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 earths 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.
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 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
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.
Orchards, social forestry plantation tea, coffee etc. are
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).