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Cities are becoming too hot for trees

According to a new study, climate change is threatening the health and survival of trees grown in urban areas to keep them cool, with more than half of the species already feeling the heat.

If you spent your summer in a city, likelihood is you were forced to endure intense, record-breaking heatwaves throughout July.

What you may not have been aware of is that, without trees, our efforts to stay inside and escape 40 degree temperatures would have been even more difficult.

This is because trees have a significantly positive impact on air quality and climate regulation in built-up areas that are otherwise typically devoid of vegetation.

How so, you may be wondering? For starters, the water vapour released through leaves produces a cooling effect that can reduce air conditioning needs by 30 per cent.

In addition, shaded areas created by trees provide twelve degree heat relief. Trees also promote cleaner air in densely populated boroughs where traffic flow is high and can (most importantly) lessen the blow of localised warming from concrete by twenty degrees.

Benefits of trees in cities

Yet, despite the benefits of this greenery in heavily industrialised spaces, a new study has unfortunately revealed that the heat may be damaging trees as much as humans.

According to the findings, climate change is threatening the health and survival of the trees we rely on to make cities liveable, with more than half of them worldwide (including oaks, maples, poplars, elms, pines, and chestnuts) said to have already been pushed beyond their comfort zones.

Within the next decade or so, this figure is expected to hit two-thirds, unless of course scientists act now – and fast – by better protecting existing trees and planting a much higher number of drought-resistant varieties.

‘We emphasise the importance of taking immediate actions in terms of the climate emergency to secure the survival and persistence of urban forests,’ reads the study.

‘Trees and shrubs absorb carbon dioxide and also cool their surroundings by providing shade and by pumping water up from their roots and releasing it through their leaves. This cooling effect makes people more comfortable and reduces energy used for cooling.’

‘They also purify air and water, provide habitat for native animals, and improve people’s mental health and wellbeing through connection to nature.’

Conducted by Manuel Esperon-Rodriguez of Western Sydney University, it looked at over 3,100 species of trees in 164 different cities from the US to South Africa to China, discovering that 65 per cent had exceeded safety margins for rainfall, and 56 per cent had passed the equivalent limit for temperatures.

This does not necessarily suggest that they will die out altogether, but means they are experiencing stress that affects their performance, such as their ability to store carbon and generate oxygen.

‘We need to make mindful plant choices today, so that what we plant will survive in future decades,’ says Esperon-Rodriguez, explaining that each species requires specific environmental surroundings to thrive.

‘All these benefits are mainly provided by big mature trees so we need to make sure that what we are planting today will get to that stage where they can provide all those benefits for future generations.’