It is an unseasonably warm day in September, at the end of a very long, very hot summer. is sitting in the passenger seat of a golf buggy, staring at a stand of withering beech trees in the middle of Kew Gardens, in south-west London. Where there should be a show of dancing green leaves, there are only wisps of brown curls amid bare branches.
Martin is responsible for tending and curating the 11,000-strong tree collection at Kew. But successive heatwaves and a severe drought have been catastrophic for his wards this summer. Across Kew, branches stand bare against clear blue sky and leaves crunch under the feet of visitors, as the stressed trees shed their leaves early in an effort to survive the drought and heat.
Martin estimates that at least 400 trees, if not more, will have died this summer at Kew, equal to the record mortality seen in 2022. 鈥淚t鈥檚 disheartening and very distressing to see the amount of tree loss we鈥檙e seeing and how the plants, trees are struggling,鈥� he says. 鈥淚鈥檇 be surprised if I鈥檝e got any common beech left in this garden, because they are all very, very poorly. Because they can鈥檛 deal with the heat.鈥�
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It isn鈥檛 just in Kew Gardens that the trees are struggling. It is the same story across south-east England. Trees in urban areas are worst affected, because alongside the drought, they are battling higher air temperatures, pollution, soil compaction and other urban stressors. Mature city trees are more resilient, but younger specimens are in dire straits, threatening efforts to provide more shading and greenery in cities.
The charity says half of the young saplings it has planted in London in the past year died over the course of this summer. Survival rates should normally hover around 80 to 90 per cent. 鈥淚鈥檝e never seen anything like it,鈥� says from the charity. 鈥淚鈥檝e walked around different sites, and you can see half the trees are dead and the other half are struggling. This summer has been very intense for the trees and very stressful for our team.鈥�
The loss of trees in parks and streets doesn鈥檛 just mean a loss of beauty. London鈥檚 trees help to cool the city by up to 5掳C, from environmental charity Friends of the Earth shows, and provide vital shading for humans and wildlife on hot days.
Things will only get worse for city trees as summers become hotter and drier. England鈥檚 climate is shifting rapidly, and the south-east is moving from a moist, temperate climate to a semi-arid one, says Martin. Summers will become hotter, but rainfall levels will flatline. 鈥淭he plants need more water to deal with the heat, but there isn鈥檛 any more water coming,鈥� he says.
Although temperatures will also increase in the north and west of the UK, rainfall will keep pace, maintaining the temperate conditions native trees are used to. 鈥淲e have to get our mind set that, although we鈥檙e a small island, we鈥檙e going to have two very different ecosystems,鈥� says Martin.
Victorian city planners lined London鈥檚 main roads with limes and London plane trees, while species such as oaks, birch and ornamental cherries and magnolias adorn parks, gardens and squares across the capital. These trees simply won鈥檛 be able to cope with the looming transition. published by Martin鈥檚 team in November 2025 reports that 73 per cent of London鈥檚 public trees will die or struggle to thrive under the climate conditions forecast for the city in 2090, assuming continued high greenhouse gas emissions. Just 0.38 per cent of its current trees are considered highly suitable for such a future.
Over the coming decades, growing numbers of large specimens will succumb to the heat, says Martin. 鈥淚 think we will see quite a few mature trees that will have a big impact on our landscapes disappear,鈥� he says. 鈥淭rees that we鈥檙e used to seeing 鈥� like your birch, your oak and your beech, they鈥檙e really struggling 鈥� we will see them gone from our landscapes.鈥�
Against that backdrop, maintaining London鈥檚 current canopy cover 鈥� let alone increasing it as mayor Sadiq Khan is targeting 鈥� looks like a Herculean task. A massive replanting programme will be required over the coming decades, says Martin, which should be staggered to prevent the disappearance of cooling and shading canopy all at once. 鈥淚 do think we are going to have to accept that some of the older trees that are really sickly, we鈥檇 be better off moving them out, removing them proactively, then planting the next generation,鈥� he says. 鈥淲e are getting to the stage where we鈥檙e going to have to start seeing proactive management of treescapes because we need to phase in these plants that are going to be more suitable.鈥�
South-east England will need trees that can cope with heavy autumn and winter rainfall and cold snaps, as well as prolonged heat and drought over the summer months. The team at Kew is turning to the forests of the Eurasian steppe for answers, collecting seeds from the lime, hornbeam and beech growing there to assess their suitability for the future British climate.
The trees that thrive on the steppe are slow-growing and use water efficiently, says Martin. That might mean less 鈥渟howy鈥� displays of spring blossom on city streets, with the focus shifting to species that conserve their energy to cope with drought stress. 鈥淏ecause our climate has shifted so fast and we鈥檝e gone into this hot, dry summer with drying air, that鈥檚 why we have to look at these more boring plants that are more invested in their water safety,鈥� he says. But these tougher varieties will still provide the shading, cooling and habitat services we demand from urban trees, he points out.
Power at Trees for Cities says the charity is changing the species mix it plants to include more drought-tolerant trees, such as ginkgo or the European nettle tree.
Finding the right trees is only part of the challenge. Ensuring that young saplings planted today survive into adulthood is becoming tougher every year. Trees for Cities is increasing its aftercare and watering regimes to help saplings through their first few summers. But local authorities need more funding and support to do the same, says at UK-based urban forestry firm Treeconomics. 鈥淭here鈥檚 always capital funding, so you can buy the trees, but you can鈥檛 necessarily pay to maintain them,鈥� he says. 鈥淢aybe we could be better at planting fewer trees, but looking after them.鈥�
