Diagnosis of Land Degradation in the Semi-Arid Area of Asia and Pacific Region 10-/
using Remote Sensing Data - JIRCAS's Case Study
Satoshi Uchida
Japan International Research Center for Agricultural Sciences (JIRCAS)
1-2 Ohwashi, Tsukuba, Ibaraki 305, Japan
presently Visiting Scientist of International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)
Patancheru 502324, Andhra Pradesh. India
Abstract
Land degradation which restricts the reproductivity of biomass appears at various areas in the world. In the semi-arid area the multiple types of land degradation happen to integrate to accelerate desertification. JIRCAS has implemented several research projects in collaboration with overseas institutes for the purpose of seeking sustainable land use system in the semi-arid area. This article describes the activities of case studies which have been adopted remote sensing data. This treats the physiographically specific topics in terms of land degradation appeared in the objective countries such as soil erosion in Pakistan and desertification of rangeland in Australia. The methodology to assess land degradation using remote sensing data should consist of the different stages of process, which are to identify the objective phenomenon from the image, to develop an
appropriate indicator, to produce dataset and to evaluate the availability of land resources. This article also mentions about the Interrelation between these stages,
1.Introduction
In recent years global environment issues have been argued in focus with quantitative measmement of objective parameters which may vary temporally and spatially .Once an estimated value is quantified and published, analyst who often utilize the secondary data may produce Wild life result. This problem is probable to occur in the estimation of global value accumulated with local data taken by nonstandardized methodology. Researchers expect to establish the methodology to assess global environment using remote sensing data as a quantitative information source. At this point it is necessary to discriminate the phenomenon whether it would be suitable as a target of remote sensing data analysis or not.
Land degradation, which is one of representative deteriorating factor of the environment, could be observed in the world wide. Land is a base to reproduce vegetation and its degradation corresponds to the restriction of vegetative activity by the change of growth conditions. Vegetative activity correlate with both agricultural productivity and environmental conservation. Land degradation tends to be an irreversible process, therefore in order to establish sustainable land use system it is important to make attempts to discover the area prone to land degradation as well as to monitor the progress of degradation .
Some typical phenomena of land degradation appear in the semi-arid area and they often cause the expansion of desert area. Desertification may be evaluated through vegetative activity on the surface but the difficulty comes from its temporal variation. Ground conditions which influence the growth of vegetation must be more suitable indicators of desertification. Representatively geomorphologic, chemical and physical degradation of soil can be identified to evaluate the state of desertification.
JIRCAS (Japan International Research Center for Agricultural Sciences) is one of the research i; institutes belonging to the Ministry of Agriculture, Forestry and Fisheries and has implemented collaborative research with overseas institutes. JIR.CAS has introduced remote sensing and GIS ~ techniques for the re some management of semi-arid areas. This article describes the outline of recent
JIRCAS's activity adopting remote sensing data for the specific topics of semi-arid area. The author will try to explain the scheme of research projects in view of standardizing the methodology to assess environmental conditions.
2.Delineation of Land Degradation Using Remote Sensing Data
The quantification of spatial behavior at the specific moment is an initial step to monitor the progress of land degradation. The capability of wide spatial coverage of remote sensing data is its advantageous feature. On the contrary the limitation of spectral variety and spatial resolution of remote sensing data often makes it difficult to discriminate the different appearance of land degradation. It is needless to say that remote sensing data cannot apply to analyze any types of land degradation.
In the previous studies applications of remote sensing data to land degradation have been performed to delineate the state of soil erosion, soil salinization, water logging, foliage deterioration, etc. The experimental site of these examples spread over various parts of the world of which considerable percentages have treated cases in the semi-arid climatic conditions. The reason of this selection is supposed that the semi-arid area would be fragile against the environmental change in terms of its vegetative activity and land could be degraded in association with vegetation coverage over the land.
There are two types of soil erosion, one is wind erosion and the other is water erosion. Both of erosion types affect the geomorphologic feature of land as well as distribution of top soil. Remote sensing data can detect directly the geomorphologic feature if spatial resolution is small enough to discriminate the pattern of eroded topography. Another method to evaluate the strength of erodibility which is a kind of indirect way, adopts an empirical parameter in correspondent with controlling factor by coverage of ground surface. Many examples have published to estimate C factor of USLE equation from vegetation index or other indices calculated from multispectral data of remote sensing. The appearance of saline soil or water logging area could be interpreted from the remote sensing imagery .The problem of reproductivity of the same result by manual interpretation may become critical if quantitative analysis is necessary. The extraction of salt affected or water logging area requires the intonation not only spectral characteristics but its geographical location in association with the topography of objective area. It is significant to introduce GIS for the purpose of extracting and monitoring salt affected or water logging area in the digital based remote sensing data analysis.
The growth of vegetation is influenced by the factors of land management besides climatic and " c' nutrient features of land. In case of agricultural land vegetation coverage varies with the cropping pattern therefore land degradation cannot be evaluated by only the change of vegetation. Apart from agricultural land and manmade land use, vegetation coverage may indicate the magnitude of land degradation. The rangeland in the semi-arid area is a good example to show the tendency of deteriorating, vegetation associated with land degradation. The methodology to monitor vegetation coverage using remote sensing data has been developed and examined its applicability by number of researchers for these decades.
Table 1 summarizes the use of remote sensing data to delineate land degradation in the semi-arid area. This table suggest~ that remote sensing data would be evaluated as a useful information to monitor land degradation although the methodology of quantitative measurement has not been established. Studies on standardization of method of analysis are required primarily at this stage.
Table 1 Use of remote sensing data to delineate land degradation in the semi-arid area
| Degradation Type |
DElineated Feature |
Methodology |
Remark |
| Water Erosion |
Gully (Topography) Coverage (Control Ractor) |
Interpretation, Texture Indices by multiple bands |
Empirical factors would be included |
| Wind Erosion |
Sand move |
Interpretion, Band calclulation |
Difficult to find position |
| Soil Salinization |
Soil color change |
Interpretation, Band calculation |
difficult to be quantified |
| Foliage Deterioration |
Density (Biomass) Species change |
Vegatation index etc. Classification |
Seasonal change should be considered |
