Land Degradation Mapping World is under the threshold of food insecurity
especially in the developing countries. It is estimated that 790 million people do not
have enough food to eat. The issue was the focal point in the World Food Summit held in
1996 and it is pledged to reduce the number of hungry people to around 400 million by
2015. The grave situation is further
highlighted while celebrating the World Food Day 2000 to have “Millennium free from Hunger”. Several measures have been taken up in this
direction to achieve the mandate set up in the World Summit. Combating land degradation
and desertification is one of the measures. Land being a finite natural resource, there is no
alternative option but to take remedial measures to normalize the degraded lands to
enhance food production and restoration of fragile ecosystem as well. Degradation of land
is the result of both natural and biotic factors. Human and animal pressure on land, over
exploitation of soil and water resources, unscientific land use, and natural calamities
like drought, floods and earthquakes are major factors responsible for land degradation.
Salinity and alkalinity of soils, soil acidity and waterlogging are common in the command
area where high inputs agriculture is practiced. These are affecting the agriculture
production severely and are also responsible for damaging the eco-system. Besides, mining
and shifting cultivation are also recognized as factors of land degradation in Land degradation is defined as a human induced or
natural process that negatively affects the land to function effectively. It is estimated
that some forms of degradation of land constituting 75% of the earth’s usable
landmass affecting 4 billion people in the world. About
15% of the world population is affected by land degradation which is likely to worsen
unless adequate and immediate measures are taken to arrest the degradation processes.
Desertification is a land degradation phenomenon occurring in arid, semi arid and dry
sub-humid areas in the World. It covers 40% of the earth surface and affects 1 billion
people who are tilling the land for survival (Anon 1999). The magnitude of land degradation and
desertification and their consequences became the international issue since 1977 and
pledged to combat the land degradation in the World, in particular in the developing
countries (UNCOD, 1977; UNEP, 1978, 1992; UNCOD, 1992, Barrow, 1991). Efforts at global and national level have been made
to focus the consequences of land degradation on food, employment, environment, health and
humanity. The GLASOD model of assessing desertification developed by UNEP is a
demonstration at international level to focus the attention of the developed and
developing countries in the world on the desertification and land degradation. It is
essential that all the counties having large scale of desertification should adopt
suitable strategy to combat the menace of land degradation. Agenda 21 of the United Nations Conference on
Environment and Development emphasized the need of wide range of activities to address
land degradation in general and desertification in particular. In response to these challenges, 100
countries have signed the convention to combat desertification in 1997 (Anon 2000). As a follow up action, a task force has also been
set up to combat desertification in the Ministry of Environment & Forest, Govt. of
India and National Action Plan has also been formulated (Anon 2001). To combat desertification our strategy should be
“think globally and act locally”. The GLASOD technique for assessment of
degraded land demonstrates the implications at global level. However to develop a strategy
to arrest land degradation, there is a need of database both at macro and micro level
planning for reclamation of degraded lands. The information on extent and spatial
distribution of degraded lands is thus a pre-requisite for formulation of developmental
action plan. In Table 1: Statistics on
Degraded Lands in
Most of the statistics published by different
organizations on degraded lands are only estimates lacking scientific base for data
acquisition and does not have spatial extent. Department
of Land Resources (DOLR), Ministry of Rural Development carried out wasteland mapping
using remote sensing technique during 1985 and 2000. The
mapping carried out during 1985 using 1:1 million-scale satellite imagery accounted for
53.3 m ha area as wasteland. Subsequently, an
estimate of 63.85 m ha (2000) and 55.27 m ha (2005) of wasteland in the country has been
reported based on 1:50000 scale mapping. The wasteland map of DOLR cannot be considered as
such a base data for degraded lands. Some of
the categories of the wastelands, such as, the steep sloping lands, scrub and without
scrub lands, snow covered lands etc. have been recognized, as wastelands, which are not
necessarily, be the degraded lands. Rapid
Inventorying of Degraded Lands Remote sensing from satellite platform in
conjunction with ground verification offers a potential means of surveying all the regions
of the globe. Satellite remote sensing offers
monitoring of much larger area in a short period than ground survey and helps in targeting
key ground observation. The processes and
extent of land degradation can be perceived better using remote sensing technique followed
by verification on the ground (Anon 2000).
Recognizing the importance of development of
degraded lands, the Department of Agriculture and Cooperation, Ministry of Agriculture
initiated land degradation mapping on district basis using remote sensing technique during
Eighth Five-Year Plan. The objective of the
mapping is to generate realistic information on degraded lands and their spatial
distribution to undertake developmental planning. Accordingly,
Soil and Land Use Survey of India (SLUSI) developed a methodology for land degradation
mapping using remotely sensed data. Importance
of Land Degradation Mapping Development of degraded lands is one of the options
to enhance agricultural production in the country. Natural
Resource Management Division, Ministry of Agriculture initiated the land degradation
mapping during Eighth Five-Year Plan based on the following factors. r No realistic database on degraded lands is available
in the country r Statistics produced by several agencies on degraded
lands vary widely r Varying nomenclature to describe the land
degradation r Techniques of data acquisition differs r Strategic planning to combat the menace of land
degradation r Land development with scientific means for sustained
agricultural production and eco-development The Ministry after due consultations with various
National and State organizations dealing with mapping of natural resources using remote
sensing techniques has decided a mapping strategy. Recognizing
the gravity of the problem and the tremendous workload, it is necessary to take up the
task of land degradation mapping under mission mode at national level. Conceptualization
of Mapping The mapping has been conceptualized as a four-tier
approach comprising kind of degradation, severity of degradation, degradation under major
land use and major landform. The various causative factors both natural and biotic
degradation processes, viz., water and wind erosion, waterlogging, salt affliction,
shifting cultivation, mining, etc. The methodology for land degradation mapping has been
developed accordingly. Methodology The methodology for land degradation mapping using
remote sensing techniques developed by the organization is based on the expertise in the
field of soil survey and remote sensing acquired since inception. Multi-date False Colour
Composite (FCC) generated out of IRS LISS II sensor has been used for interpretation
purposes. Standard procedure of image interpretation techniques covering the steps i.e.,
recognition, identification, analysis and inferences have been followed for mapping
purposes. Legend
Development Legend development is a state of art in land
resource mapping to depict the various land information on map in a comprehensive manner. According to the conceptualization of mapping,
various kinds of degraded lands have been symbolized alphanumerically. For example water
erosion has been symbolized as “We” whereas degradation due to water logging has
been denoted as “Wl”. The kind
of degraded lands have further been segregated based on degree of severity and have been
denoted by suffixing a numerical 1 to7. A land
suffering from water erosion “We” could therefore be further segregated based on
degree of severity. For example water erosion
with severe and very severe sheet, rill and few gullies could be denoted as
“We1” and “We2” respectively. Similarly, deep ravines having depth
greater than 3 m could be symbolized as “We6”. To identify and delineate the occurrence of various
kinds of the degraded lands under major landscape is essential for proper planning of any
developmental activities. Keeping this in
view, the whole country has been divided into four major landscape classes as per
universal terminology (Anon, 1993). The landscape classes viz.; plain land, undulating
land, rolling land and hilly/mountainous land based on slope ranges has been considered in
the construction of mapping unit. Small
English alphabet denoting the landscape class has been used as suffix in the mapping unit. For example, plain land with very severe water
induced soil erosion is depicted on map as “We2a”.
In order to make the legend more users friendly and to understand the
degradation process under different land uses, the mapping unit has been further expanded
with a numeral as suffix indicating the major land use classes. Legend for
Land Degradation Mapping r Kind of
Degradation
r Degree of
Severity of Degradation
r Major
Landscape Classes and
r Major Land
Use Classes
r Chemical
Characteristics of Salt-affected Soils
Source: United State Salinity Laboratory Staff (1969);
Diagnosis and Improvement of Saline and Alkali Soils. Agriculture Handbook No. 60 Key to
Degree of Salinity and / or Alkalinity
Note:
Change in land use as per image over that of shown on toposheet is to be indicated in
parenthesis. Example: Orchards, social forestry plantation tea, coffee etc. are
included under “ Status of Mapping:
SLUSI has so far covered 65 districts spread over in different agro-climatic regions of
the country. Spatial distribution of various kinds of degraded lands with extent in a
district is available in the report which is helpful for macro-level planning. It is an
in-house programme of the organization which has been taken in a limited scale due to over
burden with other ongoing activities. The mapping needs to be pacified with a mission
approach. Department of Agriculture and Cooperation and Department of Space took the
initiative of launching of National Mission for Soil and Land Degradation Mapping
(Venkataratnam and Das, 2002) which will help to accomplish the task of land degradation
mapping within stipulated time. Reclamation of Degraded
Lands: The land degradation mapping on 1:50,000 scale using remotely sensed data
provides the first hand information about the extent and spatial distribution of degraded
lands in a district that allows macro level planning for development of the degraded
lands. But reclamation of any kind of degraded land is a location specific issue that
requires to be dealt at micro level. Land reclamation aims at improving the soil productivity and
restoring fragile eco-system which is essentially the interplay between soil conservation
and degradation processes as illustrated below. Detailed database on soils and other associated information is
thus essential for soil and land reclamation purposes. District Information
System for Degraded Lands: Database with spatial distribution of various soil and land
attributes is a pre-requisite for development of strategic planning of any land
development programme. The district-wise data
base on degraded lands will not only help for rehabilitation planning of degraded lands
but will be the vital base for monitoring purposes. The
existing database of any land attributes could be updated using remote sensing technique
that will facilitate in identifying the changes being taken place due to dynamic processes
that are operating on land. The voluminous database thus generated often creates
problem in handling for compilation and analytical purposes manually resulting delay to
support the decision making process. The
technological advancement in the field of management of spatial data in the form of
Geographic Information System revolutionized not only the management of voluminous data in
a systematic manner but it allows manipulation, analysis and retrieval of map and
statistical information in desired format accurately and quickly. The information system on degraded land in the
country should be developed using remote sensing and Geographic Information System towards
strategic development of degraded lands and monitoring the status in a periodic time
scale. Such kind of information system will be
a valuable tool for management of degraded lands and national auditing as well (Anon,
2001). |
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