Land Degradation: Extent-Impact-Process

Land degradation leads to a significant reduction of the productive capacity of land. Human activities contributing to land degradation include unsuitable agricultural land use, poor soil and water management practices, deforestation, removal of natural vegetation, frequent use of heavy machinery, overgrazing, improper crop rotation and poor irrigation practices. Natural disasters including droughts, floods and landslides, also contribute.

Land degradation, defined as “a reduction in the capability of the land to support a particular use” ,is considered to be one of the major problems facing the world. Land degradation is defined as the long-term loss of ecosystem function and productivity caused by disturbances from which the land cannot recover unaided. Land degradation occurs slowly and cumulatively and has long lasting impacts on rural people who become increasingly vulnerable.

It has been estimated that 23 per cent of all usable land (excluding mountains and deserts) has been affected by degradation to a degree sufficient to reduce its productivity. Soil erosion is a major factor in land degradation and has severe effects on soil functions such as the soil’s ability to act as a buffer and filter for pollutants, its role in the hydro-logical and nitrogen cycle, and its ability to provide habitat and support biodiversity. About 2000 million ha of soil, equivalent to 15 per cent of the earth’s land area, has been degraded through human activities. The main types of soil degradation in decreasing order of impact are water erosion, wind erosion, chemical degradation and physical degradation.

Approaches to soil conservation have been greatly modified since the 1970s. Earlier it used to be concentrated on mechanical protection, such as bunds and terraces, largely to control surface run-off. This has been supplemented by a new approach which calls for greater attention to biological methods of conservation, and the integration of water conservation with soil protection, through improved management of soil plant-water relationships, including reduced disturbance by till age. Within the international agricultural research system, the Consultative Group on International Agricultural Research, there is now a commitment to natural resource management, and explicit recognition of degraded land and desertification as environmental problems.

Despite these developments there is no clear indication that the rate of land degradation has decreased. As yet, there are no continuously monitored indicators of soil condition that would permit quantitatively based assessments of changes over time, comparable to the monitoring of deforestation.

Land degradation has multiple and complex impacts on the global environment affecting a wide range of ecosystem functions and services. These impacts can directly impact the land in a specific location and its productivity, or indirect impact on broader resources and the environmental baseline. Such impacts have consequences for global development including food security, human health, water availability and our ability to adapt to climate change.

Different processes of land degradation also confound the available statistics on soil and/or land degradation. Principal processes of land degradation include erosion by water and wind, chemical degradation including acidification ,salinization, leaching etc. and physical degradation which includes crusting, compaction, hard setting etc. Some lands or landscape units are affected by more than one process among the above mentioned.