Half of all trees at Kew Gardens at risk from climate change, report finds

UK must 'diversify the plants we select for our landscapes', warns expert at the botanical gardens in London

The Mediterranean Garden at Kew Gardens. The site is home to more than 11,000 trees. Photo: Royal Botanic Gardens Kew

One of the world's leading biodiversity institutes has issued guidelines for the replacement of northern Europe's traditionally favoured tree species, compiling a top selection of climate-resilient trees from Spain, Portugal, Mexico and China.

More than half of the 11,000 trees at the famous Royal Botanical Gardens at Kew, in London, could be at risk by the late 21st century owing to climate change, the report warned.

Native trees including English oak and common beech are recorded as dying in the hotter temperatures, and trees from warmer parts of the world will be needed instead.

Kew experts said urban planners and gardeners may need to turn to resilient species from hotter climates as the UK's weather warms.

Richard Barley, director of gardens at Kew, said the report was a crucial step towards understanding the effects of climate change on “living landscapes” and the environment.

“This is not just about Kew Gardens, though. It is a broad call to diversify the plants we select for our landscapes,” he said.

“By focusing on resilience and adaptability, we hope to show it is possible to mitigate the severe impacts of climate change in both urban spaces and gardens such as Kew.”

Climate change models show that, in 2050, conditions in London could be comparable to present-day Barcelona.

The report used modelling to assess how well species have adapted to a given climate and how that might change over time, to determine the trees that need to be planted in the UK now to protect landscapes for future generations.

The results found that if temperatures at Kew increased by 4°C, more than 50 per cent of its tree species could be vulnerable by 2090 – which is within the lifetime of most trees.

Holly could be at risk in the UK as temperatures rise. Photo: Royal Botanic Gardens Kew

Alternative modelling, which combines more conservative moisture and annual temperatures, showed one third of Kew’s trees may be vulnerable by 2090. Under both scenarios, native silver birch and holly could be at risk in the UK in areas that will have a similar climate to Kew.

Trees that could replace the dying native species include Farges’ fir and Iberian alder, from Portugal and Spain, the cherry hackberry from China, Myanmar and Tibet, and Mexico’s spoon oak.

Experts at Kew warned there was an urgent need for “succession planting” across the UK because trees and woody shrubs act as “nature’s air conditioning”, managing the effects of urban heat islands, where cities are hotter than the surrounding area.

But their long lifespan means they cannot adapt easily to such a rapidly changing climate, and many of the trees being planted in the UK are failing, botanists said.

Kew lost more than 400 trees during a drought in 2022, compared with an average of 30 lost most years. Photo: Royal Botanic Gardens Kew

Tom Freeth, head of living collection support at Kew, added that it hoped others could use the report as inspiration, and develop revisions and improvements.

“Fundamentally, we want to raise awareness of what we’re likely to experience over the next 100 years, which will be profoundly different to what we have experienced in the past and showcase some of the steps we can take to address a rapidly changing climate,” he said.

The report was spurred on by the 2022 drought in which more than 400 trees were lost at the 130-hectare gardens in west London. On average, 30 trees are lost most years.

In some good news for Kew’s collection, all of the “Old Lions” – five of the oldest trees in the garden – are expected to thrive even in the worst-case climate scenario. These are a Japanese pagoda tree, Maidenhair tree, Oriental plane, Caucasian elm and Black locust.

These trees, none of which are native to British soil, were planted in the mid-1700s when Princess Augusta created a 3.6-hectare botanic garden at Kew.