## 3 Results and Discussions
### Supervised Classification  
Displaying the results of the supervised classification for images of three satellites to southern marshes for 1977 and 2017, Figure 5 showed the large variation in the area of the water bodies and the vegetation within 40 years. The area of water bodies in the image of Landsat 2 in 1977, Figure 5A was 3173.92 km\({}^{2}\), especially the large expansion for Hammar Marsh. While the area of natural plants reached to 5898.54 km\({}^{2}\), it represented the biggest area within the Hawaiian and central marshes. The agricultural areas were centered around Hawiza, and the central marshes were 4600.95 km\({}^{2}\), on branches of Tigris River in Misan province and branches of Euphrates River within Thi Qar province. The barren area reached to 4257.31 km\({}^{2}\) in 1977. Note from Figure 5B illustrates the supervised classification of Landsat 8, that the area of water bodies in marshes has shrunk in 2017 to 753.79 km\({}^{2}\), converted to a barren area. As well as, area of natural plants shrinks to 1486.16 km\({}^{2}\), agriculture areas to 3806.72 km\({}^{2}\). In other hands, the area of barren lands increased to 11,883.47 km\({}^{2}\) compared to 1977. For comparison with the image of Landsat 8, the results of supervised classification to Sentinel 2 in 2017, Figure 5C, showed that water area was 544.62 km\({}^{2}\), and the agriculture area reached to 3275.38 km\({}^{2}\), less than their values in Landsat-8. Meanwhile the area of the natural plant was 1539.86 km\({}^{2}\) and barren areas were 12,596.24 km\({}^{2}\). The difference in areas of land cover and land use between the images of Landsat-8 and Sentinel 2 came back to clear contrast in the recorded spectral reflectivity for land surface classes (water, natural plant, agriculture and barren lands) in the marshes region, especially within the spectral bands Red Edge 5, 6, 7, 8A, NIR 8 and 9 in Sentinel 2. These bands are useful for moisture land mapping and provide information to vegetation and water monitoring for marshes. There are also the spectral bands SWIR 11 and 12, in Sentinel 2, that corresponding to SWIR 6 and 7 bands in Landsat 8, Table 1. The bands SWIR 11 and SWIR 6 to distinguish water bodies, compared to SWIR 12 and SWIR 7, due to its sensitivity for plants and soil moisture content. While the thermal bands 10 and 11 are in Landsat-8 only, they are used to distinguish shallow water areas. Therefore, the area of water bodies in the image of Landsat 8 bigger than in Sentinel 2, although the two images were taken in the same year. Figure 6 shows a comparison between areas of land cover classes in Iraqi southern marshes for three satellite images in 1977 and 2017. The decreases in water, agricultural lands and natural plants conversely lead to increases in barren areas during 1977-2017. The drying up of marshes since the 1980s and conversion to barren area, destroying the unique ecosystem of marshes, represented bigger environmental disaster, changed features of life and nature in it, which led to a large migration of its residents and neighboring villages. High temperature and evaporation rates accompanied low water revenues of the marshes, as well as decreased precipitation. All these reasons have affected the environment of the marshes and their areas and changed their environment significantly. Despite an inundation of the marshes by water, it has not reached half of its previous area in the 1970s. The drying processes are not solely responsible for the deterioration of the ecosystem of the marshes. There are many factors which have contributed to this deterioration over the years, including the poor water management of the marshes after the re-inundation, and, affecting Iraq and the marshes in particular, global climate change.