Land degradation

Serious land degradation in Nauru after the depletion of the phosphate cover through mining

Land degradation is a process in which the value of the biophysical environment is affected by one or more combination of human-induced processes acting upon the land.^[1] It is viewed as any change or disturbance to the land perceived to be deleterious or undesirable.^[2] Natural hazards are excluded as a cause, however human activities can indirectly affect phenomena such as floods and bushfires.

It is estimated that up to 40% of the world's agricultural land is seriously degraded.^[3]

Causes

Overgrazing by livestock can lead to land degradation

Land degradation is a global problem, largely related to agricultural use. The major causes include:

• Land clearance, such as clearcutting and deforestation
• Agricultural depletion of soil nutrients through poor farming practices
• Livestock including overgrazing
• Inappropriate Irrigation^[4] and overdrafting
• Urban sprawl and commercial development
• Land pollution including industrial waste
• Vehicle off-roading
• Quarrying of stone, sand, ore and minerals

Effects

Soil erosion in a wheat field near Pullman, USA.

The main outcome of land degradation is a substantial reduction in the productivity of the land.^[5] The major stresses on vulnerable land include:

• Accelerated soil erosion by wind and water
• Soil acidification and the formation of acid sulfate soil resulting in barren soil
• Soil alkalinisation owing to irrigation with water containing sodium bicarbonate leading to poor soil structure and reduced crop yields
• Soil salination in irrigated land requiring soil salinity control to reclaim the land ^[6]
• Soil waterlogging in irrigated land which calls for some form of subsurface land drainage to remediate the negative effects ^[6]
• Destruction of soil structure including loss of organic matter

Overcutting of vegetation occurs when people cut forests, woodlands and shrublands—to obtain timber, fuelwood and other products—at a pace exceeding the rate of natural regrowth. This is frequent in semi-arid environments, where fuelwood shortages are often severe.

Overgrazing is the grazing of natural pastures at stocking intensities above the livestock carrying capacity; the resulting decrease in the vegetation cover is a leading cause of wind and water erosion. It is a significant factor in Afghanistan.

Agricultural activities that can cause land degradation include shifting cultivation without adequate fallow periods, absence of soil conservation measures, fertilizer use, and a host of possible problems arising from faulty planning or management of irrigation. They are a major factor in Sri Lanka and the dominant one in Bangladesh.

The role of population factors in land degradation processes obviously occurs in the context of the underlying causes. In the region, in fact, it is indeed one of the two along with land shortage, and land shortage itself ultimately is a consequence of continued population growth in the face of the finiteness of land resources. In the context of land shortage the growing population pressure, during 1980-1990, has led to decreases in the already small areas of agricultural land per person in six out of eight countries (14% for India and 22% for Pakistan).

Population pressure also operates through other mechanisms. Improper agricultural practices, for instance, occur only under constraints such as the saturation of good lands under population pressure which leads settlers to cultivate too shallow or too steep soils, plough fallow land before it has recovered its fertility, or attempt to obtain multiple crops by irrigating unsuitable soils.

Severe land degradation affects a significant portion of the Earth's arable lands, decreasing the wealth and economic development of nations. As the land resource base becomes less productive, food security is compromised and competition for dwindling resources increases, the seeds of famine and potential conflict are sewn.

Climate change

Significant land degradation from seawater inundation, particularly in river deltas and on low-lying islands, is a potential hazard that was identified in a 2007 IPCC report.^{[citation needed]} As a result of sea-level rise from climate change, salinity levels can reach levels where agriculture becomes impossible in very low lying areas.

See also

	Earth sciences portal
	Environment portal

Land improvement Land reclamation Sustainable agriculture Environmental impact of irrigation

Desertification Soil#Degradation Soil degradation

References

1. ^ Conacher, Arthur; Conacher, Jeanette (1995). Rural Land Degradation in Australia. South Melbourne, Victoria: Oxford University Press Australia. p. 2. ISBN 0195534360. 
2. ^ Johnson, D.L., S.H. Ambrose, T.J. Bassett, M.L. Bowen, D.E. Crummey, J.S. Isaacson, D.N. Johnson, P. Lamb, M. Saul, and A.E. Winter-Nelson. 1997. Meanings of environmental terms. Journal of Environmental Quality 26: 581-589.
3. ^ Ian Sample (2007-08-31). "Global food crisis looms as climate change and population growth strip fertile land". The Guardian. http://www.guardian.co.uk/environment/2007/aug/31/climatechange.food. Retrieved 2008-07-23. 
4. ^ ILRI (1989), Effectiveness and Social/Environmental Impacts of Irrigation Projects: a Review, In: Annual Report 1988 of the International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands, pp. 18–34, http://www.waterlog.info/pdf/irreff.pdf 
5. ^ "Land: Programmes and Activities". United Nations Environment Programme. http://www.unep.org/themes/land/index.asp?page=programmes. Retrieved 2008-07-19. 
6. ^ ^{a b} "Free articles and software on drainage of waterlogged land and soil salinity control". http://www.waterlog.info. Retrieved 2010-07-28. 

Further reading

• "Human Induced Land Degradation is Preventable". United States Department of Agriculture - Natural Resources Conservation Service. http://soils.usda.gov/use/worldsoils/landdeg/degradation.html. Retrieved 2006-06-20.  This article incorporates text in the public domain produced by the USDA Natural Resources Conservation Service
• Eswaran, H.; R. Lal and P.F. Reich. (2001). "Land degradation: an overview". Responses to Land Degradation. Proc. 2nd. International Conference on Land Degradation and Desertification. New Delhi, India: Oxford Press. http://soils.usda.gov/use/worldsoils/papers/land-degradation-overview.html. Retrieved 2006-06-20. 
• D.L. Johnson and L.A. Lewis Land Degradation:Creation and Destruction, 2nd edition, Rowman and Littlefield, Lanham, Boulder, New York, Toronto, Oxford, 2007.''Italic text