Soil degradation

from Wikipedia, the free encyclopedia

As soil degradation refers to the deterioration of ecosystem services of the soil up to their complete loss. It can be a natural process, for example triggered by climate change , or by humans , for example, through cultivation of the soil without compensation for the extraction of substances.

Soil degradation caused by anthropogenic causes is meanwhile deteriorating areas on the scale of Switzerland every year . Without a functioning soil and the microfauna it encapsulates , ecosystem functions and the services resulting from them, such as the decomposition of dead organic material, recycling of nutrients and the cultivation of crops, would no longer be guaranteed.

Problem

The degradation of soils is a global problem and not a phenomenon of the modern age (see Critias by Plato ), even if it has assumed ever greater proportions in recent decades. As early as 1997, 15% of the ice-free land surface showed anthropogenic degradation phenomena (an area larger than the USA and Mexico combined), of which one percent was already so destroyed that the soil can no longer be reclaimed. The area of ​​soils with signs of degradation continues to increase; in 2008 this area was already 24%. Today we lose approximately 24 billion tons of surface soil annually. The size of the degraded area is roughly equivalent to that of Switzerland. The continents are affected to different degrees by the problem of soil degradation. The most intensive phenomena of soil degradation can be found in Asia, where 39% of the soils are already degraded. Dry areas, which make up 40% of our land area, are particularly affected, with soil degradation already being seen in 70% of the area. Soil degradation is particularly problematic because it is a creeping process that is only perceived at a late stage. For example, a farmer can lose about 0.1 cm of soil on a very rainy night, which is 1.2 tons of soil lost on 1000 m². After 20 years, over 2 cm of soil has been irretrievably lost. It would take nearly 500 years to recreate this soil. In relation to a human life, the soil can thus be described as a non-renewable resource .

Causes of Soil Degradation

  • Destruction of the vegetation cover: mostly through deforestation, slash and burn or overgrazing .
  • Mismanagement: Cultivation of monocultures , insufficient supply of organic fertilizers or green manure or liquid manure , excessive farming on slopes, intensive irrigation with poor quality water, insufficient drainage of arable land leads to salinization .
  • Intensive use of inorganic fertilizers, pollution with industrial and urban waste, air pollution, contaminated sites .
  • Destruction of the soil structure: compaction by machines, large populations of livestock or people (footpaths), soil removal.

Types and consequences of soil degradation

In principle, one can differentiate between biological, chemical and physical soil degradation.

Biological soil degradation

Chemical soil degradation

  • Depletion of the carbon pool in the soil: Increases the CO 2 content of the air
  • Changes in pH value : lead to soil sterility
  • Soil salinization : prevents the plants from absorbing water
  • Poisoning: Contamination of the soil with inorganic and organic pollutants kills organisms and can lead to contamination of the groundwater

Physical soil degradation

  • Soil compaction : Destroys the pores of the soil and thus the habitat of soil organisms and plants, soil respiration is reduced and water is no longer absorbed
  • Soil sealing : can promote flooding as the water can no longer penetrate the soil
  • Soil loss: The use of the soil for farmers is no longer possible

Projects to combat land degradation

The People's Republic of China , with the Green Wall of China , and the African Union , with the Green Wall in the Sahel , have separately launched two similar projects to combat ongoing soil degradation.

Known countermeasures

Against chemical degradation becomes increasingly phytoremediation as bioremediation technique used to filter the contaminants from the soil.

Lime is used extensively against soil acidification in order to raise the pH value again.

Economic and social consequences

The destruction of the soil leads to an increasing threat to the food base worldwide. Because today already 20% of the areas used for agriculture by humans show signs of degradation. One third of the world's agricultural area with around 3.2 billion dependent people was affected by significant soil degradation in 2016. This is particularly threatening as only a small part (11%) of the land area can be used for agriculture without restrictions. Most of it is too dry (23%), 10% is chemically unbalanced, 6% is too humid, 6% is permafrost . For the rest of the country, the soil is not deep enough for agricultural use. 1.5 billion people are directly affected by soil degradation. Food production is expected to fall between 15 and 35% over the next 25 years. Especially in the poorer regions, crop failures due to degraded soils cannot be buffered by improved crops. This can lead to mass migrations in the corresponding areas. Over the next 10 to 20 years, global environmental changes, including desertification and soil degradation, are expected to cause economic damage of $ 5 trillion. In addition to the loss of soil as a source of food, soil degradation disrupts biogeochemical material cycles, for example the water cycle . The loss of soil also reduces its function as a store for greenhouse gases and thus intensifies climate change .

Soil degradation in Europe

Even if Europe is below the global average with only eleven percent degraded area, there are strong effects in individual regions. In Europe, soil compaction is a particular problem due to the population density. The Ukraine , with approx. 40% compacted soil, serves as an example . In Germany more than 30,000 km² of soil has already been degraded, which is more than nine percent of the total area. The Mediterranean region in Europe is much more severely affected, 157 million hectares there are at risk from soil erosion and another four million from soil salinization . It is precisely in these places that tourism also has a negative impact on the soil. The different European soils are the result of geography , topography , climate and the distribution of loads. The climate makes Mediterranean regions particularly sensitive to soil degradation (especially erosion). The deforestation of the forests in these areas and the increase in forest fires have severely degraded the soil since Roman times. Today there are areas in which there is simply no more soil that could degrade further. The same applies to regions in Eastern Europe. In the western states, the problem of soil sealing is particularly dramatic. In densely populated countries such as Belgium and Denmark , between 16 and 20% of the area (industrial plants, roads, etc.) is sealed. The pollution of the soil by toxins is problematic throughout Europe, as these substances are increasingly finding their way into the groundwater . In Poland , for example, 35% of the land area is already showing signs of acidification through pollution .

See also

Web links

Individual evidence

  1. ^ A b c d G. WJ van Lynden: Soil Degradation in Central and Eastern Europe . ISRIC. 2000.
  2. ↑ a b L. R. Oldeman: Global Assessment of Soil Degradation. 1988.
  3. ↑ a b Scientific Advisory Council of the Federal Government on Global Change: World in Transition. 2000.
  4. ↑ Scientific Advisory Council of the Federal Government on Global Change: The Endangerment of Soils. 2000.
  5. ↑ a b c Bai ZG, Dent DL, Olsson L and Schaepman ME: Global Assessment of Land Degradation and Improvement. 1 Identification by remote sensing. Report 2008/01 (GLADA Report 5) . ISRIC - World Soil Information, Wageningen. 2008.
  6. ^ Soil Degradation Study: There Goes the Farm. In: New York Times. March 31, 1992.
  7. ↑ a b c d R. Lal, TM Sobecki, Thomas Iivari, John M. Kimble: Soil Degradation in the United States: Extent, Severity, and Trends. Published by CRC Press, 2004.
  8. ↑ A third of the world's arable land is at risk . In: Welt , February 13, 2016. “Fertile soils are the basis of life for humanity. However, scientists observe that the quality of soils is deteriorating worldwide. "  
  9. ↑ Ephraim Nkonya, Alisher Mirzabaev, Joachim von Braun: The worldwide degradation of land and soils . ZEF of the University of Bonn and the International Food Policy Research Institute (IFPRI) Washington DC 2016.
  10. ↑ LR Oldeman: Impact of Soil Degradation: A Global Scenario. 2000.
  11. ↑ D. Pimentel, N. Kounang: Ecology of Soil Erosion in Ecosystems . In: Ecosystems . 1998. doi : 10.1007 / s100219900035 . "Each year, about 75 billion tons of soil are eroded from the world's terrestrial ecosystems"
  12. ^ Review of the Economics of Climate Change. In: Stern. 2006.
  13. ↑ Environment in Europe: Soil degradation. European Environment Agency, 1998.
  14. ↑ Europe's environment: the third assessment. European Environment Agency , May 12, 2003, accessed March 31, 2019 .