While numerous more nuanced definitions exist, “rewilding” refers broadly to the restoration of ecosystems where nature is allowed and able to take care of itself. It’s the process of rebuilding natural ecosystems by restoring human-disturbed natural processes and is therefore sometimes referred to as “process-led nature restoration”.

Natural processes include soil formation, carbon cycling, natural flood management, grazing, pollination, and predation, many of which are driven by the free movement of species, habitat connectivity, and low human intervention.

The ultimate goal of rewilding is the restoration of functioning and resilient native ecosystems, including intact food webs. As far as possible, rewilded environments should “look after themselves” as dynamic, self-sustaining systems that require minimum human intervention and management. 

Rewilding efforts can be considered as fitting into the broader category of nature-based solutions (NbS), addressing the interlinked climate and ecological crises and realising crucial win-win-wins by sequestering carbon, restoring biodiversity, and improving human livelihoods and wellbeing.

The International Union for the Conservation of Nature offers ten basic rewilding principles alongside its definition. The following ten principles derive from a literature review, surveys, expert interviews, and practitioner workshops:

The UN Global Land Outlook estimates that up to 40% of the planet’s land surface has now been degraded by human activity. Land degradation, chiefly resulting from agriculture and forestry, is the greatest contributor to biodiversity decline and a major driver of climate change. Degradation and ecological breakdown in turn increase the vulnerability of land and dependent communities to extreme weather events associated with climate change and reduce long-term food and natural resources production.

Rewilding as a nature-based solution can realise a variety of benefits for people, the climate, and wildlife, including:

The World Economic Forum estimates that at least half of the world’s total GDP is moderately or highly dependent on nature, equivalent to ~$44T of economic value generation. Meanwhile, a new nature economy could generate up to $10.1T in annual business value and create 395 million jobs globally by 2030. In all, land-based nature-based solutions, including terrestrial rewilding, could provide around one-third of the cost-effective carbon sequestration and emissions reduction required to avert the worst consequences of climate change while reducing biodiversity loss.

As contrasted with other forms of nature restoration, such as active reforestation involving human tree planting and supporting infrastructure such as nurseries, planting equipment or machines, and fencing, rewilding may offer a more cost-effective route towards healing degraded landscapes. Activities involving tree planting and associated ground preparation for conventional reforestation can cost between $1,400/ha and $34,000/ha.

Rewilding’s process-led approach and focus on achieving self-sustaining ecosystems that require minimal human intervention can be cheaper at both the intervention and long-term management phases. Rather than seeking to design a native forest and then plant it, a rewilding approach could embrace grazing control to encourage natural recolonisation by vegetation and initiate a process of ecological succession. 

This nature-led approach is considerably more passive self-organising, and inexpensive: Studies in Brazil show that the costs of natural regeneration are 38-76% lower than for active plantation.

A meta-analysis of 133 studies demonstrated that the success of natural tropical forest regeneration surpassed active restoration efforts across major biodiversity groups and measures of vegetation structure.

Research indicates that natural regeneration can potentially absorb 40 times more carbon than plantations, with natural regenerated scrub and forest environments being considerably more resistant to climate- and disease-related stresses than planted forests.

Scaling global rewilding efforts to meaningfully address the climate-ecological crisis will require a major redirection of financial flows from nature-positive industries to regenerative land interventions. The Paulson Institute estimates that the global nature funding gap stands at roughly $700B per yea. At least this much additional finance must be directed to preserving and restoring nature to avoid the worst effects of climate change and halt biodiversity loss while preserving the natural capital upon which the global economy relies. Funding rewilding requires that nature, and the ecosystem services it provides, be appropriately valued in all economies. Governments will need to pave the way, by establishing the right regulatory environment, with intelligent incentives and market structures to catalyse financial flows from the private sector into process-led nature restoration. Rapidly growing global carbon markets could be a source of capital for carbon-negative rewilding efforts, especially as corporate sustainability leaders increasingly prioritise biodiversity and demand carbon credits from high-quality projects that deliver a myriad of non-carbon benefits. 

However, harnessing environmental markets – with carbon as the most mature of these – is impeded by the acute challenge of measurement and valuation when it comes to process-led, rather than input-led, nature restoration. Conventional afforestation projects include known inputs (eg. number and species of trees planted) and are vastly more uniform and straightforward to assess than the “messiness” of natural regeneration and the dynamic mosaic of scrubby successional habitats that generally result when nature is allowed to run its course and recolonise an area. While still deeply flawed, the conventional tools of forest carbon quantification – the tape measure and biomass equations – are considerably more suitable to a plantation than to a natural forest or scrubland.

The issue of reliably measuring carbon and climate benefits in rewilding projects presents an enormous barrier to financing these projects with carbon credits and other forms of impact capital.

More generally,  a greater understanding of the interaction between rewilding and wider ecosystem service delivery is sorely needed.

Current evidence gaps, many stemming from the challenges of measurement and monitoring, mean that rewilding is not adequately represented in national greenhouse gas abatement plans nor prioritised as a viable solution in climate and land use policies. 

As a result, there is a clear need to quantify the effectiveness of rewilding as a nature-based solution to climate change. 

Robust, high-integrity estimates of rewilding habitats’ carbon sequestration and storage potential could allow process-led nature recovery projects valuable access to carbon markets and greater importance in evidence-based environmental policymaking. 

This would facilitate new private and public routes for financing such projects, helping this type of project to proliferate and scale.

Treeconomy’s work on the Knepp Estate and Knepp Wildland Carbon Project seeks to address precisely this issue through the application of advanced sensing and digital carbon measurement techniques.

The Knepp Estate, located in southern England, is a world-famous rewilding project.

The main rewilding area, known as the “Southern Block” comprises 430 hectares. This land was previously farmed conventionally for arable crops and dairy until around 2002, at which point the area in agricultural production was reduced on a field-by-field basis until all farming had ceased by 2006.

Former agricultural fields were left to be naturally colonised by grasses, shrubs, and trees. Soils depleted by decades of exploitation began to repair themselves. Seeds from existing hedgerows, grass margins, and woodland areas continued to colonise the ex-arable fields, with dispersal supported by a growing number of animals, including field mice and jays.

A deer fence was erected in 2009 and a variety of free-roaming herbivores were introduced into the newly-enclosed block, including fallow deer, Old English longhorn cattle, Exmoor ponies, Tamworth pigs, and red deer. This introduction of naturalistic grazing and browsing influenced the growing vegetation, creating a complex mosaic of habitats that were then occupied by a range of species, many of them nationally threatened and dwindling elsewhere across the UK, including turtle doves, and Purple Emperor butterflies.

Within 20 years, Knepp’s embrace of process-led nature restoration transformed an ecologically impoverished farm into a thriving ecosystem. Today, Knepp has one of the highest densities of breeding songbirds and is recognised as a nationally important site for nature. Meanwhile, Knepp Estate more than tripled its number of employees, becoming a hub for rural economic development.

Through ongoing surveying and observation demonstrated the remarkable biodiversity uplift achieved through Knepp’s rewilding transformation, the climate benefits of carbon sequestration in new vegetation had never been measured.

Though abundant natural regeneration was obvious, quantifying the carbon in this biomass was not possible via conventional manual methods, such as plot-based sampling with tape measurement of tree diameters. Such approaches derive from the commercial timber industry and were wholly inappropriate for assessing carbon stocks in the dynamic mosaic of scrubby successional habitats that had formed over two decades of natural regeneration across the Southern Block. The Knepp Wildland Carbon Project was initiated to address this crucial data gap and quantify the carbon sequestration associated with process-led nature restoration, thereby laying the groundwork for access to carbon finance.

The project partnership comprised Treeconomy, global sustainable development consultancy Arup, pioneering rewilding project, the Knepp Estate, natural capital company, Nattergal, as well as soil carbon startup, Agricarbon, and experts from Queen Mary University of London’s School of Geography. Treeconomy leveraged existing capabilities in machine learning, 3D remote sensing, and nature-based carbon assessment to deploy a pioneering approach to measure the carbon in woody biomass across woodland, scrub, and hedgerow habitats.

You can access the full Knepp Wildland Carbon Project report here.

Treeconomy is the UK’s rewilding carbon leader, having surveyed thousands of hectares across a variety of inspiring nature restoration projects.

We are trusted by landowners, natural capital investors, government agencies, carbon standards, and corporate carbon buyers. 

We offer best-in-class natural capital baselining and carbon measurement services with a multi-award-winning scientific team and our Sherwood nature-based project monitoring platform. 

Our dedicated natural capital team works to facilitate confident investment into a growing portfolio of fully-monitored nature projects on our marketplace.

We have worked with the UK’s leading rewilders, including Nattergal, Highlands Rewilding, Heal Rewilding, Wildlife Trusts, and Wilder Carbon.

Get in touch today for a free demo or consultation.

Burrell et al.,2024. The inadequacy of current carbon storage assessment methods for rewilding: A Knepp Estate case study: https://besjournals.onlinelibrary.wiley.com/doi/10.1002/2688-8319.12301

Carver et al., 2021. Guiding Principles for Rewilding: https://conbio.onlinelibrary.wiley.com/doi/10.1111/cobi.13730

Crouzeilles et al., 2017. Science Advances. Ecological restoration success is higher for natural regeneration than for active restoration in tropical forests.  https://www.science.org/doi/10.1126/sciadv.1701345?sm_guid=MjUyNTY2fDB8LTF8fDE4ODMxMTF8fDB8MHw1ODE1MDY2MnwwfDB8MHx8MjE2ODg50

Di Sacco et al., 2021. Global Change Biology. Ten golden rules for reforestation to optimize carbon sequestration, biodiversity recovery and livelihood benefits. https://onlinelibrary.wiley.com/doi/10.1111/gcb.15498#gcb15498-bib-0102

Grantham Research Institute on Climate Change and the Environment, 2023. Exploring the carbon sequestration potential of rewilding in the UK: policy and data needs to support net zero: https://www.lse.ac.uk/granthaminstitute/publication/exploring-the-carbon-sequestration-potential-of-rewilding-in-the-uk-policy-and-data-needs-to-support-net-zero

IUCN, 2022. Rewilding Principles: https://www.iucn.org/sites/default/files/2022-10/principles_of_rewilding_cem_rtg.pdf

Knepp Wildland Carbon Project report: https://www.arup.com/perspectives/publications/research/section/knepp-wildland-carbon-project

Paulson Institute. Financing Nature: Closing the Global Biodiversity Financing Gap: https://www.paulsoninstitute.org/wp-content/uploads/2020/10/FINANCING-NATURE_Full-Report_Final-with-endorsements_101420.pdf

Rewilding Britain, 2023. What is rewilding? https://www.rewildingbritain.org.uk/why-rewild/what-is-rewilding

UNEP, 2023. State of Finance for Nature: https://www.unep.org/resources/state-finance-nature-2023

UNCBD, 2020. Global Biodiversity Outlook 5: https://www.cbd.int/gbo/gbo5/publication/gbo-5-en.pdf

UNCDD, 2022. Global Land Outlook: https://www.unccd.int/resources/global-land-outlook/overview\

World Economic Forum, 2020. New Nature Economy report series: https://www.weforum.org/publications/new-nature-economy-report-series/