Natural colonisation establishes most quickly where there is a nearby seed source, such as a woodland edge or hedge line, as in this 18 year old example on a Norfolk farm.
Photo: Elliot Colley.

By Bianca Ambrose-Oji, Maddy Pearson, Katy Spencer, Elliot Colley, Matt Guy, and Kevin Watts.

Read the full paper here.

Governments around the globe have announced climate and biodiversity emergencies. Increasing tree cover has been identified as one response to meeting these challenges. This can be achieved through different approaches, including active tree planting, or being more passive and letting nature do the work through ecological processes. Whilst we know a lot about why land managers might plant trees, there is much less known about whether, and why, they might use other approaches. This is information is important to those wanting to promote natural approaches for expanding tree cover to the widest possible audience.

We spoke to nearly 100 private and public landowners and managers, as well as their advisors, to find out more about what kinds of woodland creation approaches they found acceptable on their land.  We included land managers with different objectives such as conservation, timber production and providing public amenity, to get a representative view.  We wanted to know if they recognised natural woodland creation processes (what we call “natural colonisation”) on their land.  We asked them to tell us what benefits they were looking for when choosing their approach to woodland creation.

They told us a lot about the risks they perceived as much as the benefits. They saw natural processes as good for biodiversity, but they worried about the species of trees that would establish themselves, the time it would take, and negative perceptions people might have about the land looking abandoned during the process.  Tree planting was seen as good for carbon sequestration and timber production, but costs of planting and uncertainty about tree resilience to climate change were seen as risks. Interestingly, about 65% preferred mixing tree planting and natural colonisation, what we call “hybrid approaches”, to balance perceived risks and benefits.

Policy makers and advisors need to better understand the risks influencing land managers decisions to use natural colonisation, and respond by building advice offering mitigation measures, including hybrid techniques. The design of other support, e.g. grants, needs to build in flexibility to address risks and allow hybrid approaches to increase the certainty of outcomes.