Desertification can be defined as the land degradation in arid
Desertification can be defined as the land degradation in arid, semi-arid, and dry sub-humid regions caused by climatic changes and human activities that lead to serious ecological, environmental, and socio-economic threats to the universe. The effects of desertification include a set of important operations which are dynamic in arid and sub-arid regions, where water is the essential limiting factor of land use execution in such ecological system (Sandy deserts being one of the most dangerous ecological problems in the world). Many countries in the arid and semi-arid areas, including Iraq, are witnessing such desertification problems. To assess desertification problems, different methods were proposed. In Europe Mediterranean areas, the soil loss caused by water erosion correlating with loss of soil nutrients status was the most serious problem in those areas. Salinization and wind erosion were more often to occur in arid Mediterranean regions. Environmentally sensitive areas to desertification shows various sensitivity status to desertification for different reasons. For instance, some regions present high sensitivity to low rainfall and extreme events due to low coverage of vegetation, low durability of vegetation due to dryness, sharp slopes, and excessive man-made damage. Loss of land capacity falls into two overlapping systems: Human social system, and the natural ecological system. The degree of land degradation can be evaluated according to those two systems. Desertification indicators are indicators showing the level of risk to desertification in order to follow a plan to mitigate desertification. Those indicators should be based on remotely sensed images (soil, climate, geology, and topographic data). At a scale of 1/25000, the effect of socio-economic system is uttered through land use pattern. Different types of environmentally sensitive areas to desertification can be featured and mapped using different symbols for evaluating land capacity to resist and further degradation or support different land uses.
1.2- Aim of project
The aim of this report is to show how the advanced usage of remote sensing can limit and detect desertification by analyzing data based on different parameters; which should be based on four categories defining the quality of soil, vegetation, climate, and land management.
Chapter 2: Materials
2.1-Data required
In order to evaluate the desertification sensitivity index (DSI), three main indices are required which are the thematic layer of soil quality index (SQI), Climate quality index (CQI),and the range of sand movement (crust indext(CI)). These indices are extracted from topographic data, geologic maps, and satellite images( through satellite sensors Landsat TM and Landsat ETM).
2.2-Satellites used
In our investigation to detect environmentally sensetive areas to desertification, two landsat satellites are significat; the landsat TM and landsat ETM. These satellites consist of detectors which produce signals relative to the mean amount of light reflected from a specific region, which correlates to the resolution of their sensors.
The Landsat Thematic Mapper (TM) sensor was mounted on Landsat 4-5, has images made of six spectral channels(bands) with a spatial resolution of 30 meters for Bands 1 to 5 and 7, and one thermal band (Band 6). The scene size is about 170 km north-south by 183 km east-west.
*Note that TM Band 6 is obtained at 120-meter resolution, but products are resampled to 30-meter resolution.
The Landsat Enhanced Thematic Mapper Plus (ETM+) sensor is mounted on Landsat 7, has images made of seven spectral channels(bands) with a spatial resolution of 30 meters for Bands 1-5 and 7, and a resolution of 15 meters for Band 8(panchromatic). The gain settings for all bands can be collected (high or low) for increased radiometric sensitivity and dynamic range, however Band 6 collects both high and low gain for all scenes (Bands 61 and 62). The scene size is about 170 km north-south by 183 km east-west.
*Note that ETM+ Band 6 is obtained at 60-meter resolution, but products are resampled to 30-meter resolution.
*Note the panchromatic band works similarly as the black and white film, it combines the visible spectrum into one bands allowing the sensor to observe more light and provide the sharpest image among the others.
Due to the multispectral sensors of the Landsat, we can monitor desertification through their images.
