LandUse Change Detection of Paddy Field to Eucalyptus in Songkram Watershed Using Satellite Data and In-Depth Interview

Abstract

General situation of land use and agricultural activities especially the conversion of the paddy field to the eucalyptus plot were studied using the Landsat-5 satellite image analysis with computerized system and compared with topographical map. The ultimate objective is to create a complete Geographic Information System (GIS), which will represent the current land utilization map, and detect land use change. In addition, field visits and in-depth interview with farmers were carried out in the study areas. The study was conducted in the 3 river basins with 3 different characteristics; The Upper Songkram watershed, The Lower Songkram River Basin (Mae Nam Oun Tributaries) and The Lower Songkram watershed. The findings from field visits and also the in-depth interviews with farmers were interesting which reveals that the conversion from farm crops, such as sugarcane and cassava, to the plot crops, such as rubber and eucalyptus, have sharply risen to 90% of the total area during the agricultural year 2000-2007. Rice cultivation is also a major occupation of the interviewed farmers, however, paddy fields are also threatened by annual flood, whereas upland paddy field yield low outputs. It can be observed that there is a tendency of introducing eucalyptus replacing paddy fields. This information has also been supported by the study of land use change during last five years, from 2000-2005, using Landsat images. It has been found that paddy field area have decreased by 2.56% which is equivalent to 64,761 rai of the total area of Songkram watershed (3,963,321 rai). However, eucalyptus plantation occupies 1,656 rai or 0.07% of the total paddy fields. The information has been classified on the basis of period of acquisition of the images as mentioned before. Even though since 2005, eucalyptus has been in favor of the farmers, it was not evident in the image which might be because the plants were not matured enough at the time of capturing images over the study area in 2005. Another reason might be that Landsat images classification can not be used for extraction of the eucalyptus trees from other trees grown in the paddy fields. Eucalyptus trees are normally planted with a distance of 2x3 meters, and farmers prefer to plant eucalyptus only on ridges of paddy fields.