I am looking at a change.org plea asking me to oppose cutting of trees coming in the way of a national highway. As the plea is forwarded by a very erudite professor, I decided to study it, only to discover an interesting misconception that really needs our attention.
This plea and many more similar ones have one central theme. They all presume a link between air quality index (AQI) and trees, so the uncouth me is forced to look at the science behind the hazardous AQI numbers that they are riding for supporting their cause.
AQI is a composite index based on levels of five major air pollutants, i.e. ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. And the bitter truth (for saviours of trees and planet) is that these pollutants and trees have no positive correlation linking them.
In most cases (other than dust storms, volcanic eruptions or forest fires) it is the normal human activities that produce these pollutants, so they are present across the globe wherever dense populations exist. Their presence becomes more pronounced in winter as cold air stagnates close to ground.
While I invite tree-lovers to explain their version of science of how any of the parameters considered for AQI will improve by having trees, I would like to bring to your attention a phenomenon that points exactly in opposite direction, especially in India.
In the air quality index, the number that is really worrisome for us in Ahmedabad or Delhi is of particulate matter (PM), more specifically of PM 2.5 levels, i.e. of particles that are smaller than 2.5 micrometer in size.
These extremely small particles are highly dangerous because they pass through all the natural defences of our respiratory system and cause long term damage to our lungs. The smog that has become symbol of pollution in India is caused by the high PM levels.
World over particulate matter is produced due to industrial activities, partial burning of fuel by vehicle engines and also because of burning of organic material. While we are guilty of having polluting industries and chaotic traffic, there is one uniquely local factor that could be a big source of particulate matter in our cities, and that is trees.
As winter is a season of fall, leaf litter forms a large part of waste material in our cities. As it is simple to burn it, city administration is unable to wean our sanitation workers off it even after working hard at training them. Citizens are also equally guilty of disposing organic waste by burning it.
This problem is compounded in cold weather as those forced to live outdoors are tempting to burn litter and wood for warmth. All this burning produces a massive amount of particulate matter that hangs around in cold air and gives alarming spike to AQI. So, while not contributing much in improving AQI, a city-dwelling tree is possibly a guilty of abetting increase in PM2.5 levels.
The real learning from the story of trees is that understanding is a greatest requirement for love to be meaningful. We need trees, but we also need to understand the comprehensive role they play, or it is entirely possible that having more trees can end up contributing to increasing pollution instead of reducing it.
So, if you are a tree-lover and really want to improve air quality, invest your energy in preventing burning of leaf litter instead of wasting time in raising objections to building of a road that may be smoothening transportation and reducing pollution.
Pollution is a massive crisis that is getting bigger because emotion-driven “lovers” of nature have hijacked our response to it. We need to break free from these obsessions and allow scientific reason to prevail, if we want real solutions.
#AirQualityIndex #AQI #Smog #Pollution #AhmedabadPollution #DelhiPollution #PM2.5 #ParticulateMatter