Occasional Publication No. 1, September 2015 Centre for Rural Development Studies, College of Natural Resources, Lobesa, Royal University of Bhutan Land Use Land Cover Changes in Bhutan: 2000-2013 Ugyen Yangchen1, Ugyen Thinley1 and Gudrun Wallentin2 1 2 College of Natural Resources, Royal University of Bhutan, Lobesa, Bhutan Correspondence: [email protected] Interfaculty Department of Geoinformatics - Z_GIS, University of Salzburg, Austria Abstract The urbanisation and infrastructure development in Bhutan are expanding at a fast pace and it has been observed that these processes are causing a decrease in the forest cover, agricultural area and shrub lands. This paper attempts to analyse land use land cover (LULC) changes in Bhutan over a period of thirteen years from 2000 to 2013. The images of Landsat 5, 7 and 8 were used for LULC classification and change detection. For validation, ground truth data of 2010 was used for assessing the classification accuracy. The results show that the largest proportion of the area (54%) in 2000 was under vegetation cover, the second largest (20%) was bare area and the third largest (14%) was under agricultural uses. The built-up areas constituted only 4% and rest was under snow, rivers and lakes. There was an increase of 10% and a decrease of 6% in the vegetation area in 2006 and 2013 respectively. Similarly, the agricultural area increased to 15% and then decreased to 8% during these years. There was a significant increase in the built-up area which accounted for 6% in 2006 and 14% in 2013. Also the snow cover increased from 4% in 2000 to 6% in 2006 and 9% in 2013. The overall accuracy of about 66% for 2000 and 2006 was fairly good. A low accuracy of 52% for 2013 may be partially because the spectral quality of the images was not good enough and partially due to the fact that the wavelengths of the bands of Landsat 8 satellite are little different than the corresponding bands of Landsat 5 and 7 satellites. However, the results ca be improved by using advanced methods of image processing and classification. Key words: Agriculture, Change Detection, Landsat Image, Land Use Land Cover, Maximum Likelihood Classification, Supervised Classification. Introduction Bhutan is located in the eastern Himalayas approximately between latitudes 260 41’ 52” N to 0 28 14’ 52” N and longitudes 880 44’ 54” E to 920 41’ 7” E. The total geographical area of the country is about 38,686 km2 and the elevation ranges from about 160 meters in the southern part to more than 7000 meters in the northern part. The general climatic conditions are subtropical in the southern parts, temperate in the central parts and alpine in the northern parts, with a small area under glaciers and perpetual snow on the higher ranges. According to the Census of Bhutan2005, the total population of the country was 672,425 persons out of which about 70 percent resided in the rural areas (NSB, 2014). Over the last several years, urbanisation and infrastructure development has expanded at a fast pace due to which not only the forest cover, agricultural area and shrub lands have decreased but also some other side effects have been observed (Giri and Singh, 2013). Similar processes have been analysed in the adjoining parts of the Himalayas and it has been found that a lot of prime agriculture land is lost to the process of urbanisation and infrastructure development (Prokop and Sarkar, 2012; Regmi, Saha and Balla, 2014; Rimal 2012). The population of Bhutan is projected to reach 809,397 persons by 2020 and it is expected to force significant changes in the land use and land cover (LULC) of the country. Bhutan is primarily a self-subsistent agricultural economy, engaging more than 70 percent of the total workforce in this sector alone, but only about 3 percent of the total area of the county is 37 Proceedings of the Conference on ‘Climate Change, Environment and Development in Bhutan’ 2-3 April, 2015, Royal University of Bhutan (RUB), Thimphu, Bhutan Editors: Shahnawaz and Ugyen Thinley Occasional Publication No. 1, September 2015 Centre for Rural Development Studies, College of Natural Resources, Lobesa, Royal University of Bhutan under agricultural uses. The Royal Government of Bhutan has developed a vision document ‘Bhutan 2020: A Vision for Peace, Prosperity and Happiness’ (PC 1999) which adopts “Gross National Happiness as the central development concept based on its four pillars of Equitable and Sustainable Socio-Economic Development, Environmental Conservation, Preservation and Promotion of Culture and Good Governance and their linkages” (NLC, 2010, p 3). On the other side ‘The Constitution of the Kingdom of Bhutan’ states that “a minimum of sixty percent of Bhutan’s total land shall be maintained under forest cover for all time” (TCoTKB, 2008, p. 12) Although, both the above mentioned declarations seem complimentary but may turn out to be conflicting at some point of time if the land for agricultural expansion and/or developmental activities cannot be obtained from other types of LULC and may force deforestation process. These concerns raise the significance of regular monitoring of LULC changes in the country. It is important to keep a balance between the land related needs of the people, urbanisation and developmental activities on one side and the environmental conservations on the other side. Remote sensing and GIS techniques have proved quite useful for such purposes (Lillesand and Kiefer, 2000; Yichun, Zongyao and Mei, 2008). However, any studies related to the assessment of LULC changes in Bhutan is not known to the authors so far. In this paper, change detection in LULC of Bhutan was performed for a period of 13 years, with a gap of 6-7 years. Materials and Method 1. Data acquisition The study is based on the multispectral images of Landsat 5, 7 and 8 satellites (Table 1) acquired from the USGS EarthExplorer (USGS, n. d.) for different points of time. A gap of 6-7 years was desirable for properly detecting the LULC changes in a country like Bhutan where a very large area is covered by forest and the pace of change is quite slow. The images downloaded from the EarthExplorer pertain to the years 2000, 2006 and 2013. Bhutan is covered by 2 images and the revisit time of Landsat is 14 days so it was not possible to find the images with minimal cloud cover on the consecutive passes of the satellite or even within the same month for 2000. The images were selected for the autumn months because the cloud cover is minimal at this time of the year and the small vegetation, e.g. grasses and shrubs are dry and the agricultural fields are fallow, which makes it easier to differentiate between the agricultural fields and the surrounding grassy areas, but also difficult to differentiate between fallow fields form the bare soil areas. Date 28 December 2000 30 September 2000 18 October 2006 9 October 2006 6 November 2013 13 November 2013 Satellite LS7 LS7 LS5 LS5 LS8 LS8 Path and Row P – 137 , R – 41 P – 138 , R – 41 P – 137 , R – 41 P – 138 , R – 41 P – 137 , R – 41 P – 138 , R – 41 Ground Coverage Eastern Half of Bhutan Western Half of Bhutan Eastern Half of Bhutan Western Half of Bhutan Eastern Half of Bhutan Western Half of Bhutan Table 1. Details of the Images Used in the Study 2. Image Processing and Classification The wave lengths of the bands of Landsat 8 are different than the Landsat 5 and 7 satellites (Table 2). The wavelength of Band 1 of Landsat 8 is 0.43-0.45 micro meters and this does not exist in the images of the other two satellites (USGS 2014) so this was excluded from the processing of the images. The six closely matching bands common in all the images were selected i.e. bands 1, 2, 3, 4, 5 and 7 for the images of Landsat 5 and 7; and bands 2, 3, 4, 5, 6, 7 for Landsat 8 images. The selected bands of each image were composited in ESRI Software ArcGIS 38 Proceedings of the Conference on ‘Climate Change, Environment and Development in Bhutan’ 2-3 April, 2015, Royal University of Bhutan (RUB), Thimphu, Bhutan Editors: Shahnawaz and Ugyen Thinley Occasional Publication No. 1, September 2015 Centre for Rural Development Studies, College of Natural Resources, Lobesa, Royal University of Bhutan version 10.1 the two images of the same year were mosaicked to make one complete image covering whole Bhutan. However, an area of about 85 km2 on the south-western boundary of the country falls in the third scene, i.e. path 139 and row 41, but this was left out from the study. The National Boundary of Bhutan was used to extract the required parts from the mosaicked images. Band Coastal Aerosol Blue Green Red Near Infrared (NIR) Cirrus SWIR 1 SWIR 2 Panchromatic Thermal Infrared (TIRS) 1 Thermal Infrared (TIRS) 2 Wave Length in Landsat 8 (µm) Wave Length in Landsat 5 and 7 (µm) 0.43 - 0.45 0.45 - 0.51 0.45-0.52 0.53 - 0.59 0.52-0.60 0.64 - 0.67 0.63-0.69 0.85 - 0.88 0.77-0.90 1.36 - 1.38 1.57 - 1.65 2.11 - 2.29 0.50 - 0.68 1.55-1.75 2.09-2.35 0.52-0.90 10.60 - 11.19 10.40-12.50 11.50 - 12.51 Table 2. The Bands and their Wavelengths in Different Landsat Satellites The extracted images of Bhutan for each of the three years were classified by applying maximum likelihood method of supervised classification technique. Ten classes were identified on each image (Table 3), out of which only seven classes pertained to LULC and the remaining three consisted of noise elements such as clouds, shadows and stripes etc. Since the spatial resolution of Landsat images is approximately 30 meters and it is difficult to clearly differentiate between some classes having similar optical characteristics. Due to this, the high resolution images on ArcGIS online and Google Earth as well as the ‘Bhutan Land Cover Assessment (LCA) 2010’ data generated by the Ministry of Agriculture and Forests (MoAF, 2010) were referred to minimise the errors in defining the training areas for each class. In this way, thirty training areas were identified for each class on each image and these were used for generating the signature files for classifying the images. Class ID Class Name Class Description 1 2 Snow River 3 Lake 4 Vegetation 5 6 7 8 9 10 Agriculture Bare Area Build-up Area Shadow Cloud Others Areas covered by snow Areas covered by flowing water Areas covered by marshy area. water reservoir and water other than flowing river Broad leaf + conifer+ fir+ chirpine+ spruce forest + shrub+ meadow Dry land+ wet land+ orchards Rocky outcrop+ bare soils+ degraded area Settlements+ industrial + commercial+ facilities Shadow Cloud Noise elements other than shadow and clouds Table 3. Image Classification Schema Reclassified ID for Masking 1 2 39 Proceedings of the Conference on ‘Climate Change, Environment and Development in Bhutan’ 2-3 April, 2015, Royal University of Bhutan (RUB), Thimphu, Bhutan Editors: Shahnawaz and Ugyen Thinley 3 4 5 6 7 0 0 0 Occasional Publication No. 1, September 2015 Centre for Rural Development Studies, College of Natural Resources, Lobesa, Royal University of Bhutan It is evident from Table 3 that there were some non-LULC classes. i.e. noise elements, in all the classified images. The IDs of the three such classes, i.e. Shadow (9), Cloud (10) and Others (11), were reclassified to zero and the ‘Bhutan LCA 2010’ dataset was used to mask these areas. The ‘Bhutan LCA 2010’ dataset has been generated from the images having 10 meter spatial resolution captured by the Advanced Land Observing Satellite (ALOS - AVNIR-2) during the winter season from 2006-2009 (MoAF, 2011). The process of preparing ‘Bhutan LCA 2010’ also included extensive ground truthing and other sources of spatial information. Thus, this dataset served as the best source for masking as well as a base for testing if the training samples defined on one dataset can be transferred for classifying another dataset. This procedure was used for accuracy assessment of the classified Landsat images. Before using for masking and accuracy assessment, the ‘Bhutan LCA 2010’ dataset required some processing. It had 28 LULC classes whereas the classification schema used in this study has only seven LULC classes (Table 3). The current classification schema was taken as the base and the relevant classes of ‘Bhutan LCA 2010’ were merged together to match the classes of all the images. The merged dataset of ‘Bhutan LCA 2010’ was resampled to match the resolution of the classified Landsat images of the three years being studies. 3. Accuracy Assessment The accuracy assessment is necessary to validate the results of image classification and several methods have been developed for this process (Banko, 1998; MGL, 2013; Verbyla, 2013). As mentioned above, the merged and resampled dataset of ‘Bhutan LCA 2010’ was used as test ground. The sample size of the test points / pixels was derived based on the thumb rule that these should at least be ten times the number of classes for each class (VGE, 2013). As there are seven LULC classes so the total sample size was computed as 7*10*7 = 490 pixels, and the numbers of pixels for each class were determined by using ratio calculation. All the seven LULC classes were assigned a rank in the ascending order of their area, each rank was divided by the sum of the ranks, i.e. 28, and finally it was multiplied by the total number of pixels, i.e. 490 (Table 4). Classes Snow River Lake Vegetation Agriculture Bare Area Built-up Area Total Ratio 4 3 1 7 6 5 2 Sample size 4/28*490 = 70 3/28*490 = 52.5 (52) 1/28*490 = 18 7/28*490 = 122.5 (122) 6/28*490 = 105 5/28*490 = 87.5 (88) 2/28*490 = 35 490 Table 4. Sample Size of Test Points for Accuracy Assessment Result and Discussion 1. LULC: Area and Change The results of LULC classification show that vegetation occupied 54 percent of the total area in 2000, which was the largest among all the classes (Table 5 and Map 1). The vegetated areas were spread as continuous stretches all over the country except for the northern and western parts. These bare areas account for 20 percent of the total area which have high altitude, cold climate and rocky surface, and all of these factors do not support the growth of vegetation. The 40 Proceedings of the Conference on ‘Climate Change, Environment and Development in Bhutan’ 2-3 April, 2015, Royal University of Bhutan (RUB), Thimphu, Bhutan Editors: Shahnawaz and Ugyen Thinley Occasional Publication No. 1, September 2015 Centre for Rural Development Studies, College of Natural Resources, Lobesa, Royal University of Bhutan agriculture area of 14 percent was distributed in the form of elongated stretches and their shape is self-explanatory that most of these are situated in the flatter valley floors. Some patches of agriculture area were also visible in the northern and western cold-rocky parts, which seems to be a classification error due to similarity in the spectral values of some soil deposits in the higher dry valleys with the fallow agricultural fields. The 4 percent snowy areas are visible along the northern boundary of Bhutan. The proportion of the remaining three classes, i.e. lakes, rivers and built-up area, is 1 percent, 2 percent and 5 percent respectively which is distributed in small patches in different parts of the country and is hardly visible. Class Name Snow Lake River Bare Vegetation Agriculture Built-up TOTAL %Area 2000 4 1 2 20 54 14 5 100 %Area 2006 6 1 2 6 64 15 6 100 Change 2000-06 2 0 0 -14 10 1 1 0 %Area 2013 9 1 3 7 58 8 14 100 Change 2006-13 3 0 1 1 -6 -7 8 0 Change 2000-13 5 0 1 -13 4 -6 9 0 Table 5. Bhutan: Land Use Land Cover - 2000, 2006 and 2013 The vegetation area showed a significant increase of ten percent between 2000 and 2006 (Table 5 and Map 2). There was also an increase of 1 percent in agriculture area, 2 percent in snow area and 1 percent in built-up area during this period. Contrary to this, bare area decreased by 14 percent over the same period. A comparison of Map 1 and Map 2 shows that the bare areas disappeared from the central parts of the country and the vegetation areas extended northward and westward into the bare areas. This seems an effect of the dates of image capturing (Table 1). The images used for 2000 were captured on 30th September and 28th December, and the vegetal cover in the higher altitude areas would have changed drastically over these 3 months. Also the images used for 2006 were captured on 9th and 18th October which falls in between dates of the 2 images of 2000 and there will be certain differences in the vegetal cover. During 2006 and 2013, built-up area shows a significant increase of 8 percent whereas the area under vegetation and agriculture shows a decrease of 6 percent and 7 percent respectively (Table 5 and Map 3). Some of these changes can be attributed to the difference of about 3 weeks in the image capturing dates and some is a real change due to conversion of land from one type to the other. An increase of 3 percent in the snow covered area seems to be the result of early snowfall i.e. in November (Map 3). The overall analysis of LULC during 2000 to 2013 shows that vegetation covered the largest area in all the three years but its proportion fluctuated from 54 percent in 2000 to 64 percent in 2006 and to 58 percent in 2000. The variability in coverage can be attributed to phenological effect of vegetation such as shedding of leaves by deciduous trees during winters. As mentioned previously, one image of 2000 was from December and both the images image for 2013 were from November. Apart from this, some rapid economic developments took place which had entailed increase in infrastructure development in the country (GNHC, 2015). These included mega hydro power projects, power transmission lines, industries, widening of national highway and farm roads to provide better facilities for rural development. All such activities certainly have a bearing on the LULC changes. 41 Proceedings of the Conference on ‘Climate Change, Environment and Development in Bhutan’ 2-3 April, 2015, Royal University of Bhutan (RUB), Thimphu, Bhutan Editors: Shahnawaz and Ugyen Thinley Occasional Publication No. 1, September 2015 Centre for Rural Development Studies, College of Natural Resources, Lobesa, Royal University of Bhutan A significant decrease was found in agriculture area from 14 percent to 8 percent and an increase in built-up area from 5 percent to 14 percent (Table 5). These changes can be attributed to the population growth in the country which was estimated as 677,934 persons in 2000 (CSO, 2000), enumerated as 672,425 persons in 2005 (OCC, 2005) and projected as 733,004 persons in 2013 (NSB, 2013). In particular, the growth of urban areas due to increasing economic opportunities and rural-urban migration had forced the construction of a large number of buildings for serving as residences, offices and business places. Also the expansion of facilities and amenities, infrastructure, roads, drinking water pipelines, and recreational sites is causing reduction in agriculture areas. Such developmental activities have led to significant conversion of agricultural lands in to built-up areas. Also a high decrease in bare areas from 20 percent in 2000 to 7 percent in 2013 was found. The larger coverage of bare areas in 2000 can be attributed to the exposure of rocks with less snow cover during the month of September. Further, images from November and December could have led to mixing of spectral properties between agriculture area and bare area due to non-agriculture season on one side and dryness on the other side. Map 1. Bhutan Land Use Land Cover – 2000 2. LULC: Accuracy Assessment As mentioned in the methodology, an attempt was made to test if the classification validation test areas created on a single and different dataset can be used for validating the classified images of various years. The classification validation test pixels were extracted from ‘Bhutan LCA 2010’ and these were used for assessing the accuracy the 3 LULC datasets of 2000, 2006 and 2013. The results show that the overall accuracy of classification for the dataset of 3 years, i.e. 2000, 2006 and 2013, was 66.32 percent, 66.60 percent and 52 percent respectively (Tables 6, 7 and 8). The overall accuracy for each of the years, especially year 2013, was way below 80 percent which according to Kiefer and Lillesand (2000) is said to be the threshold of good classification result. This can be associated with the fact that the satellite images used for classification were captured on dates and months as the images of good spectral quality of the same months 42 Proceedings of the Conference on ‘Climate Change, Environment and Development in Bhutan’ 2-3 April, 2015, Royal University of Bhutan (RUB), Thimphu, Bhutan Editors: Shahnawaz and Ugyen Thinley Occasional Publication No. 1, September 2015 Centre for Rural Development Studies, College of Natural Resources, Lobesa, Royal University of Bhutan were not available from the USGS EarthExplorer portal. Besides, the images were from non– agriculture months (October, November and December) when the agricultural fields have no crops and it becomes difficult to distinguish agriculture fields from bare soils or also from shrubs sometimes. Map 2. Bhutan Land Use Land Cover – 2006 Map 3. Bhutan Land Use Land Cover - 2013 43 Proceedings of the Conference on ‘Climate Change, Environment and Development in Bhutan’ 2-3 April, 2015, Royal University of Bhutan (RUB), Thimphu, Bhutan Editors: Shahnawaz and Ugyen Thinley Occasional Publication No. 1, September 2015 Centre for Rural Development Studies, College of Natural Resources, Lobesa, Royal University of Bhutan LULC Class Snow River Lake Snow River Lake Vegetation Agriculture Bare areas Built-up areas Total Producer’s accuracy Overall 47 5 0 0 4 10 3 69 68.12 0 13 0 2 8 10 20 53 24.53 0 2 8 2 2 2 2 18 44.44 Vegetation 0 0 0 104 9 3 3 119 87.39 Agriculture 0 1 0 6 79 9 7 102 77.45 Bare Area 4 2 0 4 11 59 8 88 67.05 Built-up Area 0 0 0 0 22 2 11 35 31.43 Total 51 23 8 118 135 95 54 484 User’s accuracy 92.16 56.52 100.00 88.14 58.52 62.11 20.37 66.32 Table 6. Confusion Matrix for LULC - 2000 Classification Snow River Lake Snow River Lake Vegetation Agriculture Bare areas Built-up Total Producer’s accuracy Overall 52 2 0 3 1 9 2 69 75.36 0 10 0 2 8 6 27 53 18.87 0 6 9 0 1 0 2 18 50 Vegetation 0 4 0 90 15 3 8 120 75 Agriculture 0 0 0 7 89 3 3 102 87.25 Bare Area 3 6 0 5 10 54 10 88 61.36 Build-up Area 0 0 0 2 14 0 19 35 54.29 Total 55 28 9 109 138 75 71 485 User’s accuracy 94.55 35.71 100.00 82.57 64.49 72.00 26.76 66.60 Table 7. Confusion Matrix for LULC - 2006 Classification Snow River Lake Snow River Lake Vegetation Agriculture Bare areas Built-up Total Producer’s accuracy Overall 49 1 0 1 0 10 8 69 71.01 0 5 0 5 9 3 31 53 9.43 2 1 14 0 1 0 0 18 77.78 Vegetation 0 3 0 74 9 10 23 119 62.18 Agriculture 0 0 0 9 80 6 7 102 78.43 Bare Area 24 10 1 2 10 12 29 88 13.64 Build-up Area 0 0 0 0 17 0 18 35 51.43 Total 75 20 15 91 126 41 116 484 User’s accuracy 65.33 25.00 93.00 81.32 63.49 29.27 15.52 52.07 Table 8. Confusion Matrix for LULC - 2006 The satellite images captured during different seasons are considered important for classifying agriculture area but such Landsat images of usable quality were not available due to large cloud coverage and haze etc. (Prishchepov et al., 2012). Apart from this, low resolution (30m) of Landsat images with no field verification can result in low accuracy (Yichun, Zongyao and Mei, 2008; Prishchepov et al., 2012). Conclusions and Outlook A very large proportion of the total area of Bhutan has extensive vegetal cover. Although, there were some fluctuation in this area between 2000 and 2013 still it covers 58 percent of the country’s area, which is 4 percent more than that in 2000. The built-up areas are increasing due 44 Proceedings of the Conference on ‘Climate Change, Environment and Development in Bhutan’ 2-3 April, 2015, Royal University of Bhutan (RUB), Thimphu, Bhutan Editors: Shahnawaz and Ugyen Thinley Occasional Publication No. 1, September 2015 Centre for Rural Development Studies, College of Natural Resources, Lobesa, Royal University of Bhutan to urbanisation and developmental processes and these are encroaching up on the areas under vegetation and agriculture. There is no significant change in the water bodies like lakes and drivers but there is a small increase in the area under snow cover. A significant decline in bare areas seems to be an error in the classification caused by the fact that there is significant gap in the dates of capturing the images used in this study. The overall accuracy of the classification varied between 52 percent and 67 percent, which is considered quite poor, and the accuracy of some classes was as low as 20 percent. This happened due to several confounding factors which include dates of the images, coarse resolution of Landsat images as well as testing of a methodology for transferring the validation samples taken from a different dataset than from the classified images to be validated. Remote sensing technology offers a range of advantages over the conventional methods of studying LULC changes. Given the availability of good quality data and application of appropriate methodology, this technology helps in reducing costs and time to a large extent. However, this study confronted several limitations due to which authors resorted to depend on the images of different spatial and temporal resolutions. For example, the images on Google Earth and ArcGIS Online were of varying spatial resolutions depending on the scale of visualisation and for different points of time, and these were referred during the process of identifying LULC classes on Landsat images of 30 meter resolution. In addition, the ‘Bhutan LCA 2010’ was of 10 meter resolution and this was used as a proxy ground reference for validating classification accuracy. This approach was adopted due to sheer lack of time and resources. Also advanced using image processing methods, such as band ratioing for detecting clouds and shadows as well as NDVI computation, can facilitate better discrimination between vegetation and other cover types and help in reducing misclassification or classification errors (Farooq, n.d). The results can be improved tremendously by overcoming the limitations and using advanced methods of image processing and classification. Acknowledgements This study was carried out as part of the project ‘Geospatial Methodology to Assess Climate Change Adaptation Strategies for Traditional Economy in Bhutan’ co-funded by the Commission for Development Research (KEF), Vienna, Austria and coordinated by the Interfaculty Department of Geoinformatics - Z_GIS, University of Salzburg, Austria. The authors are grateful to KEF as well as to Z_GIS for involving the College of Natural Resources (CNR), Royal University of Bhutan (RUB) as a partner in this project and providing ample opportunity to benefit from the faculty development activities. We are also thankful to the Austrian Development Cooperation Coordination Office, Bhutan for co-funding the dissemination conference and to the Centre for Rural Development Studies, CNR, RUB for publishing this paper in the conference proceedings. We highly appreciate Dr. Shahnawaz (Z_GIS) for his support and guidance throughout this research project. References CSO (2000). Statistical Year Book 2000. Central Statistical Organisation, Royal Government of Bhutan, Thimphu, Bhutan. Banko, G. (1998). A Review of Assessing the Accuracy of Classifications of Remotely Sensed Data and of Methods Including Remote Sensing Data in Forest Inventory. <http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.200.7822&rep=rep1&type=pdf>. 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Journal of Plant Ecology 1 (1). pp. 9-23. 46 Proceedings of the Conference on ‘Climate Change, Environment and Development in Bhutan’ 2-3 April, 2015, Royal University of Bhutan (RUB), Thimphu, Bhutan Editors: Shahnawaz and Ugyen Thinley
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