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When you study the composition of living organisms, carbon constitutes 49% of dry weight of organisms and is next only to water. If we look at the total quantity of global carbon, we find that 71 per cent carbon is found dissolved in oceans. This oceanic reservoir regulates the amount of carbon dioxide in the atmosphere. Do you know that the atmosphere only contains about 1% of total global carbon?  Fossil fuel also represent a reservoir of carbon. Carbon cycling occurs through atmosphere, ocean and through living and dead organisms. According to one estimate 4 × 1013 kg of carbon is fixed annually in the biosphere through photosynthesis.  A considerable amount of carbon returns to the atmosphere as CO2 through respiratory activities of the producers and consumers.  Decomposers also contribute substantially to CO2 pool by their processing of waste materials and dead organic matter of land or oceans. Some amount of the fixed carbon is lost to sediments and removed from ci...

When we conserve and protect the whole ecosystem, its biodiversity at all levels is protected - we save the entire forest to save the tiger. This approach is called in situ (on site) conservation .  In situ conservation – Faced with the conflict between development and conservation, many nations find it unrealistic and economically not feasible to conserve all their biological wealth. Invariably, the number of species waiting to be saved from extinction far exceeds the conservation resources available.  On a global basis, this problem has been addressed by eminent conservationists. They identified for maximum protection certain ‘biodiversity hotspots’ regions with very high levels of species richness and high degree of endemism (that is, species confined to that region and not found anywhere else).  Initially 25 biodiversity hotspots were identified but subsequently nine more have been added to the list, bringing the total number of biodiversity hotspots in the world to 3...

There are many reasons, some obvious and others not so obvious, but all equally important. They can be grouped into three categories: narrowly utilitarian, broadly utilitarian, and ethical.   1. The narrowly utilitarian arguments for conserving biodiversity are obvious; humans derive countless direct economic benefits from naturefood (cereals, pulses, fruits), firewood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes ) and products of medicinal importance. More than 25 % of the drugs currently sold in the market worldwide are derived from plants and 25,000 species of plants contribute to the traditional medicines used by native peoples around the world. Nobody knows how many more medicinally useful plants there are in tropical rain forests waiting to be explored. With increasing resources put into ‘bioprospecting’ (exploring molecular, genetic and species-level diversity for products of economic importance), nations endowed with rich ...

Biodiversity is the term popularised by the sociobiologist Edward Wilson to describe the combined diversity at all the levels of biological organisation.  The most important of them are–  (i) Genetic diversity: A single species might show high diversity at the genetic level over its distributional range. The genetic variation shown by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges might be in terms of the potency and concentration of the active chemical (reserpine) that the plant produces. India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango.  (ii) Species diversity: The diversity at the species level, for example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.  (iii) Ecological diversity: At the ecosystem level, India, for instance, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosyste...

Deforestation is the conversion of forested areas to non-forested ones. According to an estimate, almost 40 per cent forests have been lost in the tropics, compared to only 1 per cent in the temperate region. The present scenario of deforestation is particularly grim in India.  At the beginning of the twentieth century, forests covered about 30 per cent of the land of India. By the end of the century, it shrunk to 21.54 per cent, whereas the National Forest Policy (1988) of India has recommended 33 per cent forest cover for the plains and 67 per cent for the hills.  How does deforestation occur? A number of human activities contribute to it. One of the major reasons is the conversion of forest to agricultural land so as to feed the growing human population. Trees are axed for timber, firewood, cattle ranching and for several other purposes.  Slash and burn agriculture, commonly called as Jhum cultivation in the north-eastern states of India, has also contributed to d...

The degradation of natural resources can occur, not just by the action of pollutants but also by improper resource utilisation practices.  Soil erosion and desertification: The development of the fertile top-soil takes centuries. But, it can be removed very easily due to human activities like over-cultivation, unrestricted grazing, deforestation and poor irrigation practices, resulting in arid patches of land. When large barren patches extend and meet over time, a desert is created. Internationally, it has been recognised that desertification is a major problem nowadays, particularly due to increased urbanisation.  Waterlogging and soil salinity: Irrigation without proper drainage of water leads to waterlogging in the soil. Besides affecting the crops, waterlogging draws salt to the surface of the soil. The salt then is deposited as a thin crust on the land surface or starts collecting at the roots of the plants. This increased salt content is inimical to the growth of crops...

Ozone is found in the upper part of the atmosphere called the stratosphere, and it acts as a shield absorbing ultraviolet radiation from the sun. UV rays are highly injurious to living organisms since DNA and proteins of living organisms preferentially absorb UV rays, and its high energy breaks the chemical bonds within these molecules.  The thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units (DU). Ozone gas is continuously formed by the action of UV rays on molecular oxygen, and also degraded into molecular oxygen in the stratosphere. There should be a balance between production and degradation of ozone in the stratosphere. Of late, the balance has been disrupted due to enhancement of ozone degradation by chlorofluorocarbons (CFCs). CFCs find wide use as refrigerants. CFCs discharged in the lower part of atmosphere move upward and reach stratosphere.  In stratosphere, UV rays act on them releasing Cl atom...

Initially, nuclear energy was hailed as a non-polluting way for generating electricity. Later on, it was realized that the use of nuclear energy has two very serious inherent problems. The first is accidental leakage, as occurred in the Three Mile Island and Chernobyl incidents and the second is safe disposal of radioactive wastes.  Radiation, that is given off by nuclear waste is extremely damaging to organisms, because it causes mutations at a very high rate. At high doses, nuclear radiation is lethal but at lower doses, it creates various disorders, the most frequent of all being cancer. Therefore, nuclear waste is an extremely potent pollutant and has to be dealt with utmost caution.  It has been recommended that storage of nuclear waste, after sufficient pre-treatment, should be done in suitably shielded containers buried within the rocks, about 500 m deep below the earth’s surface. However, this method of disposal is meeting stiff opposition from the public.

Mantle plume is an up-welling of abnormally hot rock within the earth’s mantle which carries heat upward in narrow, rising columns, driven by heat exchange across the core-mantle boundary. Eventually, the rising column of hot rock reaches the base of the lithosphere, where it spreads out, forming a mushroom-shaped cap to the plume.  Geophysicist, W. Jason Morgan, developed the hypothesis of mantle plumes in 1971. The largest (and most persistent) mantle plumes are presumed to form where a large volume of mantle rock is heated at the core-mantle boundary, about 1800 miles below the surface, although smaller plumes may originate elsewhere within the mantle. Heat transferred from the plume raises the temperature in the lower lithosphere to above melting point, and forms magma chambers that feed volcanoes at the surface.  Role of Mantle Plume in Plate Tectonics :  •Mantle plumes transport primordial mantle material from below the zone of active convection; produce time-p...

“Prevention is better than cure” is the motto of disaster management strategists around the world. The first step i.e. disaster preparedness embodies half of the disaster management planning process. Better preparedness against disaster checks the excess loss of life and property and thus, saves the revenues of the government to a greater extent.  Hazard Zone Mapping is an efficient measure to check disaster loss to a greater extent by micro-management of the different disaster-prone zones. It considers a particular disaster, such as earthquake and map it according to its severity and impact in different areas.  Landslide hazard zone mapping and its use in disaster management process.  • Landslide hazard zone mapping at regional level of a large area provides a broad trend of potential landslide zones. A macro level landslide hazard zone for a small area may provide a better insight into the landslide hazards.  • The hazard zone map produced by using techniques, such...

Dead zones are low-oxygen, or hypoxic, areas in the world’s oceans and lakes. Because most organisms need oxygen to live, few organisms can survive in hypoxic conditions. That is way these areas are called dead zones. Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. One of the largest dead zones forms in the Gulf of Mexico every spring. Hypoxic zones can occur naturally but climate change, nutrients run-off from the land, and eutrophication are leading to algal bloom and causing further depletion of oxygen level in water. As a result dead zones are spreading at much faster pace.  Consequences of spreading of Dead Zones on Marine Ecosystem  •The reduced dissolved oxygen in ocean water results in loss of marine life thus the habitats which were once teeming with life are transformed into biological deserts.  •Elevated nutrient levels and algal blooms can also cause problems in drinking water ...

1. Physical Vulnerability may be determined by aspects, such as population density levels, remoteness of a settlement, the site, design and materials used for critical infrastructure and for housing (UNISDR).  Example: Wooden homes are less likely to collapse in an earthquake, but are more vulnerable to fire. 2. Social Vulnerability: Refers to the inability of people, organizations and societies to withstand adverse impacts to hazards due to characteristics inherent in social interactions, institutions and systems of cultural values. It is linked to the level of well-being of individuals, communities and society. It includes aspects related to levels of literacy and education, the existence of peace and security, access to basic human rights, systems of good governance, social equity, positive traditional values, customs and ideological beliefs and overall collective organizational systems (UNISDR). In a disaster, women in general may be affected differently from men because of th...

United Nations Environment Programme (UNEP) has released a report, ‘Sand and Sustainability: Finding new solutions for environmental governance of global sand resources’, that highlights the problem of sand being extracted at rates exceeding natural replenishment rates. Coastal sand mining poses one of the biggest threats to our environment:  •While 85% to 90% of global sand demand is met from quarries, and sand and gravel pits, 10% to 15% extracted from rivers and seashores is a severe concern due to the environmental and social impacts.  •Their extraction often results in river and coastal erosion and threats to freshwater and marine fisheries and aquatic ecosystems, instability of river banks leading to increased flooding, and lowering of groundwater levels.  •The UNEP report notes that China and India head the list of critical hotspots for sand extraction impacts in rivers, lakes and coastlines.  •As per the report, most large rivers of the world have lost betwee...

Its physical characteristics like temperature, salinity, density and the external forces like the sun, the moon and the winds influence the movement of ocean water. Ocean currents are the continuous flow of huge amount of water in a definite direction. Water moves ahead from one place to another place through ocean currents. Ocean currents have direct impact on the climate and economy of the region.  Ocean currents and water masses differ in their impacts on marine life and the coastal environment in different ways:  • Impact on biodiversity:  The physical parameters of water masses are essential because they structure the water masses and determine the various habitats that provide the environmental conditions required for marine life.  These conditions influence the production and the growth of plankton and fish species. The dispersion and dwelling of larvae for many benthic and pelagic species depend on hydro-graphical factors. They also play an important role for...

Mountains are an important source of water, energy and biological diversity. Furthermore, they are a source of key resources such as minerals, forest products and agricultural products and of recreation. As a major ecosystem representing the complex and interrelated ecology of our planet, mountain environments are essential to the survival of the global ecosystem. Mountain ecosystems are, however, rapidly changing.  Developmental initiatives and Tourism in Mountains Adverse Impact:  • Dams and Roads: Dams and roads can be hazardous, if they are not properly constructed and managed. Disasters in mountains, and the forces that trigger them, affect larger areas, sometimes entire watersheds or river systems.  • Mining: The forces that shaped the world’s mountains also made them rich in minerals and metals, including gold, copper, iron, silver and zinc. Owing to increasing demand, mines are now being opened even in remote mountain areas, particularly in developing countries....

Mangrove forests form a unique wetland ecosystem, inhabiting the edge of land and sea, thriving in seawater. Over the past four decades, 35% of global mangrove forests have been destroyed. This degradation of mangrove forests has a knock-on effect on some of the world’s most endangered species which rely on them for habitat, such as the proboscis monkey and the Bengal tiger.  Causes of depletion of mangroves  The natural causes  • Cyclones, typhoons and strong wave action, especially in the geographically vulnerable Andaman and Nicobar Islands;  • Browsing and trampling by wildlife (e.g. deer) and livestock (goats, buffaloes and cows), which are often left to graze freely, especially in the areas close to human habitation;  • Damage by oysters to the young leaves and plumules of Rhizophora and Ceriops plants; crabs, which attack young seedlings, girdle the root collars and eat the fleshy tissues of the propagules  • Insect pests, such as wood borers, caterp...

Destruction of coral reef can be induced by a variety of factors, alone or in combination. However, unprecedented global warming and climate change combined with growing local pressures have resulted in destruction of coral reefs to a large extent.  Impact of global warming on the coral life system:  Coral Bleaching  • The impacts from coral bleaching are becoming global in scale, and are increasing in frequency and intensity.  • Mass coral bleaching generally happen, when temperatures around coral reefs exceed 1 degree Celsius above an area’s historical norm for four or more weeks. Sea surface temperature increases have been strongly associated with El Nino weather patterns. • However, light intensity, (during doldrums, i.e. flat calm conditions), also plays a critical role in triggering the bleaching response. If temperatures climb to more than 20 C for similar or longer periods, coral moralities following bleaching increase.  Rising sea levels  • Observa...