Chapter 20: Natural Regions of the World
Suppose you could set out from the Equator and walk north in a straight line, and simply keep going. You would begin inside a forest so tall and so closely packed that the ground stays almost dark at midday. Every afternoon, between noon and three, the rain would come down in sheets. Keep walking. The forest thins. The trees now stand apart, with tall coarse grass between them, and there is a long season when no rain falls at all and the grass turns brown and waits. Keep walking. The grass gives out and the sand begins, where the air is so dry that a fierce afternoon can be followed by a night cold enough for frost. Keep walking, and olive trees appear along a coast whose rain arrives in winter and whose summer is dry. Keep walking, and the trees fall away again into open grassland ploughed for wheat. Keep walking, and a belt of spruce and fir runs on without a break. Keep walking, and the trees stop for good, leaving moss, lichen and sedge over frozen ground. You have not changed continent. You have changed climate — and climate has rearranged the plants, the animals and the way people earn a living.
Map
Map 20.A1 Caption: The world sorted into its major natural regions, each named after the climate and vegetation that dominate it. Brief: World outline map with Equator, both Tropics, Arctic and Antarctic Circles marked; shade and label only the eight regions the syllabus lists — Equatorial, Tropical Grasslands, Tropical Deserts, Tropical Monsoon, Mediterranean, Temperate Grasslands, Taiga and Tundra — with a key giving one distinct tint per region and no country names shown.
20.1 What A Natural Region Is
A natural region is a part of the Earth’s surface which has a comparatively high degree of uniformity of structure, surface form and climate within it. Structure means the rock that lies beneath, surface form means the shape of the land above it — plain, plateau or mountain — and climate means the long-run pattern of temperature and rainfall. Where all three hold steady across a wide stretch of the Earth, geographers treat that stretch as a single unit.
Because of that uniformity, every natural region is a homogeneous unit, meaning one whose parts closely resemble one another. The resemblance is not only in the physical conditions but in what those conditions allow people to do.
The following are broadly uniform within a natural region: (a) The climatic conditions, so temperature and rainfall follow much the same yearly rhythm across the whole region. (b) The soil, because it is formed under that same climate acting on the rock below. (c) The natural vegetation, since plants can only grow where the temperature and moisture suit them. (d) The human activities, because the crops that can be raised and the animals that can be kept are set by the same climate.
Uniform, But Not Identical
Uniformity is a matter of degree, not of sameness. Slight variations are present within each climatic region, but these variations are far more pronounced between one climatic region and the next. That difference in scale of change is what makes the division useful.
Take the region on either side of the Equator, where uniformly hot and rainy conditions are prevalent throughout the year. Despite this uniformity, minor variations in temperature and rainfall are still found within the Equatorial region. The conditions are quite different, however, in the adjoining Savanna region, which has greater variation in temperature and receives only moderate rainfall. The step you take on crossing from one to the other is much larger than any step you take inside either.
A boundary line on a world map is therefore a convenience rather than a wall on the ground. One region shades into the next over a wide belt, and the line simply marks where the shading has gone far enough to matter.
Why The World Is Divided This Way
Thus the world is divided into a number of major regions whose physical features, rock structure, soils, climate and resultant products and human activities are similar over large areas. Resultant products means what the region yields under that climate — its timber, its crops, its livestock.
The value of the division is that it lets you carry an explanation from one place to another. Understand why a process works as it does in one part of a region, and you have understood most of the region, because the conditions driving that process hardly change across it.
20.2 Climatic Classification Of Natural Regions
The basic factor on the basis of which the world is divided into major natural regions is climate. It is chosen because it does not act alone — it acts on everything else. The climate influences the soil, the flora and fauna, and the vegetation of the region. Flora means the plant life of an area and fauna means its animal life.
That influence is why the climatic regions are also named after the vegetation type prevalent there. Naming a region a rainforest or a grassland is a way of naming its climate in shorthand, because the plants are the visible record of the temperature and rainfall that produced them.
Why Rainfall Alone Is Not Enough
Vegetation does not simply follow the rain gauge. It depends not only on the total annual rainfall, but also on the relation of that rainfall to temperature, and on its distribution through the year. Two places receiving the same annual total can carry very different plants if one gets its rain in a single burst and the other spreads it evenly.
Temperature enters through evaporation, the process by which water at the surface turns to vapour and returns to the air. In high latitudes, evaporation is less than in low latitudes. Hence, less rainfall is needed to keep the subsoil moist than in tropical regions, and a modest total that would leave a tropical soil parched can support steady growth in a cold one.
What The Classification Rests On
Every natural region has a combination of climatic elements different from every other. The sorting of these combinations into types is known as climatic classification, and each type has some common characteristics that hold wherever that type is found.
The climatic zones are based on the following factors: (a) The temperature, pressure, winds and humidity conditions, which differ from type to type, so that the human response under different climatic types is different. (b) The landforms, which differ in different climatic regions. (c) The weathering of rocks, which is influenced by climatic conditions, so that soils too vary considerably from one region to another. (d) The vegetation and wildlife, which vary greatly from one climate type to another. (e) The water run-off in rivers and streams, which differs considerably between regions. (f) The cropping seasons and methods, which vary with the climatic conditions.
Read down that list and one pattern stands out: every item after the first is a consequence of the first. Temperature, winds and humidity are the drivers, and soils, plants, animals, run-off and crops are what those drivers produce. Fig. 20.A1 sets out that chain.
Flowchart
Fig. 20.A1 Caption: Climate is placed first in the classification because everything else in a region follows from it. Nodes: climate — temperature, pressure, winds and humidity → branch 1: weathering of rocks → soils differ from region to region; branch 2: vegetation → wildlife that feeds and shelters in it; branch 3: water run-off in rivers and streams; branch 4: cropping seasons and methods → agriculture, animal husbandry and forestry; all four branches → the region is named after its climate or its vegetation type
Climate And The Way People Live
Human response shows a broad relationship with climatic conditions. The relation between climate and human activities is most striking in regions where the primary activities are dominant — agriculture, animal husbandry and forestry, which take their produce directly from the land rather than processing it in a factory.
These activities are governed directly by the climatic conditions. Each climatic type suits the cultivation of certain crops and not others, because a crop can tolerate only some range of temperature and needs a certain minimum water supply. Fall below that minimum, or move outside that range, and the crop fails however carefully it is tended. Thus the major natural regions are named after the climate or the vegetation type.
It should be noted, however, that with modern technology these differences are rapidly reducing. Irrigation, greenhouses, cold storage and transport all loosen the grip of climate on what people can grow and do. In fact, economic status now determines activities in a region a good deal of the time, since the money available decides whether that technology can be bought at all. Climate still sets what is easy and what is expensive; it no longer settles what is possible.
Based on the climatic classification, the major natural regions of the world are discussed below.
20.3 Equatorial Region
20.3.1 Location
The Equatorial Region extends between 0–10° north and south of the Equator. It is therefore a narrow ribbon wrapped around the middle of the globe, reaching only about ten degrees of latitude on either side of the line.
That narrowness matters. Everything described in this section — the daily rain, the tall forest, the animals that live above the ground — belongs to a belt you could cross in a day’s flight.
20.3.2 Area
The region is not continuous. It is broken into blocks by the oceans, and each block sits astride the Equator on a different continent.
It is found in the following areas: (a) Asia: Indonesia, Malaysia, and the southern part of the Philippines, all of them island or peninsular lands of South-East Asia. (b) South America: the coastal lowlands between the Guiana and Brazilian Highlands, the Amazon basin, and coastal Columbia on the north-western shoulder of the continent. (c) Africa: the Zaire basin in the middle of the continent, and the Guinea coast in West Africa. (d) Oceania: Papua New Guinea, the large island lying north of Australia.
Fig. 20.1 shows how these blocks line up along the Equator.
Map
Fig. 20.1 Caption: Regions with Equatorial climate. Brief: World outline map with the Equator, both Tropics and the Arctic Circle drawn; shade in one dark tint only the equatorial areas of Indonesia, Malaysia, the southern Philippines, the Amazon basin and coastal Columbia, the Zaire basin, the Guinea coast and Papua New Guinea; India shown to its full extent as officially defined; no country names printed.
20.3.3 Climate
The climate in the Equatorial Region is characterised by heavy rainfall and constant high temperatures throughout the year. This region lies in the Torrid belt, the hot zone of the earth that stretches between the two Tropics.
At and near the Equator, the Sun’s rays have a high angle of incidence, which varies between 66½° and 90° during the year. The angle of incidence is the angle at which the rays strike the ground; the closer it is to 90°, the more nearly overhead the Sun is, and the more heat each square metre of ground receives. The days and nights here are almost of equal duration throughout the year.
Temperature
The temperature in this region ranges between 25°C and 30°C during the year. The mornings are pleasant and sunny, and the temperature then begins to rise as the Sun climbs.
In the afternoon, the sky is overcast with clouds. This cloud cover prevents heat from being radiated back to the atmosphere, so the temperature at the ground remains high. The nights are cool and the sky remains clear at night, which lets the day’s heat escape upward.
Rainfall
The Equatorial rainfall is of the convectional type throughout the year. Convectional rainfall is rain formed when air heated at the ground rises, cools as it goes up, and drops its moisture. It ranges between 175 to 250 cm a year. This is due to the vertical rays of the Sun, the intense heating of land, and the radiation of heat into the atmosphere.
Some of the mountainous areas, like those in Indonesia and in Africa, receive orographic or relief type of rainfall instead. Orographic rainfall falls where moist air is forced to climb a slope, cooling as it rises.
The temperature and rainfall are also modified by the relief, meaning the height and shape of the land. For example, Mount Kilimanjaro, the highest mountain peak in Africa, has peaks covered with snow throughout the year despite being close to the Equator. East Africa, because of its high elevation, has considerably lower mean temperature and rainfall than the equatorial lowlands nearby.
In the plains, torrential rainfall occurs regularly in the afternoon between 12 noon and 3 p.m. The amount of rainfall decreases with increase in distance from the Equator, and rainfall is maximum at the equinoxes in March and September. Fig. 20.A2 follows one such day from sunrise to nightfall.
Flowchart
Fig. 20.A2 Caption: The equatorial day repeats itself with very little change, all through the year. Nodes: pleasant sunny morning → intense heating of the land by near-vertical rays → heated air rises and cools → cloud builds and the sky is overcast by midday → torrential rain between 12 noon and 3 p.m. → cloud clears after the rain → clear night sky lets heat radiate away → cool night → back to a pleasant sunny morning
Seasons
There is no winter or dry season here. Due to the small differences in temperature through the year, the region has a hot and wet season throughout the year — one season, repeated, rather than a cycle of several.
20.3.4 Natural Vegetation
The Equatorial region has a dense forest cover known as Tropical Rainforest, or Selvas in the Amazon Basin, which is the local name for this forest. The rainforests occupy low altitude areas near the Equator in South America, especially in the Amazon Lowlands, in Central and West Africa, in the Indo-Malay peninsula that runs from mainland South-East Asia into the islands, and in the New Guinea region.
These forests are thick and luxuriant. The trees have broad leaves and are evergreen, which means they carry leaves all year instead of shedding them in one season — there is no dry season here to shed them for.
The Four Layers Of The Forest
The vegetation in these forests shows four distinct layers, and the reason for the layering is competition for light.
The layers, from the top down, are the following: (a) The emergent layer, at the edge of the forest, has trees like the kapok and mahogany which reach up to the height of over 50 metres. (b) The canopy is the top layer, formed by the crowns of trees which grow close together, and it blocks out sunshine and wind. (c) The understorey is the next layer down, where the light is blocked by the canopy, so the plants have larger leaves to maximise the light they can absorb. (d) The bottom layer, or the forest floor, has ferns and shrubs as well as climbers.
Diagram
Fig. 20.2 Caption: Equatorial plants. Brief: Cross-section through a rainforest with a vertical scale in metres marked 0 to 50 on the left; label the emergent trees rising above the continuous canopy, the under canopy, the shrub layer and the forest floor; show trees of different ages and sizes and note that little light reaches the ground, so few shrubs grow there.
The main trees of the rainforests include ebony, mahogany, cinchona, green heart, rosewood, and rubber. Fig. 20.3 gives an idea of how unbroken this cover looks from above.
Diagram
Fig. 20.3 Caption: An aerial view of rainforests in Brazil. Brief: Source an aerial photograph looking down on unbroken rainforest canopy with a river winding through it; emphasise the continuous green surface of the canopy and the absence of any gap through which the ground can be seen.
The equatorial region, because of the presence of the dense Tropical Rainforest, is called the ‘Lungs of the World’. This is because the rainforests function as a giant machine that absorbs a large amount of carbon dioxide and produces oxygen.
Wildlife
The Equatorial forests have a wide variety of animal species, and many of them have solved the same problem the plants faced. Some animals, including snakes, are found on trees rather than on the ground. Such types of animals are called arboreal, meaning adapted to living on trees.
The reason is the darkness below. It is almost dark on the ground, and the absence of light does not favour the growth of life there, so the food and shelter are up in the branches. There are a large number of lemurs, apes, monkeys, and reptiles like snakes, lizards and frogs.
Near the edge of the forests, where light does reach the ground, elephants and rhinoceroses are found. Among the birds found in these forests are horn bills, parrots and macaws, and most of the birds are bright-coloured.
20.3.5 Human Adaptations
In the Equatorial regions, traditionally, some primitive people practise hunting and gathering, whereas others practise shifting cultivation — clearing a patch of forest, cropping it for a few seasons, and then moving on to clear another. In the clearing for shifting cultivation, crops like tapioca, yam, bananas, groundnuts and maize are grown.
Many plantations have been established in the Equatorial regions, especially in Java, Sumatra, Malaysia, West Africa and Central America. A plantation is a large estate growing a single crop for sale rather than for the grower’s own use. The most outstanding of these plantations are natural rubber and cocoa.
Malaysia and Indonesia are the leading producers of natural rubber in the world, accounting for more than a third of the world production. Cocoa is most extensively cultivated in West Africa, with Ghana and Nigeria being the important producers.
Other crops grown in the Equatorial regions include bananas, coconuts, coffee, cinchona, sugar, spices, sago, tea, tobacco and pineapples. What ties this long list together is the climate that made it possible: constant warmth and constant moisture allow growth to continue all year, with no cold season to interrupt it.
20.4 Tropical Grasslands
20.4.1 Location
Tropical Grasslands, also known as Savannas, are a grassland biome located in semi-arid to semi-humid climate regions of subtropical and tropical latitudes. A biome is a large community of plants and animals suited to one set of climatic conditions; semi-arid means only partly dry, and semi-humid means only partly moist.
They lie roughly between 7° to 20° north and south of the Equator. That places them immediately poleward of the equatorial belt on both sides, which is why the two regions were compared in section 20.1.
20.4.2 Area
Savannas of one sort or another cover almost half the surface of Africa, about five million square miles, generally in Central Africa, and they take in large areas of Australia, South America and Central America. The square mile is an older unit of area still used in some texts.
The main stretches are the following: (a) South America: there are two distinct regions of Savanna, north and south of the Equator, namely the Llanos of the Orinoco Basin in the north of the continent and the Campos of the Brazilian Highlands. (b) Africa: Sudan, Senegal, Chad, Cameroon, Ghana, Guinea, Mali, Niger, Togo, Kenya, Tanzania, Angola, Uganda, Zaire, Zambia, Zimbabwe, Malawi and Mozambique — a spread that runs right across the continent and down its eastern side. (c) Australia: the Northern Territory and Queensland, in the north and north-east of the country.
Fig. 20.4 shows how these blocks sit as two broad bands, one on either side of the equatorial forest.
Map
Fig. 20.4 Caption: Tropical grasslands. Brief: World outline map with the Equator and both Tropics drawn; shade in one dark tint the savanna belts of central and southern Africa, northern Australia and South America, labelling Llanos and Campos on South America; India shown to its full extent as officially defined; no other names printed.
20.4.3 Climate
Temperature
The climate of the region is characterised by hot, wet summers and cool dry winters. Since the regions lie within the Tropics, there is great heat in summer, with 13 to 14 hours of sunshine and low humidity. The average monthly temperature during the dry season lies between 22°C and 37°C.
The highest temperature does not coincide with the period of the highest Sun. It occurs just before the onset of the rainy season. For instance, the hottest months in Sudan are April and May, and October in Salisbury in Australia. There occurs a distinct drop in temperature during the rainy season, due to the overcast sky and the cooler atmosphere it brings.
Days are hot, and during the hot season noon temperatures of over 38°C are quite frequent. However, when night falls, the same clear sky which promotes intense heating during the day also causes rapid radiation in the night. Temperatures drop to well below 10°C, so a single day here can swing through nearly thirty degrees.
Rainfall
The annual rainfall is less than that of the Tropical Monsoon climate, and the length of the wet and dry seasons also differs from area to area. There is no single savanna year that fits every part of the region.
Seasons
In the northern hemisphere, the hot, rainy season begins in May and lasts till September, and the rest of the year is cool and dry. In the southern hemisphere, the rainy season is from October to March. The two halves of the region are therefore out of step with each other by about six months, because the seasons themselves are reversed across the Equator.
20.4.4 Natural Vegetation
The Savanna landscape is characterised by tall grasses and short trees — the reverse of the rainforest, where the trees dominate and little grows below.
The grass is coarse and grows to the height of 3 to 6 feet at maturity. It has long roots which go deep down in search of water, which is what allows it to survive months in which no rain reaches the surface.
During the rainy season, the grass appears green and well-nourished. It lies dormant throughout the long, rainless period, meaning it stops growing but does not die, and it appears again in the next rainy season. In between the tall grass, scattered short trees and low bushes grow. Fig. 20.A3 sets out this yearly rhythm.
Flowchart
Fig. 20.A3 Caption: The savanna year is a swing between growth and waiting, repeated without end. Nodes: rainy season begins → grass turns green and well-nourished → rains end and the cool dry season begins → trees shed their leaves and the grass lies dormant → long rainless period with deep roots reaching for water → next rainy season arrives → back to green, well-nourished grass
As the rainfall becomes scarce towards the deserts, the Savanna merges into thorny scrub — low, spiny bushes able to survive on very little water. There is no line on the ground where one ends and the other begins.
The trees are deciduous trees, which shed their leaves in the cool, dry season to prevent excessive loss of water. A leaf loses water to the air, so a tree with no leaves loses far less of it.
Some of the trees, like the baobabs and bottle trees, take a different route. They have broad trunks with water-storing devices, which lets them survive during the dry season on water taken in months earlier.
20.4.5 Human Adaptations
The Savannas are called the ‘natural cattle country’, as many of the traditional native people are herdsmen or pastoralists — people who make their living by keeping grazing animals rather than by growing crops. They keep large numbers of cattle which are fed on the tall grass or the bushes, and which provide them with meat and milk.
Queensland in Australia is the largest cattle producing state. Cattle ranching is an important economic activity in the Campos and Llanos grasslands of South America, where the same tall grass supports the same activity half a world away.
The Savannas also have immense potential for plantation agriculture, such as cotton, cane sugar, coffee, oil palm, groundnuts and tropical fruits. This is because of 30 inches of annual rainfall and the lack of severe cold. An inch is a little over two and a half centimetres, so this is a moderate total — far less than the equatorial forest receives, but spread over a warm year in which nothing freezes.
In West Africa, the main crops are groundnuts, oil, palm and cocoa, and there are large plantations of sugarcane, cotton and tobacco. Fig. 20.6 shows one such plantation.
Diagram
Fig. 20.6 Caption: A cocoa plantation. Brief: Source a photograph taken inside a cocoa plantation showing ripening pods growing directly on the trunks and lower branches, with the shade of taller trees overhead; emphasise the regular spacing of the planted trees.
20.5 Tropical Deserts
20.5.1 Location
Between 15° to 30° North and South Latitudes are the Tropical Deserts, and they are so known because this latitude zone mostly falls in the tropical zone. They therefore lie just poleward of the savanna belt, at the dry end of the same drying trend.
One further point of their position matters more than any other: they lie to the west of the landmass. Section 20.5.3 shows why that single detail explains most of what follows.
20.5.2 Area
The tropical deserts are found on every continent that reaches into these latitudes.
They are found in the following areas: (a) Africa: the Sahara desert, the largest in the world, in North Africa; the Kalahari desert in South-West Africa; and the Namib desert in Namibia and South-west Angola. (b) Asia: the Arabian desert and the Thar desert, the latter in the north-west of the Indian subcontinent. (c) North America: the desert extends from Mexico into the USA and is called by different names, like the Mohave, Sonoran, Californian and Mexican Deserts. (d) South America: the Atacama Desert, the driest of all deserts, lies along the Pacific coast. (e) Australia: the Great Australian Desert, which occupies much of the middle of the continent.
Fig. 20.7 shows these areas together, and the pattern in their placing is worth pausing over.
Map
Fig. 20.7 Caption: Tropical desert regions. Brief: World outline map with the Equator, both Tropics and the Arctic Circle drawn; shade in one dark tint and label the Mohave, Sahara, Arabian, Iranian, Thar, Massawa, Kalahari, Namib, Atacama and Australian deserts; India shown to its full extent as officially defined; no country names printed.
20.5.3 Climate
This climate type is characterised by offshore dry Trade winds originating from the high pressure belt. Trade Winds are the steady winds that blow from the high pressure belts of the subtropics towards the Equator, and offshore means blowing from the land out to the sea, so they carry no moisture in from the ocean.
Tropical deserts have hot summers and cool winters, and the world’s highest temperatures are recorded in these areas.
Temperature
Summer temperatures may range from 30°C to 45°C, and some areas may record a maximum of 58°C during peak summer. The hottest month has a mean temperature of 30°C, a mean being the average taken over the whole month rather than the single highest reading.
Land heats and cools quickly, and the absence of vegetation creates extremes of temperature. With no leaf cover to shade the ground by day or hold warmth near it by night, nothing softens the swing. The winter temperature may be less than 20°C, and sometimes there may be frost at night.
Rainfall
There are a few areas in the deserts with no rainfall at all. Generally, hot deserts have less than 25 cm annual rainfall, which is a small fraction of what the equatorial forest receives in a year.
Since these deserts are located on the western margins of continents, the Trade Winds that blow in the region shed their moisture in the eastern margins of continents. They become dry by the time these winds reach the western side. Cold ocean currents also help in the formation of deserts: they do not cause rain, they bring mist and fog, and they lower the temperature of the air above them. Fig. 20.A4 traces the whole chain.
Flowchart
Fig. 20.A4 Caption: A desert on the western margin is the end of a long drying process, not a single cause. Nodes: high pressure belt → Trade Winds set off across the continent → they shed their moisture on the eastern margins → they arrive dry at the western margins and blow offshore → rainfall under 25 cm a year; cold ocean current offshore joins here → no rain, only mist and fog, and lower air temperature → scanty vegetation cover → bare land heats and cools quickly → extremes of temperature
Seasons
In the interior parts there are generally two seasons — winter and summer. In coastal areas, there may be a short rainy season between summer and winter.
Hot, dry winds like the Mistral, Bora and Sirocco bring pleasant weather conditions and may affect the seasons. These are named local winds, each belonging to one part of the world rather than blowing everywhere.
20.5.4 Natural Vegetation
In this region the rainfall is scanty and the dry Trade Winds do not help to support vegetation cover. At some places thorny shrubs like cactus and prickly pear are found. Fig. 20.5 shows what this thin, widely spaced cover looks like on the ground.
Diagram
Fig. 20.5 Caption: A desert landscape at sunset. Brief: Source a photograph of an arid landscape with widely spaced thorny desert trees and low scrub on bare sandy ground, taken at sunrise or sunset; emphasise the large gaps of open ground between plants.
Plants which are adapted to arid condition are known as xerophytic plants, arid meaning so dry that little will grow. They are almost leafless and store water in their stems, which is how they carry themselves through months without rain.
Their defences are as important as their water stores, because in a place with so little green, every plant is a target.
Their adaptations include the following: (a) Some plants have leathery leaves, which lose far less water to the air than soft ones. (b) Others have thorns, which discourage animals from grazing on them. (c) Still others have a repugnant smell, which serves the same purpose of protection against animal grazing. (d) Thorny cacti, which is often cited as a typical desert plant, combine a swollen water-storing stem with spines in place of leaves.
Near water courses, where a channel carries water at least part of the year, date palms are found.
Wildlife
Even in this harsh environment, one can find lifeforms like lizards, squirrels, snakes, rats, foxes and mice. To escape the heat, burrowing animals dig holes in the ground, where the temperature swings far less than it does at the surface.
Some animals which wander in the desert but live near the edges include jackals, foxes, hyenas and antelopes. People use camels to travel through deserts, since a camel can cross long dry stretches between water points.
20.5.5 Human Adaptations
In the harsh, inhospitable conditions in the deserts, the inhabitants have to struggle against an environment deficient in water, food and other means of livelihood. Some of the desert’s inhabitants live as nomadic hunters and food gatherers, moving with the seasons rather than settling in one place, and among them are the Bushmen of the Kalahari and the Bindibu of Australia.
Crops cannot be grown without irrigation in the deserts. Irrigation is the supply of water to fields by human effort rather than by rain. The water for irrigation is obtained from rivers, dams, oasis, or through a network of canals.
The life-giving waters of the river Nile in Egypt allow the Egyptians to raise a number of crops. They cultivate rice and cotton in summer, followed by wheat, barley, beans and other minor crops in winters — two harvests a year, in a country where the rainfall alone would support none.
In the deserts, where there are oasis, underground water reaches the surface and is drawn up from wells by camels or mules. An oasis is a spot in the desert where such water is available all year. Water is led to the fields by irrigation channels, small cuts that carry it from the well to the crop.
Besides the date palm, the other crops cultivated in the oasis include barley, cane, cotton, wheat, sugar, fruits and vegetables. The oasis is therefore a small, sharply bounded island of farming, and its size is set not by the soil or the sunshine but by how much water can be lifted and led out to the fields.
20.6 Tropical Monsoon Type Climate
20.6.1 Location
The Tropical Monsoon type of climate is found in Southern Asia, with onshore wet monsoons in the summer and offshore dry monsoons in the winter. A monsoon is a wind that reverses its direction between the seasons; onshore means blowing from the sea towards the land, and offshore means blowing from the land out to the sea. The reversal is the whole of the story: the same region is wet or dry depending on which way the wind is pointing.
Alongside it, the Tropical Marine type of climate is experienced along the eastern coasts of tropical lands, which receive steady rainfall from the Trade Winds all the time. The two are treated together here, but they are not the same. The monsoon type has one wet season and one dry one; the marine type, sitting on the eastern coasts where the Trade Winds arrive still loaded with moisture, is watered all year and has no dry season to speak of.
20.6.2 Area
The two types occupy different sides of the tropical world, and Fig. 20.8 separates them.
The Tropical Monsoon type is found in these areas: (a) Asia: India, Pakistan, Bangladesh, Sri Lanka, Myanmar, Southern China, Cambodia, Laos, Thailand, Vietnam, and the islands of Hainan, Taiwan and the Philippines. (b) Australia: the northern tip of Australia.
The Tropical Marine type is found in these areas: (a) Africa: parts of South-East Africa and Madagascar, the large island off Africa’s eastern coast. (b) Central America: Jamaica, Belize, Honduras and Nicaragua. (c) South America: eastern Brazil. (d) Australia: parts of North-eastern Australia.
Map
Fig. 20.8 Caption: Regions with Tropical Monsoon type climate. Brief: World outline map with the Equator and both Tropics drawn; use two clearly different tints with a key, one for Tropical Monsoon and one for Tropical Marine, shading southern and south-eastern Asia and northern Australia in the first and the eastern coasts of South-East Africa, Madagascar, Central America, eastern Brazil and north-eastern Australia in the second; India shown to its full extent as officially defined.
20.6.3 Climate
The Tropical Monsoon type of climate is regarded as a sub-region of the tropical, and of the sub-tropical humid and dry, climatic region. It has hot summers and cool winters with a distinct rainy season.
In the areas with Tropical Marine type climate, the onshore Trade Winds influence the climate all the year round and lead to more evenly distributed rainfall, so the year has no sharp break in it.
Temperature
The summer temperature varies between 27°C to 30°C in the coastal areas and 35°C to 38°C in the interior. The sea keeps the coast cooler in summer, and the same sea keeps it warmer in winter: the winter temperature is between 5°C and 18°C in the interior and between 22°C and 25°C in the coastal areas.
There are cyclonic disturbances in this region, and the monsoon is also not regular from year to year. The Monsoon depends on rainfall instead of temperature — it is the rain, not the thermometer, that marks its seasons. At the end of the monsoon, when the seasonal winds begin to withdraw, there are often violent storms.
Rainfall
Summer rain provides a refreshing contrast from the dry conditions in winter. The Trade Winds in winter are offshore winds, and they blow from land to sea, which normally means no rain.
In India, however, due to the Himalayan barrier, these winds move in the North-East direction. They pick up moisture over the Bay of Bengal and cause winter rainfall over much of the Coromandel coast, which is the south-eastern coast of India. Fig. 20.10 shows this winter pattern, and Fig. 20.9 the summer one.
Many other factors, like cyclones in winter, influence rainfall, and the rainfall is therefore not uniform in this region. The annual amount of rainfall varies from 75 to 200 cms. Cherrapunji in Meghalaya, in the hills of north-east India, receives over 1200 cm rainfall, and Mawsynram near Cherrapunji has recorded the heaviest rain in the world.
In the areas with Tropical Marine type of climate, rainfall is caused by the Trade Winds and also by the intense heating during the day in summer, which lifts moist air and turns it to rain.
Map
Fig. 20.9 Caption: Summer south-west monsoon winds. Brief: Map of southern Asia and northern Australia with arrows showing the South-West Monsoon striking the Indian subcontinent and the South-East Monsoon crossing the Equator towards it; label the Himalayan barrier, the low pressure over the Punjab region and the high pressure to the south; arrows point from sea towards land; India shown to its full extent as officially defined.
Map
Fig. 20.10 Caption: Winter north-east monsoon winds. Brief: Same base map as Fig. 20.9 with arrows reversed, showing the North-East Monsoon blowing from land to sea across the Bay of Bengal and the North-West Monsoon further east; label the Himalayan barrier, the winter low pressure areas and the summer low over northern Australia; India shown to its full extent as officially defined.
Seasons
In regions like the Indian sub-continent which have a true Tropical Monsoon Climate, three distinct seasons can be distinguished: (a) The hot dry season, from March to May. (b) The rainy season, from June to September. (c) The cool, dry season, from October to February.
The main cause for this seasonal climate is the differential rate of heating of land and sea, meaning that land warms and cools faster than water does. Fig. 20.A5 puts the three seasons into the cycle they actually form.
Flowchart
Fig. 20.A5 Caption: The monsoon year turns on one fact — land heats faster than sea, and cools faster too. Nodes: hot dry season, March to May → land heats far faster than the sea → wind turns onshore and the rainy season runs June to September → seasonal winds withdraw, often with violent storms → land cools faster than the sea → wind turns offshore for the cool dry season, October to February → back to the hot dry season in March
In the areas with Tropical Marine type of climate there are two main seasons only, the wet season and the dry season. The wettest months are January, February, March and April, and there is no month without rainfall.
20.6.4 Natural Vegetation
This region is characterised by a wide variety of vegetation types, because the rainfall itself varies so widely across it.
Where Rain Falls All Year
Many of the islands and coastal areas have Tropical Evergreen Rainforests. This vegetation type differs only marginally from the Equatorial Rainforest vegetation, and the trees are tall, above 60 metres in height.
During the summer rains, there is a luxuriant growth of climbers, epiphytes, ferns and bamboos. Epiphytes are plants that grow perched on other plants rather than in the soil. Common species of trees include rosewood, ebony, sisam and bamboo.
Some of the trees have broad leaves, which serve two purposes at once: they give out excess moisture and they receive more sunlight. Islands in the Indian Ocean, the slopes of the Western Ghats, and western parts of Maharashtra, Kerala and Tamil Nadu in India have such forests.
Where There Is A Dry Season
Areas where rainfall is not experienced throughout the year have a marked dry season, and here Tropical Monsoon Deciduous Forests are found. During the dry period, these trees shed their leaves for 6 to 8 weeks to preserve moisture.
Teak, sal, sandalwood and mohua are found in 150–200 cm rainfall areas. These areas include the western side of the Deccan plateau, which is the raised tableland covering most of peninsular India, the North-Eastern Part of the Deccan Plateau, and some areas in Southern China.
20.6.5 Human Adaptations
Agriculture is the main occupation of the majority of people in the Tropical Monsoon region. Crops are grown on small farms in the plains and on terraced hills, where the slope is cut into steps so that water stands on the field instead of running off it.
Tropical agriculture here is dependent on natural rainfall and on a large labour force. That dependence is the weak point of the system, because the monsoon is not regular, and a season that arrives late or thin is felt on every one of those small farms at once.
The major crops grown in the Tropical Monsoon regions include rice, wheat, maize, millet, sorghum, gram and beans. A number of cash crops like sugarcane, cotton, tea and coffee are also grown — cash crops being those raised for sale rather than for the farmer’s own table.
20.7 Mediterranean Region
20.7.1 Location
The Mediterranean Region is so called because the largest stretch of area here lies along the margins of the Mediterranean Sea, the almost enclosed sea between southern Europe, western Asia and North Africa.
The regions having similarities with the Mediterranean region are located on the western margins of continents, in the latitudinal belt between 30° to 45° North and South latitudes. Therefore, these regions are known by the common name of the Mediterranean region of the world, even though most of them lie thousands of kilometres from that sea.
20.7.2 Area
The scattered patches of this climate are the following: (a) Europe: the margins of South Portugal, Bulgaria, France, Greece, Italy, Romania, Serbia and Montenegro, formerly Yugoslavia, and Spain. (b) Asia: Israel, Lebanon, Syria and parts of coastal Turkey, at the eastern end of the Mediterranean Sea. (c) North America: the coastal California around San Francisco. (d) South America: Central Chile, on the Pacific side of the continent. (e) Africa: the coastal area of Algeria, Morocco, Tunisia, Libya, and the region around Cape Town in South Africa. (f) Australia: the South-west area around Perth and southern Australia around Adelaide.
Fig. 20.11 shows how small and how widely separated these patches are. Read down the list and one thing stands out: apart from the Mediterranean Sea itself, every patch sits on the western edge of a continent, and every one lies in the same latitude band in its own hemisphere.
Map
Fig. 20.11 Caption: Regions with Mediterranean climate. Brief: World outline map with the Equator, both Tropics and the Arctic Circle drawn; shade in one dark tint, with a key, the lands around the Mediterranean Sea, coastal California, central Chile, the Cape Town area, and the Perth and Adelaide areas of Australia; India shown to its full extent as officially defined; no country names printed.
20.7.3 Climate
The Mediterranean region lies between the Tropical Deserts on the Equatorward side and the Cool Temperate West Margin region on the Poleward side. Equatorward means towards the Equator, and poleward means towards the pole.
Sitting between the two, it takes something from each. It shares the summer drought conditions of the deserts at lower latitudes and receives its rain in winter. Drought means a long spell in which rainfall is far below what plants and people need. This climate region is therefore also known as the Subtropical Winter Rain Zone, or the Warm Temperate West Margin Climate.
Temperature
Mean summer temperatures range between 20°C and 28°C, and in the hottest month the temperature may touch a maximum of 30°C. Areas close to the oceans experience a lower temperature, because the sea warms more slowly than the land beside it.
In winter, the mean January temperature may be from 6° to 10°C. The temperature at night, in winter, may fall below 0°C, owing to the destruction of forests in the region — with the tree cover gone, there is nothing to hold the day’s warmth near the ground after dark.
The Winds
In the Mediterranean region, the considerable East-West extent of the sea allows the westerly influence of winds to penetrate deep into the Afro-Asian landmass. Water offers no barrier to a wind, so a wind that would be slowed and dried by land travels far along this sea.
On account of the local conditions and the indented coastline, meaning a coast cut into bays and headlands, many local variations of the winds are produced. The Westerlies, the steady winds of the middle latitudes that blow from the west, and the temperate cyclones, which are travelling low pressure systems, move from west to east and bring rainfall in decreasing order as they go.
In addition, cold Polar winds in winter are sometimes drawn into the circulation of depressions, a depression being another name for such a low pressure system. Two of them are the Mistral in the Rhone valley of southern France and the Bora in the northern Adriatic Sea region, and they cause great devastation. Southern winds like the Sirocco in North Africa are hot and dry, and these winds are known as the Khamsin in Egypt. They cause considerable damage to crops.
These patterns of weather also occur in Cape Town in Africa, in California, in Oregon in the USA, and in Central Chile.
Rainfall
The rainfall in the Mediterranean region is experienced mostly in winter, which is the reverse of the pattern in every region studied so far. The annual average rainfall varies between 35 cm to 75 cm, and rainfall is more on the Poleward sides of the region, nearer the belt of the Westerlies.
The effect of this moderate rainfall is marked. The pleasant climate and bright sunny weather, especially in winter, is most favoured by tourists, who flock in great numbers to the region — a case of a climate itself becoming an economic resource.
Seasons
The deciduous type of vegetation and the abundance of flowering plants indicate that there are four climate seasons here — Winter, Spring, Summer and Autumn, or Fall. The Mediterranean climate is well-defined, and so the seasons are also well defined.
The unique quality of winter rain allows plants to adjust their growth with the seasons. In spring, plants flower; in autumn the leaves fall, almost in a rhythmic order. Fig. 20.A6 sets the four seasons out as the cycle the plants are following.
Flowchart
Fig. 20.A6 Caption: In this region the rain and the warmth arrive in different seasons, and plants time their year around the gap. Nodes: winter — Westerlies and temperate cyclones bring the rain, soil moisture is restored → spring — warmth returns while the soil is still damp, and plants flower → summer — drought conditions reach up from the deserts, growth slows and long roots and thick bark hold moisture in → autumn — leaves fall in rhythmic order → back to the winter rains
20.7.4 Natural Vegetation
The vegetation here is of the deciduous type, and it is adapted to withstand a long period of summer drought. So the trees in this region have long roots, which reach water far below the dried-out surface, and thick barks to retain moisture in the dry summer months.
Short stature, moisture retentive trees grow here, especially citrus fruits. Being short is itself an adaptation, because a small tree has less leaf area from which to lose water.
The conditions favourable for vegetation here are a higher intensity of light, a moderate amount of precipitation, and a longer growing season — the stretch of the year warm enough for plants to grow.
The Trees Of Each Continent
The dominant trees in the Mediterranean region of Europe include oak, laurel, cork, oleander, beech and ash, and all these are evergreen trees. Olive is the most common tree. Eucalyptus, introduced from Australia, is also now commonly found. In Europe, most of the natural vegetation has been replaced by cultivated plants like orange, lemon and laurel, so what grows there now is largely what people chose to plant.
The North American Mediterranean region is still rich in flora. There are more dominant species of the chestnut, maple and hemlock. The forests of California are famous for the redwood trees, and there are also a large number of undergrowth plants such as the blue bell.
Towards the Polar regions and in the highlands, coniferous evergreen trees are found — cone-bearing trees with narrow needle-like leaves. Cedar, pine, fir and cypress are the common varieties.
The climatic conditions in the Mediterranean region favour the growth of bushes instead of grasses on the outer edge of forests. Most of the bushes are sweet smelling and scattered in clumps rather than spread evenly. Common species of bushes are lavender, rosemary, myrtle and laurel. Fig. 20.12 shows this mixture of low bushes, scattered trees and dry ground beside the sea.
Diagram
Fig. 20.12 Caption: A Mediterranean landscape. Brief: Source a photograph of a rocky Mediterranean coast with clear blue water, whitewashed buildings on the slope above, and low scattered bushes and short trees on dry ground in the foreground; emphasise the short stature of the vegetation and the bare rock between clumps.
20.7.5 Human Adaptations
Due to the warm, bright summers and the cool, moist winters, a wide variety of crops are cultivated in the Mediterranean Region. The unusual timing of the rain is what makes the mix possible: the water arrives in the season when the heat cannot burn it off at once.
This region is particularly famous for orchard farming, which is the growing of fruit trees as the main crop. A wide variety of citrus fruits like oranges, limes, lemons and grapefruit are grown, and in fact the Mediterranean regions account for 70 per cent of the world’s export of citrus fruits.
Besides citrus fruits, the other important fruits cultivated in the Mediterranean region are olives, grapes, walnuts, hazelnuts and almonds. The other crops grown in the Mediterranean regions include wheat, barley, rice, cotton and tobacco.
20.8 Temperate Grasslands
20.8.1 Location
The continental, or the Steppe-Prairie, type of climatic region is under the influence of the circulation of the Westerly Wind Belt for most of the year.
The Temperate grasslands occupy the interior of the continents in the mid-latitude zone of 40° to 55° North and South. Being in the interior is the key fact about them: they lie far from the sea in every direction, and the winds that reach them have already crossed a great width of land.
These grasslands occupy vast areas in the Northern Hemisphere, where their east-west extension is broader. In the Southern Hemisphere, the grasslands are small in extent, simply because there is less land in those latitudes for them to occupy.
20.8.2 Area
The temperate grasslands carry a different name on almost every continent.
They are found in the following areas: (a) Europe: a narrow belt lying to the north of the Black Sea and the Caspian Sea, and a small area in the Hungarian plains known as the Puszta. (b) Asia: the Manchurian plains of north-east China, Northwest China and Western Siberia. (c) North America: a part of the USA and Canada situated between the Great Lakes and the Rockies, known as the Prairies. (d) South America: parts of Argentina and Uruguay, known as the Pampas. (e) South Africa: the grasslands situated on the plateau which is on the leeward side of the Drakensberg Mountains, known as the Velds. The leeward side is the sheltered side, away from the wind, where far less rain falls. (f) Australia: the grasslands known as the Downs, in the Murray-Darling basin.
Table 20.1 gathers those local names together.
Fig. 20.13 shows the same six areas on the map, all of them well inside their continents.
Map
Fig. 20.13 Caption: Temperate grasslands. Brief: World outline map with the Equator, both Tropics and the Arctic Circle drawn; shade in one dark tint and label the Prairies, Pampas, Steppes, Puszta, Manchurian Grassland, Velds and Downs; India shown to its full extent as officially defined; no country names printed.
20.8.3 Climate
Temperature
The summer temperature varies between 15°C to 25°C and is influenced by several factors. In the hottest month, the maximum temperature during the day time may exceed 30°C.
One may contrast the temperature pattern of the cool temperate continental with that of the cool temperate oceanic — or Calgary in Canada with Osaka in Japan. The chapter gives four readings for the two towns, and setting them side by side shows what distance from the sea does.
The gap between the two towns is wider in winter than in summer, and that is the point. From the above example it is seen that in winter, temperature in the continental region goes considerably below 0°C, while the coastal town never drops that far. In the continental or oceanic region, the duration of sunshine in summer is only a few hours. The annual range of temperature varies between 18°C to 26°C, as in the case of Calgary. What the comparison cannot settle by itself is how much of the difference is distance from the sea and how much is the difference in latitude between the two towns.
It is not the annual range or the diurnal range — the swing between day and night — that matters here, but the great variety of weather characteristic of temperate latitudes. This rarely happens in the tropical and subtropical zones, where one type of weather can hold for weeks.
In the Southern Hemisphere, winters are less severe owing to the moderating effect of the oceans, which surround these small patches of grassland on almost every side.
Rainfall
There are variations in rainfall owing to the influence of the Westerly winds in the Northern Hemisphere. In the Southern Hemisphere, ocean currents and maritime influence — the effect of a nearby sea — play the major role instead.
There are great variations in rainfall, which varies between as low as 20 cm to 60 cm. The rainfall is of the convectional type, accompanied by lightning and thunder.
In the Calgary region of Canada, where the January temperature is −10°C, rain with melting snow is experienced in winter. In North America, local winds like the Chinook bring about a sudden increase in temperature for a few days, and the snow cover thus melts away.
20.8.4 Natural Vegetation
On account of the low rainfall, both coarse and tall grass, as well as short and soft grass, is the characteristic vegetation of the continental Steppe climate type.
The Temperate grasslands, or Steppes, differ from the Tropical Savannas in an important way. The Steppes are practically treeless and their grasses are much shorter, while the Savannas carry scattered short trees and low bushes between grasses that reach 3 to 6 feet. The reason lies in the climate: the Steppes have scanty rainfall, long droughts and severe winters, and a tree cannot get through all three. Both regions are grasslands, and in both the grass is what survives where trees cannot.
Wildlife
The herbivorous animals, which feed on grass, are found in large numbers here, as a treeless grassland is one enormous supply of food at ground level. Common herbivores include the bison in the North American prairie, and other animals include antelopes, wild asses and horses. The Kangaroo is found in the Australian grasslands.
The carnivores, meaning the flesh-eating animals, are mostly rodents and reptiles. Fig. 20.14 shows the prairie country these animals graze.
Diagram
Fig. 20.14 Caption: A prairie landscape. Brief: Source a photograph of open rolling prairie grassland at low sun, with bison grazing near a stream and low hills behind; emphasise the unbroken grass cover and the near-absence of trees.
20.8.5 Human Adaptations
The Temperate grasslands are known as the ‘granaries of the world’, a granary being a store of grain. They are ideal for extensive wheat cultivation — farming that works large areas with machinery rather than working small plots intensively by hand.
They produce the greatest quantity of wheat per capita amongst the world’s wheat-growing nations where irrigation is available. Per capita means per person, so the figure reflects a small population working a very large area, not simply a heavy total harvest. Cotton and maize are also grown.
20.9 The Taiga Region
The Taiga region is also known as the Cool Temperate Continental type, or the Siberian Type. All three names describe the same thing from different angles: a cold interior, far from any warming sea, carrying an unbroken forest of cone-bearing trees.
20.9.1 Location
This region lies between 55° and 70° in the Northern Hemisphere. Towards the poles, it merges into the Arctic Tundra of Canada and Eurasia at around the Arctic Circle, so its northern edge is not a line but a slow thinning of the forest.
Due to the strong oceanic influence in the far south, the severity of the winter and the coniferous forest are found only on the mountainous uplands of southern Chile, New Zealand, Tasmania and south-east Australia. In those places it is height, not distance from the sea, that supplies the cold.
20.9.2 Area
The region is found in these areas: (a) Europe: Finland, the northern part of Russia, Sweden and parts of Norway. (b) North America: Southern Canada and southern Alaska. (c) Asia: Northern Siberia and the Sakhalin islands, off Russia’s Pacific coast.
Fig. 20.15 shows how these join up into one long band across the top of the world.
Map
Fig. 20.15 Caption: The Taiga region. Brief: World outline map with the Equator, both Tropics and the Arctic Circle drawn; shade in one dark tint a continuous band across southern Canada and Alaska, Scandinavia and northern Russia through to eastern Siberia; India shown to its full extent as officially defined; no country names printed.
20.9.3 Climate
The Siberian type of climate is experienced only in the Northern Hemisphere. This is because of the narrowness of the southern continents in the high latitudes — at 55° to 70° South there is almost no land, only ocean.
Temperature
The Siberian type of climate is marked by severe winters of long duration and a cool, brief summer lasting only 3 to 4 months. Almost two-thirds of the year, therefore, is winter.
Heavy snowfall occurs during the winter. Frost occurs as early as August, and by September lakes and ponds become frozen — the cold arrives while the calendar still says summer elsewhere.
Rainfall
The rainfall varies from 25 to 100 cm. It is well distributed throughout the year, with a maximum in summer, so there is no dry season here of the kind found in the savanna or the Mediterranean lands.
In winter, the precipitation is in the form of snow, as mean temperatures are well below freezing point. Cold polar anticyclones, which are high pressure systems with air flowing outward from their centres, blow away vast masses of snow and spread it over large areas. They are called the Blizzards in Canada and the Burans in Europe and Asia. Fig. 20.A7 sets the year out as the cycle it forms.
Flowchart
Fig. 20.A7 Caption: In the taiga the growing season is short and the frozen season is long, and the two repeat without a dry spell between them. Nodes: brief cool summer of 3 to 4 months, with rainfall at its maximum → frost begins as early as August → lakes and ponds freeze by September → long severe winter, precipitation falling as snow → Blizzards and Burans sweep the snow across large areas → thaw → back to the brief cool summer
20.9.4 Natural Vegetation
The main vegetation of the Siberian type of climate includes evergreen coniferous forests, and these forests are found in a continuous belt across North America, Europe and Asia. One vegetation type circles the globe here, which happens nowhere else.
The coniferous forests of Eurasia and North America are the richest sources of softwood, the timber taken from cone-bearing trees, which is lighter and easier to work than the hardwood of broad-leaved trees. It is used in furniture making, building construction, and the paper and pulp industries.
The major trees of the coniferous forests are pine, fir, spruce, cedar and hemlock. A forest that runs unbroken for thousands of kilometres, made of only a handful of species, is what makes cutting on an industrial scale possible here — a single mill can draw the same timber year after year.
20.9.5 Human Adaptations
The Taiga region is sparsely populated, meaning few people live in each square kilometre of it. Farming does not constitute an important economic activity, as the land remains covered with snow during the long, cold winter season.
Only in the sheltered valleys and the lands bordering the Steppes are some crops grown, such as barley, oats, rye, potatoes and beetroots. These are hardy crops that will ripen inside a short summer, and they grow where the land is either shielded from the worst winds or warmed slightly by its position further south.
20.10 The Tundra
The Tundra type of climate is also known as the Arctic or Polar Type. In fact, Tundra is the name of the vegetation type characteristic of the region, and the word has been derived from a Russian word which means a flat treeless plain. The vegetation has given its name to the climate here, exactly as the classification in section 20.2 said it would.
20.10.1 Location
This region lies roughly beyond 65° North, on the northern side of the Taiga region. It is the last belt before the ice, and everything about it follows from how little heat reaches it.
20.10.2 Area
The region is found in these areas: (a) Europe: Greenland, Iceland and Northern Scandinavia. (b) North America: Northern Canada and Alaska. (c) Asia: Siberia.
Fig. 20.16 shows the Tundra as a ring of land around the Arctic Ocean.
Map
Fig. 20.16 Caption: The Tundra region. Brief: World outline map with the Equator, both Tropics and the Arctic Circle drawn; shade in one dark tint the northernmost fringes of Canada and Alaska, Greenland, Iceland, northern Scandinavia and the Arctic coast of Siberia; India shown to its full extent as officially defined; no country names printed.
20.10.3 Climate
The Tundra type of climate is found mainly north of the Arctic Circle in the Northern Hemisphere. The climate is characterised by long, severe winters and cool, brief summers.
Temperature
The region is marked by weeks of continuous darkness. At the North Pole, there are six months without daylight in winter — the single fact that shapes everything else here.
The region has a low annual range of temperature. This is because temperatures remain low all year: the Sun stays low in the sky, and much of the warmth of its faint rays is either reflected by the ground snow or used up in melting the ice, rather than heating the ground. The temperature in the warmest month, June, seldom rises to more than 10°C, and in mid-winter, in January, temperatures are as low as −37°C.
Rainfall
Due to the low rate of evaporation and the lack of moisture in the air, no convectional rainfall occurs here — cold air simply cannot hold much water vapour to give up. The rainfall is cyclonic in form, meaning it comes from travelling low pressure systems rather than from air rising off a heated surface.
Most of the rain falls in summer. In coastal areas, where cyclones are strongly felt, most of the rain falls in winter, and here it exceeds the normal limit of 12 inches. In winter, the precipitation takes the form of snow, which does not melt due to the severe cold, so it accumulates instead of running off.
20.10.4 Natural Vegetation
Due to the extremely harsh climatic conditions, only a few plants can survive in the Tundra. There are no trees in the Tundra region because of the very short growing season of three months and the warmest month having only 10°C temperature. A tree needs more warmth, and more time, than the year here can supply.
The most common type of natural vegetation includes mosses, lichens and sedges — low, ground-hugging plants, of which lichens can grow on bare rock itself. Some hardy grasses grow in the more favourable coastal lowlands, where the sea keeps conditions slightly milder. Fig. 20.A8 sets out why the plant list is so short, and Fig. 20.17 shows the country these plants must hold on to.
Flowchart
Fig. 20.A8 Caption: Three conditions between them rule out trees and leave only the lowest-growing plants. Nodes: growing season of only three months → warmest month reaching just 10°C → precipitation lying as unmelted snow → too little warmth and time for any tree → mosses, lichens and sedges cover the ground; branch: more favourable coastal lowlands → hardy grasses grow as well
Diagram
Fig. 20.17 Caption: A tundra landscape. Brief: Source a photograph of a snow-covered treeless slope with dark rock breaking through the snow and a figure walking for scale; emphasise the complete absence of trees and the bareness of the ground.
20.10.5 Human Adaptations
The permanently snow-covered Tundra region is too cold for the cultivation of any crop. Traditionally, it is inhabited by a few semi-nomadic people, who move between settled camps with the seasons rather than staying in one place all year.
They live as hunters, fishermen and gatherers, and they derive their food from fish, seals, walruses and polar bears. They hunt reindeer and other animals, which provide them with milk, meat, fat, skins and bones. Almost nothing of an animal is wasted, because in a land with no crops and no timber, the animal supplies the food, the clothing and the raw material all at once. They also rear fur-bearing animals on a commercial scale.
However, in the southern part of the Tundra region, a new variety of wheat which has a short maturing period is being cultivated. The maturing period is the time a crop needs between sowing and harvest, and shortening it is what lets a crop fit inside a three-month summer. It is a good example of the point made in section 20.2: with modern technology, the old limits set by climate are being loosened, though not removed.
20.11 Summary
- A natural region is a part of the Earth’s surface which has a comparatively high degree of uniformity of structure, surface form and climate within it.
- Every natural region is a homogeneous unit, but the uniformity is a matter of degree.
- Slight variations are present within each region.
- The variations between one region and the next are far more pronounced, and that is where the boundary is drawn.
- Climate is the basic factor on which the world is divided into major natural regions, because it influences the soil, the flora and fauna, and the vegetation.
- The regions are usually named after the vegetation type prevalent in them, since the plants are the visible record of the climate.
- Vegetation depends not only on total annual rainfall but on its relation to temperature and its distribution, and in high latitudes less rainfall is needed because evaporation is weaker.
- The sorting of combinations of climatic elements into types is called climatic classification, and the climatic zones are based on temperature, pressure, winds and humidity, landforms, weathering and soils, vegetation and wildlife, water run-off, and cropping seasons and methods.
- Human response is closely tied to climate where the primary activities dominate, though modern technology is reducing these differences and economic status now decides much of what is done in a region.
- The Equatorial Region lies between 0–10° north and south of the Equator.
- Temperature ranges between 25°C and 30°C, and convectional rainfall of 175 to 250 cm falls in the afternoon through the year.
- Its dense rainforest, or Selvas, grows in four layers — emergent, canopy, understorey and forest floor — and is called the ‘Lungs of the World’.
- People practise hunting and gathering and shifting cultivation, and plantations of natural rubber and cocoa are the most outstanding.
- The Tropical Grasslands, or Savannas, lie roughly between 7° and 20° north and south of the Equator.
- Summers are hot and wet, winters cool and dry, and the hottest month comes just before the rains.
- Tall coarse grass 3 to 6 feet high grows with scattered deciduous short trees, and baobabs and bottle trees store water in broad trunks.
- They are the ‘natural cattle country’, and also carry plantations of cotton, cane sugar, coffee, oil palm and groundnuts.
- The Tropical Deserts lie between 15° and 30° north and south, on the western margins of continents.
- The Trade Winds shed their moisture on the eastern margins and arrive dry, and cold ocean currents add to the dryness.
- Rainfall is under 25 cm a year, summer temperatures reach 30°C to 45°C, and the bare ground gives extremes of temperature.
- Xerophytic plants store water in their stems, and crops can only be grown by irrigation, from rivers such as the Nile or from an oasis.
- The Tropical Monsoon type of climate is found in Southern Asia, with onshore wet monsoons in summer and offshore dry monsoons in winter.
- Rainfall varies from 75 to 200 cms and is caused mainly by the differential rate of heating of land and sea.
- The Indian sub-continent has three distinct seasons — hot dry, rainy, and cool dry.
- Tropical Evergreen Rainforests grow where rain falls all year and Monsoon Deciduous Forests where there is a marked dry season.
- The Mediterranean Region lies between 30° and 45° north and south, on the western margins of continents, with summer drought and winter rain of 35 cm to 75 cm.
- Trees have long roots and thick barks to survive the summer drought, and olive is the most common tree.
- Orchard farming of citrus fruits dominates, and the region accounts for 70 per cent of the world’s export of citrus fruits.
- The Temperate Grasslands occupy the interiors of continents between 40° and 55° north and south, and are known by different names on different continents.
- They are practically treeless with much shorter grasses than the Savannas, because of scanty rainfall, long droughts and severe winters.
- They are the ‘granaries of the world’, ideal for extensive wheat cultivation.
- The Taiga region lies between 55° and 70° in the Northern Hemisphere only, because the southern continents are narrow at these latitudes.
- Winters are severe and long and the summer lasts only 3 to 4 months.
- Evergreen coniferous forests form a continuous belt and are the richest source of softwood.
- The Tundra lies roughly beyond 65° North, on the northern side of the Taiga.
- The warmest month seldom exceeds 10°C and mid-winter falls to −37°C, so no trees grow and only mosses, lichens and sedges survive.
- People live as hunters, fishermen and gatherers, and a short-maturing wheat is now grown in the south of the region.
Flowchart
Fig. 20.A9 Caption: One factor, climate, sorts the world into eight regions, and latitude is the thread that runs through the whole list. Nodes: climate, the basic factor → low latitudes branch: Equatorial 0–10° / Tropical Grasslands 7–20° / Tropical Deserts 15–30° on western margins / Tropical Monsoon in southern Asia → middle latitudes branch: Mediterranean 30–45° on western margins / Temperate Grasslands 40–55° in continental interiors → high latitudes branch: Taiga 55–70° North / Tundra beyond 65° North → each region takes its name from the vegetation its climate produces
What This Chapter Cannot Tell You
The world maps in this chapter are drawn at a scale where a whole country is a few centimetres wide, so every boundary on them is a simplification. On the ground one region shades into the next across a wide belt, and the chapter itself shows why: Mount Kilimanjaro carries snow inside the equatorial belt, and East Africa is cooler and drier than the lowlands around it.
The figures given for each region are averages and ranges, not the weather of any particular year. A stated rainfall of 75 to 200 cms says nothing about the year the monsoon arrives late, which is exactly the year that matters most to the farmer.
Nor does a natural region describe the people in it. The classification tells you what the climate makes easy or difficult, not what any community has actually chosen or been able to do with it — and, as section 20.2 notes, technology and economic status are steadily loosening that link.
20.12 Check Your Concepts
Look at Fig. 20.2. Name the four layers of the equatorial forest, working from the forest floor upward, and explain why the plants of the understorey have larger leaves than those higher up.
This chapter gives the hottest month at Calgary as 16.4°C and its coldest month as −10.0°C, while at Osaka the figures are 27.6°C and 4.4°C. Work out how much warmer Osaka is than Calgary in the coldest month, showing your arithmetic, and state what the answer suggests about the effect of being far from the sea.
In winter the Trade Winds over India blow from the land to the sea, yet the Coromandel coast still receives rain in that season. Set out, step by step, how this happens.
The Taiga type of climate is found only in the Northern Hemisphere. Explain why, and state what would have to be different about the southern continents for a taiga to develop there as well.
Explain how a natural region is a homogeneous unit.
Give a reason for each of the following:
- There is a uniformly high temperature in the Equatorial region.
- Though Mount Kilimanjaro is located close to the Equator, its peaks remain covered with snow throughout the year.
- The Equatorial region is called the ‘Lungs of the World’.
Give a reason for each of the following:
- In the Tropical Desert climate region, the Trade Winds are dry.
- In the Indian subcontinent there are three distinct seasons.
- Agriculture is the chief occupation in the monsoon region.
How are the Temperate Grasslands different from the Tropical Savannas?
In which natural region of the world is India located? Which characteristic features of this type of natural region are found in India?
On an outline map of the world, mark one region each with the following climates:
- Tropical Monsoon type.
- Tropical hot desert type.
- Equatorial type.