More than half the tree species at Kew’s Royal Botanical Gardens are at risk of dying due to climate change, a study by the public body has found.
Founded in 1840, Kew Gardens says it houses the largest botanical collection in the world. During the drought of 2022, the botanic gardens in south-west London lost 400 of its trees. Scientists at Kew decided they needed to map and record the climate risk to the trees to see how much could potentially be lost to the changing weather in the coming decades.
The finding that half of Kew’s 11,000 trees are at risk has led the organization to write a succession plan to replace some of the trees likely to die as the climate degrades.
Kew is particularly vulnerable as many of its plantings were done at least 100 years ago, when future climate scenarios were not considered. The site is thought to have a specific and stable climate that supported trees that liked moist soil.
The UK’s 10 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. The succession plan is important as urban trees help cool the area and provide shade for the habitat during heat waves.
Climate modeling by Kew based on specific projections for West London and weather station records from the botanic gardens was combined with global tree data and details of existing plant collections, along with empirical testing.
The researchers found that more than 50% of Kew’s tree species could be vulnerable by 2090, with 45% predicted to be at the edge of their known range and 9% outside their known range based on average annual temperature.
This has implications for British natives such as English oaks (Quercus robur), common beech (Fand sylvatica), silver birch (Betula pendula) and holly (Ilex aquifolium), which may be at risk in areas of the UK with a similar climate to Kew.
Vulnerable trees that Kew has chosen to replace include those that are drought tolerant: Iberian Alder (Alnus lusitanica), native to Portugal and Spain; Farges’ fir (Abies colorsii), endemic to central China; cherry hackberry (Celtis cerasifera), native to China, Myanmar and Tibet; Montezuma pine (Pinus montezumae), native to Central America; and spoon oak (Quercus urbani), native to Mexico.
The report also states that existing species from warmer European climates, such as oaks, may be more resilient than English oaks as they have adapted to the stressors of a warmer, drier environment.
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Richard Barley, the director of gardens at Kew, said: “[The succession plan] is a crucial and very timely step in understanding the effects of the projected climate on our living landscapes, allowing us to implement changes that will make them more resilient.
“However, it’s not just about Kew Gardens; it is a broad call to diversify the plants we choose for our landscapes. By focusing on resilience and adaptability, we hope to show that it is possible to mitigate the severe impacts of climate change in both urban spaces and gardens like Kew.”
Ross Cameron, a professor of environmental horticulture at the University of Sheffield, said of the findings: “The implications of the Kew report are reasonable. It is logical to assume that tree species that prefer, for example, moist moist conditions will in the future in the south east of England can struggle.So our native Alnus (elsewhere) and Sorbus (roas and whitebarks) may find conditions too dry to succeed.”
