Results and Discussion
In this study, Landsat satellite imageries were used to classify the LULC change in class transition. The classified LULC maps of Islamabad for four decades are presented in Fig.2. In addition, the LULC change in class areas is graphically shown in Fig 3. The achieved overall classification accuracy of LULC maps for the years 1979, 1989, 1999, 2009 and 2019 were 90.5%, 91.13%, 95.32%, 94.44% and 95.1%, respectively. The overall Kappa statistics of the agreement were 0.90, 0.92, 0.94, 0.92 and 0.93 respectively. In the image classification process, the accuracy assessment is an important component. According to Lea and Curtis (2010), the Kappa statistics above 0.9 and overall classification accuracy above 90% indicate a successful classification which succeeded in the present study. The individual LULC class area statistics and rate of change over the various study periods are summarized in Table 3.
The image classification results indicated that the total land area of Islamabad is 906.62 km2. Our results showed that in 1979 approximately 10.7% of the land was covered by build-up land and 14.3% by agriculture and 19.3% by forest and 1.7% by water bodies, adding up to 53.1% of the land area as barren. Whereas, our result indicated that in 2019 approximately 52.4% of the land was covered by build-up land and 19.5% by agriculture and 10.3% by forest and 0.7% by water bodies whereas 17.1% of the land area was covered by barren land. The results revealed that a major expansion with respect to area coverage in Islamabad city was observed in built-up and agriculture land whereas, the forest and barren areas were declined. The assessment of individual class of 1979 and 2019 indicated that there has been a noticeable LULC change during the study period of 4 decades. According to an earlier study (Hassan et al., 2016) that in Islamabad city rapid development has been observed in agriculture, commercial, industrial and urban. This significant trend of LULC use change in urban centers reinforces that increase economic development, population growth, traffic infrastructure, administrative services, topographic and geographic are the major factors of change in land (Mundia and Aniya, 2007; Butt et al., 2015). According to Hassan et al. (2016), the main driving factors of rapid expansion in LULC of Islamabad city is increased in economic activity, population growth and climate change. Rapid development in commercial, industrial, residential and expansion in agriculture land into forest and barren land has been observed in surrounded areas of Islamabad. The barren and the forest area near the population has been cleared for the residential, commercial and agricultural production in order to fulfill the basic necessities of life (Hagler Bailly, 2007).
The results presented in Table 4 and Fig. 2 depict that both negative and positive change followed in the LULC pattern in the Islamabad city of Pakistan. During the period of 1979-2019, the area and amount of change in the build-up and agriculture has account +41.7%, +5.2% added of the total urban sprawl whereas, forest (-9.03%), water bodies (-1.21%) and barren areas (-36.8%) were subtracted in the study area. To understand land expansion in various LULC categories, a change detection matrix (Table 5) was developed which indicate class conversions during the last four decades (1979-2019). The conversion between various LULC categories in different years were studied using cross-tabulation matrix method of Pontius and others (2004).
According to cross tabulation, barren land was converted primarily to build-up and agriculture land. About 417.45 km2 gained by build-up class from barren land as well as from other classes while only 39.87 km2 area converted to other classes. The LULC with respect to build-up land primarily due to rapid population growth and economic development. The area of forest lost about 85.78 km2 while only 21.85 km2 gained from other landscape categories. The rapid expansion of residential, commercial, industrial and infrastructure as well as political driving forces contributing to the decline in forest, vegetation and barren areas (Butt et al., 2015; Hassan et al.,2016). In urban LULC build-up land obtained by changing areas that were previously barren land, agriculture, vegetation, water bodies, which indicate that the existence of high pressure on natural resources to fulfill the growing demand for urban land (Dewan and Yamguchi, 2009). Worldwide anthropogenic activities are responsible for such rapid factor of barren and habitat destruction as well as loss of biodiversity. The rural areas converting into urban land through rapid population growth and development occurring at an unprecedented rate in recent human history and severely degrading functioning of ecosystem services (Lopez, Bocco, Mendoza and Duhau, 2001; Alphan 2003 and Dewan and Yamguchi, 2009).
Water class loss about 10.37 km2 during the last 40 years period. The results indicate that water resources are at decreasing rate. Water source are under stress and such uncertain fluctuations in water bodies may be due to increased urbanization as well as change in climatic patterns. Water bodies are under high stress of high demand of water to Islamabad and Rawalpindi and also for irrigation purposes. Apart from that, water bodies are not only reducing due unban and agriculture demands but also decline due to seepage, percolation and evaporation as well as miss management of water resources (Ashraf et al., 2007; Hagler Bailly, 2007; Keller et al., 2000; Butt et al., 2016). According to IUCN (2005), due to use of herbicides and pesticides in the agriculture land as well as urban waste degrade water quality and quantity (Ahad et al., 2005; Iram et al., 2009). According to IPCC, due to global warming the Earth temperature is rising which lead to change in temperature and precipitation patterns. Consequently, extreme climatic events are occurring such flooding, drought and heat waves. Such changes in climatic patterns can affect water resources and biodiversity (Hassan et al., 2016). In 2015 a severe heat wave struck southern parts of Pakistan and more than 1500 loss their life due to heat stroke in the Karachi city (Chaudhry, 2015).
Generally land dynamic is a complex process and any one approach is unable to describe the pattern of LULC change completely (Verburg and Overmars, 2007).The study indicates that the GIS and remote sensing technique provide an important information about the spatial distribution as well as natural of LULC changes. In our study, we focused only GIS and Remote sensing techniques to examine the LULC change pattern, but could not consider other factors such as climatic, geophysical, socioeconomic, housing factor and land use policy related variables. Therefore future study use policy and other factors along with current study to achieve sustainable urban LULC management.