A new study by scientists at the Royal Botanic Gardens, Kew, and Forest Research has shed light on the strengths and weaknesses of planting versus natural colonisation when it comes to creating resilient woodlands.

The research, published on 27 August in Evolutionary Applications, is the first from the Centre for Forest Protection (CFP), a joint venture between Kew and Forest Research funded by Defra.

With England aiming to reach 16.5% tree canopy cover by 2050, the findings provide timely insights for policymakers and land managers.

Scientists compared young oak and birch trees in planted and naturally colonised sites, analysing their health and genetic diversity.

Both methods can create healthy woodlands with strong local adaptation.

However, inbreeding was found to be twice as high in naturally colonised sites, due to the isolation of many UK woodlands.

Planted trees, by contrast, often come from too few seed sources, making them more genetically uniform than expected.

The new research was a joint venture between Kew and Forest Research funded by Defra (credit: RBG Kew).

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Dr Guillermo Friis, Postdoctoral Researcher at Kew, explained: "Across the country, trees of the same species have slight genetic differences that help them thrive in their local environment.

"Protecting this diversity is vital if our trees are to respond to climate change. By choosing seed sources carefully, planting can help grow forests that stay healthy and adaptable over time."

One of the study's key recommendations is to expand the range of seed sources used in planting projects.

Kew's UK National Tree Seed Project has already pioneered this approach, collecting seeds from across regions to ensure balance between genetic diversity and local adaptation.

Dr James Borrell, Research Leader at Kew, commented:

"If seeds come from the same small number of stands, we risk eroding the genetic diversity of our native trees.

"Working closely with nurseries, we can ensure saplings have the resilience they need for the future."

While overall tree health was rated as good, the researchers noted higher levels of leaf pathogens on planted birch compared with naturally colonised birch.

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Kew say a follow-on project called SUPPoRT (SUstainable Plant Provenancing for Resilient Trees) will investigate further.

Dr Nadia Barsoum, Senior Forest Ecologist at Forest Research, added: "Our findings suggest that a hybrid approach – combining natural colonisation with carefully sourced planting – could be the most effective way to grow forests resilient to pests, diseases and climate change."

Dr Friis concluded: "It's not just about how many trees we plant, but whether the ones we plant are equipped to thrive in today's environment – and whether their offspring can keep pace with the challenges of the future."

To read the new study in full, click here.

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