Patterns in Environmental Quality and Sustainability

Soil and Change

Soil and Change

• Explain the causes of soil degradation.• Discuss the environmental and

socio-economic consequences of this process, together with management strategies.

Degradation of the soil is caused by natural processes as well as by

human activities

Human Activities

• Deforestation• Farming • Economic activities : Mining• Developmental works : Settlements, Transport

and Communication

DEFORESTATION

• http://www.treehugger.com/natural-sciences/unchopping-a-tree-a-video-that-puts-deforestation-in-perspective.html#0_undefined,0_

Deforestation

• Clearing the Earth's forests on a massive scale, often resulting in damage to the quality of the land

• Deforestation occurs because of the increased demand for food and grazing livestock.

• Another important reason for forest conversion is to meet the fuel wood demand. – The rural population in the tropics depends almost

exclusively on fuel wood as their primary sources of energy.

– It is estimated that the per cent energy requirements met by fuel wood in rural areas is 90% in Kenya, 88% in Zambia, and 95% each in Nepal, Sri Lanka, and Thailand.

Farming

• Agriculture in its multiple dimensions has been a major human intervention to cause soil erosion and loss of bio-diversity.

• It has interfered with the natural means to regenerate land productivity and replenish available moisture storage.

• The worst form of erosion on farm lands is wash-off or sheet erosion.

Sheet Erosion

• erosion that removes surface material more or less evenly from an extensive area as contrasted with erosion along well-defined drainage lines

Economic Activities

• Minerals and metals as well as fossil fuel are other natural resources that the society needs to meet its energy requirement and for other activities

• The extraction of such natural resources demand deforestation and changes in landscape.

Developmental Works

• Human settlements are a major threat to the soil and land, as during the construction in the developmental phase, much accelerated erosion takes place.

• Roads, railways, etc. are required to be aligned, cutting across the natural divides such as ridges, valleys, streams and rivers.

• The construction causes dislocation of earth mass and rock material associated with disruption of natural drainage system, resulting in accumulation of water and cause land slides.

Natural Activities

ErosionSalinity

Erosion

Water erosionWind erosion.

http://videos.howstuffworks.com/discovery/31883-howstuffworks-show-episode-4-power-of-water-erosion-

video.htm

WATER EROSION

1. Sheet erosion where a fairly uniform layer of soil is removed ‑over an entire surface area.

2. Rill erosion this occurs where water runs in very small ‑

channels over the soil surface. Losses consist mainly of surface soil.

3. Gully erosion This occurs when rills flow together to make ‑larger streams. They tend to become deeper with successive flows of water and can become major obstacles to cultivation.

4. Bank erosion this is caused by water cutting into the banks ‑of streams and rivers. It can be very serious at times of large floods and cause major destruction to property.

SALINITY• High salt levels in soils reduce the ability of

plants to grow or even to survive.• This is can be caused by natural processes, but

much occurs as a consequence of human action.• Caused by the discharge of saline groundwater.• The large scale clearing of forests since

European settlement has seen increased 'recharge' of aquifers (where groundwater gathers in the ground)

Wind Erosion• The force of wind becomes strong enough to cause

erosion when it reaches what is known as the 'critical level' and this is the point at which it can impart enough energy to cause soil particles to move.

• Particles first start rolling along the surface.• Once they have rolled a short distance they often

begin to bounce into the air, where wind movement is faster.

*surface creep: where soil particles too large to bounce and are rolled downwind.

European Soil Charter

• Because 30 % of European soil was considered to be moderately or severely damaged they came up with the following:

• Soil is a precious asset• Soil is a limited resource which is easily destroyed• Land has a wide variety of uses and a proper planning

policy is needed by Governments for urban development and civil engineering projects

• Farmers and foresters must preserve the soils quality• Soil must be protected from erosion and pollution

SOLUTIONS1. to prevent erosion of bare soil, it is important to maintain a

vegetation cover, especially in the most vulnerable areas e.g. those with steep slopes, a dry season or periods of very heavy rainfall.

2. Where intensive cultivation takes place, farmers should use a crop rotation in order to prevent the soil becoming exhausted. Careful management of irrigation.

3. livestock grazing rates must be carefully managed to prevent overgrazing.

4. Perhaps we must attempt to restrict highway construction and urbanization to areas of lower agricultural potential. With extractive industries, a pledge must be secured to restore the land to its former condition before planning permission for quarries or mines is granted.

Dust Bowl of the United States

Part I: Summarize the Dust Bowl that hit the Unite States

Part II: Define the following:• Crop rotation• Strip farming• Contour plowing • Terracing• Cover crops• Fallow