Forest and land cover change detection is one of the major applications of satellite-based remote

Transcription

1 4.3 Trend, Nature and Rate of Forest Cover Change Extent of Ikhoho Forest Cover in the year 2000 and to 2010 Forest and land cover change detection is one of the major applications of satellite-based remote sensing. Satellite images from different dates for a particular geographic area are analyzed for changes in spectral patterns, and these changes are classified into appropriate forest change or land cover change categories. It is accepted that remotely sensed imagery can be used to monitor forest changes (Hame, 1991; Olsson, 1994; Coppin and Bauer, 1996; Collins and Woodcock, 1996; Hame et al., 1998; Franklin et al., 2000; Sader et al., 2003, Jin and Sader, 2005). One of the tasks in the field was to digitize the Images of Ikhoho forest cover of the different years so as to know the Forest covers changes. The task was done through the use of Arc view GIS 9.1 software in order to digitize the images downloaded from Google earth and extract only the areas covered by the forest. The Ikhoho Forest covers images of the year of 2000 and 2010 were digitized and the resulting forest area was as shown in the Figure 7 below. Figure 1: Ikhoho Forest area coverage in 2000 (Source: Original Map derived from Google earth Satellite image of 2000) 1

2 From the Figure 7 Green color shows the Forest Coverage in the year 2000 after the processing and digitizing Google earth satellite image through Arc-view GIS 9.1 software. The results show that the Forest area coverage is about 477 hectares. Image interpretation of Ikhoho Forest of the year 2000 shows that the Forest area covers the area of about 477 hectares; however origin size between 1982 to 2000 was 560 Hectares (MDC, 2005). The Forest area decreased by about 83 Hectares between This is about 25% of the total area decrease for 18 years since the establishment in This implies that the averages of 4.6 hectares of the Forest are being changed into other uses per year. The resulting forest area of 2010 as derived from Google earth image is as shown in Figure 8 below Figure 2: Ikhoho Forest area coverage in

3 (Source: Original Map derived from Google earth Satellite image of 2010) From the Figure 8 above Green color shows the forest area in the year of 2010 after the processing and digitizing using Arc-view GIS 9.1 software. The Forest area covers about 456 hectares. The image interpretation of the year 2010 shows that the Forest covers the total area of 456 hectares. Calculations show that the forest has decreased by 21 hectares between 2000 and This is about 5% loss of the total forest area of Generally, it has been observed that from 1982 (Introduction of the forest reserve) to 2010, a total of 104 hectares to be reduced/cleared. Table 3 below shows the Forest area change trend and rate. Table 1: Trend and Rate of Ikhoho Forest Cover Change Forest Cover (ha) Forest Area coverage ( ha) Rate per year (%) Year Change Change From From (ha) (ha) % 0.4% (Source: Field data, 2011) From the Table 3 above which show the comparison of forest cover from 1982 to 2010, it shows that the rate of forest cover change to the year 2000 was high as to compare from the year 2000 to This implies that at recent years there is a little change as compare to the previous years due to Environmental education Forest Area Cover Change from 2000 to 2010 Several techniques were used to determine the specific areas where deforestation had taken place between the years The digitized images of Ikhoho Forest were overlayed in order to get the spatial distribution of the changed area so as to detect those changes. The digitized image of the year 2000 were overlayed with the one of 2010 and the results were as seen in the Figure 9 3

4 Figure 3: Ikhoho Forest Cover maps of 2000 and 2010 overlayed (Source: Original Map derived from digitized Google earth Satellite image of 2000 and 2010) Figure 9 above shows the overlay image of the changed Forest area, where Green color represent the Forest area which is not changed while the black colors shows at the margins the Forest area which has been cleared. Macleod and Congation (1998) identified four aspects of change detection which are important when monitoring natural resources; these are detecting the changes that have occurred, identifying the nature of the change, measuring the area extent of the change and Assessing the spatial pattern of the change. GIS software has ability to overlay by creating some part of the overlayed layers. In this research the common areas of the two layers overlayed in Figure 8 was created the remaining part which is there at the margins which has been cleared is as shown in Figure 10. 4

5 Figure 4: Forest area which has been cleared from 2000 to 2010 (Source: Original Map derived from Satellite image of 2000 and 2010) 5