We already know that trees provide clean oxygen and remove pollutants such as sulphur dioxide, nitrogen dioxide and, of course, carbon dioxide – chemicals which can have a harmful effect on the health of the environment, animals, and humans.
What may be less clear is which tree species are best for improving air quality but research from the University of Sussex indicates that evergreens with smaller leaves are most effective when it comes to removing pollutants and cleaning up the air.
The study monitored 10 trees of different species alongside an urban road and noted which of them captured the most pollution particles.
Out of these 10 species, the yew tree was the most effective at removing urban air pollution. This is because its broader needles have a rougher surface which capture the pollutant particles and keep hold of them better during rainfall.
Leaf pores, or stomata, enable a tree’s gas exchange of pollutants in and oxygen out and the slightly rougher yew leaves help pollution particles to collect on the lower surface of the leaf where they are absorbed.
Japanese cedar and Lawson’s cypress were also effective at removing chemical pollutants from the air.
If trees are strategically grown in the right places, they should be able to help the quality of urban air directly by forming a physical barrier between pollutants and passersby, and by catching the polluting particles on their leaves.
Indirectly, they can help by reducing temperatures which lowers the risk of other harmful pollutant emissions which may spike on hot days, and by keeping shaded buildings cooler which in turn may reduce the need for emission-producing air conditioning.
Similarly, strategically placed forestry and woodland that is appropriately managed can help protect ancient woodlands and their ecosystems from damaging air pollution.
