Existing biodiversity credit methodologies largely fail to address uncertainty in measuring biodiversity change, which could result in misleading assessments of nature conservation and restoration projects, researchers have told Carbon Pulse.

A team of scientists led by Richard Field and Franziska Schrodt of the University of Nottingham assessed 17 biodiversity credit methodologies by examining their published specifications, and found significant gaps in how they deal with uncertainties associated with sampling errors, seasonal and day-to-day variation, and other factors.

“These uncertainties are important because we do not want credits to be issued for biodiversity outcomes that are no more than random fluctuation,” Field, professor of biodiversity science at the University of Nottingham, told Carbon Pulse.

“Nor do we want the payment to be withheld for small reductions in measured biodiversity when those reductions are only random fluctuations.”

Of the 17 methodologies reviewed by the team in March, only a few explicitly addressed uncertainty in their documentation, said Schrodt, professor of earth system science at the University of Nottingham.

Among them are the frameworks developed by Pivotal/Plan Vivo and the Wallacea Trust, as well as the Biodiversity Assessment Methodology (BAM) of the New South Wales government in Australia.

EARLY STAGES

“The market is still in the very early stages, and we cannot expect perfection from the start,” she told Carbon Pulse.

“There’s room for improvement, but everyone needs to look very carefully at this aspect, as the reputation of biodiversity credits will depend on the accuracy of the outcomes for nature that units aim to represent.”

Funded by the UK’s Natural Environment Research Council (NERC) and Economic and Social Research Council (ESRC), the project intends to flag the most critical weaknesses in existing biodiversity credit methodologies and draft guidance to enhance them.

The team is currently stress-testing a set of the assessed methodologies at two sites in the UK – the Knepp Castle Estate rewilding site and the Attenborough Nature Reserve.

The stress test process devised by Field, Schrodt, and a large team of University of Nottingham academics combines on-site measurements with semi-automated methods, including environmental DNA (eDNA) for water, bioacoustics for bats and birds, and light detection and ranging (LiDAR) data for vegetation.

“We do intensive fieldwork, looking at the plants, birds, bats, butterflies, plants, invertebrates, and other species groups. We’re assessing their abundance and richness. It’s really detailed, more than you would do for biodiversity credits,” said Field.

“We use a mix of technologies and approaches to capture biodiversity in our two field sites, applying different metrics to our data sets and examining how they respond.”

DEALING WITH BIASES

The project, which will run until Mar. 2026, focuses on assessing methodologies’ accuracy in measuring biodiversity uplift and dealing with biases.

“If you’re observing animals, you need to consider which ones just happen to be in there at the time you’re observing the site, but also take into account changes with seasons and antecedent weather conditions – if it’s been raining versus if the sun is out, for example,” said Field.

“Then, there are errors associated with sampling – so how representative your data are, or the degree to which you can infer across different habitat types. Basically, we need error bars around all of our data points.”

Schrodt said most of the biodiversity credit methodologies the team has examined so far do not account for that.

One of the most critical challenges is collecting a large amount of data, as this is key to ensuring that uncertainty is quantified properly.

“That will often not be done because it’s very expensive and takes time,” she said.

“There’s always a trade-off between the costs of continuous, high-level measurements for the duration of the programme and how valid the change inference is. We need to find the right balance.”

BIGGER CHALLENGES

Schrodt also pointed out that methodologies designed to be broadly applicable rather than focusing on a specific habitat or species face bigger challenges when tested on heterogeneous sites.

“We’ve found that they don’t work in certain circumstances, particularly in very patchy areas with loads of little mosaics of habitat,” she said.

Furthermore, Field warned against an overreliance on just one technology, including eDNA, which is being increasingly promoted as a non-invasive way to measure biodiversity uplifts from projects and other activities.

“We encountered some technical issues when testing [its use]. There is, rightly, a lot of excitement about new approaches to measure biodiversity, but the promises made are not always supported by scientific research,” he said.

“There are many things eDNA is useful for but also many you can’t do with it, yet, such as getting reliable abundance estimates.”

Field and Schrodt plan to share their findings with the main initiatives that emerged in recent years to support the development of voluntary biodiversity credits – that they both have been working with – including the Biodiversity Credit Alliance (BCA) and the International Advisory Panel on Biodiversity Credits (IAPB).

The BCA, primarily consisting of project developers but with advisory groups spanning multiple types of organisations, has recently issued a set of recommendations to enhance the integrity of biodiversity credits.

Meanwhile, the IAPB, established by the French and UK governments, carried out stakeholder consultation ahead of the planned launch of a market framework during the UN COP16 biodiversity summit, due to be held in Cali, Colombia over Oct. 21-Nov. 1.

The project led by Field and Schrodt will also involve the publication of a paper featuring the key findings as well as a set of recommendations to design robust biodiversity credit methodologies.

By Sergio Colombo – sergio@carbon-pulse.com

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