A new report, from Kew Gardens reveals over half of the 11,000 trees currently found at the site may be at risk by 2090.

Due to the 2022 drought that caused the loss of over 400 trees at the Royal Botanic Gardens, Kew's Landscape Succession Plan uses climate models tested by Kew experts to identify which species to plant now to safeguard UK landscapes for the future.

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.

Richard Barley, Director of Gardens at RBG Kew, says: "Planting for the Future: Kew's Landscape Succession Plan' is a crucial, and very timely step towards understanding the effects of the projected climate on our living landscapes, enabling us to implement changes that will make them more resilient.

"This is not just about Kew Gardens though; it is a broad call to diversify the plants we select for our landscapes. 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."

Landscape Succession Planning

Kew's Planting for the Future report is the first landscape succession plan to be created by a botanic garden in the UK and, due to the diversity and breadth of Kew's Living Collection, is considered to be the most expansive landscape succession plan in the world at this time, say Kew Gardens.

The botanical garden believes climate change 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.

Trees and woody shrubs, the focus of this plan, act as nature's air conditioning, effectively managing the effects of urban heat islands[4] 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.

The English Fagus sylvatica, better known as common beech, could be at risk due to climate change (credit: Royal Botanic Gardens Kew).

Key findings

Novel climate models that draw on specific projections for west London and 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.

Notably, 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 says it will continue to model and test as new techniques and data emerge, but in the short-term gardens and urban planners must prioritise planting resilient species to replace existing trees as they fail.

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, are shown to be species that should withstand projected climate conditions.

They could therefore be new additions to the treescape at Kew Gardens, and areas with similar climatic conditions - particularly urban spaces and southeast England. (See attached for full list of recommended plantings).

In addition, certain species already found in Kew's collection are shown to be resilient if they are sourced from areas within their geographic range that have similar climates to Kew's predicted future.

Examples include European species of oak and beech which have developed altered traits as a result of genetic variation within species. This occurs in response to the conditions they grow in, improving resilience to a changing climate.

Kew says while it knows the English oak will suffer from temperature and water stress as we experience hotter conditions with longer periods of drought, trees grown from oak seeds sourced from locations such as the Eurasian steppe have built-in resilience.

Dying Nothofagus summer 2022 at Kew Gardens (credit: Royal Botinc Gardens Kew).

Climate modelling combined with species mapping reveals the Hyrcanian forest of Iran and Azerbaijan, parts of South Western USA and Northern Mexico, parts of continental Europe and the Mediterranean and the Eurasian steppe to be prime locations to source resilient plant material for the UK. 

As a result, Kew is working with organisations, gardens and research partners internationally to plan seed-collecting trips to these regions.

Beech saplings from a seed collecting trip to Romania in 2023 are already growing in Kew's state-of-the-art Arboretum Nursery, and will later be tested to determine their suitability for Kew and other parts of the UK. If successful, stock will be shared with other public gardens and arboreta. 

Why is Kew leading the way?

Botanic gardens globally hold 30% of the world's known plants, including 41% of known threatened species.

What's more, new data showing the influence of London's urban heat island effect at Kew, combined with the site's alluvial, free-draining soil, positions it as one of the best-suited locations to test these trees of the future, acting as a window into the UK's future climate.

This landscape succession plan joins the efforts of botanic gardens globally to reshape planting plans in response to climate change within botanic, public and private gardens, and underscores the importance of sharing knowledge and resources across botanical institutions, local government and industry.

Tom Freeth, Head of Living Collection Support at RBG Kew, says: "This plan is a statement of RBG Kew's intention and responsibility.

"We hope others can use it as inspiration, then revise and improve it where necessary, and through that process it will provide a channel for vital collaboration.

"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."