Page 51 - Soil Degradation, Conservation and Remediation

36 1 Soil Resources and Soil Degradation

2500
1985
2000
Area, million heclare 1500 1094

1000

500 549
239
83
0
Water Erosion Wind Erosion Chemical Physical Total
Degradation Degradation
Soil degradation processes

Fig. 1.8 Land area so far degraded by different processes (Data from Oldeman 1994 )

Soil degradation types and subtypes
Type Subtypes
W: Water erosion Wt: loss topsoil
Wd: terrain deformation/mass movement
Wo: off-site effects
Wo: reservoir sedimentation
Wof: fl ooding
Woc: coral reef and seaweed destruction
E: Wind erosion Et: loss of topsoil
Ed: terrain deformation
Eo: overblowing
C: Chemical deterioration Cn: Loss of nutrients and/or organic matters
Cs: Salination
Ca: Acidifi cation
Cp: Pollution
Ct: Acid sulphate soils
Ce: Eutrifi cation
P: Physical deterioration Pc: compaction, sealing, and crusting
Pw: water logging
Pa: lowering of water table
Ps: subsidence of organic soils
Po: other physical activities such as mining and urbanization
B: Degradation of biological activity

Land area degraded by each type of soil degradation is shown in Fig. 1.8 .