Soil Depletion

Land degradation is a process in which the value of the biophysical environment is affected by combination of human-induced processes acting upon the land.[1] also environmental degradation is the gradual destruction or reduction of the quality and quantity of human activities animals activities or natural means example water causes soil erosion, wind, etc. 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 bush fires.

This is considered to be an important topic of the 21st century due to the implications land degradation has upon agronomic productivity, the environment, and its effects on food security.[3] It is estimated that up to 40% of the world's agricultural land is seriously degraded.[4]

Measures

Land degradation is a broad term that can be applied differently across a wide range of scenarios. There are four main ways of looking at land degradation and its impact on the environment around it:

  • A temporary or permanent decline in the productive capacity of the land. This can be seen through a loss of biomass, a loss of actual productivity or in potential productivity, or a loss or change in vegetative cover and soil nutrients.
  • Action in the lands capacity to provide resources for human livelihoods. This can be measured from a base line of past land use.
  • Loss of biodiversity: A loss of range of species or ecosystem complexity as a decline in the environmental quality.
  • Shifting ecological risk: increased vulnerability of the environment or people to destruction or crisis. This is measured through a base line in the form of pre-existing risk of crisis or destruction.

A problem with measuring land degradation is that what one group of people call degradation, others might view as a benefit or opportunity. For example, heavy rainfall could make a scientific group be worried about high erosion of the soil while farmers could view it as a good opportunity to plant crops.[5]

Different types 

In addition to the usual types of land degradation that have been known for centuries (water, wind and mechanical erosion, physical, chemical and biological degradation), four other types have emerged in the last 50 years:[6]

  • pollution, often chemical, due to agricultural, industrial, mining or commercial activities;
  • loss of arable land due to urban construction;
  • artificial radioactivity, sometimes accidental;
  • land-use constraints associated with armed conflicts.

Overall, 36 types of land degradation can be assessed. All are induced or aggravated by human activities, e.g. sheet erosion, silting, aridification, salinization, urbanization, etc.

Causes

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

Effects

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. ext 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.

High population density is not always related to land degradation. Rather, it is the practices of the human population that can cause a landscape to become degraded. Populations can be a benefit to the land and make it more productive than it is in its natural state. Land degradation is an important factor of internal displacement in many African and Asian countries[8]

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.

Sensitivity and resilience

Sensitivity and resilience are measures of the vulnerability of a landscape to degradation. These two factors combine to explain the degree of vulnerability.[5] Sensitivity is the degree to which a land system undergoes change due to natural forces, human intervention or a combination of both. Resilience is the ability of a landscape to absorb change, without significantly altering the relationship between the relative importance and numbers of individuals and species that compose the community.[9] It also refers to the ability of the region to return to its original state after being changed in some way. The resilience of a landscape can be increased or decreased through human interaction based upon different methods of land-use management. Land that is degraded becomes less resilient than undegraded land, which can lead to even further degration through shocks to the landscape.

Climate change

Significant land degradation from report.

IPCC
Assessment reports:
First (1990)
1992 sup.
Second (1995)
Third (2001)
Fourth (2007)
Fifth (2014)
UNFCCC | WMO | UNEP

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

References

Further reading

  • This article incorporates text in the public domain produced by the USDA Natural Resources Conservation Service
  • D.L. Johnson and L.A. Lewis Land Degradation:Creation and Destruction, 2nd edition, Rowman and Littlefield, Lanham, Boulder, New York, Toronto, Oxford, 2007.

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