Depletion of forest trees on a large scale is referred to as deforestation and is the main cause of extinction of species from tropical areas. Deforestation has led to increase in human and livestock population which puts a stress on the limited to resources available in the environment.

Ozone in the stratosphere is considered good ozone as it helps in limiting the entry of UV-rays to Earth surface and protecting us from skin-burn and skin cancer due to over-exposure.

Ozone found in the troposphere is considered as bad ozone cause this ozone increases the smog formation and density hampering vision. Also, ozone if inhaled leads to breathing and other respiratory problems.

Natural aging and nutrient enrichment of a water body is termed as eutrophication. Due to the human activities of adding sewage and industrial waste, water bodies like lake have been heavily eutrophised. Contaminants like nitrates and phosphates overstimulate algal growth as a consequence deplete the oxygen level in water body. Also, other pollutants poison the population of aquatic life leading to their death and increasing the rate of decomposition by bacteria which further depletes the oxygen level. As a result, the aquatic life in water body chokes to death.

The greenhouse effect is a natural phenomenon keeping the atmosphere warm enough for life to occur on the planet and sustain. This is due to absorption of part of the heat energy, while the remainder escapes into space. Water vapor, carbon dioxide, methane and nitrous oxide are part of the greenhouse gases in the atmosphere.