What would swapping 10,000 parking spaces for 10,000 trees do for Birmingham? 

This post is by Sophie O’Connell, policy assistant and Zoe Avison, policy analyst at Green Alliance.

In 2019, cars drove 3.44 billion miles across Birmingham, so it’s no surprise that the city’s particulate matter (PM2.5) levels are double that stipulated as safe in the WHO’s air quality guidelines.   

The University of Birmingham’s West Midlands Air Quality Improvement Programme has identified that air pollution in the West Midlands affects 2.8 million people and costs £860 million annually. Approximately 900 premature deaths in the city are attributed to air pollution every year and it is a real concern for residents. This is illustrated in recent polling we conducted which shows that a fifth of Birmingham residents say air quality is one of the worst things about living in the city. Almost three quarters blamed the excessive number of cars on the road and 41 per cent would like more trees to improve air quality.  

Trees are a particularly effective filter against PM2.5 and at absorbing carbon dioxide, and they can be used as physical barriers between polluting roads and pedestrians. Planting 10,000 additional trees in Birmingham could save nearly £9 million in pollution and health costs between now and 2050.   

Too much urban space is taken up by cars
In Birmingham, over five per cent of the city centre is devoted to parked cars. Using just a fraction of this space to plant these new urban trees would help Birmingham become a cleaner, greener and more resilient city. 

Reducing car use would be a powerful way to tackle this problem as well as helping the city to play its part in meeting national carbon targets. Switching to electric vehicles is a flagship UK climate policy but our recent study shows we can’t only rely on them to achieve a greener transport system, cutting the volume of traffic will also be essential. One proven way of encouraging people out of their cars is to manage the amount of parking available.  

For Birmingham, this is a real prospect. Recently, it announced a transport plan which sets an ambition to transform the city centre, reducing transport emissions by managing parking demand and reallocating road space. A study for Birmingham City Council in 2016 identified an oversupply of 10,000 parking bays and recommended removing them.  

We decided to see what the potential financial benefits might be to the city of converting these parking spaces into green spaces and found the services 10,000 trees could provide in removing traffic pollutants, absorbing excess stormwater runoff, as well as raising street amenity value, added up to £287 million between now and 2050.  

These spaces could be taken from free street parking and private non-residential parking, so would leave the council’s revenue from controlled parking in place. Implementing a workplace parking levy on the city could support the reduction of private non-residential parking while generating revenue for public transport, as has been successfully demonstrated in Nottingham. 

Why we need to plant more city trees
There are so many advantages to increasing urban trees. They can protect against the effects of climate change we are now seeing much more frequently across the UK especially through more heavy downpours, wetter winters and flooding. Cities are particularly vulnerable to flash flooding as paved surfaces leave little room for the ground to absorb water, leading it to drains to take the excess which can be overwhelmed by large sudden volumes. Trees alleviate this surface flooding through the soil around them, creating infiltration space for water to enter the ground, and the tree itself acts like an effective water pump, absorbing water through its roots. This prevents excess surface water from entering the sewerage system. Our analysis found the additional 10,000 trees across Birmingham could save £100,450 in sewerage costs while lessening the costs and inconvenience associate with flood damage, supporting the city’s resilience to the effects of climate change.  

Despite the furore around Sheffield’s trees in recent years, trees are generally valued as capital assets by local authorities. They provide shade through the summer months, counteracting the urban heat island effect by cooling areas and supporting adaptation to climate change. They increase the amenity value of an area by improving aesthetics and supporting local wildlife and biodiversity. The presence of street trees has been linked to lower crime rates and safer driving environments. Trees also have a positive effect on the local housing market.  

Trees instead of car parking spaces is a simple solution to make cities better places to live. It’s time to rethink, as Birmingham is starting to do, how we design our cities and allocate space to meet the health, climate and economic challenges of the future. 

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