The UK should turn to climate-resilient hybrid trees as temperatures rise, Kew Gardens advises. Kew Gardens, a lush, green oasis on the outskirts of London listed as a UNESCO World Heritage site, is facing significant challenges due to climate change.
In 2022, a drought hit the region, marking the hottest year on record in the UK, with temperatures soaring above 40 degrees Celsius. Water levels deep below the surface of the soil dried out, forcing some trees, more used to temperate climates, to shed their leaves. Experts estimate around 400 trees were lost due to this extreme weather.
Tom Freeth, Head of Living Collection Support at Kew Gardens, explained that this loss was much higher than the typical annual loss of 20 to 40 trees. “This is like a much slower moving event,” Freeth said, noting that the impact of the drought continued into subsequent years. Spurred by this loss, scientists at Kew have been investigating how their trees will fare in the long term.
Using new climate models, they have assessed how the plants will respond to rising temperatures and changing weather patterns. The result is alarming: up to 50 percent of the garden’s trees could be vulnerable to climate change by 2090. There are around 2,000 species at Kew, but if mean annual temperatures rise, some could be pushed beyond their natural range.
“If we take the worst-case prediction offered up by these globally available models, it’s going to get up to four degrees warmer in terms of mean annual temperature,” Freeth stated.
Hybrid trees for future resilience
The patterns of rainfall may also become more erratic, impacting the trees’ health.
Predictable wet seasons could give way to random dry spells, putting all plants at risk throughout the summer. The findings have been published in a new report called “Planting the Future,” released today (22 July). Since completing the study, Kew scientists have investigated whether precipitation levels could mitigate the negative impact of rising temperatures.
They now believe increased rainfall could lessen some of the impact, but still predict that up to a third of the trees could no longer grow in the region by the end of the century. This includes beloved species like the English oak, beech, birch, and holly. Kevin Martin, Head of Tree Collections at Kew, emphasized the need for diverse planting strategies.
“When we’ve done the research, it’s as much as one third of this living collection that is going to be at risk due to climate change,” he said. “The English oak, for instance, will struggle as it is drought-sensitive.”
The report urges the horticulture industry and urban planners to increase the diversity of tree species and shrubs. New types of plants may be required to keep Kew Gardens, and South East England in general, green.
At Kew, they are working to identify which trees will cope better with hotter temperatures and less predictable rainfall. Martin showed a sapling that is a hybrid between the common beech and the Oriental beech, indicating such hybridization could be a key strategy for future resilience. Botanic gardens globally hold 30 percent of the world’s known plants, including 41 percent of known threatened species, highlighting the importance of these institutions in conserving global biodiversity amidst changing climates.
