City Trees

Life is not easy for city trees and, like honey bees, they are often unnoticed and unappreciated.  

 

Hemmed in by buildings and roads, urban trees exist in a polluted environment with limited resources.  When it rains the trees are either inundated with runoff or left thirsty under concrete paving or tar macadam roads that prevent water penetration.  Their roots are squashed into heavily compacted soil  with little space to expand before  bumping into bricks or concrete. 

Like city residents, most of these trees live in cramped conditions, they are riddled with infectious diseases and suffer from chronic stress.  In this unnatural setting they tend to live fast and die young, with mortality rates nearly twice as high as those in rural areas,.  

Writing for the BBC and with specific reference to the British capital, reporter Zaria Gorvett observes that “The City of London may be an urban jungle, but it's hardly an idyllic environment for a tree.”  And yet some survive, and the London Plane Tree even flourishes.

In the  17th Century, as global trade took off between Western countries and their colonies, explorers and merchants included millions of tiny guests among the crates of spices, silks, stolen artefacts and tea  – seeds. Somehow two plants from continents thousands of miles apart – an American sycamore and an Oriental plane – met and reproduced.  One possibility is that they coexisted on the grounds of the Oxford Botanical Garden; another  is that they hooked up in Spain.  Either way, the result was a large, strikingly beautiful specimen called the London Plane tree with a fast growth rate and an unusually robust constitution, able to survive in one of the harshest environments on Earth –  our cities.

In the nineteenth century, these  trees were used to develop the leafy boulevards  of London and Paris, and later Sydney and New York; despite the harsh living conditions of the Industrial Revolution they survived, in part because of some quirky features that helped them adjust to city life, not least the ability to discard the outer layers of their smog-coated trunks to reveal a fresh patchwork of green and white bark beneath. This is not unlike a feral hive that absconds from its tree cavity very three years, allowing wax moths to destroy the old comb in preparation for a new swarm to move in the following spring. 

But the London Plane is not as dominant as it once was – or quite as robust. When trees are stressed by their local environment, such as warming cities, localized droughts, compacted soil that is the equivalent of junk food,  paved streets that limit water retention, air pollution,  being confined to a concrete street box, or human abuse such as hammering in nails to hold notices and signs, they become susceptible to a range of diseases and fungal infections. 

Just because old trees have made it this far, there's no guarantee they'll survive another century,  hence the current emphasis on finding and developing a new generation of  city trees. If urban planners get it right, over the next few decades cities across the globe may soon break away from the monoculture aesthetic  represented by the London Plane tree and pioneer something more diverse and robust.  One of the leading contenders is the gingko, an ancient tree that existed alongside the dinosaurs.

The parallels with honey bees are intriguing.  Polluted environments, limited resources, increasing stress, new diseases and pathogens,  increased mortality rates, the need for biodiversity, the search for better and more robust bees, and even, like the ginkgo, a return to origins and practices that existed eons before we, humans, came on the scene. 

But what strikes me most of all is the expectation that the honey bees and the trees adapt to our cities, rather than other other way round.  Granted there are some developments in urban planning that are nature friendly, such as better use of precipitation, preventing storm water run off, and increased use of green spaces, just as there are beekeepers who are trying to be bee, rather than beekeeper, centric. But behind it all is the expectation that somehow nature must adapt to us, despite the declining environment that this attitude has created.   It feels like an archetypal case of blaming the victim : the perpetrators expect the victims, in this case honey bees and urban trees, to change their behaviors to accommodate us. 

 

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27.11 | 11:01

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