Urban ecology part three: Air pollution and the urban heat island effect


Urban ecology part three: Air pollution and the urban heat island effect

Resident writer Nike is back with part three of her ‘urban ecology’ series. If you need to catch up, you can read parts one and two here!

We’ve made it halfway through this five-part series into the magnificence of urban ecology. So far, we’ve talked about how humans became disconnected from nature and how it has the power to heal. Now, it’s time to talk about how greenery can revolutionise our cities and lives for the better.

The air we breathe

It’s no secret that urban life presents us with challenges for our health and lifestyles. Those in Manchester might have noticed the clean air advertisements popping up across the city. This is because Manchester is third on the list of 30 UK towns and cities that exceed the World Health Organisation’s recommended air pollution limit of 10 micrograms per cubic metre.

It’s no secret that air pollution from industrial processes and, more commonly, vehicles in the city can have significant and devastating health impacts. And, these problems affect poorer communities the most. Studies show that people in areas where poverty is the highest are more likely to live near busy main roads, send their children to school in polluted areas, and struggle to get a higher quality of health care that more affluent communities access.

The health problems that ensue include decreased lung function, asthma, bronchitis, emphysema, shortened life span, accelerated ageing of the lungs, and cancer, and these diseases put a significant strain on the NHS.

The trees we plant

It’s simple but effective. Trees are efficient in the removal of air pollutants in uptake through the leaves or the plant surface. One study showed that the reduction of particulate matter near each tree was between 7 and 24%.

The study also suggests that with proper design and location of tree planting, their canopies can protect city residents from air pollution by blocking the airflow which carries particulate matter. You could build barriers of trees between roads and residential areas for example. The rain then washes the collected pollutants away so they don’t return to the air. This spectacular process requires no fossil fuels, just nature, and more trees will help reduce atmospheric CO2 levels.

The urban heat island

Many cities, especially megacities like New York and London, come with their own climate. The unique arrays of skyscrapers and land doused in concrete changes how the wind flows. It insulates the city, and absorbs more heat, creating the urban heat island effect. The cities are much warmer than the rural areas surrounding them.

Hot weather might not initially seem like a problem; we could all use a little more sun in the UK. But warm water from the city that flows into local streams can stress native species used to cooler environments. And, as temperatures increase because of global warming, problems like heat stroke, which hits vulnerable populations like children and older adults, will become more common.

The cool breeze in the trees

Planting trees and other vegetation has cooling effects in our cities for two reasons. They shelter impervious surfaces like concrete from the sun, preventing excess heat storage which later radiates into the air. They also transpire water as they grow, so energy from the sun goes towards turning this water into vapour instead of heating the city. Essentially, trees are super sweaty.

Tree shade reduces the surface temperature by 11 to 25°C and also helps cool the surrounding air. This is noticeable in our everyday lives. Sitting next to a tree on a hot day is always cooler than sitting on the concrete next to a building for this reason.

What does it cost?

It’s clear that introducing more trees into our cities can be hugely beneficial in the fight against air pollution and the urban heat island effect. Strategically planting trees, building parks, and maintaining vegetation comes with costs, however, doing so provides the equivalent of at least £133 million of benefits each year in London alone.

This is just the positive effects it can have on humans. The impact of introducing more greenery to our cities can also be a saving grace for many native and endangered animal species, but we’ll talk more about that next time.

To keep up to date with the Urban Ecology series, follow the Coster Content blog. This is where we share our passions, writing tips, and all the things you need to know to improve your content. If you’d like a more personal introduction to how sharing original and engaging content can boost sales in your business, give Coster Content a call on 0161 413 8418.

Alia Coster