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Desertification: causes, occurences
and control stategies
Immanuel Chongboi Haokip10537
Division of Soil Science and Agricultural Chemistry
IARI
SSAC - 605
TERM PAPER
on
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DesertificationAubreville(1949) defined it as the changing
of productive land into a desert as the result of ruination of
land by man-induced soil erosion.
He associated it with the humid and subhumid tropics where
he worked.
UNEP (1992) defined desertification as land degradation in
the arid, semi-arid, and sub-humid areas resulting from
various factors, including climatic variations and human
activities.
Desertification usually begins as a spot on the land-scape
where land abuse has become excessive.
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The causes and development of desertification
Desertification
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classes of desertification: Slight: Little or no degradation of the soil and plant cover has
occurred.
Moderate:
(1) 26-50% of plant community consists of climax species, or
(2) 25-75 % of original topsoil lost, or
(3) soil salinity has reduced crop yields 10 to 50 percent.
Severe:
(1) 10-25 % of plan community consists of climax species, or
(2) erosion has removed all or practically all of the topsoil, or
(3) salinity controllable by drainage and leaching has reduced cropyield by more than 50%.
Very Severe:
(1) Less than 10% of plant community consists of climax species, or (2) land has many sand dunes or deep gullies, or
(3) salt crusts have developed on very slow permeable irrigated soils.
Dregne (1986)
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OCCURRENCE OF DESERTIFICATION
Desertification affects nearly all of the arid
regions, to varying degrees, except for theextremely arid climatic deserts such as the
Sahara, Atacama, and Taklimakan.
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Process wise desertification in India
(mha)
Ajai et al., 2009
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State-wise statistic of desertification
Ajai et al., 2009
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Consequences of desertification
Reduces the landsresilience to natural climate variability.
Soil becomes less productive.
Vegetation becomes damaged.
Downstream flooding, reduced water quality, sedimentation
in rivers and lakes, and siltation of reservoirs and navigation
channels.
Food production is undermined.
Desertification contributes to famine.
UNCCD
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National Action Programme to Combat Desertification
India is a party to UNCCD and MoEF is the NationalCoordinating Agency for the implementation of the UNCCD
in the country. The objectives are:-
1. Community based approach to development
2. Activities to improve the quality of life of the localcommunities
3. Awareness raising
4. Drought management preparedness and mitigation
5. R&D initiatives and interventions which are locally suited6. Strengthening self governance leading to empowerment of
local communities
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Case study
2.34 million sq. km.
85% in India
91% in Rajasthan
covers 61% of Rajasthan
100-500mm90% -July and September.
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1.Introduction of fast growing exotic tree
species
indigenous tree species are few and
extremely slow growing.
about 115 Eucalyptus spps, 73 Acacia spps.
and 170 miscellaneous spp. were introduced.
Acacia tortilisfrom Israel has been adjudged
the best fuel-cum-fodder species for the
desert.
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2. Stabilization of shifting sand-dunes
Low-rainfall areas (150 mm to 400 mm), huge shifting sand
dunes
Techniques of afforesting standardized after 10 yrs
Techniques consist
(i) protection against biotic interferences;
(ii) treatment of shifting sand-dunes by fixing barriers using thelocal shrub material to protect the seedlings from burial or
exposure by the blowing of sand;
(iii) afforestation of such treated dunes by direct seedling and
planting.
Both indigenous and exotic species have proved successful
Phog (Calligonum polygonoides),a naturally growing shrub,
root which works as effective sandbinder
Acacia albida was used to stabilize 60,000 ha of sand-dunes
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3. Shelterbelt plantations to reduce wind velocity
Shelterbelts and tree-screens consisting of a row of trees viz.
Acacia tortilis, Tamarix articulata and Azadirachta indica
flanked by two rows (one on each side) of smaller trees like
Acacia senegal, Prosopis juliflora etc., with two rows (one on
each side) of shrubs like Aerva tomentosa, Zizyphus
spinachristi, Calligonum polygonoideswere found to be veryeffective.
Shelterbelts reduced the wind velocity by 2046% on the
leeward side for 2H10H during the monsoon period.
Rajasthan State Forest Department has so far covered about38,000 row km area under shelterbelt
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4.Ecological regeneration through aerial seeding
Aerial seeding of seed pellets was done in 56 ha of military
range areas in Barmer district at two sites: the duny sandy
plain of Jalipa and the rocky hill ranges of Jasai village.
Two methods of seeding-helicopter and manual
broadcasting of pellets were used
Manual broadcasting of pellets was found better than aerial
seeding by helicopter.
Under controlled conditions in the Jasai area, the plant
population at sandy and rocky area were 6 and 3 individuals
per sq. m. , respectively.
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5. Ecological restoration and regeneration of the minedwastelands
Gypsum and limestone mined wastelands
Four plots-1 ha each-4 treatments
Control, micro-catchment area, half moon structure andridge and furrow system.
Seven indigenous and exotic species of trees, four of shrubs
were selected for plantation and rooted slips of grasses.
More than 90% of the plants survived
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Time sequence of regeneration of rangelands in
various habitats of the Thar desert.
Shankarnarayanan in Ishwar Prakash,1988,
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Conclusions
Overgrazing, extraction of food, fodder and fuelwood causeddesertification.
The degraded rangelands of the Thar desert show
tremendous resilience for regeneration when the influence
of biotic factors are removed.
However it is possible to recover these desertified land
through different practice.
Therefore, strenuous efforts should made towards
desertification control.
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