When we see endless land, covered with sand, we immediately think: desert. But actually, this is not how all deserts look like so I feel, I should clarify what a desert ecosystem is.
Well, the answer is not so simple. There are many factors, like precipitation, temperature, location and human activity that define a desert, and they can look very different too.
Deserts are pieces of land, where very little participation occurs. But how much are we talking about when we say – very little? It’s less than 200 mm a year! And there is more! The deserts are divided into two groups – arid and semi-arid deserts. An arid desert gets about 25-200 mm of participation per year and the semi-arid get even less than that! The driest desert on Earth is the Atacama desert (Chile), that only gets 1 mm of participation per year!
The next factor is the average annual temperature. The magic border that defines a desert as one with cold or hot climate is 18°C. The most well known hot climate desert is Sahara, but there are also others such as Libyan, Namib, Arabian and great Victoria desert. The hot deserts are also known as the hottest, driest and sunniest places on Earth.
On the other hand, there are deserts with cold climate. Even though it can get very cold, snow or any other form of precipitation is very rare. This makes them drier than the deserts with a hot climate. The most well-known desert with cold climate is the Gobi desert (China and Mongolia). Other deserts, that share the characteristics are Patagonian, Katpana and the Great Basin desert. When talking about cold deserts, we should also mention the Arctic and Antarctic. These two do not classify as deserts with cold climate, but as deserts with polar climate (summer temperatures are around 10°C).
Why are deserts mostly sandy?
Remember when I talked about big temperature changes? They are the secret factor behind the mysterious looks of many deserts. Since the temperatures vary between 50 °C and -18 °C, the tiny cracks in rocks form. In time, the rock slowly breaks apart and the end result of the process has become the face of deserts. The particles are often being relocated by the wind. This event is known as a dust- or sandstorm. These tiny particles also play a huge role in further erosion (shaping of bigger rocks).
Locations of deserts
The locations of deserts are not picked randomly by nature but occur in the areas where the conditions enable them. We could say that in a way, the locations are chosen by the – so-called – Coriolis effect. This effect is just a fancy name to describe the movements of objects on a rotating body (in this case – Earth). This effect is responsible for things like winds, water currents, pressure changes etc. and therefore affects the rate of precipitation, temperatures, and much more. An example I can set is the high pressure that occurs in some areas. High pressure “scares away” the clouds, that also take the water that they carry with them.
There are some guidelines to where the deserts occur. The hot deserts mostly appear in 30 south-30 north latitudes. In this part of the Earth, the sun is directly overhead at noon at least once a day and the power of rays is the strongest. On the other hand, the colder deserts usually occur in latitudes greater than 30. They have cold climate because of the ocean currents, that bring the cold water close to the surface at the shoreline. The cold water cools the air, which is then moving toward the warmer area (land) in order to keep balanced temperatures. At land, the air cools down and therefore provides a cold climate for the desert.
There can also be geographical barriers that end with a formation of a desert. One of these barriers are the high mountains. In order for a cloud to pass them, they need to leave all the water on the side of the mountain they came from (high pressure). This effect is known as rain shadow effect and the areas, where it occurs have very little precipitation. Another way a desert can occur due to the geographical barrier is when we speak of a large land mass. The winds that blow from sea to land are carrying moisture, that is slowly being lost with traveled distance. At some point, there is no more moisture and therefore a desert occurs.
However, not all deserts occur naturally. Some of them are made by human hand and some expand very quickly due to our mismanagement of land. We mismanage land mostly by clearing it (for wood, agriculture, solar factories, etc.) and therefore influencing its natural cycles (water cycle, nutrient cycle, food webs etc.). The main reason for the expansion of desert is the absence of plants, that tend to grab soil with their roots and participate in the water cycle. When they are gone, wind and water slowly erode the unprotected soil. With this process, a lot of fertile soil, land and living habitat is lost.
The two biggest desserts in the world are the Antarctic (14.200.000 km²) and Arctic (13.900.000 km²) desert. The third biggest desert is the sandy desert in Africa – The Sahara desert. It covers about 9.100.000 km² of land and is gaining about 50 km of land every year. However, this Is not the fastest expanding desert on Earth. The champion here is the Gobi desert, that covers about 1.300.000 km² and expands by 3600 km² every year!
I probably don’t need to mention that this is very bad news for all the people living in these areas. The expansion makes it impossible for them to farm the land, moreover, it presents a health hazard and forces them to leave their homes. To fight this, there are some ongoing projects to help fight the desertification. The main tool used in these projects are the trees, that can survive severe droughts and grow quickly. By growing they act as a live fence, protecting the land behind them. Studies show, that with this project, we have been able to largely prevent the further expansion of desert. They also show, that the land has become more hostile and even enables people to grow their own food! We need to keep in mind, that even though the results are very positive, the projects must not stop or everything will go back to the way it was.
What do you think of desert ecosystems? Do you find them fascinating or boring? Do you have any experience with them? Let me know your thoughts in the comments- I would be very happy to read them!
Related read: The great green wall – African project