A guest post by Rob MacKenzie, Professor of Atmospheric science, School of Geography, Earth & Environmental Science. This article was first published in the University of Birmingham’s Original magazine, June 2013.
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“The city” defines an increasingly large part of the 21st-century human condition. We are living through “the human epoch”: the Anthropocene. So far as we can tell, over half of the human population already resides in cities — striving, producing, and innovating. The creation unlocked by urban living is dazzling. Imagine how much you could make in a single day of self-sufficiency. Multiply that by every working day in a life. Now look around you. What fraction of what you can see could any one person make in a lifetime?
Our time is the Anthropocene and, more and more, our place is the Astysphere – the urban space, possibly most easily visualised from space at night. It is like having tens of thousands of glittering Hollywood A-listers astride the planet, tens of thousands of Clark Gables, say. According to many of his co-stars, and to his legions of fans, Clark Gable was the most attractive man who ever lived. But by some — doubtless apocryphal — accounts, Gable had very bad breath, which dulls some of the glamour of the famous Rhett-Scarlett kiss from Gone With The Wind.
Something of this sensory dissonance is true of our modern cities. Glamorous as they are, the breath of contemporary cities stinks. The government’s Committee on the Medical Effects of Air Pollution estimated in 2010 that the burden of microscopic air particles measured in 2010 would affect UK mortality equivalent to a loss of life expectancy from birth of approximately six months. The same study calculated that reducing the annual average UK concentration of these microscopic particles by 1 unit (out of an atmospheric load of roughly 20 units) would save approximately 4 million life-years for those born in 2008. Of the many air pollution thresholds, set by the UK government, that for the annual average of a gas called nitrogen dioxide is most often exceeded. The Department for Environment, Food, and Rural Affairs lists 712 ‘air quality management areas‘—where specific problems with air pollution have been identified—across the UK, including all of the West Midlands except Solihull. Who would kiss Marylebone Rd in London, or Broad St, Birmingham, and taste the nitrogen dioxide and microscopic particle concentrations so high they contribute more to mortality in the UK today than environmental tobacco smoke or road traffic accidents?
The simplest and most effective way to improve the situation with urban air quality is to reduce emissions from fossil fuel burning. Emission controls have been very effectively implemented for large industrial complexes in the global north but there is still much to do elsewhere in the world, particularly in those places with economies reliant on power from coal. In the UK, the most problematic pollution is that from traffic, especially traffic congestion in narrow streets. Improvements to engine design have led to fewer emissions per vehicle, but improvements in air pollution have stalled for almost a decade. Apparently as a society we have managed to undo the good work of the automotive engineers by driving bigger cars and driving our cars more and more. It is hard to think of a more obvious example of how dynamically complex and difficult to predict is the Astysphere.
One way to intervene in the complicated social-economic-ecological system that is the Astysphere is to use vegetation as “green infrastructure”, analogously to the water, energy and information infrastructures that permeate our cities. Vegetation in cities can provide many and varied benefits: decreased urban heat island effects, improved air quality, increased biodiversity, improved water quality, resilience to flooding, and greater feelings of wellbeing. Realising these benefits requires careful planning and proactive engineering: “the right tree in the right place”. Get it wrong and trees — street trees in particular — can even make things worse, by preventing air pollution from mixing away from the roadside, for instance. Get it right, mind you, and cities could have better air quality and more biodiversity than the agricultural prairies surrounding them, leading to increased wellbeing, happiness and productivity.
In all likelihood this planet will have to carry 8-10 billion people sometime in this century. Cities are our best hope for accommodating so many people, but cities will fail ultimately if we don’t investigate the processes underlying the functioning of these super-systems, if we don’t diagnose and value the services provided to us by the non-human urban system, and if we don’t recognise the vulnerability of all human and non-human complex systems. That’s a lot of detailed and complicated work to undertake, but perhaps the most important work simply is to change our mind-set and realise finally that, for our own good, cities should not just exploit the potentials that people and finite natural resources offer, but should enhance the lived experience of all those who live, and will live, in them. Cities are for life, not just for people.