Discuss the role of aeolian processes in desertification and land degradation.

Answer outline

Introduction

Aeolian processes are the erosion, transport and deposition of sediment by wind; they dominate in arid and semi-arid lands with sparse vegetation and loose, dry soil.

Erosion: loss of soil

• Deflation removes fine silt, clay and organic matter, the most fertile fraction, leaving coarse sand or a gravel lag (desert pavement).
• Deflation hollows (blowouts) lower the land surface; abrasion wears down surfaces by sandblasting.

Transport

• Saltation (grains up to about 2 mm) likely accounts for 50 to 70% of deflation; suspension carries fine dust long distances; creep moves coarse grains.
• Dust storms reduce visibility and affect crops and people far from the source.

Deposition: burial and dune spread

• Migrating dunes, such as barchans that can move up to 30 m a year, bury fields, roads, rail lines and canals.
• Desert pavement left behind by deflation is a sheet of rock fragments from which the fine soil has gone.

Human triggers that intensify wind action

• Overgrazing, removal of shrubs for fuel, ploughing of marginal land and drought expose soil to wind.
• The US Dust Bowl of the 1930s resulted from severe drought combined with human removal of the native cover that held the topsoil.

Control measures

• Shelterbelts, sand dune stabilisation and grass cover; CAZRI, Jodhpur, began in 1952 with dune stabilisation and shelterbelts against wind erosion.
• Restoring degraded land under India's Land Degradation Neutrality commitment.

Conclusion

Wind is the agent but loss of vegetation is the trigger, so controlling desertification means keeping soil covered and managing land use, which India's 2030 restoration target seeks to do.