Revision: Environmental Management Science SSLC (English Medium) Class 10 Tamil Nadu Board of Secondary Education

Deforestation is the conversion of forested areas into non-forested areas for agricultural, industrial, urban or other human uses.

The loss of soil or disturbance of the soil structure is called soil erosion.

Water is obtained naturally from ice sheets, ice caps, glaciers, icebergs, ponds, lakes, rivers, streams, and underground is called freshwater.

The collection of rainwater for direct use or for recharging the groundwater level for indirect use is called water harvesting.

Irreparable computers and other electronic goods are known as electronic wastes (e-wastes).

1. Afforestation and Reforestation
   Large-scale afforestation programmes are promoted to increase forest cover, while reforestation helps restore forests that were destroyed earlier, either naturally or through human efforts.
2. Social Forestry
   Started in 1976, social forestry encourages plantation on community and public lands to supply firewood, fodder and small timber, reducing pressure on natural forests and involving local people.
3. Agroforestry
   Agroforestry integrates agriculture, forestry and animal husbandry on the same land to increase productivity, conserve the environment and meet demands for fuel, fodder and timber.
4. Urban Forestry
   Urban forestry focuses on planting trees in towns and cities for aesthetic value, pollution control and improvement of urban environment.
5. Forest Policies and Legislation
   The National Forest Policy (1988) and the Forest (Conservation) Act, 1980 aim to protect forests, prevent diversion of forest land, promote sustainable use and encourage people’s participation in forest conservation.

• Soil erosion is the removal of the top fertile layer of soil by water, wind, and human activities.
• Soil erosion by water includes sheet erosion, rill erosion, gully erosion, leaching, sea erosion, and stream-bank erosion.
• Wind erosion occurs in dry and semi-arid regions where loose soil is carried away by strong winds, reducing soil fertility.
• Human activities such as deforestation, overgrazing, improper farming, and shifting cultivation greatly increase soil erosion.
• Soil erosion reduces agricultural productivity, leads to land degradation, and creates a cycle of poverty.

• Soil conservation means protecting soil from erosion and maintaining its fertility.
• Soil erosion causes loss of fertile topsoil, leading to reduced agricultural productivity.
• Soil conservation helps maintain soil moisture and raise the groundwater level.
• It prevents silting of rivers, floods, droughts, and landslides, especially in hilly areas.
• Soil conservation is essential because soil forms very slowly but can be destroyed quickly, and it supports plants, animals, and human life.

1. Working Principle: Hydroelectric power plants use the potential energy of water stored in a reservoir, which converts into kinetic energy as water flows down.
2. Turbine and Generator: The flowing water (kinetic energy) drives a water turbine, which in turn rotates a generator to produce electrical energy.
3. Energy Conversion:
   Potential energy of water → Kinetic energy of flowing water → Kinetic energy in turbine → Electrical energy
4. No Fuel Pollution: Since no fuel is burned in hydroelectric plants, there is no air pollution from combustion.
5. Advantages & Concerns: Hydroelectric power gives uninterrupted generation if water is available, but reservoir storage may submerge land and affect living things in the river ecosystem.