In 2019 National governments and local authorities are increasingly taking measures to improve air quality in towns and cities, with air pollution widely recognised as the most significant environmental risk to human health in the UK, and the fourth biggest threat overall – after cancer, heart disease and obesity.
DEFRA published its ‘Clean Air Strategy’ that laid out a series of goals and actions required to achieve them, including the reduction of toxic pollutants like nitrogen oxides, particulate matter and sulphur dioxide.
It’s very easy to think of air pollution as being purely down to the ever-increasing levels of traffic on our roads, and while there’s no doubt that vehicle emissions are huge contributors, there is a wide range of other sources of air pollutants that have a major impact – for example, burning fossil fuels, intensive agricultural food production, industrial heating and even cleaning with solvents.
There are a number of initiatives already in place to help tackle many of the sources of air pollution – for example, London’s new Ultra Low Emission Zone, which is to be introduced in April this year, and six other UK cities which are set to introduce Clean Air Zones. Similarly, there’s a huge debate around wood-burning stoves and the impact they have on air quality, with many arguing for tighter regulation on their design and use.
But as well as tackling the sources, we can also help improve air quality by taking positive steps to remove the harmful pollutants. By ‘greening’ a city’s buildings, streets and public spaces, it’s possible to not only significantly improve the aesthetic look and appeal of an area, but also to help clean the air we breathe, and moderate the temperature, both of individual buildings and the city in general.
Recognising the benefits that urban greening can deliver, many authorities are actively looking to encourage developers and building owners to include urban greening initiatives in their development plans.
For example, under proposals outlined by the City of London Corporation’s Planning and Transportation Committee, every new development in the city’s square mile would have to include plans for ‘urban greening’. This would include details of how, through greening, the building would contribute to improving biodiversity, rainwater run-off, air and noise pollution and temperature regulation, as well as making the City of London a more desirable place for businesses to locate.
For a long time, green walls were seen simply as an aesthetic enhancement to a building (think ivy-covered vicarage walls), but modern systems now deliver so much more than just good looks, with research proving their worth in delivering both environmental and economic benefits; particularly their ability to help improve local air quality, both by absorbing carbon dioxide and releasing oxygen, and by trapping dust and other harmful pollutants.
Greening on a large scale also contributes greatly to passive building cooling during the warmer periods of the year, with green walls providing natural shading for the surfaces of buildings, so preventing them from overheating. They also help buildings to retain their warmth in the winter, acting as an extra layer of exterior insulation.
In addition to helping with cooling and warming, green walls also have a climate control effect – based on ‘evaporative chilling’. This means that green walls absorb heat, but then release it back into the atmosphere by ‘evapotranspiration’ and natural cooling via ventilation. Consequently, green walls can be used to reduce temperature peaks in densely populated areas, making a positive contribution to urban climates.
Furthermore, green walls can help to address the loss of biodiversity due to the spread of urbanization. With green walls consisting of a range of plants, they can act as a home for pollinators, and invertebrates, as well as a habitat and nesting spot for many species. We can even supply bat boxes and bug hotels when we install our green wall systems. So as well as the positive measures to reduce the level of harmful pollutants that are emitted, we can tackle the problem from both ends – enforcing and encouraging reductions but also improving the environment through positive action, bringing greening back to urban areas.