Environment & Ecology


To prepare for ENVIRONMENT  for any competitive exam, aspirants have to know Environment & Ecology.  Here we will study Environment & Ecology in details. It gives an idea of all the important topics for the IAS Exam and the Governance syllabus (GS-II.). Environment & Ecology terms are important from Environmental perspectives in the UPSC exam. IAS aspirants should thoroughly understand their meaning and application, as questions can be asked from this static portion of the IAS Syllabus in both the UPSC Prelims and the UPSC Mains exams. Even these topics are also highly linked with current affairs. Almost every question asked from them is related to current events. So, apart from standard textbooks, you should rely on newspapers and news analyses as well for these sections.



  • The word “Environment”, in its most basic meaning, is “that which surrounds”, derived from the French preposition ‘environ (around)’.
  • It is defined as the surroundings or conditions in which an organism lives or operates.
  • The environment broadly includes biotic (living) and abiotic (non-living) components which are listed in the table given below
  • An environment in the real sense is the surrounding around us, where we feel, see, and perform our daily task.
  • Earth is a form of environment, which comprises the components like water, air, living beings, non-living beings, etc.
  • Living organisms need both abiotic and biotic components of the environment for survival.
  • A delicately balanced relationship between living organisms and their environment is critically important for their survival.




  • The term ecology was derived from two Greek words ‘Oikos’ meaning home and ‘logos’ meaning study.
  • German zoologist Ernst Haeckel used the term  ‘oekologie’ (‘ecology’) in 1869  first 
  • ‘Ecology may be defined as the scientific study of the relationship of living organisms with each other and with their environment.’
  • Ecology has been broadly divided into autecology and synecology.
  • Autecology: Autecology is the study of individual organism or individual species. It is also known as population ecology.
  • Autecology helps us to understand the relationships between individual plants and environment.
  • Synecology: 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.
  • Synecology helps us to understand the relationships between communities and environment.



  • What do you understand by ecology? What measures are being taken to preserve the wild flora and fauna and protect the endangered species of animals in India? Name three species for which special measures have been taken to preserve. What are the main objectives of Government science policy? What steps are being taken for the optimum utilisation of manpower, and improvement in the quality of life and technical education? (1981)



The main levels of organisation of ecology are the following:


Individual and Species:

  • An individual can be any living organism that has the ability to function independently.
  • It is a body made up of organs, organelles and other parts that work together to carry out various processes of life for e.g. a lion, an elephant, a tiger, a wolf etc.
  • They make the basic unit of study in ecology.
  • The organisms of the similar type have the potential for interbreeding, and produce fertile offspring, which are called species.



  • A population is an assemblage of similar organisms belonging to the same species, living together at one place at a given time.
  • A population always lives a specific place known as its habitat.
  • Populations of plants and animals in the ecosystem do not function independently of each other. They are always influencing each other and organizing themselves into communities and have functional relationship with their external environment for e.g., a pride of lions, a herd of elephants, a school of fish, a flock of sheep etc.
  • Population growth rate is the percentage variation between the numbers of individuals in a population at two different times. Therefore, the population growth rate can be positive or negative.
  • The factors limiting growth/ decline of population are biotic and abiotic components. Population density is the relation between the number of individuals of a population and the area they occupy.



  • Community can be defined as the collection of different species of population (both plant and animal species) in a specific area at a given point of time. These species can vary vastly in number and size.
  • A Community in most instances is named after the dominant plant species. g., grasses dominate a grassland community, though it may contain herbs, shrubs, and trees along with associated animals of different species.
  • Based on size and degree of relative independence communities may be divided into two types: Major Communities and Minor Communities.
  • Major Communities: These are large sized and relatively independent. They depend only on the sun’s energy from outside. Eg: Tropical evergreen forests.
  • Minor Communities: These are dependent on neighboring communities and are often called societies.
  • They are secondary aggregations within a major community. Eg: A mat of lichen on a cow dung pad.



  • The term ecosystem was coined by Sir Arthur Tansley in 1935.
  • An ecosystem is a functional unit of nature encompassing complex interaction between its biotic (living) and abiotic (non-living) components. For example- a pond is a good example of ecosystem.
  • An ecosystem in composed of a biotic community, integrated with its physical environment through the exchange of energy and recycling of the nutrients.
  • Ecosystems can be recognised as self- regulating and self-sustaining units of landscape
  • An ecosystem has two basic components:
  • Abiotic (non-living), and
  • Biotic (living organisms).
  • Abiotic components– comprise inorganic materials, such as carbon, nitrogen, oxygen, carbon dioxide, water etc., while biotic components include producers, consumers and decomposers.


Functions of ecosystem

Ecosystems are complex dynamic system. They perform certain functions.

  • Energy flow through food chain
  • Nutrient cycling (biogeochemical cycles)
  • Ecological succession or ecosystem development
  • Homeostasis (or cybernetic) or feedback control mechanisms


According to de Groot et al. 2002 there are four primary groups of ecosystem functions

  • Regulatory functions
  • Production functions
  • Habitat functions
  • Information functions


Question :

  • The Millennium Ecosystem Assessment describes the following major categories of ecosystem services- provisioning, supporting, regulating, preserving and cultural. Which one of the following is supporting service?
  1. Production of food and water
  2. Control of climate and disease
  3. Nutrient cycling and crop pollination
  4. Maintenance of diversity

Ans. C

Types of ecosystems

  • Ecosystems are classified as follows:
  • Natural ecosystems
  • Man made ecosystems

(i) Natural ecosystems:  (a) Totally dependent on solar radiation e.g. forests, grasslands, oceans, lakes, rivers and deserts. They provide food, fuel, fodder and medicines.

(b) Ecosystems dependent on solar radiation and energy subsidies (alternative sources) such as wind, rain and tides. e.g tropical rain forests, tidal estuaries and coral reefs.


(ii) Man made ecosystems:  (a) Dependent on solar energy-e.g. Agricultural fields and aquaculture ponds. (b) Dependent on fossil fuel e.g. urban and industrial ecosystems.



  • This is a large regional unit characterised by a major vegetation type and associated fauna found in a specific climate zone.
  • Biomes refer basically to terrestrial areas. The aquatic systems like the seas, rivers etc. are also divided into distinct life zones on basis of salinity, level of dissolved nutrients, water, temperature and depth of sunlight penetration.
  • It includes all associated developing and modified communities occurring within the same climatic region, e.g., forest biomes, grassland and savanna biomes, desert biome, etc.
  • The climate determines the boundaries of a biome and the abundance of plants and animals found in each one of them.
  • The most important climatic factors are temperature and precipitation.
  • On a global scale, all the earth’s terrestrial biomes and aquatic systems constitute the biosphere.



  • The term ‘Biosphere’ was given by geologist Edward Suezz in 1875.
  • Biosphere is a part of the earth where life can exist. It is a zone of life on earth where plants and animals, including we, develop kinship with one another for life, food, water, shelter, mates etc.
  • This discrete unit has living and non-living components, which are interdependent and interrelated in terms of their structure, components, and functioning.
  • Biosphere represents a highly integrated and interacting zone comprising of atmosphere (air), hydrosphere (water), and lithosphere (land). It is the narrow layer around the surface of the earth.
  • The global environment consists of three main sub-divisions:
  • The hydrosphere which includes all the water components,
  • The lithosphere comprises the solid components of the earth’s crust, and
  • The atmosphere formed of the gaseous envelope of the earth. The biosphere consists of the lower atmosphere, the land and the oceans, rivers and lakes, where living beings are found.
  • Biosphere is absent at extremes of the north and south poles. Occasionally spores of fungi and bacteria do occur at heights beyond 8000mts, but they are not metabolically active and represent only the dormant life.
  • The organisms in the biosphere may broadly be divided into the plant kingdom and the animal kingdom.
  • The three domains of the earth interact with each other and affect each other in some way or the other. For example, cutting of forests for fulfilling our needs of wood, or clearing land for agriculture may lead to fast removal of soil from slopes.
  • Similarly earth’s surface may be changed due to natural calamities like earthquakes. For example, there could be submergence of land, as happened in the case of Tsunami recently. Parts of Andaman & Nicobar Islands were submerged under water.
  • Discharge of waste material into lakes and rivers makes the water unsuitable for human use. It also damages other forms of life. Emission from industries, thermal power plants and vehicles, pollute the air. Carbon dioxide (CO2 ) is an important constituent of air
  • But increase in the amount of CO2 leads to increase in global temperatures. This is termed as global warming.
  • There is thus, a need to limit the use of resources of the earth to maintain the balance of nature between the domains of the lithosphere, the atmosphere and the hydrosphere.



  • Recently the term ecosphere is being used more commonly. It is used to denote biosphere (living components) along with its three abiotic components –atmosphere, hydrosphere and lithosphere of the earth as one entity (unit).
  • Ecosphere = Biosphere + Lithosphere + Hydrosphere + Atmosphere




Bio Geographic Realm


Ø  Biosphere is divided into different Bio-Geographic Realm which are large spatial regions within which ecosystems share a broadly similar biological history.

Ø  In most cases, the organisms living within these biogeographic realms have been isolated from the rest of the organisms around the world and have, therefore, experienced distinct evolutionary processes.

Ø  Assessing biodiversity at the level of biogeographic realms is important because the realms display substantial variation in the extent of change, they face different drivers of change, and there may be differences in the options for mitigating or managing the drivers .

Ø  Biogeographic realms are further divided into eco-regions, which are, in turn, divided into biomes.

(Eco-regions are geographical regions that are characterized by specific ecological patterns, including soil health, flora and fauna, climatic conditions, among other factors.)

Ø  There are 8 biogeographic realm: Antarctica, Oceania,  India-malayan, Australian, Neotropic, Afrotropic, Nearctic and Palearctic.


  • Every living organism lives in a specific environment. A place or a set of environmental conditions in which a particular organism lives is called its habitat.
  • The habitats of different plants and animals are different, but at the same time many plants and animals share the same habitat.
  • Example: All forests are not habitats of tigers or lions. Jim Corbett National Park in Uttaranchal has thick forests. It provides optimum conditions for the tigers to live. There are streams and rivers flowing in the area that provide water. The presence of deer and sambhar in large number in the same habitat provide food for the tigers. Thus, a habitat must provide the organisms suitable climatic conditions, shelter and food.
  • All habitats are environments, but all environments are not habitats.
  • A habitat always has life in it, whereas the environment does not necessarily have life in it.
  • The habitat is a defined place or area of the environment according to the requirements of a particular life form. Therefore, a habitat is always an environment, but an environment is not always a habitat.
  • A habitat is always a preference of one species, whereas an environment could be a preference of many species that could eventually become many habitats.


  • An Ecotone describes an area that acts as a transition or boundary between two ecosystems. Hence it is a zone of tension. This could be, for example, an area of marshland between a river and
  • the riverbank, a clearing within a forest or a much larger area such as the transition between Arctic Tundra and Forest biomes in Northern Siberia.
  •         ECOCLINE
  •         Ecocline is a zone of gradual but continuous change from one ecosystem to another when there is no sharp boundary between the two in terms of species composition.
  •         Ecocline occurs across the environmental gradient (gradual change in abiotic factors such as altitude, temperature (thermocline), salinity (halocline), depth, etc.
  • As this area is inevitably influenced by the two bordering ecosystems, it is therefore a consequence of this that a higher density of organisms and variety of species can be found within an ecotone. This increase in biodiversity is referred to as the edge effect”.
  • The organisms which occur primarily or most abundantly in this zone are known as edge species.
  • An Ecotone can be formed naturally – through abiotic factors such as changes in soil composition – but can also be created through the result of human interaction. Clearing of forest areas or irrigation are examples of this.
  • Ecotones are considered areas of great environmental importance. As well as providing an area for a large number of species, they often experience influx from animals looking to nest or searching for food.
  • They may also be considered a habitat of greater genetic diversity and serve as bridges of “gene flow” from one population to another.
  • Additionally an Ecotone can act as a “buffer-zone” protecting the neighbouring ecosystem from possible environmental damage – i.e. a wetland area could absorb pollutants preventing them from seeping into a river or estuary. It is not surprising therefore the Ecotones have attracted a lot of scientific interest.
  • Ecotones could contain species that are entirely different from those found in the bordering systems.
  • Ecotones provide a sensitive indicator of global change. A contraction or shifting of boundaries is now believed to be a result of climate change.
  • Since many fauna and flora found in Ecotones are at the limits of their boundaries, any changes to the local environment will be felt by these species first. Their activities therefore act as a barometer for change.


v  Ecotopes are smallest ecologically distinct landscape features in landscape mapping and classification system.

v  They represent relatively homogenous spatially explicit landscape units which are useful for stratifying landscapes into ecologically distinct features for measurement and mapping of landscape structure, function and change


  • In nature, many species occupy the same habitat but they perform different functions. The functional characteristics of a species in its habitat, is referred to as “niche”.
  • While habitat of a species is like its ‘address’ (i.e. where it lives), niche can be thought of as its “profession” (i.e. activities and responses specific to the species).
  • The term niche means the sum of all the activities and relationships of a species by which it uses the resources in its habitat for its survival and reproduction.
  • A niche is unique for a species, while many species may share the same habitat. No two species in a habitat can have the same niche. This is because if two species occupy the same niche, they will compete with one another until one is displaced.
  • For example, different species of insects may be pests of the same plant, but they can co-exist as they feed on different parts of the same plant that is because their niches are different.
  • Another such example is the vegetation of the forest. The forest can support a large number of plant species as they occupy different niches: the tall trees, the short trees, shrubs, bushes and grasses. Their heights vary and they differ in their requirements for sunlight and nutrients and so they can all survive together.
  • The most important resources available in the niches of animals are food and shelter while in case of plants, they are moisture and nutrients (phosphorus and nitrogen).
  • Understanding how organisms function together through their ecological niches is crucial as it can help in conservation of endangered species and limiting the role of invasive species.


  • Biomes are large areas on Earth with similar conditions, such as similar climates and similar living organisms. There are two main categories of biomes.
  • Terrestrial biomes are usually defined by the type of vegetation that is present. The major climatic factors contributing to the vegetation types in these biomes are temperature and precipitation.
  • Aquatic biomes are defined by the type of water they contain.


  • Terrestrial : These are the biomes found on land e.g„ Tundra, forests, deserts, grasslands
  • Aquatic: These are the biomes found in water. These can be :
  1. Fresh waters, such as pond, lake and river
  2. Marine as oceans, shallow sea
  • Biomes are characterized by three factors: Temperature, precipitation and latitude. For example medium temperature and mid latitude is marked by temperate forest and grassland while tropics with high temperature and high precipitation is characterized by rainforests.


Terrestrial Biomes:


  1. Tundra:
  • The word tundra means a “barren land” since they are found in those regions of the world where environmental conditions are very severe. There are two types of tundra, arctic and alpine.


  • Arctic tundra extends as a continuous belt below the polar ice cap and above the tree line on the northern hemisphere. It occupies the northern fringe of Canada Alaska, European Russia, Siberia and island group of Arctic Ocean.
  • Alpine tundra occurs at high mountain peaks above the tree line. Since mountains are found at all latitudes therefore alpine tundra show day and night temperature variations

Climate: Permanently frozen subsoil called permafrost is found in the arctic and antarctic tundra.

  • The summer temperature may be around 15°C and in winter it may be as low as –57°C in arctic tundra.
  • Poor soil conditions prevent quick recovery of tundra in case it is disturbed.
  • A very low precipitation of less than 400 mm per year.
  • A short vegetation period of generally less than 50 days between spring and autumn frost.
  • Productivity is low.

Flora and fauna : Typical vegetation of arctic tundra is cotton grass, sedges, dwarf heath, willows birches and lichens.

  • Animals of tundra are hurepian reindeer, musk ox, arctic hare, caribous, lemmings and squirrel. Their body is covered with fur for insulation, Insects have short life cycles which are completed during favourable period of the year.


2.Tropical Rain (Evergreen) Forest:

  • These are in the tropical region of very high rain fall. Such forests are well developed over the western coast of India and North eastern Himalayas and scattered in south east Asia, west Africa and north coast of South America.
  • Tropical Rainforest occupy 52% of global forest area.


Main characteristics:

  • Temperature and light intensity are very high;
  • Rain fall is greater than 200 cm. per year;
  • Soil of these regions is rich in humus; However most of the tropical rainforests soil are poor and infertile.
  • The rate of turnover of the nutrients is very high leading to high productivity and have highest standing crop and biomass;
  • Tropical rainforests are the most rich tree species forest on the Earth.
  • The vegetation includes broad evergreen trees of about 200 feet like Health bamboos, ferns, shrub etc. Epiphytes and woody wines (liannas) are also abundant. Many tree species show buttresses (swollen stem bases) and leaves with drip tips;. Buttresses at the base of the trunk of trees help to stabilize them in shallow forest soils.
  • Epiphytes are those plants that grows upon another plantor object merely for physical support. The majority of the world’s epiphytes live in moist tropical forests.
  • The vegetation of these forests present a four layered structure. Each Layer has unique characteristics based on differing layers of water, sunlight, and air circulation. The layers are as following
  • Emergent Layer: This is the topmost layer where trees exists as tall as 60 metres (200 ft) dominating the skyline. The foliage is often sparse but spreads wide as trees reach sunny upper layer. Trees in emergent layer have small waxy leaves to retain water during long droughts or dry season. They have lightweight seeds to be carried away by wind.
  • Canopy Layer: It is beneath emergent layer and is a deep layer of vegetation roughly about 6 meters thick. Canopy’s dense network of leaves and branches form a roof over other two remaining layer and block winds rainfall and sunlight. This creates a humid, still and dark environment below.
  • Understory Layer: Located below the canopy layer ,this layer is darker and stiller and has more humid environment than canopy layer. Plants in this layer have larger leaves to catch minimum sunlight reaching beyond the dense canopy.
  • Forest Floor Layer: Also known as shrub layer, it is the lowermost layer and is the darkest of all rainforest layer making it extremely difficult for plants to grow.
  • Each of the above layer is distinct and exist as independent system. However processes and species of one layer influences those of another.
  • These forests have rich invertebrate and vertebrate fauna. Snails, centipedes, millipedes and many insect species are common near the forest floor. Rhacophorus (flying frog), aquatic reptiles, Chameleon and many birds are common in these forests. Mammals of these forests are sloths, monkeys, ant eaters, leopards, jungle cats and giant flying squirrels.

Why soil of tropical rainforests are poor and infertile?


  • Low pH of soil which makes it highly acidic. Absorption capacity by roots of plants depends upon acidity difference between soil and roots. Low acidity difference leads to low nutrient absorption by plants.
  • The type of clay particles present in soil of tropical rainforests has poor ability to trap nutrients and prevent them from being washed away.
  • Due to high temperature and moisture ,the organic matter decomposes faster than any other biomes causing release and loss of nutrients quickly.
  • High rainfall in the region washes nutrients out of the soil quickly.
  • How nutrient exchange occur among plants in spite of poor and infertile soil?
  • This is because on ground of the rainforest there is a thick layer dead and decaying plants and animals.
  • The decay rate of these are high. The nutrients released from these are washed away by heavy rains almost directly from the rotting surface material into the trees without entering into the soil.
  • The roots of the forests have shallow roots structure to absorb those nutrients.


3.Temperate Deciduous Forests:

  • Trees of deciduous forests shed their leaves in autumn and new foliage grows in spring. They occur mostly in northwest, central and eastern Europe, eastern north America, north China, Korea, Japan, far eastern Russia and Australia.
  • These type of forests occupy 17% of Global Forest Areas.

 Climate : These forests occur in the areas of moderate climatic conditions such as:

  • Annual rainfall is 75 to 150 cm.
  • Winter lasts for four to six months.
  • Temperature ranges between 10 to 20°C.
  • Soil is brown and rich in nutrients.
  • Hence these are generally the most productive agricultural areas on earth.

Flora and fauna: Commonly found trees in this ecosystem are oak, birch heath, chest nuts, pitch pine, cyprus.

  • Invertebrate fauna comprises green oak moth, bark beetle, green flies, aphids, sapflies, moths and butterflies.
  • Prominent grazers are grass eating rodents, deer and bison. Rodents play a very important role in these forests. They feed on the seeds, fruits and leaves of the trees and consume much more food than the large sized grazers.
  • Common carnivores in temperate forests are wild cat, wolves, foxes, tawny owl and sparrow hawk. Black bear, raccoons and skunks are the omnivorous animals of these forests.


4.Tropical Deciduous Forests:


  • These kind of forests occur in regions with heavy rainfall for part of the year followed by a dry season.
  • Tropical deciduousare found in the large part of India, northern Australia and in central America.
  • These forests become lush green during wet summers but become dry landscape during winters when most of the trees shed their leaves. Hence they are also called Monsoon Forests.
  • These forests are comparatively less dense than evergreen forests


  • Annual Rainfall: 70-200cm
  • Temperature: Average temperature around 30°C
  • Humidity: 80-90%.
  • Tropical deciduous forests are further categorized into Moist deciduous Forests & Dry Deciduous Forests.
  • Moist deciduous forests are found in region with rainfall 100-200cm and humidity range around 60-75%. The average annual temperature in these forests are around 27°C.
  • Dry Deciduous Forests are found in region having rainfall of 70-100 cm. The trees in these forests completely shed their leaves during dry season turning the forests into a vast grassland with naked trees dispersed all over the region. .The wetter part of these forests make transition into moist deciduous forests while drier margins make transition into thorn forests.

Flora & Fauna

  • Moist deciduous forests include tree species such as Teak, Sal, shisham, Hurra, Amla, Sandlewood etc.
  • Dry Deciduous forests include trees like Tendu, Palas, bel, Khair etc.
  • These forests also have a large number of animals. Lion, tiger, pig, deer and elephant are some of the animalsthat make these forests their habitat.


5.Coniferous forests:

  • Coniferous forests are also known as Taiga or Boreal forests. They extend as a continuous belt across north America and north Eurasia below the arctic tundra.
  • The taiga is the largest uninterrupted forest area on earth; its average width measures 1,500 km and covers 8% of the lands above sea level.
  • In the Himalayas, these are distributed above 1700 to 3000 metre altitude. They also occur at high altitude below the alpine tundra and tree line.


  • Climate is cold.
  • Long and harsh winters are for more than six months.
  • Mean annual temperature is below 0°C.
  • Soil is poor in nutrients and acidic in nature.

Flora and fauna:

  • Coniferous forests are characterized by conifers (gymnosperms). They are evergreen, drought resistant and woody. In many species the canopy is cone shaped.
  • The common species of trees of these forests are Spruce, fir and pine trees. The productivity is much less than other ecosystem.
  • There are very few animals in these forests. The herbivores are red squirrel, deer, goat, mule, moose etc. The carnivores are timber wolves, lynxes, wolverine, weasels mink and bear. Some common birds are cross bill, thrushes, warblers, flycatchers, robin and sparrow.



  • Grasslands are dominated by the grasses. They occupy about 20% of the land on earth’s surface. They occur in both tropical and temperate regions where environmental conditions are better than that of the desert but rainfall is not enough to support the growth of trees.
  • Grasslands represent an ecotone (a zone in between two ecosystems) and are found between forest on one side and deserts on the other.
  • They are subjected to greater variation of temperature, moisture, wind and light intensity of the sun.. Grasslands are known by various names in different parts of the world. For example they are called prairies (North America), steppes (Central Asia), savannas (Africa) and pampas (South America).
  • Tropical grasslands are commonly called Savannas. They occur in eastern Africa South America, Australia and India. Savannas form a complex ecosystem as they contain grasses with groups of trees. Soil of grassland is rich and fertile.

Flora and fauna:

  • Grasses are the dominating plants with scattered drought resistant trees in the tropical grasslands. Trees are less than 10 m in height.
  • Animals are much reduced in grasslands because there is no shelter. The large herbivores of this biome are bison, proghorn (North America) wild horse, ass, saiga (Eurasia), zebra and antelope (South Africa). Carnivores are quite small in number and size. They are coyotes, weasels, badgers foxes and ferrets.
  • Hawks, lark sparrows, warblers, Great Indian Bustard and peafowl are the common birds found in grassland. Grasslands are very rich in reptilian and insect fauna.



  • Deserts are waterless barren regions of the earth. They occupy about one-seventh of the land on earth’s surface.
  • Deserts form an extreme condition in sequence of ecosystems with respect to the climatic condition. They occur in two belts that encircle the northern and southern hemispheres roughly centered over the tropics of Cancer and Capricorn.

Climate: Annual rain fall is very little. It may be less than 25 cm per annum. At some places if it is high it is unevenly distributed.

  • Temperature may be very high in subtropical deserts and very low in cold deserts e.g. Ladakh.
  • Winds have high velocity.


Flora and fauna:

  • Plants and animals have modified themselves to adapt to extremes of heat and aridity by using both physical and behavioural mechanism.
  • Xerophytic and Pheratophytic adaptation in plants are common to survive desert ecosystem


Xerophytic adaptation of plants (e.g cactus, calotropis):

Ø  Succulent and fleshy stem for storing water.

Ø  Stems covered with waxy coating or hairs.

Ø  Leaves reduced to small scale and sometimes into spines to reduce transpiration.

Ø  Waxy coatings on leaves and stems

Ø  Sunken stomata


Pheratophytic adaptation of plants (e.g. Honey mesquite, Welwitschia)


Ø  Pheratophytes are deep rooted plants which obtain significant portion of water that it needs from phreatic zone

Ø  Deep root structures enable them to be in constantly in touch with moisture as their roots extend more or less deeply into the aquifer.

Ø  Pheratophytes are indicators of potable groundwater.


  • Cacti, Acacia, Euphorbia and prickly pears are some of the Health common desert plants.
  • Desert biome has a large variety of fauna including mammals (e.g. camel, coyote), birds (e.g. roadrunner, barn owl), reptiles (e.g. banded gecko), insects (e.g desert locusts) and burrowing rodents
Adaptation of animals in deserts


Insects: Evaporation from respiratory surface is reduced to minimum invaginated spiracle system.


Rodents: They can live on dry seeds, succulent cacti and other  plants that store water and donot require drinking water.


Reptiles like snakes and lizards hibernate at depth of 0.5m or more in sand under rocks or in burrows od other animals. In burrowing snakes eyes are covered with minute shields  to protect them from sand.


Mammals like camel have following features to adapt to deserts.


Ø  tolerate greater degree of water depletion as they can drink water about 1/3rd of their body weight when water is available to them.

Ø  They have long eye lashes, hairy eyes and closing nostrails to protect them form sand.

Ø  They have wide feet which prevent them from sinking in sand.

Ø   Fat stored their humps enable them to go for months without food .

Ø  They have the ability to change body temperature to avoid loss of water due to sweating.

Ø  They are also provided with thick fur to keep them warm at night. As a result camel is truly referred as “ship of desert.”


  • Which of the following is/are unique characteristic/characteristics of equatorial forests? (2013)
  • Presence of tall closely set trees with crowns forming a continuous canopy.
  • Coexistence of a large number of species.
  • Presence of numerous varieties of epiphytes.

Select the correct answer using the code given below

  1. 1 only
  2. 2 and 3 only
  3. 1 and 3 only
  4. 1, 2 and 3

Answer: D


Aquatic Biomes:
  • Aquatic ecosystems are constituted by water bodies. Water covers about one third of the earth’s surface. Origin of life took place in aquatic ecosystem.
  • Therefore, these ecosystems make an important component of our biosphere.
  • Aquatic ecosystems are classified on the basis of salinity into following two types:
  • Freshwater
  • Marine


Freshwater Ecosystem:

  • Water on land which is continuously cycling and has low salt content is known as fresh Wetlands are between aquatic and terrestrial ecosystem.
  • They show an edge effect and form a ecotone. Ecotone is a transitional zone between two ecosystems. Examples of wet zone are swamps, marshes and mangroves.
  • The study of fresh water ecosystem is known as limnology. Fresh waters are classified into two types:
  • Standing or still water (Lentic) e.g. pond, lake, bogs and swamps.
  • Running water (Lotic) e.g. springs, mountain brooks, streams and rivers.
  • Commonly found flora in ponds and lakes include
  • Phytoplanktons (freely floating microscopic plants) such as algae, diatoms
  • Floating plant: Pistia, water hyacinth, Lemna, Azolla
  • Rooted plant: Hydrilla, Vallisnaria, trapa and water lily.
  • The common animals in ponds and lakes include:
  • Zooplankton (freely floating microscopic animals) such as protozoans and crustaceans;
  • Actively swimming fishes, frogs, tortoises.
  • Bottom dwellers like hydra, worms, prawns crabs, snails.
  • Birds such as herons, water fowls and ducks occurs in and around water.


Marine Ecosystem:

  • Distribution: Marine ecosystem covers nearly 71 % of the earth’s surface with an average depth of about 4000 m. Freshwater rivers eventually empty into ocean. Salinity of open sea is 3.6 percent and is quite constant Sodium and chlorine make up nearly 86 percent of the sea salt and the rest is due other elements such as sulphur, magnesium, potassium and calcium.
  • Temperature: The range of temperature variation is much less in sea than on the land although near the surface it is considerable from –2°C in antarctic ocean to 27°C in the warmer waters of pacific ocean. In the deeper layers temperature is constant at about 2°C.
  • Light: The light reaches upto a certain depth only. Deeper regions are permanently dark.
  • Pressure: Pressure increases with depth in oceans. It is 1 atmosphere near the surface and 1000 atmosphere at greatest depth.
  • Tides: The gravitational pulls of the sun and the moon cause tides in oceans. At the time of full moon and new moon tides are high and are called spring tides. At quarter moon the tides are exceptionally low and are known as low tide or neap tides.
  • Flora and fauna: Life in the oceans is limited but its biodiversity is very high as compared to terrestrial ecosystems. Almost every major group of animals occur somewhere or the other in the sea, except for insects and vascular plant which are completely absent in marine ecosystem.


  • UNEP participates in and leads partnerships to promote the science-policy
  • interface through global initiatives and platforms, including:

1) The Economics of Ecosystems and Biodiversity (TEEB)

2) The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES).

3) Wealth Accounting and the Valuation of Ecosystem Services (WAVES)

4) The Economics of Land Degradation (ELD) Initiative.


The Economics of Ecosystems and Biodiversity (TEEB)

  • The Economics of Ecosystems and Biodiversity (TEEB) was a study led by Pavan Sukhdev from 2007 to 2011. It is an international initiative to draw attention to the global economic benefits of biodiversity.
  • Its objective is to highlight the growing cost of biodiversity loss and ecosystem degradation and to draw together expertise from the fields of science, economics and policy to enable practical actions.
  • It is a global initiative focused on “making natures values visible”. Its principal objective is to mainstream the values of biodiversity and ecosystem services into decision-making at all levels.


Intergovernmental Science-Policy Platform on Biodiversity and

Ecosystem Services (IPBES)

  • IPBES is an independent intergovernmental body established by 134 States to strengthen the science-policy interface for biodiversity and ecosystem services for the conservation and sustainable use of biodiversity, long-term human well-being and sustainable development.
  • It was established in Panama City, on 21 April 2012 by 94 Governments.
  • It is not a United Nations body.
  • However, at the request of the IPBES Plenary and with the authorization of the UNEP Governing Council in 2013, the United Nations Environment Programme (UNEP) provides secretariat services to IPBES.
  • The work of IPBES can be broadly grouped into four complementary areas:
  • Assessments
  • Policy Support
  • Building Capacity & Knowledge:
  • Communications & Outreach


Wealth Accounting and the Valuation of Ecosystem Services


  • It is a World Bank-led global partnership that aims to promote sustainable development by ensuring that natural resources are mainstreamed in development planning and national economic accounts.
  • WAVES is now part of the broader World Bank umbrella initiative, the Global Program for Sustainability (GPS).
  • This global partnership brings together a broad coalition of UN agencies, governments, international institutes, nongovernmental organizations and academics to implement Natural Capital Accounting (NCA) where there are internationally agreed standards, and develop approaches for other ecosystem service accounts.
  • WAVES was launched at the 2010 Convention on Biological Diversity meeting in Nagoya, Japan
  • Objectives
  • Help countries adopt and implement accounts that are relevant for policies and compile a body of experience
  • Develop approaches to ecosystem accounting methodology
  • Establish a global platform for training and knowledge sharing
  • Build international consensus around natural capital accounting


The Economics of Land Degradation (ELD)

  • Initiative is a global collaboration to evaluate and raise awareness on the economic benefits of land and land based ecosystems.
  • Economics of land degradation describes a holistic approach for estimates of the total economic valuation of land and land based ecosystems.
  • The ELD approach covers economic, social and environmental factors as well as the costs and benefits of sustainable land management.
  • The ELD Initiative highlights the value of land and its services through research, capacity development, and active knowledge exchange.


  • Biological community in an area or ecosystem is a complex network of interactions. The interaction that occurs among different individuals of the same species is called intra-specific interaction, while the interaction among individuals of different species in a community is termed as inter-specific interaction.
  • Interactions between organisms belonging to the same trophic level often involve competition. Individuals of a population may compete for food, space and mates.
  • For example if a mouse has been eaten by a cat, other cats competing for this resource would have one less mouse to prey on. The snake another predator of the mice would also have fewer mice to eat during the night if the cat has succeeded.
  • Direct competition, though, between the cat and snake is not much as they both prey at different times. They also eat a variety of different foods. So it may be intra-specific as well as inter-specific.
  • Inter-specific relationship may be direct and close as between a lion and deer or indirect and remote as between an elephant and a beetle. This is because interactions between two species need not be through direct contact.
  • Due to the connected nature of ecosystems, species may affect each other through intermediaries such as shared resources or common enemies. Specific terms are applied to inter-specific interactions depending upon whether the interaction is beneficial, harmful or neutral to individuals of the species.
  • Interactions may be of various kinds:




It is a negative association between two species in which one species harms or restricts the other species without itself being adversely affected or harmed by the presence of the other species.

  • Organisms that secrete antibiotics and the species that get inhibited by the antibiotics, together form example of amensalism.
  • For example the fungus called bread mould or Pencillium produces penicillin, an antibiotic, which inhibits the growth of a variety of bacteria. Pencillium benefits apparently by having greater availability of food when in the competition bacteria are removed.



  • In this type of interaction, predator captures, kills and eats an animal of another species, called the prey.
  • In this interaction one species benefits and the other is harmed.
  • The predator benefits from this relationship; while the prey is harmed. Examples: leopards, tigers, cheetahs etc.



  • In this interaction, one species is harmed and the other benefits.
  • It involves small sized organisms or parasites living in or on another living species called the host from which the parasite gets its nourishment and often shelter. The parasite is benefited and the host is harmed.
  • Organisms: bacteria and viruses are parasites of plants and animals.
  • Plants: dodder plant (Cuscuta) and mistletoe (Loranthus) are parasites that live on flowering plants. Tape worm, round worm, malarial-parasite, bacteria, fungi, and viruses are common parasites of humans.



It is an interaction between two populations in which both species are harmed to some extent.

  • Competition occurs when two populations or species, both need a vital resource that is in short supply.
  • The vital resource could be food, water, shelter, nesting site, mates or space.
  • Such competition can be:
  • inter-specific competition-occurring between individuals of two different species occurring in a habitat and
  • intra-specific competition-occurs between individuals of same species. Intra-specific competition occurs between members of the same species and so it is very intense.



  • In this relationship one of the species benefits while the other is neither harmed nor benefited.
  • Some species obtain the benefit of shelter or transport from another species.

For example: sucker fish, remora often attaches to a shark by means of its sucker which is present on the top of its head.

  • This helps remora get protection, a free ride as well as a meal from the left over of the shark’s meal.
  • The shark does not however get any benefit nor is it adversely affected by this association.
  • Another example of commensalism is the relationship between trees and epiphytic plants.
  • Epiphytes live on the surface of other plants like- ferns, mosses and orchids and use the surface of trees for support and for obtaining sunlight and moisture.
  • The tree gets no benefit from this relationship Health nor are they harmed.



  • It is a close association between two species in which both the species benefit.
  • However, some interacting species can no longer live without each other as they depend totally on each other for survival. Such close associations are termed
  • An example of such close mutualistic association is that of pollination of flowers where flowering plants are cross pollinated by the bees which benefit by getting nectar from the plants. Both cannot survive without the other.



  • Neutralism describes the relationship between two species which do interact but do not affect each other.
  • It is to describe interactions where the fitness of one species has absolutely no effect what so ever on that of other.
  • True neutralism is extremely unlikely and impossible to prove. When dealing with the complex networks of interactions presented by ecosystems, one cannot assert positively that there is absolutely no competition between or benefit to either species. Since true neutralism is rare or non-existent, its usage is often extended to situations where interaction are merely insignificant or neglible.




  • Every organism in this world has ability to adapt to changes to its surroundings which allows it to tolerate small changes in its environment such as changes in temperature, humidity etc.
  • Every species has a specific range within which it can tolerate ecological changes. This range is called ecological amplitude.


There are three broad responses within this ecological amplitude:

  • Ecophene: Also known as ecads or morphologically changed forms, ecophenes are variation in phenotypes (observable physical characteristics) present in characteristics of the population. For example an European living in Africa will have different feature (e.g higher melanin in skin) than one living in Europe.
  • Ecophenes occur when a species is transported to a new environment as a result it develop abilities to adapt to new environment.
  • The differences among ecophenes are just temporary morphological variation (body of organism assume it is going to be in new condition on for short time) and is reversible as there is no change in genetics of two separate ecophenes.
  • g. If the European living in Africa goes back to Europe, he will start loosing the melanin content of his skin and will start becoming fairer.
  • Ecotype: These are plant and animal species which are well adapted to local environment conditions.
  • Ecotypes occur when ecophenes remain in their new environment for too long as a result morphological changes becomes genetically fixed. As a result these morphological changes are permanent. However interbreeding among two ecotypes to produce a viable offspring is possible.
  • For example the grass Euphorbia hirta has two ecotypes – one which is permanently adapted to survive in moist conditions while the other is adapted to survive in dry conditions.
  • Ecospecies: Among animal or plant of some species are kept separate environment for a very long time the adaptations becomes permanent part of the genes. As a result both morphological and genetic variation is now permanent. Hence although these belong to same species, they are physically and genetically very distinct and hence known as Ecospecies.
  • Two eco species cannot interbred to produce viable off-springs. These species when left alone for many generations develop sufficient changes to become a separate species.


Ecological Footprint


  • The idea of ecological footprint was first conceived by Mathis Wackergenal and William Rees in 1990.
  • Ecological footprint is a resource accounting tool which measures how fast we consume resources and produce waste in comparison to how fast nature generate new resources and absorb our waste.. It is the only metric that measures nature we humans have and how much nature we use.
  • On demand side it measures the ecological assets which a given population requires to produce the natural resource it consumes (e.g food crops, fish products etc.) and to absorb its waste such as carbon emissions.
  • On supply side a region’s ( e.g. city, state, nation etc.) biocapacity represent the productivity of its ecological assets including cropland, grazing land, forest land etc.


 Biocapacity is ecosystems’ capacity to produce biological materials used by people and to absorb waste material generated by humans, under current management schemes and extraction technologies


  • Both ecological footprint and biocapacity is expressed in terms of global hectares (gh). If ecological footprint exceeds region’s bio capacity ,the region is said to be ecological deficit . A region is said to have ecological reserve if its biocapacity exceeds its ecological footprint.
  • Earth Overshoot occur when entire planet is running on ecological deficit. Earth Overshoot marks the day when humanities demand for ecological resources and services in a given year exceeds what Earth can regenerate in that year.
  • Earth Overshoot day is hosted and calculated by Global Footprint Network. In 2020 Earth Overshoot day fell on August 22. This included the impact of coronavirus Pandemic


(Earth’s Biocapacity Humanity’s Ecological Footprint) x 365 = Earth Overshoot Day


  • Not all countries have overshoot day. A country will have overshoot day only if their ecological foot print per person is higher than global biocapacity.


Significance of Ecological Footprint

  • It is widely used by countries to improve sustainability and well-being and by individuals to understand impact on the planet.
  • Helps in resource optimization and prevents wastage of resources.
  • Environmental educators and activits have used this footprint to raise awareness and push changes in current lifestyles which is harming the environment.


What is current Ecological footprint?

  • According to currently available data average per-person Ecological Footprint worldwide is of 2.8 gha in 2016 while the available earth’s biocapacity stood at 1.6 gha. .
  • This means that overall humanity’s demand for good and services from ecological ecosystem is currently 75% higher than what earth can renew today.
  • Carbon Footprint accounts for 60% of current Ecological Footprint of Humanity.
Why we have been able to survive even if our footprint is larger?

Ø  Not everyone is having equal access to resources.

Ø  We at present are consuming resources of their future generation. e.g. By our high water consumption we are consuming water supposed to be available for our future generation.


Ecological footprint of India

  • India’s current ecological footprint is 1.2 gha (global hectare) while Biocapacity is 0.4 gha. Hence India has an ecological deficit of 0.8 gha.
  • This means that our footprint is 200% more than the area of the country

Causes behind increasing ecological footprint

  • Increasing world population: Earth population has increased by 7 fold in last 200 years. While it stood around 1 billion in 1800s ,it was 7 billion in 2019.
  • Rising global consumption: e.g in last 50 years global meat consumption has quadrupled The world now produces more than 320 million tonnes of meat every year.
  • Poor resource management causing high wastage of resources.
  • Increased reliance on fossil fuels in past Still fossil fuel comprise of majority of the energy share of world energy. This has caused concentration of carbon dioxide in atmosphere.


Carrying Capacity


  • Carrying capacity of an eco-system is the maximum population size of a biological species that an eco-system could sustain indefinitely within its natural resource limits.
  • When population exceeds carrying capacity of an ecosystem, death and destruction occur.
  • How carrying capacity of an environment puts a natural constraints on population size of a species can be understood from following example. Suppose there is a tremendous rise of deer population, say 500 deer in a forest with carrying capacity of 100, then this will burden the forest resource needed for the deer. The deer will have to face high competition for food and space which reduces the survival chances of many of the off springs and will slowly bring the population size to 100.
  • The carrying capacity of an area is not static. It can be reduced or increased. For example the resource capacity of an area decreases during an overshoot period while it increases due to technological and social changes.
  • Factors affecting carrying capacity of an ecosystem includes disease, competition, pre-dator prey interaction, resource utilization, population of species within the eco system.


What is Tourism Carrying Capacity?


World Tourism Organization defines Tourism carrying capacity as “the maximum number of people that may visit a tourist destination at the same time, without causing destruction of the physical, economic, sociocultural environment and an unacceptable decrease in the quality of visitors’ satisfaction”


Need for sustainable Tourism in Himalayas 


Tourist arrivals in the Indian Himalayan States are projected to reach 240 million by 2025, which is 2.5 times the current tourist arrivals at 100 million

Ø  Indian Himalayan region is hosts site for both pilgrimage tourism (e.g. Vaishno devi & Kedarnath) and modern tourism e.g Shimla, Valley of flowers etc.

Ø  The current tourism in Indian Himalayan Region replaces traditional eco-friendly and aesthetic architecture with inappropriate, non-aesthetic and often dangerous constructions, and compound other challenges such as

o   poorly designed roads and associated infrastructure,

o    inadequate solid waste management accompanied by tonnes of trash left by tourists crowd.

o   air pollution, degradation of watersheds and water sources,

o   loss of natural resources, biodiversity, and ecosystem services. E.g Uttarakhand lost 268 sq Km of forests due to tourism related development.

Ø  Mass tourism is already causing ecological degradation and adversely impacting cultural fabric and social values of collectivism which were historically hallmarks of mountain communities


What need to be done:

Ø  Assessment of the carrying capacity of tourist destinations across existing and potential tourism sites.

Ø  developing, implementing and monitoring tourism sector standards (e.g., hospitality, hotel and tour operators compliance standards)

Ø  cess or higher user charges/levies on service providers and consumers

Ø  Smart Mountain Tourism Destinations” could be prepared on the lines of Smart Cities and the private sector encouraged to invest in responsible tourism

Ø  Environmental auditing – based on environmental efficiency, carbon footprint and certification – that is part of eco-labelling, can enhance the application of social and environmental safeguards in the tourism industry.


Relevance of Carrying Capacity


  • Economic Planning through development of strategies for optimal utilization of resources and reducing their adverse impact on environment.
  • Population control within a region.
  • Conservation of Biodiversity: Maintaining the population of species within carrying capacity is needed for avoid issues like man animal conflict, destruction of forest resources etc.
  • Planning Food Security: Population increase will cause spike in food consumption which will impact the availability food. Increase in population of one species beyond carrying capacity will adversely impact food availability of others.
  • g. Increase in population of elephants beyond carrying capacity will not only reduce food availability for them in forest but also cause raiding on crop fields which will destroy food grains available for human consumption.
  • In agricultural and water management by using micro irrigation techniques such as drip irrigation , sprinkler irrigation techniques, water storage structure and switching from high water intensive crops to drought resistant crops in low rainfall regions.
  • In Disaster Management such as development of adequate swage and drainage mechanism in urban areas, assessing capacity of flood plains over human encroachment in the areas.

1.      The states of Jammu and Kashmir, Himachal Pradesh and Uttarakhand are reaching the limits of ecological carrying capacity due to tourism. Critically evaluate.  (2015)

2.      Define the concept of carrying capacity of an ecosystem as relevant to an environment. Explain how understanding this concept is vital while planning for sustainable development of a region. (2019)


Planetary Boundaries


  • The concept of planetary boundaries was first introduced in 2009 to define environmental limits within which humanity can operate safely and continue to develop and thrive for generations to come.
  • Crossing these boundaries increases the risk of large scale abrupt and irreversible environmental changes.
  • Stockholm Resilience Centre quantified nine Planetary boundaries within which humanity can thrive for generation to come. These boundaries include:
  • Climate change
  • Change in biosphere integrity (biodiversity loss and species extinction)
  • Stratospheric ozone depletion
  • Ocean acidification.
  • Biogeochemical flows (phosphorus and nitrogen cycles)
  • Land-system change (for example deforestation)
  • Freshwater use
  • Atmospheric aerosol loading (microscopic particles in the atmosphere that affect climate and living organisms)
  • Introduction of novel entities (e.g. organic pollutants, radioactive materials, nano-materials, and micro-plastics).
  • According to a latest research published in journal Science Four of nine planetary boundaries have now been crossed as a result of human activity.
  • The four are: climate change, loss of biosphere integrity, land-system change, altered biogeochemical cycles (phosphorus and nitrogen).
  • Two of these boundaries i.e. Biosphere integrity and climate change are refereed as core boundaries by the scientists .The altering of these core boundaries will drive Earth System into a new state.
  • Planetary boundaries become significant as it can aid decision makers by defining safe operating space for humanity.