The re-establishment of pre-human ecosystems, including the re-introduction of key species, "might help to reduce or offset negative impacts of intensive agriculture including: soil degradation, greenhouse gas emissions, water pollution, insect pollinator declines and a reduction in biodiversity", it says.
Both management-intensive conservation and conventional farming come with significant public costs attached, it notes, pointing out that sites of special scientific interest cost around £85 per hectare per year to maintain, while more than half of total UK farming income currently comes from EU subsidies.
While rewilding can be accomplished simply by abandoning land, "natural processes may be kick-started in several ways - for example, where seed sources no longer exist, trees can be planted and fenced off to assist vegetation succession", says the report, citing the examples of Carrifran in the Scottish Borders and Glen Affric in the Highlands.
Wetland restoration "can incorporate rewilding approaches", while: "Habitats such as blanket bog retain water and decrease water treatment costs, so water companies like United Utilities and South West Water invest in restoring them."
Reinstating natural river flows and allowing vegetation succession, as at Wild Ennerdale in the Lake District, can also have a role in flood alleviation, it adds. Meanwhile, re-established woodlands "store an additional two tonnes of carbon and 20kg of nitrogen per hectare per year, although the amount gained varied between sites", according to a study of abandoned farmland at Rothamsted Research in Hertfordshire.
While the rewilding movement is often associated with reintroduction of both carnivorous and herbivorous mammals, these "are not always feasible and some stakeholders argue rewilding can be done without them", it says. Mammals such as wolves can carry out for free tasks that currently require human input such as deer culling, while beavers' dams have been shown to provide ecosystem services by slowing peak river flows and arresting agricultural run-off, although "burrowing, tree felling and localised flooding create costs for local land managers".
The outcomes of such projects are also unpredictable and may bring ecological losers as well as winners, it says. "An evidence-based framework is needed to select species suitable for reintroduction in any given case."
Meanwhile, there remains some disagreement even about what the term "rewilding" should mean, and given how few such projects have actually been established "there is limited evidence on their impacts". The website of charity Rewilding Britain lists 13 such projects.