About half of southern Africa is semi-arid and thus at risk of desertification. The area already transformed into desert-like conditions is not accurately known because uncertainty surrounds the precise definition of a desert, and what the original state of the vegetation was in the semi-arid areas of southern Africa.
The areas which are known to have deteriorated this century are mainly on the edges of the southern Kalahari. The deterioration of the Karoo is less well established. It is possible that desertification of the Karoo began in the last century, when sheep were first introduced, and before good records were available for the area.
In recent years the introduction of artificial water points into the Kalahari within Botswana, together with the widespread erection of veterinary fences, has led to the rapid desertification of huge areas. Similar schemes have had the same effect in the southern Kalahari within South Africa and Bophuthatswana.
CAUSES OF DESERTIFICATION
Causes by Climatic Variations
- Africa’s geography makes it particularly vulnerable to climate change, and seventy percent of the population rely on rain – fed agriculture for their livelihoods. Tanzania’s official report on climate change suggested that areas that usually get two rainfalls in the year will probably get more, and those that get one rainy season will get far less. Southern Africa is a region will receives seasonal rainfall therefore will receive far less rainfall.
- Increase in Temperature
Global Warming is the leading cause in climate change throughout the world. The natural greenhouse effect makes life on earth possible. Gases in the atmosphere such as carbon dioxide and water vapour trap heat. However humans have increased greenhouse gas emissions as a result of burning fossil fuels and deforestation. The result is that more heat is being trapped and the atmosphere is getting hotter. As a result global warming increases temperatures causing droughts and various other disasters. This natural phenomenon increases the desertification and forces it to spread worldwide. The increase in temperature causes various factors which are essential in increasing desertification.
Causes by Humans
- Overgrazing is one of the major causes of desertification worldwide. Plants of semi-arid areas are usually adapted to being eaten by sparsely scattered, large, grazing mammals which move in response to the patchy rainfall common to these regions. Early human pastoralists living in semi-arid areas copied this natural system. They moved their small groups of domestic animals in response to food and water availability. Such regular stock movement prevented overgrazing of the fragile plant cover.
In modern times, vast changes have forced overgrazing. The use of fences has prevented domestic and wild animals from moving in response to food availability, and overgrazing has often resulted. However, when used correctly, fencing is a valuable tool of good veld management.
The use of boreholes and windmills also allows livestock to stay all-year round in areas formerly grazed only during the rains when seasonal pans held water. Where not correctly planned and managed, provision of drinking water has contributed to the massive advance of deserts in recent years as animals gather around waterholes and overgraze the area.
- Cultivation of marginal lands. Farmers use lands on which there is a high risk of crop failure however there is a very low economic return, for example, some parts of South Africa where maize is grown.
- Destruction of vegetation in arid regions, often for fuelwood. Also destruction of forests known as Deforestation creates a bigger chance of Desertification occurring.
- Poor grazing management after accidental burning of semi-arid vegetation.
- Incorrect irrigation practices in arid areas can cause salinization, (the build up of salts in the soil) which can prevent plant growth. When the practices described above coincide with drought, the rate of desertification increases dramatically. Increasing human population and poverty contribute to desertification as poor people may be forced to overuse their environment in the short term, without the ability to plan for the long term effects of their actions. Where livestock has a social importance beyond food, people might be reluctant to reduce their stock numbers.
EFFECTS OF DESERTIFICATION
Loss of life
Desertification causes nutrient – rich soil to be blown or washed away reducing the ability of land to support life, affecting wild species, domestic animals, agricultural crops and people. Problems such as starvation and food shortages would become greater.
Overfarming or drought can change the soil so that rain no longer penetrates, and the plants lose the water they need to grow. If the changing force is lifted (drought ends or cattle are removed) the land cannot recover and is therefore desertified. The loss of productive land for a season or even a few years is one thing, but to lose it effectively for ever is clearly far more serious.
Rainfall records compared to satellite vegetation measurements since 1981 show reduced rainfall and vegetation cover during the severe droughts during the 1980s (blue line). Researchers concluded that any permanent desertification was limited to localized areas.
Increase in soil erosion
Desertification is a man-induced process that leads to soil nutrient depletion and reduction of biological productivity. The reduction in plant cover that accompanies desertification leads to accelerated soil erosion by wind and water. South Africa loses approximately 300-400 million tonnes of topsoil every year. As vegetation cover and soil layer are reduced, rain drop impact and run-off increases.
Disasters & Plant Production
Water is lost off the land instead of soaking into the soil to provide moisture for plants. Even long-lived plants that would normally survive droughts die. A reduction in plant cover also results in a reduction in the quantity of humus and plant nutrients in the soil, and plant production drops further. As protective plant cover disappears, floods become more frequent and more severe. Desertification is self-reinforcing. Once the process has started, conditions are set for continual deterioration.
Invasion of desert onto agricultural land
Local villagers choose to grow vegetation in one such area but then abandon the land leaving it totally bare because it was too far north for sustainable production. If they continue this practice, breaches will be made in the green belt. The desert will advance very quickly into the agricultural zone through the breaches leading to desert encroachment.
The increase of dry land and semi – arid areas would decrease evaporation and therefore reduce rainfall. Water in villages would therefore be scarce increasing the risks for people.
HOW WIDESPREAD IS DESERTIFICATION?
About one third of the world’s land surface is arid or semi-arid. It is predicted that global warming
will increase the area of desert climates by 17% in the next century. The area at risk to desertification is thus large and likely to increase.
Worldwide, desertification is making approximately 12 million hectares useless for cultivation every year. This is equal to 10% of the total area of South Africa or 87% of the area of cultivated lands in our country.
In the early 1980s it was estimated that, worldwide, 61% of the 3257 million hectares of all productive dry lands (lands where stock are grazed and crops grown, without irrigation) were moderately to very severely desertified. The problem is clearly enormous.
HOW CAN DESERTIFICATION BE HALTED?
To halt desertification various points should be considered. As humans we need to respond smartly yet efficiently to these problems.
- Farmers play a big role in human response as the main problem occurs at farms. They should change farming methods to suit the land and soil as well as reduce the number of animals on the land, allowing plants to regrow.
- Soil conditions must be made favourable for plant growth by, for example, mulching. Mulch (a layer of straw, leaves or sawdust covering the soil) reduces evaporation, suppresses weed growth, enriches soil as it rots, and prevents runoff and hence erosion. Reseeding may be necessary in badly degraded areas. Mulching and reseeding are unfortunately expensive practices. The more developed countries should offer assistance to southern Africa in obtaining these expensive practices.
- Increase processes that remove greenhouse gases from the atmosphere.
WHAT YOU CAN DO?
Desertification often occurs over many generations, on a very large scale and so it is difficult for individuals to take action. Some ideas for combatting this problem include:
- Take part in the activities of conservation groups.
- Bring overgrazing and land mismanagement to the attention of Department of Agriculture.
- Set up schemes to save water in your community
Desertification definitely has a big impact on southern Africa mainly due to Africa’s geography, therefore the people of Africa need to make special precautions to avoid desertification from spreading. If the problem is more recognized, and dealt with, improvements can be made. As a globe, we should look to tackle the main cause, global warming more efficiently, to reduce the increasing of desertification and preserve our vegetation.
by Sashlin Reddy, Westville Boys’ High School, South Africa