BNG Monitoring & HMMP Delivery

What is BNG monitoring?

Once a planning permission with a biodiversity net gain condition is granted, the obligation does not end at construction. The Environment Act 2021 requires the new and enhanced habitats on a site to be managed and monitored for at least 30 years, with formal reports submitted at years 2, 5, 10, 15, 20, 25 and 30. The framework for that monitoring is set out in a Habitat Management & Monitoring Plan, or HMMP – the document that translates the biodiversity metric calculation into measurable condition targets and a fixed reporting timetable.

In other words, BNG monitoring is the long tail of a planning permission. It is what turns a calculation on a spreadsheet into a delivered, evidenced biodiversity outcome – and what makes the difference between a habitat that meets its 10% net gain target and one that doesn’t.

When does monitoring start?

In practice, monitoring begins before construction does. A robust baseline survey at the start of the programme is what every later report is measured against, so we strongly recommend that the monitoring contract is agreed before habitat creation works begin on site. Once habitats are in the ground, formal condition assessments are then carried out at years 2, 5, 10, 15, 20, 25 and 30, with interim visits in the early years where the HMMP requires it. The first full report is the year-2 submission to the Local Planning Authority – and for sites consented under mandatory BNG since February 2024, that first wave is now arriving.

What we deliver

Each monitoring visit combines drone-based survey technology with expert botanical fieldwork. A typical annual programme includes:

• Annual drone survey, including RGB and multispectral imagery, building a consistent year-on-year record of habitat extent and condition.
• Key soils information including pH, NPK and invertebrate activity indices
• Fixed-point photography at agreed stations, so visual change is documented in the same way each year.
• Botanical condition assessment and scoring, ground-truthed by qualified ecologists with specialist plant community knowledge.
• National Vegetation Classification (NVC) surveys at the agreed intervals (typically years 1, 5, 10, 15 and 30, with additional surveys triggered if condition flags slip).
• Habitat area verification and mapping, against the original metric and HMMP.
• A written monitoring report against your HMMP targets, formally submitted to the Local Planning Authority and any Responsible Body holding a covenant.
• LPA liaison and query response between visits.
• Optional digital client dashboard, giving you a clear view of current habitat condition against HMMP targets at any time.

The continuity advantage

Where Bengrove has prepared the original biodiversity metric calculation and the HMMP, we hold the baseline data, the fixed-point locations and the target condition descriptors that the rest of the 30-year programme is measured against. That continuity matters: it keeps interpretation consistent year on year, removes the risk of methodological drift between contractors, and means the year-2 report is built on exactly the data set the HMMP was written from.
We are equally happy to take over a monitoring programme written by another consultancy – we simply spend the first visit verifying the baseline before settling into the long-term cycle.

Who we work with

Our monitoring service is structured for the full range of organisations who now carry a long-term BNG obligation:

• Developers and housebuilders, where monitoring is a planning condition attached to their permission.
• Habitat bank operators, who carry a 30-year covenant obligation against every gain site they trade units from.
• Off-site biodiversity unit landowners, where covenant income depends on demonstrable delivery.
• Registered Providers and housing associations holding long-term assets with BNG conditions.
• Estates and land managers acting as off-site providers under section 106 or conservation covenant.
• Local Planning Authorities and councils running their own habitat banks or council-led BNG schemes.