In the context of the constitution of environmental GIS database of west Asia, satellite remote sensing and GIS technology were applied as essential tools to address important aspects of environmental monitoring. A multi-temporal analysis of satellite derived monthly vegetation index data allows to create a land cover map of the study area. The land cover map with to create a land cover map of the study area. The land cover map with satellite image of NOAA AVHRR represent the basic elements of the environmental GIS database. The GIS is constructed in such way to envelop all necessary environmental layers (soil, geology, rainfall, elevation, temperature, moisture, albedo… etc). These layers were digitized and geo-coded to fit with latitude and longitude coordinates system as well as this the original satellite images representing the study area. Based on this environmental GIS database a desertification study will be achieved, this study will include drought assessment, desertification modeling and the construction of desertification monitoring system.
Environment is considered as a worldwide phenomenon, which is characterized with sensitive equilibrium between its components; water, air and soil. The changes that take place in many areas of the world, as a result of human and ether natural activities, could have the greatest impact on the environment. The main goal of this research is to enable countries affected by desertification and drought to be associated to remote generation of knowledge and techniques related to remote sensing and GIS, which are needed to solve their specifics problem in field of desertification control. And thus, to contribute to a better natural resources management and economic development.
West Asia region is facing environmental problem of land degradation and desertification. Whereas the most of Arabian Peniusula is free of perennial vegetation. For most areas shifting sand dunes are incapable of sustaining plants life. Most of marginal lands in west Asia are permanent pastures of 1.16 millions sq. km, and 85% of them are considered in danger to desertification. These marginal lands are subject to human activities and susceptible to inappropriate land use practices, such as overgrazing, fuel cutting and inadequate cultivation. The use of new and appropriate technologies should be of great help to understand the degradation process, to evaluate the actions already taken to combat this degradation and to design new methodologies to improve effects of future action. As the land cover is a main environmental parameter affected by desertification, the research focus on developing a detail land cover map of west Asia using satellite data such as NOAA AVHRR(1 km resolution), landsat and Resures -1. Others environmental parameters such as albedo, temperature, misture, rainfall, geology …. Etc. will be taken in consideration and used as input jointly with land cover data will be entry data for desertification analysis, modeling and monitoring.
West Asia generally characterized by arid climate, the southern part is extremely arid. However high precipitation occurs in coastal mountain ranges and in the extreme north and northeast parts. Further south, however, precipitation decreases sharply producing a semi-arid belt over the a Syrian steppes or Badia. The eastern Mediterranean countries are influenced by Mediterranean frontal depressions, the average precipitation in this region ranges from 1500 mm (Lebanon mountain ranges and Mount Hermon) to 70 mm in the Syrian steppes. Egypt climate is extremely arid and average precipitation is about 10 mm. Arabian peninsula generally characterized by a hot dry climate caused by air masses moving from the eastern Mediterranean towards the Arabian Gulf. The rainfall in Arabia peninsula ranges from 300 mm in the eastern Red Sea Mountains to 10 mm in the Rub Al-khali in the southeaster.
The general morphology of the study area is flat though relatively narrow mountain ranges extend along the coastlines of the Red Sea, the Mediterranean sea and the Guld of Oman. Mountains and plateaus are found mainly in the north with mostly low relief features, and include the Palmyrian Mountains and the Hauran and hamad plateaus. Higher mountains (the Zagros ranges) are encountered in the north east of Iraq.
Data and Materials
The base data used in this study are 1-km NOAA AVHRR 10-days composite data sets for April 1992 through March 1993. While the 10-days maximum normalized difference vegetation index (NDVI) composite data are used to classify the vegetation land cover features. Resures-1 data were used to define ground truth data and to perform visual interpretation at the post-classification level. Several thematic maps were used as sources of information for ground truth data such as Land use maps of Jordan and Syria. To supply our GIS database with layers and information representing environmental parameters such as soil geology, rainfall, temperature…. Etc, we used satellite data and maps covering the study area extracted from Arab world atlas, Tubingen Atlas of Middle East and other sources of maps.
As it mentioned before the tools of remote sensing and geographic information system are utmost important to achieve such study, therefore, satellite images are used to produce as it will be mentioned after such as land cover, temperature, albedo, moisture, evaportranspiration and dryness indices,. Scanning utility was used to enter data in form of maps. To be able geocoding these data with others and manipulating all layers of information, GIS techniques will be used to analyze data and create the derived information related to environmental deterioration in form of land degradation and desertification.
Land cover database
The reduction of vegetation cover is said to be an important indicator or desertification. Therefore the land cover database constitutes the basic element for desertification studies and control. In this study NOAA AVHRR (NDVI 10- days composite data set for one year, and visible channels 1 &2) data and other thematic maps were used to produce the land cover database.
The land cover study falls into 1- Cluster analysis of the NDVI 10 days composite data set for one year in total 36 data set. 2-Histograms analysis. 3-Ground truth collection and analysis. 4-Applying a supervised classification reules in form of three structure to create the land cover map.
As final result we have the following land cover classes with the system codes adopted by the working group”1-km land cover data base of Asia: Table (1)
|Grass & shrubs||162|
|Dry land (desert)||194|
Environmental GIS databases
A geographic information system (GIS) is designed for collection, storage and analysis of objects and phenomena where geographic location is an important characteristic or critical to analysis. The information in a GIS is presented in two basic forms, as maps and as tables.
The components of environmental GIS database, which from the structure of out GIS are described as follows:
- Data input The data input are converted from their existing form (digital or hardcopy) into standard digital data sets form.
- Data storage and management. This component reflects the structure of database, the position, linkages (topology) and attributes of geographical elements (points, lines and area)
- Data analysis and transformation. This means the achievement of transformation needed to remove errors from data or to update the data, on the other hand the data manipulation and analysis functions determine the information could be generated and extracted by GIS layers(dryness, erosion, desertification, …etc).
- Data output and presentation. The results will be in form of maps, tables of attribute values and test describing the final results. These results will be copied on CD-ROM for data storage and distribution.
Environmental parameters included in the GIS.
The study of the environmental problems needs the analysis of various parameters, which could be falls into physical, climatic and socio-economic parameters the following environmental parameters constitute out GIS layers:
- Rainfall and Water balance
- Wind and pressure
- Dryness index
- Political boundaries
- Land Cover
- Koppen Eco-system
- Population density
The context of this actual presentation doesn’t permit to give details about these parameters.
Desertification & desertification Modeling
The problem of desertification in arid and semi arid areas has a long history through the past centuries. It has always been an overlap of long-term changes in climate and human activities. With the rising population and, therefore, growth in consumption of the very limited resources, scope and intensity of interface with ecosystems by human activities grow rapidly, leading to sever degradation of vegetation, soil and water resources, which compose the natural resources of human existence. Desertification is manifested as one of typical environmental degradation forms and it constitutes a result of land degradation. This study emphasized on desertification processes, causes and indicators occurring in west Asia, then desertification analysis, modeling and monitoring.
Magnitude of the problem
With the consideration of climatic data, an estimated area of 36.3% of earth’s surface is considered desert. Based on satellite data the world’s desert is reported to 42%. The difference of the two estimations is interpreted as the desertified area by human intervention and pressure. Talking about soil salinity as form of land degradation, and the improper irrigation system as main cause of salinity. It is reported that the world lose 43 million hectares of irrigated area for food production, which means the deterioration of 30% of irrigated area and the lose of it’s fertility. The area of rainfed agriculture in the world arise to 452 millions hectares, the damaged part is about 42%. The rangeland area is approximately 4556 millions hectares, 73% of this land cover are considered as damaged. We note that 70% of agricultural land (27% of earth surface) undergoing of Desertification. Thus adding the desertified area, a total of 63% is consider unused for agricultural productivity against just 12% of earth surface which is effectively used for agricultural activities. Regarding the study area, it is considered that the total amount and seasonal incidence of rainfall chiefly determine the ecology and productivity of west Asia. Rainfal is low, unpredictable and highly variable, and prolonged droughts are more the rule than the exception. Most of the countries are classified by the FAO as low-rainfall areas, in that most of their land area is arid or semi-arid. Natural aridity is a major constraint to productivity and very little can be done to change it, However, man could balance his action with respect to the hydrologic cycle so that a given amount of water might serve his needs without undesirable side effects.
Process of Desertification
The high population pressure causes the increasing uses on grasslands for agriculture. If, however, people occupy a semi-arid zone that under-going drought, there is a strong tendency to overwork grazing lands and croplands to offset declining yields. This situation increases the stress on the landscape, leading to severe damage to soils and plants. Even after the drought ends, the weakened landscape is unable to recover and the affected area is susceptible to desertification. This illustrates a process of desertification from the interaction of land use and climatic process. There are many interactions between processes and their causes on one hand and processes and their consequences or indicators on the other. So some processes may appear as causes and others appear as indicators processes may appear as causes and others appear as indicators of desertification. The main processes within the context of desertification are: vegetation degradation, soil erosion, salinization, soil impoverishment, sand accumulation, formation of skeletal soil, overgrazing, over-cultivation and cultivation of skeletal soil, overgrazing, over-cultivation and cultivation in marginal lands, shrubs and forests cleaning and deterioration of adapted socio-economic systems. However, the following features characterize these processes :
- Reduced plant cover with lower production.
- Reduced soil cover, especially topsoil by erosion.
- Reduced soil fertility, and increased soil salinity.
- Reduced soil moisture reserves and agricultural capacity.
Causes and factors of desertification
The main factors are climate change and population pressure, these factors are considered as causes, which influence many others causes among them are listed below :
- Over-cultivation and overgrazing
- Forest cleaning and over-exploitation of forests
- Cultivation in marginal lands
- Ploughing on steep slopes
- Lack of research and applied research
- Environmental pollution
- Over-use of water for irrigation (over pumping)
- Sand dune movement
- Lack of government legislation protecting environment
- No afforestation
Indicators of desertification
The result of desertification process manifests in many ways as indicators of desertification, these indicators could be used to assess the status of desertification as also the susceptibility of an environment to desertification. The following may be considered as indicators of desertification caused by the processes described above :
- Increased surface rock area and increasing of bare land
- Dominance of invador plants (unpalatable species)
- Dust storms
- Reduction of pasturelands
- Soil erosion and land degradation
- Sand-dune formation and sand movement
- Decrease of soil fertility
- Decrease in productivity
- Crust formation
- Drop in water table
- Vegetation covers decreasing
- Permanent loss of indigenous plant species
- Deterioration of the economy and Decrease of income.
Desertification modeling & Environmental monitoring system
Desertification modeling and environmental monitoring will be the subject of the next phase of this research study. In term of desertification modeling, we will try to link desertification factors and causes to create a desertification map. This modeling system should allow to up-to-data the desertification map periodically in function of dynamic parameters (rainfall, temperature..).
The techniques developed for monitoring environmental variables from satellite data may involve thresholding, change detection aims to construct an “early warning system” which should be capable to estimate the amount and duration of rainfall, to assess the soil moisture situation, to detect changes, to provide information on trends of vegetation development. Additionally and in term of desertification, monitoring can be useful to detect areas where soil erosion is taking place, where vegetation is being destroyed or where sand dune are beginning to shift.
- Murai, S. 1991, Application of Remote Sensing, AARS, Tokyo.
- Unesco, UNEP & UNDP, 1980, Case studies on desertification, Unesco. Paris.
- Beaumint, P. 1978. The middle east-a geographical study, wiley, New York & Toronto.
- GTZ, 1988, Desertification in the middle east, GTZ, Germany.
- Elmehirk, Y. 1981, Environmental monitoring for Arab world, RSS, Amman.