Excellent study material for all civil services aspirants - being learning - Kar ke dikhayenge!
SHARE:
Environmental Geography
1.0 INTRODUCTION
Geography is a discipline committed to bridging the divide between the natural and physical sciences, on the one side, and the social sciences and humanities on the other. Environmental Geography represents attempts to understand the interrelationship between humans and the non-human world. Though the term 'environmental geography’ is less familiar than 'human' and 'physical' geography, it deserves greater recognition both within and beyond the discipline. Today there are many misconceptions pertaining to environmental geography. Environmental geography is often seen as the mid-point of a one-dimensional divide between human and physical geography. This tends to narrow down the definition of what Environmental Geography actually is. Environmental geography seeps into other disciplines and fields that share its interest in 'the geographical experiment' (and human environment interactions).
2.0 ECOLOGY AND ITS PRINCIPLES
In mid 19th century, Ernst Haeckel defined ecology as the study of the relationship of organisms with their environment. Since then other definitions of ecology have been proposed to reflect growth of the discipline, to found new specialties, or to mark out disciplinary territory.
Today, three definitions of ecology are considered to be widely acceptable. The first definition stems from the Haeckelian form – the study of the relationship between organisms and environment. The second definition, which is perhaps the most commonly repeated, considers ecology to be the study of the distribution and abundance of organisms. The third definition focuses ecology on the study of ecosystems. All these definitions have their limits and advantages.
Early ecologists recognised two major branches of ecology, animal ecology and plant ecology. With studies evolving and inter-relationships between various aspects of nature becoming more and more complex, many specialised branches of ecology have evolved. The chief among them are:
Human ecology: It involves population ecology or man and man’s relation to the environment, especially man's effects on the biosphere and the implication of these effects for man.
Applied ecology: It deals with the application of ecological concepts to human needs and thus, it includes following applications of ecology: wild-life management, range management, forestry, conservation, insect control, epidemiology, animal husbandry, aquaculture, agriculture, horticulture, and land use and pollution ecology.
Ecological genetics (geneecology): An ecologist recognized kind of genetic spasticity in the case of every organism. In any environment only those organisms that are favoured by the environment can survive. Thus, genecology deals with the study of variations of species based upon their genetic potentialities.
Palaeoecology: It is the study of environmental conditions, and life of the past ages, to which palynology, palaeontology, and radioactive dating methods have made significant contribution.
Space ecology: It is a modern subdivision of ecology which is concerned with the development of partially or completely regenerating ecosystems for supporting life of man during long space flights or during extended exploration of extra-terrestrial environments.
Radiation ecology: It deals with the study of gross effects of radiations and radioactive substances over the environment and living organisms.
Furthermore, ecology is often broadly divided into autecology and synecology. Autecology deals with the ecological study of one species of organism. Thus, an autecologist may study the life history, population dynamics, behaviour, home range and so on, of a single species, such as the Mexican free-tailed bat, Indian bull frog, or maize-borer Chilo partellus. Synecology deals with the ecological studies of communities or entire ecosystems.
The five basic concepts of ecology are:
- Diversity of living things: Plants and animals exist in a great variety of forms.They can be observed and classified by their structure and (for animals) behaviour. This diversity is the result of each type of plant or animal adapting to its environment in its own way.
- Interdependency of living things: All living things rely on and are affected by other living organisms and by non living features of their environments.
- Resource and energy cycles: The interactions among the members of an ecological community involve the exchange of energy and resources in continual cycles. Cycles are all driven by a constant flow of solar energy.
- Nested Systems: Networks of interdependent organisms exist within other larger networks (community to biosphere). Each network can be examined as a whole or as a part of a larger whole.
- Dynamic Balance: Each ecological network regulates and organizes itself by maintaining a state of dynamic balance characterized by continual fluctuations.
2.1 Human ecological adaptations
Cultural ecology studies how humans adapt to physical and social environments. Human adaptation refers to both biological and cultural processes that enable a population to survive and reproduce within a given or changing environment. Humans are tied to the environment by the way the gain their subsistence. Subsistence systems are often highly adapted to local conditions. The human body readily responds to changing environmental stresses in a variety of biological and cultural ways. We can acclimatize to a wide range of temperature and humidity. When traveling to high altitudes, our bodies adjust so that our cells still receive sufficient oxygen. We also are constantly responding in physiological ways to internal and external stresses such as bacterial and viral infections, air and water pollution, dietary imbalance, and overcrowding.
This ability to rapidly adapt to varying environmental conditions has made it possible for humans to survive in most regions of the world. Humans can live successfully in humid tropical forests, harsh deserts, arctic wastelands, and even densely populated cities with considerable amounts of pollution. Most other animal and plant species are restricted to one or relatively few environments by their more limited adaptability. Humans normally respond to environmental stresses in four ways:
- genetic change
- developmental adjustment
- acclimatization
- cultural practices and technology
If environmental stress is constant and lasts for many generations, successful adaptation to that stress develops. Those individuals who inherit a trait that offers an advantage in responding to particular stresses are more likely to survive longer and pass on more of their genes to the next generation. This is evolution through natural selection. For instance, people whose ancestors have lived in areas that have had endemic malaria often inherit some degree of immunity to this serious disease. The high incidence of sickle-cell trait among the people of Central Africa is largely the result of indirect selection for this trait by malaria. Genetic change in response to environmental stresses usually takes many generations to become widespread in a population. Humans have also developed other ways of responding more quickly as individuals during our own lifetime.
3.0 ECOSYSTEMS
An ecosystem is a core concept in biology and ecology and represents the level of biological organization in which organisms interact simultaneously with each other. It consists of the biological community that occurs in some locale, and the physical and chemical factors that make up its non-living or abiotic environment. The study of ecosystems mainly consists of the study of certain processes that link the living, or biotic, components to the non-living, or abiotic, components. Energy transformations and biogeochemical cycling are the main processes that comprise the field of ecosystem ecology.
3.1 Biotic and Abiotic Components of an Ecosystem
Biotic factors are living or once-living organisms in the ecosystem. These are obtained from the biosphere and are capable of reproduction. Examples of biotic factors are animals, birds, plants, fungi, and other similar organisms. Abiotic factors refer to non-living physical and chemical elements in the ecosystem. Abiotic resources are usually obtained from the lithosphere, atmosphere, and hydrosphere. Examples of abiotic factors are water, air, soil, sunlight, and minerals.
Abiotic factors affect the ability of organisms to survive and reproduce. Abiotic limiting factors restrict the growth of populations. They help determine the types and numbers of organisms able to exist within an environment.
Biotic factors are living things that directly or indirectly affect organisms within an environment. This includes the organisms themselves, other organisms, interactions between living organisms and even their waste. Other biotic factors include parasitism, disease, and predation (the act of one animal eating another).
On a larger scale, abiotic interactions refer to patterns such as climate and seasonality. Factors such as temperature, humidity and the presence or absence of seasons affect the ecosystem. For instance, some ecosystems experience cold winters with a lot of snow. An animal such as a fox within this ecosystem adapts to these abiotic factors by growing a thick, white-colored coat in the winter.
Decomposers such as bacteria and fungi are examples of biotic interactions on such a scale. Decomposers function by breaking down dead organisms. This process returns the basic components of the organisms to the soil, allowing them to be reused within that ecosystem.
Usually, biological communities include the "functional groupings" shown above. A functional group is a biological category composed of organisms that perform mostly the same kind of function in the system; for example, all the photosynthetic plants or primary producers form a functional group. Membership in the functional group does not depend very much on who the actual players (species) happen to be, only on what function they perform in the ecosystem.
3.2 Processes of Ecosystems
Ecosystems have energy flows and ecosystems cycle materials. These two processes are linked, but they are not quite the same.
Energy enters the biological system as light energy or photons. It is then transformed into chemical energy in organic molecules by cellular processes including photosynthesis and respiration, and ultimately is converted to heat energy. This energy is dissipated, meaning it is lost to the system as heat; once it is lost it cannot be recycled. Without the continued input of solar energy, biological systems would quickly shut down. Thus the earth is an open system with respect to energy. The transformations of energy in an ecosystem begin first with the input of energy from the sun. Energy from the sun is captured by the process of photosynthesis. Carbon dioxide is combined with hydrogen (derived from the splitting of water molecules) to produce carbohydrates (CHO). Energy is stored in the high energy bonds of adenosine triphosphate.
Elements such as carbon, nitrogen, or phosphorus enter living organisms in a variety of ways. Plants obtain elements from the surrounding atmosphere, water, or soils. Animals may also obtain elements directly from the physical environment, but usually they obtain these mainly as a consequence of consuming other organisms. These materials are transformed biochemically within the bodies of organisms, but sooner or later, due to excretion or decomposition, they are returned to an inorganic state. Often bacteria complete this process, through the process called decomposition or mineralization (see previous lecture on microbes).
During decomposition these materials are not destroyed or lost, so the earth is a closed system with respect to elements (with the exception of a meteorite entering the system now and then). The elements are cycled endlessly between their biotic and abiotic states within ecosystems. Those elements whose supply tends to limit biological activity are called nutrients.
In a typical food chain, energy from the sun, captured by plant photosynthesis, flows from trophic level to trophic level via the food chain. A trophic level is composed of organisms that make a living in the same way, that is they are all primary producers (plants), primary consumers (herbivores) or secondary consumers (carnivores). Dead tissue and waste products are produced at all levels. Scavengers, detritivores, and decomposers collectively account for the use of all such "waste" consumers of carcasses and fallen leaves may be other animals, such as crows and beetles, but ultimately it is the microbes that finish the job of decomposition. Not surprisingly, the amount of primary production varies a great deal from place to place, due to differences in the amount of solar radiation and the availability of nutrients and water.The organization of biological systems is much more complicated than can be represented by a simple "chain". There are many food links and chains in an ecosystem, and we refer to all of these linkages as a food web. Food webs can be very complicated, where it appears that "everything is connected to everything else", and it is important to understand what are the most important linkages in any particular food web.
3.3 Biogeochemistry
Linkages in a food web are generally understood by studying the flow of energy or the cycling of elements. The term Biogeochemistry is defined as the study of how living systems influence, and are controlled by, the geology and chemistry of the earth. Thus biogeochemistry encompasses many aspects of the abiotic and biotic world that we live in.
There are several main principles and tools that biogeochemists use to study earth systems. Most of the major environmental problems that we face in our world toady can be analyzed using biogeochemical principles and tools. These problems include global warming, acid rain, environmental pollution, and increasing greenhouse gases. The principles and tools that we use can be broken down into 3 major components: element ratios, mass balance, and element cycling.
Element ratios: In biological systems, we refer to important elements as "conservative". These elements are often nutrients. By "conservative" we mean that an organism can change only slightly the amount of these elements in their tissues if they are to remain in good health. It is easiest to think of these conservative elements in relation to other important elements in the organism. For example, in healthy algae the elements C, N, P, and Fe have the following ratio, called the Redfield ratio after the oceanographer who discovered it:
C : N : P : Fe = 106 : 16 : 1 : 0.01
Once we know these ratios, we can compare them to the ratios that we measure in a sample of algae to determine if the algae are lacking in one of these limiting nutrients.
Mass Balance: Another important tool that biogeochemists use is a simple mass balance equation to describe the state of a system. The system could be a snake, a tree, a lake, or the entire globe. Using a mass balance approach we can determine whether the system is changing and how fast it is changing. The equation is:
NET CHANGE = INPUT + OUTPUT + INTERNAL CHANGE
In this equation the net change in the system from one time period to another is determined by what the inputs are, what the outputs are, and what the internal change in the system was. The example given in class is of the acidification of a lake, considering the inputs and outputs and internal change of acid in the lake.
Element Cycling: Element cycling describes where and how fast elements move in a system. There are two general classes of systems that we can analyze, as mentioned above: closed and open systems.
A closed system refers to a system where the inputs and outputs are negligible compared to the internal changes. Examples of such systems would include a bottle, or our entire globe. There are two ways we can describe the cycling of materials within this closed system, either by looking at the rate of movement or at the pathways of movement.
Rate = number of cycles / time (as rate increases, productivity increases)
Pathways-important because of different reactions that may occur
In an open system there are inputs and outputs as well as the internal cycling. Thus we can describe the rates of movement and the pathways, just as we did for the closed system, but we can also define a new concept called the residence time. The residence time indicates how long on average an element remains within the system before leaving the system.
3.4 Controls on Ecosystem Function
The two dominant theories of the control of ecosystems are ‘bottom-up’ control and ‘top-down’ control. Bottom up control states that it is the nutrient supply to the primary producers that ultimately controls how ecosystems function. If the nutrient supply is increased, the resulting increase in production of autotrophs is propagated through the food web and all of the other trophic levels will respond to the increased availability of food (energy and materials will cycle faster).
According to the top down control, predation and grazing by higher trophic levels on lower trophic levels ultimately controls ecosystem function. If there is an increase in predators, that increase will result in fewer grazers, and that decrease in grazers will result in turn in more primary producers because fewer of them are being eaten by the grazers. Thus the control of population numbers and overall productivity "cascades" from the top levels of the food chain down to the bottom trophic levels.
Evidence from many ecosystem studies suggests that both controls are operating to some degree. The "top-down" effect is often very strong at trophic levels near to the top predators, but the control weakens as you move further down the food chain. Similarly, the "bottom-up" effect of adding nutrients usually stimulates primary production, but the stimulation of secondary production further up the food chain is less strong or is absent. Both of these controls are operating in any system at any time. The relative importance of each control needs to be understood so that an ecosystem change under different circumstances, such as in the face of a changing climate can be predicted and monitored.
3.5 Types of ecosystems
There are many different ecosystems: rain forests and tundra, coral reefs and ponds, grasslands and deserts. Climate differences from place to place largely determine the types of ecosystems we see. How terrestrial ecosystems appear to us is influenced mainly by the dominant vegetation.
The word "biome" is used to describe a major vegetation type such as tropical rain forest, grassland, tundra, etc., extending over a large geographic area. It is never used for aquatic systems, such as ponds or coral reefs. It always refers to a vegetation category that is dominant over a very large geographic scale, and so is somewhat broader than an ecosystem.
Temperature and rainfall patterns for a region are distinctive. Every place on earth gets the same total number of hours of sunlight each year, but not the same amount of heat. The sun's rays strike low latitudes directly but high latitudes obliquely. This uneven distribution of heat sets up not just temperature differences, but global wind and ocean currents that in turn have a great deal to do with where rainfall occurs. Add in the cooling effects of elevation and the effects of land masses on temperature and rainfall, and we get a complicated global pattern of climate.
Climate studies have been complicated due to increasing changes in the climate patterns. However many aspects are still predictable. High solar energy striking near the equator ensures nearly constant high temperatures and high rates of evaporation and plant transpiration. Warm air rises, cools, and sheds its moisture, creating just the conditions for a tropical rain forest. Every location has a rainfall- temperature graph that is typical of a broader region.
4.0 ECOLOGICAL BALANCE AND HUMAN IMPACT ON THE ECOSYSTEM
The processes of cyclic flow of material from abiotic environment to the biosphere and then back to the abiotic environment and upholding the equilibrium of interaction inside food webs are essential to maintain an ecological balance. Any interference with these cycles disrupts and affects ecological balance. The various ways in which ecological balance can be disturbed are:
Introduction of foreign species into an area: One way by which man affects the equilibrium of interaction in a food web is the entering of a foreign species into areas where there are no natural enemies like Predators, Parasites and Competitors. Due to lack of natural enemies the population of the new species grows into an uncontrollable number.
Removal of predator species: A disproportionate decline in the number of predator species interferes with the balance of interaction within a food web. A massive elimination of predators in the biotic community can disturb the prey population to elevate imbalance in density.
Killing snakes in the field may cause a rapid increase of rat population because deprivation of snake population and other predators of rats. Deforestation causes owls to migrate. Since owls are major rat predators, this will lead to the dramatic upsurge in rat population of the area. In Australia, overfishing of the Giant Triton causes death of coral reefs; this Giant Triton is a predator of the crown-fish-thorn starfish.
Introduction of synthetic products: Synthetic products are materials that are made by chemical processes that are formed artificially by chemical synthesis such as plastic bags, chairs, toys, etc. These synthetic materials can last for years and cannot be decomposed by decomposers. These synthetic products like different plastic products are made up of plastic; this creation of man hinders the flow of materials in the biosphere. Improper disposal of these products causes ecological imbalance. It destroys ecosystem that can kill the organism and at the same time it causes various problems in the living world such as pollution
Throwing toxic waste into the bodies of water: Because of the conversion of agricultural land into industrial estates or residential subdivisions more toxic waste are created by man. Industries uses chemicals in making their products and some industries are very irresponsible in disposing their waste. Some of them even release toxic waste in the bodies of water like rivers and lakes which leads to death of marine animals and microorganisms. A decrease of decomposers can cause delay of materials to return from the living to the nonliving environment.
Environmental issues: There are certain issues and problems that are related to ecological imbalance. These are problems that have evolved because of the disruption of ecological equilibrium. These problems can be classified into global problems, national problems and community problems.
Global problems - these are problems that affect different nations and can only be resolve through solidarity of affected nation. Some global problems are:
- Global warming or Greenhouse effect
- Acid Rain
- Pollution (Air and Marine Pollution)
- Depletion of ozone layer in the atmosphere
- Radioactive fallout because of nuclear war
National problems - these are problems that affect a country and can only be resolved within the country. These national environmental issues are:
Pollution (air, water and soil): Degradation of natural resources such as soil erosion, deforestation, depletion of wildlife, shortage of energy, degradation of marine ecosystems and depletion of mineral resources
Alteration and inconsistent land use like the conversion of agricultural land into industrial estates, conversion of mangrove swamps into fishponds and salt beds.
Community problems - these are problems that affect in a particular localities or communities and can only be resolve at in that exact level.
- Broken and not flowing drainage
- Stench damping site (Pollution)
- Widespread of epidemic in localities
5.0 MAJOR ECOSYSTEMS OF THE WORLD
In the world, there are several ecosystems working at macro or micro level. As pointed out earlier, the biosphere is the biggest ecosystem which combines all the ecosystems of the world.
Six major ecosystems of the world are as follows:
- Fresh Water Ecosystem
- Marine (Ocean) Ecosystem
- Grassland Ecosystem
- Forest Ecosystem
- Desert Ecosystem
- Cropland Ecosystem
But with the difference in physiographic, climate, natural vegetation, soil and water bodies, separate ecosystems have been developed.
Fresh Water Ecosystem: Fresh water habitats can be divided into two categories:
- Standing water or lentic (calm)-lake, pond, swamp or bog.
- Running water or lotic (washed)-river, spring, stream.
Although fresh water habitats occupy a small portion of the earth's surface, they are of great importance to humankind because they provide drinking water as well as water for domestic and industrial needs. Odum has defined fresh water ecology as: "Fresh water ecology emphasises the organisms in environment relationship in the freshwater habitat in the context of the ecosystem principle."
A pond is a good example of fresh water ecosystem, which exhibits a self-sufficient, self-regulating system. A pond is a place where living organisms not only live but also interact with abiotic and biotic components, thus forming an ecosystem which is different from other systems.
Similarly, lakes, swampy regions and delta regions of rivers have their own ecosystems in which producers, consumers and decomposers interact and are responsible for the unique ecosystem of each.
Marine (Ocean) Ecosystem: The marine ecosystem is different from fresh water ecosystem mainly because of its salty water and also because:
- The sea covers 70 per cent of earth's area,
- The sea is deep,
- The sea is continuous, and
- The sea water is in continuous circulation. According to Odum, "marine ecology emphasises the totality or pattern of relationship between organisms and the sea environment."
In a marine ecosystem, the ecology of shallow and deep waters as well as estuarine part is different from each other. Each ocean in itself represents a very large and stable ecosystem
Grassland Ecosystem: Grasslands occupy about 19 per cent of the earth's area, which include tropical and temperate grasslands. In this, the savannah ecosystem is very important.
The abiotic components are the nutrients present in the soil and aerial environment. The elements like carbon dioxide, water, nitrates, phosphates, sulfates, etc., are present in the air and soil of the area.
The producers are mainly grasses and small trees and shrubs. The primary consumers include cows, buffaloes, sheep, goats, deer, rabbits, and other animals, while secondary consumers are animals like foxes, jackals, snakes, frogs, lizards, birds, etc.
The microbes are active in the decaying and dead organic matter of different forms. They bring the minerals back to the soil, thus making them available to producers. Pastoralism and livestock ranching are the main occupations in these regions.
Forest Ecosystem: About 30 per cent of the land area of the earth is under forest cover, but due to man's intervention this area is gradually becoming smaller. But still forest ecosystem is very important.
The coniferous forests stretch as broad belts across North America and Eurasia. On the other hand, temperate deciduous forests occupy areas in eastern North America, parts of Europe, Japan and also in Australia. Among forests the tropical evergreen forests are found in the tropical regions.
In the forest ecosystem, the abiotic components are the organic substances present in the soil and atmosphere and also minerals present in dead organic debris. The producers are trees of different species.
The primary consumers are animals of various types, while secondary consumers include carnivores like lions, tigers, snakes, birds, Hazards, foxes, etc.
The forest ecosystems are of great concern from the environmental point of view. The rate of exploitation of forest by man is growing day by day, thus causing a great concern to all nations of the world because of its impact over global climate and on several animal species.
Desert Ecosystem: Deserts generally occur in regions having less than 25 cms of rainfall and are unevenly distributed.
Scarcity of rainfall may be due to:
- High sub-tropical pressure, as in the Sahara and Australian deserts,
- Geographical position in rain shadows, or
- High altitude as in Tibetan, Gobi, Bolivia deserts.
There are three life forms of plants that are adapted to deserts:
- The annuals, which avoid drought by growing only when there is adequate moisture,
- The succulents, such as the cacti, which store water, and
- The desert shrubs, which have numerous branches and a special root system which help them to adapt to desertic conditions.
The most common animals, apart from camels and goats, are reptiles and insects, able to live under xeric conditions. Due to poor vegetation, dead organic matter is less and some fungi and bacteria act as decomposers.
Apart from hot desert, there are also widespread cold deserts encircling the north and south poles, where permanent ice caps have developed an entirely different type of ecosystem, sustainable to cold climatic conditions.
Cropland Ecosystem: Apart from above mentioned natural ecosystems, there are also man-engineered ecosystems. One such ecosystem is the cropland ecosystem, in which man has developed croplands after considering the soil, climatic and other environmental conditions. These are ecosystems of dominant crop species like wheat, maize, jowar, paddy, sugarcane, cotton, tea, coffee, etc.
The abiotic components of this ecosystem include climatic conditions and mineral contents of the soil. In case of any deficiency man used chemical fertilizers and/or water for irrigation, etc. The various types of food grains, pulses and commercial crops are grown in these croplands, which provide food and fodder not only to man and animals, respectively, but in the fields several types of animals like birds, rats, rabbits, and other smaller reptiles insects, etc., also survive.
The decomposition of dead organic matter of plants and animals make the minerals available again. There is a need that every ecosystem should be studied in detail. Apart from above mentioned macro or global ecosystems, there are several meso and micro regions existing in each region.
For example, India has the following major ecosystems:
- Himalayan mountain ecosystem
- Plain ecosystem
- Desert ecosystem
- Central India plateau ecosystem
- Peninsular (Deccan plateau) ecosystem
- Coastal plain ecosystem
- Island ecosystem
These ecosystems have been identified on the basis of physiography, which also controls climate, natural vegetation, soil and also man's adoption to nature.
Each major region can be divided into sub-ecosystem regions; for example, Rajasthan has the following ecosystems:
- Arid ecosystem
- Irrigated arid ecosystem
- Sub-arid ecosystem
- Aravalli hills ecosystem
- Eastern plains ecosystem
- Hadoti plateau ecosystem
Further identification of micro-ecosystems will help not only in understanding the ecosystem but also in regional development and planning. The goal of sustainable development can only be achieved, when our developmental policies are based on the micro-ecosystem of each region.
COMMENTS