Projects to rewild habitats offer similar CO2 sequestration rates as new native woodland initiatives over a 19-year period, in addition to better biodiversity outcomes, according to a study of an estate in southern England.

Rewilding habitats, where nature restoration has occurred with minimal human intervention, leads to the sequestration of large volumes of CO2 in the first decade of projects, a report on the Knepp Wildland Carbon Project in Sussex has found.

Over a 19-year duration, the sequestration rates of ‘rewilding habitats’ were found to be 5.2 tonnes of CO2 per hectare per year (t/CO2/ha/yr), around 86% of those estimated for new native woodland at 6.05 t/CO2/ha/yr, as estimated by the Woodland Carbon Code.

The figure for rewilding habitats is estimated from carbon stored in above-ground woody biomass, and in new soil carbon, excluding the carbon in root biomass. To address the latter, a University of Oxford study is underway to explore the carbon sequestration of shrub.

In addition to locking away carbon, rewilding offers benefits including soil restoration, reduced flood risk, wildlife restoration, and economic opportunities like ecotourism.

The report was led by a research partnership of Knepp, Nattergal, and sustainable development consultancy Arup, in addition to Treeconomy, Agricarbon, and Queen Mary University of London.

Nattergal, founded by the Knepp team, is a nature restoration company aiming to deliver nature recovery at scale in England through the sale of ecosystem restoration services.

CREDIT POTENTIAL

There is significant potential for ‘rewilding carbon credits’ to be generated and sold within the UK’s voluntary carbon market (VCM), with the biodiversity co-benefits allowing for such credits to be sold at a premium, the study found.

However, “the lack of standardised monitoring, reporting and verification (MRV) protocols, the remaining uncertainty around sequestration rates, and carbon pricing within the VCM are currently hindering major investment into ‘rewilding carbon credits’”.

Improved understanding and support for rewilding is needed for the UK to achieve its statutory nature targets – to protect and conserve a minimum of 30% of land and sea for biodiversity by 2030, in line with the Kunming-Montreal Global Biodiversity Framework of Dec. 2022 whereby 196 countries pledged to halt and reverse nature loss by 2030, said the report.

The UK government last week announced £25 million in funding towards 20 projects aimed at protecting and restoring wildlife habitats spanning 3,300 ha, including grasslands, wetlands, woodlands, saltmarsh, hedgerows, and heathlands.

The UK government also plans to launch a consultation to explore how the nascent international biodiversity credit markets can “mutually reinforce” existing carbon credit markets.

BACKGROUND TO KNEPP

The 1,400-ha Knepp Estate has transitioned from intensive agriculture to full-scale nature restoration over the past 20 years, using a ‘process-led’, non-goal-orientated approach where nature takes control as far as possible, known as ‘rewilding’.

The main area of rewilding at Knepp, known as the Southern Block, comprises about 430 ha of low-lying clay that was conventionally farmed until 2002, at which point it was gradually transitioned to nature recovery with the introduction of free roaming herbivores like fallow deer.

Supported by Countryside Stewardship funding from the UK government, the project has enabled the return of wildlife, such as critically endangered nightingales and turtle doves, in addition to restoring rivers and recovering soil, turning Knepp into an important carbon sink.

The Knepp Wildland Carbon Project initially set out to produce a carbon protocol for rewilding projects across the UK, funded by the Natural Environment Investment Readiness Fund (NEIRF) in 2022. It evolved to focus on the storage potential of these habitats when it found there were too many data gaps for the creation of a market-ready protocol.

The Southern Block of Knepp Estate has been used by the project as a real-world example from which carbon measurements could be taken, using lidar, drones, and soil sampling techniques.

Knepp environmental gains. Source: Knepp Wildland Carbon Project

SCALING UP REWILDING

The co-benefits of process-led nature restoration should be adequately priced into the cost of rewilding carbon credits by policymakers and the VCM, because these credits support projects that deliver greater biodiversity uplift than woodland carbon projects alone, the report said.

Key barriers identified by the study preventing rewilding projects from generating certified carbon credits are:

• A lack of appropriate carbon standards for nature-led projects
• A lack of clarity on future policy around the stacking and bundling of ecosystem services
• An insufficient carbon price, not fully reflective of the biodiversity benefits and additional ecosystem services of process-led nature restoration
• A lack of robust dataset for rewilding habitats.

AVAILABLE STANDARDS

The UK’s two domestic carbon standards, the Woodland Carbon Code (WCC) and Peatland Carbon Code (PCC) are specifically targeted for their eponymous land types and are not applicable for the complex ecosystems prevalent in rewilding systems, said the report.

Industry initiatives, such as the Environmental Farmers Group, are cropping up to help farmers navigate the complexity of these markets and achieve fairer market prices.

Instead, a monitoring programme is needed to capture everything that happens in the dynamic nature restoration process, with a transparent measurement and data collection process, Ivan de Klee, head of natural capital at Nattergal, told Carbon Pulse.

The Wilder Carbon Standard has emerged as a mechanism to allow for the sale of carbon credits from rewilding projects in the UK, and is a “more flexible methodology and standard than some of the other carbon credit providers”, said the report.

Wilder Carbon “includes a quantification of biodiversity and ecosystem services benefits within the carbon credit” and only allows approved buyers with a net zero pledge and ethical practices to purchase the credits.

Credits from Wilder Carbon are priced higher than those of many others on the market, at £75 per tonne of CO2.

However, soil carbon estimates for Wilder Carbon “are incredibly low compared to the data revealed in this NEIRF project” and “scrub habitat has to have a 40% buffer applied”, which restricts the commercial opportunity, the report said.

Meanwhile, Verra’s release of its new methodology for Afforestation, Reforestation and Revegetation (ARR) would be compatible with rewilding projects that include scrub, wood pasture, and woodland, but can be very expensive and require an experienced project developer, it added.

The “new ARR methodology is not well established and requires projects to be developed over a large area to ensure cost effective returns”.

TRANSPARENCY IS KEY

“The transparency of what we’re calculating and how we’re calculating it” is fundamental to the development of a biodiversity-led carbon credit market, “because we need to be able to repeat and replicate what we’re doing and build this into existing processes and systems”, said Tom Butterworth, nature lead for Arup, who worked on the study.

There is a “massive gap” in what is covered by the UK’s national codes for carbon, he said, referring to the WCC and PCC. It should not be the remit of one organisation or another to solve it, but rather a coordinated approach is needed across the whole of the UK and perhaps Northern Europe.

The ability to be able to measure and accurately reward soil carbon in the Northern hemisphere is particularly critical, because further away from the Equator, more carbon is stored in the soil compared to above-ground in vegetation, said Butterworth.

“Soil acts as a very rapid sequestration tool” in the first 10-20 years of a project life, and so we need a coherent way to be able to measure it – this report goes a long way to being able to do so, said de Klee.

By Bryony Collins – bryony@carbon-pulse.com