Trees are the source of oxygen, shade and help curb pollution at the same time. For these reasons, trees are often planted in polluted cities and urban areas. Recently, smart trees were planted in Paris to curb pollution and build a healthy environment. But a recent study has suggested that plants can also be the cause of air pollution.
Trees not only help in curbing air pollution but also in controlling soil erosion, evaporation of water and lower the overall temperature of an area.
So, how can they be the cause of air pollution? Have we been reading the benefits of trees all wrong?
A study carried out by Galina Churkina of the Humboldt University, Berlin, indicates that urban vegetation creates as much as 60% ground-level ozone. When the temperature rises, chemical compounds emitted from urban vegetation mixes with air to give birth to ground-level ozone.
Ozone in its pure form can prove to be quite harmful to humans as it can cause breathing difficulties and severely damage lungs in the long run.
The study carried out in 2004 and 2016, when temperatures in Berlin were hovering in the 30-degree Celsius range, shows that plant emissions were clearly high during this period.
The Technical Details
Moving into technicality, on a hot summer day in the Berlin-Brandenburg metropolitan area, urban plants release isoprene which combines with other man-made chemicals like nitrous oxides forming ground-level ozone.
Clearly, this can be seen as domino effect taking place since these chemicals (which mix with the ‘plant emissions’) are man-made.
And it shouldn’t come as a surprise that these chemicals exist abundantly in populated or industrial areas — thanks to ACs, Cars and Industries.
If we talk numbers, on a day with temperatures hovering around 25-degree Celsius, the emissions added to almost 6-20% ozone formation. While a spike in temperature to around 30-degree saw the ozone emission rise up to 60%.
And this number is expected to go up as this study undervalued the actual isoprene concentrations over urban forests and parks by 0.6–1.4 ppb.
However, experts caution that this study shouldn’t see plants or vegetation as the main cause or the reason to stop planting trees in urban areas. Rather the focus should be more on reducing the anthropogenic pollutants like nitrous oxide.
Solution to the Problem?
Since trees alone can not contribute towards healthy and clean air, tree planting campaigns in urban areas can be merged with lowering the fleet of cars in the streets. Another solution is to impose a fine on the older vehicles so that the owners are forced into not using them.
Every year, almost 10,000 people die a premature death at the hands of air pollution alone in London. And if we look at the global count, there are nearly 40,000 early deaths each year due to indoor pollution alone.