From the book ”The Western Ghats” by Mohan Pai (2005).
THE GROVES WERE GOD’S FIRST TEMPLES
What we are doing to the forests of the world is but a minor reflection of what we are doing to ourselves and to one another.
__ Mahatma Gandhi
Although they receive vast amounts of rain, the evergreen forests of the Western Ghats are not rainforests in the strictest sense. In the tropical rainforests of the Amazon, for example, rain falls steadily and predictably throughout the year. This ensures that the niches which flora and fauna occupy are always available; and this in turn enables an enormous variety of species to survive. So the diversity of the monsoon forests in the Western Ghats cannot be compared with that of the Amazonian jungles.
Moist deciduous forests – Mahadayi Valley
The tropical monsoon forest contains trees of smaller stature than those found in the rainforest. The trees of the monsoon forest have a more open canopy than the rainforest, creating a dense, closed forest at the floor, or what we think of as a tropical jungle beneath. The thick surface undergrowth makes it difficult to navigate through the forest. Jungle growth is also found along streams, and in openings created by humans.
The southern Western Ghats has the best preserved and most extensive climax vegetation in the peninsular India. Some of the tropical moist forests in southern Karnataka, Kerala and Tamil Nadu are among the best representative areas of Indo-Malayan rainforest formations.
Forests – the mother of rivers
There is an umbilical connection between healthy forests and water regimes. Forests are nurseries and cisterns for our life giving rivers. Forest areas in the Western Ghats give birth to all the major and minor rivers of the peninsula. Most of the rivers spring from some unknown forest of the Western Ghats and yet there is a wholesale destruction and wanton pillage of forest areas that give birth to the rivers.
Because of the slope the rain water cannot stay to soak into the earth, it flows downhill rapidly taking some of the earth with it. This run-off on the hillsides will only be halted, and water will percolate into the earth where there is good tree cover. In fact a forest traps rainwater and channels it into underground streams. The fact that so many mountain springs have dried up in recent years is not due to some inexplicable form of bad luck. It is the direct result of the reduction in the number of trees on our hills.
Relationship Between Climate and Vegetation
The climate of the Western Ghats shows two rainfall gradients and a temperature gradient.
The West-East Gradient
The west-east rainfall gradient is determined by the effect of Ghats escarpment. The reliefs of the Ghats act as a barrier to the eastward movement of the cloud masses brought by the summer monsoon rain-bearing winds of the south-west monsoon.
Bisale Ghat, Karnataka – Pic by Mohan Pai
These masses bring prodigious amount of rainfall over the western slopes of the Ghats. For instance in Agumbe (height 645 m) which is situated at the edge of the Ghats, the mean annual rainfall is 7,460 mm, and in some years it exceeds 12,000 mm in only 130 rainy days. Overall the western slopes receive 2,000 to 7,500 mm of rainfall. Once this obstacle is crossed, the rainfall decreases rapidly to <800mm>
Aerial View of Evergreen Forests – Mahadayi Valley
The South-North Gradient
An important feature of the Western Ghats is that they form more or less continuous chain of hills with a latitudinal extent of almost 12 degrees. This has few parallels in the tropical world(eastern part of Madagascar and Queensland in Australia). The monsoon, the very pulse of India, adds yet another dimension : the duration of the dry season gradually increases from two months in the southern parts of the Ghats to over eight months north of Mumbai. This gradient is determined by the arrival and withdrawal of the summer monsoon. The monsoon generally arrives towards the end of May at the southern tip of India, in the first week of June at Tiruvananthpuram, five days later it reaches Karwar, in another five days it has already crossed Mumbai and by middle of June it is beyond Kutch. Thus it takes only 10-15 days to cover the Indian peninsula from 80 N to the Tropic of Cancer.
The monsoon begins to retreat by the end of September in north India but it takes nearly 15 days for the front to withdraw from Kutch to Ratnagiri which it reaches in the beginning of October, in another 15 days it covers 400 km, the distance separating Ratnagiri from Coondapur. The front passes through Mangalore at the beginning of November and Kozikode in a fortnight, and reaches Kanyakumari only in early December. Thus the withdrawal is spread over a period of nearly two and a half months. The advance and specially the gradual withdrawal of the monsoon leads to a reduction in the rainy period from south to north and consequently a concomitant lengthening of dry season.
This gradient is one of the key factors for understanding the variations in the floristic composition along the Ghats. The distribution patterns of the species clearly show that many species cannot thrive under prolong dry periods. Thus several species are not found north of the Shencottah-Ariankavu pass, while others disappear beyond the Palghat Gap. Hence, the number of endemic evergreen species which are generally confined to a moist environment diminishes from south to north in the Western Ghats. In the northern part of the Ghats, this gradient also determines the climatic limits beyond which the evergreen formations gradually give way to deciduous forests. Evergreens survive only under special edaphic conditions or at the higher elevations, where dew and mist provide additional moisture.
The temperature gradient is mostly related to increase in altitudes. The influence of the decreasing temperature with increased altitude is explicit only in those regions of the Ghats where the altitude is sufficiently high i.e. from 700 or 800 m upwards. Generally the mean temperature of the coldest months ranges from 230C at sea level to 110C at 2,400 m. However, it must be noted that for the same elevation, the temperature may differ considerably from one place to another, depending on exposure or slope. This decrease in temperature influences the kinds of changes: a) structural change from tall forests (canopy higher than 30 m) to stunted forest (canopy lower than 20 m or sometime 15 m). b) floristic change as some species are unable to adapt to very low temperatures which are optimal for others.
Uttara Kannada Forests – Pic by Mohan Pai
Climatic Variations and Endemics
The high degree of endemism in the evergreen forests of the Western Ghats can be attributed to the isolation of the Ghats from other moist formations and the prevailing drier climatic conditions in the surrounding areas. This isolation seems to have facilitated the process of speciation (formation of new biological species) leading to the phenomenon of vicariance between sister species derived from a common ancestor, one of which thrives in the evergreen forests of the Ghats and the other in the adjacent dry regions (for example Diospyros assimilis in the moist evergreen forests and D. Ebenum in dry forests).
South of Kodagu, the Western Ghats are comprised largely of high ranging hills with several enclaves which formed ideal refugia for certain species when the climatic conditions became drier . Within the Ghats, the variation in the degree of endemism is mainly determined by
a) the increase in the number of dry months from south to north and
b) the decrease in the temperature with increase in altitude. These two gradients also explain the numerous cases of vicariance encountered within the evergreen continuum. Local topographic variations add another dimension to the floristic diversity and endemism.
Bamboo Brakes – Muthodi, Karnataka – Pic by Mohan Pai
In the Western Ghats, based on the ecological factors and floristic composition, 4 major forests and 23 floristic types have been distinguished. These types are closely related with the temperature and rainfall regimes. Wet evergreen, dry evergreen, moist deciduous and dry deciduous are clearly distinguished by the mean annual rainfall, whereas low, medium and high elevation wet evergreen types are distinguished by the decrease in minimum temperature with increasing altitude. In addition to forests, high altitude grasslands are another unique ecosystem in the Western Ghats.
Wet Evergreen Forests
Wet evergreen forests are mostly confined to the windward side of the Ghats where the rainfall exceeds 2,000 mm.
By taking into account the distribution pattern of certain characteristic species, which reflect the climatic variation, the forests are further subdivided into 15 main floristic types – low (0 – 800 mm), medium (600 – 1,450 mm) and high (> 1,450 mm) elevation types. In the low elevation type, they are tall dense forests with four strata and emergent layer – canopy height often reaches 35 – 45 m.
The deep valleys on the western windward side nurture closed canopy, stratified evergreen forests. These are arranged in a series of tiers. Each tier receives a different amount of light; the tallest trees are bathed in perpetual sunlight, smaller trees and shrubs receive dappled light. The forest floor is almost in complete darkness. The canopy is supposed to be closed because the contiguous crown of tall buttressed trees merge to form a veritable roof.
Occasionally, giant trees termed as emergents push through the canopy to obtain dominant position. Light, temperature and humidity differ at different heights beneath the canopy. Two or more strata of shade loving trees find the appropriate level at which light intensity and relative humidity are best suited for their metabolic activities.
The density of growth in these hot and humid jungles is so great that over 70 tall trees can exist in one hectare. These trees may be 35-45 m high and have evolved small narrow leaves to minimise moisture loss through evaporation. The lower growing plants have larger leaves in order to maximise the benefit of the little light that manages to penetrate. At every level, leaves tend to be narrow with drain-like tips so that the monsoon water flows off efficiently. This makes it possible for the leaf to remain relatively dry and breath.
The forests are in leaf throughout the year and hence termed evergreen. These trees shed their leaves at a slow and steady rate throughout the year, which results in continuous decay and decomposition on the forest floor which is full of leaf litter and decaying wood on which mushrooms, lichen and fungi thrive. In the relative gloom of the forest floor herbs are frequent with good representative of gingers and orchids. Climbers and lianas supported by sturdy trees, spiral towards the canopy in search of better light and fresh air.
Dry Evergreen Forests
The steep eastern slopes of the Ghats where the rainfall is less than 1,500 mm harbour dry vegetation types. However, in the relatively moist valleys and along streams, forests are evergreen and distinct in floristic composition with its counterpart on the western side. Physiognomic structure of these forests varies according to moisture level of the soil. Generally they are short forests, with a canopy seldom higher than 12 m, and with two strata.
Moist Deciduous forests
Moist deciduous forests, which are in primary nature, are found in the rainfall zone of 1,500 mm to 1,800 mm; as a transition between wet evergreen and dry deciduous forests. Large extent of these forests occurs in the Wayanad, Mysore and Karnataka plateau. Moist deciduous forests also occur within the potential area of wet evergreen formations, where the rainfall is more than 2,000 mm. Its very presence in the zone indicates their secondary nature after a possible degradation of original wet evergreen forests. On the leeward rain shadow side as well as on the coastal lowlands there are fairly long dry periods. Moist deciduous trees survive the rigours of the dry months by shedding all their leaves simultaneously to avoid loss of water through transpiration.
During the leafless period the trees carry on their reproductive cycle by spectacular flowering followed by abundant fruiting. With the pre-monsoon showers, a flush of fresh leaves appears to herald the beginning of a fresh annual cycle. A number of good timber trees are found in these open canopy forests.
Dry Deciduous forests
Dry Deciduous forests are confined to the rain shadow areas of the Ghats. Based on the topography of the Ghats, floristic types of dry deciduous formations vary.
Grasslands (The Sholas)
In the Western Ghats natural grasslands are found above 1,800 m in Bababudangiris, Kudremukh, Nilgiris, Anaimalais, Palnis and Cardamom hill ranges. The grasslands which are also called as shrub savannas or the Sholas are characterised by number of herbaceous and shrubby species mixed with grasses.
Kudremukh Sholas – Pic by Mohan Pai
The Shola are subtropical montane evergreen forests that harbour species which have outlasted the gradual climatic and ecological changes since the last glaciation 30,000 to 20,000 years ago. The exact course of evolution of the Sholas which is a mosaic of grasslands with stunted evergreen vegetation in sheltered hill folds is not certain.
One point of view attributes the expansion of grasslands to recurrent fires brought in by the early inhabitants. Using fire they cleared forests and these cleared areas became grasslands. Another point of view attributes the grasslands to climatic conditions in those elevations preventing emergence of closed canopy, multi-tiered vegetation.
Plant communities on reaching grass community level are arrested from proceeding further in succession.
Grasslands then become climatic climax. It is possible that the climax vegetation i.e. montane evergreen forests, did occur elsewhere along the crest line earlier but have been slowly regressing and receding due to climatic changes particularly due to the post Pleistocene dessication and warming. These Pleistocene refugia are mostly restricted to the Western Ghats south of Kodagu and are among the most endangered ecosystems in India.
The grassy meadows of the Sholas are at their best towards the end of south-west monsoon. Thousands of gentians, orchids and violets stud the carpet of grasses with a rapid succession of flowers. The trees are generally stunted and do not form strata. A stream generally runs through these forests. There is a thick layer of humus that holds water and filters it into the limpid streams. The stream waters the forest and the forest protects the streams.
Seaside Vegetation & Mangroves
The marshy areas, the swampy places where the sea comes in high tide, or where a river finally empties itself into the ocean, these are the places where many kinds of fish come to spawn. Often these areas are very large; trees do not grow here, for salt water washes over them, or floods them regularly; the loose muddy sand shifts easily, and the only plants which can take hold are mangroves with their long spreading roots. The mangrove bushes prove their worth during a storm, for they break its force; in a rough sea the mangrove belt acts as a buffer and prevents erosion and keeps the coastline in tact.
The mangrove vegetation has to survive on the scorching, shifting and saline sands. Trailing stems, fleshy leaves, salt excreting glands are some of the aids for their survival.
The mangroves in the slushy estuaries have special features to overcome the difficulties of their habitat. The mangrove trees and shrubs anchor themselves against the push and pull of the tides by stilt roots.
Air in the marshy soil is meagre. The trees often turn their breathing roots upwards in search of fresh air. The seedlings of mangrove trees remain attached to the parent plant until they have a chance of surviving on their own. They fix themselves like darts in the marshy saline slush to avoid being washed away by the sea until they have a chance of surviving on their own.
If we remove the mangroves, the coast is exposed to the danger and damage from storms and rough seas.
A number of factors have been responsible for the depletion of wetland areas, mainly the mangrove forests, along the coasts. Intensive aquacultural development, deforestation, pollution from tankers, domestic waste, agricultural run off and industrial effluents are some of the factors. Most of the surviving mangroves are now confined to West Bengal and the islands in the Bay of Bengal.
Sacred Groves and Sacred Trees
Many traditional societies all over the world revered and worshipped nature and considered certain plants and animals as sacred. India has a long tradition in protecting nature – both plants and animals considered as sacred. Forests have been the lifeline for tribals and other forest dwelling communities since ages. Communities all over India followed the practice of setting aside certain patches of land or forest dedicated to a deity or village God, protected and worshipped.
The forest deities are generally of a primitive nature. Sometimes in the form of unshaped stone lumps smeared with red paint – Kalkai in the Konkan, Kenchamma in South Kanara. They are amongst the fiercest of deities; and breaking even a dead twig in a sacred grove is sure to invite the wrath of the deity. Sacred groves are to be found all over the country and abundantly along the Western Ghats and the west coast and in several parts of Kerala, Karnataka, Tamil Nadu, Maharashtra and Goa.
Sacred groves ranged from 50 hectares or more to a few hundred square meters. Some sacred groves have remained in tact till recent times as in the Dakshina Kannada and Udupi districts of Karnataka. These pockets have contributed to the preservation of tropical biological diversity, for several new species of plants which have disappeared from everywhere else have been found to be preserved in the sacred groves.
Sacred groves in different areas are locally known by different names. In Kerala there are hundreds of small jungles called Sarpakavu. There are the Ayyappan kavus dedicated to Lord Ayyappan, the most famous of which is Sabrimala. In Maharashtra, they are known as Devarai, Devarakavu in Kodagu, Kavu in Kerala and Kan in Uttara Kannada.
In spite of the depletion of forests, some sacred groves still remain in-tact. The sacred groves have contributed to the conservation of nature though in a small measure. There are also sacred ponds attached to temples in many parts of India.
Some of these have been responsible for the protection of certain endangered species of turtles, crocodiles and the rare fresh water sponge.
Many plants are considered sacred from historical times – the peepul tree(ficus religiosa), the banyan tree(ficus bengelenses) and khejadi tree which were traditionally revered and therefore never cut. More than a hundred such species are considered sacred.
These include sandalwood tree, betel nut palm, coconut tree, juniper, champak, lotus and tulsi. This traditional and cultural attitude, though based on religious faith, has made a significant contribution to the protection of various species of trees and plants in India.
Author in the Sahyadris