1. explain why soil degradation happens. 2. discuss the environmental and socio-economic impacts of...

1. Explain why soil degradation happens.

2. Discuss the environmental and socio-economic impacts of soil degradation.

3. Discuss how soil degradation can be managed.

https://www.youtube.com/watch?v=oa5Rga1Qwyc

Define soil degradation…

• A global process…

• Involves the physical loss of soil (erosion) along with the reduced quality of topsoil (nutrient decline and contamination).

When land with degraded soil becomes unusable, it is considered to be DESERTIFIED.

Global Assessment of Human-Induced Soil Erosion

Polar Regions Temperate Regions Tropical Regions

Temperate areas – soil degradation as a result of economic activity (attitudes of commercial farming and governments).

Tropical areas – Degradation results form population pressure, land shortage and poor land management. Greater climate extremes and poorer soil structures.

The latter has been a great contributor to development disparity.

The Universal Soil Loss Equation

https://www.youtube.com/watch?v=9Zous6X6svs

A=RKLSCPHow do each of these factors affect the rate of soil erosion on a particular slope?

Explain the causes of soil degradation

Removal of natural vegetation cover

Deforestation

Overgrazing

Poor agricultural Management

Urbanisation

Deforestation

Clearing land for agricultural use, for timber collection, for mining purposes. This tends to happen quickly.Vegetation loss for fuelwood is more gradual.

Rain is no longer intercepted by vegetation, and topsoil is disrupted by rain-splash.

Vulnerability to erosion by overland flow increases.

Overgrazing – grazing of natural pastures at intensities beyond the livestock carry capacity.

Due to population pressure and poor agricultural management.

Livestock eat and trample vegetation.

Leaves die away reducing photosynthesis.

Ground more exposed with fewer leaves to intercept rainfall.

Plant species affected die away. Soil erodes where bare patches appear. Soil compaction occurs, so less water can infiltrate, therefore affecting growth rate of plants.

Agricultural Mismanagement – pursuit of short-term gain over long-term damage.

Shifting cultivation without appropriate fallow length.

Absence of soil conservation.

Use of poor irrigation techniques (excess leads to water table rise, leads to salinisation).

Urbanisation / Industrialisation

Globally only 1%, but more significant on a local scale.

Water and Wind Erosion

• Account for 80% of world’s eroded landscapes.

• Water erosion can carry away topsoil as surface runoff.

• Wind erosion more common in arid / desert regions, but short-term water erosion can be devastating.

Physical Degradation

• Soil compaction and sealing where the soil horizons (layers) are compacted together.• This reduces the soil permeability, decreasing

infiltration and increasing runoff.• Compacted soil particles prohibit plant growth and

prevent seedling emergence.

Chemical Degradation• Includes loss of nutrients, salinization, acidification, soil pollution and

fertility decline.

• Acidification is a change in the chemical components of soil (pH becomes more acid or alkaline). Heavy rainfall can leach out calcium faster than it can be replaced by weathering

• Salinisation is a result of excessive irrigation and subsequent evaporation.

• Soil toxicity increases by the introduction of foreign chemicals (usually agricultural, industrial or municipal waste) eg oil spills, excess fertilizer, pesticides/herbicides, radioactive materials, animal sewage.

• Soil pollution can also occur as a result of covered waste disposal.

The same process can apply to areas that have undergone slash-and-burn practices, toxic waste dumping, covered municipal waste disposal. This is particularly significant in nations where there is less regulation surrounding waste disposal.

Discuss the environmental and socio-economic impacts of soil

degradation.

Desertification

Food Security

Reduction in soil bufferingIncreased mudflows and floods

Loss of biodiversityGroundwater quality

Rural to urban migration

Child malnutrition

Higher food prices

Discuss how soil degradation can be managed.

“Discuss’ = offer a balanced review of different options.

Soil management can be subdivided into 2 strategy types:

MECHANICAL METHODS eg afforestation / reforestation – these are efforts that focus on preventing or slowing movement of water downslope, or reducing the impact of wind on the soil.

CROPPING TECHNIQUES eg no-till farming – these are techniques used in agriculture that reduce soil disturbance and manage soil content more effectively.

Mechanical Methods Cropping Techniques

• Soil conditioners (lime or organic matter)• Converting from arable

to pastoral use• Crop rotation• Encourage biodiversity• Shepherding livestock• Managing salt-affected

areas• No-till farming

• Afforestation• Reforestation• Contour ploughing• Terracing• Shelterbelts• Wind-breaks

SELECT 2 OF EACH

1. What each is / what it means2. Explain how and why it helps soil conservation 3. Strengths and weaknesses 4. An example of where this is used