leave nature in a better ecological condition than before construction. Developers must measure habitat value, account for losses, and deliver a net increase in biodiversity through on-site restoration, off-site habitat creation, or the purchase of biodiversity units.
A biodiversity unit is a standardized measurement of habitat value. Units are calculated using factors such as habitat type, condition, distinctiveness, and strategic importance. Higher-quality or rarer habitats generate more units, while degraded or common habitats generate fewer.
Developers can meet BNG requirements by improving or creating habitat on the development site, funding habitat creation off-site on other land, purchasing biodiversity units from approved providers, or buying statutory biodiversity credits as a last resort.
Rewilding projects can generate biodiversity units by restoring high-value habitats such as wetlands, woodlands, species-rich grasslands, and riparian corridors. Developers purchase these units to meet BNG obligations, creating a long-term revenue stream for ecological restoration.
Landowners, farmers, conservation organizations, and rewilding projects can sell units if they restore or create qualifying habitats, follow approved management plans, commit to maintaining the habitat for 30 or more years, and register the site in the official BNG register.
Most BNG frameworks require habitat gains to be legally secured for a minimum of 30 years, ensuring long-term ecological benefits and stable funding for restoration projects.
On-site BNG means habitat improvements occur within the development boundary. Off-site BNG means gains are delivered on separate land, often through rewilding or conservation projects. Off-site BNG is used when on-site space is limited or when higher-value habitats can be created elsewhere.
In many regions they can, but with restrictions. Some habitats can generate both biodiversity units and carbon credits through stacking, while others require choosing one market through bundling. Rules vary by jurisdiction and registry.
BNG is typically regulated by national or regional environmental agencies, local planning authorities, independent ecological assessors, and official biodiversity unit registries. In England, for example, Natural England oversees the statutory BNG register.
Common concerns include greenwashing if developers rely too heavily on off-site credits, time lags between habitat loss and restoration maturity, location mismatch when gains occur far from impacted communities, metric limitations that may oversimplify ecological complexity, and access barriers for small landowners.
BNG does not prohibit development, but it raises the ecological cost of habitat loss. By requiring measurable net gains, it incentivizes developers to avoid high-value habitats and invest in restoration.
No. Offsetting aims for no net loss, while BNG requires a net positive outcome. BNG also uses more rigorous metrics, longer monitoring periods, and stronger legal protections.