Better data & mapping for Ecology & Biodiversity Net Gain
- Claire Birnie
- Mar 25
- 6 min read
I delivered a seminar at Ecology Expo 2026 for freelancers & small businesses in ecology who may not have in-house GIS skills or access to geospatial specialists. The intention was to highlight the small-business data pipeline we all operate in and how we need to work together to ensure we're creating better data and mapping for Ecology & Biodiversity Net Gain
Not just for our own projects, but for everyone else in the chain, too.
Why bad GIS data is undermining Biodiversity Net Gain
BNG isn’t new anymore, but there are still a lot of companies that aren't creating digital data at all or are using inappropriate sources to do so.
GIS is a whole career and the Venn diagram of "ecologist who also knows and likes GIS" is often a small overlap. With BNG, the precision and accuracy needed requires additional knowledge and skills not necessarily needed previously.
Ecology has a high number of freelancers and small businesses, and newer techniques can be slow to filter down. This doesn't mean the larger companies are creating good data because I've seen a wide range of quality across all business sizes.
In planning, the redline boundary is usually created by the landowner, architect or developer and passed to surveyors, ecologists and the LPA.
It could be:
A DXF
Shapefile
A PDF with a line drawn on it
This red line boundary underpins all data from site selection through to completed development. And with a 10% BNG gain required, it's based on area and length calculations from that site data — so the stakes are real.
Most of the time, ecologists receive site data from their clients and aren't directly responsible for creating it (welcome to ecology, my friends!). But they’re responsible for the surveys and the BNG metric built on top of it.
So if the foundation's off, everything above it is too.
Why free mapping data isn't good enough for BNG
Do you use:
Google Satellite
OpenStreetMap
Ordnance Survey Open Data
Or any free-to-use basemapping data app to create a red-line boundary?
Well, you shouldn’t, because the difference between the visual and what’s on the ground can be up to 15 metres out!
Using Google & Open Street Map to digitise the red line by hand because your client hasn't provided usable data, you can’t say your calculations are accurate.
For example, this Google satellite image is 4.3 – 5 m out of alignment:
If you were digitising from this, you’ve built incorrect areas into the data. And you might have placed your site across another ownership boundary.
Baking in errors using data that’s not fit for purpose will expose you or your business to risks. In this example, even on a small site, you’re getting a difference that would mean the difference between your site achieving the 10% gain or not.
Ouchies!
What data you need from your clients and how to get it
Your client should provide you with the site data in a format you can use. This means geopackages, shapefiles or DXFs — formats you can open and use without having to fix them first.
The minimum you need:
Red line boundary
Surrounding area (OS MasterMap)
Existing block plans
Post-development plans
Optional extras:
Blue line boundary (or survey area) and additional land ownership data
A recent topographic survey
But don’t leave it to chance:
Ask for the data up front at quoting
Make it part of your contract
Add in clauses for responsibility for data, the standards you require and consequences if they’re not met
If your client can’t or won’t provide the data you need, purchase OS MasterMap and Land Registry and charge them.
The real cost of getting your BNG boundary wrong
If your boundary is off when you generate your habitat data, it’s gonna have a massive impact:
Your BNG data will be inaccurate
You’ll have to compensate more, costing the whole process more
You’ll likely be adding re-work down the line, costing you more time and money
The application may be refused
Oh, balls.
And we’re not being asked for our geospatial data for BNG right now either, but we will be one day. By delaying the use of GIS or creating inaccurate data, you'll be on the back foot when it matters.
I’m not trying to scare you by saying that.
But now you know better, do better!
Common GIS problems ecologists encounter (and how to fix them)
It's only a map — it'll be reet.
Wrong.
I make BNG maps most days of the week and I've seen data from multiple sources and all sizes of business. The big problem is that there's no consensus on standards, particularly in CAD.
Sigh.
With that in mind, here are the problems you'll likely encounter:
The data is MASSIVE: not the file, the geometry. It'll be in the wrong place, scale or both. Learn the affine transform function. If you have to fix their data, charge for it.
You’ll have data you don't need: architects draw everything (cheers, guys!). You don't need the kitchen sink or shower heads in your habitat map. Ask them to export only the relevant layers.
Information isn't clear: layer names like "Amenity grassland", "Wildflower grassland" or "Wet wildflower mix" mean different things to different people. I've had multiple different answers. Always ask.
So, how can we fix these?
Well, here’s a client data checklist worth stealing:
Georeferenced DXF — or better, a geopackage — in correct coordinates for British National Grid at a metre scale
Habitat areas in polygon format, not lines
No gaps or overlaps in the polygon data
Current design only, remove old iterations from model space
No map key, page border or PDF layout in the export
Make sure data within each layer is used correctly — e.g. new lawn shouldn't be sitting in the building layer
Layer names that match BNG terminology, or a PDF plan with a key, so you can translate
Target condition included, if known
Copy and paste this list of must-haves to your clients so that they can send it to theirs.
How to build GIS into your ecology workflow (not just BNG)
GIS isn't just a BNG tool.
If you build it into every part of your workflow, it'll improve pre-site assessments, quoting, reporting and data consistency across the board. And you’ll reduce the time spent jumping between different sources:
Bring in pre-survey data from the sources used in Magic Map, species records and site information so you can assess (and quote) more effectively
Create your PEA/UKHab survey data in GIS, then convert it into the BNG template to ensure consistency
Utilise GPS & UAVs in the field to take accurate locations of habitats, trees and features
Embed metadata, sources, licences and attribution in one place (essential for auditing and transparency)
One of the best things you can do is build a repeatable workflow.
Quality data in, quality data out, with templates that remove the need to hand-type anything.
Less faff, fewer errors.
Future you will be dead smug about this.
This isn't just an ecology problem; the whole data pipeline needs to improve
Although I'm focusing on ecologists, this one's for landowners, developers, architects and LPAs too; everyone in the chain needs to create accurate, usable data for those who come after them. The absence of consistent spatial data standards undermines the credibility and transparency of BNG assessments for all of us
If you’re reading this and you’re any of the above, please insist on better data standards to stop the creation of inaccurate data.
Everything you need to deliver better data and mapping for Ecology & Biodiversity Net Gain
The geospatial data behind BNG matters and most of us could be doing it better.
Get a plan for your workflow, make it repeatable, and share what you learn with others in the small business community.
Here’s how to start:
Use the Natural England Template: modify it to build a consistent, repeatable workflow. Their user guide assumes some QGIS knowledge, but it's worth the learning curve.
Get an OS Data Hub account: you get up to £1,000 of free premium data per month. Read the Ts&Cs, but this is a no-brainer!
Ask for client data upfront: before you quote, not after.
Read FRIDAS: a six-step framework for improving GIS data quality in BNG submissions. Implement it. Seriously.
Here’s a link to my talk slides and PDF on sourcing both open-source & proprietary data for your work.
And I also recommend reading these:
Whitepaper by EcoSpatial: Addressing GIS Data Standards in Biodiversity Net Gain Management
Data standard by EcoSpatial: GIS Data Standards for Biodiversity Net Gain Assessments
Don't want to faff about learning it yourself?
Then get in touch to see how I can do the mapping for you or teach you QGIS specifically for BNG. But if you DO fancy having a go yourself, you can purchase The Ecologist's Data Collection Toolkit, which includes five ready-to-use workflows for ecological surveys.
Catch ya next time,
Claire
