Context

The wildfires that scorched much of Australia, burned over 33 million hectares of land, killed or displaced 3 billion animals and became one of the worst natural disasters in the country.

Frequent widespread forest fires in a warming world are the new threats to the ozone layer.

Findings

The 2019-20 Australian wildfires have resulted in spiked temperatures in the lower stratosphere over Australia by 3°C leading to a rise in global temperatures by 0.7°C

Shortly after the fires subsided there was a sharp drop in Nitrogen dioxide levels, which is a precursor to ozone depletion. Researchers revealed that the drop in Nitrogen dioxide has led to a depletion of the column of ozone by 1 percent.

Ozone layer depletion strengthens polar vortex (a pocket of low pressure and cool air over the south pole). The stronger the polar vortex, the greater the depletion.

Forest fires

Forest fire may be defined as an unclosed and freely spreading combustion that consumes the natural fuels (grass, tree, shrubs, leaves) based on environmental conditions (wind, topography).

Fuel, heat and oxygen are three important components for the formation of forest fires. They are commonly referred to as “Fire Triangle”

Causes of Forest fires

According to UN Intergovernmental panel on climate change, rising global temperatures and drier conditions are leading to frequent, massive wildfires around the world.

Natural causes for forest fires include lightning, volcanic explosion, friction of rolling stone, etc. Anthropogenic causes include, shifting cultivation, stubble burning, incineration of waste, for concealing illicit felling, etc.

Ozone Layer

Ozone is a tri atomic molecule of oxygen. It occurs in two layers in the atmosphere. The layer closest to the earth’s surface is called the troposphere and contains bad ozone, an air pollutant which is the major component of urban smog.

Good ozone sits in the stratosphere, located between 10 km and 50 km above the earth’s surface and absorbs harmful ultraviolet radiation from the sun.

Mechanism of Ozone Depletion

UV radiation from the sun breaks down oxygen molecules in the upper levels of the earth’s atmosphere there by releasing free atoms which bond with other oxygen molecules to form ozone. There should be a balance between production and degradation of ozone in the stratosphere.

In recent times, due to increased use of Chlorofluorocarbons (CFCs), there has been an enhancement in Ozone degradation. CFCs discharged in the lower parts of the atmosphere, reach up to the stratosphere, where they are acted upon by UV rays, resulting in the release of Cl (Chloride) atoms. These atoms degrade ozone releasing molecular oxygen. Ozone depletion results in the formation of a large area of thinned ozone layer, referred to as Ozone hole.

Forest fires and ozone depletion

Forest fires producing injected smoke particles have led to an increase in formaldehyde, chlorine nitrate, chlorine monoxide, and hypochlorous acid and decreases in ozone, nitrogen dioxide, and hydrochloric acid. These changes in stratospheric composition can affect ozone chemistry in several ways.

Effects of Ozone Depletion

Ozone layer serves as a shield by protecting the Earth’s surface by absorbing harmful UV-B and UV-C radiation.

1. It can affect human Health resulting in sunburns, premature aging of skin, cataracts, cancer, snow blindness, etc

1. It affects world’s major crop species resulting in reduced photosynthesis and flowering. Agricultural crops like wheat, soyabean, etc are sensitive to UV- B radiation.

International Efforts for protection of Ozone layer

1. Montreal Protocol (1987) – Under this protocol, Countries agreed to face down the production and consumption of ozone depleting substances (ODSs) in a time bound manner. Developing and developed countries have equal but differentiated responsibilities.

1. Kigali amendment (2016) -Under this amendment, Countries committed to cut down production and consumption of HFCs by more than 80% by 2047.