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10.4 Sustainable management of arid and semi-arid environments
Causes of soil degradation
l Water erosion accounts for about 60% of soil degradation. There are many types of erosion including surface, gully, rill and tunnel. l Acidification is the change in the chemical composition of the soil, which may trigger the circulation of toxic metals. l Eutrophication (nutrient enrichment) can degrade the quality of ground water. l Groundwater over-abstraction can lead to dry soils. l Salt-affected soils are typically found in marine-derived sediments, coastal locations and hot arid areas where capillary action brings salts to the upper part of the soil. l Atmospheric deposition of heavy metals and persistent organic pollutants can make soils less suitable for sustaining the original land cover and land use. l Climate change will probably intensify the problem. It is likely to affect hydrology and hence land use.
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Human activities
Human activities have often led to degradation of the world’s land resources. Damage has occurred on 15% of the world’s total land area. While severely degraded soil is found in most regions of the world, the negative economic impact of soil degradation is most severe in those countries most dependent on agriculture for their incomes.
Table 10.1 Human activities and their impact on soil erosion
Action
Removal of woodland or ploughing of established pasture Cultivation
Grazing
Roads or tracks Mining
Effect
The vegetation cover is removed, roots binding the soil die and the soil is exposed to wind and water. Slopes are particularly susceptible to erosion. Exposure of bare soil surface before planting and after harvesting. Cultivation on slopes can generate large amounts of runoff and create rills and gullies. Overgrazing can severely reduce the vegetation cover and leave the surface vulnerable to erosion. Grouping of animals can lead to trampling and creation of bare patches. Dry regions are particularly susceptible to wind erosion. Reduced infiltration can cause rills and gullies to form. Exposure of bare soil leads to rapid erosion.
Sustainable development is a process by which human potential (quality of life) is improved and the environment (resource base) is used and managed sustainably to supply humanity on a long-term basis.
Sustainable development meets the needs of the present generation without compromising the ability of future generations to meet their own needs.
Essential oils in the Eastern Cape, South Africa
Global pattern
About 65% of the world production of essential oils occurs in developing countries such as India, China, Brazil, Indonesia, Mexico, Egypt and Morocco. However, the USA is also a major producer of essential oils such as peppermint and other mints.
Revised
Globally, the essential oils industry – valued at around $10 billion – is enjoying huge expansion. Opportunities include increasing production of existing products, and extending the range of crops grown.
Essential oils in South Africa
The South African essential oils industry has only recently emerged. Currently it exports mainly to developed economies such as Europe (49%), USA (24%) and Japan (4.5%). The most significant essential oils produced by South Africa are eucalyptus, citrus, geranium and buchu. Others include rosemary and lavender. Currently, the South African essential oils industry comprises about 100 small commercial producers of which fewer than 20% are regular producers. Expansion of the industry in the area involves much-needed agricultural and agriprocessing diversification.
Factors that make South Africa an attractive essential oils market include: l much of the demand being in the northern hemisphere, with seasonal effects making southern hemisphere suppliers globally attractive l having traditionally strong trade links with Europe as a major importer of fragrance materials l South Africa being established as a world-class agricultural producer of a wide range of products
The Eastern Cape
The Eastern Cape is set to become one of the main contributors to South Africa’s burgeoning essential oils industry, with 10 government-sponsored trial sites currently in development throughout the province. Six of these form part of the Essential Oil Project of Hogsback, where approximately eight hectares of communal land is being used. A project at Keiskammahoek has been operational since 2006. These trials form part of a strategy to develop a number of essential oil clusters in the Eastern Cape.
The production of essential oils holds considerable potential as a form of sustainable agricultural development in the Eastern Cape. Not only are the raw materials present but it is a labour-intensive industry and would utilise a large supply of unemployed and underemployed people.
The essential oils industry has a number of advantages: l It is a new or additional source of income for many people. l It is labour intensive and local in nature. l Many plants are already known and used by the peoples as medicines, and are therefore culturally acceptable. l In their natural state the plants are not very palatable nor of great value and will not therefore be stolen. l Many species are looked upon as weeds – removing these regularly improves grazing potential as well as supplying raw materials for the essential oils industry.
Crops
Wild als (Artemisia afra) is an indigenous mountainous shrub, used for the treatment of colds. Its oil has a strong medicinal fragrance and is used in deodorants and soaps. Double cropping – in summer when the plant is still growing and in autumn at the end of the growing season – yields the best results. Demand for Artemisia has not outstripped the supply of wild material. However, it is increasingly being cultivated as a second crop. It requires minimal input in terms of planting, tillage, pest control etc. and it is relatively easy to establish and manage. Moreover, it can stabilise many of the maize fields and slopes where soil erosion is a problem.
Expert tip
You are expected to know a case study of sustainable management in arid and semi-arid areas. You will need to learn some supporting details about your case study.
The local population is very enthusiastic about the crop, especially given the right economic incentives. Khakibush (Tagetes minuta) is an aromatic. In the Eastern Cape it is the most common weed in most maize fields. Oil of tagetes is an established essential oil, although its market is limited. Local people are again quite enthusiastic about collecting khakibush if the incentives are there. Harvesting takes up to 3 months and provides a great deal of extra employment, as well as eradicating a weed. At present the use of wild Tagetes and those in the maize fields is sufficient to meet demand. An increase in demand might lead to the establishment of Tagetes as secondary crop in maize fields. Other species such as geranium, peppermint and sage require too much land, labour and water to be very successful.
Exam-style questions
1 (a) Describe the distribution of the world’s arid areas. (b) Evaluate the role of wind in hot desert environments. 2 (a) Explain the causes of aridity. (b) Outline the potential for sustainable development in dry areas.
Typical mistake
Sustainable development is an ongoing process. It is possible to evaluate its success so far – or its potential for success – but we cannot know how conditions will change for future generations.
Now test yourself
15 To what extent could the essential oils industry be considered a form of sustainable development in the
Eastern Cape.
Answer on p.220
Tested
[10] [15] [10] [15]
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