Ozone is a colourless gas that acts as a screen for ultraviolet radiation. It is continuously formed at the higher levels of the atmosphere due to the action of UV rays on molecular oxygen. The high energy UV radiations break down O₂ molecules into nascent oxygen.

Then, this free oxygen atom combines with an oxygen molecule to form ozone.

In recent years, the amount of ozone in the atmosphere is getting depleted.
This ozone depletion causes a greater amount of ultra violet radiation to enter earth’s atmosphere. This has an indirect effect on the ecosystem.(Ecosystem includes both the biological community and the non-living components of an area). It results in the death of many phytoplanktons, thereby affecting the process of photosynthesis. Plants utilise atmospheric CO₂ to make their food. In the absence of plants, the levels of CO₂ in the atmosphere will increase, which would in turn lead to an increase in global warming.
The depletion in the ozone layer also increases the frequency of infectious diseases as it suppresses the immune systems of both human beings and animals. The frequency of skin cancer also increases in human beings because of the direct exposure to ultraviolet radiations.