Desertification

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Dried up Aral Sea

Desertification , also desertation , German ( progressive ) desertification or devastation , also Sahel syndrome , describes the deterioration of the soil in relatively dry ( arid , semi-arid and dry sub- humid ) areas, brought about by various factors such as climate change and human ( anthropogenic ) activities becomes. This soil degradation causes deserts or desert-like conditions to develop or spread. The mostly upstream stage of steppe formation is known as desertification .

Some authors specifically distinguish between desertification for natural desertification (including natural climate change) and desertification for man-made processes. The latter term is derived from the Latin desertus (= desert) and facere (= to make). The prerequisite for this is human interference in the respective ecosystem .

As a result, the earth is currently losing around 12 million more hectares of fertile soil every year (this roughly corresponds to the arable land in Germany), and the trend is increasing.

causes

Global vulnerability map of the areas most severely affected by desertification.
Erosion, here in Lesotho , causes desertification in many places

Desertification can progress through deflation (gusts of wind), denudation (water), salinization, and skeletonization. The main causes of desertification are based on human actions, so desertification is anthropogenic . In addition, natural fluctuations in the amount of precipitation also play a role, as periods of drought can trigger or intensify a desertification process.

As a result of the drought - and the associated famine in the African Sahel zone - the problem of desertification became increasingly important in the early 1970s. In the "United Nations Convention to Combat Desertification ( UNCCD )" held for the first time in 1977 in Nairobi, Kenya , an agreement was reached that human degradation of the biological basis occurs through the following anthropogenic interventions in nature:

Overgrazing and "undergrazing"

The most frequent human intervention in the natural balance of arid areas occurs through overgrazing , i.e. the number of livestock per area is too large under the given climatic conditions. Grazing causes the plant cover to become thinner and thinner and the soil is loosened by the increased cattle tread. The increased keeping of goats is often the result, as these animals are even more undemanding than other farm animals. However, goats damage the sward more severely. The result is increasing erosion .

However, the ability of vegetation to regenerate should not be underestimated. There is good evidence that areas initially classified as irreversibly deserted recovered quickly and by themselves after the reduction in livestock. Therefore, one should speak of (temporary) land degradation here rather than (permanent) desertification .

Furthermore, recent research shows that the existence and moving of large herds could play an essential role in the maintenance (and fertilization ) of the soil and that the abandonment of mobile animal husbandry and the lack of wild animal populations could be a major cause of desertification.

Overuse

In second place there is an unsuitable agricultural use. Shortened fallow periods , faulty irrigation techniques, plowing on sloping surfaces that favor erosion and unsuitable plants are causes of soil changes that lead to less vegetation and thus greater erosion. Chemical substances such as fertilizers or pesticides and mechanical compaction affect the life of the soil, which can lead to the extinction of many animal species living in the soil (e.g. earthworms ). Desertification is much more likely on such areas than on pastureland .

Overuse leads, among other things, to the loss of terraces, to salinization, to the loss of plant cover and nutrients, which results in a vicious circle of overuse and desertification. In addition, there is often an illegal use of groundwater and the use of plastic tarpaulin, which are plowed into the ground after the harvest and thereby further damage the soil.

Deforestation

Finally, deforestation in arid areas is an important cause of desertification. The extraction of arable land and the need for firewood and construction wood have dramatically reduced the tree population in many arid areas of the world, especially in many densely populated regions of Africa where wood is still the most important source of energy today. The lack of protection provided by the treetops and, in particular, by the roots, exposes the soil to erosion. The natural regeneration of tropical dry forests is often not given, so that only targeted planting and maintenance measures (such as in the Sahel zone) can stop desertification.

Complex root causes

Combating desertification is complex. Overexploitation and climate variations can have identical effects and be linked in feedback, making it very difficult to identify the causes of desert advancement and to take appropriate countermeasures. Research into the past ( historical desertification ) plays a special role here, as it enables a better differentiation between natural and anthropogenic factors. More recent research results on historical desertification in Jordan make it appear questionable whether the current measures to protect vegetation and soil can lead to success in the face of advancing climate change , and whether the influence of humans has not been significantly overestimated. Progressive warming could e.g. B. lead to the death of afforested forests .

consequences

According to estimates by the United Nations Millennium Ecosystem Assessment , well over a billion people and around a third of all arable land on earth are affected by soil degradation and thus potentially also by desertification. This applies in particular to large parts of North Africa in the Sahel zone , South Africa , Central and South Asia , Australia , parts of North and South America and southern Europe .

The following 13 countries in the EU are affected by desertification: Bulgaria , Greece , Spain , Croatia , Italy , Cyprus , Latvia , Hungary , Malta , Portugal , Romania , Slovenia and Slovakia .

The consequences of desertification are profound from an ecological and economic point of view and almost all of them are negative. In summary: Agricultural and, in particular, forestry productivity, biodiversity and also the number of individuals are falling markedly, which can have serious consequences, especially in poorer countries due to the great dependence there on natural resources and the mostly low reserves and alternative options. Desertification reduces the availability of elementary ecosystem services and threatens human security . Desertification has also caused the number and intensity of sandstorms to multiply in recent years. It is therefore an important obstacle to development, which is why the United Nations has proclaimed 2006 the International Year of Deserts and Desertification .

Exposed and relocated topsoil can be blown away by the wind or washed away by rain. This can worsen the physical structure and biochemical composition of the soil. Erosion channels and cracks can arise and vital plant nutrients can be carried away by wind or water. When the water table rises due to inadequate drainage and poor irrigation practices, the soil can become boggy or too salty. If the soil is also trampled and compacted by cattle , this can result in plants no longer growing and the precipitation not being able to penetrate the soil, but flowing off the surface. The loss of the vegetation cover is both a consequence and a cause of land degradation . In loose soil, plants can be buried by drift sand or their roots can be exposed. If pasture land is overused by too many animals or by non-adapted animal species, traditional forage crops can disappear due to overeating.

Drying out of the Aral Sea (animation)

Some of the above effects can also affect people outside of the areas directly affected. Deserted land can lead to floods , reduced water quality, increased deposits of sediments in rivers and lakes, and silting up of reservoirs and fairways . The increased number and intensity of sandstorms caused , among other things, leads to damage to machines and to mental and health problems (e.g. infections of the eyes, respiratory diseases and allergies ).

Another aspect is that the production of food is affected. Unless desertification is stopped and reversed, food yields will decline in many affected areas. Malnutrition , hunger and ultimately famine would be the result (especially given the growing world population). However, food production does not only depend on the progress of land degradation . But it can be said with certainty that desertification contributes to the development of famine. Desertification is a huge drain on economic resources. An unpublished study by the World Bank suggests that the decline in natural resources in a country in the Sahel region was equivalent to 20 percent of that country's gross domestic product (GDP). Globally, it is estimated that the revenue that is lost each year in the areas directly affected by desertification is approximately 42 billion US dollars. The indirect economic and social costs for areas not directly affected - such as the influx of " environmental refugees " and losses in food production for the internal market - can be much higher.

Drought and land degradation also contribute to triggering crises (e.g. due to the violation of borders when searching for food), which are then exacerbated by the fact that food is inadequately distributed and the population has no access to it. Due to wars, droughts and land degradation in arid regions , many people in Africa have been displaced within their own country or have been forced to migrate to other countries. The environmental resources in cities and camps in which these people settle, as well as in their surroundings, are exposed to considerable stress (e.g. from clear-cutting of the remaining vegetation). Difficult living conditions and the loss of cultural identity undermine the stability of social structures.

Countermeasures

Reforestation project in Senegal to stop desertification

The Convention to Combat Desertification is implemented through National Action Programs (NAPs). Among the signatories of the convention is expected to deal with their role in supporting these programs and a holistic, integrated and participatory approach to management of natural resources in the ecosystems of the drylands to give. This means that if the states concerned have developed a national action program together with helping states and there are concrete projects, donors can support them directly (e.g. financially). By March 2008, 102 National Action Programs (NAPs) had been drawn up and adopted. They are reference points for ongoing planning processes for poverty reduction and sustainable development in arid areas, a kind of control mechanism for the convention to see whether its efforts are bearing fruit.

Efforts to combat desertification are also to be integrated into other development framework programs (e.g. land degradation and poverty alleviation ). These two goals include improved food supplies, education and training for the people, building capacity at the local level and mobilizing non-governmental organizations. The national action programs try to implement long-term strategies with the participation of the local population. Because only if the population can help shape political processes will they identify with the resulting strategies. The targeted priorities are preventive measures and promoting commitment to sustainable activities by the people who work and depend on the land. The National Action Programs (NAPs) are expected to mobilize significant funding from outside sources. NAPs also describe concrete steps and measures as well as the obligations of governments to create a “favorable environment”.

Overall, an effective counter-strategy against desertification can generally only be implemented through such a package of measures with climatic, forest and agricultural as well as social and political aspects (e.g. Africa's Green Wall in the Sahel or China's Green Wall ). This means that at the local level, for example, reforestation projects together with the creation of forest protection strips can only be permanently implemented if the local population is aware of the problem on the one hand and an alternative to firewood on the other . Issues of local population growth , poverty and urbanization are also crucial, as they can often make such alternatives impossible.

As a local measure against desertification, stone or mud walls are often built to hold up the small amount of precipitation . It is sufficient to set up systems 30 to 40 cm high. At the same time, education measures for the population regarding the maintenance of the dams must usually take place so that damage caused by water, cattle treads and other factors can be repaired annually before the rainy season . Forage crops such as millet can then be planted on the fields that have been created. Another option is to create hedges and rain plantings .

Another strategy against the spread of the desert could be the use of economical stoves or solar cookers . Since they require significantly less or no firewood at all, the amount of firewood taken is also reduced. The lightweight construction of these advanced devices should enable residents to build such a stove themselves. This method strengthens one's own economy and reduces deforestation . Another starting point, in Central Asia, is better thermal insulation of the houses, as less firewood is needed for heating.

A promising approach that is frequently discussed in development cooperation is agroforestry measures. Trees are planted on arable land. On the one hand, they slow down the erosion effect of the wind and, on the other hand, reduce evaporation losses due to the shadow effect; in this way they counteract the drying out of the soil. It is also necessary to solve the economic and political problems of the affected countries in order to achieve an effective and long-term fight against desertification.

See also

literature

Web links

Commons : Desertification  - Collection of images, videos and audio files
Wiktionary: Desertification  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ definition according to UNCCD ; on the website of the UN Environment Program, accessed on December 29, 2007.
  2. ^ Desertion in the Lexicon of Biology. Spectrum of science ; Accessed September 7, 2017.
  3. ↑ a b c The creeping catastrophe. In: Das Parlament , issue 32–33 2010.
  4. ↑ a b Schultz, J. (2008): The Earth's Eco Zones . Stuttgart: Ulmer. ISBN 978-3-8252-1514-9 , pp. 280-281
  5. ↑ a b Fred Scholz: Nomadism is dead. In Geographische Rundschau , Heft 5, 1999, pp. 248-255.
  6. ↑ Jody Butterfiel: Holistic Management Handbook: Healthy Land, Healthy Profits, Second Edition . Island Press, 2006, ISBN 1-55963-885-0 .
  7. ↑ Franziska Dürmeier: Spain: "We are irrevocably losing the best soils". In: www.sueddeutsche.de. June 30, 2019, accessed June 30, 2019 .
  8. ↑ European Court of Auditors : Combating desertification in the EU: The steps taken so far lack coherence, criticize the EU auditors. In: eca.europa.eu . December 18, 2018, accessed December 19, 2018 .
  9. ↑ a b c See: Factsheet 3 of the United Nations Convention to Combat Desertification, published by the UNCCD Secretariat in 2008 PDF file ( Memento of the original from January 24, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.unccd.int
  10. ↑ Cf.: Factsheet 4 of the United Nations Convention to Combat Desertification, published in 2008, read March 24, 2011, from: PDF file ( Memento of the original of January 24, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.unccd.int
  11. ↑ Hans-Heinrich Bass, Klaus von Freyhold and Cordula Weisskoeppel: Harvesting water, protecting trees: Food security in the Sahel [1] verweis = , Bremen 2013, pp. 35–41. (PDF file; 2.79 MB).