Uzbekistan

Rehabilitation of lands degraded by human
activities:
Stabilizing the dry soil of
the Aral Sea basin

uzbekistan
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Region Central Asia
Capital Tashkent
Surface area 447,400 km2
Population 26,980,000 inhab.
Population density 60 inhab./km2
Infant mortality rate (per thousand births) 58
Fertility rate (births per woman) 2.7
Population growth rate (per annum) 1.5%
Life expectancy (female-male) 70 – 63 years
Average temperatures (min./max.) 8.3 / 21 ºC
Forest area 5 %

Introduction

The ambitious irrigation projects undertaken in Central Asia at the time of the Soviet Empire are the principal causes of the catastrophic desiccation of the Aral Sea. Excessive pumping of water from the Amu-Dar’ya and Syr-Dar’ya rivers to farmlands has led to the total imbalance of the Aral Sea ecosystem and water resources of the entire region. The drying up of the Aral Sea is often cited as the greatest environmental disaster caused by mankind.

The breaking up of the Aral Sea into smaller water bodies has begun and is likely to continue. The expression ‘Aral Sea syndrome’ suggests the complex desertification process taking place in the region. In an attempt to rehabilitate the desiccated Aral Sea bed, scientists have planted salt resistant plant species introduced to stabilize and enrich the soil.

The Aral Sea

The Aral Sea, once covering an area of 68,000 km2 , has for a long time been one of the biggest salt lakes in the world, principally drawing its source from two rivers, the Amur-Dar’ya and the Syr-Dar’ya. The Aral Sea began drying up in the 1960s as water was pumped to irrigate cotton fields and other thirsty crops. Over the last few decades the Aral Sea has shrunk to half its original size. Up until the mid 1980s, the sea used to receive 50 km3 to 60 km3 of water per year from its two main feeder rivers, the present flow stands at 2 km3 to 5 km3 per year. With the shrinking of the Aral Sea, traditional fishing communities have long since lost their source of revenue as salt levels have increased resulting in the disappearance of a large number of fish species (picture 1.).

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1. Stranded ships in the bay of Birlestik.
© Yann Arthus-Bertrand / Earth from Above / UNESCO

By studying the available literature, it is clear that the catastrophic environmental consequences were already foreseen during the planning stages of the major irrigation project. It was believed that the economic advantages of the undertaking counterbalanced the negative ecological effects.

Indeed, the economic benefits in the region were substantial during the first ten to fifteen years of the project. However, in the long term, the harmful consequences of the natural imbalance has made itself felt at every level while the economic objectives were never reached. Due to the difference between the planning and realization of the project, the socio-economic situation around the Aral Sea worsened. The region of the two river deltas has been seriously affected by the drying up of the lake. The drop in the volume of water has resulted in an increase in the concentration of pesticides, minerals, fertilizers and herbicides in the soil, all used in large quantities in cotton monoculture. These factors have all contributed in disturbing the quality of life of the local people, especially in the regions of Amur-Dar’ya and Syr-Dar’ya. Deprived of its water reserves and potable water supplies and unable to pursue traditional agriculture or fishing, the local populations have lost their livelihood.

In 1988, the USSR declared the zone around the Aral Sea a ‘natural disaster area’ and for the first time, the USSR turned to the international community for help. Following the break-up of the Soviet Union, the five newly independent states of the Aral Sea basin, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan have been seeking to mobilize regional and international support for measures to rehabilitate the degraded land and water resources in the basin. Among the scientific initiatives has been an eight-year ecological monitoring and research project in the river delta areas of the Aral.
The project is supported by the German Ministry of Education, Science, Research and Technology (BMBF) and is co-ordinated by Hamburg University and UNESCO.

badCauses and effects of Aral Sea desiccation

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2. The desiccation the Aral Sea over the years.
© Siegmar W. Breckle and Walter Wucher, Bielefeld University, Germany

The lowering of the Aral Sea water table is still continuing and is the cause of two major environmental problems:

In 1939, the island of Barsa-Kelmes was designated a nature reserve, one of the more precious Central Asian deserts. The flora of the island comprises some 257 species, in particular Artemesia and Anabasis. Some antelope species (Gazella subgutturosa and Saiga tatarica) as well as the onager (Equus hemionus) were introduced on the island several years ago. Certain species have recently been added to the Red Fauna List of threatened species (a list of the world's most threatened fauna and flora species). The isolated nature of this reserve has secured its absolute protection and only as recently as 1999 has the island become accessible from the mainland. If special efforts are not made to preserve the unique character of this ancient island, it will rapidly lose its status as one of the most important nature reserves in Central Asia.
The emergent strip of land has been named the Aralkum desert. The surface area of the desiccated seabed is about 40,300 km2. Unintentionally, the massive scale of human experimentation has thrust the local population into an uncertain future.

goodPossible solutions

The problems of the Arulkum desert had not been dealt with since the middle of the 1980s. In 1992 this prompted a new inter-disciplinary research programme with special emphasis on the delta areas. The UNESCO-BMBF project was begun, financed by BMBF and co-ordinated by Bielefeld University (Germany). The international project focuses on plant succession on the dry Aral Sea bed and the prospect of improving soil fertility for agriculture (picture 3.). The project has two main objectives:

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3. Plantations to rehabilitate the soil in the Aral Sea region.
© Walter Wucher, Bielefeld University, Germany

The desiccated Aral Sea bed forms a virgin land surface on which plants (including seeds) and animals have never before existed, though it is actively populated by various micro-organisms. The Aralkum desert seabed thus represents the largest terrestrial area where primary succession is currently taking place: it is possible to observe how different vegetation cover successively colonizes the bare sandy salt bed.

Knowledge acquired through observation of the vegetation is very important for the understanding of ecosystem dynamics in the whole Central Asian area.

Since the 1980s only salt deserts have formed on the dry seabed. Today, the open dry seabed area is a huge salt flat and a source of salt dust in the vicinity. The direct influence of aerosols, such as salt particles and dust, on the natural ecosystem and the health of the local people remain controversial.

Saline soils and salt specific vegetation, made up of halophytes, are characteristic of these deserts and steppes and are most typical in the Caspian region, the Aral Sea and the Balkhash basin in Central Asia. Over a period of 40 years, the Aral Sea basin has been transformed into an immense salt desert that is gradually expanding. Comparable to the Great Iranian Salt desert and even greater than the Great Salt desert of Utah in the United States, the coastal plain and the dry seabed of the Aral Sea are perfect models for studying salt desertification.

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4. Vegetation cover of 30% to 40% helps to stabilize the
dry seabed on the eastern coast of the Aral Sea.
© Walter Wucherer

bladPhytomelioration: improving the quality of the saline soils by plants

The phytomelioration technique consists of improving soil properties by planting species resistant to harsh desert conditions that prompt plant succession. It is essential to understand the mechanisms of the different types of salt-tolerant species in order to improve the vegetation composition on these saline soils. The salinity of the dry seabed varies enormously from one place to another, resulting in a considerable variety of saline soil types.

Among the 266 known species in the region, 200 (75.2%) species appear on the saline soils of the seabed. The remaining species may be influenced by salt after germination or during the other stages of their development. The result is rich halophyte flora that is, on the one hand, affected by the various degrees of salinity, and on the other hand, has developed adaptation strategies to resist salt conditions.
Thus, the following species lend themselves particularly well to phytomelioration: Halocnemun strobilaceum, Halostachys caspica, Halidium caspicum, Haloxylon aphyllum, Tamarix and Climacoptera species.

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5. Landscape of the desiccated banks of the Aral Sea.
© Yann Arthus-Bertrand Earth from Above / UNESCO

Conclusion

Soil improvement by vegetation cover is a realistic way to stabilize the dry seabed surface. This process will reinforce the natural colonization of the area by plant propagation and the creation of seed banks (a reserve for growing plants in the future) for natural dissemination.
The following conclusions can be drawn from experiments carried out in the region of Kaskakulan Island:

  • The rate of aridity during the first vegetative period plays a major role in the survival rate of seedlings and saplings.
  • Species of local flora are more effective in improving the soil.
  • Sandy soils of the 1960s and 1970s are more favourable for soil improvement by plants than the clay soils of the 1980s and 1990s.

This case study was proposed by Mr Walter Wucherer.
For more information, please contact him at the following address:

Mr Walter Wucherer
Universität Bielefeld
Biologische Fakultät
Lehrstuhl für Ökologie
PO Box 100131
33501 Bielefeld
Germany

Tel. (+49) 521 106 55 37
Fax (+49) 521 106 29 63
E-mail: walter.wucherer@biologie.uni-bielefeld.de

activities

pencil

The teacher tells the story of the Aral Sea to the class.

pencil

Where is Central Asia?
Locate the Aral Sea basin on
the world map. Can you find Uzbekistan and Kazakhstan?
How is desertification occurring in the Aral Sea basin?
Do you know of similar phenomena of desertification induced by human activities?
Is there a similar problem like
the Aral Sea in your region?

smile

How do scientists attempt to rehabilitate the Aral Sea?
What role do plants play?
Will the Aral Sea ever become
like its former past?
How do you envisage the future of the Aral Sea basin?
Imagine the life of the inhabitants of the region.

smile

Imagine that you are a fisherman from Kazakhstan or Uzbekistan. How would you react faced with the desiccation of the Aral Sea? What would you say about
a scientific project to grow plants on the bare soil?
How do you imagine your future?

smile

Part of the class could draw the Aral Sea as it was before the irrigation project while another group could draw the desiccated Aral Sea after the project: the boats that have run aground, the dead fish, the angry fishermen.
The others could draw the dry seabed after the plantation
of vegetation cover.
Which new activities could
be adopted by the local population?


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