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Hydrogen sulphide tarnishes silver and blackens leaded house paints

Chapter 3

Impact of Environment Degradation (8L)

  • Biodiversity, Losses and Species Extinction

  • Natural Disasters- Earthquake and Seismicity, Floods, Drought, Tsunamic and Cyclones

Temperature of surface determines the general climate and climate change. However, even during this stable period, regional changes have occurred. As an change in climate that have occurred during this period, it may be noted that about 7000 years ago today’s Sahara Deserts use to receive 20 times more rain fall than it does today.

  1. Write short note on ‘Earth’s Heat Balance.

The radiation which carries energy away from the earth is of a much longer wavelength than the sunlight which brings it to the earth. This is a crucial factor in maintaining the heat balance and one susceptible to upset by man’s activities. The maximum intensity of incoming radiation occurs at 0.5 micros (500 nanometers) in the visible region with essentially none below 0.2 µ or above 3 µ. This encompasses the whole visible region and small parts of the ultraviolet the infrared adjacent to it. Outgoing radiation is in the infrared region with maximum intensity at about 10 and primarily between 20 and 40 µ. Thus the earth loses energy by electromagnetic radiation of much longer wavelength (lower energy) than the radiation by which it receives energy.

The average surface temperature of the earth is maintained at a relatively comfortable 15 ̊ C because water vapor, and to a lesser extent carbon dioxide, reabsorbs much of the outgoing radiation while retaining part of the energy as heat before eventual total loss. If this were not the case the earth’s surface temperature would average around -40C Most of the absorption of infrared radiation is done by water molecules in the atmosphere. Absorption is weak in the regions 7 to 8.5 µ and 11 to 14 µ and nonexistent between 8.5 and 11µ allowing a hole in the infrared adsorption spectrum through which radiation may escape. Carbon dioxide, though presented a much lower concentration than water, absorbs strongly between 12 and 16.3µ and plays a key role in maintaining the heat balance. There is concern that an increase in the carbon dioxide level in the atmosphere could prevent sufficient energy loss to cause a perceptible and damaging increase in the earth’s temperature. This is the well- known, “greenhouse effect” which might result from elevated CO2 levels coming from increased use of fossil fuels.

The earth’s mean temperature rose 0.4 ̊ C from 1880 to 1940 and from 1945 has dropped around 0.1 ̊ C. The initial has been correlated with an increase in atmospheric concentration of CO2. The net result is that the earth’s surface gets heated up by a phenomenon called the ‘Green House Effect’.

  1. What are the factors responsible for increasing CO2 concentration in atmosphere which result in global warming?

Ans. An increased heating of earth would cause recede of glaciers, disappearance of ice caps such as those found over Antarctic and Greenland and rise in ocean level. In fact, it has been estimated that if all the ice on the earth should melt, 200 feet of water would be added to the surface of all oceans, and low-lying postal cities such as Bangkok and Venice would get inundated. Only a rise in sea level of 50 to 100 cm caused by ocean warming would be able to flood low-lying lands, in Bangladesh and West Bengal. Further, due to the much warmer tropical oceans because of increasing carbon- dioxide, there have been likely to be more hurricanes and cyclones and early show melts in mountain causing more floods during monsoons.

If the carbon dioxide content of the atmosphere gets double, the average surface temperature of the earth would rise 6.5 F. However, this would not happen because of reflection of some of the sun’s heat back into the space by densely accumulating particulate contaminants such as smoke and dust from industrial and automobile exhaust. If carbon dioxide continues to accumulate, it may disallow the cooling effect of particulate contaminants, and as a consequence the earth’s temperature may rise again.

Ans. The trend in temperature which has taken place over the last century cannot be associated with the postulated increase in CO2 concentration over the same period. Average northern hemisphere temperatures increased by 0.6 ̊ C between 1890 and 1940 but since that date temperature have decreased by 0 ̊ C. This does not rule out the relationship between CO2 concentrations and temperature but reveals the uncertainty associated with prediction of climatic change and the magnitude of natural effects of unknown cause.

It has been assumed that particulate concentration have been increasing because of man’s activities and that this increase would have an effect of the climatic particles, for instance increase the albedo (percentage of sunlight reflected) by scattering the incoming radiation, and cooling would be predicted as a consequence. Particles also scatter the outgoing radiation, although not so effectively because the particulate sizes that predominate in the atmosphere are most efficient at scattering light of the incoming wavelengths.

  1. What are the effects of particulates on solar radiation and climate?


  1. What type of future climate changes is expected? What will their effect?

Ans. In 1988, the United Nations and the World meteorological Organization established the Intergovernmental Panel on Climate Change (IPC) to study climate change. The IPCC is a network of about 2000 of the world’s leading climate experts from 70 nations.

Greenhouse gases are accumulating in the Earth’s atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperature sand surface ocean temperatures to rise. The changes observed over the last several decades are likely mostly due to human activities. Global warming could have serious societal and ecological impacts by the end of this century.

In May 2000, 63 national academics of science issued a joint statement that said, “The balance of scientific evidence demands effective steps now to avert damaging changes to the Earth’s climate. “At the 1998 World Economic Forum, the CEOs of the world’s 1000 largest corporations voted climate changes as the most critical problem facing humanity.

  1. Oceans help moderate the earth’s average surface temperature in two ways.

    1. They remove about 29% of the excess CO2 we pump into the atmosphere as part of the global carbon cycle.

  2. Aerosols (tiny droplets and soil particles) of various air pollutants are released or formed in the atmosphere by volcanic eruptions and human activities. Some of the resulting clouds have a high albedo and reflect more incoming sunlight back into space during the day. This could help counteract the heating effect of increased greenhouse gases. Nights would be warmer because many of the clouds would still be there and prevent some of the heat stored in the earth’ surface (land and water) during the day from being radiated into space. These pollutants may explain why most of the recent warming in the northern hemisphere occurs at night. However, these interactions are complex. Pollutants in the lower troposphere can either warm or cool the air, depending on the reflectivity of the underlying surface and their ability to limit the size of water droplets.

  3. Some studies suggest that more CO2 in the atmosphere could increase the rate of photosynthesis in areas with adequate amounts of water and other soil nutrients. This would remove more CO2 from the atmosphere and help slow atmospheric warming.

Here is another problem. The elevated levels of CO2 inhibited the uptake of nitrate fertilizer. The decreased uptake of nitrate fertilizer could offset increased plant growth from higher CO2 levels. Perhaps increased rainfall- not increased CO2- accounted for two-thirds of the additional growth of the forests.

  1. What are some possible effect of atmospheric warming?

  1. Changes in the structure and location of wildlife habitats could expand ranges and population of some plant and animal species adapted to warmer climates. However, such changes would threaten plant and animal species that could not migrate rapidly enough to new areas and spices with specialized niches.

  2. Shifts in regional climates would threaten many parks, wildlife reserves, wilderness areas, wetlands and coral reefs-wiping out many current efforts to stem the loss of biodiversity.

Ans. Acid rain causes a number of adverse implications. It tends to increase acidity in the soil, threatens human and aquatic life, destroys, forests and crops reducing agricultural productivity. Besides, it is able to corrode buildings, monuments, statues, bridges, fences and railings.

Significant reductions in fish populations have been observed, accompanied by an associated decrease in the variety of species at all levels in the food chain soils in certain regions similarly are having little buffering capacity and are subject to the leaching of minerals essential to plant growth. There have been soils which have been low in sulphur or high in carbonate. Acidification of soil changes its biology and chemistry. When the soil gets acidified, plant can absorb cadmium more easily and high levels of cadmium in plants have been dangerous for animals for animals and human beings.

  1. Agriculture: Most farm crops are less affected by acid rain than are forests. The deep soils of many farm regions can absorb and neutralize large amounts of acid. Mountain farms are more at risk- the thin soils in these higher elevations cannot neutralize so much acid. Farmers can prevent acid rain damage by monitoring the condition of the soil and, when necessary, adding crushed limestone to the soil to neutralize acid. If excessive amounts of nutrients have been leached out of the soil, farmers can replace them by adding nutrient- rich fertilizer.

  2. Surface waters: Acid rain falls into and drains into streams, lakes, and marshes. Where there is snow cover in winter, local water grow suddenly more acidic when the snow melts in the spring. Most natural waters are close to chemically neutral, neither acidic nor alkaline: there pH is between 6 and 8. The water in some lakes now has a pH value of less than 5 as a result of acid rain. This means they are at least ten times more acidic than they should be. The lakes and ponds are acidic, and many have lost their brook trout and other fish. All of Norway’s major rivers have been damaged by acid rain, severely reducing salmon and trout populations.

  1. Write note on “depletion of Forests”.

Ans- Falling of trees for human use has been going on unabated for centuries. Increased urbanization, industrialization and mining have also caused indiscriminate felling of trees and denudation of trees. Still, tribes are using them for firewood and making huts, and also for making handles for their tools, furniture and fence posts. For them, forests had only a present and a past i.e., no future. In India, we are losing more than 1.5 million hectare of forest cover every year. Since independence of country, 23 million hectare of forest has been destroyed, because of over exploitation and misuse and conversion to agricultural fields

In addition to its effects on the economy, health, and natural resources, pollution has social implications. Low-income populations do not receive the same protective from environmental contamination as do higher-income communities. Toxic waste incinerators, chemical plants, and solid waste dumps are often located in low-income communities because of a lack of organized, informed community involvement in municipal decision-making processes.

  1. What are the harmful effects of radiations?

The fragmentation of biologically less vital molecules ( such as water) with the formation of reactive ions or free radicals that can later affect more important molecules and impair their usefulness.

Radiation enters the body on airborne, radioactive dusts and gases, or in food. The death rate from lung cancer in the infamous uranium mines of joachimsthal; bohemia was 30 times normal in the 1930s. Radon, a radioactive decay product of uranium and radium, has been chemically inert but radioactive gas that did not dissipate readily in the mines, which have been worked for lead, cobalt, and arsenic, and the frequency of “lung diseases” among the miners was noted more than 400 years ago.

Ans: The buildup of nuclear weapons with destructive power of 10000 megatons by nuclear powers has been done. The nuclear powers include US, erstwhile USSR, UK, France, Israel and China with several other countries on the threshold of joining this category.

The consequences of a nuclear war have been realized by the superpowers and some steps have already been taken in the direction of reducing the nuclear weapons. But unless steps are taken for the total banning of nuclear arms, the threat of a nuclear war looms large over humanity. The recent dismemberment of the USSR leading to large parts of the nuclear arsenal falling under the control of the feuding member states also adds to this threat.

  1. After a nuclear war, neither humans nor animals will have anything to eat unless something grows. No agriculture can survive under the conditions of Nuclear Winter. It is predicted that the production of food would cease for at least one year in the greater part of the northern Hemisphere and many regions of the Southern Hemisphere. Even if some reserves of food are available somewhere there will be no means to transport these foods and distribute them, since all communications and transport will have collapsed. Consequently the majority of the survivors would die of starvation.

  2. Apart from the nuclear winter other consequences of nuclear war would be

  1. List various threats of dirty radioactive bombs?

Ans. A dirty radioactive bomb consists of an explosive such as dynamite mixed with or wrapped around some radio- active material that is not difficult or expensive to obtain. These are used by terrorist now. The radioactive materials are often stolen from places where these materials are in use for some peaceful applications, e.g., radioisotope (Co-60) is stolen from hospitals where it is used to treat cancer or diagnose various diseases.

  1. It causes intense psychological terror and panic in the area.

  1. Write short note on “There Miles Island and the China Syndrome”.

Much of the blame was directed at the complacency of the nuclear industry with regard of safety. The attitude of the industry had been that nuclear power is essentially safe. Such an attitude is wrong and must be reversed. That is to say, nuclear power must be regarded as potentially dangerous by its very nature, and “one must continually question whether the safeguards already in place are sufficient to prevent major accidents.” the complacent altitude resulted in such lapses that “ an accident like Three Mile Island was eventually inevitable”.

The immediate cause of the accident was a combination of malfunction of equipment and errors by the operators. The commission was especially critical of the confusing design and arrangement of the indicators in the control room. Operators should not shoulder the blame for faulty equipment or gauges. But what about the fact that the operators turned off the cooling pumps when the core was partially exposed by bubbles below? When the feed water flow stopped, the fission reaction was automatically shut down (by the control rods) within 12 seconds. Of course, the radioactivity continued- that cannot ne shutdown. Furthermore, as mentioned previously, the core actually was completely exposed for some time. This evidence is both frightening and, to some people with another point of view, comforting. It is frightening because an accident of a kind that the nuclear industry implies was too unlikely to worry about did really happen. Many people consider that their confidence and trust have been betrayed. On the other hand, the fact that an exposed core did not melt down may mean that a nuclear plant is more resistant to catastrophe than its severest critics believe.

However, at least one type of cancer can be attributed directly to Chernobyl’. There has been a significant rise in the incidence of thyroid cancer among children in the areas where radiation levels are highest. Thyroid cancer rates in Homyel’ Oblast, for example, increased 22- fold from 1986 through 1990 compared to the period from 1981 through 1985.

  1. What is biodiversity?

  1. Genetic diversity

It means diversity of genes within a species. There is a genetic variability among the populations and the individuals of the same species. Genetic diversity is a characteristics of ecosystems that describes an attribute which is commonly held to be advantageous for survival- that there are many different versions of otherwise similar organisms. For example, the Irish potato famine can be attributed in part to the fact that there are so few different genetic strains of potatoes in the country, making it easier for one virus to infect and kill much of a crop.

The diversity among species.

  1. Ecosystem diversity:

For geneticists biodiversity is the diversity of genes and organisms. They study processes such as mutations, gene exchanges, and genome dynamics that occur at the DNA level and generate evolution.

For biologists, biodiversity is the diversity of populations of organisms and species, but also the way these organisms function. Organisms appear and disappear; sites are colonized by organisms of the same species or by another. Some species develop special organizations to improve their reproduction goals or use neighbor species that live in communities. Depending on their environment, organisms do not invariably use the same strategies of reproduction.

If biological resource represents an ecological interest for the community, their economic value is also increasing. New products are developed thanks to biotechnologies, and new markets created. For society, biodiversity also is a field of activity and profit. It requires a proper management setup to determine how these resources are to be used.

Finally, the role of biodiversity is to be a mirror of our relationship with the other living species, an ethical view with rights, duties, and education.

For ecologists, this approach is sometimes considered inadequate and too restricted.

  1. Biodiversity: time and space, comment?

  1. What are hotspots of biodiversity?

Ans. One definition of a hotspot of biodiversity is a spot with many endemic species. Hotspots tend to occur in areas of growing human impact. Most of these spots are located in the tropics.

Ans. Ecologists and environmentalists were the first to insist on the economic aspect of biological diversity protection. Thus, Edward O. Wilson wrote in 1992, that 1a biodiversity est

1’une des plus grandes richness de la plane’te, et pourtant lamoins recoonue comme telle.

  1. Indirect use value, like pollution of plants and other biodiversity services.

  1. Non- use or intrinsic value.

Among the dissenters, some argue that there are not enough data to support the view of mass extinction, and say abusive extrapolation are being made on the global destruction of rainforests, coral reefs, mangrove swamps, and other rich habitats.

  1. What do you mean by endangered species?

  • Extinct: The last remaining member of the species had died, or is presumable to have died beyond reasonable doubt. Examples: Thylacine, Dodo.

  • Extinct in the Wild: Captive individual survive, but there is no free- living, natural population. Examples: Dromedary, przewalski’s Horse.

Endangered mammals:

  • Aye- aye

  • Elephant

  • Fin Whale

  • Gorilla

  • Indria

  • Red Panda

  • Sea Otter

  • Vaquita

Endangered Birds:

  • Chatham Albartross(Thalassarche eremita)

  • Chinese Crested Tern (Sterna bernesteinii)

  • Indian White- rumped Vulture (Gyps bengalensis)

  • Ivory- billed Woodpecker (probably extinct)

  • Kiwi (Apteryx australis, A hastii, A. owenii)

  • Lesser White- Fronted Goose (Anser erythropus)

  • Philippine Eagle (Pithecophaga jefferyi)

  • Red- cockaded Woodpecker (Picoides borealis)

  • Spix’s Macaw (Cyanopsitta spixii)

  • White- headed Duck (Oxyura leucocephala)

  • Desert slender salamander (Batrachoseps aridus)

  • Israel painted frog (Discoglossus nigriventer)

  • African violet ( Saintapaulia ionantha), due to forest clearance

  • Baishanzu fir (Abies benshanzuensis), southest China, three trees known on an isolates mountain summit.

  • Pnus squamata, southwest China, about 20 trees known

  • Saguaro cactus (Carnegia gigantean) of North America, due to over collection, slow maturing, and slow breeding.

Taxonomic group Number of threatened species



Invertebrates Plants




Total 459

Ans. India is one of the 12 mega biodiversity countries of the world. The Country is divided into 10 bio-geographic regions: Trans- Himalayan, Himalayan, Indian Desert, semi- Arid, Western Ghats, Deccan Peninsula, Gangetic Plains, North- East India, Islands and Coasts, and this diversity create rich biodiversity in the country. The wide variety in physical features and climatic situations have resulted in a diversity of ecological habitats like forests, grasslands, wetlands, coastal and marine ecosystems and desert ecosystems, which harbor and sustain the immense biodiversity. With only 2.4% of the total land area of the world, the known biological diversity of India contributes 8% to the known global biological diversity. Currently available data place India in the tenth position in the world and fourth in Asia in the plant diversity. In terms of the number of mammalian species, India ranks tenth in the world; in terms of the endemic species of higher vertebrates, it ranks eleventh. It stands seventh in the world for the number of species contributed to agriculture and animal husbandry.

  1. Write short note on “Hot spots”?

Ans: India has two of the 18 identified ‘hot spots’. These are: Eastern Himalaya and Western Ghats.

Eastern Himalayas

Tea (Thea sinensis) is reported to be in cultivation in this region or the last 4000 years. Many wild and allied species of tea, the leaves of which are used as substitute of tea, are found growing in the North- East in their natural habitats.

As regards faunal diversity, 63% of the genera of land mammals in the India are known from this area. During the last four decades, two new mammals have been discovered from the region: Golden Langur from Assam- Bhutan region, and Namadapha flying squirrel from Arunanchal Pradesh indicating the species richness of the region.

As regards the fauna, as many as 315 species of vertebrates belonging to 22 genera are endemic, these include 12 species of mammals, 13 species of birds, 89 species of reptiles, 87 species of amphibians and 104 species of fish.

The extent of endemism is high in amphibians and reptiles. There occur 117 species of amphibian in the region, of which 89 species (i.e. 76%) are endemic. Of the species of reptiles found in Western Ghats, 88 species are endemic.

  1. Gradual change in climatic caused by continental drift and slight shifts in the earth’s orbit around the sun.

  2. Rapid climates changes caused by cataphoric events, e.g., volcanic eruptions, huge meteorites and asteroids crashing into earth ad and release of large amount of methane trapped beneath the ocean floor. These event create dust clouds for longer duration and cut photosynthesis for long enough to eliminate huge numbers of producers and soon thereafter the consumers that fed on them.

Ans. By natural disasters, it means instantaneous damage on a large scale to the community due to natural catastrophies. The main examples of disasters are earthquake, cyclones, landslides, floods, fires, explosions and epidemics. These disasters cause sudden damage on a very large scale.

In world there are ten hazard- prone countries. India is one of those, and accounts for wall 50% of the world’s major disasters taking place in the last two decades.

The focal depth of an earthquake is the depth from the Earth’s surface to the region where an earthquake’s energy originates (the focus). Earthquakes with focal depths from the surface to about 70 kilometers are classified as shallow. Earthquake with focal depths from 70 to300 kilometers are classified as intermediate. The focus of deep earthquakes may reach depths of more than 700 kilometers. The focuses of most earthquakes are concentrated in the crust and upper mantle. The depth to the center of the Earth’s core is about 6370 kilometers, so even the deepest earthquakes originate in relatively shallow parts of the Earth’s interior.

The epicenter of an earthquake is the point on the Earth’s surface directly above the focus. The location of an earthquake is commonly described by the geographic position of its epicenter and by its focal depth.

  1. How do we measure earthquake?

Ans. The vibration produced by earthquakes are detected, recorded and measured by instruments call seismographs. The zigzag line made by a seismograph, called a “seismogram”, reflects the changing intensity of the vibration by responding to the motion of the ground surface beneath the instruments. From the data expressed in seismograms, scientists can determine the time, the epicenter, the focal depth, and the type of faulting of an earthquake and can estimate how much energy was released.

Magnitude Effects



Major earthquake inflicts serious damage. Roughly 10 occur each year.

Great Earthquakes. Occur once every 5-10 years, produce total destruction to nearby communities.

  1. What are the causes of earthquakes of India?

Ans. Physiographic ally and tectonically, India may be divided into three broad zones such as: Peninsular India, Indo-Genetic plains and the extra peninsular India (Himalayas).

The sea floor in the Indian Ocean in spreading and thereby pushing land inwards in northeast direction at the rate of 5 cm per year and at the same time Saurashtra region is rotating in an anticlockwise direction. The advanced of sea-floor against Indian plate amounts to nearly 125 to 150 cm to 25 to 30 years. It is responsible for the earthquakes not only at the edge of Indian plate and elsewhere in the Himalayas. The rifts are inherently unstable because of pushing and movement of the Indian plates towards north.

The system seems to activate itself in the week every 25 to 30 years because of the shifts.

  1. What are cyclones?

Ans. Cyclone refers to an area of low atmospheric pressure surrounded by a wind system blowing, in the northern hemisphere, in a counterclockwise direction. A corresponding high-pressure area with clockwise wind is known as an anticyclone. In the southern hemisphere these wind direction are reversed. Cyclones are commonly called lows and anticyclones highs. The term cyclone has often been more loosely applied to a storm and disturbance attending such pressure system, particularly the violent tropical hurricane and the typhoon, which center areas of usually low pressure.

Winds at the ground (in the northern hemisphere) blow counterclockwise and inward around the area of low pressure. As the surface wind converge towards the center of the storm, the area gradually rises, often condensing into clouds. The heat released during condensation supplies some of the energy for the storm’s development. Additional energy is derived as the air masses struggle to obtain equilibrium. Warm air rises along the warm front and cold air sinks behind the cold front. The rising and sinking air transforms potential energy into kinetic energy.

The storm’s development and movement depend upon the winds aloft. Strong winds above the storm quickly sweep the rising air downwind. If the wind aloft remove the air above the storm more quickly than the surface air converges, the surface pressure drops and the storm system intensifies. Conversely, if the converging surface air is greater than the removal of air loft, the surface pressure rises and the storm system weakens. Because the winds above the surface typically blow from the southwest (in the northern hemisphere), the center of the surface low normally moves northeastward.

Tropical cyclones tend to form along a weak area of low pressure, called a disturbance or wave, in the intertropical convergence zone (ITCZ). As the disturbance becomes more organized, it first becomes a tropical depression, then a tropical storm, then finally a tropical cyclone. For the tropical to intensity, the outflow of air above the storm must exceed the inflow of air in the bottom. Tropical cyclones derive their energy from the transfer of heat from the warm water and from the latent heat given up to the system during condensation. Tropical cyclones dissipate when they are cut off from their energy sources either moving over cold water or a large land mass. Although tropical cyclones often take erratic paths, the prevailing easterly winds in the tropic tend to steer tropical cyclones westward or northwestward until they leave the tropics, then the prevailing westerlies tend to sweep northeastward.

  1. What are the disastrous effects of cyclones?

  1. What is drought?

Ans. Drought is condition of abnormally dry weather within a geographic region where some rain might usually be expected. A drought is thus quite different from a dry climate, which designates a region that is normally, or at least seasonally, dries.

  1. What are the effects of drought on environment?

Ans. A drought can also enhance pressures on the environment in terms of falling ground water table Sand reduced tree cover. Because of a power crisis due to the expected shortfall in hydro power generation, the industrial production becomes low.

Ans. Water is considered to be the greatest of all geological phenomenon hazardous to man. In rivers and streams, water flows uniformly but from time to time water over- flow the banks of rivers and streams. This is known as flooding. Due to flooding, the areas adjacent to rivers and streams get enough water, thereby causing enormous damage. In India, floods frequently occur in the rainy season. However, in the temperate areas and snow- rich winter areas, floods occur due to more production of water than the rivers can hold.

  1. How flood affect us?

  1. What are the effects of oil spills on ocean ecosystems?

Ans. Crude petroleum is accidentally or sometimes deliberately released into the environment from a number of sources.

  1. Some other chemicals form tarlike globs that float on the surface and coat the feathers of birds (especially diving birds) and the fur of marine mammals. This oil coating destroys their natural insulation and buoyancy, causing many of them to drown or die of exposure from loss of body heat.

  2. Heavy oil components that sink to the ocean floor or wash into estuaries can smother bottom- dwelling organisms such as crabs, oysters, mussels, and calms or make them unfit for human consumption. Some oil spills have killed reef corals.

Fire can burn off floating oil, but crude oil is hard to ignite, and this approach produces air pollution. In time, the natural action of wind and waves mixes or emulsifies oil with water (like emulsified salad dressing), and bacteria biodegrade some of the oil.

Evidence for this approach comes from a number of oil tanker spills. One is the large 1989 spill from the Exxon Valdez oil tanker in Alaska’s Prince William Sound hat ended up costing $6 billion, including cleanup costs and damage fines. Another is the massive oil spill when the oil tanker Prestige sank off the coast of Spain in 2002. The ship is expected to leak about twice as much oil as the Exxon Valdez for years, possibly until 2006.Both of these spills would probably not have happened if the tankers had been equipped with double hulls instead of single hulls.

Ans. Scientists use elaborate computer models of temperature, precipitation patterns, and atmosphere circulation to study global warming. Based on these models, scientists have made several predictions about how global warming will affect weather, seal levels, coastlines, agriculture, wildlife, and human health.

  1. Weather

As the atmosphere warms, the surface layer of the ocean warms as well, expanding in volume and thus raising sea level. Warming will also melt much glacier ice, especially around Greenland, further swelling the sea. Sea levels worldwide rose 10 to 25cm (4 to 10 in) during the 20th century, and scientist predict a further rise of 9 to 88 cm (4 to 35 in) in the 21st century.

Sea – level changes will complicate life in many coastal regions. A 100 cm (40-in) rise could submerge 6 percent of The Netherlands, 17.5 percent of Bangladesh, and most or all of many islands.

  1. Human Health

In a warmer world, scientist predict the more people will get sick or die from the heat stress, due less to hotter days that to warmer nights (giving the sufferers less relief). Disease now find in the tropics, transmitted by mosquitoes and other animal hosts, will widen their range as these animals hosts move into region formally too cold for them. Today 45 percent of the world people live their where they might get bitten by a mosquito carrying the parasite that causes malaria; that percentage would increase to 60 percent if temperature rise. Other tropical disease may spread similarly, including dengue fever, yellow fever and encephalitis. Scientist also predict rising incidence of allergies and respiratory diseases as warmer air grows more charged with pollutant, mold spores, and pollens.

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