The Indian Rainforests
Rainforests – the Lungs of the Planet Earth
Tropical rainforests are vital to the global ecosystem and human existence. They are a world like no other and are unparalleled in terms of their biological diversity. Tropical rainforests are a natural reservoir of genetic diversity which offers a rich source of medicinal plants, high-yield foods, and a myriad of other useful forest products. They are an important habitat for migratory animals and sustain as much as 50 percent of the species on Earth, as well as a number of diverse and unique indigenous cultures. Tropical rainforests play an elemental role in regulating global weather in addition to maintaining regular rainfall, while buffering against floods, droughts, and erosion. They store vast quantities of carbon, while producing a significant amount of the world’s oxygen. Rainforests once covered 14% of the earths surface and even though they now only cover 6% of the earth, they are home to almost half of the worlds population of mammals, amphibians, reptiles, insects, bird life and plant life.
Tropical rainforests are located in a band around the equator (Zero degrees latitude) in the area between the Tropic of Cancer (23.5° North latitude) and the Tropic of Capricorn (23.5° South latitude).This 3,000 mile (4800 kilometres) wide band is known as the ‘tropics’.
The equator is a line that circles the centre of our global world and is situated halfway between the north and south poles. Temperatures at the equator are high. These high temperatures cause accelerated evaporation of water, which results in frequent rain in rainforests in the tropics.
Tropical rainforests are found between latitudes 10° N and 10° S. This includes the Amazon Basin of South America, the Zaire Basin of Africa and the islands and peninsulas of South-east Asia.In Southeast Asia, the tropical rainforests are found in India, Bangladesh, Sri Lanka, Malaysia, Brunei, Indonesia, Burma and Papua New Guinea. The rainforests found in India, Bangladesh and Sri Lanka are in small patches and strips, while on the other hand, Indonesia contains one-tenth of the world’s rainforest and 40% of all Asian rainforests! However sadly, as Indonesia is progressing further into modernisation, it is losing its rainforests to commercial logging and human settlements. Malaysia too has lost about two third of its lowland forest to plantations. On a brighter side, Papua New Guinea still has areas of rainforest yet to be disturbed, due to its mountainous terrain. Papua New Guinea is home to many amazing animals, one being the largest butterfly in the world; the Queen Alexandra’s birdwing. Its wing span can reach up to 10 inches wide!
Although they cover less than 2 percent of Earth’s surface, they house an estimated 50 percent of all life on the planet. The immense numbers of creatures that inhabit the tropical rainforests are so great—an estimated 50 million species— they are almost incomprehensible. The sheer range of numbers alone suggests the limited extent of our knowledge of these forests. For example, whereas temperate forests are often dominated by a half dozen tree species or fewer that make up 90 percent of the trees in the forest, a tropical rainforest may have more than 480 tree species in a single hectare (2.5 acres). A single bush in the Amazon may have more species of ants than the entire British Isles. This diversity of rainforests is not a haphazard event, but is the result of a series of unique circumstances.
A tropical rainforest is typically divided into four main layers, each with different plants and animals adapted for life in that particular area: the emergent, canopy, understory, and forest floor layers.
The emergent layer contains a small number of very large trees called emergents, which grow above the general canopy, reaching heights of 45-55 m, although on occasion a few species will grow to 70-80 m tall. They need to be able to withstand the hot temperatures and strong winds in some areas. Eagles, butterflies, bats, and certain monkeys inhabit this layer.
Diagram: Coutesy Animal Corner
The canopy layer contains the majority of the largest trees, typically 30-45 m tall. The densest areas of biodiversity are found in the forest canopy, a more or less continuous cover of foliage formed by adjacent treetops. The canopy, by some estimates, is home to 50 percent of all plant species, suggesting that perhaps half of all life on Earth could be found there. Epiphytic plants attach to trunks and branches, and obtain water and minerals from rain and debris that collects on the supporting plants. The fauna is similar to that found in the emergent layer, but more diverse. A quarter of all insect species are believed to exist in the rainforest canopy. Scientists have long suspected the richness of the canopy as a habitat, but have only recently developed practical methods of exploring it. As long ago as 1917, naturalist William Beebe declared that “another continent of life remains to be discovered, not upon the Earth, but one to two hundred feet above it, extending over thousands of square miles.” True exploration of this habitat only began in the 1980s, when scientists developed methods to reach the canopy, such as firing ropes into the trees using crossbows. Exploration of the canopy is still in its infancy, but other methods include the use of balloons and airships to float above the highest branches and the building of cranes and walkways planted on the forest floor. The science of accessing tropical forest canopy using airships, or similar aerial platforms, is called dendronautics.
The understory layer lies between the canopy and the forest floor. The understory (or understorey) is home to a number of birds, snakes, and lizards, as well as predators such as jaguars, boa constrictors, and leopards. The leaves are much larger at this level. Insect life is also abundant. Many seedlings that will grow to the canopy level are present in the understory. Only about 5 percent of the sunlight shining on the rainforest reaches the understory. This layer can also be called a shrub layer, although the shrub layer may also be considered a separate layer.
The forest floor, the bottom-most layer, receives only 2 percent of sunlight. Only plants adapted to low light can grow in this region. Away from riverbanks, swamps, and clearings
where dense undergrowth is found, the forest floor is relatively clear of vegetation because of the low sunlight penetration. It also contains decaying plant and animal matter, which disappears quickly due to the warm, humid conditions promoting rapid decay. Many forms of fungi grow here which help decay the animal and plant waste. It takes up to 20 minutes for rain to actually touch the ground from the trees. Forest floor – Mahadayi Valley, Karnataka.
Because of the ample solar energy, tropical rainforests are usually warm year round with temperatures from about 72-93F (22-34C), although forests at higher elevations, especially cloud forests, may be significantly cooler. The temperature may fluctuate during the year, but in some equatorial forests the average may vary as little as 0.5F (0.3C) throughout the year. Temperatures are generally moderated by cloud cover and high humidity.
An important characteristic of rainforests is apparent in their name. Rainforests lie in the intertropical convergence zone where intense solar energy produces a convection zone of rising air that loses its moisture through frequent rainstorms. Rainforests are subject to heavy rainfall, at least 80 inches (2,000 mm), and in some areas over 430 inches (10,920 mm) of rain each year. In equatorial regions, rainfall may be year round without apparent “wet” or “dry” seasons, although many forests do have seasonal rains. Even in seasonal forests, the period between rains is usually not long enough for the leaf litter to dry out completely. During the parts of the year when less rain falls, the constant cloud cover is enough to keep the air moist and prevent plants from drying out. Some neotropical rainforests rarely go a month during the year without at least 6″ of rain. The stable climate, with evenly spread rainfall and warmth, allows most rainforest trees to be evergreen—keeping their leaves all year and never dropping all their leaves in any one season. Forests further from the equator, like those of India, Thailand, Sri Lanka, and Central America, where rainy seasons are more pronounced, can only be considered “semi-evergreen” since some species of trees may shed all of their leaves at the beginning of the dry season. Annual rainfall is spread evenly enough to allow heavy growth of broad-leafed evergreen trees, or at least semi-evergreen trees. The moisture of the rainforest from rainfall, constant cloud cover, and transpiration (water loss through leaves), creates intense local humidity. Each canopy tree transpires some 200 gallons (760 liters) of water annually, translating to roughly 20,000 gallons (76,000 L) of water transpired into the atmosphere for every acre of canopy trees. Large rainforests (and their humidity) contribute to the formation of rain clouds, and generate as much as 75 percent of their own rain.
The Amazon rainforest is responsible for creating as much as 50 percent of its own precipitation. Deforestation and climate change may be affecting the water cycle in tropical rainforests. Since the mid-1990s, rainforests around the world have experienced periods of severe drought, including southeast Asia in 1997 and 2005 and the Amazon in 2005. Dry conditions, combined with degradation from logging and agricultural conversion, make forests more vulnerable to wildfire.
Tropical rainforests have some of the largest rivers in the world, like the Amazon, Madeira, Mekong, Brahmaputra, Negro, Orinoco, and Zaire (Congo), because of the tremendous amount of precipitation their watersheds receive. These mega-rivers are fed by countless smaller tributaries, streams, and creeks. For example, the Amazon alone has some 1,100 tributaries, 17 of which are over 1,000 miles long. Although large tropical rivers are fairly uniform in appearance and water composition, their tributaries vary greatly. Many tropical rivers and streams have extreme high and low water levels that occur at different parts of the year. In addition to rivers, rainforests have conventional, free-standing lakes and so-called oxbow lakes, formed when a river changes course. These lakes are home to species adapted to the quiet, stagnant conditions. Tropical waters, whether they be giant rivers, streams, or oxbow lakes, are almost as rich in animal species as the rainforests that surround them. But they, too, are increasingly threatened by human activities, including pollution, siltation resulting from deforestation, hydroelectric projects, and over-harvesting of resident species.
Forest – 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 give birth to all the major and minor rivers. Most of the rivers spring from some unknown forests. 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 a good tree cover. In fact a forest “traps” rainwater and channels it into underground streams.
World’s Largest Pharmacy
Medicinal plants and herbs which are in great demand by Pharmaceutical MNCs e.g. Mappia foetida used for the treatment of ovarian colon cancers. The tree is the richest source of Camptothetician (CPT) used in the treatment of these cancers.
Tropical rainforests are called “the world’s largest pharmacy” because of the large amount of natural medicines discovered in rainforests that are derived from rainforest plants. For example, rain forests contain the basic ingredients of hormonal contraception methods, cocaine, stimulants, and tranquilizing drugs. Curare (a paralyzing drug) and quinine (a malaria cure) are also found there.
CONSEQUENCES OF DEFORESTATION
Rainforests around the world still continue to fall. Does it really make a difference? Why should anyone care if some plants, animals, mushrooms, and microorganisms perish? Rainforests are often hot and humid, difficult to reach, insect-ridden, and have elusive wildlife.
Actually the concern should not be about losing a few plants and animals; mankind stands to lose much more. By destroying the tropical forests, we risk our own quality of life, gamble with the stability of climate and local weather, threaten the existence of other species, and undermine the valuable services provided by biological diversity. While in most areas environmental degradation has yet to reach a crisis level where entire systems are collapsing, it is important to examine some of the effects of existing environmental impoverishment and to forecast some of the potential repercussions of forest loss. Continuing loss of natural systems could make human activities increasingly vulnerable to ecological surprises in the future. The most immediate impact of deforestation occurs at the local level with the loss of ecological services provided by tropical rainforests and related ecosystems. Such habitats afford humans valuable services such as erosion prevention, flood control, water treatment, fisheries protection, and pollination—functions that are particularly important to the world’s poorest people, who rely on natural resources for their everyday survival. Forest loss also reduces the availability of renewable resources like timber, medicinal plants, nuts and fruit, and game. Over the longer term, deforestation of tropical rainforests can have a broader impact, affecting global climate and biodiversity. These changes are more difficult to observe and forecast from local effects, since they take place over a longer time scale and can be difficult to measure.
Deforestation and the Global Carbon Cycle
Carbon dioxide ( CO2) is the major gas involved in the greenhouse effect, which causes global warming. All the things that produce CO2 (like car burning gas) and the things that consume Co2 (growing plants) are involved in the “global carbon cycle”. Tropical forests hold an immense amount of carbon, which joins with oxygen to form CO2. The plants and soil of tropical forests hold 460-575 billion metric tons of carbon worldwide. Each acre of tropical forest stores about 180 metric tons of carbon.
Deforestation increases the amount of CO2 and other trace gases in the atmosphere. When a forest is cut and replaced by cropland and pastures, the carbon that was stored in the tree trunks (wood is about 50% carbon) joins with oxygen and is released into the atmosphere as Co2.The loss of forests has a great effect on the global carbon cycle. From 1850 to 1990, deforestation worldwide (including that in the United States) released 122 billion metric tons of carbon into the atmosphere, with the current rate being 1.6 billion metric tons per year. In comparison all the fossil fuels (coal, oil and gas) burned during a year release about 6 billion tons per year.Releasing CO2 into the atmosphere increases the greenhouse effect, and may raise global temperature. The role of fossil fuels burned by cars and industry is well known, but tropical deforestation releases about 25% of the amount released by fossil fuel burning. Tropical deforestation, therefore, contributes a significant part of the increasing CO2 in the atmosphere.
Today tropical rainforests are disappearing from the face of the globe. Despite growing international concern, rainforests continue to be destroyed at a pace exceeding 80,000 acres (32,000 hectares) per day. World rainforest cover now stands at around 2.5 million square miles (6 million square kilometers), an area about the size of the contiguous 48 United States or Australia and representing around 5 percent of the world’s land surface. Much of this remaining area has been impacted by human activities and no longer retains its full original biodiversity.
The Rainforests of India
The rainforests in India are the centres of species richness and endemism and due to this has the status of being one of the 12 mega-biodiversity countries in the world. Even the two hotspots in India, the Western Ghats and the Eastern Himalayas, owe their status due to the presence of rainforests therein. These forests form very important catchments areas for major river systems, maintain soil and water fertility not only in the immediate vicinity but also hundreds of kilometers away, harbours rich indigenous culture with long traditions of sustainable use of traditional knowledge systems especially on medicines and wild relatives of cultivate crops. It is to these rainforests that more than 80% of the endemic flora and fauna of India are confined. Being the most complex ecosystem, the rain forests are living laboratories in which complex ecological, biological and evolutionary processes that have shaped the Earth.
Bamboo brakes, Muthodi, Karnataka
Tropical forest cover in India has been reduced to two major areas: the coastal hills of the Western Ghats (about 55,000 square miles or 135,000 sq. km) and 14,000 square miles (34,500 sq. km) in Northeastern India. Very little of India’s forest cover is considered pristine. 22.8% —or about 67,701,000 hectares—of India is forested. Change in Forest Cover: Between 1990 and 2000, India gained an average of 361,500 hectares of forest per year. The amounts to an average annual reforestation rate of 0.57%. Between 2000 and 2005, the rate of forest change decreased by 92.3% to 0.04% per annum. In total, between 1990 and 2005, India gained 5.9% of its forest cover, or around 3,762,000 hectares. Measuring the total rate of habitat conversion (defined as change in forest area plus change in woodland area minus net plantation expansion) for the 1990-2005 interval, India gained 1.0% of its forest and woodland habitat.Biodiversity and Protected Areas: India has some 2356 known species of amphibians, birds, mammals and reptiles according to figures from the World Conservation Monitoring Centre. Of these, 18.4% are endemic, meaning they exist in no other country, and 10.8% are threatened. India is home to at least 18664 species of vascular plants, of which 26.8% are endemic. 4.9% of India is protected under IUCN categories I-V.
Rainforests of the Western Ghats
The Western Ghats hill range in India contains spectacular landscapes and an incredible array of wild species, many found nowhere else in the world. One among the world’s 34 most biologically diverse “hotspots”, the region has representation of a wide variety of natural ecosystems from grasslands and dry forests to rainforests, rivers, and streams, threatened by a multitude of human activities such as industrialisation, agriculture, grazing, hunting, deforestation, fragmentation, and degradation. Today, rainforests in the Western Ghats occur largely as fragments within a landscape matrix dominated by commercial plantations of tea, coffee, and other cash crops. With an annual deforestation rate of 1.2%, the southern Western Ghats is losing about 500 square kilometres of forest every year. NCF’s programme focuses on human impacts on wild species and habitats, biological surveys, human-wildlife conflict research and mitigation, and restoration to turn the tide of destruction towards conservation.
Forests of the western slopes of the Western Ghats, Konkan
The northern portion of the range is generally drier than the southern portion, and at lower elevations makes up the North Western Ghats moist deciduous forests ecoregion, with mostly deciduous forests made up predominantly of teak. Above 1,000 meters elevation are the cooler and wetter North Western Ghats montane rain forests, whose evergreen forests are characterized by trees of family Lauraceae.The evergreen Wayanad forests of Kerala mark the transition zone between the northern and southern ecoregions of the Western Ghats. The southern ecoregions are generally wetter and more species-rich. At lower elevations are the South Western Ghats moist deciduous forests, with Cullenia the characteristic tree genus, accompanied by teak, dipterocarps, and other trees. The moist forests transition to the drier South Deccan Plateau dry deciduous forests, which lie in its rain shadow to the east.
Above 1,000 meters are the South Western Ghats montane rain forests, also cooler and wetter than the surrounding lowland forests, and dominated by evergreen trees, although some montane grasslands and stunted forests can be found at the highest elevations. The South Western Ghats montane rain forests are the most species-rich ecoregion in peninsular India; eighty percent of the flowering plant species of the entire Western Ghats range are found in this ecoregion.
The animal life of the Indian peninsular region is characterised by the absence of many of the Indo-Malay species which are so abundant in the hill forests of the Himalayas. It is the home of the true Indian fauna of which the spotted deer, the nilgai, the blackbuck, the four-horned antelope, and the sloth bear are typical representatives. They are found no where else. Other species like the gaur, the sambar and the muntjac (barking deer) occur both in India and Malay countries. The Western Ghats, in sharp contrast to the adjoining dry zone of the Deccan present a region of great humidity and heavy rainfall. The forests covering the western slopes are at times very dense and composed of lofty trees, festooned with perennial creepers. Bamboos form a luxuriant undergrowth. In parts of the range the forests are more open and the banks of clear streams running through them are covered with spice and betel groves.
The Nilgiris, an offshoot of the Western Ghats, rise precipitously to form extensive grassy downs and tablelands seamed with densely forested gorges or Sholas. They are composed of evergreen trees with dense undergrowth.
Among the species limited to these forests are the Nilgiri langur, the Lion-tailed macaque, the Nilgiri brown mongoose and the striped necked mongoose, the Malabar civet, and the spiny mouse. In the higher levels of the Nilgiris and the Anaimalais are found such characteristically Himalayan animals as the tahr, the pine marten and the European otter.
The mammalian fauna of the Western Ghats is dominated by insectivores (11 species), bats (41 species) and rodents (27 species including porcupine). Few studies have, however, paid attention to the community structure and organisation of these small mammals in the Western Ghats, although there have been attempts to review our understanding of the status and ecology of smaller cats and lesser carnivores.
The Northeast India lying between 22-30 degree N latitude and 89-97 degree E longitude, and sprawling over 2,62,379 sq.km., Northeast India represents the transition zone between the Indian, Indo-Malayan and Indo-Chinese biogeographic regions and a meeting place of the Himalayan Mountains and Peninsular India. It was the part of the northward migrating ‘Deccan Peninsula’ that first touched the Asian landmass after the break up of Gondwanaland in the early Tertiary Period. Northeast India is thus the geographical ‘gateway’ for much of India’s flora and fauna, and as a consequence, the region is one of the richest in biological values. It is in this lowland-highland transition zone that the highest diversity of biomes or ecological communities can be found, and species diversities within these communities are also extremely high.
Northeast India is blessed with a wide range of physiography and ecoclimatic conditions. The State of Assam has extensive flood plains, while Khangchendzonga in Sikkim stands 8586 m. tall. Cherrapunjee in the State of Meghalaya holds the record for the highest rainfall in a single month (9,300 mm) as well as the most in a year (26,461 mm) in India, while the nearby Mawsynram has the world’s highest average rainfall (11,873 mm). The forests in the region are extremely diverse in structure and composition and combine tropical and temperate forest types, alpine meadows and cold deserts. There are regions, for example, in the State of Sikkim, where the faunal assemblages also change rapidly from tropical to subtropical, temperate, alpine and finally to cold desert forms.
After the Andaman and Nicobar Islands and the Western Ghats, Northeast India forms the main region of tropical forests in India, especially the species-rich tropical rain forests. The tropical semi-evergreen and moist deciduous forests in the lowlands of this region extend south and west into the subcontinent, and east into Southern China and Southeast Asia. The subtropical forests of the region follow the foothills of the Himalaya to the west; also extend into Southeast China in the east. Himalayan temperate and subalpine zone forests extend from northern Pakistan and adjacent Afghanistan through Northeast India to Southwest China. Each of the eight States of the region, namely Arunachal Pradesh, Assam, Meghalaya, Manipur, Mizoram, Nagaland, Sikkim and Tripura, boast of several endemics in flora as well as fauna. This region represents an important part of the Indo-Myanmar biodiversity hotspot.