Environment

Monthly Project

By-R.Satish Kumar
IGCSE

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INDEX

Sr. No. | Title | Page No. | 1 | Environment | 1 | 2 | Atmosphere | 3 | 3 | Hydrosphere | 8 | 4 | Lithosphere | 13 | 5 | Biosphere | 21 | 6 | Interdependence Between The Four Spheres | 26 | 7 | Human Impact On The Environment | 32 |

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ENVIRONMENT

The geographical conditions that surrounds the man on the earth is known as environment. The landforms, water, climate, natural vegetation, minerals, etc. are natural phenomena. These comprise the physical environment. In order to fulfill his requirements, man has made a number of changes in natural environment. The man-made features such as agriculture, buildings, roads, settlements, dams, etc. are considered as cultural environment.

Four Parts of Environment 1. Atmosphere :- The atmosphere is a mixture of nitrogen (78%), oxygen (21%), and traces (remaining 1%) of carbon dioxide, argon, water vapor and other components. Although the atmosphere is approximately 1,100 km high, the stratosphere (10 to 50 km) and the troposphere (less than 10 km) are the main atmospheric interactors of the biosphere. The atmosphere is a prime mean for the spatial diffusion of pollutants and a temporary mean of their accumulation.

2. Hydrosphere :- The hydrosphere is the accumulation of water in all its states (solid, liquid and gas) and the elements dissolved it in (sodium, magnesium, calcium, chloride and sulphate). 97% of the water forms the oceans, 2% is ice (north and south poles) and 1% forms rivers, lakes, ground water and atmospheric vapor. It covers around 71% of the earth's surface and is an important accumulator of pollutants and a significant vector of diffusion.

3. Lithosphere :- The lithosphere is the thin crust between the mantle and the atmosphere. Although the lithosphere is around 100 km thick, only 1 km of it can be considered in interaction with the biosphere. Main constituents are oxygen (47%), silicon (28%), aluminum (8%), iron (5%), calcium (4%), sodium (3%), potassium (3%) and magnesium (2%) in a crystalline state. The lithosphere is the main source of pollutants and a permanent accumulator. Some are naturally released through sources like volcanic eruptions, while others like fossil fuels are the result of artificial extraction and combustion.

4. Ecosphere (Biosphere):- The ecosphere is the set of all living organisms, including animals and vegetal. They are temporary accumulators (like lead) and sources for pollutants (natural forest burning) in a very complex set of relationships with the atmosphere, hydrosphere and lithosphere.

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ATMOSPHERE
Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly 78% nitrogen and 21% oxygen, trace amounts of other gases, and water vapor. This mixture of gases is commonly known as air. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.
The atmosphere has no abrupt cut-off. It slowly becomes thinner and fades away into space. There is no definite boundary between the atmosphere and outer space. Three-quarters of the atmosphere's mass is within 11 km of the planetary surface. In the United States, persons who travel above an altitude of 50.0 miles (80.5 km) are designated as astronauts. An altitude of 120 km (75 mi or 400,000 ft) marks the boundary where atmospheric effects become noticeable during re-entry. The Karman line, at 100 km (62 mi), is also frequently used as the boundary between atmosphere and space.
The evolution of the Earth's atmosphere The history of the Earth's atmosphere prior to one billion years ago is poorly understood, but the following presents a plausible sequence of events. This remains an active area of research.
The modern atmosphere is sometimes referred to as Earth's "third atmosphere", in order to distinguish the current chemical composition from two notably different previous compositions. The original atmosphere was primarily helium and hydrogen. Heat (from the still-molten crust, and the sun) dissipated this atmosphere.

About 3.5 billion years ago, the surface had cooled enough to form a crust, still heavily populated with volcanoes which released steam, carbon dioxide, and ammonia. This led to the "second atmosphere", which was primarily carbon dioxide and water vapor, with some nitrogen but virtually no oxygen (though very recent simulations run at the University of Waterloo and University of Colorado in 2005 suggested that it may have had up to 40% hydrogen . This second atmosphere had approximately 100 times as much gas as the current atmosphere. It is generally believed that the greenhouse effect, caused by high levels of carbon dioxide, kept the Earth from freezing.
During the next few million years, water vapor condensed to form rain and oceans, which began to dissolve carbon dioxide. Approximately 50% of the carbon dioxide would be absorbed into the oceans. One of the earliest types of bacteria were the cyanobacteria. Fossil evidence indicates that these bacteria existed approximately 3.3 billion years ago and were the first oxygen-producing evolving phototropic organisms. They were responsible for the initial conversion of the earth's atmosphere from an anoxic state to an oxic state (that is, from a state without oxygen to a state with oxygen). Being the first to carry out oxygenic photosynthesis, they were able to convert carbon dioxide into oxygen, playing a major role in oxygenating the atmosphere.
Photosynthesizing plants would later evolve and convert more carbon dioxide into oxygen. Over time, excess carbon became locked in fossil fuels, sedimentary rocks (notably limestone), and animal shells. As oxygen was released, it reacted with ammonia to create nitrogen; in addition, bacteria would also convert ammonia into nitrogen.
As more plants appeared, the levels of oxygen increased significantly, while carbon dioxide levels dropped. At first the oxygen combined with various elements (such as iron), but eventually oxygen accumulated in the atmosphere, resulting in mass extinctions and further evolution. With the appearance of an ozone layer (ozone is an allotrope of oxygen) lifeforms were better protected from ultraviolet radiation. This oxygen-nitrogen atmosphere is the "third atmosphere".

Temperature anypd the atmospheric layers
The temperature of the Earth's atmosphere varies with altitude; the mathematical relationship between temperature and altitude varies between the different atmospheric layers:
1) Troposphere: From the Greek word "tropos" meaning to turn or mix. The troposphere is the lowest layer of the atmosphere starting at the surface going up to between 7 km at the poles and 17 km at the equator with some variation due to weather factors. The troposphere has a great deal of vertical mixing due to solar heating at the surface. This heating warms air masses, which then rise to release latent heat as sensible heat that further buoys the air mass. This process continues until all water vapor is removed. In the troposphere, on average, temperature decreases with height due to expansive cooling.
2) Stratosphere: from that 7–17 km range to about 50 km, temperature increasing with height.

3) Mesosphere: from about 50 km to the range of 80 km to 85 km, temperature decreasing with height.
4) Thermosphere: from 80–85 km to 640+ km, temperature increasing with height.
The boundaries between these regions are named the tropopause, stratopause, and mesopause.The average temperature of the atmosphere at the surface of earth is 14 °C.

Various atmospheric regions
Atmospheric regions are also named in other ways:
1) Inosphere – the region containing ions: approximately the mesosphere and thermosphere up to 550 km.
2) Exosphere – above the ionosphere, where the atmosphere thins out into space. This is the last major atmosphere. (“Exo” means “outside” in Greek.)
3) Magnetosphere – the region where the Earth's magnetic field interacts with the solar wind from the Sun. It extends for tens of thousands of kilometers, with a long tail away from the Sun.
4) Ozone Layer – or ozonosphere, approximately 10 - 50 km, where stratospheric ozone is found. Note that even within this region, ozone is a minor constituent by volume.
5) Upper atmosphere – the region of the atmosphere above the mesopause.
6) Van Allen radiation belts – regions where particles from the Sun become concentrated. Composition of dry atmosphere, by volume | ppmv: parts per million by volume | Gas | Volume | Nitrogen (N2) | 780,840 ppmv (78.084%) | Oxygen (O2) | 209,460 ppmv (20.946%) | Argon (Ar) | 9,340 ppmv (0.9340%) | Carbon dioxide (CO2) | 381 ppmv | Neon (Ne) | 18.18 ppmv | Helium (He) | 5.24 ppmv | Methane (CH4) | 1.745 ppmv | Krypton (Kr) | 1.14 ppmv | Hydrogen (H2) | 0.55 ppmv | Not included in above dry atmosphere: | Water vapor (highly variable) | typically 1% |
Composition

Density and mass
The density of air at sea level is about 1.2 kg/m3. Natural variations of the barometric pressure occur at any one altitude as a consequence of weather. This variation is relatively small for inhabited altitudes but much more pronounced in the outer atmosphere and space due to variable solar radiation.
The atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula. More sophisticated models are used by meteorologists and space agencies to predict weather and orbital decay of satellites.
The average mass of the atmosphere is about 5,000 trillion metric tons. According to the National Center for Atmospheric Research, "The total mean mass of the atmosphere is 5.1480 x 1018 kg with an annual range due to water vapor of 1.2 or 1.5 x 1015 kg depending on whether surface pressure or water vapor data are used; somewhat smaller than the previous estimate. The mean mass of water vapor is estimated as 1.27 x 1016 kg and the dry air mass as 5.1352 ±0.0003 x 1018 kg."
The above composition percentages are done by volume. Assuming that the gases act like ideal gases, we can add the percentages p multiplied by their molar masses m, to get a total t = sum (p·m). Any element's percent by mass is then p·m/t. When we do this to the above percentages, we get that, by mass, the composition of the atmosphere is 75.523% nitrogen, 23.133% oxygen, 1.288% argon, 0.053% carbon dioxide, 0.001267% neon, 0.00029% methane, 0.00033% krypton, 0.000724% helium, and 0.0000038 % hydrogen.
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HYDROSPHERE
The hydrosphere includes all water on Earth. In one respect, planet Earth is a misnomer in that 71% of the earth is covered by water and only 29% is terra firma. Indeed, the abundance of water on Earth is a unique feature that clearly distinguishes our "Blue Planet" from others in the solar system. Not a drop of liquid water can be found anywhere else in the solar system. It is because the Earth has just the right mass, the right chemical composition, the right atmosphere, and is the right distance from the Sun (the "Goldilocks" principle) that permits water to exist mainly as a liquid. However, the range of surface temperatures and pressures of our planet permit water to exist in all three states: solid (ice), liquid (water), and gas (water vapor). Most of the water is contained in the oceans and the high heat capacity of this large volume of water (1.35 million cubic kilometers) buffers the Earth surface from large temperature changes such as those observed on the moon. Water is the universal solvent and the basis of all life on our Planet. It is an essential life-sustaining resource which led Benjamin Franklin to comment "When the well's dry, we know the worth of water."

The hydrologic cycle is a conceptual model that describes the storage and movement of water between the biosphere, atmosphere, lithosphere, and the hydrosphere .Water on this planet can be stored in any one of the following reservoirs: atmosphere, oceans, lakes, rivers, soils, glaciers, snowfields, and groundwater. Hydrologic Cycle.
Water moves from one reservoir to another by way of processes like evaporation, condensation, precipitation, deposition, runoff, infiltration, sublimation, transpiration, melting, and groundwater flow. The oceans supply most of the evaporated water found in the atmosphere. Of this evaporated water, only 91 % of it is returned to the ocean basins by way of precipitation. The remaining 9 % is transported to areas over landmasses where climatologically factors induce the formation of precipitation. The resulting imbalance between rates of evaporation and precipitation over land and ocean is corrected by runoff and groundwater flow to the oceans.
The planetary water supply is dominated by the oceans .Approximately 97 % of all the water on the Earth is in the oceans. The other 3 % is held as freshwater in glaciers and icecaps, groundwater, lakes, soil, the atmosphere, and within life.

Inventory of water at the Earth's surface. Reservoir | Volume (cubic km x 1,000,000) | Percent of Total | Oceans | 1370 | 97.25 | Ice Caps and Glaciers | 29 | 2.05 | Groundwater | 9.5 | 0.68 | Lakes | 0.125 | 0.01 | Soil Moisture | 0.065 | 0.005 | Atmosphere | 0.013 | 0.001 | Streams and Rivers | 0.0017 | 0.0001 | Biosphere | 0.0006 | 0.00004 |
Water is continually cycled between its various reservoirs. This cycling occurs through the processes of evaporation, condensation, precipitation, deposition, runoff, infiltration, sublimation, transpiration, melting, and groundwater flow. Table 8b-2 describes the typical residence times of water in the major reservoirs. On average water is renewed in rivers once every 16 days. Water in the atmosphere is completely replaced once every 8 days. Slower rates of replacement occur in large lakes, glaciers, ocean bodies and groundwater. Replacement in these reservoirs can take from hundreds to thousands of years. Some of these resources (especially groundwater) are being used by humans at rates that far exceed their renewal times. This type of resource use is making this type of water effectively nonrenewable. Typical residence times of water found in various reservoirs. Reservoir | Average Residence Time | Glaciers | 20 to 100 years | Seasonal Snow Cover | 2 to 6 months | Soil Moisture | 1 to 2 months | Groundwater: Shallow | 100 to 200 years | Groundwater: Deep | 10,000 years | Lakes | 50 to 100 years | Rivers | 2 to 6 months |

The hydrosphere, like the atmosphere, is always in motion. The motion of rivers and streams can be easily seen, while the motion of the water within lakes and ponds is less obvious. Some of the motion of the oceans and seas can be easily seen while the large scale motions that move water great distances such as between the tropics and poles or between continents are more difficult to see. These types of motions are in the form of currents that move the warm waters in the tropics toward the poles, and colder water from the polar regions toward the tropics. These currents exist on the surface of the ocean and at great depths in the ocean (up to about 4km). The characteristics of the ocean which affects its motion are its temperature and salinity. Warm water is less dense or lighter and therefore tends to move up toward the surface, while colder water is more dense or heavier and therefore tends to sink toward the bottom. Salty water is also more dense or heavier and thus tends to sink, while fresh or less salty water is less dense or lighter and thus tends to rise toward the surface. The combination of the water's temperature and salinity determines whether it rises to the surface, sinks to the bottom or stays at some intermediate depth. | The oceans currents are also affected by the motion of the atmosphere, or winds, above it. The energy in the wind gets transferred to the ocean at the ocean surface affecting the motion of the water there. The effect of wind is largest at the ocean surface. The ocean serves two main purposes in the climate system. First, it is a large reservoir of chemicals that can contribute to the greenhouse effect in the atmosphere and energy absorbing 90% of the solar radiation which hits the surface. This reservoir changes very slowly limiting how fast the climate can change. Second, it works with the atmosphere to redistribute the energy received from the sun such that the heat in the topics, where a lot of energy is received from the sun, is transferred toward the poles, where heat is generally lost to space. |
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LITHOSPHERE

Lithosphere The crust of the Earth which is solid in form is made of various rocks & minerals. The thickness of the crust varies from 5 to 40 km. It is shallower in oceanic areas & thicker in continental areas have greater proportion of silica & aluminum. These are therefore called SIAL. Below the sail exists matter containing silica & magnesium. Hence these are called SIMA.

Interior of Earth

Crust: A layer of solid rock. There are two types of crust :- * Continental crust * Oceanic Crust

Mantle: A thick layer of solid dense rock which is rich in magnesium & silicon. Parts of mantle move slowly. Temperature in mantle varies from 1000 0C to 3000 0C.

Asthenosphere: The boundary between the crust & the mantle.

Core: Core is after mantle. There are two types of core :- * Outer Core * Inner Core

Outer Core: Very Dense liquid rock at high temperature of about 4000 0C composed of nickel & iron. The earth’s magnetic field arises here.

Inner Core: Solid rock at very high temperature of about 6000 0C & pressure composed of nickel & iron.

On the basis of modes of their formation rocks are classified as :- * Igneous Rocks * Sedimentary Rocks * Metamorphic Rocks

Types Of Rocks

Igneous Rocks Igneous rocks are called fire rocks and are formed either underground or above ground. Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets. As these pockets of magma cool slowly underground, the magma becomes igneous rocks. These rocks are called Plutonic igneous rocks.

Igneous rocks are also formed when volcanoes erupt, causing the magma to rise above the earth's surface. When magma appears above the earth, it is called lava. Igneous rocks are formed as the lava cools above ground.

Examples Granite Rocks: Granite rocks are igneous rocks which were formed by slowly cooling pockets of magma that were trapped beneath the earth's surface. Granite is used for long lasting monuments and for trim and decoration on buildings.

Scoria Rocks: Scoria rocks are igneous rocks which were formed when lava cooled quickly above ground. You can see where little pockets of air had been. Scoria is actually a kind of glass and not a mixture of minerals.

Obsidian Rocks: Obsidian rocks are igneous rocks that form when lava cools quickly above ground. Obsidian is actually glass and not a mixture of minerals. The edges of this rock are very sharp.

Sedimentary Rocks For thousands, even millions of years, little pieces of our earth have been eroded-broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.
Sedimentary rocks are formed in two ways :- * Some are formed by pressing together or compacting loose particles which have been deposited on land or in water bodies such as seas or lakes. These loose particles are called sediments. * Sedimentary rocks are also formed by the crystallization of dissolved minerals.

Examples
Sandstone Rocks: Sandstone rocks are sedimentary rocks made from small grains of the minerals quartz and feldspar. They often form in layers. They are often used as building stones.

Limestone Rocks: Limestone rocks are sedimentary rocks that are made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells. This rock is used in concrete and is an excellent building stone for humid regions.

Gypsum Rocks: Gypsum rocks are sedimentary rocks made up of sulfate mineral and formed as the result of evaporating sea water in massive prehistoric basins. It is very soft and is used to make Plaster of Paris, casts, molds, and wallboards.

Metamorphic Rock Metamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks.
How do sedimentary and igneous rocks change? The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change. As they are derived from previously existing igneous, sedimentary or even metamorphic rock, their appearance is variable. They are identified by the types of minerals they contain and their texture.

Examples
Schist Rocks: Schist rocks are metamorphic. These rocks can be formed from basalt, an igneous rock shale, a sedimentary rock; or slate, a metamorphic rock. Through tremendous heat and pressure, these rocks were transformed into this new kind of rock.

Gneiss Rocks: Gneiss rocks are metamorphic. These rocks may have been granite, which is an igneous rock, but heat and pressure changed it. The mineral grains in the rock were flattened through tremendous heat and pressure and are arranged in alternating patterns.

The Rock Cycle

The Rock Cycle is a group of changes. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock.
Igneous rock forms when magma cools and makes crystals. Magma is a hot liquid made of melted minerals. The minerals can form crystals when they cool. Igneous rock can form underground, where the magma cools slowly. Or, igneous rock can form above ground, where the magma cools quickly. When it pours out on Earth's surface, magma is called lava. Yes, the same liquid rock matter that you see coming out of volcanoes. On Earth's surface, wind and water can break rock into pieces. They can also carry rock pieces to another place. Usually, the rock pieces, called sediments, drop from the wind or water to make a layer. The layer can be buried under other layers of sediments. After a long time the sediments can be cemented together to make sedimentary rock. In this way, igneous rock can become sedimentary rock.
All rock can be heated. But where does the heat come from? Inside Earth there is heat from pressure. There is heat from friction. There is also heat from radioactive decay. So, what does the heat do to the rock? It bakes the rock. Baked rock does not melt, but it does change. It forms crystals. If it has crystals already, it forms larger crystals. Because this rock changes, it is called metamorphic. Remember that a caterpillar changes to become a butterfly. That change is called metamorphosis. Metamorphosis can occur in rock when they are heated to 300 to 700 degrees Celsius. When Earth's tectonic plates move around, they produce heat. When they collide, they build mountains and metamorphose (met-ah-MORE-foes) the rock. The rock cycle continues. Mountains made of metamorphic rocks can be broken up and washed away by streams. New sediments from these mountains can make new sedimentary rock. The rock cycle never stops.
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The environment on the planet earth is most favorable for the existence of biotic world. The Earth is inhabited by a variety of the families of microscopic organisms, .insects, vegetation and animals. In the biosphere, we study the distribution of all these life forms on the surface of the earth. The biosphere is largely influenced by the abiotic component of the environment such as atmosphere, lithosphere and hydrosphere.

Importance of the-.Biosphere Out of the basic needs of life. such as food, clothing and shelter man depends wholly on the biosphere for his requirement to food, The other two needs are also to some extent fulfilled by the biosphere. All the life forms depend on biosphere for their food. The vegetal world is used for chemical and pharmaceutical industries. Man makes use of the animal world, to get materials, like meat, skin, wool, etc. various purposes.' Plants consume carbon-di-oxide and release oxygen required by other living things. In the process they help to maintain the environmental balance. Microscopic bacterias decompose the dead bodies of living things. Earth worms increase fertility of soils.

However, man has been denuding forests to build cities. He has adversely harmed the biosphere. Urban areas have scanty natural vegetation and animals. Then again, with problems like air, water and noise pollution coupled with the tension of fast city life, the urban folk are compelled to take refuge at the tourist, centres for recuperation and recreation. As man has caused damage to the different components of biosphere the environmental balance too has been disturbed. If he does not take proper care in time his future will be full of difficulties and frequent calamities.

Hence it is necessary to study all the components of biosphere, as also the relationship of man and the environment.

Ecology'and Ecosystem
The relationship among the different constituents of ' biotic world and their interaction with abiotic components of environment form the core of the science of ecology.

'Ecosystem' is studied in ecology. It studies the relationship of the vegetal and animal world including man with the environment. Environment has different types of ecosystems.Components of ecosystem:

An ecosystem always consists of biotic and abiotic components. All living things are included in its biotic part. The vegetation, insects, micro-organisms, animals and man are all parts of the biotic world. The inanimate things in the environment, such as rocks, land, water, climate etc., together form the abiotic or the non-living world. The biotic and abiotic component influence each other. For example, rocks are weathered by the growing roots of trees and the soils are formed out of .the weathered materials. The trees depend on soils for their nutritional requirements.

Environment is not the same allover the world. The biotic world of a region with a given environment differs considerably from the biotic world of another region. Plant life, for example, from warm areas differs considerably from that of colder regions.

The Biotic Producers during the day plants produce food for themselves through the process of photosynthesis. Hence plants are called 'producers'. Plants take the carbon-di-oxide from the atmosphere through their leaves and water through the roots, with the help of sunlight and the chlorophyll, the carbon-di-oxide and water form compounds and in the process carbohydrates and oxygen are produced. Oxygen is released into the atmosphere through the leaves and carbohydrates are used by plants for their growth.Sometimes the carbohydrates are stored in the form of various sugars in the leaves of the plants. This process is known as 'photosynthesis’

The entire biotic world from micro-organisms to man. are not capable of producing food by themselves. They consume the food produced by plants. Hence all the biotic world which consumes food is included under category of 'consumers'. However, not all the animals eat the vegetal produce. Those who wholly depend on the vegetation for their food requirement are called herbivores. These are primary consumers. Then there are those who eat animal flesh. Instead .of the vegetal produce they consume those animals who depend on vegetal products.. These are called carnivores. These are secondary consumers. The animals which these secondary consumers eat are basically herbivores. But some animals eat the secondary consumers as well. These are called the tertiary consumers.

The Biotic Decomposers The micro-organisms thrive on the dead bodies of' living organism, are called decomposers. They perform the important task of decomposing the dead bodies of living organisms after their life cycle is complete. The decomposed material gets dissolved into water and enters the soil. It may be recycled into the process if and when it is absorbed by roots of plants. Thus all the components of the living world are related to each other.

Food chain Plants produce food. The primary consumers depend on the vegetal world for their food. The secondary and tertiary consumers depend on animals for their food requirement. The bacteria and other microscopic animals act as decomposers. They return the material contained in dead bodies back to abiotic worl4 which then becomes available for plant growth. Thus food is transferred from one component to another and directed back to the producers. This cycle is known as food chain. Food Pyramid and Energy Flow The energy received from the Sun, gets reduced every stage from the primary consumers to tertiary consumers.

This is because at every step, part of the energy is used up by the organism for its growth. Moreover, the number of consumers at each step depends on available energy. The number of consumers in each step goes on decreasing. Thus from the producer to the highest level of the consumer the number of organisms decreases. If we try to draw the diagram, representing the number of produces, the primary consumers, the secondary consumers and the tertiary consumers, it resembles a pyramid. Hence it is called the food pyramid.
In the food pyramid, plants form the base while man is at its apex. The number of animals and vegetation is much larger, than that of man. . Such a food pyramid is considered to be balanced pyramid. In such a condition all the processes in biosphere take place smoothly. . If however, for any' reason the number in any layer of pyramid changes it is likely to disturb the balance. It will have an adverse effect not only on the organisms of that particular layer but the whole pyramid itself. The increase in the population of human beings, unprecedented growth of cities and the development of

industries, the increase of the demand for raw materials for industries in recent times has led to clearing of the forests to an alarming extent. Game hunting has also caused considerable decrease in the population of wild animals. Thus the strength in lower levels of pyramid is decreasing while the number of human population has at be~n .increasing. The food pyramid as been disturbed. This is going to exert stress on the biosphere. All will have an adverse effect on human life. Hence strong and stringent measures w1l1 have to be taken 10 order to restore order in the processes of biosphere.

Though the most intelligent, man is very much a part of the biosphere, and not apart from it. Hence it is imperative for him to take care not only of him self but also of all other elements of the biotic world. It is necessary to conserve forests and other animals forming inseparable links in the chain of food pyramid for maintaining the balance of environment. His very survival depends on that.

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INTERDEPENDENCE BETWEEN THE FOUR SPHERES

Earth System Science
In the phrase "Earth system science (ESS)," the key term is "system." A system is a collection of interdependent parts enclosed within a defined boundary. Within the boundary of the earth is a collection of four interdependent parts called "spheres." Earth's spheres include:

1. The lithosphere, which contains all of the cold, hard, solid rock of the planet's crust (surface), the hot semi-solid rock that lies underneath the crust, the hot liquid rock near the center of the planet, and the solid iron core (center) of the planet

2. The hydrosphere, which contains all of the planet's solid, liquid, and gaseous water, 3. The biosphere, which contains all of the planet's living organisms, and 4. The atmosphere, which contains all of the planet's air.
These spheres are closely connected. For example, many birds (biosphere) fly through the air (atmosphere), while water (hydrosphere) often flows through the soil (lithosphere). In fact, the spheres are so closely connected that a change in one sphere often results in a change in one or more of the other spheres. Such changes that take place within an ecosystem are referred to as events.Events can occur naturally, such as an earthquake or a hurricane, or they can be caused by humans, such as an oil spill or air pollution. An event can cause changes to occur in one or more of the spheres, and/or an event can be the effect of changes in one or more of Earth's four spheres. This two-way cause and effect relationship between an event and a sphere is called an interaction. Interactions also occur among the spheres; for example, a change in the atmosphere can cause a change in the hydrosphere, and vice versa.
Interactions that occur as the result of events such as floods and forest fires impact only a local region, meaning the flood waters can only travel so many miles from the original stream, and only the trees that lie within the area on fire will be burned. On the other hand, the effects of events such as El Nino or ozone depletion may cause interactions that can be observed worldwide. For example, the El Nino event--a change in the ocean currents off the coast of Peru-- can cause changes in weather patterns all the way across North America, while ozone depletion above Antarctica may result in increased levels of ultra-violet B radiation around the world. Understanding the interactions among the earth's spheres and the events that occur within the ecosystem allows people to predict the outcomes of events. Being able to predict outcomes is useful when, for example, developers wish to know the environmental effects of a project such as building an airport before they begin construction.
Understanding the interactions that occur in the earth system also helps people to prepare for the effects of natural disasters such as volcanic eruptions; this understanding allows people to predict things like how far and in what direction the lava will flow. This relatively new field of studying the interactions between and among events and the earth's spheres is called

Earth system science (ESS). There are ten possible types of interactions that could occur within the earth system. Four of these interactions are between the event and each of the earth's spheres: event lithosphere event hydrosphere event biosphere event atmosphere
The double-headed arrows () indicate that the cause and effect relationships of these interactions go in both directions; for example, "event hydrosphere" refers to the effects of the event on the hydrosphere, as well as the effects of the hydrosphere on the event. These four types of interactions can be illustrated in the Earth System Diagram below:

In addition to the above four event sphere interactions, there are six interactions that occur among the earth's spheres: lithosphere hydrosphere lithosphere biosphere lithosphere atmosphere hydrosphere biosphere hydrosphere atmosphere biosphere atmosphere
Again, the double-headed arrows () indicate that the cause and effect relationships of the interactions go in both directions; for example, "lithosphere hydrosphere" refers to the effects of the lithosphere on the hydrosphere, as well as the effects of the hydrosphere on the lithosphere.

These six types of interactions can be illustrated in gray in the Earth System Diagram below (note the four event sphere interactions are also included in this diagram, they are depicted in gold):

The ten types of interactions that can occur within the earth system often occur as a series of chain reactions. This means one interaction leads to another interaction, which leads to yet another interaction--it is a ripple effect through the earth's spheres. For example, a forest fire may destroy all the plants in an area (event biosphere). The absence of plants could lead to an increase in erosion--washing away--of soil (biosphere lithosphere). Increased amounts of soil entering streams can lead to increased turbidity, or muddiness, of the water (lithosphere hydrosphere). Increased turbidity of stream water can have negative impacts on the plants and animals that live in it (hydrosphere biosphere).
An Example of an Earth System Science Analysis.
An ESS analysis was performed on the forest fires event that occurred in Yellowstone National Park, Wyoming. This forest fires event occurred in 1988 and destroyed tremendous areas of the park.

Below are some of the event sphere interactions discovered during an ESS analysis of the Yellowstone forest fires event: Event HydrosphereA lack of moisture in the soil and in vegetation may have provided a dry environment in which the fires, once burning, could continue to burn. Heat from the fire may have further removed moisture from the air, soil, and vegetation through the process of evaporation. Event AtmosphereA lightning strike from the air may have started the fires by igniting the dry vegetation. Gaseous pollutants such as carbon dioxide (CO2) may have been produced during the burning of the vegetation and carried into the air by the wind. Event LithosphereThe intense heat from the fires may have caused some rocks to break apart. Event BiosphereDead branches and pine needles on the ground may have provided fuel for the fires. The seeds of some plants may have required that their outer shells be burned before they could germinate; therefore they benefited from the forest fires. |
Below are some of the sphere sphere interactions discovered during the ESS analysis of the Yellowstone forest fires event: Lithosphere Hydrosphere Increased erosion of loose soil (see "Lithosphere Biosphere," below) may have led to increased sediments (i.e. soil particles) in streamwater, making the water "muddier." Lithosphere Biosphere A decrease in vegetation may have resulted in increased soil erosion because there were fewer roots to hold the soil in place. Lithosphere Atmosphere Ash particles in the air may have been carried by the wind and dropped on the ground miles away from the forest fires; the ash particles--which have a high pH--may have changed the pH of the soil. . Hydrosphere Biosphere Ash particles in the water may have clogged the gills of fish and other aquatic organisms and choked them. Hydrosphere Atmosphere There may have been more precipitation in neighboring areas because ash particles in the air may have become condensation centers upon which raindrops could form. Very dry, windy air may have drawn moisture out of the living grasses and trees through the process of evaporation. Biosphere Atmosphere Smoke in the air may have coated the lungs of animals--including people--and affected their ability to breathe. |

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HUMAN IMPACT ON THE ENVIRONMENT |

Interrelationships
The Earth has limited to resources to support populations of humans and other organisms.Our ever increasing human numbers is depleting many of our planet's resources and placing severe stress on the natural processes that renew many of our resources.
Ecosystem Processes
Natural ecosystems are involved in a wide variety of natural processes influencing humans and other organisms.The activities of humans in the environment are changing many of these natural processes in a harmful fashion.Some of these natural processes and a brief description of a human influence on these processes is indicated in the table which follows. Human Influence on Some Ecosystem Processes | Ecosystem Process | Human Influence | Generation of Soils | Agricultural practices have exposed soil to the weather resulting in great loss of topsoil. | Control of the Water Cycle | The cutting of forests and other human activities have allowed increased uncontrolled runoff leading to increased erosion and flooding. | Removal of Wastes | Untreated sewage wastes and runoff from farms and feedlots have led to increased water pollution. | Energy Flow | Some industries and nuclear plants have added thermal pollution to the environment. The release of some gases from the burning of fossil fuels may be slowly increasing the Earth's temperature. (Greenhouse Effect). | Nutrient Recycling | The use of packaging material which does not break down, burning of refuse, and the placing of materials in landfills prevents the return of some useful materials to the environment. |
Some Detrimental Human Activities
Humans are part of the Earth's ecosystem. Human activities can either deliberately or inadvertently alter the balance of an ecosystem. This destruction of habitat, whether accidental or intentional, is threatening the stability of the planet's ecosystems. If these human influences are not addressed, the stability of many ecosystems may be irreversibly affected. Some of the ways that humans damage and destroy ecosystems are indicated in the table below. Some Ways Humans Adversely Influence Ecosystems | Human Influence | Effect on Ecosystems | Population growth | Our increasing numbers are using excessive amounts of the Earth's limited resources. | Over consumption | Industrialized societies are using more resources per person from our planet than people from poor nations. | Advancing Technologies | Often we introduce technology without knowing how it will influence the environment | Direct Harvesting | This has resulted in a large loss of rainforest and the many products associated with its biodiversity. | Pollution | Land, air, water, and nuclear pollution have had many adverse influences on ecosystems. | Atmospheric Changes | These include the addition of Greenhouse gases mostly due to the burning of fossil fuels and depletion of our stratospheric ozone layer. Other pollutants also have negative effects on living things. | | | |

Technological Developments | |

Technological Developments
Human technologies which degrade the environment result in a loss of diversity in the living and nonliving environment. Biodiversity refers to the differences in living things in an ecosystem.Many of our technologies and resource use practices have resulted in an irreversible loss of biodiversity.

Some examples of human activities which have negatively influenced other organisms include our land use practices and pollution. Excessive land use decreases the space and resources available to other species on the planet. Air, soil, and water pollution changes the composition of these environmental resources, making them harmful and unusable for other species and sometimes ourselves.

Endangered Species
Endangered species are those species which are threatened with destruction due to habitat destruction or other factors. Animals which were once endangered but are presently successfully reproducing and increasing their numbers are the bisons, gray wolves and egrets. Other endangered animals which are currently responding to conservation efforts and beginning to make a comeback are the whooping crane, bald eagle, and peregrine falcon. Even with these successes, the future of many endangered species remains in doubt.Exotic Species
The importation of some organisms have caused problems for native organisms. Organisms which are imported into an area from another region are called exotic species. Many examples of this are found world-wide. Some common examples of exotic species having negative effects would include the rabbits and deer which were imported into Australia. These exotic species won the competition with many native herbivorous marsupials and became nuisance species. The starling was brought into the United States from Europe. The starling has out competed many of our native songbirds. We also have alien invasive species which have caused problems in New York State. These include the plants such as the Water Chestnut, Eurasian Water milfoil, and Purple Loosestrife and animals such as the Alewife and Zebra Mussel. The Purple Loosestrife | | Purple loosestrife is a plant native to Europe. It was brought to North America in the early 1800's by immigrants who valued its beautiful purple flowers. It is now a serious pest of wetlands. Once purple loosestrife enters a wetland, it takes over. Common native wetland plants, such as cattails, cannot compete with purple loosestrife. Once these native plants are choked out, the wildlife that depends on them for food and shelter are also eliminated. |
Use of Fossil Fuels
Fossil fuels are becoming rapidly depleted. The use of these fuels are adding to out air pollution problems.The search and demand for additional fossil fuel resources also impact ecosystems in a negative way. Industrialization has brought an increased demand for and use of energy. One of the ways the increased burning of fossil fuels has had a harmful influence of the environment is by causing an increased incidence of acid precipitation. How does Acid Precipitation occur? | Most acid rain influencing New York State is caused by sulfur dioxide and nitrogen dioxide pollution from the burning of fossil fuels in the Western and Midwestern United States. These gases combine with water vapor in the atmosphere and fall back to the earth over New York and the Eastern United States as acid precipitation. | Some Problems Associated With Acid Precipitation | * Destruction of limestone and marble monuments due to increased chemical weathering * Acidification of aquatic ecosystems destroying the life in them * Damage forests and other plants in a variety of ways |
Our increased burning of fossil fuels and the release of excess carbon dioxide to the atmosphere associated with their combustion is also contributing to the Greenhouse Effect or global warming. It is believed the increase in level of carbon dioxide and some other gases is not allowing much infrared or heat radiation to escape the planet into outer space. This is causing our planet to slowly warm. The graphs in the table below show the link between increasing earth carbon dioxide levels and the increase in global average temperatures. Relationship Between
Global Temperature and Carbon Dioxide Levels | | | Some Consequences of Global Warming | * Rising sea levels and coastal flooding * Changed precipitation patterns which may result in droughts in some regions and increased levels of crop failure * An increase in insect borne diseases in temperate regions such as New York State as milder winters fail to kill the disease carrying insects. (The increase in the incidence of West Nile virus may be an example of this.) |
Ozone Depletion
CFC's (chloroflurocarbons) are very active chemicals associated with certain human manufacturing processes and products. This CFC pollution from refrigerants and plastics are destroying our thin ozone shield high up in our atmosphere or in the stratosphere. This layer of ozone normally shields us from excessive incoming ultraviolet radiation. Some consequences of this ever increasing ozone depletion appear to be an increased incidence of skin cancers and cataracts in the human population.Nuclear Energy
While nuclear energy avoids many of the pollution drawbacks associated with the increased burning of fossil fuels, there are many risks associated with the use of nuclear fuels for energy. Environmental dangers exist in reference to obtaining, using, and storing the wastes from these fuels. Many of the waste products of used nuclear fuel stay in the environment for thousands of years and release radiation which is harmful to humans or other living things. Additionally, the water used to cool many nuclear reactors must be released eventually to the environment. The thermal pollution associated with this released heat into the water is potentially dangerous to the aquatic life in the area where this hot water is released.Other Factors Influencing Environmental Quality
Many different factors besides industry and resource use have influences on environmental quality. Some factors include population growth and distribution, resource use, the capacity of technology to solve environmental problems, as well as economic, cultural, political, and ethical views. Some Examples of Political or Cultural Views Influencing Environmental Quality | * Wealthy people in the developed world tend to have fewer children. * Some countries like China have laws concerning the number of children a couple may have without penalty. * In some countries such as many in Latin America, families tend to be larger as birth control violates religious and societal norms. * In some poor cultures in third world countries, having many children is seen as a means of having economic security in old age. | |

IMPACT OF POPULATION GROWTH ON FOOD SUPPLIES AND ENVIRONMENT

As the world population continues to grow geometrically, great pressure is being placed on arable land, water, energy, and biological resources to provide an adequate supply of food while maintaining the integrity of our ecosystem. According to the World Bank and the United Nations, from 1 to 2 billion humans are now malnourished, indicating a combination of insufficient food, low incomes, and inadequate distribution of food. This is the largest number of hungry humans ever recorded in history. In China about 80 million are now malnourished and hungry. Based on current rates of increase, the world population is projected to double from roughly 6 billion to more than 12 billion in less than 50 years (Pimentel et al., 1994). As the world population expands, the food problem will become increasingly severe, conceivably with the numbers of malnourished reaching 3 billion. Based on their evaluations of available natural resources, scientists of the Royal Society and the U.S. National Academy of Sciences have issued a joint statement reinforcing the concern about the growing imbalance between the world's population and the resources that support human lives (RS and NAS, 1992).

Reports from the Food and Agricultural Organization of the United Nations, numerous other international organizations, and scientific research also confirm the existence of this serious food problem. For example, the per capita availability of world grains, which make up 80 per cent of the world's food, has been declining for the past 15 years (Kendall and Pimentel, 1994). Certainly with a quarter million people being added to the world population each day, the need for grains and all other food will reach unprecedented levels.
More than 99 per cent of the world's food supply comes from the land, while less than 1 per cent is from oceans and other aquatic habitats (Pimentel et al., 1994). The continued production of an adequate food supply is directly dependent on ample fertile land, fresh water, energy, plus the maintenance of biodiversity. As the human population grows, the requirements for these resources also grow. Even if these resources are never depleted, on a per capita basis they will decline significantly because they must be divided among more people.
At present, fertile cropland, is being lost at an alarming rate. For instance, nearly one-third of the world's cropland (1.5 billion hectares) has been abandoned during the past 40 years because erosion has made it unproductive (Pimentel et al., 1995). Solving erosion losses is a long-term problem: it takes 500 years to form 25 mm of soil under agricultural conditions.
Most replacement of eroded agricultural land is now coming from marginal and forest land. The pressure for agricultural land accounts for 60 to 80 percent of the world's deforestation. Despite such land replacement strategies, world cropland per capita has been declining and is now only 0.27 ha per capita; in China only 0.08 ha now is available. This is only 15 per cent of the 0.5 ha per capita considered minimal for a diverse diet similar to that of the U.S. and Europe. The shortage of productive cropland combined with decreasing land productivity is, in part, the cause of current food shortages and associated human malnutrition. Other factors such as political unrest, economic insecurity, and unequal food distribution patterns also contribute to food shortages.
Water is critical for all crops which require and transpire massive amounts of water during the growing season. For example, a hectare of corn will transpire more than 5 million liters of water during one growing season. This

means that more than 8 million liters of water per hectare must reach the crop. In total, agricultural production consumes more fresh water than any other human activity. Specifically, about 87 per cent of the world's fresh water is consumed or used up by agriculture and, thus, is not recoverable (Pimentel et al., 1996).
Competition for water resources among individuals, regions, and countries and associated human activities is already occurring with the current world population. About 40 percent of the world's people live in regions that directly compete for shared water resources. In China where more than 300 cities already are short of water, these shortages are intensifying. Worldwide, water shortages are reflected in the per capita decline in irrigation used for food production in all regions of the world during the past twenty years. Water resources, critical for irrigation, are under great stress as populous cities, states, and countries require and withdraw more water from rivers, lakes, and aquifers every year. A major threat to maintaining future water supplies is the continuing over-draft of surface and ground water resources.
Diseases associated with water rob people of health, nutrients, and livelihood. This problem is most serious in developing countries. For example, about 90 per cent of the diseases occurring in developing countries result from a lack of clean water (Pimentel et al., 1996). Worldwide, about 4 billion cases of disease are contracted from water and approximately 6 million deaths are caused by water-borne disease each year. When a person is ill with diarrhea, malaria, or other serious disease, anywhere from 5 to 20 percent of an individual's food intake offsets the stress of the disease.
Disease and malnutrition problems in the third world appear to be as serious in rural areas as they are in urban areas, especially among the poor. This will intensify in the future. Furthermore, the number of people living in urban areas is doubling every 10 to 20 years, creating major environmental problems, including water and air pollution and increased disease and food shortages.
Fossil energy is another prime resource used for food production. Nearly 80 per cent of the world's fossil energy used each year is used by the developed countries, and part of it is expended in producing high animal protein diets. The intensive farming technologies of developed countries use massive amounts of fossil energy for fertilizers, pesticides, irrigation, and for

machines as a substitute for human labor. In developing countries, fossil energy has been used primarily for fertilizers and irrigation to help maintain yields rather than to reduce human labor inputs (Giampietro and Pimentel, 1993).
Because fossil energy is a finite resource, its depletion accelerates as population needs for food and services escalate. The U.S. is already importing more than 50 per cent of its oil, and projections from the U.S. Department of Energy indicate that the country will exhaust all of its oil reserves within the next 15 to 20 years (Pimentel et al., 1994). Oil imports will then have to increase, worsening the U.S. trade imbalance. As supplies of fossil energy dwindle, the cost of fuel increases everywhere. The impact of this is already a serious problem for developing countries where the high price of imported fossil fuel makes it difficult, if not impossible, for poor farmers to power irrigation and provide for their other agricultural needs. Worldwide, per capita supplies of fossil energy show a significant decline.
In general, developing countries have been relying heavily on fossil energy, especially for fertilizers and irrigation to augment their food supply. The current decline in per capita use of fossil energy, caused by the gradual decline in oil supplies and their relatively high prices, is generating direct competition between developed and developing countries for fossil energy resources.
Economic analyses often overlook the biological and physical constraints that exist in all food production systems. The assumption is that market mechanisms and international trade are effective insurances against future food shortages. A rich economy is expected to guarantee a food supply adequate to meet a country's demand despite existing local ecological constraints. In fact, the contrary is true. When global biological and physical limits to domestic food production are reached, food importation will no longer be a viable option for any country. At that point, food importation for the rich can only be sustained by starvation of the powerless poor.
These concerns about the future are supported by two observations. First, most of the 183 nations of the world are now, to some extent, dependent on food imports. Most of these imports are cereal surpluses produced only in those countries that have relatively low population densities and practice intensive agriculture. For instance, the United States, Canada, Australia, Oceania, and Argentina provide 81 percent of net cereal exports on the

world market. If, as projected, the U.S. population doubles in the next 60 years (Pimentel et al., 1994), then its cereal and other food resources would have to be used domestically to feed 520 million hungry Americans. Then the U.S. would cease to be a food exporting country.
In the future, when exporting nations must keep surpluses at home, Egypt, Jordan, and countless other countries in Africa and Asia will be without the food imports that now help them survive. China, which now imports many tons of food, illustrates this problem. As the Worldwatch Institute has pointed out, if China's population increases by 500 million and their soil erosion continues unabated, it will need to import 200-400 million tons of food each year by 2050 (Brown, 1995). But by then, sufficient food imports probably will not be available on the international market.
Certainly improved technology will assist in more effective management and use of resources, but it cannot produce an unlimited flow of those vital natural resources that are the raw materials for sustained agricultural production. For instance, fertilizers enhance the fertility of eroded soils, but humans cannot make topsoil. Indeed, fertilizers made from finite fossil fuels are presently being used to compensate for eroded topsoil. Per capita fish catch has not increased even though the size and speed of fishing vessels has improved. On the contrary, per capita fish production is lower than ever before because greater efficiency led to overfishing. In regions like eastern Canada, overfishing has been so severe that cod fishermen have no fish to catch, and the economy of that region has been devastated. All of the world's fishing grounds are facing overfishing problems.
Consider also the supplies of fresh water that are available not only for agriculture but also for industry and public use. Water withdrawn from the Colorado River in several states for irrigation and other purposes results in the river being nearly dry by the time it reaches the Sea of Cortes, Mexico. No available technology can double the flow of the Colorado River, although effective water conservation would be a help. Similarly, the shrinking ground water resources stored in vast aquifers cannot be refilled by human technology. Rainfall is the only supplier.
A productive and sustainable agricultural system depends on maintaining the integrity of biodiversity. Often small in size, diverse species are natural enemies of pests, degrade wastes, form soil, fix nitrogen, pollinate crops, etc.

For example, in New York State on one bright, sunny day in July, the wild and other bees pollinate an estimated 6,000,000 million blossoms of essential fruits and vegetables. Humans have no technology to substitute for many of the services provided by diverse species in our environment.
Strategies for the future must be based first and foremost on the conservation and careful management of land, water, energy, and biological resources needed for food production. Our stewardship of world resources must change and the basic needs of people must be balanced with those resources that sustain human life. The conservation of these resources will require coordinated efforts and incentives from individuals and countries. Once these finite resources are exhausted they cannot be replaced by human technology. Further, more efficient and environmentally sound agricultural technologies must be developed and put into practice to support the continued productivity of agriculture.
Yet none of these measures will be sufficient to ensure adequate food supplies for future generations unless the growth in the human population is simultaneously curtailed. Several studies have confirmed that to maintain a relatively high standard of living, the optimum population should be less than 200 million for the U.S. and less than 2 billion for the world (Pimentel et al., 1994). This assumes that from now until an optimum population is achieved, strategies for the conservation of land, water, energy, and biological resources are successfully implemented and a sound, productive environment is protected. Improvements | |

Through a greater awareness of ecological principles and application of these principles to our natural environment, humans can help assure there will be suitable environments for succeeding generations of life on our planet.

Individuals in our societies will always have to make decisions on proposals involving the introduction of new technologies. Individuals in these societies need to make decisions which will assess the risks, benefits, trade-offs, and costs of these new technologies. The economic rewards of these technologies must be properly balanced with any adverse consequences these new technologies may have on the environment. It may be impossible to completely assess the consequences of introducing a new technology, but critical questions in reference to its introduction must be asked.

While the overall impact of humans on the planet's ecosystems have been negative, humans have done many things to improve the overall quality for living things in ecosystems we have damaged or destroyed. Activities having possible adverse effects on the environment in New York State are subject to review by SEQR (State Environmental Quality Review Act). Some other ways in which humans have attempted to minimize negative impacts or improve the ecosystems we are all a part of are listed in the table which follows. Some Positive Influences of Humans on the Ecosystem | * Sustaining endangered species by using habitat protection methods such as wildlife refuges and national parks. * Passing wildlife management laws, such as game laws and catch restrictions. * Adding lime to Adirondack lakes in an effort to neutralize their acid pollution so the original living things in these lakes can be reintroduced. * Design new products which meet basic needs without generating pollution. * Inspection of all materials before entering the country to prevent pest introduction. * Increased use of biodegradable packaging materials which will recycle themselves quickly to the environment. * Use fuels which contain less pollutants, such as low sulfur coal and oil. * Remove pollutants by using such devices as afterburners or catalytic converters before they enter the air. | |

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REFERENCE |

1. Internet :- * Wikipedia.com * Google.com * Four Spheres.com * Human Impact On Environment.com

2. Discovery Book 3. The Earth {Past, Present, Future} 4. Biology Book 5. Is our Environment safe ? 6. Visual Dictionary