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Facts about Tropical Rainforest, Savanna and Desert Landscape (climate, culture, trees, weather and much more)
[EDITOR'S NOTE: For the first part to understand humidity condensation and everything else better click here.]
Before going into deeper detail about the tropics, savannah and the desert I would like to take a quick look on the weather conditions:
- wet equatorial climate: This climate is coined with the same rainy weather every day the whole year round (no seasons!). The area is the tropical rainforest (equator) and the temperature fluctuates between 2-5°C. The precipitation is always more than 200cm per year and there are no or at maximum 2 dry months.
- tropical wet-dry climate: This climate has 2 seasons, which is divided into a rainy and a completely dry season. The temperature can vary from 4-8°C and the precipitation lies in between 100-200cm. The area is the part of the savannah that lies most closely to the tropical rainforest. It has 3-5 dry months.
The dry savannah falls into this category too, having a precipitation from 50cm to 100cm per year. The temperature can vary over the year 5°C up to 10°C. Usually, it has 6-7 dry months.
The thorn or semi-savannah is the part of the savannah, which lies most closely to the desert and also features desert like temperature etc. The temperature fluctuates 8°C up to 15°C. It has a rather low precipitation (20-50cm per year) and 8-10 dry months.
- desert climate: The temperature of the desert can have a difference over the year of 10°C up to 20°C. There is no precipitation or at maximum 20cm per year. It has 11 dry months or even 12.
- Mediterranean climate: This climate situation does not fall into the area between the tropics and the desert, but nonetheless, it is a very important climate. The temperature can vary from 10°C up to 15°C on a day (or over the year). The precipitation is 10-40cm per year and it has 4-10 dry months. In summer, it has the climate situation of the tropical climate.
And now, let us take a deeper look into those specific areas. But before, we have first to learn something about the trade winds, since they are a very, very important feature of the equator.
The sun warms up the equator zone (about 0° latitude). Consequently, the warmed up zone becomes a low pressure area, since the hot air at the equator starts rising, thus becoming cooler while rising, and goes to the less warmed up zones, which are ~30° N/S. Resultantly, those become high pressure areas. When the air is descending, it becomes warmer. Winds are always blowing from high pressure areas to low pressure areas. In this case, it is also true and when they reach the equator respectively the low pressure zone they meet there and are “neutralized”. This place is called Intertropical Convergence Zone (ITCZ). Due to the Coriolis force they are deflected easterly, resulting into north/south-eastern trade winds and converging to the ITCZ. Between 5° N/S - 30° N/S there are often strong warm winds, whereas in the ITCZ virtually no winds are blowing.
Epithytes and Lianas
Basics about the Tropics
Climate: The tropical rainforest shows a very humid and warm weather conditions (25°C). Every day is the same day in the tropical rainforest. The mornings are usually clear, but in the noon, it gets cloudy already and the afternoon is coined with heavy rainfall and occasional short thunderstorms. The evening gets clear again and so is the night too. Due to the angle, which the sunlight hits the tropical rainforest, it becomes warm quite fast. The air starts to rise and reaches its dew point (saturation point) and it will finally start to rain massively. From this process also originates the trade winds.
Epiphytes and Lianas:
Epiphytes are plants that grow onto other plants and so live in symbiosis with them. They do not harm their “host” and that is why they are not classified as parasites. Since the woods are very dense in the tropics, sunlight hardly reaches the ground and that is why some plants had to develop a new technique in order to get more sunlight. But this also has some problems, namely the following: Since it has no roots that go into the ground, such plants can be fairly instable and they have a big problem to get water and nutrients.
Strategies such plants have developed:
One is to have some little holes in their leaves, what enables the uptake of water and nutrients.
Another is to build a “container” with their leaves, where water can be collected and also dead animals. Microorganisms decompose those dead animals and the plant takes advantage of the waste material.
Other plants have an extended root tissue, with what it is easier able to take up water and material.
Also, some plants are able to close their exchange openings (stomas) which postpone the CO2 uptake and minimize the loss of water this way.
A last strategy is to have thick leaves and swellings. This is beneficial for the plants too, since it can store water and nutrients for bad days there.
Lianas have also the problem of the gathering sunlight, but they developed a technique opposite to the one of the epiphytes. Unlike the epiphytes, they do not live on other plants, but on the ground. This gives them the advantage of having a secure water and nutrient source, but the sunlight problem remains. Lianas have a special stem that allows them to grow vertically on rocks, bigger plants or other surfaces. Otherwise, they possess climbing organelles that emits a glue-like substance and can so make their way up to the heights, where the sunlight is easily reached.
Basics about the Savannah
Climate: We already looked at it in general, but let us take a closer look at the two different seasons.
Dry season: This season lasts from November to April. The temperature is always at least 20°C and the precipitation is less than 6cm. The humidity level is low and watering holes as well as rivers dry out completely. There are occasional bushfires and grazing animals are forced to migrate into more grassy lands. This also leads to many problems for farmers, since agriculture is impossible to do and farmers are forced to move into the already overpopulated towns, what again enhances the problem with diseases.
Wet season: That season last from May to October and the precipitation is always over 6cm. In this season, there are heavy rainfalls. It is always hot and humid. Due to the heavy rainfall, fresh and groundwater quality improves drastically and the soil is enriched with nutrients. Vegetation is possible, but due to the extreme rainfalls, floods often may happen, rivers can overflow and the soil is repellent to water, because of the bushfires in the dry season. Many animals have to leave for higher heights, but there are also other animals and insects that profit from it. One of them is the Mosquito, what reinforces the problem with Malaria.
Trees: There are three different types of trees in the savannah, where one is closest to the desert (xeric shrub land, which consists of cactuses and thorn bushes), the semiarid savannah, that is made of baobab trees and palm trees (which can grow up to 20m in height) and the semi humid savannah which is the closest to the tropical rainforest and is the home of teak trees, bamboo and palm trees (which can grow up to 40m in height). Although they live on different places, these trees have one thing in common. They all live in symbiosis with bacteria in order to get more nutrients. Their roots do not grow deeply in the ground, but are widely spread and so they can gather and store more water. This is a technique which enables them to withstand longer dry periods. Their leaves are usually small and hairy, waxy or thorn shaped. This minimizes the water loss and those leaves can emit or store a poison in order to be protected against animals and insects.
Nomads/tribes in the savannah: The Yanemamis are the most common tribe in the savannah. This indigenous culture consists of 40-300 people. They live in villages that only have one big round roof (Shabanosare). The whole tribe lives under such a Shabanosare, where every family has its own compartment. After some years, they have to leave their villages. One reason is that the Shabanosare get damaged from time to time and another reason is that there are not so many animals left anymore, which can be hunted. The Yanemamis eat fish, monkeys, local fruits, maggots, insects and the heart of palms. The use bow and arrows, blowpipes and spears to hunt. Men are only dressed with a rope round their waist, whereas women wear coloured waistbands. Their culture is said to be one of the most primitive ones. Men can have several women. Male offspring is preferred, what often leads to a lack of women. That is why other females are often kidnapped from other tribes, what results into wars between tribes. Yanemamis are animists. This means they believe that every being and object has a soul.
Such indigenous tribes have many problems nowadays. They partly lose their homes, because of gold diggers. Many diseases were introduced by the gold diggers, what lead to a massive death rate, since they were not immune to the foreign illnesses. Also, the rainforest has been chopped down progressively and animals were killed, what destroyed the environment of those tribes and makes them quite hard to survive nowadays.
Laterite: Those are special reddish stones that are created by a process called “laterization”. Rocks on the surface of the ground break down due to high temperature and pressure. Water carries away many minerals of the former rock like Potassium, Magnesium, Calcium, Silicium and others. Only iron and aluminium remain as they less soluble (or not at all) in water. The change of the wet and dry seasons and the low topographical relief (means no erosion) are two other necessary conditions of the formation of laterites. They can be used for building blocks in houses, but also for roads as Kenya does. Moreover, they have the usage of an aquifer in rural areas and is also a source for iron aluminium and nickel.
Desert types and Pictures
Basics about the Desert
Climate: A day in the desert can be more than 45°C hot! And in the night, it gets fairly chilly (under 0°C). There is almost no precipitation. In some places in the desert it only rains every twenty years! The equator heats up very fast due to the intense sun rays and the angle they fall in. Hot air rises very fast and the process of the trade winds begins. This leads to an increase of moisture -> no precipitation. This air goes back as trade winds to the desert.
Nomads in the desert: Nomads are people that more or less travel constantly, depending on the season and their environment, and take all of their belongings, animals and family with them. One of such nomads is the Bedouins. They herd animals like sheeps, goats and dromedaries. Dromedaries are even of a special importance to them, because they are their main riding and transport animal and dromedaries also provide the Bedouins with wool and leather and are even a medium of exchange. Their nurture consists mainly of bread, butter, milk, dates, cheese, vegetables and if they are close to the see, also of fish and seafood and they also drink coffee and tea (alcohol is not one of their preferred drinks and also does it only appear very seldom in their inventory). They depend on trading with other people from the town and often trade, for example, carpets, which the women make. The Bedouins have a very strong community feeling. If there is a disagreement, the whole tribe is concerned. They are very proud of themselves and need their freedom and independence from the government. Marriages are a special case, because only people in the same tribe can be married to each other or another accepted tribe.
Types of deserts: There are three different types of deserts.
- Hamada (death) desert: This type of desert has 70% of the total desert area. It is nearly impassable even with camels or vehicles and extremely dangerous since it consists of sharp rocks and big stones. There is almost no vegetation and the life-threatening Wadis (dry riverbeds that can get very high for a short time when it rains). The landscape is formed by weathering and deflation.
- Serir (depressed area) desert: 20% of the whole desert is a Serir desert. It consists mainly of pebbles with a radius of 2mm to 60mm. It is less dangerous than the Hamada desert and very easily passable. Its landscape is, like in the Hamada desert, formed by weathering and deflation.
- Erg (sand sea): The Erg desert is the type one usually imagines a desert. It has beautiful dunes that can reach a height of 200m. The dunes move with the wind. This process is called saltation and can travel several kilometres. Unfortunately, it only has 10% of the total desert area.
How to make a living in the oasis: There are four different types of oasis:
- groundwater oasis
- river water oasis
- spring water oasis
- artesian well oasis
The land around the oasis is very fertile. This allows many plants to live there. One can plant vegetables, corn, rice, orange, apple, lemon and peach trees and also date palms. Date palms are very important for the trees on an oasis. Date palms can grow very high and therefore are able to protect to other smaller trees from too intense sunlight. Their roots grow up to 30m deep in the soil and therefore it is no problem for them to reach the groundwater. Not only are they helpful for the other trees, but also are humans able to use almost everything of the date palm. The dates are exported into foreign countries for a high price, but nomads, for example, eat them as well. The date kernels are crushed and used as food for the animals of the nomads. The big leaves can be used to make brooms and baskets and the delicious palm wine comes directly from the juice of the stem.
Another important factor to make a living in the oasis are camels. Their ability to survive several weeks without water in the desert makes them ideal for transport.