Concerns raised whether UK forests are genetically diverse enough to deal with climate change, pests and disease
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Scientists hope to achieve a canopy cover of 16.5 per cent over England by 2050, aiming to halt nature’s decline. Against the backdrop of such demands, policymakers are keen to know whether natural colonisation or tree planting is the way forward to achieving this goal.
In a new study published today in the journal Evolutionary Applications, scientists from the Royal Botanic Gardens, Kew, and Forest Research, have begun to answer that dilemma. The study has compared genetic diversity and comparative tree health of young British woodlands, revealing the pros and cons of planting versus natural colonisation.
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To draw their conclusions, scientists examined sites with naturally colonising and planted English oak and silver birch to compare the condition of young trees and assess the small differences in DNA between tree populations.
Genetic diversity is crucial if the UK’s forests are to thrive, as although many trees will undoubtedly fail, some will have the built-in resilience to pathogens and stressors such as drought, that can be passed on to future generations.
Researchers found both planting and natural colonisation can create healthy and diverse forests when analysed at the local level, reinforcing recent findings in a Surrey woodland where natural selection was evolving resilience to ash dieback. However, natural colonisation on its own is not a solution to increasing canopy cover, due to the small and fragmented nature of UK woodlands.
One proposal that will be put forward to the government, alongside the seed supply and nursery sector, is prioritising collecting seed from a wider range of parent trees from a variety of regions, helping to balance genetic diversity. This comes after researchers found that planted trees commonly originate from just a handful of seed sources, contributing to a lack of variability among planted woodlands.
Climate projections for the UK suggest trees planted today will face conditions that are drier and multiple degrees centigrade hotter than today. Additionally, they will face increased risks from pests and diseases.
As such, it is vital that a holistic approach, combining targeted tree planting with natural colonisation, is adopted.
‘Moving forward, it’s not just about how many trees we plant, but making sure the ones we plant are equipped to thrive in today’s environment and that their offspring can keep pace with the environmental challenges of the future,’ said postdoctoral researcher in plant health and adaptation at RBG Kew and first author of the paper Dr Guillermo Friis.
