Updated Jun 18, 2021

Passive rewilding brings new woodlands

A new study on "Long-term woodland restoration on lowland farmland through passive rewilding" has found that over half of the trees in two new woodlands in lowland England have been planted by jays.

The study followed two fields next to Monk Woods, a nature reserve in Cambridgeshire, which had been undergoing passive rewilding for 24 and 59 years. Within six decades, native woodland restoration was approaching the structure (but not the species composition) of long-established woodlands.

During a process referred to as  "passive rewilding", thrushes spread seeds of bramble, blackthorn and hawthorn, and this scrub then provided natural thorny tree "guards" for oaks that grew from acorns buried in the ground by jays.

After this success, other sites adjacent to ancient woodland could reflect ideal conditions for restoration, with numerous seed sources of varied woody species close by.

The study published by PLOS ONE believed it provided direct evidence that passive rewilding has the potential to expand native woodland habitat at very low cost and within relatively short timescales, potentially generating valuable successional habitats for biodiversity. Passive rewilding can expand and buffer existing woods, as at Monks Wood, or create new woodland patches to diversify intensive farmland and act as sources for further expansion.

The UK's target to plant at least 12 million trees on 185,000 ha by 2042 has been predicted to cost £5.7 million for a 'Northern Forest', incorporating targeted passive restoration into such plans could result in significant cost savings.

The lead author of the study, Dr Richard Broughton of the UK Centre for Ecology and Hydrology said: "Many people don't like jays. Traditionally they have been seen as a pest. But jays and possibly grey squirrels planted more than half the trees in these sites. The jays and the thrushes basically engineered these new woodlands."

Chair of Natural England, Tony Juniper said: "In meeting our most welcome national ambition to expand woodland there is every good reason to harness the power of nature. The natural woodland regeneration at Monks Wood presents a fantastic example of what is possible – with trees planting themselves, with the assistance of the wind, birds and mammals. The feathered and furry foresters doing their work means there's no need for the usual invasive digging, plastic tubes or imported saplings.

"There is also as a result no risk of importing diseases, it's cost-free and full of wondrous wildlife, such as pollinating insects, wild plants and many birds including garden warblers, yellowhammer and reed bunting. Natural woodland recovery also catches carbon and can help reduce flood risk. It doesn't work everywhere, but it quite clearly does in so many places and I would love to see this kind of example inspiring more natural regeneration across the country."