Biodiversity rules are strangling small housebuilders

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As an architect and developer, every day I must wade through the swamp of planning rules, building regulations, financial restrictions and NIMBYism peppering the landscape of the construction sector. One set of rules in particular though, and one sub-set of those rules, grinds my goat so intensely for its sheer wanton stupidity and backward-thinkingness, that there is barely a goat left to be grinded thereafter.

I am talking, dear reader, about the Biodiversity Net Gain (BNG) rules. Now you might well agree, as I and most people do, that net-gaining biodiversity is a wonderful thing. And you would be quite right to think that. After all, who doesn’t love fluffy bunnies, bats, newts and lesser-spotted Eastern Siberian Jabberwocky caterpillars? (or suchlike)… but the very rules created to encourage the flourishing of such things are the same rules that make it impossible for SME developers.

There are two ways they do this. And do please forgive me for the nerdish hyper-technicality of this explanation. I will try to distil it down: the BNG rules basically come down to two fairly basic spreadsheets, the standard version and minor sites version. How biodiversity is measured is by a number of classifications of ‘habitat type’ if you will, each given a score. The same thing is done with trees, which have their own classification system, and also with hedges, which are measured in linear metres. You then add how many square metres of each habitat type you have on the existing site and it spits out a number. The same exercise is then done with the proposal, based on the drawings, which also spits out a number. If the second number is at least 10% bigger than the first, you’re rosy. If it’s not, you have a problem.

This is easy to do when you are a massive housebuilder with a 50 acre site and can just parcel off a couple of acres in the corner to be a meadow and ‘Sustainable Urban Drainage System’ (a pond). But when you are an SME developer and are building two or three houses on a tiny site, which is barely viable already, and where the entirety of the land must either be house, garden, driveway or road, it is not possible to carve off a whole separate block of land just for critters.

However, beyond even this, the aforementioned goat-grinding idiocy I speak of, is to do with what counts and what does not. Put simply, anything in a private garden does not count. That is, habitat that is part of an existing private garden counts on the way in, but any sort of habitat in a new private garden cannot be included in the BNG calculation. So it counts as a negative if you destroy it, but doesn’t count as a positive if you put it back.

Yes reader, you read that right, no matter how many majestic oak trees, wild flower borders, native hedgerows, beds of petunias, or darn little daisies you plant, none of it counts. ‘Why?’ I hear you ask, because under the BNG rules, any habitat that counts as a ‘significant enhancement’, must be subject to a 30-year legal agreement between landowners and the Local Planning Authority (LPA). Firstly of course this is a problem because legal agreements cannot be entered into by hypothetical future freehold purchasers before the houses have even been built. Secondly, the LPAs are of the opinion that any habitat in private residential ownership ‘cannot be assured’, in other words, their hypothetical BNG police wouldn’t be able to fine you if you remove your shrubbery. Oh the anarchy.

Even if some form of covenant was placed on each house’s title, (which would read something like: ‘thou shalt not remove the shrubbery on penalty of death’) the rules on BNG are so mind numbingly complex, that it’s no wonder it is blocking SME developers from entering the market. The sheer complexity and costs involved can only ever be navigated by massive housebuilders with in-house legal teams.

The solution is so simple it’s bonkers it hasn’t been done. Firstly, we must reinstate the BNG exemption for developments of fewer than 10 units, which ended in 2024. This would help SME developers get a foot in the door.

Secondly, we must remove the need for 30-year legal agreements around biodiversity assurance on land designated for private sale or rent. People like shrubberies. Trust that they will not destroy their own gardens, and over time, maturing trees and vegetation on private land will provide far more biodiversity benefits than the derelict sites left empty by SME developers unable to afford to build on them.

Our planning system is gummed up by dozens of requirements that are individually justifiable but collectively unbearable. BNG is just one of these. It’s time to rein them in one by one, starting here.

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