1. Introduction
Mountains are among the most fragile environments on Earth. Many mountain ecosystems, including the Himalayan mountains, which are among the most unstable and fragile mountain areas in the world, are strongly affected by drivers of global change such as land use changes and climate change [
1,
2,
3,
4,
5,
6]. Environmental degradation such as deforestation and degradation of the Himalayan forests are major environmental issues of global significance and some of the most intensively studied land use change processes [
1,
7,
8]. Despite the fact that the Indian Himalayas are recognized global biodiversity hotspots, forest cover is under pressure from extensive and rapid land cover change due to anthropogenic and natural drivers [
9,
10]. At the same time, the Himalayan region is vulnerable to numerous types of hazards such as landslides, extreme rainfall events, floods, and forest fires, which further deteriorate the mountain landscape and forest ecosystem [
11,
12,
13].
Forest loss and fragmentation are distinct but related phenomena. Forest loss is simply the conversion of forestland to some other land use, but forest fragmentation occurs when a large region of forest is broken down, or fragmented, into a collection of smaller patches of forest habitat [
14,
15]. Forest landscapes are at high risk of forest fragmentation because of changes in land cover due to processes such as agricultural intensification, logging, and infrastructure development. These changes have led not only to the loss of habitat and biodiversity, but also to the modification of natural landscapes and ecosystem functions [
16,
17,
18,
19,
20,
21]. The anthropogenic drivers and their impact on natural resources, biodiversity, habitat loss, and fragmentation of the forest are widely documented across the Hindu Kush Himalaya region [
22,
23,
24,
25,
26,
27,
28], although non-anthropogenic drivers such as natural hazards also contribute to forest fragmentation, especially in mountain regions such as the Himalayas [
29]. However, very few studies have been conducted to understand the correlation between natural hazards and forest fragmentation. Therefore, understanding the link between natural hazards and forest fragmentation at different scales is also important for implementing conservation strategies for proper land management in mountain regions such as the Himalayas.
The Garhwal Himalaya is one of the hotspots of biodiversity situated in the western part of the Uttarakhand Himalaya [
30]. Extensive deforestation and fragmentation of the forests in the Garhwal Himalaya have caused serious environmental degradation [
1,
31,
32], which is a critical issue in the Uttarakhand Himalaya and a basic reason for biodiversity loss [
32]. According to data from the Ministry of Environment and Forests (MoEF), 44,868 hectares of forest land have been changed to non-forest use in Uttarakhand since 1980, 9500 hectares of which have been converted for the construction of roads, followed by 5500 hectares for hydro-projects and 3100 hectares for transmission lines. Agriculture is the main occupation of the people of the Garhwal Himalaya. About 70% of the population is directly and indirectly employed in the agriculture sector [
33], which may lead to the overexploitation of natural resources in the region. Not surprisingly, the fragile nature of the Garhwal Himalaya coupled with increasing human activity poses a serious threat to the natural landscape, especially in the forest ecosystem. Therefore, forest cover has been under pressure over the last few decades in the region.
The present study focuses on the Rudraprayag district of the Uttarakhand state, situated in the Garhwal Himalaya region of India (
Figure 1). The Rudraprayag district has been continuously experiencing extensive forest loss, due to agriculture expansion and infrastructure development. The forest in this area has been converted for hydroelectric projects (62.93 hectares), roads (187.52 hectares), or other activities (299.08 hectares) [
34]. On the other hand, natural hazards such as floods, landslides, and forest fires have increased over the last few decades and have led to further deterioration of the forest landscape in the study area [
10]. For example, a vegetation cover mapping was done at the National Remote Sensing Centre (NRSC) for the flood affected area of the Mandakini river between Kedarnath to Rudraprayag during the 16th and 17th of June 2013. The assessment shows that the vegetation cover had changed at 50 locations. The loss of forest cover was 46 hectares and the loss of grassland cover was 124.9 hectares in the Rudraprayag district. Recently, in 2016, a study was conducted by the Forest Department of Uttarakhand, which was related to the forest fire in Uttarakhand. According to the report, 79 locations experienced forest fires in the forest area, and the loss of forest cover was 157.20 hectares in the forest fire incident in the Rudraprayag district between April and May 2016. These are some examples that have indicated the anthropogenic pressure on natural resources and the natural vulnerability of this region.
The Rudraprayag district has experienced the extensive loss of forest in the past due to human activities and natural hazards, but data and documentation detailing this are limited. The present study is designed to fill this gap and to provide detailed information about land cover change and forest fragmentation in the study area. Satellite remote sensing and the use of geographical information systems (GIS) have emerged as powerful tools to create a spatial inventory of natural resources and play crucial roles in monitoring and analysing spatial and dynamic changes of an area [
35]. Therefore, this study applies satellite remote sensing: (1) to analyse the spatial-temporal trends in land-use/cover change from 1976 to 2014 and (2) to evaluate forest fragmentation due to the land cover change.
3. Results
3.1. Land Cover Maps and Status
The land cover maps for the years 1976, 1998, and 2014 based on Landsat 2 (MSS), Landsat 5 (TM), and Landsat 8 (OLI) satellite data were prepared with nine land-cover types, namely, dense forest, open forest, pasture land, snow and glacier, barren land, scrub land, agriculture land, water bodies, and built-up area.
Figure 3 shows the final output of the supervised classification, which consists of three classified maps of the Rudraprayag district, for 1976, 1998, and 2014 and a comparison in terms of the total area for each land cover category.
3.2. Accuracy Assessment
Table 3 shows the error matrix with the user’s accuracy, producer’s accuracy, and kappa coefficient. The overall accuracy was calculated from the error matrix (
Table 3) by dividing the correctly classified pixel by the total number of the pixels, i.e., (240/267) × 100 = 89.88%. Therefore, the total accuracy was 89.88% for the 2014 classified map. Furthermore, the Kappa coefficient was calculated for the 2014 classified map at 0.8818 (88.18%).
3.3. Land-Use and Land-Cover (LULC) Change
Table 4 summarizes the results of the land cover, change rate, and annual rate of change in area of each class for the Rudraprayag district. Forest area (dense forest and open forest) was the main land cover in 1976 with 74.42% of the total area of the Rudraprayag district, followed by pasture land (11.78%), barren land (4.00%), agriculture land (3.78%), and scrub land (1.89%). The area of dense forest decreased from 55.24% (1069.51 km
2) in 1976 to 44.18% (855.39 km
2) in 2014. On the other hand, open forest increased from 19.18% (371.3 km
2) in 1976 to 23.82% (461.08 km
2) in 2014. The area of pasture decreased from 11.78% (227.98 km
2) in 1976 to 9.91% (191.78 km
2) in 2014. Agriculture and built-up areas progressively increased from 3.78% and 0.14% in 1976 to 8.02% and 0.62% in 2014, respectively. Barren and scrub land areas also progressively increased from 4.0% and 1.89% in 1976 to 6.37% and 4.12% in 2014, respectively. Due to climatic or seasonal variation, the areas under snow and glacier and water bodies decreased from 3.38% (65.5 km
2) and 0.61% (11.86 km
2) in 1976 to 2.51% (48.61 km
2) and 0.46% (8.94 km
2) in 2014, respectively.
The overall annual rate of change in the declining phase of forest cover (dense and open forest) was observed at about 0.22% and 0.27% during the 1st period (1976–1998) and 2nd period (1998–2014), respectively. Another declining annual rate of change was observed for pasture land and snow and glacier during the 1st period (1976–1998), while water bodies and snow and glacier were observed to be in decline during the 2nd period (1998–2014). Other land cover classes experienced an expansion at both time intervals.
3.4. Land-Use and Land-Cover (LULC) Change Trajectories
Table 5 and
Table 6 show the conversion of the land cover in the form of a change matrix for the 1st period (1976–1998) and 2nd period (1998–2014). In the 1st period (1976–1998), there was a major conversion from forest cover (dense and open forest) to agriculture land (44.79 km
2), from forest to scrub land (25.33 km
2), from forest to barren land (5.86 km
2), and from forest to built-up area (2.18 km
2). In the same period, a change from snow and glacier to barren land, from pasture to agriculture land, and from barren land to snow and glacier were also observed. On the other hand, the 2nd period (1998–2014) showed a further major loss of forest cover (dense and open forest), being converted to agriculture land (39.8 km
2), scrub land (29.95 km
2), built-up area (4.13 km
2), barren land (3.51 km
2), and pasture land (5.13 km
2). During the same time period, another major change from snow and glacier to barren land was also observed. A few areas were converted to forest in the study area during both periods.
3.5. Gain and Loss of Land-Use and Land-Cover (LULC)
The net change in the form of gains and losses for each class during the 1st period (1976–1998) and the 2nd period (1998–2014) is shown in
Figure 4. The highest loss was in the dense forest (121.55 km
2) during the 1st period, followed by pasture land (47.88 km
2), and water bodies (1.94 km
2), while a significant gain was observed in agriculture land (54.29 km
2), open forest (54.23 km
2), snow and glacier (25.59 km
2), scrub land (20.77 km
2), barren land (12.21 km
2), built-up area (3.75 km
2), and water bodies (1.41 km
2). An overall loss of 67.32 km
2 of forest area (dense and open forest) was observed during the 1st period. On the other hand, the highest loss was observed in dense forest (92.57 km
2) and snow and glacier (42.48 km
2), while significant gains were observed in open forest (35.55 km
2), barren land (33.75 km
2), agriculture land (27.83 km
2), scrub land (22.39 km
2), pasture land (11.68 km
2), and built-up area (5.37 km
2) during the 2nd period. An overall loss of 57.03 km
2 of forest area (dense and open forest) was observed during the 2nd period. However, the overall net change was the highest during the 1st period.
3.6. Forest Fragmentation Pattern and Status
The forest fragmentation pattern maps for the years 1976, 1998, and 2014 based on forest and non-forest areas were generated by using LFT v2.0. Forest fragmentation maps with categories such as patch, edge, perforated, small core, medium core, and large core are shown in
Figure 5.
3.7. Forest Fragmentation Change
Table 7 summarizes the forest fragmentation change from 1976 to 2014. Forest fragmentation analysis shows a significant decrease in the compact forest area (large core forest) from 1976 to 2014. In 1976, the large core forest was dominant covering 62.01% of the total study area, followed by edge forest (5.28%), perforated forest (5.08%), small core (1.03%), patch forest (0.90%), and medium core (0.12%). Between 1998 and 2014, the large core forest decreased, while medium core, small core, edge, and patch forest continuously increased.
The area of large core forest decreased from 62.01% in 1976 to 32.57% in 2014, showing a component change of 9.95% and 19.49% in the 1st period (1976–1998) and the 2nd period (1998–2014), respectively. The area under patch, edge, perforated, and medium core forest progressively increased from 0.90%, 5.28%, 5.08%, and 0.12% in 1976 to 2.07%, 10.45%, 19.02%, and 0.61% in 2014, respectively, showing a component change of 0.34%, 1.32%, 4.97%, and 0.10 % in the 1st period and 0.83%, 4.01%, 8.96%, and 0.38% in the 2nd period, respectively. Small core forest slightly decreased by 1.02% in 1998, and then drastically increased by 3.28% in 2014, showing a decreased change of 0.01% in the 1st period and an increased change of 2.25% in the 2nd period. An overall decrease in forest area from 3.47% in the 1st period to 2.94% in the 2nd period was observed, while an overall increase in non-forest area from 3.47% in the 1st period to 2.94% in the 2nd period was observed.
A declining annual rate of change for large core forest was observed at about 0.79% and 2.93% in the 1st period (1976–1998) and the 2nd period (1998–2014), respectively. Other increasing annual rates of change were observed in patch, edge, perforated, and medium core forests in the 1st period and the 2nd period, although small core forest decreased in the 1st period, and then increased again in the 2nd period. A declining overall annual rate of change for the total forest cover was observed at 0.22% and 0.27% for the 1st period and the 2nd period, respectively. As a result, the overall annual rate of change in non-forest increased from 0.58% in the 1st period to 0.60% in the 2nd period.
5. Conclusions
This study assessed changes in land-use/land-cover and forest fragmentation in the Rudraprayag district, Garhwal Himalaya, India. The study area experienced a decrease in forest cover and an increase in agricultural land, barren land, scrub land, and built-up area between 1976 and 2014. Forest cover is likely to decrease further due to commercial exploitation, expansion of agricultural land, and human settlements. The results of the forest fragmentation analysis showed that the increase in the non-forest and perforated areas is the main cause of the decline of the large core forest. The study indicates that expansion in agriculture and the built-up area are the major drivers of forest cover change and fragmentation. The study results also suggested that forest fragmentation coupled with land cover changes may lead to forest degradation with implications for biodiversity, habitat ecosystem services, and people’s livelihoods.
This study contributes to the understanding of the pattern of forest fragmentation and influence on the forest fragmentation pattern caused by land cover changes. Finding the areas where changes have occurred will help to fill the gap necessary to lead to prioritization in forest management, conservation, and biodiversity policies. This study will also fill an information gap regarding area classification, which has been heretofore poorly researched with poor data availability and will improve information at the regional and national level. Moreover, improved understanding of the drivers can help reveal the dynamics of LULC change and the forest fragmentation process of the Himalaya region at different scales.