Over 50% Kew’s trees could be at risk says new report on the Botanic Gardens

Image: Royal Botanic Gardens, Kew, aerial photograph

Traditional English trees not fit for new climate conditions

The Royal Botanic Gardens at Kew has published a report on the future of its 11,000 trees. The shocking findings are that over 50% of Kew’s tree species could be vulnerable by 2090 because of climate change. Much-loved species such as oak, beech and holly are all at risk in the UK.

The report calls on the horticulture industry and urban planners to increase the diversity of trees and shrubs and start planning for resilience to more extreme weather.

‘Spurred by the drought of 2022, which resulted in the loss of over 400 trees at Kew Gardens (compared to an average loss of 30 trees most years)’, the Royal Botanic Gardens commissioned the report: Planting for the Future:  Kew’s Landscape Succession Plan using novel climate models that have been empirically tested by Kew horticulturists and scientists that draw on specific projections for West London.

Acorns on Quercus robur, English oak.

Ilex aquifolium ‘Elegantissima’ on Holly Walk

Images: Acorns on Quercus robor, English Oak; Ilex aquifolium ‘Elegantissima’ on Holly Walk;Fagus sylvatica, common beech; images Kew Gardens

English oak, common beech, holly and silver birch likely casualties of climate change

The report continues:

‘Weather station records from Kew Gardens have been combined with global tree data and details of Kew’s existing plant collections, alongside empirical testing. The results reveal that over 50% of Kew’s tree species could be vulnerable by 2090 (45% are predicted to be at the edge of their known range and 9% outside of their known range based on mean annual temperature).

‘Additional modelling that combines moisture and annual temperature more conservatively predicts one third of Kew’s trees may be vulnerable by 2090, yet both scenarios reveal much-loved British natives such as English oak (Quercus robur), common beech (Fagus sylvatica), silver birch (Betula pendula) and holly (Ilex aquifolium) could be at risk in areas of the UK with a similar climate to Kew Gardens.’

Image: Fagus sylvatica, common beech, in Kew’s Arboretum

Notably, the report says, all of Kew’s ‘Old Lions’ (five of the oldest trees in the Gardens) are expected to thrive even in the worst-case climate scenario. These trees, none of which are British natives, were planted in the mid-1700s when Princess Augusta created a nine-acre botanic garden at Kew, demonstrating the benefits of diversifying collections.

Kew hopes the report will act as a blueprint for urban spaces, botanic, public and private gardens, and calls on the horticulture industry as well as urban planners to recognise concerns around an exclusive focus on native species.

Image: Dying Nothofagus, beech, summer 2022 at Kew Gardens

‘Urgent need for succession planning’

‘There is an urgent need for succession planning nationally as the UK’s ten warmest years since 1884 have occurred in the 21st century, and London’s climate in 2050 is expected to be comparable to present-day Barcelona.

‘This poses multiple threats to living landscapes and is of particular concern at Kew Gardens where the selection of plants has, in the past, been based on the assumption that site characteristics are static. Historically, species have therefore not been selected with the future climate in mind.

Image: Pagoda vista; Kew Gardens

‘Trees and woody shrubs, the focus of this plan, act as nature’s air conditioning, effectively managing the effects of urban heat islands both on people and wider ecosystems. However, their long lifespan means their ability to adapt to rapidly changing climate conditions are limited, and many of the trees currently being planted in the UK are failing.’

Resilient species they suggest include: Farges’ fir (Abies fargesii), Iberian alder (Alnus lusitanica) – native to Portugal and Spain, cherry hackberry (Celtis cerasifera) – native to China, Myanmar and Tibet, Montezuma’s pine (Pinus montezumae) – native to Central America, and spoon oak (Quercus urbani) – native to Mexico, which are shown to be species that should withstand projected climate conditions.

Image: Cedar vista; Kew Gardens

Image: Mediterranean Garden; Kew Gardens

Image: Aerial view of the arboretum

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