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Term Paper # 1. Introduction to Biomes:
The climate zones have their own characteristic environmental conditions. In a given climatic condition, specific types of biotic (living) and non-biotic (non-living) groups can exist in harmonious relations amongst the three, to make up, what is known as environment. An ecosystem is a geographical area of a variable size where plants, animals, the landscape and the climate all interact together.
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Within an ecosystem, organisms occupy areas, where physical conditions, especially climate factors such as light, heat, moisture and wind are most appropriate to cater to their needs. These areas are called habitats.
The communities of plants and animals occupying major geographical areas, (continental or sub continental in scale), that retain sufficient similarities of form and function, that are recognized as ecosystems, are called biomes. Biomes are defined as “the world’s major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment”. A biome can be thought of many similar ecosystems throughout the world grouped together. An ecosystem can be as large as the Sahara Desert, or as small as a puddle or vernal (temporary) pool.
A biome is usually considered to have the attributes of climax community – a community that represents the most developed combination of plants and animals possible under the environmental conditions at a given time in a given area. The biomes are dynamic entities, and can retain the equilibrium to a considerable degree of variations in environmental conditions such as those occurring during seasonal changes.
However, prolonged environmental disruptions, such as, that caused by climate change or fire, may alter a specific ecosystem irreversibly and bring a system with different characteristics. As a result maps of biomes only represent the period in which it has been in existence but surely not the current scenario.
If the remaining biomes are to be protected and preserved, and the projected changes threatened by global warming are to be managed, it is important to know what currently exists and what might be expected to come in a particular area. Biomes are responsible for keeping the ecological balance and maintaining of optimum quantities of carbon dioxide in the atmosphere and the climate. Hence they need to be preserved.
Term Paper # 2. Types of Biomes:
There is no accepted classification of biomes. However biomes are commonly divided into terrestrial, fresh water and marine groups. The four major terrestrial biomes consisting of deserts, forests, grassland and tundra can be further subdivided into around 10 more biomes (table 6.1). On land, biomes are separated primarily by latitude.
A biome contains a large area with similar flora, fauna, and microorganisms. The familiar tropical rainforests, tundra in the arctic regions, and the evergreen trees in the coniferous forests, belong to one or other of large communities containing species that are adapted to its varying conditions of water, heat, and soil. For instance, polar bears thrive in the arctic while cactus plants have a thick skin to help preserve water in the hot desert.
The six biomes and their characteristic features are as follows:
1. Freshwater:
Freshwater is defined as water with low salt concentration (<1%). Plants and animals growing in this biome would not survive in sea water with high salt content.
The three different types of freshwater regions include:
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(i) Ponds and lakes
(ii) Streams & rivers and
(iii) Wetlands.
(i) Ponds and Lakes:
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Small ponds to big lakes are scattered throughout the Earth. Many ponds are seasonal, while lakes may exist for hundreds of years or more. Ponds and lakes may have limited species diversity since they are often isolated from one another and from other water sources like rivers and oceans. Three different zones of ponds and lakes differ in features and species.
The topmost zone near the shore known as the littoral zone is shallow and warmest. This zone has a fairly diverse community, such as, several species of algae (like diatoms), floating aquatic plants, snails, clams, insects, fishes, and amphibians. The plants and animals in the littoral zone become food for creatures such as turtles, snakes, and ducks.
The near-surface open water surrounded by the littoral zone is an important zone, known as, limnetic zone. The limnetic zone is also well-lighted and is dominated by plankton, both phytoplankton and zooplankton. Phytoplanktons play a crucial role in the food chain by producing food (carbohydrates) through photosynthesis. Planktons are thus net absorbers of carbon dioxide from the atmosphere.
Planktons have short life spans and the dead ones fall into the deep-water part of the lake/pond, the profundal zone. This zone is cooler and denser than the other two, with very little light. The fauna are heterotrophs, meaning that they eat dead organisms and use oxygen for cellular respiration.
Temperature varies in ponds and lakes seasonally. In tropical regions, the temperature at the top in summer can be as high as outside temperature of up to 35° C, with some cooling effect due to evaporation, while the bottom can remain cool at 18° C to 10° C. In between the two layers, there is a narrow zone called the thermocline where the temperature of the water changes rapidly.
(ii) Streams and Rivers:
These are bodies of flowing water moving in one direction, from their starts at headwaters, which may be springs, snowmelt or even lakes, and then travel all the way to their mouths, usually another water channel or the ocean. The cool, clear water, with high oxygen levels at the source lead to freshwater fish such as trout and heterotrophs to survive in this region.
At the middle part of the stream/river, the width increases along with species diversity. Numerous aquatic green plants and algae can be found in this area. Toward the mouth of the river/stream, the water becomes murky from all the sediments that it has picked up upstream, decreasing the amount of light that can penetrate through the water. With less light, there is less diversity of flora, and lower oxygen levels allows fish that require less oxygen, such as catfish and carp, to survive.
(iii) Wetlands:
Wetlands are areas of standing water that support aquatic plants. Marshes, swamps, and bogs are all considered wetlands. Plant species adapted to the very moist and humid conditions are called hydrophytes. These include pond lilies, cattails, sedges, tamarack, and black spruce. Marsh flora also includes such species as cypress and gum. Wetlands have the highest species diversity of all ecosystems.
Many species of amphibians, reptiles, birds (such as ducks and waders), and furbearers can be found in the wetlands. Wetlands are not considered freshwater ecosystems as there are some, such as salt marshes, that have high salt concentrations, supporting different species of animals, such as shrimp, shellfish, and various grasses.
Wetlands are found to be useful in:
i. Controlling floods,
ii. Contributing to biological processes for natural resources, pollination by insects, birds, and mammals, and
iii. The most important function concerning global warming is regulating the climate by forests and open space through oxygen production and carbon dioxide consumption.
Freshwater biomes have suffered mainly from pollution. Runoff containing fertilizer and other wastes and industrial dumping enter into rivers, ponds, and lakes and tend to promote abnormally rapid algae growth. When these algae die, dead organic matter accumulates in the water. This makes the water unusable and it kills many of the organisms living in the habitat. Stricter laws have helped to slow down this thoughtless pollution.
2. Marine:
Marine regions cover about three-fourths of the Earth’s surface and include oceans, coral reefs, and estuaries. Marine algae supply much of the world’s oxygen supply and take in a huge amount of atmospheric carbon dioxide. The evaporation of the seawater provides rainwater for the land.
Marine regions consist of followings:
i. Oceans.
ii. Coral reefs.
iii. Estuaries.
i. Oceans:
The largest of all the ecosystems, oceans are very large bodies of water that dominate the Earth’s surface. The oceans regions have been divided in several separate zones (fig.6.0). All zones have great diversity of species. The ocean probably has the richest diversity of species with lesser number than on land.
The characteristic features of different zones are as follows:
a. Intertidal Zone:
Is where the ocean meets the land? This zone is either submerged and or exposed, by waves and tides. The submerged high tide area contains algae and small animals, such as snails, crabs, sea stars etc., while at the bottom of intertidal zone, exposed during lowest tides, fishes, & seaweed are found. In intertidal zone on sandy shores, waves keep mud and sand constantly moving, thus mostly found some fauna, such as worms, clams, crabs, and shorebirds.
b. Epipelagic Zone:
The epipelagic zone includes those waters further from the land, basically the open ocean. This surface layer is also called the sunlight zone and extends from the surface to 660 feet (200 meters). The solar heat is responsible for the wide range of temperatures that occur in this zone, both in different latitude and each season.
Surface temperature “follows the sun”. From the earth’s perspective, the sun’s position in the sky moves higher each day from winter to summer. This change in the sun’s position from winter to summer means that in summer more energy is reaching the ocean and therefore warms the water The sea surface temperature can be high at 97°F (36°C) in the Persian Gulf and low at 28°F (-2°C) near the north pole.
Interaction with the wind keeps this layer mixed and thus allows the heating from the sun to be distributed vertically. At the base of this mixing layer is the beginning of the thermocline (Fig.6.0.1). The thermocline is a region where water temperature decreases rapidly with increasing depth and transition layer between the mixed layer at the surface and deeper water.
The depth and strength of the thermocline varies from season to season and year to year. It is strongest in the tropics and decrease to non-existent in the polar winter season.
The flora found includes surface seaweeds. The fauna consists of many species of fish and some- mammals, such as whales and dolphins. Many feed on the abundant plankton.
c. Mesopelagic Zone:
This zone, also known as ‘twilight zone’ extends from 200 meters to 1000 meters (3281 ft.).The light that penetrates to this depth is very faint. In this zone the twinkling lights of bioluminescent creatures become visible. A great diversity of strange and bizarre fishes can be found here.
d. Bathypelagic Zone:
The next layer, also referred to as the midnight zone or the dark zone, extends from 1000 meters down to 4000 meters (13,124 ft.). Here the only visible light is that produced by the creatures themselves. The water pressure at this depth is immense, reaching 5,850 pounds per square inch. In spite of the pressure, a surprisingly large number of creatures can be found here. Sperm whales can dive down to this level in search of food. Most of the animals that live at these depths are black or red in color due to the lack of light.
e. Abyssopelagic Zone:
This zone, also known as the abyssal (in Greek means ‘no bottom’) zone, extends from 4000 meters to 6000 meters (19,686 ft.). Abyssal zone has high pressure, cold (around 3° C) water, contains high oxygen and poor nutritional value. The zone supports many species of invertebrates, such as basket stars and tiny squids, and fishes. Three-quarters of the ocean floor lies within this zone. The deepest fish ever discovered was found in the Puerto Rico Trench at a depth of 27,460 feet (8,372 meters).
f. Hadalpelagic Zone:
This layer extends from beyond 6000 meters to the bottom of the deepest parts of the ocean. These areas are mostly found in deep water trenches and canyons. The deepest point in the ocean is located in the Mariana Trench off the coast of Japan at 35,797 feet (10,911 meters). The temperature is just above freezing, and the pressure is an incredible eight tons per square inch. In spite of the pressure and temperature, life can still be found here. Invertebrates such as starfish and tube worms can thrive at these depths.
Mid-ocean ridges (spreading zones between tectonic plates), often with hydrothermal vents, are found in this zone along the ocean floors. Near these vents, chemosynthetic bacteria thrive on the large amounts of hydrogen sulfide and other minerals they emit, which ultimately become fodder for invertebrates and fishes.
Ocean and Carbon Dioxide Absorption:
Ocean removes carbon dioxide from the atmosphere by either absorption or photosynthesis by plants, algae and planktons. Oceans soak up around a quarter to one third of annual CO2 emissions but should they fail to do so in future, the gas would stay in the atmosphere and could accelerate the greenhouse effect.
Reveille’s works at Scripps Institute of Oceanography indicate that sea water surface layer has a limited capability of absorbing carbon dioxide, barely one-tenth of calculated buffering capacity. EU research project showed that the North Atlantic, which along with the Antarctic is one of the world’s two vital ocean carbon sinks, is absorbing only half the amount of CO2 as in the mid-1990s.
The more CO2 the oceans store, the more difficult it will be for them to take up the additional load from the atmosphere and carbon absorption will stagnate even further. Some forms of sea life have suffered from the large amounts of CO2 absorbed, because of changes in acidity levels, thus affecting biological process of carbon dioxide absorption negatively. Climate change may also affect the biological pump in the future by warming and stratifying the surface ocean, thus reducing the supply of limiting nutrients to surface waters.
ii. Coral Reefs:
Coral reefs are found in warm shallow waters, as barriers along continents (e.g., the Great Barrier Reef off Australia), fringing islands, and atolls. The dominant organisms in coral reefs are corals. Corals consist of both algae (zooanthellae) arid tissues of animal polyp. Since reef waters tend to be nutritionally poor, corals get nutrients through the algae via photosynthesis and also by extending tentacles to obtain plankton from the water. Besides corals, the fauna include several species of microorganisms, invertebrates, fishes, sea urchins, octopuses, and sea stars.
iii. Estuaries:
Estuaries are areas where freshwater streams or rivers merge with the ocean. The mixing of waters with different salt concentrations creates a unique ecosystem. Microflora like algae, and macroflora, such as seaweeds, marsh grasses, and mangrove trees (only in the tropics), can be found here. Estuaries support a diverse fauna, including a variety of worms, oysters, crabs, and waterfowl.
Over fishing and pollution have threatened to make oceans into ecological disaster areas. Industrial pollutants that are dumped upstream of estuaries have rendered unsuitable for survival of many marine habitats.
Role of Planktons in Global Warming:
Planktons, inhabitants of fresh water and marine biomes need a special mention, because of their unique properties in relation to global warming. Like plants they are both carbon dioxide absorber and producer of oxygen, a vital element for survival of living organisms. Each year, the North Atlantic Ocean announces springtime by producing “blooms” large enough to be seen from space. The latest development in oceanographic remote sensing, however, enables researchers to detect the glow, or phytoplankton fluorescence, from chlorophyll chain.
Planktons are primarily divided into broad functional groups, as follows:
i. Phytoplankton (from Greek phyton, or plant), includes different types of algae that live near the water surface where there is sufficient light to support photosynthesis. Among the more important types are the diatoms, cyanobacteria and dinoflagellates.
ii. Zooplankton (from Greek zoon, or animal), small protozoan or metazoans (e.g. crustaceans and other animals) that feed on other plankton and telonemia. Some of the eggs and larvae of larger animals, such as fish, crustaceans, and annelids, are included in this group.
iii. Bacterioplanktons are bacteria and archaea, which play an important role in remineralising organic material down the water column.
The planktons that make their own food by photosynthesis are called phytoplankton and those small-sized animals that cannot synthesize their own food but feed on organic food available is called zooplankton. The phytoplanktons, like the plants on land, are the primary producers, and the zooplankton (copepods, salps) that survives on phytoplankton, like the herbivorous animals on land are the primary consumers.
Carnivorous zooplankton and fish that feed on herbivorous zooplankton are the secondary consumers. Bacterioplaktons work as re-mineralising the water required for producing food by photosynthesis. Thus the plankton as a community consisting of three broad groups, such as, producer, consumer and recycler, has the capabilities of self-sustaining with the help of sunlight. Planktons are responsible for providing major food source for the sea animals including fishes.
Of the three types, phytoplanktons are the oldest of the known planktons. Scientists consider that the microorganisms originated around three and half billion years ago and can convert water, minerals, and carbon dioxide under sunlight into carbohydrates and oxygen as per following equation:
CO2 + H2O + nutrients + light = organic matter (C6 H12 O6) + O2.
The basic requirements for above reaction to occur are as follows:
i. Light is required for photosynthesis. The top 100-150 m of the ocean surface (photic or euphotic zone) as well as shallow water zones in the coastal areas (Fig.6.0) gets the required level of light intensity for photosynthesis. These zones are thus favorable for producing phytoplanktons.
ii. Mineral nutrients (nitrate, ammonium, phosphate, silicate and iron) are essential for the growth and multiplication of phytoplankton. The nutrient content in the top layer of the ocean is low; hence the above reaction is often limited by the supply of nutrients. However coastal regions are rich in both nutrients and sunlight encouraging the production of planktons.
Physical processes such as upwelling (a process in which cooler waters from below are brought up), hydrographic fronts (regions over which a property like temperature or salinity changes sharply in the horizontal), eddies and cyclones are responsible for bringing up nutrients from deeper waters to the surface, thus stimulating primary production of planktons.
iii. Source of carbon dioxide for planktons include:
(a) Absorption of CO2 from the atmosphere,
(b) Release through respiration of bacteria and animals, and
(c) Upwelling of CO2 from dissolved calcium carbonate in shells of benthic animals.
Although large areas of the tropical and sub-tropical oceans have abundant light, they experience relatively low primary production due to the poor availability of nutrients. This is a result of large- scale ocean current and stratification of the water column. In such regions, primary production still usually occurs at greater depth, although at a reduced level (because of reduced light).
Despite significant concentrations of macronutrients, some regions of the ocean are unproductive in the so-called HNLC (high- nutrient, low-chlorophyll) – a term used in marine ecology to describe areas of the ocean where the number of phytoplanktons are low inspite of high macro-nutrient concentrations (nitrate, phosphate, silicic acid).
HNLC is thought to be caused by the scarcity of iron (a micro-nutrient which phytoplankton require for photosynthesis) and high grazing rates by zooplanktons that feed on the phytoplankton. The HNLC condition has been observed in the equatorial and sub arctic Pacific Ocean, the Southern Ocean, and in some strong upwelling regimes, such as off central and northern California and off Peru.
By adding mineral iron in the iron deficient regions, it is possible to grow phytoplankton. Iron primarily reaches the ocean through the deposition of atmospheric dust on the sea surface. In the famous “iron experiment” in the eastern Pacific and near the South Pole, a solution of iron was spread over a large area to promote phytoplankton growth. An increase in chlorophyll concentration and phytoplankton numbers was noticed.
The oceanic areas adjacent to unproductive or HNLC arid regions of continents have abundant phytoplankton. For example the western Atlantic Ocean areas have plenty of phytoplankton, due to trade winds bringing dust and nutrients from the Sahara Desert in North Africa. This is an example of nature’s synchronizing the activities of different biomes for producing phytoplankton.
Phytoplankton plays an important role in the global carbon cycle by regulating atmospheric CO2. Efforts are being made globally to increase primary production in the world oceans to reduce the atmospheric CO2. More significantly about 50-75% of the atmosphere’s oxygen comes from marine phytoplankton.
Besides phytoplankton are also actively involved in the transport of nitrogen, phosphorus, iron and silica in the oceans It has been suggested that large-scale seeding of the world’s oceans with iron could generate phytoplankton large enough to negate anthropogenic carbon dioxide emission.
3. Deserts:
Deserts occur where rainfall is less than 50 cm/year, and cover about one fifth of the Earth’s surface. Most deserts occur at low latitudes, such as, Sahara of North Africa and in the southwestern U.S, Mexico, and Australia. Another kind of desert, cold deserts, occurs in Utah and Nevada and in parts of western Asia.
Soils often have abundant nutrients because they need only water to become very productive and have little or no organic matter. Disturbances are common in the form of occasional fires or cold weather, and sudden, infrequent, but intense rains that cause flooding. There are relatively few large mammals in deserts, due to absence of water and shelter from sun and the dominant animals are reptiles.
Desert biomes can be classified according to several characteristics. The four major types of deserts, include, Hot and dry, Semiarid, Coastal and Cold.
i. Hot and Dry Desert:
The deserts of this type are found in the North America (e.g. Great Basin), Southern Asian realm, Neotropical (South and Central America), Ethiopian (Africa) and Australia. The seasons are generally warm throughout the year and very hot in the summer. The winters usually bring little rainfall.
Temperatures exhibit daily extremes because the atmosphere contains little humidity to block the Sun’s rays. Desert surfaces receive a little more than twice the solar radiation received by humid regions and lose almost twice as much heat at night. The extreme maximum temperature is 49° C, while the minimum drops to -18° C. Evaporation rates regularly exceed rainfall rates. Lowest rainfall is less than 1.5 cm and the highest at 28 cm a year.
Plants are mainly small shrubs and short woody trees with leaves possessing “replete” (fully supported with nutrients) and water-conserving characteristics. In the cacti, the leaves are much- reduced (to spines) and photosynthetic activity is restricted to the stems. Some plants open their stomata, openings in leaves that allow for gas exchange, only at night when evaporation rates are lowest. These plants include yuccas, ocotillo, turpentine bush, prickly pears etc.
ii. Semiarid Desert:
The major deserts of this type include Montana and Great Basin (USA), and the near arctic realm (North America, Newfoundland, Greenland, Russia, Europe and northern Asia).
Winters normally bring low concentrations of rainfall, and average rainfall ranges from 2-4 cm, summer maximum day temperature is 38° C and night temperatures of around 10°C. Cool nights help both plants and animals by reducing moisture loss from transpiration, sweating and breathing. Furthermore, condensation of dew caused by night cooling may equal or exceed the rainfall received by some deserts.
The soil has a fairly low salt concentration with no subsurface water. The spiny plants in this zone with spines shade on the surface significantly reduce transpiration. The silvery or glossy leaves allow them to reflect more radiant energy. Semiarid plants include: creosote bush, white thorn, brittle bushes etc. During the day, insects move around twigs to stay on the shady side, jack rabbits follow the moving shadow of a cactus or shrub. Many animals find protection in underground.
iii. Coastal Desert:
These deserts occur in moderately cool to warm areas such as the near arctic and Neotropical realm. A good example is the Atacama of Chile. The cool winters of coastal deserts (minimum around – 4°C) are followed by moderately long, warm summers (maximum around 35°C). Average rainfall measures 8-13 cm in many areas. The maximum annual precipitation over a long period of years has been 37 cm with a minimum of 5 cm.
The fairly porous soil containing moderate amount of salt and good drainage supports. The plants have thick and fleshy leaves or stems, which can take in large quantities of water when it is available and store it for future use. The list of plants includes the salt bush, black bush, rice grass, and black sage. Some toads seal themselves in burrows with gelatinous secretions for 8-9 months until next rainfall, amphibians with accelerated larval stages thus reaching maturity before the waters evaporate.
iv. Cold Desert:
These deserts have by cold winters with snowfall and high overall rainfall throughout the winter and occasionally over the summer. They occur in the Antarctic, Greenland and the Nearctic realm. They have short, moist, and moderately warm summers with fairly long, cold winters. The mean winter temperature is between -2 to 4°C and the mean summer temperature is between 21 to 26°C.
The winter high snowfall results in annual precipitation ranges from 15 to 46 cm. It contains alluvial soil, which is relatively porous and good drainage leads to leaching out most of the salt. The main plants are deciduous, most having spiny leaves. Widely distributed animals are jack rabbits, kangaroo rats, kangaroo mice, pocket mice etc.
Each kind of desert has its own characteristic plants and animals according to climatic conditions in the region. Variations in the climatic conditions would lead to changes in the ecological cycle and so also the in the type of plants and animals.
Trade winds carrying dust rich in minerals from the Sahara Desert in North Africa have made HNLC or unproductive regions of oceans like western Atlantic Ocean highly productive areas for phytoplankton.
4. Forests:
Today, forests occupy approximately one-third of Earth’s land area, account for over two-thirds of the leaf area of land plants, and contain about 70% of carbon present in living things. However, forests are becoming major casualties of civilization. The ever growing industrialization and urbanization, to cater for the needs of rapidly increasing populations, have resulted in heavy deforestation through occupation of forest lands and consumption of forest resources. The three major types of forest biomes are tropical, temperate and boreal forests (taiga). They are situated at different latitude.
i. Tropical Forest:
Tropical forests occurring near equator in an area bounded by 23.5°N & 23.5°S, are characterized by the greatest diversity of species, and have only two seasons, viz., and rainy and dry, with no winter, and almost constant 12 hours daylight. Average temperature is 20-25° C and varies little throughout the year. Precipitation is even throughout the year, with annual rainfall > 2000 mm.
Soil is nutrient-poor and acidic. Decomposition is rapid and soils are subject to heavy leaching. Canopy in tropical forests is multilayered and continuous, allowing little light penetration.
Flora is highly diverse. In 1 sq.km, there can be 100 different tree species. Trees are 25-35 m tall, mostly evergreen, with large dark green leaves. Plants such as orchids, bromeliads, vines (lianas), ferns, mosses, and palms are present in tropical forests. Fauna include numerous birds, bats, mammals, and insects.
Further subdivisions of this group are determined by seasonal distribution of rainfall as follows:
i. Evergreen rainforest, no dry season.
ii. Seasonal rainforest: short dry period in a very wet tropical region. The trees and forest undergo definite seasonal changes. However general character of vegetation remains same as in evergreen rainforest.
iii. Semi evergreen forest: has longer dry season. The upper tree story consists of deciduous trees, while the lower story is still evergreen.
iv. Moist/dry deciduous forest (monsoon)’, the length of the dry season increases further as rainfall decreases (all trees are deciduous).
ii. Tropical Rainforests:
The intense solar radiation leads to a lot of evaporation, and as warm, moist air rises, it cools, the water condenses, and the water falls back to the earth as rain. Some of the rainforests are known as cloud forest or fog forest, due to high incidence of low-level cloud cover, usually at the canopy level, such as, Monteverdi cloud forest in Costa Rica.
Tropical rainforest is a major sink for GHGs and producer of oxygen. Rainforests now cover less than 6% of Earth’s land surface. Scientists estimate that more than half of all the world’s plant and animal species live in tropical rain forests.
Almost all rain forests lie near the equator in three major geographical areas.
The list includes:
(i) Central America in the Amazon River basin.
(ii) Africa – Zaire basin, with a small area in West Africa; also eastern Madagascar, and
(iii) Indo-Malaysia – west coast of India, Assam, Southeast Asia, New Guinea and Queensland, Australia.
Seventy percent of the plants in the rainforest are trees. The trees in the tropical rainforests produce 40% of Earth’s oxygen by photosynthesis through absorption of large amount of carbon dioxide. About 1/4 of all the medicines we use come from rainforest plants. Each of the three largest rainforests has a different group of animal and plant species.
Tropical rain forests, the heartland of ever-growing lush green trees responsible for absorbing large quantities of carbon dioxide producing 40% of the Earth’s oxygen have been a major casualty. More than one half of tropical forests have already been destroyed.
iii. Temperate Forest:
Temperate forests occur in eastern North America, northeastern Asia, and western and central Europe. Temperate zone has well- defined seasons with distinct winter, moderate climate and a growing season of 140-200 days. Temperature varies from -30° C to 30° C. Precipitation (75-150 cm) occurs evenly in a year. Soil is fertile, enriched with decaying litter. Canopy is moderately dense & allows light to penetrate, resulting in well-developed & richly diversified understory vegetation.
Flora is characterized by 3-4 tree species per square kilometer. Trees are distinguished by broad leaves that are lost annually and include such species as oak, hickory, beech, hemlock, maple, basswood, cottonwood, elm, willow, and spring- flowering herbs. Fauna is represented by squirrels, rabbits, skunks, birds, deer, mountain lion, bobcat, timber wolf, fox, and black bear.
Further subdivisions of this group are determined by seasonal distribution of rainfall:
i. Moist conifer and evergreen broad-leaved forests’, wet winters- & dry summers (rainfall in the winter months and winters are relatively mild).
ii. Dry conifer forests’, dominate higher elevation zones; low precipitation.
iii. Mediterranean forests’, precipitation in winter, less than 1000 mm per year.
iv. Temperate coniferous: mild winters, high annual precipitation > 2000 mm.
v. Temperate broad-leaved rainforests’, mild, frost-free winters, high precipitation (more than 1500 mm) evenly distributed throughout the year.
Only scattered remnants of original temperate forests remain.
iv. Boreal Forest (Taiga):
Boreal forests, or taiga, represent the largest terrestrial biome, occurring between 50° & 60°N latitudes. Boreal forests are found in the broad belt of Eurasia and North America: two-thirds in Siberia with the rest in Scandinavia, Alaska, and Canada. Seasons are divided into short, moist, and moderately warm summers and long, cold, and dry winters. The length of the growing season in boreal forests is 130 days.
Due to very low temperature, precipitation is mainly 40-100 cm of snow annually. Soil is thin, nutrient-poor, and acidic, canopy permitting low light penetration, & as a result, understory is limited. Flora includes evergreen conifers with needlelike leaves, such as pine, fir. Fauna includes woodpeckers, hawks, bear, fox, wolf, deer, hares, chipmunks; Current extensive logging in boreal forests may soon cause their disappearance.
5. Grasslands:
Grasslands are lands dominated by grasses rather than large shrubs or trees, and of two main types, viz., Tropical grasslands or Savannas and Temperate grasslands.
i. Savanna:
Savanna is grassland with scattered individual trees. Savannas of different types cover almost half the surface of Africa (about 5 million square miles, generally central Africa) and large areas of Australia, South America, and India.
Climate making a savanna is warm or hot, and annual rainfall ranging from 50.8 to 127 cm (20-50 inches) per year. Rainfall is concentrated in 6-8 months of the year, followed by long period of drought when fires can occur. If the rain were well distributed throughout the year, many such areas would become tropical forest.
Three different types of Savannas include climatic savannas (results from climatic conditions), edaphic savannas (caused by soil conditions, occur on hills or ridges where soil is shallow, or in valleys in claysoils, waterlogged, in wet-weather) and derived savanna, (results from clearing forest land for cultivation). In Africa, a heavy concentration of elephants in protected parkland has created a savanna by destroying trees, thus converting dense woodland into open grassland.
The predominant vegetation consists of grasses and forbs (small broad-leaved plants that grow with grasses). A type of savanna common in Kenya, Tanzania, and Uganda, called grouped-tree grassland, has trees growing only on termite mounds. Frequent fires and large grazing mammals kill seedlings, thus keeping the density of trees and shrubs low. Seasonal fires play a vital role in the savanna’s biodiversity. The deep roots remain unharmed by fire and grow when the soil becomes moist. With rains, savanna bunch grasses grow vigorously, to an inch or more in 24 hours.
However, controlled burning of far north Australian savannas can result in an overall carbon sink. Other animals (which do not all occur in the same savanna) include giraffes, zebras, buffaloes, kangaroos, mice, moles, snakes, termites, beetles, lions, leopards, hyenas, and elephants. The environmental concerns regarding savannas are mainly due to human activities such as poaching, overgrazing, and clearing of the land for crops.
ii. Temperate Grassland:
Temperate grasslands have grasses as dominant vegetation (no tree, large shrubs), with large temperatures variation from summer (38° C or 100°F) to winter (-40° C or -40°F) and less rainfall (average 50.8-88.9 cm or 20-35 inches) than temperate grasslands in savannas. Precipitation occurs in the late spring and early summer. Major temperate grasslands include veldts of South Africa, pasta (Hungary), pampas (Argentina & Uruguay), steppes (former Soviet Union), and plains & prairies (Central North America).
As in the savanna, seasonal drought and occasional fires affect biodiversity but to a lesser extent. Because of nutrient-rich soil, the temperate grasslands are deep and dark, with fertile upper layers.
Trees, such as cottonwoods, oaks, and willows grow in river valleys, and some nonfood plants, specifically a few hundred species of flowers, grow among the grasses. The fauna in different zones include gazelles, zebras, rhinoceroses, wild horses, lions, wolves, prairie dogs, jack rabbits, deer, etc.
There are also environmental concerns regarding the temperate grasslands. Few natural prairie regions remain because most have been turned into farms or grazing land. This is because they are flat, treeless, covered with grass, and have rich soil. Today, people use steppes to graze livestock and to grow wheat and other crops. Overgrazing, plowing, and excess salts left behind by irrigation waters have harmed some steppes. Strong winds blow loose soil from the ground after plowing, especially during droughts. This causes the dust storms of the Great Plains of the U.S.
6. Tundra:
Tundra is the coldest of all the biomes. Tundra comes from the Finnish word tunturi, meaning treeless plain.
It is a frost-molded landscape with following characteristics:
a. Extremely cold climate & low biotic diversity.
b. Simple vegetation structure due to limitation of drainage.
c. Short season of growth and reproduction.
d. Energy and nutrients in the form of dead organic material.
e. Large population oscillations.
Tundra is separated into two types:
i. Arctic Tundra:
Arctic tundra is located in the northern hemisphere, encircling the North Pole & extending south to the coniferous forests of the taiga. The arctic is known for its cold, desert-like conditions. The growing season ranges from 50 to 60 days. Yearly precipitation, including melting snow, is 15 to 25 cm (6 to 10 inches). A layer of permanently frozen subsoil called permafrost exists, consisting mostly of gravel and finer material.
When water saturates the upper surface, bogs and ponds may form, providing moisture for plants. No deep- rooted vegetation forms but a wide variety of plants, about 1,700 kinds, grow the arctic and sub-arctic, including low shrubs, sedges, reindeer mosses, liverworts, & grasses and 400 varieties of flowers. Mammals & birds have additional insulation from fat, breed and raise young quickly in summer, hibernate or migrate (bird) during the winter because food is not abundant.
Recent reports of permafrost, (frozen soil in Arctic Tundra) melting is expected to mop up organic matters and bacteria. This may cause release of more CO2 and CH4, nitrates and phosphates. While release of GHGs would add to the global warming, nitrates and phosphates would allow novel plants to grow and make the landscape full of domes and pits known as thermokarst – thus changing the tundra’s ecology. A combination of melting of ice and thawing permafrost has resulted in submersion of several coastal villages in Alaska.
ii. Alpine Tundra:
Alpine tundra is located on mountains throughout the world at high altitude where trees cannot grow. The growing season is approximately 180 days. The night time temperature is usually below freezing. Unlike the arctic tundra, the soil in the alpine is well drained. Plants are similar to arctic ones and include tussock grasses, dwarf trees, small-leafed shrubs, and heaths Animals living in the alpine tundra include mammals pikas, marmots, mountain goats, sheep, and elk- grouse like birds and insects; beetles, grasshoppers, butterflies.
Term Paper # 3. Carbon & Biodiversity Demarcation Atlas of Biomes:
A demonstration atlas correlating carbon and biodiversity has been produced by the World Conservation Monitoring Centre (WCMC) of the UN Environment Programme (UNEP), with support from the German government and the Humane Society International. The atlas is believed to be the first of its kind. Atlas maps those places that contain major species concentrations and where efforts to stop deforestation will produce maximum benefit.
The atlas includes regional and national maps for six tropical countries showing where areas of high carbon storage coincide with areas of biodiversity importance. It also shows that existing protected areas are high in both carbon and biodiversity. The earth’s terrestrial ecosystems store an estimated 2,000 billion tonnes (Gigatonnes) of carbon (GtC) in the biomass above ground and in the soil, with a significant proportion of this in the tropics.
The tropical Andes is the richest and most diverse biodiversity hotspot in the world while the Amazon rainforest, the world’s largest continuous rainforest area, hosts an estimated quarter of the world’s terrestrial species. High biodiversity areas within the tropical Andes and Amazon account for 11 percent of the total carbon stock in the area the experts call the neotropics.
In tropical Africa over 60 percent of the high biodiversity areas are in high carbon areas and contain a total of 18 billion tonnes of carbon. Employing the techniques used in the atlas would make it possible to identify where areas of high carbon density and high density of great apes overlap, in order to find where REDD investment could also benefit great ape conservation.
The national maps in the atlas illustrate different ways of identifying areas of biodiversity importance and their overlaps with high carbon areas. In Tanzania, key biodiversity areas contain 17 percent of the country’s carbon stock. Vietnam’s protected areas cover 32 percent of the land area that has been identified as having high values for both carbon and biodiversity, demonstrating the potential value of the protected area system for meeting both carbon and biodiversity goals.
In Papua New Guinea the map illustrates how the centre of the country, which is high in biodiversity, also contains areas of large areas of high carbon stock. It also shows that existing protected areas overlap with only 14 percent of the high carbon areas. ‘India’s Western Ghats are among the hotspots identified in the atlas.
The prevention of deforestation helps combating climate change, conserving biodiversity from amphibians and birds to primates Nature has spent millions of years perfecting carbon capture and storage in forests, peatlands, soils and the oceans while evolving the biodiversity that is central to healthy and economically productive ecosystems, Preservation of biomes is thus an .essential step towards minimizing global warming.