Last night I had a dream about a huge tree being felled in a storm. It was the last big tree in the area and its roots had been weakened by the surrounding concrete. I started coughing a deep rasping cough and couldn’t breathe and then I woke up with the words ‘air quality’.
According to the World Health Organization, nine out of ten people breathe polluted air. Approximately seven million deaths every year are attributed to bad air quality, which increases the risk of strokes, lung cancer and heart disease. Breathing dirty air has also been linked to immune system damage, as the body becomes inflamed to try and fight off the particles it is being exposed to. 
The world’s forests absorb a third of global emissions every year. Particles, odors and pollutant gases such as nitrogen oxides, ammonia and sulfur dioxide settle on the leaves of a tree. Trees absorb these toxic chemicals through their stomata, or ‘pores’, effectively filtering these chemicals from the air. Trees also mitigate the greenhouse gas effect by trapping heat, reduce ground-level ozone levels and release life-giving oxygen. If we continue with our current rate of deforestation, it will have severe consequences on the quality of our air. 
We need green spaces in cities and we need forests. Trees act as the earth’s purification system by absorbing airborne chemicals and releasing oxygen. To tackle global air pollution, we need to halt deforestation and plant billions of trees.
Many studies are being conducted globally to research which tree species are best planted in cities to combat air pollution that originates from our roads, which is a major source of poor air quality. But we need to remember that trees are also effected by pollution. According to an article by G.M. Moore of the University of Melbourne;
While pollution damage to trees in Australian cities is not common, pollutants can cause significant injury to street trees. Often the damage is subtle or chronic and so may not become evident for many years by which time the damage has been done (Moore 1983). The damage done to street trees by particulate matter, petroleum product spills, accidental spraying with pesticides and natural gas leaks should not be under- estimated and the possibility of pollution damage should not be discounted when street trees perform badly without other apparent causes such as poor soils or insect or fungal attack.
As is often the case with plant responses to stress, the alleviation of other environmental stresses may reduce the effects of pollution damage (Harris 1983). Trees that are otherwise healthy and that are growing in good environments often show higher tolerance of pollutants – prevention is always better than cure. Knowledge of pollutants and their symptoms when affecting trees is important to those managing street trees. Pollution can reduce the amenity value and life spans of street trees, and the competent urban forest manager needs to be aware of pollution as a real and potential risk. 
We need trees and trees also need us to assist in managing air control. One of the biggest polluters in Cities is traffic and according to Robyn Schofield, a Senior Lecturer for Climate Systems Science at the University of Melbourne and Mark Stevenson, a Professor of Urban Transport and Public Health at the University of Melbourne the way we travel can greatly assist air quality.
In the short term, we can all try to use cars less often and not idle our cars when in use. Raising awareness helps; a recent study showed millions of dollars could be saved in fuel costs by exposing drivers of fleets to anti-idling initiatives.
Purchasing a vehicle with automatic idle-stop technology will help cut vehicle emissions. This technology, popular in high-end European car models, automatically switches off the vehicle when it is still and allows the driver to restart the car when their foot presses the accelerator.
To achieve a population-level benefit from such technology, however, would require policymakers to include it in the Australian Design Rules, the national standards for vehicle safety, anti-theft measures and emissions. That process can take many years.
A more sustainable approach to air pollution would be to upgrade Australian refineries to supply low-sulfur fuel. Although costly, the alternative – the escalating health burden associated with vehicle emissions – is a cost too high for society to pay.
We cannot afford to continually invest in a transport system operated solely on fossil fuels. Supporting public transport that operates with “clean” fuels (such as our trams and trains, which run on electricity) will go some way to reducing air pollution in our cities. It is worth noting, though, that while our electricity is mostly fossil-fuelled, this only shifts the air pollution to someone else’s backyard.
Importantly, we need to raise public awareness of the quality of our air and ensure the government considers the long-term ramifications of short-sighted policies.
We must all do our part to improve air quality in Australia – and that means not idling your car, which is an offence that can attract fines as high as $5,000 and/or jail time in some parts of the world.
We can survive weeks without food, days without water, but only minutes without air. Let’s start treating our air as the valuable commodity it is. 
COVID-19 has given us the rare opportunity to empirically observe the positive effects of changing our behaviours and slowing down industry and transport. It has delivered unusual environmental benefits: cleaner air, lower carbon emissions, a respite for wildlife. Now the big question is; are we will to make the necessary changes to keep it going?