SourCeBook oN remoTe SeNSiNg aND BioDiverSiTy iNDiCaTorS

Recommendations

Info

Sourcebook on Remote Sensing and Biodiversity Indicators maps, using MODIS data, and published the results in a national newspaper. This was used in a geographic information system (GIS) to create edge-area maps of each forest patch. The change over time in this ratio is reported per department. All of these data are available online at http://www.landcover.org. 4 Case Study 4.2: Dry Tropical Forest Mosaic of eastern Cambodia Author: Colby Loucks, World Wildlife Fund US (WWF) Indicators: dry tropical forest extent Potential monitoring scales: landscape, small and large nations Sensor: Landsat TM and Landsat ETM+ Imagery cost/hectare: free Limitations on accuracy: seasonality, fires, ground-truth data a. Introduction The dry forests of eastern Cambodia are the largest contiguous area of dry forest in all of mainland Southeast Asia. Cambodia’s eastern plains are dominated by deciduous and dry dipterocarp forests, interspersed with patches of semievergreen forest. Many large mammal species require all three of these forest types to hunt or breed sometime during the year. A study by the WWF produced an estimate of the distribution and change in extent from 1990 to 00 of three types of forest: semievergreen, mixed deciduous, and dry dipterocarp. It estimated how much of each type was converted to agricultural, residential, or barren land cover. b. Methods The analysis was based on two Landsat images of the same area, both from the dry season: December 1, 1990, and February 13, 00 . WWF collected ground-reference data during surveys of the southeast portion of the study area. WWF also collected GIS data on topography, roads, villages, protected areas, and rivers to provide contextual information. These data were supplemented with interviews with local experts. The analysis of the two images began with geometric registration of the 00 image and then coregistration of the 1990 image to the 00 image. This was achieved with subpixel accuracy (less than 30 metres). The two images, each with six data layers, one for each reflectance channel, were then combined to create a single two-date file with 1 data layers. This file was then used in an unsupervised classification to produce 50 classes, or clusters of data with greatest similarity among the 1 layers. These classes were then labeled (i.e., assigned to one of several possible cover types), referring to the suite of reference and supplemental data collected. Additional field surveys were conducted in areas where interpretation of the raw images was most difficult and where classification results were most suspect. The latter was evidenced by areas where several classes were interspersed in the results and where results appeared to conflict with experts notes. The data from the second survey were used to refine the initial classification. The final map was then filtered with a 3x3 grid cell box neighborhood focal filter. This filter returns the majority value to the centre pixel and filters out isolated pixels. c. Results Mapped results of the forest change analysis for Cambodia are presented in Figure 4. . We found that .9% of the dry dipterocarp, mixed deciduous, and semi-evergreen forests in the study area were defor-
Chapter 4. Trends in Selected Biomes, Habitats, and Ecosystems: Forests ested over the 1 year time period (Table 4.1). The majority of the forest loss occurred near villages that existed in 1990. Expansion of these populated areas occurred over the 1 year period with the conversion of most of the forest to residential-agricultural lands. Additional forest loss was also found along road networks, several of which were created or improved since 1990. The semi-evergreen forests were deforested as a result of both conversion to swidden agriculture and deforestation along road networks that were built through these blocks of forests. We also found that 0.6% of the forests in the study area had regenerated (Table 4.1). The majority of the regeneration areas were from prior intensive timber operations. A small portion of the regenerating forest was from abandoned swidden agricultural lands found in semi-evergreen forests. Therefore we measured a net decrease in forest areas of .3% in the study area over the 1 year time frame. A majority of the study area still contains native land cover (89.1%), while approximately 9% of the study area has been converted to human-dominated land uses (i.e. residential or agricultural lands). TABle 4.1. land cover classes and area for the land cover change analysis (1990-2002) in eastern Cambodia. land cover classes are separated in static (non-change) classes and change classes. In the change classes, the text within the parenthesis indicates the general classes in 1990 and then in 2002. land Cover Area (km2) Percent of region Semi-evergreen forest 94.4 of analysis 12.0 Mixed deciduous forest (semi-dense) 186.3 23.7 Deciduous dipterocarp forest 409.5 52.2 grasslands-scrub 6.3 0.8 Seasonal wetlands 3.4 0.4 Water 7.6 1.0 Seasonally bare land/Agricultural land 40.3 5.1 Residential-agricultural mosaic 9.2 1.2 Change Classes Deforested area (intact forest to bare land) 15.5 2.0 Degraded forest mosaic (intact forests to disturbed forests) 7.0 0.9 Regenerating forest mosaic (bare soil-agriculture to secondary forests) 3.8 0.5 Regenerating swidden agriculture (agriculture to secondary forests) 1.1 0.1 Water expansion (agriculture to water) 0.8 0.1 Total 785.3 100.0 43
Page 1: Secretariat of the Convention on Bi
Page 4 and 5: Sourcebook on Remote Sensing and Bi
Page 94 and 95:
Sourcebook on Remote Sensing and Bi
Page 96 and 97:
Page 98 and 99:
Page 100 and 101:
Page 102 and 103:
Page 104 and 105:
Page 106 and 107:
Page 108 and 109:
Page 110 and 111:
Page 112 and 113:
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198 and 199:
Page 200 and 201:
Page 202 and 203:
Page 204 and 205:
show all

SourCeBook oN remoTe SeNSiNg aND BioDiverSiTy iNDiCaTorS

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?