‘The trees of the late 21st century will be shaped by what we do now’

This week Royal Botanic Gardens, Kew revealed that up to half of their 11,000 trees could be at risk before the end of the century due to the effects of climate change. The findings come from their Planting for the Future report which is being used as a succession plan for trees under future UK climate conditions. We asked Dr Keith Kirby, Visiting Researcher at University of Oxford , for his expert take on the report.

Words by Dr Keith Kirby

Climate change is having an effect on our trees and woods, from changes in the time at which they come into leaf, to increased deaths from extreme weather events such as droughts and storms. These changes will become more and more apparent by the latter part of this century.

Unlike with farmland where a crop can be changed from year to year, the mature tree and woodland of the late 21st century will be shaped by what we do now: we cant wait to see whether  (against the current odds) we manage to bring climate change under control by then.

Most of our existing native trees will still be here in 2100, but not necessarily in the same places and with same abundances as now.

Kew are to be congratulated on taking a lead with this report in trying to model what trees are likely to become more vulnerable and which new species might be worth trying as perhaps more likely to be suitable for future conditions. Of course all such models and projections have weaknesses and limitations; things may not turn out as severe as expected, tree species may prove to have greater adaptability to the new conditions than we can currently predict – but things could go the other way as well.

This proactive approach is particularly important for a site such as Kew which is not just an incredibly important amenity for London and its citizens but is of world-wide importance for its scientific collections and research.  It should and is setting an example for other organisations across the country to follow.

The report notes that it is not just changes in mean temperatures or rainfall that are important, but how patterns of temperature or rainfall change within and across years. Similarly it is not just the vulnerability of the trees themselves to climate change but also the potential for new pests and diseases to emerge, or trees becoming more susceptible, because of climate stresses to existing pests.

Species from southern Europe may need to play a bigger role in the countryside particularly in the south-east of England.

The report also rightly notes that climate change will have effects on the functioning of the Gardens, from the way the watering systems work, to the energy use in the greenhouses, the risks of flooding from increased river flow or tidal surges.

Are there lessons for the rest of the country? Yes – we need to build future climate change into all our thinking. This does not mean rushing into big changes, but being aware of the direction in which things are going, and not trying to work against the grain. We need to be more flexible in our choice of trees for different situations, to encourage a wider range of species because we cannot know for certain which are going to thrive.

Most of our existing native trees will still be here in 2100, but not necessarily in the same places and with same abundances as now. Species from southern Europe may need to play a bigger role in the countryside particularly in the south-east of England.

We cannot stop change; we need to get better at guiding it. This report is a pointer to how we can approach that.

Head over to Kew's website to read the full report.