RADIOACTIVE WASTES
$\displaystyle \small \bullet$ Initially, nuclear energy was hailed as a non-polluting way for generating electricity.
$\displaystyle \small \bullet$ Later on, it was realized that the use of nuclear energy has two very serious inherent problems.
$\displaystyle \small \bullet$ The first is accidental leakage, as occurred in the Three Mile Island and Chernobyl incidents.
$\displaystyle \small \bullet$ The second is safe disposal of radioactive wastes.
$\displaystyle \small \bullet$ Radiation, that is given off by nuclear waste is extremely damaging to organisms, because it causes mutations to occur at a very high rate.
$\displaystyle \small \bullet$ At high doses, nuclear radiation is lethal but at lower doses, it creates various disorders, the most frequent of all being cancer.
$\displaystyle \small \bullet$ Therefore, nuclear waste is an extremely potent pollutant and has to be dealt with utmost caution.
$\displaystyle \small \bullet$ Disposal of nuclear wastes:
$\displaystyle \small \bullet$ Storage of nuclear waste, after sufficient pre-treatment, should be done in suitably shielded containers buried within the rocks, about 500 m deep below the earth’s surface.

GREENHOUSE EFFECT AND GLOBAL WARMING
$\displaystyle \small \bullet$ The term ‘Greenhouse effect’ has been derived from a phenomenon that occurs in a greenhouse.
$\displaystyle \small \bullet$ It looks like a small glass house and is used for growing plants especially during winter.
$\displaystyle \small \bullet$ In a greenhouse the glass panel lets the light in, but does not allow heat to escape. Therefore, the greenhouse warms up.
$\displaystyle \small \bullet$ The greenhouse effect is a naturally occurring phenomenon that is responsible for heating of Earth’s surface and atmosphere.
$\displaystyle \small \bullet$ Without greenhouse effect the average temperature at surface of Earth would have been a chilly –18°C rather than the present average of 15°C.
$\displaystyle \small \bullet$ “The progressive warming of Earth’s surface due to an increase of greenhouse gases is called greenhouse effect”.
$\displaystyle \small \bullet$ Green House Gases: Carbon dioxide ($\displaystyle CO_{2}$), Methane ($\displaystyle CH_{4}$), $\displaystyle N_{2}O$, Chlorofluorocarbon (CFC) and Water Vapor ($\displaystyle H_{2}O$)

Significance of Green House Effect
$\displaystyle \small \bullet$ It is essential to make earth warmer for organisms to live.
$\displaystyle \small \bullet$ The energy of sunlight reaches the outermost atmosphere. Clouds and gases reflect about one-fourth of the incoming solar radiation, and absorb some of it but almost half of incoming solar radiation falls on Earth’s surface heating it, while a small proportion is reflected back.
$\displaystyle \small \bullet$ Earth’s surface re-emits heat in the form of infrared radiation. But a part of it is absorbed by atmospheric gases ($\displaystyle CO_{2}$, $\displaystyle CH_{4}$ etc.) and so cannot escape into space.
$\displaystyle \small \bullet$ These gases (greenhouse gases) radiate heat energy.
$\displaystyle \small \bullet$ Overheating of Earth due to increased level of greenhouse gases is called global warming.
$\displaystyle \small \bullet$ During the past century, the temperature of Earth has increased by 0.6°C, most of it during the last 3 decades.
$\displaystyle \small \bullet$ Contribution of greenhouse gases to total global warming: $\displaystyle CO_{2}$ (60%), $\displaystyle CH_{4}$ (20%), CFCs (14%) & $\displaystyle N_{2}O$ (6%).  

Effect of Global Warming
$\displaystyle \small \bullet$ Deleterious changes in the environment and resulting in odd climatic changes (e.g. El Nino effect).
$\displaystyle \small \bullet$ Increased melting of polar ice caps as well as of other places like the Himalayan snow caps.
$\displaystyle \small \bullet$ Rise in sea level that can submerge many coastal areas.
$\displaystyle \small \bullet$ El-Nino Effect: It is a warm phase and is associated with a band of warm ocean water (that develops in the central and East – central equatorial pacific).
$\displaystyle \small \bullet$ An Abnormal warming of surface of ocean water in the eastern tropical pacific (also called Southern Oscillation of ENSO).

Control of Global Warming
$\displaystyle \small \bullet$ Reduce use of fossil fuel
$\displaystyle \small \bullet$ Improving efficiency of energy usage
$\displaystyle \small \bullet$ Reducing deforestation
$\displaystyle \small \bullet$ Promoting afforestation programme (Planting trees)
$\displaystyle \small \bullet$ Slowing down the growth of human population
$\displaystyle \small \bullet$ International initiatives are also being taken to reduce the emission of greenhouse gases into the atmosphere.

OZONE DEPLETION IN THE STRATOSPHERE
$\displaystyle \small \bullet$ ‘Bad’ ozone, formed in the lower atmosphere (troposphere) that harms plants and animals.
$\displaystyle \small \bullet$ There is ‘good’ ozone also; this ozone is found in the upper part of the atmosphere called the stratosphere, and it acts as a shield absorbing ultraviolet radiation from the sun.
$\displaystyle \small \bullet$ The thickness of the ozone layer is measured in terms of Dobson units (DU).
$\displaystyle \small \bullet$ Ozone ($\displaystyle O_{3}$) gas is continuously formed by the action of UV rays on molecular oxygen, and also degraded into molecular oxygen in the stratosphere.
$\displaystyle \small \bullet$ There should be a balance between production and degradation of ozone in the stratosphere.

Ozone Depletion
$\displaystyle \small \bullet$ The balance  of   ozone   disrupted   due   to   enhancement   of   ozone   degradation   by chlorofluorocarbons (CFCs).
$\displaystyle \small \bullet$ CFCs find wide use as refrigerants.
$\displaystyle \small \bullet$ CFCs discharged in the lower part of atmosphere move upward and reach stratosphere.
$\displaystyle \small \bullet$ In stratosphere, UV rays act on them releasing Cl atoms. Cl degrades ozone releasing molecular oxygen.
$\displaystyle \small \bullet$ Chlorine acts as catalysts and not consumed in the reaction.
$\displaystyle \small \bullet$ Hence, whatever CFCs are added to the stratosphere, they have permanent and continuing effects on Ozone levels.
$\displaystyle \small \bullet$ Ozone depletion is occurring widely in the stratosphere, the depletion is particularly marked over the Antarctic region. This has resulted in formation of a large area of thinned ozone layer, commonly called as the ozone hole.

Effects of UV Rays
$\displaystyle \small \bullet$ UV radiation of wavelengths shorter than UV-B, are almost completely absorbed by Earth’s atmosphere.  
$\displaystyle \small \bullet$ But, UV- B causes DNA mutation.
$\displaystyle \small \bullet$ It causes aging of skin, damage to skin cells and skin cancers.
$\displaystyle \small \bullet$ A high dose of UV-B causes inflammation of cornea (snow-blindness), cataract etc. It permanently damages the cornea.
$\displaystyle \small \bullet$ Prevention:
$\displaystyle \small \bullet$ Montreal Protocol was signed at Montreal (Canada) in 1987 (effective in 1989) to control the emission of ozone depleting substances.
$\displaystyle \small \bullet$ Many more efforts have been made and protocols have laid down definite roadmaps, separately for developed and developing countries, for reducing the emission of CFCs and other ozone depleting chemicals.

DEGRADATION BY IMPROPER RESOURCE UTILIZATION AND MAINTENANCE
$\displaystyle \small \bullet$ The degradation of natural resources can occur, not just by the action of pollutants but also by improper resource utilization practices.
$\displaystyle \small \bullet$ Soil erosion and desertification
$\displaystyle \small \bullet$ “The removal of top fertile soil layer due to natural and human activities”.
$\displaystyle \small \bullet$ Reasons for soil erosion:
$\displaystyle \small \bullet$ Over-cultivation
$\displaystyle \small \bullet$ Unrestricted grazing
$\displaystyle \small \bullet$ Deforestation
$\displaystyle \small \bullet$ Poor and improper irrigation practices
$\displaystyle \small \bullet$ Increased urbanization.

Water-logging and Soil Salinity
$\displaystyle \small \bullet$ Irrigation without proper drainage of water leads to water-logging in the soil.
$\displaystyle \small \bullet$ Water-logging draws salt to the surface of the soil.
$\displaystyle \small \bullet$ The salt is deposited as a thin crust on the land surface
$\displaystyle \small \bullet$ Salt starts collecting at the roots of the plants.
$\displaystyle \small \bullet$ This increased salt content is unfavorable to the growth of crops and is extremely damaging to agriculture.
 
Deforestation
$\displaystyle \small \bullet$ Conversion of forested areas to non-forested land is called deforestation.
Reasons for deforestation:
$\displaystyle \small \bullet$ The conversion of forest to agricultural land so as to feed the growing human population.
$\displaystyle \small \bullet$ Trees are axed for timber, firewood, cattle ranching and for several other purposes.
$\displaystyle \small \bullet$ Slash and burn agriculture commonly called as Jhum cultivation in the north-eastern states of India.
$\displaystyle \small \bullet$ The farmers cut down the trees of the forest and burn the plant remains.
The ash is used as a fertilizer and the land is then used for farming or cattle grazing.
$\displaystyle \small \bullet$ After cultivation, the area is left for several years so as to allow its recovery. The farmers then move on to other areas and repeat this process.
$\displaystyle \small \bullet$ With increasing population and repeated cultivation, this recovery phase is done away with, resulting in deforestation.
Effects of deforestation:
$\displaystyle \small \bullet$ Leads to global warming due to excess carbon dioxide.
$\displaystyle \small \bullet$ Loss of biodiversity due to habitat destruction.
$\displaystyle \small \bullet$ Disturbs hydrologic cycle
$\displaystyle \small \bullet$ Causes soil erosion
$\displaystyle \small \bullet$ leads to desertification in extreme cases.
Reforestation: “The process of restoring a forest that once existed but was removed at some point of time in the past. Reforestation may occur naturally in a deforested area.
Afforestation: Developing a forest in a new area where no such forest existed in that area.

Case Study of People’s Participation in Conservation of Forests
$\displaystyle \small \bullet$ People’s participation has a long history in India. In 1731, the king of Jodhpur in Rajasthan asked one of his ministers to arrange wood for constructing a new palace.
$\displaystyle \small \bullet$ The minister and workers went to a forest near a village, inhabited by Bishnois, to cut down trees.
$\displaystyle \small \bullet$ The Bishnoi community is known for its peaceful co-existence with nature.
$\displaystyle \small \bullet$ The effort to cut down trees by the kings was dissatisfied by the Bishnois.
$\displaystyle \small \bullet$ A Bishnoi woman Amrita Devi showed exemplary courage by hugging a tree and daring king’s men to cut her first before cutting the tree.
$\displaystyle \small \bullet$ The tree mattered much more to her than her own life.
$\displaystyle \small \bullet$ Sadly, the king’s men did not gave attention to her requests and prayers, and cut down the tree along with Amrita Devi. Her three daughters and hundreds of other Bishnois (365 Persons) followed her, and thus lost their lives saving trees.
$\displaystyle \small \bullet$ Nowhere in history do we find a commitment of this magnitude when human beings sacrificed their lives for the cause of the environment.
$\displaystyle \small \bullet$ The Government of India has recently instituted the Amrita Devi Bishnoi Wildlife Protection Award for individuals or communities from rural areas that have shown extraordinary courage and dedication in protecting wildlife.
 
Chipko Movement of Garhwal Himalayas
$\displaystyle \small \bullet$ In 1974, local women showed enormous bravery in protecting trees from the axe of contractors by hugging them.
$\displaystyle \small \bullet$ People all over the world have acclaimed the Chipko movement.

Joint Forest Management (JFM)
$\displaystyle \small \bullet$ Government of India in 1980s introduced the concept of Joint Forest Management (JFM) to work closely with the local communities for protecting and managing forests. In return for their services, the communities get benefit of forest products (fruits, gum, rubber, medicine, etc.).