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LAND SURFACE TEMPERATURE RESPONSES TO THE LAND COVER DYNAMICS IN WESTERN GHATS
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T V Ramachandra, Srijith A H and Bharath S
Energy and Wetlands Research Group,
Centre for Ecological Sciences,
Indian Institute of Science - 560012
3. Study Area
The study encompasses high biodiversity hotspot in South Western part of India, known as Western Ghats, extending from 8° to 21° N and 73° to 78° E covering a stretch of 1600 km through the states of Gujarat, Maharashtra, Goa, Karnataka, Kerala and Tamil Nadu. It covers an area 1, 60, 000sq.km. The hill range is interrupted by a 30 km break by the Palakkad (Palghat) Gap of Kerala. These mountain ranges are older than the great Himalayan, which emphasizes their importance. Due to its unique features and resources it is listed by UNESCO as one of the 35 biodiversity hot spots of the world (Meyers et al., 2000). Biodiversity hotspots are the regions that experience an exceptional concentration of plant endemism and experience high rates of habitat loss. The study area is known for high biodiversity, which offer the essential ecosystem services which account for only 3% of the India’s land mass. Around 35% of the global ecosystem services are due to the of biodiversity hotspots, accounting only 2.3 % of Earth’s surface. The study area along with the state boundaries is shown in Fig. 3.1.
This region has been under tremendous pressure due to its declining forest cover at rapid pace which prompted the Govt. of India to list the region under WPA, 1972. The WPA, 1972 was passed to protect animals and plants defining five types of protection viz. National Park, Wild life sanctuary, Conservation reserves, Community reserves and Tiger reserves (WPA, 1972). The region has 16 National Parks, 50 Wild life sanctuary, 2 conservation reserve. Even though conservation measures are adopted, the rate of deforestation has been accelerating in recent years. A report published by ATREE, Bengaluru estimates a loss of 2,729 sq. km. of forest in the Western Ghats during the period 1973-95 with an annual deforestation rate of 1.16%. The loss has been attributed to rise in plantations. Ramachandra et al., 2015 highlight serious LC changes in Western Ghats as forest cover decreased by 2.84%, 4.38% and 5.77% in the Northern, Southern and Central regions of Western Ghats. This has indeed affected the climate of the region with deficit rainfall, rising temperature. If plantations are taking over forest at this rate, then the forests would be destroyed in less than a quarter century (UN FAO, 2008). The rising human interference and building of dams has tremendously affected both flora and fauna of Western Ghats. There are around 1600 dams are built in Western Ghats with Maharashtra topping the list with 631 dams (Latha, 2009). As human and livestock population swell, forests shrink, which shows the relationship between rural communities and forest has become increasingly precarious. Nearly 90% of wood taken by rural communities is used as fuel and the forest is the source of fodder for over 100 million cattle heads of India.
The Ministry of Environment and Forests, Govt. of India, set up a Western Ghats Ecology Expert Panel to study the degradation of Western Ghats and to suggest suitable measures in its protection. The commission headed by Prof. Madhav Gadgil submitted its report on 31 August, 2011 which recommended to declare 64% of the region as Ecologically Sensitive Area (ESA) zones. This sparked in protests against the implementation of the report as it was excessively environment friendly and not in tune with ground realities. Another High Level Working Group (HLWG) headed by Kasturirangan was set up to balance the concern of development and environment protection. This report recommended to declare 37% of area under Ecologically Sensitive Area (ESA) zone which has been accepted but fails in implementation till date.
3.1. Vegetation:
3.1.1. Forest Types:
Western Ghats has 5 major forests and 23 floristic types based on ecological factors and floristic composition (FSI, 2015). They have been distinguished which are closely related to temperature and rainfall regimes. They are:
(i) Tropical Wet Evergreen Forests:
Tropical Wet evergreen forests are mostly confined to windward side of the Western Ghats where the annual rainfall exceeds 2500 mm. These are further divided on basis of elevation into low (0 - 800m), medium (800 – 1450 m) and high (> 1,450m). These are tall trees with canopy reaching a height of 35-45m. The trees are arranged in tiers with each tier receiving different amount of light. The forest floor is in complete darkness. These forests have leaf all through the year and the shedding of leaves occur at a slow and steady rate all through the year. The leaves are pointed and narrow so that monsoon water flows off easily. These forests support lichen, mushroom and fungi that thrive on dead decaying matter. Climbers and lianas supported by sturdy trees, spiral towards canopy in search of light and fresh air (FSI, 2015).
(ii) Tropical semi Evergreen Forests:
The steep eastern slopes of the Ghats where the annual rainfall is less than 1800mm harbour dry vegetation types. Their physiognomic features vary depending on moisture level of soil. Some of the valleys have evergreen forests that are distinct in floristic composition with its counterpart on Western side. These have two strata with canopy reaching a height of 12m from ground (FSI, 2015).
(iii) Tropical Moist Deciduous Forests:
Moist deciduous forests are found in zone where the annual rainfall is in the range of 1600mm to 2000mm. These are a transition between wet evergreen and dry deciduous. Its presence indicates their secondary nature which has been formed after a possible degradation of wet evergreen forests. These are found at lower elevations in the coast and the eastern side which experience fairly long dry periods. These forests shed their leaves to survive the rigours of dry months to avoid loss of water through transpiration. With the pre-monsoon showers, a flush of fresh leaves appears to herald the beginning of fresh annual cycle. These forests have good timber trees (FSI, 2015).
(iv) Tropical Dry Deciduous Forests:
Dry deciduous forests are found in areas where the annual rainfall is in the range of 800mm to 1500mm. These occur in climates that are warm year round and face drought during some months of the year. These are found towards the northern part and eastern side of Western Ghats. These form a canopy cover at a height of 10m. These forests shed the leaves during dry period to prevent loss of water through transpiration (FSI, 2015).
(v) Grasslands:
In Western Ghats, natural grasslands are found above 1800m from MSL in Babudangiris, Kudremukh, Nilgiris, Anaimalai, Palani and Cardamom hill ranges. These are characterized by number of herbaceous and shrubby species mixed with grasses. The grasslands are also called shrub savannah or the sholas that have outlasted the gradual climatic and ecological changes over the last 20,000 years. This vegetation is found in hill folds that are attributed with stunted evergreen vegetation along with shrubby species and they do not form any strata (FSI, 2015).
3.1.2. PLANTATIONS:
The hills of Western Ghats are dominated by different monocultures. Most of these plantations are exotics, which were introduced by the colonial rulers due to their high demand and commercial value. Post-independence the plantations continue to dominate the hilly agro systems. Tea and coffee were the first plantation (17th century) introduced to Western Ghats which are suited to the moist tropical climate for its growth. Teak plantation was first raised as monoculture in Nilambur, Kerala in 1844 and over the period this has attained prominence due to its high timber value. Over the years eucalyptus, bamboo, rubber, clove, acacia, coconut, cardamom, cinchona, Casurina sp. have displaced extensive patches of forest throughout Western Ghats. The hill ranges are also dominated with large number of ornamental plants and horticulture of temperate origin. Some unique landscape such as Myristica swamps were replaced by cultivation of rice, which has led to disappearance of swamp trees (Sathe et. al., 2003).
3.2 SOIL:
The Western Ghats have a wide range of rocks and minerals that has given rise to different kinds of soils. The present system of 11 major soil groups is followed in the classification of soils in the study area (Rajan et al., 2013). The region is dominated with fertile Mollisols followed by Vertisols from southern to northern part. The presence of Ultisols in the Northern end of Western Ghats indicates a change in climate from wet to dry regime (Chandran, 1997). The soil map of the study area is shown in Fig. 3.2.
3.3. RIVERS:
This region forms the catchment of area for complex riverine systems that drain almost the entire South India. The rivers originating in Western Ghats are classified into two major categories: west flowing and east flowing. The west flowing rivers are fast moving owing to the short distance travelled and steeper gradient forming estuaries. The east flowing rivers are slow moving due to the large distance travelled in the plains and eventually join Bay of Bengal forming large deltas. The data on prominent rivers originating from Western Ghats are described in Table 3.1.
3.4. MOUNTAINS:
The ranges of Western Ghats are known by different names at different locations ie. ‘Sahyadris’ in Karnataka and Maharashtra, ‘Sahya Parvatham’ in Kerala and ‘Nilgiri Malai’ in Tamil Nadu. The Western Ghats have some of the highest peaks (Figure 3.3) of the peninsular India with Anaimudi in Kerala scaling 2695m above mean sea level (MSL). The Eastern Ghats and Western Ghats converge at Bilirirangan Hills of Karnataka. The hill range has a number of pass like the Palakkad gap, Tamhini Ghat, Naneghat, Kasara Ghat etc. The northern portion of narrow coastal plain between Western Ghats and Arabian sea is known as Konkan coast, while the central portion is called Kanara and the southern portion is called Malabar. The foothills to the east of Ghats are known as Malenadu in Karnataka while it is Desh in Maharashtra.
3.5 RAINFALL:
The Western Ghats regions are rain fed by the South West monsoon during the months of April to September. The rainfall of Western Ghats show two gradients i.e. the Western and the Eastern. These gradients are due to the differing relief of the Ghats. The relief of Ghats act as barrier to the Eastward movement of cloud masses brought by winds of South West monsoon. These cloud masses ensure an enormous amount of rainfall on the Western slopes of Ghats with an annual average of at least 2000mm. The Eastern slope of Western Ghats faces a drastic change with an annual average falling to 800mm. Table 3.2 describes the annual mean rainfall over two gradients. The annual rainfall of the study area is shown in Fig. 3.4.
3.6 CLIMATE AND TEMPERATURE:
The climate is humid and tropical in the Western side lower reaches due to the proximity to the sea. Elevations higher than 1500 and 2000m (AMSL) have temperate climate and average annual temperature is around 15°C at this elevation but there are drastic changes due to the changing vegetation practices of the region. At lower elevations the mean annual temperature varies from 20°C in South to 24°C in North. Table 3.3 describes the mean temperature over different months of the year in the study area.
3.7 . AGRO – CLIMATIC ZONE OF WESTERN GHATS:
The study has been carried out on the basis of 3 major divisions of Western Ghats: Coast, Hill and Plains carved out of the Agro-climatic zone of India. The Tamil Nadu coast, Malabar coast, Karnataka coast, Konkan coast, Gujarat Region East constitute the coast of Western Ghats. The Maharashtra Sahyadri, Malnad, Tamil Nadu Ghat and South Sahyadri form the hills of Western Ghats. The Maharashtra plateau, Maidan (North&South) and the Coimbatore Madurai uplands constitute the plains of Western Ghats. The agro-climatic zones of Western Ghats are shown in Fig. 3.5.
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