Chapter III

Chapter - III

Basic Ecological Principles

Components of Ecosystem: Biotic Components and Abiotic Components (with info-graphics)

The term ecosystem was coined by A.G. TansIey (1935) who stated the following words, “………………… the more fundamental conception is………….. the whole system (in the sense of physics), including not only the organism complex but also the whole complex of physical factors forming what we call the environment of the biome – the habitat factors in the widest sense.

Though the organisms may claim out primary interest, when we are trying to think fundamentally we cannot separate them from their special environment which they form one physical system. It is the systems so formed which…………………..are basic units of nature on the face of the earth……………….. The ecosystems as we may call them are of most various kinds and sizes”. Thus, the ecosystem can be of any size.

It has been observed that the green plants and some autotrophic bacteria are able to prepare their own food by utilizing solar radiant energy (light). They are capable of binding up the simple molecules of carbon-dioxide, water and other elements, such as, nitrogen, phosphorous, potassium, magnesium etc. by the help of light.

These substances are confined to the physical surroundings. Some animals (herbivores) eat plants directly and others (carnivores) eat such animals, which feed on the plants. Another group of organisms depends on the dead plants and animals to obtain their food from the decomposed tissues.

The food is digested and assimilated to synthesize different organic compounds from which the energy is derived for the life activities. The mechanism involves two distinct processes, firstly, the energy used by the plants passes through various organisms and finally it is lost as heat. The process has been referred as the ―flow of energy‖.

Secondly, along with energy, the substances also pass through the organisms but remain available for use, again and again. This process is known as biogeochemical cycling. These two

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Chapter III processes bind the organisms to their environment and the complex network is termed as the ecosystem.

An ecosystem in a laboratory may be as small as an aquarium. It may range from the size of a lake or forest to the size of the earth. Biosphere (W. Vernadsky 1929) or the Ecosphere (L.C. Cole, 1958) is the usual term which applies to the ecosystem that covers the whole of the earth. In fact, none of the ecosystems in independent, rather all are interdependent in some way or other.

All ecosystems consist of two major components—biotic and abiotic. The biotic component is comprised the living organisms, whereas the abiotic component includes the physical (non- living) environment. But, both of these components interact very closely to exhibit a definite structural organization. Sometimes, it is very difficult to separate the biotic components from the abiotic components.

Biotic Component:

When we consider the biotic components, the organisms are divided into two categories, the autotrophs and the heterotrophs. The autotrophs can produce their own food. They are the green plants with chlorophyll and certain types of bacteria—chemosynthetic and photosynthetic. Since these organisms produce food for all other organisms, they are also known as ‗Producer‘. The heterotrophs depend directly or indirectly on the autotrophs for their food. This type of organisms is further divided into two groups, such as, Photographs and Osmotrophs.

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The photographs take food from outside and digest it inside their bodies. They are called consumers. All animals—herbivores (plant eating), carnivores (animal eating) or omnivores (eating all kinds of food) fall in this group. The osmotrophs are those organisms who secrete digestive enzymes to break down the food into simpler substances and then absorb the digested food.

This group embraces the parasitic and saprophytic bacteria as well as the fungi. They may also be called Decomposers because their role has been well documented in the decomposition of the dead organic matter. But the most interesting point is that all of these parasites are not decomposers, rather some of them are consumers (insects and such small animals) who help in the decomposition by breaking down the dead organic matter into small bits. However, the heterotrophs can also be divided into two broad groups as the bio phages (feeding on living organisms) and the sarcophagus (feeding on dead organisms) Fig. 10.3.

The above mentioned divisions of organisms are principally based on the nature of food which in turn gives rise to the trophic structure of the ecosystem. It signifies a step-wise systematic relationships among the living organisms for food, which forms a chain, known as the food chain.

Some common food chains can be illustrated as follows:

(i) Grass ———–> goat———–>man

(ii) Seed———–>rat——— > cat———–>hawk

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(iii) Algae———–>zooplankton ———–> fish———–>man

(iv)Algae———–>insect———–> frog———–> snake———–>peacock

Such food chains can be traced back to the Producers and the position of the organism in the food chain is indicated by the trophic levels. This trophic level is defined as the number of links by which it is separated from the producer; the producers always belong to the first trophic level or the base.

A single species can operate more than one trophic level in the ecosystem which means that this species get its food from more than one source. Again, the same species may be eaten by several other species of a higher trophic level; thus, one can find out several food chains linked together in an intersecting manner to develop a network, known as food web. Such a network provides a clear- cut idea about the functioning of the ecosystem.

Abiotic Component:

Abiotic component of ecosystem refers to the physical environment and its several interacting variables which can be divided into four folds:

(i) Lithosphere which means the solid mineral matter on the earth and the land form as well;

(ii) Hydrosphere, i.e. the water in oceans, lakes, river, ice-caps, etc.;

(iii) Atmosphere, the gaseous mixture in the air; and

(iv) The radiant solar energy.

The position and movement of the earth with its gravitational force are additional components of the environment Fig. 10.4. However, these components create invariability of magnitude and duration of other environmental factors.

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The energy interacts with rocks, water and gases to produce a complex environment with a large number of identifiable variables such as heat, light, rain, wind, snow, fog, dust, storm, fire, etc. Thus, by the interaction of variables, the environment is created and maintained as a unit where any single component cannot be removed or altered without disturbing the other components.

Therefore, the environment is a dynamic whole, which remain continuously in a state of flux and also varies in space. The structural analysis of the environment in an ecosystem is urgently required to know the energy gradients and their flow.

Functionally the ecosystem allows the flow of energy and cycling of materials which ensures the stability of the system and continuity of life. The energy needed for all life processes come from solar radiation Fig. 10.5.

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During photosynthesis, green plants convert light energy to chemical (potential) energy and make it available to other organisms as food. Thus, a continuous flow of energy from sun through organisms maintains the life on earth. Laws of Thermodynamics govern on the transfer and transformation of energy.

It says, the energy can never be destroyed, but it is transformed into different forms. Therefore, the part of solar radiant energy that is not used in photosynthesis is used in heating of air, water and soil. So some change does occur in cyclic order of nature.

Ultimately the energy is reflected back to outer space as heat. In fact, a small fraction of available light energy is utilized during photosynthesis and a very little part is stored in animal tissues; the bulk is wasted as heat.

The next point is the ratio between the production and assimilation of energy. The small organisms utilize a large part of the assimilated energy for growth while larger organisms consume a larger part of the assimilated energy for maintenance of the organism (respiration). However, all these mechanisms-the transformation of energy, the food chain, the assimilation etc., are expressed as ecological efficiency.

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It is therefore clear that the two processes, namely the flow of energy and the cycling of materials are equally important for the functioning of ecosystem. These two processes are inseparable and run concurrently. As a consequence of interactions, a variety of organic substances are produced. This production is called biological production, which is essentially different from the chemical and industrial production. Biologists are interested in this production as it a part of a perpetual process.

In dealing with ecosystem, the concept of community is very important which can be defined as an assemblage of a number of organisms including man. The organisms include several species, which occupy the same habitat.

Even the micro-organisms are the part of a community. Here, ‗community‘ is essentially treated as a biotic component of the ecosystem. A population may also be defined

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Chapter III ecologically as a group of organisms of the same species occupying a particular space. However, population is the basic unit of the community—an aggregate of individuals of same species who mate among themselves.

Naturally the members live in a common area and like to use the same resources of the particular ecosystem. In this manner, by the way of interactions between the organism and its environment, each population develops a style of life, which is designated as the niche or ecological niche of the population.

The niche denotes a specific portion of the habitat occupied by each species. In 1917, J. Grinnell first brought this word. In 1927, C. Elton defined niche as an animal‘s place in the biotic environ-population in the community. In a simple way, it can be said that the habitat is the address of the species and the niche is its profession.

So, several populations with different functions may occupy the same habitat. The ecological niche is referred to the totality of biotic and abiotic factors to which a given population is uniquely adapted. The concept of niche was analyzed by R.H. Whittakar in 1970 as ―functional system of interacting niche differentiated species populations that tend to complement one-another rather than directly competing, in their utilization of the community‘s space, time, resources and possible kinds of interactions‖.

An important term fundamental to the concept of ecological niche is Biome. A biome is a biotic community characterized by distinct life forms of climax species. The climax species in an integrated unit which acts as an indicator of a specific climate.

The growth as well as life forms of climax populations suggests the result of interactions between the organisms and their environment. Though the climax species is a subject of controversial discussion, still each climatic zone represents some particular species as dominants.

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As a matter of fact, biome has been emphasized on the recognition and classification of natural biotic communities, which can be correlated, with the abiotic environment of that area. The other important concept, apart from Biome and Habitat, is the culture. Culture indicates a man-made environment is contrast to natural environment.

Man tends to develop an environment around him by invention as well as learning. The ecological niche appears by the interplay of the biome, habitat and culture. It keeps a harmonic balance between the biotic and abiotic components in the biosphere of ecosystem. (Fig. 10.7.)

As man is the most superior animal on the earth, he is able to manipulate his own environment. Sometimes he exploits the nature so severely that many life forms, beneficial to his survival are destroyed quite unknowingly. This disturbs the balance of the natural ecosystem and man faces odd consequences. For example, modem techniques of Agriculture and industrial development have brought adverse impact on ecosystem. Ecological niche An ecological niche is the role and position a species has in its environment; how it meets its needs for food and shelter, how it survives, and how it reproduces. A species' nicheincludes all of its interactions with the biotic and abiotic factors of its environment.

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Individuals' Ecological Niches

Every living thing on Earth has a role to play in its environment. In fact, you are filling a niche right now as you read this lesson. Whether you are a student, have a full time job, or are a mother or father, these are parts of the niche you fill. Your niche also includes where and how you obtain food and all of the things you do in order to survive.

If you closely look at a typical habitat in the environment, you will see many organisms living and working together, fulfilling their ecological niches. For example, imagine you are walking through the forest where there are leaves scattered on the ground and an old rotting log sitting on the forest floor. If you look closely, you could probably find earthworms just under the soil feeding on

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Chapter III decaying organic matter. There could also be centipedes eating small beetles and other organisms as well as a colony of ants that work and feed on dead insects. You may even find a couple of millipedes strolling around feeding on decaying leaves.

In this small section of the vast forest, all of these organisms are filling an individual ecological niche. To some degree, their niches may overlap, but if you look into all aspects of their lives, including where they live, how they survive, and how they reproduce, you will see that they are each truly individual niches. You could think of each ecological niche as parts of a puzzle that go together to make the environment successful.

What are autecology and synecology?

The study of the interactions between living things and their environments is known as ecology. In ecology, everything is connected to everything else and

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Chapter III there is a constant interaction between organisms and their environment. Autecology and Synecology Autecology & Synecology are two main branches of ecology. Autecology is the study of individual organism or individual species. It is also known as population ecology. Synecology is the study of group of organisms of different species which are associated together as a unit in form of a community. Also known as community ecology. Autecology helps us to understand the relationships between individual plants and environment. Synecology helps us to understand the relationships between communities and environment.

Importance of the hydrosphere

The primary importance of the hydrosphere is that it contains water, which sustains a variety of life forms and plays an important role in regulating the atmosphere and surrounding ecosystems. The hydrosphere includes all water located on the surface of the Earth. It contains freshwater, saltwater and frozen water as well, including groundwater and water in the lower levels of the atmosphere.

The water in the hydrosphere varies in texture and consistency, but shares the important function of sustaining human, plant, animal and bacterial life on Earth. Living organisms contain approximately 75 percent water. Cells within living beings rely on water to carry out important life functions. Water also allows cells to carry out critical chemical reactions, which otherwise would not happen, and therefore cause life to cease.

In addition to existing within organisms, water exists in habitats where plants and animals live. Water helps to regulate climates and atmospheric conditions and facilitates human activities, such as irrigation. The hydrosphere contains bodies of water around the world. Most of its composition derives from oceans, which have water trapped in layers of sedimentary rock. Oceans, lakes, rivers and ice include the main geographical features in

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Chapter III the hydrosphere, and exist in places around the world. Of these features, ice makes up the smallest portion of the hydrosphere, contributing only one percent to the total.

The hydrosphere provides an important place for the human beings and animals to live. There are also nutrients like the nitrate, nitrite, ammonium ions and other ions are dissolved in water. These substances is really needed for life to exist in water. The hydrosphere also helps the earth to regulate its temperature for the reason water takes a long time to heat up and a long time to cool down making the temperature of the earth stay within a range that is acceptable for life to exist. Humans and animals use water in a number of ways. Humans and animals uses water for drinking, which is essential to maintain life, and water is used for other purposes like washing, cleaning, and generating electricity through hydropower. If the hydrosphere or the so called water sphere is depleted or will totally vanish, there will be no more supply of water that is essential to maintain life and there will be no more human beings or even animals that will live in the planet earth. If the hydrosphere will vanish, the interaction between the hydrosphere and othere spheres of the earth like the litosphere, atmosphere and biosphere will be out of balance and will create disturbance or malfunction of the litosphere, atmosphere, and biosphere.

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Chapter III

Ecosystems: Concept, Structure and Functions of Ecosystems (with diagram)

Introduction - What is an Ecosystem?

An ecosystem 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. There are many examples of ecosystems -- a pond, a forest, an estuary, a grassland. The boundaries are not fixed in any objective way, although sometimes they seem obvious, as with the shoreline of a small pond. Usually the boundaries of an ecosystem are chosen for practical reasons having to do with the goals of the particular study.

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 andbiogeochemical cycling are the main processes that comprise the field of ecosystem ecology. As we learned earlier, ecology generally is defined as the interactions of organisms with one another and with the environment in which they occur. We can study ecology at the level of the individual, the population, the community, and the ecosystem.

Studies of individuals are concerned mostly about physiology, reproduction, development or behavior, and studies of populations usually focus on the habitat and resource needs of individual species, their group behaviors, population growth, and what limits their abundance or causes extinction. Studies of communities examine how populations of many species interact with one another, such as predators and their prey, or competitors that share common needs or resources.

In ecosystem ecology we put all of this together and, insofar as we can, we try to understand how the system operates as a whole. This means that, rather than worrying mainly about particular species, we try to focus on major functional aspects of the system. These functional aspects include such things as the amount of energy that is

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Chapter III produced by photosynthesis, how energy or materials flow along the many steps in a food chain, or what controls the rate of decomposition of materials or the rate at which nutrients are recycled in the system.

Components of an Ecosystem

You are already familiar with the parts of an ecosystem. You have learned about climate and soils from past lectures. From this course and from general knowledge, you have a basic understanding of the diversity of plants and animals, and how plants and animals and microbes obtain water, nutrients, and food. We can clarify the parts of an ecosystem by listing them under the headings "abiotic" and "biotic".

ABIOTIC COMPONENTS BIOTIC COMPONENTS Sunlight Primary producers Temperature Herbivores Precipitation Carnivores Water or moisture Omnivores

Soil or water chemistry (e.g., P, NH4+) Detritivores etc. etc. All of these vary over space/time

By and large, this set of environmental factors is important almost everywhere, in all ecosystems.

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

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Chapter III depend very much on who the actual players (species) happen to be, only on what function they perform in the ecosystem.

Processes of Ecosystems

This figure with the plants, zebra, lion, and so forth illustrates the two main ideas about how ecosystems function: ecosystems have energy flows and ecosystems cycle materials. These two processes are linked, but they are not quite the same (see Figure 1).

Figure 1. Energy flows and material cycles.

Energy enters the biological system as light energy, or photons, is 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

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Chapter III input of solar energy, biological systems would quickly shut down. Thus the earth is an open system with respect to energy.

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 callednutrients.

The Transformation of 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, or ATP (see lecture on photosynthesis).

The prophet Isaah said "all flesh is grass", earning him the title of first ecologist, because virtually all energy available to organisms originates in plants. Because it is the first step

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Chapter III in the production of energy for living things, it is called primary production (click here for a primer on photosynthesis). Herbivores obtain their energy by consuming plants or plant products,carnivores eat herbivores, and detritivores consume the droppings and carcasses of us all.

Figure 2 portrays a simple food chain, in which energy from the sun, captured by plant photosynthesis, flows fromtrophic 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.

For reasons that we will explore more fully in subsequent lectures, energy transfer through the food chain is inefficient. This means that less energy is available at the herbivore level than at the primary producer level, less yet at the carnivore level, and so

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Chapter III on. The result is a pyramid of energy, with important implications for understanding the quantity of life that can be supported.

Usually when we think of food chains we visualize green plants, herbivores, and so on. These are referred to asgrazer food chains, because living plants are directly consumed. In many circumstances the principal energy input is not green plants but dead organic matter. These are called detritus food chains. Examples include the forest floor or a woodland stream in a forested area, a salt marsh, and most obviously, the ocean floor in very deep areas where all sunlight is extinguished 1000's of meters above. In subsequent lectures we shall return to these important issues concerning energy flow.

Finally, although we have been talking about food chains, in reality 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.

Biogeochemistry

How can we study which of these linkages in a food web are most important? One obvious way is to study the flow of energy or the cycling of elements. For example, the cycling of elements is controlled in part by organisms, which store or transform elements, and in part by the chemistry and geology of the natural world. The term Biogeochemistry is defined as the study of how living systems influence, and are

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Chapter III 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.

1. 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 theRedfield 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.

2. 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:

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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.

3. 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.

1. Rate = number of cycles / time * as rate increases, productivity increases 2. 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.

1. Rate 2. Pathways 3. Residence time, Rt

Rt = total amount of matter / output rate of matter

(Note that the "units" in this calculation must cancel properly)

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Controls on Ecosystem Function

Now that we have learned something about how ecosystems are put together and how materials and energy flow through ecosystems, we can better address the question of "what controls ecosystem function"? There are two dominant theories of the control of ecosystems. The first, called 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).

The second theory, called top-down control, states that predation and grazing by higher trophic levels on lower trophic levels ultimately controls ecosystem function. For example, if you have 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.

So, which theory is correct? Well, as is often the case when there is a clear dichotomy to choose from, the answer lies somewhere in the middle. There is evidence from many ecosystem studies that BOTH controls are operating to some degree, but that NEITHER control is complete. For example, 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.

Thus we find that both of these controls are operating in any system at any time, and we must understand the relative importance of each control in order to help us to predict how an ecosystem will behave or change under different circumstances, such as in the face of a changing climate.

The Geography 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

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Chapter III 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 (Figure 3). 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.

Figure 3: The distribution of biomes.

We can draw upon previous lectures to remember that 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

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Chapter III 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.

A schematic view of the earth shows that, complicated though climate may be, many aspects are predictable (Figure 4). 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. Contrast the stable temperature but varying rainfall of a site in Panama with the relatively constant precipitation but seasonally changing temperature of a site in New York State. Every location has a rainfall- temperature graph that is typical of a broader region.

Figure 4. Climate patterns affect biome distributions.

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We can draw upon plant physiology to know that certain plants are distinctive of certain climates, creating the vegetation appearance that we call biomes. Note how well the distribution of biomes plots on the distribution of climates (Figure 5). Note also that some climates are impossible, at least on our planet. High precipitation is not possible at low temperatures -- there is not enough solar energy to power the water cycle, and most water is frozen and thus biologically unavailable throughout the year. The high tundra is as much a desert as is the Sahara.

Figure 5. The distribution of biomes related to temperature and precipitation.

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Types of Ecosystems

There are many types of ecosystems on earth. There are three major classes of ecosystems: 1. Fresh water Ecosystems 2. Terrestrial Ecosystems 3. Ocean Ecosystems

Examples of Ecosystems

Pond Ecosystem: In a pond, frogs, fishes, other tiny insects, several bacteria, fungi, algae with a variety of plants may be present. Some plants may float on water surface and some completely submerged in the water. Some water birds may be swimming on water surface. Fishes and frogs eat small insects. Small animals (insects etc) eat small plants.

The water plants need CO2 to prepare their food, this CO2 comes from the pond animals. During food preparation process plants give out oxygen, this oxygen is utilized by the pond animals. This form a pond ecosystem.

Forest Ecosystem: This includes inorganic and organic substances present in the atmosphere and soil. Tree and shrubs are also present in forest. There are small animals feeding on tree leaves these are ants, beetles, flies, spiders and grasshoppers. Different kinds of big animals and birds, snakes, lizards are also present in the forest. They all are inter-related with each other for food, energy, oxygen and other components which are essential for their survival and life processes.

Sea Ecosystem: In sea, we find so many types of plants and animals. Some plants and animals are very minute and some are very big. Green plants prepare food, these plants are eaten by the small animals and small animals are eaten by the huge animals. Their

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Chapter III main need is food, oxygen, carbon-dioxide and other life process components. They are inter-related with each other for their essential components for life process. How Ecosystem Affect Human Life

Every ecosystem has several interrelated mechanisms that affect human life. These are The Water Cycle, The Carbon Cycle, The Oxygen Cycle, The Nitrogen Cycle and The Energy Cycle. Every ecosystem is controlled by these cycles and each ecosystem‘s abiotic and biotic features are distinct from each other. All functions of the ecosystem are in some way related to the growth and re-generation of its plant and animal species.

The water cycle depends on the rainfall, which is necessary for plants and animals to live. Carbon is found in components of ecosystem and it is building block of both plant and animal tissues. In the atmosphere carbon occurs as CO2 .Plants help in regulating and monitoring the percentage of oxygen and carbon dioxide in the Earth‘s atmosphere. Both plants and animals release CO2 during respiration. They also return fixed carbon to the soil in the waste they excrete. When plants and animals die, they return their carbon to the soil. These processes complete the carbon cycle and the oxygen cycle.

In the nitrogen cycle, plants absorb nitrogen in the form of nutrients and use for their growth. Nutrients are re-cycle back from animals to plants.

The energy cycle re-cycle nutrients into the soil on which plant life grows.

Our own lives are closely linked to the proper functioning of these cycles of life.

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These cycles are a part of global life processes and have specific features in each of the ecosystems. They are also linked to adjacent ecosystems as well as plants and animals communities in the region. Together, the cycles are responsible for maintaining life on Earth. If human activities go on altering them beyond the limits that nature can sustain, they will eventually break down and lead to a degraded Earth on which man will not be able to survive.

Summary

Ecosystems are made up of abiotic (non-living, environmental) and biotic components, and these basic components are important to nearly all types of ecosystems. Ecosystem Ecology looks at energy transformations and biogeochemical cycling within ecosystems.

Energy is continually input into an ecosystem in the form of light energy, and some energy is lost with each transfer to a higher trophic level. Nutrients, on the other hand, are recycled within an ecosystem, and their supply normally limits biological activity. So, "energy flows, elements cycle".

Energy is moved through an ecosystem via a food web, which is made up of interlocking food chains. Energy is first captured by photosynthesis (primary production). The amount of primary production determines the amount of energy available to higher trophic levels.

The study of how chemical elements cycle through an ecosystem is termed biogeochemistry. A biogeochemical cycle can be expressed as a set of stores (pools) and transfers, and can be studied using the concepts of "stoichiometry", "mass balance", and "residence time".

Ecosystem function is controlled mainly by two processes, "top-down" and "bottom-up" controls.

A biome is a major vegetation type extending over a large area. Biome distributions are determined largely by temperature and precipitation patterns on the Earth's surface.

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Terrestrial and Aquatic Ecology/Ecosystem

It is not easy to compare terrestrial and aquatic systems because there is such a large variety of these environments. It is possible to recognize in the terrestrial part of the biosphere a small number of units with distinctive vegetation and climate, each with a complex of communities of large extent. These units are known as biomes and six major biomes are usually recognized, namely the:

 Tundra,  Taiga ( coniferous forests ),  Deciduous Forests,  Grasslands,  Tropical Rain Forests,  Deserts.

The Major Biomes of the World:

In this section we will focus on the similarities and differences between terrestrial and aquatic ecosystems.

Similarities between Terrestrial and Aquatic systems

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 in both terrestrial and aquatic environments the ecosystems include communities made up of a variety of species,  within both terrestrial and aquatic communities there are populations at the different trophic levels,  a great deal of mutual interdependence exists between species in both terrestrial and aquatic environments,  in undisturbed terrestrial and aquatic ecosystems equilibrium is reached, i.e. very few major changes are observed over a period of time,  in both ecosystems stratification (vertical zonation) occurs.

The Knysna forest in South Africa, an example A marine aquatic ecosystem of an terrestrial ecosystem.

Differences between Terrestrial and Aquatic systems

 because aquatic environments are so rich in nutrients they support more live than equivalent terrestrial ecosystems. The small drifting photosynthetic organisms of the oceans, referred to collectively as phytoplankton are regarded as the major photosynthesizers, or primary producers, of the earth,  aquatic environments are much more stable than terrestrial environments, with smaller fluctuations in temperature and other variables,  aquatic organisms are seldom exposed to desiccation while terrestrial organisms are often exposed to desiccation and are usually relatively resistant to drying out,

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 oxygen (because there is very much less present) is sometimes a limiting factor an aquatic habitats but this is seldom the case in terrestrial habitats,  light can be a limiting factor in some aquatic habitats, but in most terrestrial environments there is hardly ever a a shortage of light,  terrestrial animals are influenced far more by gravity, while water supports aquatic organisms.

Energy Flow Through Ecosystems

 Ecosystems maintain themselves by cycling energy and nutrients obtained from external sources. At the first trophic level, primary producers (plants, algae, and some bacteria) use solar energy to produce organic plant material through photosynthesis. Herbivores—animals that feed solely on plants—make up the second trophic level. Predators that eat herbivores comprise the third trophic level; if larger predators are present, they represent still higher trophic levels. Organisms that feed at several trophic levels (for example, grizzly bears that eat berries and salmon) are classified at the highest of the trophic levels at which they feed. Decomposers, which include bacteria, fungi, molds, worms, and insects, break down wastes and dead organisms and return nutrients to the soil.

 On average about 10 percent of net energy production at one trophic level is passed on to the next level. Processes that reduce the energy transferred between trophic levels include respiration, growth and reproduction, defecation, and nonpredatory death (organisms that die but are not eaten by consumers). The nutritional quality of material that is consumed also influences how efficiently energy is transferred, because consumers can convert high-quality food sources into new living tissue more efficiently than low-quality food sources.

 The low rate of energy transfer between trophic levels makes decomposers generally more important than producers in terms of energy flow. Decomposers process large amounts of organic material and return nutrients to the ecosystem in inorganic form, which are then taken up again by primary producers. Energy is not recycled during decomposition, but rather is released, mostly as heat (this is what makes compost piles and fresh garden mulch warm). Figure 6

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shows the flow of energy (dark arrows) and nutrients (light arrows) through ecosystems.

Figure 6. Energy and nutrient transfer through ecosystems

An ecosystem's gross primary productivity (GPP) is the total amount of organic matter that it produces through photosynthesis. Net primary productivity (NPP) describes the amount of energy that remains available for plant growth after subtracting the fraction that plants use for respiration. Productivity in land ecosystems generally rises with temperature up to about 30°C, after which it declines, and is positively correlated with moisture. On land primary productivity thus is highest in warm, wet zones in the tropics where tropical forest biomes are located. In contrast, desert scrub ecosystems have the lowest productivity because their climates are extremely hot and dry (Fig. 7).

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Figure 7. Terrestrial net primary productivity

In the oceans, light and nutrients are important controlling factors for productivity. As noted in Unit 3, "Oceans," light penetrates only into the uppermost level of the oceans, so photosynthesis occurs in surface and near- surface waters. Marine primary productivity is high near coastlines and other areas where upwelling brings nutrients to the surface, promoting plankton blooms. Runoff from land is also a source of nutrients in estuaries and along the continental shelves. Among aquatic ecosystems, algal beds and coral reefs have the highest net primary production, while the lowest rates occur in the open due to a lack of nutrients in the illuminated surface layers (Fig. 8).

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Figure 8. Ocean net primary productivity, 1997-2002 .

How many trophic levels can an ecosystem support? The answer depends on several factors, including the amount of energy entering the ecosystem, energy loss between trophic levels, and the form, structure, and physiology of organisms at each level. At higher trophic levels, predators generally are physically larger and are able to utilize a fraction of the energy that was produced at the level beneath them, so they have to forage over increasingly large areas to meet their caloric needs.

Because of these energy losses, most terrestrial ecosystems have no more than five trophic levels, and marine ecosystems generally have no more than seven. This difference between terrestrial and marine ecosystems is likely due to differences in the fundamental characteristics of land and marine primary organisms. In marine ecosystems, microscopic phytoplankton carry out most of the photosynthesis that occurs, while plants do most of this work on land. Phytoplankton are small organisms with extremely simple

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structures, so most of their primary production is consumed and used for energy by grazing organisms that feed on them. In contrast, a large fraction of the biomass that land plants produce, such as roots, trunks, and branches, cannot be used by herbivores for food, so proportionately less of the energy fixed through primary production travels up the food chain.

Growth rates may also be a factor. Phytoplankton are extremely small but grow very rapidly, so they support large populations of herbivores even though there may be fewer algae than herbivores at any given moment. In contrast, land plants may take years to reach maturity, so an average carbon atom spends a longer residence time at the primary producer level on land than it does in a marine ecosystem. In addition, locomotion costs are generally higher for terrestrial organisms compared to those in aquatic environments.

The simplest way to describe the flux of energy through ecosystems is as a food chain in which energy passes from one trophic level to the next, without factoring in more complex relationships between individual species. Some very simple ecosystems may consist of a food chain with only a few trophic levels. For example, the ecosystem of the remote wind-swept Taylor Valley in Antarctica consists mainly of bacteria and algae that are eaten by nematode worms (footnote 2). More commonly, however, producers and consumers are connected in intricate food webs with some consumers feeding at several trophic levels (Fig. 9).

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

Figure 9. Lake Michigan food web

An important consequence of the loss of energy between trophic levels is that contaminants collect in animal tissues—a process called bioaccumulation. As contaminants bioaccumulate up the food web, organisms at higher trophic levels can be threatened even if the pollutant is introduced to the environment in very small quantities.

The insecticide DDT, which was widely used in the United States from the 1940s through the 1960s, is a famous case of bioaccumulation. DDT built up in eagles and other raptors to levels high enough to affect their reproduction, causing the birds to lay thin-shelled eggs that broke in their nests. Fortunately, populations have rebounded over several decades since the pesticide was banned in the United States. However, problems persist in some developing countries where toxic bioaccumulating pesticides are still used.

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 Bioaccumulation can threaten humans as well as animals. For example, in the United States many federal and state agencies currently warn consumers to avoid or limit their consumption of large predatory fish that contain high levels of mercury, such as shark, swordfish, tilefish, and king mackerel, to avoid risking neurological damage and birth defects.

Biogeochemical Cycling in Ecosystems

Along with energy, water and several other chemical elements cycle through ecosystems and influence the rates at which organisms grow and reproduce. About 10 major nutrients and six trace nutrients are essential to all animals and plants, while others play important roles for selected species (footnote 3). The most important biogeochemical cycles affecting ecosystem health are the water, carbon, nitrogen, and phosphorus cycles.

As noted earlier, most of the Earth's area that is covered by water is ocean. In terms of volume, the oceans dominate further still: nearly all of Earth's water inventory is contained in the oceans (about 97 percent) or in ice caps and glaciers (about 2 percent), with the rest divided among groundwater, lakes, rivers, streams, soils, and the atmosphere. In addition, water moves very quickly through land ecosystems. These two factors mean that water's residence time in land ecosystems is generally short, on average one or two months as soil moisture, weeks or months in shallow groundwater, or up to six months as snow cover.

But land ecosystems process a lot of water: almost two-thirds of the water that falls on land as precipitation annually is transpired back into the atmosphere by plants, with the rest flowing into rivers and then to the oceans. Because cycling of water is central to the functioning of land ecosystems, changes that affect the hydrologic cycle are likely to have significant impacts on land ecosystems. (Global water cycling is discussed in more detail in Unit 8, "Water Resources.")

Both land and ocean ecosystems are important sinks for carbon, which is taken up by plants and algae during photosynthesis and fixed as plant tissue. Table 2 compares the quantities of carbon stored in Earth's major reservoirs.

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Table 2. Global carbon storage. Source: NOAA, www.pmel.noaa.gov/co2/gif/globcar.png. Location Amount (gigatons carbon) Atmosphere 750 Land plants 610 Soil and detritus 1,500 Surface ocean 1,020 Intermediate and deep ocean 37,890 Sediments 78,000,000

Carbon cycles relatively quickly through land and surface-ocean ecosystems, but may remain locked up in the deep oceans or in sediments for thousands of years. The average residence time that a molecule of carbon spends in a terrestrial ecosystem is about 17.5 years, although this varies widely depending on the type of ecosystem: carbon can be held in old-growth forests for hundreds of years, but its residence time in heavily grazed ecosystems where plants and soils are repeatedly turned over may be as short as a few months.

Human activities, particularly fossil fuel combustion, emit significant amounts of carbon each year over and above the natural carbon cycle. Currently, human activities generate about 7 billion tons of carbon per year, of which 3 billion tons remain in the atmosphere. The balance is taken up in roughly equal proportions by oceans and land ecosystems. Identifying which ecosystems are absorbing this extra carbon and why this uptake is occurring are pressing questions for ecologists.

Currently, it is not clear what mechanisms are responsible for high absorption of carbon by land ecosystems. One hypothesis suggests that higher atmospheric CO2 concentrations have increased the rates at which plants carry out photosynthesis

(so-called CO2 fertilization), but this idea is controversial. Controlled experiments have shown that elevated CO2 levels are only likely to produce short-term increases in plant growth, because plants soon exhaust available supplies of important nutrients such as nitrogen and phosphorus that also are essential for growth.

Nitrogen and phosphorus are two of the most essential mineral nutrients for all types of ecosystems and often limit growth if they are not available in sufficient

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Chapter III quantities. (This is why the basic ingredients in plant fertilizer are nitrogen, phosphorus, and potassium, commonly abbreviated as NPK.) A slightly expanded version of the basic equation for photosynthesis shows how plants use energy from the sun to turn nutrients and carbon into organic compounds:

CO2 + PO4 (phosphate) + NO3 (nitrate) + H2O → CH2O, P, N (organic tissue) + O2

Because atmospheric nitrogen (N2) is inert and cannot be used directly by most organisms, microorganisms that convert it into usable forms of nitrogen play central roles in the nitrogen cycle. So-called nitrogen-fixing bacteria take inert nitrogen (N2) from the atmosphere and convert it to ammonia (NH4) nitrate (NO3) and another nitrogen compounds, which in turn are taken up by plants. Some of these bacteria live in mutualistic relationships on the roots of plants, mainly legumes (peas and beans), and provide nitrogen directly to the plants; farmers often plant these crops to restore nitrogen to depleted soils. At the back end of the cycle, decomposers break down dead organisms and wastes, converting organic materials to inorganic nutrients. Other bacteria carry out denitrification, breaking down nitrate to gain oxygen and returning gaseous nitrogen to the atmosphere (Fig. 9).

Figure 10. The nitrogen cycle

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Human activities, including fossil fuel combustion, cultivation of nitrogen-fixing crops, and rising use of nitrogen fertilizer, are altering the natural nitrogen cycle. Together these activities add roughly as much nitrogen to terrestrial ecosystems each year as the amount fixed by natural processes; in other words, anthropogenic inputs are doubling annual nitrogen fixation in land ecosystems. The main effect of this extra nitrogen is over-fertilization of aquatic ecosystems. Excess nitrogen promotes algal blooms, which then deplete oxygen from the water when the algae die and decompose (for more details, see Unit 8, "Water Resources"). Additionally, airborne nitrogen emissions from fossil fuel combustion promote the formation of ground-level ozone, particulate emissions, and acid rain (for more details, see Unit 11, "Atmospheric Pollution").

Phosphorus, the other major plant nutrient, does not have a gaseous phase like carbon or nitrogen. As a result it cycles more slowly through the biosphere. Most phosphorus in soils occurs in forms that organisms cannot use directly, such as calcium and iron phosphate. Usable forms (mainly orthophosphate, or PO4) are produced mainly by decomposition of organic material, with a small contribution from weathering of rocks (Fig. 11).

Figure 11. The phosphorus cycle

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The amount of phosphate available to plants depends on soil pH. At low pH, phosphorus binds tightly to clay particles and is transformed into relatively insoluble forms containing iron and aluminum. At high pH, it is lost to other inaccessible forms containing calcium. As a result, the highest concentrations of available phosphate occur at soil pH values between 6 and 7. Thus soil pH is an important factor affecting soil fertility.

Excessive phosphorus can also contribute to over-fertilization and eutrophication of rivers and lakes. Human activities that increase phosphorus concentrations in natural ecosystems include fertilizer use, discharges from wastewater treatment plants, and use of phosphate detergents (for details, see Unit 8, "Water Resources").

Regulation of Ecosystem Functions

A key question for ecologists studying growth and productivity in ecosystems is which factors limit ecosystem activity. Availability of resources, such as light, water, and nutrients, is a key control on growth and reproduction. Some nutrients are used in specific ratios. For example, the ratio of nitrogen to phosphorus in the organic tissues of algae is about 16 to 1, so if the available nitrogen concentration is greater than 16 times the phosphorus concentration, then phosphorus will be the factor that limits growth; if it is less, then nitrogen will be limiting. To understand how a specific ecosystem functions, it thus is important to identify what factors limit ecosystem activity.

Resources influence ecosystem activity differently depending on whether they are essential, substitutable, or complementary. Essential resources limit growth independently of other levels: if the minimum quantity needed for growth is not available, then growth does not occur. In contrast, if two resources are substitutable, then population growth is limited by an appropriately weighted sum of the two resources in the environment. For example, glucose and fructose are substitutable food sources for many types of bacteria. Resources may also be complementary, which means that a small amount of one resource can substitute for a relatively large amount of another, or can be complementary over a specific range of conditions.

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Resource availability serves as a so-called "bottom-up" control on an ecosystem: the supply of energy and nutrients influences ecosystem activities at higher trophic levels by affecting the amount of energy that moves up the food chain. In some cases, ecosystems may be more strongly influenced by so-called "top-down" controls—namely, the abundance of organisms at high trophic levels in the ecosystem (Fig. 12). Both types of effects can be at work in an ecosystem at the same time, but how far bottom-up effects extend in the food web, and the extent to which the effects of trophic interactions at the top of the food web are felt through lower levels, vary over space and time and with the structure of the ecosystem.

Figure 12. Predators impose top-down control on ecosystems

Many ecological studies seek to measure whether bottom-up or top-down controls are more important in specific ecosystems because the answers can influence conservation and environmental protection strategies. For example, a study by Benjamin S. Halpern and others of food web controls in kelp forest ecosystems off the coast of Southern California found that variations in predator abundance explained a significant proportion of variations in the abundance of algae and the organisms at higher trophic levels that fed on algae and plankton. In contrast, they

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Chapter III found no significant relationship between primary production by algae and species abundance at higher trophic levels. The most influential predators included spiny lobster, Kellet's whelk, rockfish, and sea perch. Based on these findings, the authors concluded that "[e]fforts to control activities that affect higher trophic levels (such as fishing) will have far larger impacts on community dynamics than efforts to control, for example, nutrient input, except when these inputs are so great as to create anoxic (dead) zones" (footnote 4).

Drastic changes at the top of the food web can trigger trophic cascades, or domino effects that are felt through many lower trophic levels. The likelihood of a trophic cascade depends on the number of trophic levels in the ecosystem and the extent to which predators reduce the abundance of a trophic level to below their resource- limited carrying capacity. Some species are so important to an entire ecosystem that they are referred to as keystone species, connoting that they occupy an ecological niche that influences many other species. Removing or seriously impacting a keystone species produces major impacts throughout the ecosystem.

Many scientists believe that the reintroduction of wolves into Yellowstone National Park in 1995, after they had been eradicated from the park for decades through hunting, has caused a trophic cascade with results that are generally positive for the ecosystem. Wolves have sharply reduced the population of elk, allowing willows to grow back in many riparian areas where the elk had grazed the willows heavily. Healthier willows are attracting birds and small mammals in large numbers.

"Species, like riparian songbirds, insects, and in particular, rodents, have come back into these preferred habitat types, and other species are starting to respond," says biologist Robert Crabtree of the Yellowstone Ecological Research Center. "For example, fox and coyotes are moving into these areas because there's more prey for them. There's been an erupting trophic cascade in some of these lush riparian habitat sites."

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Ecological Niches

Within ecosystems, different species interact in different ways. These interactions can have positive, negative, or neutral impacts on the species involved (Table 4).

Table 4. Relationships between individuals of different species. Type of Effect of interaction Examples interaction Competition Both species are harmed Oak trees and maple trees competing for light in a (population growth rates are forest, wading birds foraging for food in a marsh reduced). Predation One species benefits, one is Predation: wolf and rabbit Parasitism harmed. Parasitism: flea and wolf Mutualism Both species benefit. Humans and house pets, insect pollination of flowers Relationship may not be essential for either. Commensalism One species benefits, one is Maggots decomposing a rotting carcass not affected. Amensalism One species harms another Allelopathy (plants that produce substances harmful (typically by releasing a toxic to other plants): rye and wheat suppress weeds when substance), but is not used as cover crops, broccoli residue suppresses affected itself. growth of other vegetables in the same plant family

Each species in an ecosystem occupies a niche, which comprises the sum total of its relationships with the biotic and abiotic elements of its environment—more simply, what it needs to survive. In a 1957 address, zoologist George Evelyn Hutchinson framed the view that most ecologists use today when he defined the niche as the intersection of all of the ranges of tolerance under which an organism can live (footnote 5). This approach makes ecological niches easier to quantify and analyze because they can be described as specific ranges of variables like temperature, latitude, and altitude. For example, the African Fish Eagle occupies a very similar ecological niche to the American Bald Eagle (Fig. 13). In practice it is hard to measure all of the variables that a species needs to survive, so descriptions of an organism's niche tend to focus on the most important limiting factors.

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Figure 13. African fish eagle

The full range of habitat types in which a species can exist and reproduce without any competition from other species is called its fundamental niche. The presence of other species means that few species live in such conditions. A species' realized niche can be thought of as its niche in practice—the range of habitat types from which it is not excluded by competing species. Realized niches are usually smaller than fundamental niches, since competitive interactions exclude species from at least some conditions under which they would otherwise grow. Species may occupy different realized niches in various locations if some constraint, such as a certain predator, is present in one area but not in another.

In a classic set of laboratory experiments, Russian biologist G.F. Gause showed the difference between fundamental and realized niches. Gause compared how two strains of Paramecium grew when they were cultured separately in the same type of medium to their growth rates when cultured together. When cultured separately both strains reproduced rapidly, which indicated that they were adapted to living and reproducing under the same conditions. But when they were cultured together,

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Chapter III one strain out-competed and eventually eliminated the other. From this work Gause developed a fundamental concept in community ecology: the competitive exclusion principle, which states that if two competitors try to occupy the same realized niche, one species will eliminate the other (footnote 6).

Many key questions about how species function in ecosystems can be answered by looking at their niches. Species with narrow niches tend to be specialists, relying on comparatively few food sources. As a result, they are highly sensitive to changes in key environmental conditions, such as water temperature in aquatic ecosystems. For example, pandas, which only eat bamboo, have a highly specialized diet. Many endangered species are threatened because they live or forage in particular habitats that have been lost or converted to other uses. One well-known case, the northern spotted owl lives in cavities of trees in old-growth forests (forests with trees that are more than 200 years old and have not been cut, pruned, or managed), but these forests have been heavily logged, reducing the owl's habitat.

In contrast, species with broad niches are generalists that can adapt to wider ranges of environmental conditions within their own lifetimes (i.e., not through evolution over generations, but rather through changes in their behavior or physiologic functioning) and survive on diverse types of prey. Coyotes once were found only on the Great Plains and in the western United States, but have spread through the eastern states in part because of their flexible lifestyle. They can kill and eat large, medium, or small prey, from deer to house cats, as well as other foods such as invertebrates and fruit, and can live in a range of habitats, from forests to open landscapes, farmland, and suburban neighborhoods (footnote 7).

Overlap between the niches of two species (more precisely, overlap between their resource use curves) causes the species to compete if resources are limited. One might expect to see species constantly dying off as a result, but in many cases competing species can coexist without either being eliminated. This happens through niche partitioning (also referred to as resource partitioning), in which two species divide a limiting resource such as light, food supply, or habitat.

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Evolution and Natural Selection in Ecosystems

As species interact, their relationships with competitors, predators, and prey contribute to natural selection and thus influence their evolution over many generations. To illustrate this concept, consider how evolution has influenced the factors that affect the foraging efficiency of predators. This includes the predator's search time (how long it takes to find prey), its handling time (how hard it has to work to catch and kill it), and its prey profitability (the ratio of energy gained to energy spent handling prey). Characteristics that help predators to find, catch, and kill prey will enhance their chances of surviving and reproducing. Similarly, prey will profit from attributes that help avoid detection and make organisms harder to handle or less biologically profitable to eat.

These common goals drive natural selection for a wide range of traits and behaviors, including:

 Mimicry by either predators or prey. A predator such as a praying mantis that blends in with surrounding plants is better able to surprise its target. However, many prey species also engage in mimicry, developing markings similar to those of unpalatable species so that predators avoid them. For example, harmless viceroy butterflies have similar coloration to monarch butterflies, which store toxins in their tissues, so predators avoid viceroy butterflies.  Optimal foraging strategies enable predators to obtain a maximum amount of net energy per unit of time spent foraging. Predators are more likely to survive and reproduce if they restrict their diets to prey that provide the most energy per unit of handling time and focus on areas that are rich with prey or that are close together. The Ideal Free Distribution model suggests that organisms that are able to move will distribute themselves according to the amount of food available, with higher concentrations of organisms located near higher concentrations of food (footnote 8). Many exceptions have been documented, but this theory is a good general predictor of animal behavior.  Avoidance/escape features help prey elude predators. These attributes may be behavioral patterns, such as animal herding or fish schooling to make individual organisms harder to pick out. Markings can confuse and disorient predators: for example, the automeris moth has false eye spots on its hind wings that misdirect predators (Fig. 14).  Features that increase handling time help to discourage predators. Spines serve this function for many plants and animals, and shells make crustaceans and mollusks harder to eat. Behaviors can also make prey harder to handle: squid and octopus emit clouds of ink that distract and confuse attackers, while hedgehogs and porcupines increase the

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effectiveness of their protective spines by rolling up in a ball to conceal their vulnerable underbellies.  Some plants and animals emit noxious chemical substances to make themselves less profitable as prey. These protective substances may be bad-tasting, antimicrobial, or toxic. Many species that use noxious substances as protection have evolved bright coloration that signals their identity to would-be predators—for example, the black and yellow coloration of bees, wasps, and yellowjackets. The substances may be generalist defenses that protect against a range of threats, or specialist compounds developed to ward off one major predator. Sometimes specialized predators are able overcome these noxious substances: for example, ragwort contains toxins that can poison horses and cattle grazing on it, but it is the exclusive food of cinnabar moth caterpillars. Ragwort toxin is stored in the caterpillars' bodies and eventually protects them as moths from being eaten by birds.

Figure 14. Automeris moth

Natural selection based on features that make predators and prey more likely to survive can generate predator-prey "arms races," with improvements in prey defenses triggering counter-improvements in predator attack tools and vice versa over many generations. Many cases of predator-prey arms races have been identified. One widely known case is bats' use of echolocation to find insects. Tiger

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Chapter III moths respond by emitting high-frequency clicks to "jam" bats' signals, but some bat species have overcome these measures through new techniques such as flying erratically to confuse moths or sending echolocation chirps at frequencies that moths cannot detect. This type of pattern involving two species that interact in important ways and evolve in a series of reciprocal genetic steps is called coevolution and represents an important factor in adaptation and the evolution of new biological species.

Other types of relationship, such as competition, also affect evolution and the characteristics of individual species. For example, if a species has an opportunity to move into a vacant niche, the shift may facilitate evolutionary changes over succeeding generations because the species plays a different ecological role in the new niche. By the early 20th century, large predators such as wolves and puma had been largely eliminated from the eastern United States. This has allowed coyotes, who compete with wolves where they are found together, to spread throughout urban, suburban, and rural habitats in the eastern states, including surprising locations such as Cape Cod in Massachusetts and Central Park in New York City. Research suggests that northeastern coyotes are slightly larger than their counterparts in western states, although it is not yet clear whether this is because the northeastern animals are hybridizing with wolves and domestic dogs or because they have adapted genetically to preying on larger species such as white-tailed deer.

Natural Ecosystem Change

Just as relationships between individual species are dynamic, so too is the overall makeup of ecosystems. The process by which one natural community changes into another over a time scale of years to centuries is called succession. Common succession patterns include plant colonization of sand dunes and the regrowth of forests on abandoned farmland (Fig. 15). While the general process is widely recognized, ecologists have offered differing views of what drives succession and how to define its end point. By analyzing the natural succession process, scientists seek to measure how stable ecosystems are at different stages in their trajectory of

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Chapter III development, and how they respond to disturbances in their physical environment or changes in the frequency at which they are disturbed.

Figure 15. Typical forest succession pattern

In the early 20th century, plant biologist Frederic Clements described two types of succession: primary (referring to colonization of a newly exposed landform, such as sand dunes or lava flows after a volcanic eruption) and secondary (describing the return of an area to its natural vegetation following a disturbance such as fire, treefall, or forest harvesting). British ecologist Arthur Tansley distinguished between autogenic succession—change driven by the inhabitants of an ecosystem, such as forests regrowing on abandoned agricultural fields—and allogenic succession, or change driven by new external geophysical conditions such as rising average temperatures resulting from global climate change.

As discussed above, ecologists often group species depending on whether they are better adapted for survival at low or high population densities (r-selected versus K- selected). Succession represents a natural transition from r- to K-selected species. Ecosystems that have recently experienced traumatic extinction events such as

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Chapter III floods or fires are favorable environments for r-selected species because these organisms, which are generalists and grow rapidly, can increase their populations in the absence of competition immediately after the event. Over time, however, they will be out-competed by K-selected species, which often derive a competitive advantage from the habitat modification that takes place during early stages of primary succession.

For example, when an abandoned agricultural field transitions back to forest, as seen in Figure 15, sun-tolerant weeds and herbs appear first, followed by dense shrubs like hawthorn and blackberry. After about a decade, birches and other small fast-growing trees move in, sprouting wherever the wind blows their lightweight seeds. In 30 to 40 years, slower-spreading trees like ash, red maple, and oak take root, followed by shade-tolerant trees such as beech and hemlock.

A common observation is that as ecosystems mature through successional stages, they tend to become more diverse and complex. The number of organisms and species increases and niches become narrower as competition for resources increases. Primary production rates and nutrient cycling may slow as energy moves through a longer sequence of trophic levels (Table 5).

Table 5. Characteristics of developing and mature ecosystems. Source: Drudy, W.H., and I.C.T. Nisbet, "Succession," Journal of the Arnold Arboretum, vol. 54 (1973), pp. 331-368; Odum and Barrett (2005), Fundamentals of Ecology, 5th Edition. Ecosystem attributes Developmental stages Mature stages Energetics: Production/respiration More or less than 1 Approaching 1 Production/biomass High Low Food chains Linear Web-like Community structure: Niches Broad Narrow Species diversity Low High Nutrient conservation Poor; detritus unimportant Good; detritus important Nutrient exchange rates Rapid Slow Stability Low High

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Many natural disturbances have interrupted the process of ecosystem succession throughout Earth's history, including natural climate fluctuations, the expansion and retreat of glaciers, and local factors such as fires and storms. An understanding of succession is central for conserving and restoring ecosystems because it identifies conditions that managers must create to bring an ecosystem back into its natural state. The Tallgrass Prairie National Preserve in Kansas, created in 1996 to protect 11,000 acres of prairie habitat, is an example of a conservation project that seeks to approximate natural ecosystem succession. A herd of grazing buffalo tramples on tree seedlings and digs up the ground, creating bare patches where new plants can grow, just as millions of buffalo maintained the grassland prairies that covered North America before European settlement

Chapter References:

Paul A. Colinvaux, Why Big Fierce Animals Are Rare: An Ecologist's Perspective (Princeton, NJ: Princeton University Press, 1979). A survey of major questions in ecology, including why every species has its own niche.

Chris Reiter and Gina C. Gould, "Thirteen Ways of Looking at a Hedgehog," Natural History, July/August 1998. Hedgehogs' spines are unique adaptations, but they have thrived in many regions for millions of years because they are generalists in terms of climate zones and diet.

ReefQuest Centre for Shark Research, "Catch As Catch Can," http://www.elasmo- research.org/education/topics/b_catch.htm. Contrary to their popular image as mindless eating machines, great white sharks' foraging strategies are selective and efficient.

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Major Terrestrial and Aquatic Biomes

Geography has a profound impact on ecosystems because global circulation patterns and climate zones set basic physical conditions for the organisms that inhabit a given area. The most important factors are temperature ranges, moisture availability, light, and nutrient availability, which together determine what types of life are most likely to flourish in specific regions and what environmental challenges they will face.

As discussed in Unit 2, "Atmosphere," and Unit 3, "Oceans," Earth is divided into distinct climate zones that are created by global circulation patterns. The tropics are the warmest, wettest regions of the globe, while subtropical high-pressure zones create dry zones at about 30° latitude north and south. Temperatures and precipitation are lowest at the poles. These conditions create biomes—broad geographic zones whose plants and animals are adapted to different climate patterns. Since temperature and precipitation vary by latitude, Earth's major terrestrial biomes are broad zones that stretch around the globe (Fig. 2). Each biome contains many ecosystems (smaller communities) made up of organisms adapted for life in their specific settings.

Figure 2. Earth's major land biomes

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Another way to visualize major land biomes is to compare them based on their average temperature ranges and rainfall levels, which shows how these variables combine to create a range of climates (Fig. 3).

Figure 3. Biome type in relation to temperature and rainfall Land biomes are typically named for their characteristic types of vegetation, which in turn influence what kinds of animals will live there. Soil characteristics also vary from one biome to another, depending on local climate and geology.

Table 1 compares some key characteristics of three of the forest biomes.

Forest type Temperature Precipitation Soil Flora

Tropical 20-25°C >200 cm/yr Acidic, low in Diverse (up to 100 nutrients species/km2)

Temperate -30 to 30°C 75-150 cm/yr Fertile, high in 3-4 tree species/km2 nutrients

Boreal Very low 40-100 cm/year, mostly Thin, low in nutrients, Evergreens (taiga) snow acidic

Aquatic biomes (marine and freshwater) cover three-quarters of the Earth's surface and include rivers, lakes, coral reefs, estuaries, and open ocean (Fig. 4). Oceans

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Chapter III account for almost all of this area. Large bodies of water (oceans and lakes) are stratified into layers: surface waters are warmest and contain most of the available light, but depend on mixing to bring up nutrients from deeper levels (for more details, see Unit 3, "Oceans"). The distribution of temperature, light, and nutrients set broad conditions for life in aquatic biomes in much the same way that climate and soils do for land biomes.

Marine and freshwater biomes change daily or seasonally. For example, in the intertidal zone where the oceans and land meet, areas are submerged and exposed as the tide moves in and out. During the winter months lakes and ponds can freeze over, and wetlands that are covered with water in late winter and spring can dry out during the summer months.

There are important differences between marine and freshwater biomes. The oceans occupy large continuous areas, while freshwater habitats vary in size from small ponds to lakes covering thousands of square kilometers. As a result, organisms that live in isolated and temporary freshwater environments must be adapted to a wide range of conditions and able to disperse between habitats when their conditions change or disappear.

Figure 4. Earth's marine and freshwater biomes

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Since biomes represent consistent sets of conditions for life, they will support similar kinds of organisms wherever they exist, although the species in the communities in different places may not be taxonomically related. For example, large areas of Africa, Australia, South America, and India are covered by savannas (grasslands with scattered trees). The various grasses, shrubs, and trees that grow on savannas all are generally adapted to hot climates with distinct rainy and dry seasons and periodic fires, although they may also have characteristics that make them well-suited to specific conditions in the areas where they appear.

Species are not uniformly spread among Earth's biomes. Tropical areas generally have more plant and animal biodiversity than high latitudes, measured in species richness (the total number of species present) (footnote 1). This pattern, known as the latitudinal biodiversity gradient, exists in marine, freshwater, and terrestrial ecosystems in both hemispheres. Figure 5 shows the gradient for plant species, but it also holds true for animals.

Figure 5. Plant species diversity

Source: Barthlott, W., Biedinger, N., Braun, G., Feig, F., Kier, G., and Mutke, J. (1999): Terminology and methodological aspects of the mapping and analysis of global diversity. Acta Botanica Fennica 162, 103–110.

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Why is biodiversity distributed in this way? Ecologists have proposed a number of explanations:

 Higher productivity in the tropics allows for more species;  The tropics were not severely affected by glaciation and thus have had more time for species to develop and adapt;  Environments are more stable and predictable in the tropics, with fairly constant temperatures and rainfall levels year-round;  More predators and pathogens limit competition in the tropics, which allows more species to coexist; and  Disturbances occur in the tropics at frequencies that promote high successional diversity.

Of these hypotheses, evidence is strongest for the proposition that a stable, predictable environment over time tends to produce larger numbers of species. For example, both tropical ecosystems on land and deep sea marine ecosystems— which are subject to much less physical fluctuation than other marine ecosystems, such as estuaries—have high species diversity. Predators that seek out specific target species may also play a role in maintaining species richness in the tropics.

Benefits of ecosystems

The interaction of living things depending on each other and relating to their environments has immense benefits in terms of the health and spiritual wellbeing of humans, the health of members of the ecosystem themselves, as well as the environment. Living things do not exist in isolation. They depend on abiotic factors too. The benefit of ecosystems therefore is not exclusive to living things. So, what is the role of ecosystems?

A. Supportive

Ecosystems provide a supporting role for all its members. In this role, living members serve as food for others, and their produce and residue serve as nutrients to soils and gases to the atmosphere. This makes soil nutrient cycle, carbon and oxygen cycle and water cycle possible and also for living things to continue procreation.

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B. Provision

Ecosystems are also the source of all foods, store of all energy, fibre, genetic resources, medicines, fresh water and minerals. All natural resources that humans depend on, has its source from ecosystems.

C. Regulation

The function of a healthy ecosystem ensures that there is balance and regulation in the climate, regulation in fresh water, soils, rocks, and atmosphere. They function to regulate animals and plant diseases and ensure that biodiversity is preserved.

D. Spiritual Value

Perhaps not exclusive to humans, ecosystems provide humans with deeper spiritual enrichment and cognitive development. The wonder and breathtaking properties of healthy ecosystems has recreational effects, as well as aesthetic value to us. From land the remotest places on earth to the deepest places in the oceans, there are millions of life forms that function in harmony, and provide humans with meditative and healing benefits.

Threats to Ecosystems

Anything that attempts to alter the balance of the ecosystem potentially threatens the health and existence of that ecosystem. Some of these threats are not overly worrying as they may be naturally resolved provided the natural conditions are restored. Other factors can destroy ecosystems and render all or some of its life forms extinct. Here are a few:

Habitat Destruction

Economic activities such as logging, mining, farming and construction often involve clearing out places with natural vegetative cover. Very often, tampering with one factor of the ecosystem can have a ripple effect on it and affect many more or all other factors of that ecosystem. For example, clearing a piece of forest

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Chapter III for timber can expose the upper layers of the soil to the sun's heat, causing erosion and drying. It can cause a lot of animals and insects that depended on the shade and moisture from the tree to die or migrate to other places.

Pollution

Water, land and air pollution all together play a crucial role in the health of ecosystems. Pollution may be natural or human caused, but regardless they potentially release destructive agents or chemicals (pollutants) into the environments of living things. ―In a lake, for example, it can create havoc on the ecological balance by stimulating plant growth and causing the death of fish due to suffocation resulting from lack of oxygen. The oxygen cycle will stop, and the polluted water will also affect the animals dependent on the lake water‖ Source: Study the effect of pollution on an ecosystem, WWF.

Eutrophication

This is the enrichment of water bodies with plant biomass as a result of continuous inflow of nutrients particularly nitrogen and phosphorus. Eutrophication of water fuels excessive plant and algae growth and also hurts water life, often resulting in

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Chapter III the loss of flora and fauna diversity. ―The known consequences of cultural eutrophication include blooms of blue-green algae (i.e., cyanobacteria, Figure 2), tainted drinking water supplies, degradation of recreational opportunities, and hypoxia. The estimated cost of damage mediated by eutrophication in the U.S. alone is approximately $2.2 billion annually (Dodds et al. 2009) Source: Eutrophication: Causes, Consequences, and Controls in Aquatic Ecosystems, Michael F. Chislock

Invasive species

Any foreign specie (biological) that finds its way into an ecosystem, either by natural or human introduction can have an effect on the ecosystem. If this alien has the ability to prey on vulnerable and native members of that ecosystem, they will be wiped out, sooner or later. One devastating impact of introducing alien Nile Perch and Nile Tilapia into Lake Victoria in the 1970s was the extinction of almost half of the 350+ endemic species of fish in the cichlid family.

Overharvesting

Fish species, game and special plants all do fall victim from time to time as a result of over harvesting or humans over dependence on them. Overharvesting leads to reduction in populations, community structures and distributions, with an overall reduction in recruitment. Lots of fish species are know to have reached their maximum exploitation level, and others will soon be. ―For example Oreochromis karongae is one of the most valuable food fishes in Malawi, but populations collapsed in the 1990s due to overfishing, and it is now assessed as Endangered.‖ Source: IUCN, Major Threats

UV Radiation

The sun‘s rays play an important role in living things. UV rays come in three main wavelengths: UVA, UVB and UVC, and they have different properties. UVA has long wavelengths and reaches the earth‘s surface all the time. It helps generate vitamin D for living things. UVB and UVC are more destructive and can cause DNA and cell damage

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Chapter III to plans and animals. Ozone depletion is one way that exposes living things to UVB and UVC and the harm caused can wipe lots of species, and affect ecosystems members including humans.

Preserving Ecosystems

Considering the threats facing ecosystems, we can begin to appreciate the importance of policy, rules and regulation in human activity towards ecosystems. Here are a few ways we can ensure the health and smooth functioning of ecosystems.

Habitat preservation

Economic activity should be managed and made sustainable. Tree cutting for example must be regulated and best practices enforced.

Invasive Species

In many of the tragedies that ecosystems have faced with the introduction of alien species, humans have caused that. It is crucial that proper inspection, regulation, research and monitoring systems are in place to protect weaker native species in ecosystems, if new species are to be introduced.

Eutrophication

One big cause of eutrophication is the runoff of surface chemicals and fertilizers applied to plants during farming. Whiles we need food to survive, it is important that we

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Chapter III encourage organic planting as against the heavy use of chemicals. Sewage also need to be inspected and monitored such that when the waste water is deposited into water bodies, it is properly filtered and treated to reduce the organic nutrient content.

Pollution

Air and land pollution together have effects on water bodies too. Acid rains and chemical runoff all affect life forms in the water. Oils that are discharged into water bodies can have a devastating effect. ―In aquatic ecosystems, air pollution acidifies surface waters, reducing their ability to sustain native fish. In estuaries and coastal waters, it contributes to nutrient over-enrichment, producing algal blooms, foul smells and low oxygen levels. It also causes mercury to accumulate in aquatic food webs, threatening the health of both people and wild animals2‖

Ozone

Ozone is a secondary pollutant. It is the result of the formation of precursors nitrogen oxides and Volatile Organic Compounds (VOC). Biomass burning produces this. It is known that forest cover act as a net sink of ozone. It is therefore important that we preserve natural vegetative covers on earth and invest in energy forms that reduce the emissions of VOCs.

What are the main threats to ecosystem/biodiversity?

 How are human activities affecting the amount of nitrogen in the environment?  How serious is the threat to biodiversity posed by invasive alien species?

FOCAL AREA | Addressing the major threats to biodiversity, including those arising from invasive alien species, climate change, pollution, and habitat change

Five main threats to biodiversity are commonly recognized in the programmes of work of the Convention: invasive alien species, climate change, nutrient loading and pollution, habitat change, and overexploitation. Unless we successfully mitigate the impacts of these direct drivers of change on biodiversity, they will contribute to the loss of biodiversity components, negatively affect ecosystem integrity and hamper aspirations towards sustainable use.

In discussing threats to biodiversity it is important to keep in mind that, behind these direct drivers of biodiversity loss, there are a number of indirect drivers that interact in complex ways to cause human-induced changes in biodiversity. They include

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Chapter III demographic, economic, socio-political, cultural, religious, scientific and technological factors, which influence human activities that directly impact on biodiversity.

Indicators for trends in nutrient loading and invasive alien species have been identified under the focal area addressed here, and are described below. Information on habitat change is provided by the indicator trends in extent of selected biomes, ecosystems and habitats. Overexploitation is discussed under the focal area on sustainable use. While there is no single indicator of the impacts of climate change on biodiversity, a number of indicators, including those on trends in extent of selected biomes, ecosystems and habitats (particularly applied to coral reefs, polar ice and glaciers, and certain types of forests and drylands), abundance and distribution of selected species, and incidence of human induced ecosystem failure, can serve to derive trends where specific data are available. Because small, fragmented ecosystems are more affected by changes in temperature and humidity than large contiguous ecosystems with a more balanced micro- climate, trends in connectivity/fragmentation of ecosystems provide an indicator of the vulnerability of ecosystems to climate change.

Case Study 1:

How are human activities affecting the amount of nitrogen in the environment:

HEADLINE INDICATOR Nitrogen deposition

The ability of agriculture to produce far greater quantities of food and fibre than ever before can be attributed to a number of factors, including the availability of fertilizers on a commercial scale. However, excessive levels of the plant nutrients nitrogen and phosphorus in natural ecosystems are now causing concern. While reactive nitrogen occurs naturally in all ecosystems, the production of reactive nitrogen by humans, mostly from manufacturing synthetic fertilizer to increase agricultural production, has changed ecological balances, both locally and in far-distant ecosystems. Anthropogenic production of reactive nitrogen leads to the release of nitrogen compounds into the atmosphere, which are subsequently deposited onto the biosphere. Aerial deposition of nitrogen increases levels in ecosystems such that those slow growing species that thrive in nitrogen-poor environments cannot compete with faster-growing species that depend on higher nutrient levels. Temperate grasslands are particularly vulnerable in this respect. Moreover, soluble nitrogen leaches from soils into groundwater, resulting in increased

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Chapter III eutrophication—excess nutrients in inland and coastal waters that stimulate excessive plant growth—algal blooms and the creation of anoxic (oxygen-free) zones in inshore marine areas.

Figure 2.15 Global trends in the creation of reactive nitrogen on Earth by human activity

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Figure 2.16 Estimated total reactive nitrogen deposition from the atmosphere (wet and dry) (early 1990s)

Anthropogenic sources of nitrogen—from the manufacturing of synthetic fertilizer, fossil fuel combustion and by nitrogen-fixing crops and trees in agroecosystems—now exceed natural terrestrial sources, such that more than half of all reactive nitrogen in ecosystems globally now comes from human sources. The rate of increase in the production of reactive nitrogen has accelerated sharply since 1960 (Figure 2.15). Atmospheric deposition currently accounts for about 12% of the reactive nitrogen entering terrestrial and coastal marine ecosystems globally, although in some regions, this percentage is much higher (Figure 2.16).

To continue to meet global demand for food and fibre and minimize environmental problems, significant improvements are required in the efficiency with which nitrogen fertilizer is utilized within production

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Chapter III systems. A 20% increase in nitrogen-use efficiency in the world’s cereal production systems would reduce the global production of reactive nitrogen by approximately 6% and lead to reduced expenditure for fertilizers equivalent to a value of about US$ 5 billion annually.

Case Study 2:

How serious is the threat to biodiversity posed by invasive alien species?

Invasive alien species can have devastating impacts on native biota, causing extinctions and affecting natural and cultivated ecosystems. Since the 17th century, invasive alien species have contributed to nearly 40% of all animal extinctions for which the cause is known. In the Fynbos biome of South Africa, 80% of the threatened species are endangered because of invading alien species.

A proportion of invasive alien species are important pests or pathogens that can cause enormous economic costs. The annual environmental losses caused by introduced pests in the United States, United Kingdom, Australia, South Africa, India and Brazil have been calculated at over US$ 100 billion. Invasive alien species can transform the structure and species composition of ecosystems by repressing or excluding native species. Because invasive species are often one of a whole suite of factors affecting particular sites or ecosystems, it is not always easy to determine the proportion of the impact that can be attributed to them. In the recent past, the rate and risk associated with alien species introductions have increased significantly because human population growth and human activities altering the environment have escalated rapidly, combined with the higher likelihood of species being spread as a result of increased travel, trade and tourism.

A major source of marine introductions of alien species is hull fouling and the release of ballast water from ships, although other vectors, such as aquaculture and aquarium releases, are also important and less well regulated than ballast water. In the marine ecosystem, the movement of non-native species has been well studied. Of the 150 species that have recently arrived in the Great Lakes, 75% originated from the Baltic Sea. Similarly, migration flow from the Red Sea to the Mediterranean through the Suez Canal

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Chapter III continues unabated with nearly 300 species of these Lessepsian migrants, including decapod crustaceans, molluscs and fishes, having entered the Mediterranean since 1891.

Equally long-term data available from five Nordic countries (Iceland, Denmark, Norway, Sweden and Finland) that have recorded the cumulative number of alien species in freshwater, marine and terrestrial environments since 1900 demonstrate the continuing arrival of new immigrants of plants, vertebrates and invertebrates (Figure 2.17).

Invasive alien species are a global problem requiring responses at all levels. Many countries have established systems to prevent and control invasive alien species and, as part of risk assessments, to predict the likelihood of alien species becoming invasive and the potential ecological and economic cost they may incur. To effectively communicate the challenges posed by invasive alien species there is a need to develop a methodology for integrating information quantifying the threat and its impacts on biodiversity into a coherent indicator.

Figure 2.17 Number of alien species recorded in the Nordic terrestrial, freshwater and marine environment

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Case 3:

How is the extent of forests and other ecosystems changing?

HEADLINE INDICATOR Trends in extent of selected biomes, ecosystems and habitats

Ecosystems are dynamic and complex assemblages of organisms that interact with each other and with the physical environment. Conversion, degradation, or the unsustainable management of a natural ecosystem has far-reaching consequences: it results in a change of the relative abundance of individual species, and frequently the loss of populations, and also in the reduction or loss of ecosystem services. Over the last 50 years, humans have changed ecosystems more rapidly and extensively than in any comparable period of time in human history. Reducing the rate at which ecosystems are being degraded or lost is therefore a key contribution towards the achievement of the 2010 Biodiversity Target.

For most of the world‘s main habitats and ecosystems, neither the current global extent nor rates of change in that extent are known with high certainty. This is due in part to the challenges of measuring global habitat extent, differences in definitions and classification systems and the lack of historical data. The exception is forests, many of which have direct commercial and/or scientific value, and are therefore regularly inventoried and assessed in most countries. Even here, however, there are limitations in analyses to date that make it difficult to assess, for example, changes in primary forests.

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Figure 2.1 Annual net change in forest area by region (1990–2005)

In the absence of human influence, forests and woodlands covered approximately half of the Earth‘s land surface. However, thousands of years of human activity have reduced their extent to about 30% of total land area. Of this area only one-third is considered primary forest—forest of native species where ecological processes are not significantly disturbed by human activities. Deforestation, mainly conversion of forests to agricultural land and pasture, continues at an alarmingly high rate: about 13 million hectares— equivalent to the area of Greece or Nicaragua—are lost each year. At the same time, tree planting, landscape restoration and natural expansion of forests have significantly offset the loss of primary forest area. It should be borne in mind, however, that the biodiversity value of forest plantations and secondary forests is generally much lower than that of forests. Figure 2.1 presents the trends in net forest area by region. The net loss in forest area in the period 2000–2005 is estimated at 7.3 million hectares per year, equivalent to an annual loss of 0.18% of net forest area. This compares to 8.9 million hectares (0.22%)

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Chapter III per year from the period 1990 to 2000. Over the last 15 years, primary forest has been lost or modified at a rate of approximately six million hectares a year.

Africa and South America continue to have the largest net loss of forests. Oceania and North and Central America also show a net loss of forests. The forest area in Europe continued to expand, although at a slower rate. Asia, which had a net loss in the 1990s, reported a net gain of forests in the period 2000–2005, primarily due to large-scale afforestation reported by China. There is recent evidence, however, of increases in the frequency and extent of natural disturbances (fire, insect outbreaks and disease) in boreal forests, which negatively affect forest cover in those ecosystems.

Achievement of the 2010 Biodiversity Target requires a significant reduction in the current rate of reduction of the extent of ecosystems. With regard to forests, a 20% reduction in the current rate of net loss of forest extent (7.3 million ha/yr lost between 2000 and 2005) would require limiting forest loss to 5.84 million ha/yr by 2010, while a 50% reduction would mean no more than 3.65 million ha/yr of forest loss. At the same time, efforts would need to focus on conserving natural forest area, rather than replacing natural forests with plantations of low biodiversity value.

Figure 2.2 Locations reported by various studies as undergoing high rates of change in forest cover in the past few decades

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On the basis of various studies from the period of 1980 to 2000, the Millennium Ecosystem Assessment prepared a map showing the areas undergoing high rates of change in forest cover (Figure 2.2)

Figure 2.3 Change in live coral cover across the Caribbean basin (1977-2002)

General patterns of change in the extent of ecosystems across other biomes besides forests show similar negative trends. The Millennium Ecosystem Assessment reported that almost 70% of Mediterranean forests, woodlands and scrub, 50% of tropical and sub- tropical grasslands, savannas and shrublands and 30% of desert ecosystems had been lost by 1990. Coastal and marine ecosystems have been heavily impacted by human activities, with degradation leading to a reduced coverage of kelp forests, seagrasses and corals. In the Caribbean, average hard coral cover declined from about 50% to 10% in the last three decades, equivalent to a loss of almost 7% of remaining area covered by live coral each year since the 1970s (Figure 2.3). Some 35% of mangroves have been lost in the last two decades in countries for which adequate data are available. This is equivalent to an annual loss of 2% of the remaining area. There has been a widespread retreat of mountain glaciers in non-polar regions during the 20thcentury, and decreases of about 10% in the extent of snow cover since the late 1960s. In the Arctic the average annual sea ice extent

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Chapter III has declined by about 8% in the past 30 years, with a loss of 15 to 20% in summer sea ice extent over the same period.

Case. 4 :

What proportion of species is threatened?

Threatened species occur across all taxonomic groups and in all parts of the world. Over the past few hundred years, it is estimated that humans have increased species extinction rates by as much as 1,000 times the background rates typical over Earth‘s history. Between 12% and 52% of species within well-studied higher taxa are threatened with extinction, according to the IUCN Red List of Threatened Species.

Figure 2.6 Red List Index for birds in marine, freshwater and terrestrial ecosystems, and in forest and shrubland/grassland habitats (1988-2004)

On the basis of Red List data, a Red List Index can be calculated for different taxonomic groups or geographic regions to show trends in the proportion of species expected to remain extant in the near future without additional conservation interventions. The index is based on the number of species present in each Red List category, and on the number that change categories over time (i.e., between assessments), as a result of genuine improvement or deterioration in status. This index shows a continuing deterioration in the

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Chapter III status of bird species, which have been completely assessed for the IUCN Red List four times over the last two decades, across all biomes (Figure 2.6). Despite limitations in our knowledge about the total number of species and their status, preliminary findings for other major groups, such as amphibians and mammals, indicate that the situation is likely worse than for birds.

The Red List Index is highly representative, being based on assessments of a high proportion of species in a taxonomic group across the world, but it shows a coarse level of resolution because of the width of the Red List categories. Some of the Red List criteria are based on absolute population size or range size, while others are based on rates of decline in these values or combinations of absolute size and rates of decline. Because the Red List Index is based on a proportional change in a measure and its values relate to the rate at which species are slipping towards extinction at particular points in time, a downward trend, even if becoming less steep, shows that the slide of the species towards extinction is accelerating, rather than slowing down. The 2010 Biodiversity Target would therefore only be met when a positive trend is achieved.

Landuse pattern and its importance

Land use pattern in India relates to the physical characteristics of land, the institutional and other resources framework like labour, capital available. All these aspects are associated with the economic development. India has a total land area of approximately 328 million hectares. Mostly, land utilisation statistics are obtainable for almost 93 % of the entire area that is around 306 million hectares. It is considerable to note that every forefather over the past 8,000 years or so have been successful in harbouring nearly 140 million hectares of land from the natural ecosystem to agriculture. From the time of independence, people have been successful to add another 22 million hectares. As a result, 162 million hectares of land excels as the net sown area at present. It forms a stupendous percentage of as high as 51%. No other large country is as fortunate as India in this regard.

Reporting and Non-Reporting Land

The land for which the data on classification of land-use is available is known as Reporting Land. In some cases the reporting land is that land, where the land use pattern figures are supported on land records and are based on village records or

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Chapter III papers. These records are preserved by village revenue agency and here the data is completely based on details of entire areas. In cases, where the records are not preserved, the estimates are mostly based on sample survey. Thus, the statistics of land use pattern are based on these two methods. On the other hand, the lands where no data is available are known as Non-Reporting Lands.

Uncultivated Land

According to the available land use statistics, there has been a slight increase in the net sown area. Almost 28 million hectares have been added over the passing few decades. Around 1.3 % of the land is under fruit trees. Nearly 5 % of the land falls in the category of uncultivated land which is cultivated once every 2 to 3 years. Thus, near about 51% of the whole area, on an average, is cultivated once a year. The uncultivated lands are subsidiary lands and are kept so to re-establish their richness. Its use depends upon high-quality and timely rains also.

Pastures and other Grazing Lands

The area separated as cultivable waste, has remained stationary at around 6.4 % for several decades. The land under permanent pastures is despondently low and suggests a remarkable population pressure on the land. Also, credit must be confirmed on the farmers that with so modest land under pastures, they have the biggest number of cattle. They are nurtured mainly on husk, grain chaff, farm waste and few fodder crops. This is definitely the most economical way to have a larger number of drought animals and bovine cattle. Areas that have been classed under forests are also used for cattle grazing.

Forested land in India is far less in scientific norm. For a self-sufficient economy and accurate ecological steadiness, at least one third of the total land area must be kept under forests and natural vegetation. In India, it is as low as 19.27%. Photographic proof, gained from satellites has confirmed that only about 46 million hectares come under real forests, as opposed to the estimated 63 million hectares, according to the

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Chapter III figures of land use pattern. However, this outline establishes a tiny rise from 40 million hectares.

Forest Lands It is important for the populace to ensure that they increase the area under forests for reasons more than one. A bigger area under forests is an obligation, to maintain the ecological balance and for absorption of carbon dioxide, the assemblage of which is likely to heighten the green house effect. This in turn would raise atmospheric temperature at the global stage. It may lead to thawing of ice caps and equivalent rise in sea level, jeopardising low-lying densely populated parts of the world. Forests supply home to wildlife and help their continuation. They help in enhancing the level of rainfall, minimising cases of famine. Forested lands also help in permeation of rainwater in the subsoil and modulating the flow of river waters in both rainy and dry seasons. Forests safeguard not only water but soil as well. They, thus, help in plunging the volume of floodwaters and their ferocity.

Wasteland A part of the land that is not utilised for the moment is classified as wasteland. This embraces the baked and rocky deserts. High mountainous and uneven lands also fall into this category. At times humankind has also been responsible to add to such areas by deforestation and overgrazing.

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Measures for proper Land Use

The mounting population and advanced standards of living have resulted in an ever increasing demand for residential land, both in villages and towns. Cities and towns are obligated to grow vertically rather than horizontally. Land is needed to develop industry, commerce, transport and recreational facilities. In view of mounting pressure on land for numerous purposes, it is customary to plan appropriate use of all the obtainable land. This may be done by following fitting measures to control soil erosion, desertification etc. which turns cultivatable land into wildernesses. In addition, some of the barrens may be brought around for different uses. Likewise, with the help of up-to- date and scientific methods of farming, productivity of land can also be amplified. All endeavours should be made to strike a balance amongst diverse use of land.

In India the capacity for expansion of cultivation to further new areas is very restricted. As of now, 49% of the entire reporting land is cultured. Fallow and other waste lands, including grazing pastures, which are not currently cultivated, is presumed around 42 million hectares, and further expansion of cultivation to such lands would be expensive

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Chapter III as improvements should be made on irrigation and water and soil conservation.

In the dynamic context, keeping in view the natural endowments and the recent advances in technology, the overall interests of a country may dictate a certain modification of or a change in the existing land-use pattern of a region. A proper study of the present land-use patterns and the developing trends will help to suggest the scope for planned shifts in the patterns in India.

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MACRO- AND MICROCLIMATE:

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Ecological Succession Defined

As you develop and grow there are certain predictable changes that will occur, and they usually happen in a specific order. As a baby, you first learn to roll over, then crawl, then walk. You also learn new skills such as how to feed yourself and how to talk, but each skill you learn builds on those learned before it. Your body also changes as you grow taller, your muscles and bones develop, your hair grows longer, etc.

Ecological succession is the same idea. It is the observed changes in an ecological community over time. These changes are fairly predictable and orderly. Within an ecological community, the species composition will change over time as some species become more prominent while others may fade out of existence. As the community develops over time, vegetation grows taller, and the community becomes more established. (Or)Ecological succession is the observed process of change in the species structure of an ecological community over time. The time scale can be decades (for example, after a wildfire), or even millions of years after a mass extinction.

Example: Succession of plant species on abandoned fields. Pioneer species consist of a variety of annual plants.

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About Ecological Succession:

For those unfamilire with the subject matter, there are two types of Ecological Succession. First there is Primary Succession and then there is Secondary Succession. The primary difference between the two types of succession lies in the oragins of the ground upon which the plants take root.

Primary succession takes place in the wake of a major catastrophic or geological disturbance where absolutely all of the plants in an area are distroyed. This is the kind of succession that could be observed hundreds of millions of years ago when the earth first came into beeing. Unfortunately, since this happened so long ago it is impossible for us to observe it in that setting today. We must instead settle for new souces from which to study examples in primary succession.

Such sources of major catastrophic or geological disturbance include things such as volcanic erruptions and glacial retreat. Some semi-local examples of primary succession, for me, include the aftermath of strip mining in the Lehigh Valley Gap in Whitehall, PA and glacial retreat at the Glacier National Park located in western Montana along the spine of the Rocky Mountains. Locations where primary succession can be observed today are few and far between.

Secondary succession, on the other hand, is a fairly common occurance. It takes place when a major disturbance occurs. Some examples of major disturbances are wild fires and deforestation which can be found all throughout the United States. With seccondary succession, all of the plants in an area are wiped out but they leave behind a seedbank from which they can be regrown once given favorable

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Chapter III enough conditions. Included in the following are the general processes of both primary and seccondary succession.

Primary Succession:

Primary succession is the development of an ecological community where one did not yet previously exist. It occurs in sources where bear rock has either been exposed or created by geological activity. It is upon this bear rock that lichens and algea take root in areas where some form of mositure content can be found. These areas include cracks in the rocks surface, small abrasions on the rock caused by the retreat of a glacer, poarus rocks which more easily absorb moisture, and rocks with shallow depressions where water condenses due to the lowering of tempertures in areas where the air has a high water molecule content.

These lichens and algea secrete digestive acids which help break down the rock's surface material for better nutrient absorption. These digestive acids help form tiny cracks in the rocks surface which are then widened over time as the mositure undergoes natural freezing and thawing processes. These cracks eventually grow large enough to trap enough organic materal and moisture for various moss species to take hold. These mosses also secrete digestive acids which assist in the breaking down of the rock's surface helping to form even larger cracks as they grow.

These cracks eventually collect enough soil to support grasses, flowers, and even small shrubs. Over time the roots of these plants burrow even further into the

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Chapter III cracks in the rock's surface. This allows the water to burrow further into the rock as well where it also freezes and thaws further widening the cracks in the rock. With the rooting of each new plant. the size of both the crack in the rock's surface and the size of the next plant able to take root there increases. They have a direct corrolation to each other. Eventually, several of the larger cracks form together creating a basin where trees can then take root. The eventual end result of primary succession is a climax community. However, it can often take hundreds, or in worse cases, even thousands of years for a climax community to become a reality.

Secondary Succession:

Secondary succession is the redevelopment of an ecological community where an ecological community has already previously existed but had since been wiped out for some reason or another. There are several primary causal sources of seccondary succession. These primary causal sources include things such as Lake Succession, Dune Succession, Fire Succession, Clear Cutting Succession, and Old Field Succession. For the general purpose of my assignment I am only going to go into detail about the proccess of Old Field Succession since this is the only one of the five which falls under the scope of my project.

While the strip of land in my back yard is not an old field, its environment has resulted from a churning of earth much like that which happens in a farmers field. Like the old field abandoned by the farmer, the strip of earth in my back yard has also been left to seed. In old fields, grasses are usually the first plants to take root. These plants are usually followed by low lying plants such as dandylions and other short flowering plants. As these cycle through taller plants such as milkweeds, goldenrods, and asters take root. These are then followed up by taller and taller plants.

The reason for this is due to the competition for light sources. Any new plants that want to take root can not be content to grow in the shadow of the plants that have come before it as it will not be able to undergo photosynthesis. Inorder to compeat for the light source it must be able to rise above and out distance the canopy of the shorter plants which would otherwise crowd it out. As the plants get taller they often become more woody inorder to combat gravity. This process eventually leads to the planting of shrubs and other small trees such as Sassafrases and Hawthornes.

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As the plants grow taller they have a tendency to shade out the shorter plants. These shorter plants will eventually die off leaving more space for taller plants which must breach the canopy of the medium sized plants that came before it. This escalating cycle eventually leads to the growth of larger trees such as Oaks, Maples, Hickories,and Beeches. As with primary succession, this proccess will eventually result in a mature forest, better known as a climax community. Also known as old growth forests, such communities have a layering of trees and shrubs in varying hights and sizes. Unlike the way it is with primary succession, if left to itself the secondary succession proccess does not usually take more than 75-150 years to become a climax community.

Types of Ecological Succession

Succession may be initiated either by formation of new habitat (landslide or lava flow) or disturbance of already existing habitat (fires, land clearance). There are three recognized stages to ecological succession. Each covers a gradual process of change and development. They do not have hard and defined boundaries, and it is possibly for an ecological system to be in both stages at once during the transition period from one to another. The 3 stages of ecological succession are:

1. Primary – This is when an ecological community first enters into a new form of habitat that it has not been present in before. A good example of this would be the habitat created when granite is removed in a quarry. The rock face that is left behind is altered and becomes a new habitat. The environment that then grows within that habitat is considered to be in its primary stage.

2. Secondary – The secondary succession stage occurs after a habitat has been established, but it is then disturbed or changed in some fashion and a new community moves in. To use the example from before – let us say that a primary stage develops on the face of a newly quarried granite cliff. That habitat grows undisturbed, until there is a forest fire that then burns and changes a portion of the habitat that has been growing on the rock face. That ecological habitat has now entered its secondary stage.

3. Climax – the climax stage is the last stage of an ecosystem. It is when the ecosystem has become balanced and there is little risk of an interfering event or change to mutate the environment. Several rainforests and deserts qualify as being in the climax stage. What is tricky about a climax stage is that given human development, any ecosystem that is in the climax stage now holds the risk of being destroyed and going backward in the stages.

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4 Stages of Ecological Succession

When talking about the types of ecological succession it is important to remember that the ―types‖ occur within the stages, but they may not necessarily be unique to that stage. What determines the stage that an ecosystem is in is dependent on its energy balance – which is discussed in the next section. There are four main types of ecological succession:

 Pioneer – pioneer types are the new lifeforms that enter into a primary succession and begin to take hold. This can be anything from a seed to a bacteria to an insect or to an animal wandering into a new area and bedding down to make it their home. The pioneer has no connection to the environment, but it does find enough present in the new ecosystem to begin to establish its life.

 Establishing – the establishing type can be hard to pinpoint because it crosses into the pioneer and sustaining. Establishing is the process in which lifeforms identify elements in an ecosystem that can sustain their basic needs – such as food, water and safe habitat.

 Sustaining – Sustaining type means that life in the ecosystem has begun to enter into a pattern that allows for a cycle of life to continue. This means that birth and death are occurring, and there is little migration outside of the ecosystem – this is most common in the climax succession.

 Producing – the producing type occurs during the secondary succession. This is when lifeforms are breeding and growing, but there is migration because what is produced is also not capable of being supported within the ecosystem. There are also more areas of overgrowth or overpopulation due to seed levels.

Pioneer species are the ones that thrive the new habitat at the beginning of ecological succession. Pioneer species are ‗r-selected‘ species that are fast growing and well- dispersed. Early succession is therefore dominated by so called ‗r-selected‘ species. As succession continues, more species enter the community and begin to alter the environment. These are called ‗k-selected‘ species. They are more competitive and fight for resource and space. The species that are better suited for the modified habitat then begin to succeed the other species. These are superseded by newer set of species. This goes on till the stage of climax or equilibrium is achieved.

When succession reaches a climax, where community is dominated by stable and small number of prominent species and no other species can be admitted, that is called the state of equilibrium or the climax community.

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Ecological Succession and Energy Balance

The climax stage of ecological succession is defined by the energy balance that is achieved. This means that within this very stable ecological system, there is a balance between the life that is produced, and the life that is consumed. For example, there are enough animals to eat the extra seeds to prevent overgrowth that could choke out plants, but not enough to prevent some of the seeds from growing and continuing their cycle of life. The climax stage is stable, but not static. During the other stages, the balance of energy is not in place and there may be crises that develop as a result which will prolong the secondary stage.

How Long Does Each Stage of Ecological Succession Take?

Each stage of ecological succession can take 100s to 1,000s of years – if not more. That is true, but only in a forensic sense. The assumption of ecological succession is that it is a forward moving, and linear path. As more of humankind encroaches on the natural world, the linear progression of this methodology is changing itself. That someone seems fitting for a theory that talks about the inevitability of change.

How is Mankind Changing Ecological Succession?

To best illustrate this, let us return to our first example – the rock face. Let us suppose that the granite wall was quarried by man, and then abandoned once they had what they needed. This allows for a primary stage to begin. Left alone by man, it could quickly pass into a secondary stage within a hundred years or so. Another few centuries after that, the old quarry is slowly entering its stable climax stage – except – now man has returned to build a road. One thing that ecological succession recognizes is the death of an ecosystem. That is what occurs when a climax stage ecosystem like the rain forest is destroyed by logging. Yet when a climax stage ecosystem is only interrupted, it is not yet understood whether it returns to the secondary stage, or would still be considered at its climax of ecological succession.

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Bioindicators

Introduction

Bioindicators are organisms, such as lichens,birds and bacteria, that are used to monitor the health of the environment. The organisms and organism associations are monitored for changes that may indicate a problem within their ecosystem. The changes can be chemical, physiological or behavioural.

What can the canary in the coal mine tell us? Historically, canaries accompanied coal miners deep underground. Their small lung capacity and unidirectional lung ventilation system made them more vulnerable to small concentrations of carbon monoxide and methane gas than their human companions. As late as 1986, the acute sensitivity of these birds served as a biological indicator of unsafe conditions in underground coal mines in the United Kingdom. Since human health concerns continue to drive the development and application of bioindicators, the loss of ecosystem services (e.g., clean air, drinking water, plant pollinators) has increasingly focused our attention on the health of natural ecosystems. All species (or species assemblages) tolerate a limited range of chemical, physical, and biological conditions, which we can use to evaluate environmental quality. Despite many technological advances, we find ourselves turning to the biota of natural ecosystems to tell us the story of our world.

Red areas represent portions of an environmental gradient (e.g., light availability, nitrogen levels) where an individual, species, or community, has fitness or abundance greater than zero. The dashed line represents the peak performance along this particular environmental gradient, while yellow boxes include the optimum range or tolerance. Bioindicators possess a moderate tolerance to environmental variability, compared to rare and ubiquitous species. This tolerance affords them sensitivity to indicate environmental change, yet endurance to withstand some variability and reflect the general biotic response.

Bioindicators include biological processes, species, or communities and are used to assess the quality of the environment and how it changes over time. Changes in the environment are often attributed to anthropogenic disturbances (e.g., pollution, land use changes) or natural stressors (e.g., drought, late spring freeze), although anthropogenic stressors form the primary focus of bioindicator research. The widespread development and application of bioindicators has occurred primarily since the 1960s. Over the years, we have expanded our repertoire of bioindicators to assist us in studying all types of environments (i.e., aquatic and terrestrial), using all major taxonomic groups.

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Figure 1: Comparison of environmental tolerances of (a) bioindicators, (b) rare species, and (c) ubiquitous species

However, not all biological processes, species, or communities can serve as successful bioindicators. Physical, chemical, and biological factors (e.g., substrate, light, temperature, competition) vary among environments. Over time, populations evolve strategies to maximize growth and reproduction (i.e., fitness) within a specific range of environmental factors. Outside an individual's environmental optima, or tolerance range, its physiology and/or behavior may be negatively affected, reducing its overall fitness (Figure 1). Reduced fitness can subsequently disrupt population dynamics and alter the community as a whole (Figure 2). Bioindicator species effectively indicate the condition of the environment because of their moderate tolerance to environmental variability (Figure 1). In contrast, rare species (or species assemblages) with narrow tolerances are

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Chapter III often too sensitive to environmental change, or too infrequently encountered, to reflect the general biotic response. Likewise, ubiquitous species (or species assemblages) with very broad tolerances are less sensitive to environmental changes which otherwise disturb the rest of the community. The use of bioindicators, however, is not just restricted to a single species with a limited environmental tolerance. Entire communities, encompassing a broad range of environmental tolerances, can serve as bioindicators and represent multiple sources of data to assess environmental condition in a "biotic index" or "multimetric" approach.

Furthermore, biological processes within an individual can act as bioindicators. For example, cutthroat trout inhabit coldwater streams of the western United States. Most individuals have an upper thermal tolerance of 20°–25°C; thus, their temperature sensitivity can be used as a bioindicator of water temperature. Livestock grazing, burning, and logging are examples of human-related disturbances that can increase water temperature in these streams and be detected by cutthroat trout at various biological scales (Figure 2). An immediate response of cutthroat to thermal pollution occurs at the cellular level. Specifically, heat shock protein (hsp) synthesis increases to protect vital cellular functions from thermal stress. We can quantify hsp levels to measure thermal stress in cutthroat trout and assess how the environment has been altered. If thermal stress persists, such physiological changes are generally tractable at the individual level through behavioral changes and subsequent reductions in growth and development. In the most extreme instances, however, large and persistent thermal alterations can reduce population numbers and even lead to local extinctions, causing compositional shifts to warm water fisheries.

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Figure 2: Diagram of the hierarchical levels of an ecosystem that respond to anthropogenic disturbances or natural stress The white ring of environmental variables includes factors that may be directly altered by disturbance or stress. These alterations may subsequently affect individual organisms, populations, or the community as a whole. The outermost colored ring represents individual organisms (cutthroat trout, Pteronarcys Salmonfly, Phaedoactylum diatom), the middle colored ring represents populations of those organisms, and the innermost colored ring represents the community in which all three species coexist. Disturbance and stress may positively or negatively affect energy resources (e.g., food, light), biotic interactions (e.g., competition, predation, herbivory), and the physical (e.g., water velocity, substrate upon which an organism attaches, uses for refugia, lays eggs), or chemical (e.g., nutrients) environment. These environmental changes may increase or decrease growth and reproduction of an organism, consequently impacting the size and productivity of the population and interactions with other species in the community. Isn't it Called Biomonitoring?

In common usage, the terms "biomonitoring" and "bioindication" are interchangeable, but in the scientific community these terms have more specific meanings. Bioindicators qualitatively assesses biotic responses to environmental stress (e.g., presence of the

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Chapter III lichen, Lecanora conizaeoides, indicates poor air quality) while biomonitors quantitatively determine a response (e.g., reductions in lichen chlorophyll content or diversity indicates the presence and severity of air pollution). Hereafter, the term "bioindicator" is used as a collective term to refer to all terms relating to the detection of biotic responses to environmental stress. Within this framework, there are three main functions of bioindicators: 1. to monitor the environment (i.e., physical and/or chemical changes), 2. to monitor ecological processes, or 3. to monitor biodiversity.

Examples of environmental, ecological, and biodiversity indicators can be found in many different organisms inhabiting many different environments. Lichens (a symbiosis among fungi, algae, and/or cyanobacteria) and bryophytes (mosses and liverworts) are often used to assess air pollution. Lichens and bryophytes serve as effective bioindicators of air quality because they have no roots, no cuticle, and acquire all their nutrients from direct exposure to the atmosphere. Their high surface area to volume ratio further encourages the interception and accumulation of contaminants from the air.

Figure 3: Relationship of elemental concentration within moss tissue (inset is Hylocomium splendens) to distance from the road in Alaska, USA

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Each element is represented by a different set of colored dots (red, Aluminum; yellow, Zinc; green, Lead; blue, Cadmium). The greatest concentration of each element occurred close to the road and declined with distance from the road, demonstrating a marked impact of overland transport of mined ore on the biota.

Similar to lichens and bryophytes, aquatic macroinvertebrates possess many of the hallmark traits of good bioindicators (Table 1). The most common application of macroinvertebrates as bioindicators, due to their speciose nature, is at the community scale. An unimpaired stream or river commonly contains more than 40 identifiable taxa, representing a range of habitat preferences and life history strategies. This taxonomic and functional diversity can capture the myriad responses to different stressors and disturbances, including the presence of fine sediment, metals, nutrients, and hydrologic alterations. Accordingly, macroinvertebrate communities have been frequently used as

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Chapter III environmental, ecological, and biodiversity indicators. Currently, all 50 states of the United States use aquatic macroinvertebrates to assess the biological health of streams and rivers. For example, Miller et al. (2007) quantified aquatic macroinvertebrates to identify a threshold separating irrigation water withdrawals, which adversely affected the biota of river systems, from withdrawal levels that did not influence the community. Water withdrawals exceeding 85% of ambient levels, combined with elevated water temperatures, reduced the proportion of disturbance-intolerant taxa, consequently shifting the community toward more disturbance-adapted species (Figure 4). Resource managers can use the integrated response of the entire macroinvertebrate community to relate how much water can be taken for irrigation before negative biological responses are seen, while also using the responses of individual taxa, or groups of taxa, to indicate the mechanism(s) of environmental degradation (e.g., increased temperature or fine sediment levels) by which water withdrawals adversely impact aquatic ecosystems. Thus macroinvertebrate populations can be used as biodiversity and ecological indicators at the community scale and environmental indicators at the population scale.

Table 1: Regardless of the geographic region, type of disturbance, environment, or organism, good bio indicators often share several characteristics. Provide measurable response (sensitive to the disturbance or stress but does not experience mortality or accummulate pollutants directly from their environment)

Response reflects the whole

population/community/ecosystem response Good indicator ability Respond in proportion to the degree of contamination or degradation Adequate local population density (rare species are not optimal)

Abundant and common Common, including distribution within area of question Relatively stable despite moderate climatic and environmental variability Ecology and life history well understood Well-studied Taxonomically well documented and stable Easy and cheap to survey Economically/commercially Species already being harvested for other purposes important Public interest in or awareness of the speces

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What Makes a Good Bioindicator?

Considering the 1.7 million species that currently documented on Earth, how do we chose just one as a bioindicator? The answer is simple: No single species can adequately indicate every type of disturbance or stress in all environments. Depending upon the specific environment, the species present, and local disturbances, appropriate bioindicator species or groups of species need to be selected. Ecologists have established a broad set of criteria that species must exhibit to be considered good bioindicators (see Table 1).

Benefits and Disadvantages of Bioindicators

The numerous benefits of bioindicators have spurred legislative mandates for their use in countries around the world and their inclusion in several international accords. Yet bioindicators are not without their problems. Like the canaries in the coal mine, we rely upon the sensitivity of some bioindicators to function as early-warning signals. In some instances, we cannot discriminate natural variability from changes due to human impacts, thus limiting the applicability of bioindicators in heterogeneous environments. Accordingly, populations of indicator species may be influenced by factors other than the disturbance or stress (e.g., disease, parasitism, competition, predation), complicating our picture of the causal mechanisms of change. A second criticism of the use of bioindicators is that their indicator ability is scale-dependent. For example, a large vertebrate indicator (e.g., a fish) may fail to indicate the biodiversity of the local insect community. Third, bioindicator species invariably have differing habitat requirements than other species in their ecosystem. Managing an ecosystem according to the habitat requirements of a particular bioindicator may fail to protect rare species with different requirements. Finally, the overall objective of bioindicators is to use a single species, or a small group of species, to assess the quality of an environment and how it changes over time, but this can represent a gross oversimplification of a complex system.

Like all management tools, we must be conscious of its flaws. However, the limitations of bioindicators are clearly overshadowed by their benefits. Bioindicators can be employed at a range of scales, from the cellular to the ecosystem level, to evaluate the health of a particular ecosystem. They bring together information from the biological, physical, and chemical components of our world that manifest themselves as changes in individual fitness, population density, community composition, and ecosystem processes. From a management perspective, bioindicators inform our actions as to what is and is not

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Chapter III biologically sustainable. Without the moss in the tundra, the cutthroat in the mountain stream, and the canary in the coal mine, we may not recognize the impact of our disturbances before it is too late to do anything to prevent them.

Conservation status

The conservation status of a species indicates the likelihood that it will become extinct. Many factors are considered when assessing the conservation status of a species; e.g., such statistics as the number remaining, the overall increase or decrease in the population over time, breeding success rates, or known threats.[2] The IUCN Red List of Threatened Species is the best-known worldwide conservation status listing and ranking system.[3]

Over 40% of the world's species are estimated to be at risk of extinction.[4] Internationally, 199 countries have signed an accord to create Biodiversity Action Plans that will protect endangered and other threatened species. In the United States, such plans are usually called Species Recovery Plans.

IUCN Red List Though labelled a list, the IUCN Red List is a system of assessing the global conservation status of species that includes "Data Deficient" (DD) species – species for which more data and assessment is required before their status may be determined – as well species comprehensively assessed by the IUCN's species assessment process. Those species of "Near Threatened" (NT) and "Least Concern" (LC) status have been assessed and found to have relatively robust and healthy populations, though these may be in decline. Unlike their more general use elsewhere, the List uses the terms "endangered species" and "threatened species" with particular meanings: "Endangered" (EN) species lie between "Vulnerable" (VU) and "Critically Endangered" (CR) species, while "Threatened" species are those species determined to be Vulnerable, Endangered or Critically Endangered.

The IUCN categories, with examples of animals classified by them, include: Extinct (EX)

 Examples: aurochs  Bali tiger  blackfin cisco  Caribbean monk seal  Carolina parakeet  Caspian tiger

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 dodo  dusky seaside sparrow  eastern cougar  golden toad  great auk  Japanese sea lion  Javan tiger  Labrador duck  passenger pigeon  Schomburgk's deer  Steller's sea cow  thylacine  toolache wallaby  western black rhinoceros

Extinct in the wild (EW) Captive individuals survive, but there is no free-living, natural population.

 Examples: Barbary lion  Hawaiian crow  Père David's deer  scimitar oryx  Socorro dove  Wyoming toad

Critically endangered (CR) Faces an extremely high risk of extinction in the immediate future.

 Examples: addax  African wild ass  Alabama cavefish  Amur leopard  Arakan forest turtle  Asiatic cheetah  axolotl  Bactrian camel  black rhino  blue-throated macaw  Brazilian merganser  brown spider monkey  California condor  Chinese alligator  Chinese giant salamander  gharial  Hawaiian monk seal  Javan rhino

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 kakapo  Leadbeater's possum  Mediterranean monk seal  mountain gorilla  northern hairy-nosed wombat  Philippine eagle  red wolf  saiga  Siamese crocodile  Malayan tiger  Spix's macaw  southern bluefin tuna  South China tiger  Sumatran orangutan  Sumatran rhinoceros  Sumatran tiger  vaquita  Yangtze river dolphin  northern white rhinoceros  hawksbill sea turtle  Kemp's ridley sea turtle

Endangered (EN) Faces a high risk of extinction in the near future.

 Examples: African penguin  African wild dog[a]  Asian elephant  Asiatic lion  Australasian bittern  blue whale  bonobo  Bornean orangutan  common chimpanzee  dhole  eastern lowland gorilla  hispid hare  giant otter  giant panda  Goliath frog  green sea turtle  loggerhead sea turtle  Grevy's zebra  hyacinth macaw  Humblot's heron  Iberian lynx  Japanese crane

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 Japanese night heron  Lear's macaw  Malayan tapir  markhor  Malagasy pond heron  Persian leopard  proboscis monkey  purple-faced langur  pygmy hippopotamus  red-breasted goose  Rothschild's giraffe  snow leopard  South Andean deer  Sri Lankan elephant  takhi (near Critically Endangered) Toque macaque  Vietnamese pheasant  volcano rabbit  wild water buffalo  white-eared night heron  fishing cat  tasmanian devil

Vulnerable (VU) Faces a high risk of endangerment in the medium term.

 Examples: African grey parrot  African bush elephant[b]  African lion[b]  American paddlefish  common carp  clouded leopard  cheetah[c]  dugong  Far Eastern curlew  fossa  Galapagos tortoise[d]  gaur  blue-eyed cockatoo  golden hamster  whale shark  hippopotamus  Humboldt penguin  Indian rhinoceros  Komodo dragon[e]  lesser white-fronted goose  mandrill  maned sloth

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 mountain zebra  polar bear  red panda  sloth bear  takin  yak  great white shark  American crocodile  dingo  king cobra

Near-threatened (NT) May be considered threatened in the near future.

 Examples: American bison  Asian golden cat  blue-billed duck  emperor goose  emperor penguin  Eurasian curlew  jaguar  leopard  Larch Mountain salamander  Magellanic penguin  maned wolf  narwhal  margay  montane solitary eagle  Pampas cat  Pallas's cat  reddish egret  white rhinoceros  striped hyena  tiger shark  white eared pheasant

Least concern (LC) No immediate threat to species' survival.

 Examples: American alligator  American crow  Indian peafowl  olive baboon  bald eagle  brown bear  brown rat

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 brown-throated sloth  Canada goose  cane toad  common wood pigeon  cougar  common frog  giraffe  grey wolf  house mouse  wolverine[6]  human  palm cockatoo  mallard  meerkat  mute swan  platypus  red-billed quelea  red-tailed hawk  rock pigeon  scarlet macaw  southern elephant seal  milk shark  red howler monkey

Criteria for classification

Criteria for 'Endangered (EN)'

A) Reduction in population size based on any of the following:

1. An observed, estimated, inferred or suspected population size reduction of ≥ 70% over the last 10 years or three generations, whichever is the longer, where the causes of the reduction are clearly reversible AND understood AND ceased, based on (and specifying) any of the following: 1. direct observation 2. an index of abundance appropriate for the taxon

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3. a decline in area of occupancy, extent of occurrence and/or quality of habitat 4. actual or potential levels of exploitation 5. the effects of introduced taxa, hybridisation, pathogens, pollutants, competitors or parasites. 2. An observed, estimated, inferred or suspected population size reduction of ≥ 50% over the last 10 years or three generations, whichever is the longer, where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) any of (a) to (e) under A1. 3. A population size reduction of ≥ 50%, projected or suspected to be met within the next 10 years or three generations, whichever is the longer (up to a maximum of 100 years), based on (and specifying) any of (b) to (e) under A1. 4. An observed, estimated, inferred, projected or suspected population size reduction of ≥ 50% over any 10 year or three generation period, whichever is longer (up to a maximum of 100 years in the future), where the time period must include both the past and the future, and where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible, based on (and specifying) any of (a) to (e) under A1.

B) Geographic range in the form of either B1 (extent of occurrence) OR B2 (area of occupancy) OR both:

1. Extent of occurrence estimated to be less than 5,000 km², and estimates indicating at least two of a-c: 1. Severely fragmented or known to exist at no more than five locations. 2. Continuing decline, inferred, observed or projected, in any of the following: 1. extent of occurrence 2. area of occupancy 3. area, extent and/or quality of habitat 4. number of locations or subpopulations 5. number of mature individuals 3. Extreme fluctuations in any of the following: 1. extent of occurrence 2. area of occupancy 3. number of locations or subpopulations 4. number of mature individuals 2. Area of occupancy estimated to be less than 500 km², and estimates indicating at least two of a- c: 1. Severely fragmented or known to exist at no more than five locations. 2. Continuing decline, inferred, observed or projected, in any of the following: 1. extent of occurrence 2. area of occupancy 3. area, extent and/or quality of habitat 4. number of locations or subpopulations 5. number of mature individuals 3. Extreme fluctuations in any of the following: 1. extent of occurrence 2. area of occupancy 3. number of locations or subpopulations 4. number of mature individuals

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C) Population estimated to number fewer than 2,500 mature individuals and either:

1. An estimated continuing decline of at least 20% within five years or two generations, whichever is longer, (up to a maximum of 100 years in the future) OR 2. A continuing decline, observed, projected, or inferred, in numbers of mature individuals AND at least one of the follow (a-b): 1. Population structure in the form of one of the following: 1. no subpopulation estimated to contain more than 250 mature individuals, OR 2. at least 95% of mature individuals in one subpopulation 2. Extreme fluctuations in number of mature individuals

D) Population size estimated to number fewer than 250 mature individuals.

E) Quantitative analysis showing the probability of extinction in the wild is at least 20% within 20 years or five generations, whichever is the longer (up to a maximum of 100 years).

1.

 Near-critically endangered.   Particularly sensitive to poaching levels.

  Near-endangered due to poaching.

  May vary according to levels of tourism.

 Varies according to female populations.

Endangered and Endemic species of India

ENDANGERED SPECIES OF INDIA

A plant, animal or microorganism that is in immediate risk of biological extinction is called endangered species or threatened species. In India, 450 plant species have been identified as endangered species. 100 mammals and 150 birds are estimated to be endangered. India's biodiversity is threatened primarily due to:

1. Habitat destruction 2. Degradation and 3. Over exploitation of resources

The RED-data book contains a list of endangered species of plants and animals. It contains a list of species of that are endangered but might become extinct in the near future if not protected. Some of the rarest animals found in India are:

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1. Asiatic cheetah 2. Asiatic Lion 3. Asiatic Wild Ass 4. Bengal Fox 5. Gaur 6. Indian Elephant 7. Indian Rhinocerous 8. Marbled Cat 9. Markhor

Extinct species is no longer found in the world.

Endangered or threatened species is one whose number has been reduced to a critical number. Unless it is protected and conserved, it is in immediate danger of extinction.

Vulnerable species is one whose population is facing continuous decline due to habitat destruction or over exploitation. However, it is still abundant.

Rare species is localized within a restricted area or is thinly scattered over an extensive area. Such species are not endangered or vulnerable.

A few endangered pecies in the world are listed below:

1. West Virginia Spring Salamander (U.S.A) 2. Giant Panda (China) 3. Golden Lion Tamarin (Brazil) 4. Siberian Tiger (Siberia) 5. Mountain Gorilla (Africa) 6. Pine Barrens Tree Frog (Male) 7. Arabian Oryx (Middle East) 8. African Elephant (Africa)

Other important endangered species are:

1. Tortoise, Green sea Turtle , Gharial, Python (Reptiles) 2. Peacock, Siberian White Crane, Pelican, Indian Bustard (Birds) 3. Hoolock gibbin, Lion-tailed Macaque, Capped mokey, Golden monkey (Primates) 4. Rauvol fia serpentina (medicinal plant), Sandal wood tree, etc

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FACTORS AFFECTING ENDANGERED SPECIES

1. Human beings dispose wastes indiscriminately in nature thereby polluting the air, land and water. These pollutants enter the food chain and accumulate in living creatures resulting in death. 2. Over-exploitation of natural resources and poaching of wild animals also leads to their extinction. 3. Climate change brought about by accumulation of green houses gases in the atmosphere. Climate change threatens organisms and ecosystems and they cannot adjust to the changing environmental conditions leading to their death and extinction.

An international treaty to help protect endangered wildlife is, "Convention on International Trade in Endangered Species 1975" (CITES). This treaty is now signed by 160 countries.

1. CITES lists 900 species that cannot be commercially traded as live specimens or wildlife products as they are in danger of extinction. 2. CITES restricts trade of 2900 other species as they are endangered.

DRAWBACKS OF CITES

1. This treaty is limited as enforcement is difficult and convicted violators get away by paying only a small fine. 2. Member countries can exempt themselves from protecting any listed species.

Endemic species of India

Species that are found only in a particular region are known as endemic species. Almost 60% the endemic species in India are found in Himalayas and the Western Ghats. Endemic species are mainly concentrated in:

1. North-East India 2. North-West Himalayas 3. Western Ghats and 4. Andaman & Nicobar Islands.

Examples of endemic Flora species are

1. Sapria Himalayana 2. Ovaria Lurida 3. Nepenthis khasiana etc

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Endemic fauna of significance in the western ghats are:

1. Lion tailed macaque 2. Nilgiri langur 3. Brown palm civet and 4. Nilgiri tahr

Factors affecting endemic species:

1. Habitat loss and fragmentation due to draining and filling of inland wetlands. 2. Pollution also plays an important role.

Ex:

1. Frog eggs, tadpoles and adults are extremely sensitive to pollutants especially pesticides. 2. Over-hunting and 3. Populations can be adversely affected by introduction of non active predators and competitors. Disease producing organisms also play an important adversary in reducing populations of endemic species.

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Suggested Readings:

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 Borman, F.H. and G.E. Likens. 1970. "The nutrient cycles of an ecosystem." Scientific American, October 1970, pp 92-101.  Wessells, N.K. and J.L. Hopson. 1988. Biology. New York: Random House. Ch. 44.  Burgess, Ernest W. (1925) 1961 The Growth of the City: An Introduction to a Research Project. Pages 37–44 in George A. Theodorson (editor), Studies in Human Ecology. Evanston, Ill.: Row, Peterson.  Christaller, Walter 1933 Die zentralen Orte in Siiddeutschland: Eine okonomisch- geographische Untersuchung iiber die Gesetzmdssigkeit der Verbreitung und Entwicklung der Siedlungen mit stddtischen Funktionen. Jena (Germany): Fischer.  Duncan, Otis Dudley 1959 Human Ecology and Population Studies. Pages 678–716 in Philip M. Hauser and Otis Dudley Duncan (editors), The Study of Population: An Inventory and Appraisal. Univ. of Chicago Press.  Hawley, Amos H. 1950 Human Ecology: A Theory of Community Structure. New York: Ronald.  McKenzie, Roderick D. (1924) 1925 The Ecological Approach to the Study of the Human Community. Pages 63–79 in Robert E. Park, Ernest W. Burgess, and Roderick D. McKenzie, The City. Univ. of Chicago Press. -* First published in Volume 30 of the American Journal of Sociology.  Park, Robert E. (1936) 1952 Human Ecology. Pages 145–158 in Robert E. Park, Human Communities: The City and Human Ecology. Collected Papers, Vol. 2. Glencoe, Ill.: Free Press. → First published in Volume 42 of the American Journal of Sociology.  Quinn, James A. 1950 Human Ecology. Englewood Cliffs, N.J.: Prentice-Hall.  Schnore, Leo F. 1958 Social Morphology and Human Ecology. American Journal of Sociology 63:620–634.  Steward, Julian H. 1955 Theory of Culture Change: The Methodology of Multilinear Evolution. Urbana: Univ. of Illinois Press.  golley, frank. a primer for ecological literacy. new haven, conn.: yale university press, 1998.  gumbine, r. edward. "what is ecosystem management?" conservation biology 8 (1994): 27-38.  leopold, aldo. "the land ethic." in a sand county almanac. new york: oxford university press, 1968.  northcott, michael s. the environment and christian ethics. cambridge, uk: cambridge university press, 1996.  pimentel, david; westra, laura; and noss, reed f., eds. ecological integrity: integrating environment, conservation, and health. washington, d.c.: island press, 2000.  rolston, holmes, iii. "the bible and ecology." interpretation: journal of bible and theology 50 (1996): 16–26.  sagoff, mark. "ethics, ecology, and the environment: integrating science and law." tennessee law review 56 (1988): 77-229.  soulé, michael e., and lease, gary, eds. reinventing nature? responses to postmodern deconstruction. washington, d.c.: island press, 1995.  holmes rolston, iii  Billington, Elizabeth T. Understanding Ecology. New York: F. Warne, 1971.  Curtis, Helena, and N. Sue Barnes. Biology, 5th ed. New York: Worth Publishing, 1989.  Darwin, Charles. On the Origin of Species. Danbury, CT: Grolier Enterprises, 1981.

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  Haeckel, Ernst. The Riddle of the Universe, trans. Joseph McCabe. New York: Buffalo Books, 1992.  Miller, G. Tyler, Jr. Living in the Environment, 6th ed. Belmont, CA: Wadsworth, 1990.  Pringle, Laurence. Lives at Stake: The Science and Politics of Environmental Health. New York: Macmillan Publishing Company, 1980.  Purves, William K., and Gordon H. Orians. Life: The Science of Biology. Sunderland, MA: Sinauer, 1987.  Sharpe, Grant William. Interpreting the Environment, 2nd ed. New York: Wiley, 1982.  Sharpe, Grant William, Clare W. Hendee, and Shirley W. Allen. Introduction to Forestry, 5th ed. New York: McGraw-Hill, 1986.  arignan, V. & M.-C. Villard. Selecting indicator species to monitor ecological integrity: A review. Environmental Monitoring and Assessment 78, 45–61 (2002).  Hasselbach, L. et al. Spatial patterns of cadmium and lead deposition on and adjacent to National Park Service lands in the vicinity of Red Dog Mine, Alaska. Science of the Total Environment 348, 211–230 (2005).  Iwama, G. K. et al. Heat shock protein expression in fish. Reviews in Fish Biology and Fisheries 8, 35–56 (1998).  Miller, S. W. et al. Resistance and resilience of macroinvertebrates to irrigation water withdrawals. Freshwater Biology 52, 2494–2510 (2007).  Rainio, J. & Niemelä, J. Ground beetles (Coleoptera: Carabidae) as bioindicators. Biodiversity and Conservation 12, 487–506 (2003).  Rosenberg, D. M. & Resh, V. H. Freshwater Biomonitoring and Benthic Macroinvertebrates. New York, NY: Chapman and Hall, 1992.  Tanabe, S. & Subramanian, A. Bioindicators of POPs: Monitoring in Developing Countries. Kyoto, Japan: Kyoto University Press, 2006.

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