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9 Jun, 27 tweets, 14 min read

@DICE_Kent

Biodiversity Net Gain. Wish there was actual, empirical evidence about what it might really mean for your company/local authority/England’s nature?

Our @DICE_Kent-led new paper in @ConLetters reports the results of the 1st evaluation of #BNG conbio.onlinelibrary.wiley.com/doi/full/10.11…. Monster🧵

TLDR: Under #BNG, we lose open greenspace, traded for promises to deliver smaller, higher quality habitats in future. Offset system might be tiny: 95% of units in our sample delivered within development footprints themselves. Governance & the Metric need URGENT improvement.

Environment Bill is expected to mandate that all new developments under the Town & Country Planning Act achieve a mandatory net gain in biodiversity, measured using the Biodiversity Metric (3.0 released soon). Mandatory #BNG expected to be implemented nationally from autumn 2023.

A few local authorities are implementing mandatory Net Gain early. We partnered with 6 of these to track all the #BNG assessments included in planning applications for the last year, to find out what actual ecological outcomes we might expect under #BNG

Let’s look at the results of all the habitat trades promised under #BNG.

Key highlights. A) Most development is happening on cropland & pasture, which could mean that BNG is successfully directing development towards low biodv-value land.

B) Within the total area (the red-line boundary of all the developments) included in our dataset, the amount of developed urban land increases by 34% under the post-development scenario. So, #BNG is associated with quite a large land-take of open greenspace.

C) #BNG promises to deliver small increases in the area of woodland, scrubland, & ‘other neutral grasslands’, associated with big losses of cropland & pasture. Overall, our database records a 20% Net Gain according to the Biodiversity Metric 2.0.

D) The largest single contributor of biodiversity units across the whole policy (i.e. all our 6 LPAs) is ‘moderate’ condition ‘other neutral grasslands’. We’ll get to why this is concerning later.

E) 95% of biodiversity units delivered under #BNG in our sample come on-site, or on immediately adjacent land owned by developers. This means, in our sample, the ‘market’ for off-site biodv units is tiny – a worry for peeps who think BNG will fund local nature recovery networks.

OK, so these habitat trades aside, we did 2 other key things in this paper. We surveyed expert grassland ecologists to find out whether the biodiversity Metric is replicable/ open to bias; & we reviewed all the governance underpinning #BNG.

We gave 7 grassland experts a set of grassland assessments associated with BNG reports, stripping out the final condition & habitat type designation made. We asked experts to give their judgements. Experts fully agreed with BNG reports’ grassland judgements just 34% of the time.

We didn’t find a single grassland where there was unanimous agreement between our experts about what habitat type and condition score it was. These experts are the most skilled of the skilled; so this suggests Net Gain reports don’t provide enough info to properly scrutinise.

I worry about this because if the Metric is open to bias, it could have big impacts. Say, for example, a site is covered by ‘other neutral grassland’. If it's misclassified as ‘modified grassland’, all else equal, the biodiversity liability is HALVED.

OK, so next we reviewed all the proposed governance. For off-site gains (inc. gains delivered through ‘the market’), this looks promising – big promises to invest in capacity, annual monitoring & reporting, new legal mechanisms for delivering gains (conservation covenants).

But remember, in our dataset, off-site gains account for just 5% of all the biodv delivered by the policy according to the Metric! So what about the governance of on-site gains, 95% of all of the policy’s impacts?

Well, these look alarming. The govt says existing planning enforcement mechanisms are sufficient to ensure these ‘on-site’ biodv promises occur. But we know planning enforcement is reactive & stretched, so nearly all planners I speak to worry about this.

Scarier, Local Government Ombudsman suggest LPAs don’t take enforcement action except when ‘serious harm to a local public amenity’. It’s unlikely failure of habitat to reach condition score promised years ago counts – so 95% of all biodv delivered via BNG might be unenforceable!

OK. So, we now have our best picture yet of what BNG is likely to deliver for English nature, & there are some gaping areas for improvement. What’s next? Here are my personal recommendations for how we can improve biodv impacts of #BNG.

A) We need a big discussion about the governance of on-site gains. S106 agreements are often thought too cumbersome, covenants probs won’t apply to small habitat patches within developments. We need something that makes the future gains promised within developments accountable.

B) In my view, we should discuss limiting how much of our biodv liability we may meet on-site. The best places for biodv are not within development footprints; they’re in places of landscape-scale importance, possibly found in the Local Nature Recovery Network

So I would advocate that we set up more explicit mechanism for linking #BNG payments to investments in the local nature recovery networks. That would deliver the most ecologically-robust biodiversity gain.

Yes, I understand the desire for on-site compensation to enhance people’s access to greenspace. But now we have actual data on what these on-site promises are, & it’s hard to argue that grasslands & scrub within housing developments will bend the curve of English biodv loss.

C) re the Metric, Defra & NE are working on reducing ambiguities in classifications – that’s great. This needs to be accompanied by more training for ecologists doing BNG assessments & planners to scrutinise them (like this UK Hab classification training ukhab.org/training/)

With metrics summarising complex phenomena, there’s always a risk the metric becomes the be-all-&-end-all, squeezing out other relevant information. We can’t let that happen here – the Metric is a decision-aid, not proof that biodv will increase. Other ecol info still *essential*

@DICE_Kent

The stars of this project are the amazing biodiversity officers & planners who work with us – our huge thanks for their ongoing collaboration & help. On the academic side, this is a pure @DICE_Kent project from @wildbusiness lab group.

Thanks for reading!