University of Oxford
11a Mansfield Rd
OX1 3SZ
UK
11th December 2024
5 minutes read
Leading ecologists have devised a new framework to classify how biodiversity credit operators define what a unit of nature is. The new analysis demonstrates the challenges involved with devising a biodiversity credit market to fund nature recovery, and the risks of relying too heavily on ‘offsetting’.
Nature conservation faces an estimated $700 billion annual funding gap, in order to halt and begin to reverse global biodiversity loss. This means there is an urgent need to engage businesses and the financial sector in funding nature recovery.
This has sparked interest in developing a ‘biodiversity credit market’, where companies could purchase nature credits to compensate for their biodiversity impacts. There has been an explosion in the number of actors who are beginning to develop or sell biodiversity credits, however up to now it has been unclear how they are defining what ‘one unit of nature’ means, or how they are making standardised, generalisable measurements of biodiversity.
In a new review, a group of researchers have introduced a framework that defines how companies are quantifying biodiversity, detecting positive outcomes, and linking actions to investment. They use this framework to interrogate the various challenges that come with abstracting nature, in all its complexity, to one unit, and to discuss ways in which units of nature could be misleading, or unrepresentative of true biodiversity gains.
The review is particularly special because it is the first in a new series commemorating the work of Professor Dame Georgina Mace, who made foundational contributions to the field of biodiversity measurement to support international conservation policy.
Senior author Professor EJ Milner-Gulland said:
“The world’s governments have agreed to halt and reverse biodiversity loss by 2030. This requires wider society, particularly businesses, to pull their weight as well. We can’t avoid all impacts of human activity on nature, so we need to be able to compensate for the damage that we cause to nature. Our review demonstrates how challenging it is to do this via a tradeable ‘unit of nature’ and provides guidance on how to ensure biodiversity credits are appropriately designed and used, so that they can support genuine biodiversity recovery.”
Lead author Dr Hannah Wauchope (University of Edinburgh) said: “Measuring biodiversity outcomes is of increasing interest to policy and financial sectors, but it is phenomenally difficult to reduce something as complex as biodiversity to a single number, meaning there are many risks to developing a market that trades in nature. We wanted to examine how companies were attempting this difficult task.”
The framework shows how two broad approaches are being used to reduce the complexity of biodiversity at a site to a single value. The first assigns a numeric value to an area, where a higher number indicates higher biodiversity value. For instance, a site might be measured by a number of metrics such as species richness, tree canopy cover, and abundance of a target species. These numbers would be aggregated to a single value that represents ecosystem health.
The second approach classifies sites according to a binary condition – whether the ecosystem is healthy or not. For instance, the health of the forest could be measured by the presence or absence of indicator species, such as the jaguar.
Credits then measure whether sites have been conserved or restored – either demonstrating that the site has not changed (in the case of conservation), for instance, by showing that an indicator species is still present, or demonstrating that the site has improved (in the case of restoration), for instance, by measuring changes in the numeric value. Finally, credit operators adjust the number of credits they issue based on uncertainties (for example, not selling 20% of measured credits) to act as a buffer.
The researchers use this framework to highlight the various challenges that are faced in trying to represent biodiversity by a single unit. For example, biodiversity has many ways of being valuable, many of which are unmeasurable, and some of which conflict with each other (for example the cultural value of a tree species for local people and its financial value as a timber product). Even for aspects that can be measured, it is difficult to do so accurately, and to aggregate metrics in sensible ways – leaving lots of room for uncertainties or gaming to produce misleading outcomes.
According to the researchers, perhaps the biggest challenge is demonstrating that conservation or restoration outcomes happen as a direct result of investment, rather than some other reason, and ensuring that threats to biodiversity haven’t simply been displaced elsewhere.
Because of these challenges, the researchers caution against using biodiversity credits to offset a company’s impacts on the environment, particularly to support “Nature Positive” claims. Instead, companies should prioritise avoiding and reducing impacts on nature as much as possible. Credits are best used as a way for companies to demonstrate that they are making measurable, positive, contributions towards nature recovery, when they cannot do this directly (for instance, by restoring biodiversity on land they own).
Dr Hannah Wauchope said: “Biodiversity credit markets can only be positive for biodiversity if they are used with unprecedentedly strict regulation that ensures businesses prioritise avoiding negative impacts in the first place. If biodiversity credits are purchased, it should be to quantify positive contributions rather than as direct offsets.”
E.J. Milner-Gulland added:
“There may be a role for biodiversity markets in leveraging funding for nature that would otherwise be unreachable, but markets can only ever be one part of the solution for delivering effective and equitable conservation. There will remain an important role for direct investment in nature by the public and private sectors, as well as for regulation to reduce impacts on nature.”
Author
E.J. Milner-Gulland is Tasso Leventis Professor of Biodiversity at the University of Oxford. Previously she was Professor of Conservation Science at Imperial College London, and she has also held lectureships in Resource Economics and Mathematical Ecology. Her PhD, at Imperial College London, was on the wildlife trade, with a focus on ivory, rhino horn and saiga antelopes. Her research group, the Interdisciplinary Centre for Conservation Science, undertakes a wide range of research, outreach and engagement projects, on five continents and in both marine and terrestrial settings. These include developing and applying methods for understanding, predicting, and influencing human behaviour in the context of local resource use in developing countries, and working with businesses to improve their environmental and social sustainability. Her team also works on controlling the illegal trade in wildlife and on designing, monitoring and evaluating conservation interventions in order to improve their effectiveness. She aims to ensure that all the research in her group is addressing issues identified by practitioners, and is carried out collaboratively with end-users, and builds the capacity of young conservationists, particularly in developing countries. She is the founder and chair of the Saiga Conservation Alliance and has launched a number of initiatives which aim to change the real-world conversation around conservation, including the Conservation Hierarchy approach to meeting a global vision of restoring nature and the Conservation Optimism movement. She is the Chair of the UK Government's Darwin Expert Committee and a Trustee of WWF-UK
Finally, I am passionate about the conservation ecology of the saiga antelope in Central Asia, and co-founded the Saiga Conservation Alliance in 2006.
Author
My Postdoc is funded by EU Horizon 2020 project “SUPERB”, focusing on understanding and evaluating the mechanisms for financing the restoration of ecosystems across Europe. I also lead an AGILE Sprint on how the UK governments can achieve its finance goals under the Kunming-Montreal global biodiversity framework.
Author
My applied research focuses on the development and implementation of financial and non-financial incentives for conservation, with particular interest in sustainable conservation finance mechanisms linked to threatened species and wildlife that can be dangerous to live alongside, including venomous reptiles and large carnivores. Alongside my PhD, I am Director of Conservation at the Thousand Year Trust in Cornwall, where I support the restoration of Atlantic temperate rainforest. The Trust’s work has featured in outlets including the BBC, The Guardian, The Spectator, the Woodland Trust, and South West Rainforest Alliance reports. We are the winners of the 2026 Defender Awards, and 2025 winners of the On The Edge conservation fund to grow rainforest on ropes. A central ambition of my work is to create opportunities for exchange between UK restoration projects and global field sites, strengthening collaboration, innovation, and public curiosity about the natural world.
I am also a Fellow of the Royal Geographical Society, a member of The Explorers Club, and an Associate at the University of Exeter’s Centre for Ecology and Conservation (CEC).