Reforestation is often dismissed as a realistic way of fighting climate change, the scale of co-ordinated planning and resources required is considered to be much too large and almost impossible to achieve in a realistic time scale. In 2000, a special report on the effects of tree planting found that trees could remove around 1.1–1.6 billion tonnes of CO2 per year from the atmosphere – which would only put a small dent in our yearly emissions. However, whilst planting trees is still an important part of reducing the amount of Co2 in our atmosphere, planting them in cities is one of the most effective ways to combat pollution and the effects of climate change. Since air pollution in London (and other parts of the UK) is an ongoing issue, we decided to take a look at one of the most cost effective ways to fight pollution that the government could implement.

In January of this year, London mayor Sadiq Khan issued the highest air pollution alert in London for the first time, declaring that the “filthy air” had become a “health crisis”, with readings in from the Air Quality Index showing that air quality in London was worse than Beijing at some points of the day. But this is not the first time that the public have been warned of the dangers of air pollution in cities. A 2015 study from King’s College London found that almost 9,500 people die early each year in London because of long-term exposure to air pollution, more than twice as many as previously thought. However, the cause is not Co2, it is a combination of fine particulates called PM2.5s and PM10s, along with nitrogen oxide (NO2). These are created by mostly by diesel cars, lorries, and busses and have been found to affect both lung capacity and growth.

As well as public health concerns there are also significant economic costs to pollution, the Kings Report, compiled by the London government, estimated that,
“economic costs… ranged from £1.4 billion (long-term exposure to PM2.5 and mortality; short-term exposure to PM2.5 and hospital admissions; short-term exposure to NO2 and both deaths brought forward and hospital admissions) to £3.7 billion (replacing short-term exposure to NO2 and deaths brought forward with long-term exposure to NO2 and mortality). Inclusion of other less well established health outcomes would increase the economic costs although this has not been estimated in this report.”

The last Mayoral administration under Boris Johnson spent £1.43m applying a special glue to roads around London that was, in theory, supposed to stick air pollutants to the road. However in 2013, the scheme was deemed to have been an ineffectual waste of money – the author of a Greater London Authority (GLA) report on how London’s illegal air pollution disproportionately affects deprived schools even accused Boris Johnson of burying the negative findings after the Guardian published a leaked version of the report last year.

We cannot claim that the government has ignored the issue since, the Mayor of London has launched a number of schemes to help fight air pollution in London in the coming years. They have introduced a number of measures to fight air pollution in London over the coming years, including:

  • A £10 toxicity charge applied  to older and more polluting vehicles from October 2017 – drivers could pay up to £21.50 at peak congestion
  • The world’s first Ultra Low Emission Zone (ULEZ) is due to start in London in 2019, creating strict emission standards for diesel vehicles at all times in an attempt to reduce emissions by 50 percent in central London.
  • London (and Paris) will both be launching a vehicle scoring system to show potential buyers the emission standards of cars on sale.
  • Audits on primary schools in areas exceeding legal limits of NO2 – £1 billion has been pledged by the major to help local boroughs to implement changes to improve air quality.
  • London taxis licensed after January 1st 2018 will have to be zero-emissions capable – plans for zero emissions ranks and rapid charge points have been laid out
So whilst Sadiq Kahn and his Labour administration are clearly taking some measures to combat air pollution in the capital, we feel that London, and many other cities in the UK, could benefit from the most cost-effective way of fighting air pollution and the effects of climate change; planting trees.
A 2016 global report from the Nature Conservancy explored the ways in which targeted tree planting campaigns within cities could be utilised to reduce temperatures, ease the pressure on storm water systems by absorbing rainwater, and soak up fine particle pollution. Trees take in both heat and sunlight, providing shade during heatwaves and cooling down city temperatures. The report found that well placed trees can reduce temperatures by anywhere from 0.5 degrees Celsius to 2 degrees Celsius during the hottest summer days – something that could become increasingly more significant as global temperatures creep upwards. This also reduces electricity use by between 0.9 and 4.8 percent in some cities as less power is used to keep houses and buildings cool during heatwaves. Trees have also been shown to boost real estate value and even have some mental health benefits – something the government has promised to deal with.

With all these benefits rolled into a cost-effective solution to air pollution we feel that tree planting has been over-looked by many city governments across the UK, and the rest of the world, as an effective way to substantially reduce air pollution. But there are examples of this policy succeeding; in 2016 Rajshahi City, Bangladesh, found that their tree planting campaign resulted in a 67.2 percent decrease in concentration of PM10 particles – serving as a benchmark for other heavily polluted cities to improve air quality. The key trapping to avoid is creating dense canopies over narrow streets, this can actually worsen air pollution as it can trap poor quality air at street level, rather than allowing it to dissipate in the breeze.

London’s trees already provide at least £133 million of benefits every year, so the economic benefits have already been acknowledged. It is clear that planting trees can provide medical, social, and economic benefits to a society, whilst reducing air pollution and fighting the effects of climate change, so perhaps it is time that governments looked at this policy as a serious proposal.

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