Groundbreaking ‘Planting for the Future’ report reveals over 50% of Kew’s trees could be at risk
Release date: 22 July 2024
- Kew publishes trailblazing report detailing the future of its 11,000 trees
- ‘Planting for the Future’ reveals over 50% of Kew’s tree species could be vulnerable by 2090
- Much-loved species such as oak, beech and holly at risk in the UK
- Recommendation that planting for resilience is essential nationally
- Report calls on horticulture industry and urban planners to increase diversity of trees and shrubs
A new report, published on 22 July 2024 by the Royal Botanic Gardens, Kew, reveals over half of the 11,000 trees currently found at the 320-acre Gardens in London may be at risk by 2090.
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), Planting for the Future: Kew’s Landscape Succession Plan uses novel climate models that have been empirically tested by Kew horticulturists to determine the species we need to start planting nationally now, to protect UK landscapes for future generations. 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.
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 time1.
There is an urgent need for succession planning nationally as the UK’s ten warmest years since 1884 have occurred in the 21st century2, and London’s climate in 2050 is expected to be comparable to present-day Barcelona3. 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.
Trees and woody shrubs, the focus of this plan, act as nature’s air conditioning, effectively managing the effects of urban heat islands4 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.
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 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. While we know 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.
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. Consequently, 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 species5. What’s more, new data showing the influence of London’s urban heat island effect at Kew6, 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. By harnessing collective information on site-specific plant performance, gardens worldwide can work together to safeguard plant diversity and mitigate the impacts of climate change.
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.”
Future steps
Kew’s Landscape Succession Plan aims to act as a blueprint for urban spaces, botanic, public and private gardens nationally, with the ‘trees of the future’ and geographic areas highlighted can directly influence planting decisions. RBG Kew will incorporate Wakehurst, Kew’s wild botanic garden in Sussex, by 2025. Alternatively, the methodologies can be used as a starting point for other sites to conduct their own research. The report also calls on the horticulture industry and urban planners to recognise concerns around an exclusive focus on native species and hopes this will impact urban tree planting and urban forests (parks, gardens and street trees in towns and cities).
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.”
1: Melbourne Gardens displays almost 50,000 individual plants representing 8,500 different species, which fed into their succession strategy. This strategy inspired the multivariate analyses of Kew’s woody plant collections to produce a Landscape Succession Plan. Kew Gardens contains more than 68,000 accessions of over 27,000 taxa, making it the most diverse collection of any botanic garden in the world. In turn, this has enabled the most expansive Landscape Succession Plan to be created by a botanic garden globally.
2: Kendon, M. et al. (2022). State of the UK Climate 2022. International Journal of Climatology 43(S1): 1–83. DOI: https://doi.org/10.1002/joc.8167
3: Bastin, J.F., et al. (2019). Understanding climate change from a global analysis of city analogues. PLOS ONE 14(10): e0217592. DOI: https://doi.org/10.1371/journal.pone.0217592
4: An urban heat island is an urban area that's a lot warmer than the rural areas surrounding it https://education.nationalgeographic.org/resource/urban-heat-island/
5: Landscape Succession Toolkit published by the Climate Change Alliance of Botanic Gardens (CCABG, 2022).
6: See page 10 of Planting for the Future: Kew’s Landscape Succession Plan
ENDS
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Notes to Editors:
About Royal Botanic Gardens, Kew
The Royal Botanic Gardens, Kew is a world-famous scientific organisation, internationally respected for its outstanding collections and scientific expertise in plant and fungal diversity, conservation, and sustainable development in the UK and around the globe. Kew’s scientists and partners lead the way in the fight against biodiversity loss and finding nature-based solutions to the climate crisis, aided by five key scientific priorities outlined in Kew’s Science Strategy 2021-2025. Kew Gardens is also a major international and top London visitor attraction. Kew’s 132 hectares of historic, landscaped gardens, and Wakehurst, Kew’s Wild Botanic Garden and ‘living laboratory’, attract over 2.5 million visits every year. Kew Gardens was made a UNESCO World Heritage Site in July 2003 and celebrated its 260th anniversary in 2019. Wakehurst is home to the Millennium Seed Bank, the largest wild plant seed bank in the world and a safeguard against the disastrous effects of climate change and biodiversity loss. RBG Kew received approximately one third of its funding from Government through the Department for the Environment, Food and Rural Affairs (Defra) and research councils. Further funding needs to support RBG Kew’s vital scientific and educational work comes from donors, memberships and commercial activity including ticket sales. For tickets, please visit www.kew.org/kew-gardens/visit-kew-gardens/tickets. In the first six months since implementing a new accessibility scheme for those in receipt of Universal Credit, Pension Credit and Legacy Benefits, Kew has welcomed over 88,000 visitors with £1 tickets.