In this article, I want to walk you through the Terrestrial Ecosystem for the UPSC exam.
Terrestrial ecosystems are distinguished from aquatic ecosystems by the lower availability of water and the consequent importance of water as a limiting factor.
Terrestrial ecosystems are characterized by greater temperature fluctuations on both a diurnal and seasonal basis than occur in aquatic ecosystems in similar climates, because water has a high specific heat, a high heat of vaporization, and a high heat of fusion compared with the atmosphere, all of which tend to ameliorate thermal fluctuations.
The availability of light is greater in terrestrial ecosystems than in aquatic ecosystems because the atmosphere is more transparent than water. Gases are more available in terrestrial ecosystems than in aquatic ecosystems. Those gases include carbon dioxide that serves as a substrate for photosynthesis, oxygen that serves as a substrate in aerobic respiration, and nitrogen that serves as a substrate for nitrogen fixation.
Terrestrial environments are segmented into a subterranean portion from which most water and ions are obtained, and an atmospheric portion from which gases are obtained and where the physical energy of light is transformed into the organic energy of carbon-carbon bonds through the process of photosynthesis.
Terrestrial ecosystems are –
Forests are large areas supporting the rich growth of trees. Depending on the climate and type of trees they are generally grouped into:
- Tropical rain forests
- Temperate deciduous forests
- Boreal or north coniferous forests
Tropical Rain Forest
Distribution: These are found in the high rainfall areas on either side of the equator. Such forests are found on the western coast of India, scattered in southeast Asia, some parts of Africa and South America.
Climate: Tropical rainforests occur in areas by having high temperature and high humidity and receives above 200 cm of rainfall per year. Soil is rich in humus.
Flora and fauna: These forests have a very rich biodiversity e.g. Brazilian tropical rain forests have more than 300 species of trees in an area of 200 square kilometers. Trees are tall growing up to 50 to 60 m. These forests also support epiphytes, like vines, creepers, woody creepers and orchid, etc. These forests are rich in tree-dwelling animals such as monkeys, flying squirrels, snails, centipedes, millipedes, and many insect species that are common on the forest floor.
Temperate Deciduous Forests
Distribution: They occur mostly in northwest, central and eastern Europe, eastern North America, north China, Korea, Japan, far eastern Russia and Australia. Trees of deciduous forests shed their leaves in autumn and new foliage grows in spring.
Climate: These forests occur in the areas of moderate climatic conditions such as temperature range but 10 to 20oC with a 6-month long winter and an annual rainfall between 75 to 150 cm. They have their brown soils that are rich in nutrients.
Flora and fauna: Common trees are oak, beech, heath, chestnut, birch, pine. These forests also show stratification and have an understory of saplings shrubs and tall herbs. Prominent grazers include deer, bison and rodents. Rodents play a very important role in these forests. They feed on seeds, fruits and tree leaves. Black bears, raccoons, wild cats, wolves, fox and skunks are the omnivores found in these forests. Hibernation or winter sleep during winter is a common feature of animals found in these forests. Invertebrate fauna comprises green flies, aphids, certain moths and butterflies.
Boreal or North Coniferous Forests
Distribution: Coniferous forests are also known as ‘Taiga’. They extend as a continuous belt across North America and northern Eurasia below the arctic tundra. There is no counterpart of these forests in the southern hemisphere as there is no land at this latitude.
Climate is cold with long, harsh winter, with a mean annual temperature below 00 C. The soils are acidic and poor in nutrients.
Flora and fauna: Coniferous forests are characterized by evergreen, drought-resistant and woody. Conifers (gymnosperms) e.g. spruce, fir and pine trees which bear naked seeds in cones. The animals found in these forests, are red squirrel, deer, goat, mule, moose, etc. The carnivores which feed upon them are timber wolves, lynxes, bear. Some common birds are crossbill, thrushes, warblers, flycatchers, robin and sparrow.
Importance of Forests
The early life of humans on this planet began as a forest dweller. In the early days humans were dependent on forests for food, clothing, and shelter.
Even after agriculture was started humans remained dependent upon the forests for several of their needs.
The source of fuelwood and provide raw materials to various wood industries.
Indian forests also provide many other valuable minor products such as essential oil, medicinal plants, resins, turpentine, etc.
Forests are renewable resources that provide a wide variety of commodities. Forests satisfying the aesthetic needs of humans and have been a source of inspiration for the development of culture and civilization.
Forests are home to a very large variety of plants, animals and micro-organisms. This great richness of flora and fauna which has evolved over the years is an important part of nature. Forests provide habitat and food as well as protection to wildlife species against extremes of climate.
Forests have great biological importance as reservoirs of genetic diversity apart from playing an important role in regulating the earth’s climate.
Deforestation is a very broad term, which consists of cutting of trees including repeated lopping, felling, and removal of forest litter, browsing, grazing and trampling of seedlings. It can also be defined as the removal or damage of vegetation in a forest to the extent that it no longer supports its natural flora and fauna.
The rapid rate of deforestation in the tropics is a key driving force in the yearly increase of flood disasters.
Deforestation refers to the loss of tree cover; land that is permanently converted from forest to non-forest uses such as agricultural pasture, desert, and human settlement.
Causes of Deforestation
The most common reason for deforestation is cutting of wood for fuel, lumber, and paper. Another important cause relates to the clearing of forest land for agriculture, including conversion to cropland and pasture.
The main causes of deforestation are:
The expanding agriculture is one of the most important causes of deforestation. Man has always modified the natural ecosystems in such a way that environment becomes more favorable for crop growth whether using traditional or modern methods of agriculture.
As demands for agricultural products rise, more and more land is brought under cultivation and for that more forests are cleared, grasslands and even marshes, and lands under water are reclaimed.
Thus, there is much more ecological destruction than gain in terms of crop yield. The forest soil after clearing is unable to support farming for long periods due to exhaustion of nutrients. Once the soils become unfit for cultivation, the area suffers from soil erosion and degradation.
Hunting and gathering has been the main form of sustenance practiced in the earlier periods of human history. Shifting cultivation or Jhoom farming is a 12000-year old practice and a step towards the transition from food collection to food production.
It is also known as the slash-and-burn method of farming. Annually about 5 lakhs ha (hectares) of forest is cleared for this type of farming. In this type of cultivation there is a limited use of tools with the not very high level of mechanization.
However, this method of cultivation causes extreme deforestation, as, after 2-3 years of tilling, the land is left to the mercy of nature to recover.
This type of cultivation was always meant to fulfill local needs or onsite demands to meet the requirements of the cultivating villagers. Even today, shifting cultivation is practiced in the states of Assam, Manipur, Meghalaya, Mizoram, Nagaland, Tripura and Andaman and Nicobar Islands.
Demand for firewood
Firewood has been used as a source of energy for cooking, heating, etc. Almost 44% of the total global wood produced fulfills the fuel requirements of the world. A close look at the pattern of utilization of wood produced will show that the developed countries utilize 16% of their share for fuel requirements. India consumes nearly 135-170 Mt (Million tonnes) of firewood annually and 10-15 ha of forest cover is being stripped off to meet the minimum fuel needs of urban and rural poor.
Wood for industry and commercial use
Wood, the versatile forest produce, is used for several industrial purposes, such as making crates, packing cases, furniture, matchboxes, wooden boxes, paper and pulp, plywood, etc. 1.24 lakh ha of forest have been cut for various industrial uses.
Unrestricted exploitation of timber, as well as other wood products for commercial purposes, is the main cause of forest degradation. The paper industry accounts for about 2% of the country’s annual consumption of wood and 51% this requirement is met by bamboo wood. This has led to the depletion of bamboo stocks in most of the peninsular India.
For example, the apple industry in the Himalayan region has led to the destruction of fir and other tree species, for making wooden boxes used for transporting apples. Similarly, plywood crates were used for packing particularly tea and other produce.
Urbanization and developmental projects
Often urbanization and developmental activities lead to deforestation. The process of deforestation begins with the building of infrastructure in the form of roads, railway lines, the building of dams, townships, electric supply, etc. Thermal power plants, mining for coal, metal ores and minerals are also important causes of deforestation.
Another example would be forest blazes; Hundreds of trees are lost each year due to forest fires in various portions of the world. This happens due to extreme warm summers and milder winters. Fires, whether caused by man or nature resulting in a huge loss of forest cover.
Effects of Deforestation
Deforestation also affects the climate in more than one way. Trees release water vapor in the air, which is compromised with the lack of trees. Trees also provide the required shade that keeps the soil moist.
This leads to the imbalance in the atmospheric temperature further making conditions for the ecology difficult. Flora and fauna across the world are accustomed to their habitat. This haphazard clearance of forests has forced several of these animals to shift from their native environment. Due to this several species are finding it difficult to survive or adapt to new habitats.
Increase in Global Warming
Trees play a major role in controlling global warming. The trees utilize the greenhouse gases, restoring the balance in the atmosphere. With constant deforestation the ratio of greenhouse gases in the atmosphere has increased, adding to our global warming woes.
Also due to the shade of trees the soil remains moist. With the clearance of tree cover, the soil is directly exposed to the sun, making it dry.
When it rains, trees absorb and store a large amount of water with the help of their roots. When they are cut down, the flow of water is disrupted and leads to floods in some areas and droughts in others.
Due to the massive felling down of trees, various species of animals are lost. They lose their habitat and forced to move to a new location. Some of them are even pushed to extinction. Our world has lost so many species of plants and animals in the last couple of decades.
Strategies to Reduce Deforestation
- Reduce population growth and increasing per capita incomes
- Reducing emissions from deforestation and forest degradation (REDD and REDD+)
- Increase the area and standard of management of protected areas
- Increase the area of forest permanently reserved for timber production
- Increase the perceived and actual value of forests
- Promote sustainable management
- Encouraging substitutes
- Increase area of forest plantation
- Strengthen government and non-government institutions and policies
- Participatory forest management and rights
- Increase investment in research, education and extension
- Improve the information base and monitoring
- Policy, legislative and regulatory measures-enforcement and compliance
Distribution: Grasslands are areas dominated by grasses. They occupy about 20% of the land on the earth surface. Grasslands occur both in tropical and temperate regions where rainfall is not enough to support the growth of trees. Grasslands are known by various names in different parts of the world.
|Place||Name of the|
|Eurasia (Europe and Asia)||Steppes|
Grasslands are found in areas having well defined hot and dry, warm and rainy seasons. Tropical grasslands are commonly called Savannas. They occur in eastern Africa, South America, Australia and India. Savannas form a complex ecosystem with scattered medium-size trees in grasslands.
Flora and fauna: Grasses are the dominating plants with scattered drought resistant thorny trees in the tropical grasslands. Badgers, fox, ass, zebra, antelope are found grazing on grasslands support the dairy and leather industries. Grasslands also support a large population of rodents, reptiles and insects.
Importance of grassland
They provide forage for grazing animals and thus make vegetation suitable for human consumption. Animals transform vegetation and produce e.g. milk, meat and wool for human consumption and use.
They have developed a natural environment of vegetations where medicinal plants and herbs are collected and used for human consumption.
Their surface cover protects life-giving soils and croplands from the harmful effects of natural disasters and human intervention, erosion and deflation.
They provide a natural environment for smaller-larger animal species living on them, maintaining and ensuring the potentials of biodiversity.
They keep not only surface soils, but croplands in suitable conditions, as well. Grasses are specially related to soils: dead plant residues generate humus, which promotes the formation of different soil structures. The fibrous root system of grasses directly advances the formation of soil structures.
In our direct human environment, they contribute to “human aesthetics” and relaxation. A beautiful lawn enhances the friendliness of our environment, the value of the scenery that we directly see.
They are natural areas for doing sports, recreation activities (e.g. football fields) by the construction of manmade sports grounds in urban areas or by transforming the natural environment (golf courses).
In the form of a naturally generated “biomass” or established culture (energy grass), they are renewable energy sources for humans.
They directly ensure numbers of entrepreneurs (enterprises) enough to live on, as entrepreneurs produce (grass) seeds or give advice on grasses.
Impact of grazing
Due to heavy grazing pressure, the quality of grasslands deteriorates rapidly, the mulch cover of the soil reduces, microclimate becomes drier and is readily invaded by xerophytic plants.
Due to the absence of humus cover, mineral soil surface is heavily trampled when wetness produces puddling of the surface layer. In turn it reduces the infiltration of water into the soil and accelerates its runoff, producing drought.
These changes contribute to the reduction of energy flow and the disruption of the Stratification and periodicity of the primary products. It results in a breakdown of the biogeochemical cycles of water, carbon and nitrogen.
Water and wind erosion completely deteriorates dry grassland microclimate.
Intensive grazing results in increasing areas of bare soil, which creates a new habitat for burrowing animals such as mice, jackrabbits, gophers, prairie dogs, locusts etc., which render large areas of forage lands sterile.
Distribution: Deserts are hot and low rain areas suffering from water shortage and high wind velocity. They show extremes of temperature. Globally deserts occupy about 1/7thof the earth’s surface.
Flora and fauna: Cacti, Acacia, Euphorbia and prickly pears are some of the common desert plants. Desert animals include shrew, fox, wood rats, rabbits, camels and goats are common mammals in the desert. Other prominent desert animals are, reptiles, and burrowing rodents insects.
Adaptations: Desert plants are hot and dry conditions.
These plants conserve water by following methods:
- They are mostly shrubs.
- Leaves absent or reduced in size.
- Leaves and stems are succulent and water storing.
- In some plants even, the stem contains chlorophyll for photosynthesis.
- Root systems well-developed spread over a large area.
The animals are physiologically and behaviorally adapted to desert conditions.
- They are fast runners.
- They are nocturnal in habit to avoid the sun’s heat during day time.
- They conserve water by excreting concentrated urine.
- Animals and birds usually have long legs to keep the body away from the hot ground.
- Lizards are mostly insectivorous and can live without drinking water for several days.
- Herbivorous animals get sufficient water from the seeds which they eat.
It can be defined as ‘the diminution or destruction of the biological potential of the land which can ultimately lead to desert-like conditions’.
The arid and semi-arid areas where the climate is dry, restoration is very slow, mining and overgrazing, etc. adds to several other desertification pressures. Desertification is a systemic phenomenon resulting from excessive felling of trees which manifests itself in the loss of soil fertility, high wind velocity, low precipitation, increasing aridity and extremes of temperatures in the affected area.
Desert supports very little vegetation and animals which are specially adapted to extremely unfavorable conditions. Although desertification can develop from natural causes alone, in a majority of instances human intervention promoted arid conditions in an already dry area.
This can happen in any climatic zone or ecosystem, resulting from exploitative interaction of man with the natural ecosystem. Most of the deserts of recent origin have resulted from any one or more of the following human activities.
- Uncontrolled and overexploitation of grazing land, indiscriminate cutting of trees and forest resources leading to drought, soil erosion, deterioration of soil fertility which results in stunted plant growth.
- Excessive mining in arid and semi-arid regions for extraction of minerals, coal or limestone resulting in loss of trees, and green cover, and leading to the destruction of conditions conducive to vegetation growing.
- Uneconomic land use for agriculture by cultivation on marginal lands affecting adjacent fertile lands and causing soil erosion.
- Intensive and uneconomic exploitation of water resources leading to fall in the water table, seepage and problems of excessive salinization of soil.
Extent of desertification
About 76.15% of the total Indian desert area has resulted from a manmade desertification process. Another 19.5% of the total area is subjected to medium or slight desertification. This area is concentrated mostly along the eastern Rajasthan in the north-east to the southwest zone parallel to the foothills of Aravalis.
Most of the deserts, in India, are found in the states of Rajasthan and Western Gujarat, where about 23.8 mha area has been affected by desertification. About 4.34% of this area lies in the extreme West of Rajasthan in Jaisalmer district. This desert is concentrated along a belt in Ganganagar, Churu, Bikaner, Jaisalmer, Barmer, Jodhpur, Jalore, Jhunjhunu and Nagaur districts. The predominant processes of desertification in this belt are the expansion of sand cover and shifting sand dunes by wind erosion.
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.
Distribution: Arctic tundra extends as a continuous belt below the polar ice cap and above the tree line in the northern hemisphere. It occupies the northern fringe of Canada, Alaska, European Russia, Siberia and island group of arctic oceans. On the South Pole Antarctica tundra in the South Pole is very small since most of it is covered by ocean. Alpine tundra occurs at high mountains above the tree line. Since mountains are found at all latitudes therefore alpine tundra shows day and night temperature variations.
Flora and fauna: Typical vegetation of arctic tundra is cotton grass, sedges, dwarf heath, willows, birches and lichens. Animals of tundra are reindeer, musk ox, arctic hare, caribou, lemmings and squirrel.
Most of them have long life e.g. Salix Arctica that is arctic willow has a life span of 150 to 300 years. They are protected from the chill by the presence of thick cuticle and epidermal hair. Mammals of the tundra region have large body sizes and small tail and ear to avoid the loss of heat from the surface. The body is covered with fur for insulation. Insects have short life cycles that are completed during a favorable period of the year.
Reference: Shankar IAS Book (Environment)