Sustainable Land Use in Deserts

Deserts are arid areas on the globe where plant growth is scarce. The lack of water during longer periods is due to climatic conditions. This is known from all parts of the climatic temperature zones of the globe. Deserts and their adjacent semidesertic regions, such as the Sahara, the Negev and Sinai, the Namib, the Atacama and Altiplano, Central Australia, the Mohave in Southwestern USA, the Kyzylkum and Aralkum, and the Kawir in Iran and the Afghan deserts often exhibit severe changes in their environmental design according to human impact. Fluvial and aeolian soil erosion, enhanced salinity by waterlogging, pollution by pesticides and other toxics, thus, the loss of productive areas, are some of the severe effects of inadequate use by man Desertification often takes place by this human influence in ecotopic areas where a shift to desertic conditions by a slight change in environmental factors may cause a severe additional degradation.

Landuse in arid regions is mainly applied for agriculture; recreational exploitation is not very often found; technical usage of these regions now has started. Three different methods of agriculture are used: animal husbandry, precipitation-fed agriculture and irrigation agriculture.Irrigation systems are some of the most comprehensive undertakings of mankind, not only involving technical and scientific measures, but alsoinflicting social and cultural changes. Economic alterations for the population and the whole society are likely. Management questions are one of the essential points in success or disaster. A historical look at some examples of irrigation culture gives an idea of the difficulties and hazards with which irrigation societies have to cope. Differences in recently installed systems and their performance are evaluated and judged against their proposed aims. Shortcomings are identified in several fields, i.e. in the technical approach, in planned economic possibilities, in social changes and influence on cultural questions, in water management tasks or in the recognition of environmental hazards.Some recommendations are offered to moderate the negative effects. Financing of the irrigation operating system must be guaranteed. Workers and management must be well-trained and motivated. Rotation patterns of crops must be strictly enforced. The market for the goods produced must repay the input. New technologies have to be evaluated and installed. In the case of financial problems, reduction of areas of cultivation as well as of animal relying on the fodder, is essential. Ingenious ideas of new products, i e making use of local weeds or agricultural use of saline lakes, must not be rejected but strongly supported. A larger diversity of crops will help to reduce fertilizer and pestizide impact as well as the dependence on a certain market.

The term Aral Sea crisis region covers the lower stretches of the rivers Amudarya and Syrdarya, where the effects of the diversion of the river water from the Amudarya and Syrdarya are a blatant case. The drying of the Aral Sea, according to the Scientific Board for Global Environmental Changes of the German Federal Republic (WBGU), was declared the greatest environmental disaster caused by mankind in this century by changing the regional water budget. The disintegration into smaller water bodies is reality. Meanwhile the knowledge and information basis on the status of land degradation and on current activities in the crisis region is still insufficient. Up-to-date information on monitoring of land use and of the situation of the ecosystems in the crisis region is important, since the ecological situation is very dynamic and unstable. Degradation and desertification are threatening the whole population of the area and endangering their basis of living.

In 1999, the dry sea floor of the Aral Sea had an area of about 40 000 km2. The new land is being steadily invaded by plants. The list of the flora consists of 266 species. It is a young immigration flora (40 years old) that established under harsh habitat conditions. Adjacent to the former coastline there are mostly sandy soils which already are free of salt. They are replaced on younger sea floor areas by mixed sandyloamy or loamy coastal and marsh solonchaks. The family Chenopodiaceae was dominant on the solonchaks of the dry sea floor from the 1970s, 1980s and 1990s. The share of the Chenopodiaceae in the flora amounts to 28.2% (75 species). Along the former coastline on the sands of the dry sea floor from the 1960s the Polygonaceae (Calligonum), Fabaceae (Astragalus), psammophilous Chenopodiaceae and some representatives of the Poaceae play a major role. The composition of the flora and of the important families is discussed.

The dry sea floor of the Aral sea is a new terrestrial surface, where plants (including seedbank) and animals have not existed before, and it is actively populated by organisms. The dry sea floor (Aralkum desert) is the largest area worldwide where a primary succession takes place. Unintentionally, mankind has created a huge experiment, an experimental set, a laboratory of nature with thousands of local events. The new knowledge on vegetation dynamics in the Aralkum desert, which is a mosaic of sand and salt desert ecosystems, is very important for the understanding of the ecosystem dynamics in the whole Central Asian area. The succession on the dry sea floor has continued for 40 years. We are able to determine the age of the drying and of the ecosystems. This is important to identify major mechanisms that determine the rate and direction of ecosystem changes on the dry sea floor. The distribution and dynamics of the vegetation and ecosystems were surveyed along some new transects. On the dry sea floor barchan and salt deserts have spread. The present and future development of the drying sea is characterized by the creation of salt desert flats. Along the former coast line the inhabitants of adjacent villages are using the dry sea floor more and more as grazing area and for hay production.

The formation of desert plant associations of the Aral shore has had a long history. This chapter describes the contemporary coastal vegetation. It was determined that main threat of loosing biodiversity in the region lies in extending anthropogenic desertification. Two methods of biodiversity conservation are discussed: (1) restoration of the lost ecosystems and (2) establishment of a network of regional protected areas.

The vegetation dynamics of the Syrdarya Delta has been studied according to its main ecosystem types. The decisive factors in anthropogenic transformation of vegetation are the irrational utilization of water, irrigated agriculture and overgrazing. Aridization of the climate caused by the shrinkage of the Aral Sea speeding up the anthropogenic successions. Vegetation dynamics on all relief positions goes in the direction of halophytization and is chaotic in character. Desertification processes are in progress and expressed in biodiversity loss, convergence of plant communities and simplification of the spatial structure of vegetation cover. Stages of desertification of the meadow vegetation have been shown.

Botanical diversity (BTD) is an important part of biodiversity and a goal for real action for conservation. BTD includes, according to our understanding, plant species, plant communities and their spatial combinations (symphytotaxones). We differentiate between the potential, the registered and the actual BTD.Potential species richness (local flora) of the Amudarya and Syrdarya River Deltas includes 774 species. 295 species are presented in bight deltas, 307 species are only in the Amudarya and 154 species are only in the Syrdarya Delta.Potential and registered plant community richness includes 71 associations and 21 formations. Actual community richness has 2 associations less of Saliceta songooricae formation, because these have disappeared within the two deltas.The ecological positions as a frequency of distribution within the scales of the groundwater table and soluble salts in the soils were studied for the main plant community.An ecological interpretation of the scheme of landscape desertification within the Amudarya Delta indicated the area where different conditions allow tugai communities to survive and possible water management to support existing tugai communities and renew wetland conditions.

Terrestrial ecosystems are extremely vulnerable in arid regions. They respond even to insignificant changes of the environment, which may result in irreversible modifications of ecosystems and often in the complete loss of their scientific, social, and economical value. Intrazonal hydromorphic landscapes undergo the greatest transformation, the main component of which is floodplain vegetation.

Particle size distribution, salt content and composition, mineralogy and micromorphology of a solonchak salt crust and a takyr crust from the Amudarya River Delta (ADRD) were determined. In the (salt-free) salt crust, 100-μm particles dominate, while silt and fine sand are present in minor quantities only and clay is absent. The soil below the crust has a similar particle size distribution. In the takyr crust, fine particles dominate. In both crusts, quartz dominates, and is accompanied by calcite and mica. Clay minerals (chlorite and kaolinite) appear in minor amounts only. Cl is the major anion among the soluble salts, followed closely by sulfate. The salt crust contains four times more salt than the takyr crust. The salt in the salt crust appears in the form of crystallites of halite and Na, Mg sulfates such as thenardite and epsomite, in addition to gypsum. The size of the interlocking crystallites is 5–10μm. The takyr crust is highly porous, with fine pores on the upper surface, and coarse pores in the bottom part of the crust. It is proposed that particle size distribution of the sediment and groundwater are among the important factors in determining the development pattern of Amudarya River delta soils. A fine particle size composition and absence of groundwater (including drainage water) close to the surface will lead to takyr formation. A relatively coarser particle size distribution and the presence of groundwater close to the surface will lead to solonchak (+salt crust) formation.

The Aral Sea basin has experienced the development of large-scale irrigation since the 1940s–1950s. This policy has resulted in an increased area of secondary salinized lands and other lands unsuitable for cultivation under conditions of a limited supply of irrigating water. The natural environment was seriously damaged, including a lowering of the Aral Sea level and deterioration in the living conditions of the local population. For a long time the population in the area and large segments of the scientific community were misinformed about or unaware of the real ecological state of the region. This, coupled with the Soviet Command and Control system of government, made it difficult, if not impossible, to take the necessary action toward environmental remediation.At present the Aral basin hosts a very complicated system of canals, reservoirs, irrigated fields and hydrotechnical construction including 7.9 million ha of irrigated lands, 323 200 km of irrigation network and 161 800 km of collectors and drains. In spite of such a wide scale of water construction, irrigation techniques themselves are the same as in Middle Ages — border and furrow irrigation. Under such a system of land use, water loss in agriculture is up to one-fifth of the total water intake for irrigation.The total volume of drainage water from the Aral Sea basin is more than 33 km3 a−1. Of this volume, more than 20 km3 a−1 returns to the rivers and about 13 km3 a−1 flows to large depressions or other chaotic areas in desert pastures.Improper irrigation leads to secondary salinization, waterlogging, and, eventually, desertification. Diversion of drainage water to the rivers results in deterioration of river water quality; diversion to the marginal desert areas results in waterlogging of pastures and environmental degradation of the total area.

The geographical situation of Kazakstan in the heart of the Euroasian continent, the aridity of its climate and the significant drainless part of the territory determine the exclusive importance of water resources as the factor providing stability for the environment and stability of social economic development of the Republic.

One of the key issues and problems of the living standard of the inhabitants in the Aral Sea region is that of a safe drinking water supply system. This problem is especially urgent for the population of the remote villages, as people living in these villages have to use water for drinking purposes from shallow wells and boreholes. As the physical conditions of the groundwater are characterized by high salinity, the problem of a safe potable water supply has become very important.

Within a relatively short period, less than a half century, the area of salt deserts in Central Asia has grown by about 60 000 km2. The process of salt desertification is tremendously active in the region of the former Aral Sea. The coastal plain and the dry sea floor of the Aral Sea are an evident model for studying salt desertification. The vast occurrence of salinization processes is the main reason for a very diverse halophytic flora on the dry sea floor. In comparison to other ecophysiological life forms, halophytes thrive on saline soils and are able to grow even on rather strongly salinized substrates. Investigation of the adaptive mechanisms of the various halophyte types is essential for an adequate species composition for phytomelioration of these saline soils. Phytomelioration by artificial planting on the dry sea floor for more rapid closure of the vegetation cover is a great need to minimize the widespread negative effects of salt desertification.

Halophytes are an ancient ecological type the origin of which is connected with the zone littoralis.A Saline environment of their habitat has a positive effect on them, as it reduces competition, prevents diseases and vermin and creates humidity at the expense of accumulation of moisture by salt. The negative qualities of this habitat are the high osmotic pressure of the soil solution and the toxic effect of salt. The morphogenesis and structure of vegetative and generative organs of hyperhalophytes (Halocnemum strobilaceum, Salicornia europaea) and euhalophytes from Suaeda (S. arcuata, S. microsperma, S. prostrata) and from ephemers (Hymenolobus procumbens, Spergularia microspermoides) were studied in the Kyzylkum desert with chloride-sulphate salting of soil, showing the characteristics of plant development caused by the specific habitat. The fruits of halophytes are not sclerified. The pericarp is parenchymatous. The testa have two layers of cells. Their adaptations to extreme desert conditions, including salinization, are implemented at the expense of the submerged position of fruits in fleshy cortex, the presence of tannins and melanins in the testa and fat in the embryo, which makes it difficult for salt to penetrate. The assimilating organs of hyperhalophytes are the shoots with reduced leaves and chlorenchymatic non-Kranz cortex of stems. Euhalophytes have small cylindrical leaves with Kranz (Suaeda arcuata, S. microsperma) and non-Kranz structure (S. prostrata, Hymenolobus, Spergularia ). However, the main line of adaptation of halophytes in both group is the succulent strategy whereby moisture is preserved at the expense of abundant water-bearing cells with thin walls. The structure of stems and roots of the species studied is anomalous, polycambialous and sclerenchymatous, which guarantees protection of lateral meristems and their substitution when they are damaged.

The extent of salinity and pollution of soils and cover vegetation by various contents of salts, organic pollutants, traces of heavy metals is presented for different regions of the South-Central Kyzylkum deserts (Uzbekistan). The Buchara oasis was chosen as the object for biomonitoring and as model site for afforestation and establishment of halophytic pastures for undertaking cattle/goat/sheep farming in arid and sandy deserts of Kyzylkum. The ecological differentiation of phytogenetic halophytic resources, the botanical and economic characteristics of plants and the allocation of edaphic resources to maintenance growth, reproduction and survival were examined for environmental heterogeneity within salt-affected and degraded sandy lands of South-Central Kyzylkum. A computer database of 120 native wide-ranging and narrowly distributed taxa, belonging to 80 genera and 25 families is proposed. Four large ecological halophytic groups in respect to their growth and life strategies in saline habitats were analyzed. For Kyzylkum plant vegetation it was found that C₃ species dropped to low levels in both numbers and biomass, whereas C₄ plants have become the dominant vegetation. This finding throws new light on the C₃/C₄ leaf anatomy of plant diversity of Kyzylkum as a cool temperate desert. More than 25 annual and perennial shrubs/semishrubs, herbs, especially species of genera Salicornia, Halostachys and Halocnemum, Ephedra, Haloxylon, Suaeda and several perennial species of Salsola, Tamarix, Artemisia, Ceratoides, Climacoptera etc. were tested and recommended both for undertaking halophytic agroforesty and biosaline agriculture in arid and sandy Kyzylkum deserts.

Sustainability is the commonly used term for “development which meets the needs of the present without compromising the ability of future generations to meet their own needs” (Pereira 1996). The adoption of such an approach means that the current handling of agricultural development, and especially of its expansion policy, should be continuously checked and evaluated. This would assure that development meets the above stated requirements and will sustain long-term stability.

A seminomadic traditional land use system, based on the ecological properties of a unique environmental constellation at the boundary between winter and summer rainfall climate, might have been instrumental in conserving natural resources in the Northern Richtersveld (Northwestern Namaqualand, Northern Cape Region, RSA). In the arid to semiarid northern part of the Richtersveld, desertification processes are of relatively low intensity, if compared with the southern part of the Richtersveld, in spite of the generally higher level of aridity on the Northern Richtersveld. This observation is of wider interest because the two regions of the Richtersveld have experienced a different history of land-tenure and land use practices, which might, in part, have caused the different level of resource degradation: In the Northern Richtersveld until today traditional seminomadic pastoralism in a communal rangeland tenure system has been maintained, although locally replaced by mining areas, permanent settlements and, since 1991, a National Park.In the Southern Richtersveld, the communal rangeland was subdivided by fences into economic units. These have been managed by farmers for a number of years. In spite of the short survival of the economic units concept, the fences still subdivide the landscape.This chapter describes patterns of environmental factors, biodiversity, land use and desertification indicators. Several possible functional interactions between desertification processes and land use are discussed and focal areas for further research are indicated.

When livestock numbers are high in relation to the percentage of the vegetation comprising preferred forage plant species, and where no provision is made for occasional livestock withdrawal during periods of flowering and seed set, grazing will deterministically lead to the near-eradication of certain forage plant guilds from rangelands. Recruitment events for long-lived plant species, and even for ephemeral plants, are uncommon in arid (<200 mm/a−1) environments and are closely tied to weather sequences that favour the particular plant species by promoting first seedset and then germination and seedling survival. Preferred forage plant species, whether ephemeral or perennial, with or without soil-stored seed banks, decrease or disappear from areas where the grazing regime, by preventing seed-set, turns potential recruitment events to non-events. This chapter provides evidence for the rarity of recruitment events in an important forage plant Osteospermum sinuatum (DC) T. Norl. (Asteraceae) in South African Karoo shrubland and analyzes population structure and seedling densities in protected (9.4 SD 7.7 seedlings m−2) and grazed areas (0.02 SD 0.3 seedlings m−2) 2 years after a sequence of years that favoured seedling recruitment. Seedling to adult ratios were 5:1 in protected areas and 0.7:1 in grazed areas on the same ranch. Although refuges have potential to increase seed availability in heavily grazed rangelands, seed input to sink populations will be constrained by the dispersal mechanism. Seeds of O. sinuatum are tumbled over the ground by wind, and an exponential decrease in seedling density with distance from the seed source (n= 25, r = −0.699, p <0.001), indicated that most seeds are dispersed within 5 m of the source. When grazing control by fencing is not economically feasible, many small refuges (such as provided by spinescent and toxic plants) may be more effective than seed plantations in maintaining key forage species in rangelands.

This chapter provides examples of the extent to which Jordanian farmers (Fellaheen) and Bedouin have contributed to vegetation degradation in northeastern Jordan. Irrigated cultivation of marginal lands, deep ploughing of the fragile rangeland, overgrazing, cutting and uprooting of perennial xerophyte species for fire, and even deliberate burning, have in some areas led to a process of desertification.It is known that the rangeland in northeastern Jordan used to support large numbers of highly palatable species for grazing including Artemisia sieberi (syn. A. herba-alba), Salsola damascena (syn. S. vermiculata), Atriplex halimus, Achillea fragrantissima, Hamada eigii and Noaea mucronata. These species were dominant, provided a high degree of surface cover, and were widely distributed.At present, these palatable species are no longer found in northeastern Jordan, except in the Surra, Khanasri and Shaumari reserves. The palatable species, however, have been replaced by invader, segetal and thorny plants, such as Peganum harmala, Anabasis syriaca, Salsola jordanicola, Halthamnus hierochunticus, Xanthium spinosum, Onopordum macrocephalum, Chenopodium album and Chenopodium murale, and others.This phenomenon can be considered and used as an indicator of vegetation degradation in northeastern Jordan.

The vegetation of southern Sinai is subjected to great disturbance through unmanaged human activities, including overgrazing, overcutting, uprooting, tourism and quarrying. Many plant species are threatened due to the severe impact of grazing and human activities. The present chapter addresses the main question; how does grazing change the vegetation and its structure in the main wadis in south Sinai? The survey was designed for the vegetation of protectorate and adjacent wadis (overview and identification) and to quantify the grazing intensity in the main wadis. Eighteen main localities within and adjacent to the Saint Catherine Protectorate were studied through choosing 54 stands from whole area. In each stand three transects (500 m in length) were distributed randomly to estimate grazing intensity (based on grazing index), total cover percent, and current species status. Three hundred and sixteen species were identified, including 19 endemic species, 10 extremely endangered, 53 endangered and 37 vulnerable species. The grazing intensity was significantly and negatively correlated with species richness, number of endangered species (extremely endangered, endangered, vulnerable), number of endemic species and total plant cover. The results showed that 50% of selected localities was overgrazed, 27.8% had high grazing, 16.7% medium grazing and 5.6% low grazing intensity. Mt. Catherine showed the highest percentage of both species richness and number of endemic species while W.El-Kid and W. Nabq have the lowest values of species richness and no endemic species. At the same time, W. El-kid and W. Nabq showed the highest number of endangered species and a huge reduction in the total cover percentage due to overgrazing activities.

In arid regions, the effects of grazing management on natural communities of long-lived plants generally take years or even decades to become evident. Event-driven dynamic behaviour, disturbances, unpredictable and low rainfall and complex interactions between species make it difficult to gather sufficient understanding of vegetation dynamics for developing guidelines for sustainable management of arid rangelands. This is further complicated by the importance of spatial scales and patterns, e.g. patchiness of rainfall, heterogeneous grazing behaviour of domestic livestock or distances between artificial watering points.Simulation models that consider the essential processes determining vegetation dynamics offer scope for quantitatively exploring long-term vegetation dynamics of arid rangelands. If these models are spatially explicit, they additionally allow for the investigation of spatial processes, such as competition or dispersal, and patterns such as landscape features or structures imposed by management (boreholes, paddocks etc.).This chapter, discusses the promises and limitations of spatially explicit simulation models as (often neglected) tools for rangeland management. We focus on model examples from rangelands in southern Africa, namely a set of models simulating cattle grazing in the southern Kalahari and a model simulating a karakul sheep farm at the border of the Namib desert (Namibia).Results of the Kalahari models show the existence of a grazing threshold that determines the long-term sustainability of livestock grazing. This threshold depends on rainfall, grazing intensity and grazing heterogeneity. Its effect is illustrated with the spatial vegetation dynamics around artificial watering points. The model of the karakul sheep farm is used to investigate a successful example of sustainable rangeland management under harsh conditions.

Since the International Convention on Desertification of the United Nations has come into force, the need to measure degradation processes in these areas has further increased. While standard methods for undertaking such measurements are imperfect or expensive, remote sensing with air- or space-borne sensor systems offers considerable potential. It provides a comprehensive spatial coverage, is intrinsically synoptic, collects objective, repetitive data and is thus ideally suited for monitoring environmentally sensitive areas. However, the relatively low spatial resolution provided by remote sensing satellites implies that one needs to exploit the spectral contrast between soil and vegetation and their intermediate states to develop surrogate measurements of degradation. Relationships between climate and environmental conditions, which may be of primary importance at a global scale, become problematic when local factors such as topography, lithology and soil properties determine the redistribution of water available for plant growth. Suitable remote sensing approaches must therefore concentrate on both, vegetation and soil-related assessments of ecosystems.

Water stress is one of the major growth-limiting factors in the Sudano—Sahelian Zone of West Africa. Due to the complex interactions of multiple growth restricting factors, a scientific quantification of water deficits on plant growth is complicated. Deterministic plant growth models (e.g. SWASUC model, CERES—Millet model) are able to describe the interactions between growth-determining factors and the environment. The development of simulation models would therefore be helpful in the classification of potential production zones for the northern part of Burkina Faso. Before plant growth models can be built up and applied, local measurements, calibration and verification are required. Many simulation results from models (see Fechter 1993) indicated that growth restriction factors other than water stress, i.e. low soil fertility or soil properties which affect soil moisture, had a significant influence on yield formation. The exploration of soil properties is of fundamental importance in the African Sahel to detect possible agricultural sites. By the combination of relief, soil types and soil water content sites for potential land use are derived. The derived field data have to be transfered to patterns in aerial photos and spectral signatures of satellite images (mainly Landsat TM and Spot XS) in order to link the field data to remote sensing information. For integrating field data to remote sensing data, robust parameters have to be found, and advanced RS techniques like RGB to USGS Munsell Color transformation or the calculation of specific indices (i.e. redness index or brightness index) have to be used.

The extent of degradation in the vegetation of the Kyzylkum Desert was determined by topography and GIS. Topography is an important variable in many ecological processes. GIS provides a number of methods for analyzing topography. The ability to analyze digital topographic data has significantly advanced ecological modelling (Johnston 1998). Geobotanic investigation, large-scale mapping and GIS make it possible to find conventionally climax associations and their anthopogenic modification in the Central Part of the Kyzylkum Desert. Zonal types were formed on the Old Xerophilous and Old Mediterrenean bases in the Paleogene and Neogene. The main types are Turanian semishrub desert type, Turanian psammophyton type, Irano—Turanian psammosavanna type and halophyton turanicum type on the different type of soils. Before the 20th century, climax associations of the first and second types were predominant in the plant cover. At present, associations of the third type predominate on sandy desert soils. Natural renewal of the fodder plants in intensively used pastures practically does not occur and weeds and unpalatable species predominate. Ninety percent of the degraded vegetation was determined by spatial analysis. Average dry mass of the pasture plants is about 105 kg ha−1 centner/hectare on grey-brown soils and 55 kg ha−1 on sandy desert soils.

The modern processes of desertification of the Caspian Sea territory have resulted in a complex influence on both external (climate, sea transgression, human activity) and internal factors (modern tectonic movement, rock structure and the level of their stability towards destruction and transportation, geomorphological and hydrogeological conditions, the structure of regional biocomponents), most effective of which is economic human activity. Irrational mastering of the semi-desert and desert regions of the Kazakhstanian zone of the Caspian Sea, along with the global and regional climatic changes, have led to significant and sometimes irreversible degradation of the many environmental components.The modern transgression of the Caspian Sea essentially affected the intensity of the desertification process, and also aggravated the ecological and social economical problems of the region.The data are made into a map of the modern natural-anthropogenic processes of the Kazakhstanian coasts of the Caspian Sea at a scale 1:500 000.Analysis of the area development and degree of intensity of modern natural-anthropogenic processes permits a regional classification on the degree of destabilization in ecosystems under coastal management in view of modern transgression by the sea.

Some aspects of the differentiation of Gobi desert ecosystems caused by climate (sectoral position of the territory on Eurasian continent, latitudinal-longitudinal changes) are reviewed. Diversity of dominant species of plant communities is noted in different regions. Ratios between areas of the different soil-lithological groups of ecosystems are presented. Main factors of anthropogenic transformation of ecosystems have been revealed and main criteria for the assessment of modern conditions of the main ecosystem components (soils and vegetation) have been developed. Ratios between ecosystems subject to different degrees of anthropogenic transformation have been calculated on the basis of ecosystem maps at a 5° scale of transformation. It is shown that anthropogenic transformation of semideserts is greater than that of deserts. Recommendations have been proposed for conservation of the ecosystems of the Gobi desert.

This chapter notes that the main leading factors disturbing the vegetation cover of Kazakhstan’s sand deserts cause different degrees of anthropogenic transformation. Methods for mapping anthropogenic successions and forecasting vegetation dynamics are discussed. A series of maps has been made to reflect the modern state and extent of anthropogenic transformation of the psammophytic vegetation: maps of modern vegetation, potential vegetation, anthropogenic transformation of vegetation, pastures, intensity of pasture use, desertification, and anthropogenic dynamics of vegetation.

Water-harvesting techniques were, and are, often applied in arid areas. Cultivated fields are irrigated by collecting overland flow from adjoining hillslopes. The purpose of the present chapter is to analyze water-harvesting efficiency in the northern Negev Desert of Israel, where annual rainfall varies from 280 mm in the north to 70 mm in the south. The hypothesis advanced is that runoff water-harvesting efficiency is primarily controlled by surface properties rather than by the absolute amounts of storm and annual rain amounts, the controlling factor for runoff generation being the extent of rocky versus soil-covered surfaces. Rocky surfaces respond quickly to rainfall, due to their low water absorption capacity. At the same time, soil covered surfaces, with a high porosity and high water absorption capacity, represent efficient sinks. As extensive rocky surfaces are more widespread in arid than in semiarid areas, where soil cover is more extensive, it appears that rocky arid areas are more suitable for runoff water-harvesting than climatically wetter semiarid areas. Hydrological data collected at two instrumented watersheds, located one in an arid rocky area, and the second in a semiarid soil-covered area, support the hypothesis. The implications of data obtained for runoff water-harvesting under changing climatic conditions are analyzed. A drier climatic regime can be expected to improve runoff water-harvesting perspectives in a semiarid area, while reducing such perspectives in rocky arid areas. An opposite trend for both areas is assumed during a transition to wetter climatic conditions.

The objective of this study was to understand how landscape structure influences primary productivity in arid shrublands. We propose that analyzing spatial arrangement of shrub patches can help to restore degraded landscapes by indicating limiting factors to landscape productivity.Based on field data from a shrub land in the Northern Negev Desert, Israel, a computer model was developed to simulate the process of surface runoff generation and redistribution by two functional units: shrub patches acting as sinks and a matrix of crusted soil acting as source. Response variables are landscape productivity and water leakage. The model shows two different kinds of ecosystem behaviour: one where water availability limits productivity and one where productivity is not affected by water availability. Spatial arrangement of patches affects landscape productivity only in a water-limited system. We propose that analysis of spatial arrangement of shrub patches in arid shrublands can indicate whether the system is limited by water availability.

Desert shrublands, all over the globe, are characterized by a patchy distribution of plants. Biomass and productivity are limited to small fertile sites. The distance between the patches, and the extent of the fertile patches, are controlled by the specific local edaphic conditions. In a non-saline environment the spatial distribution of the fertile spots is determined by spatial and temporal changes in the water regime, related to spatial differences in water input and water infiltration depth. Under a given climatic regime the differences in the water regime are basically controlled by surface properties. A compacted topsoil surface would limit infiltration depth and enhance runoff generation. Runoff generated at compacted areas is absorbed, on its way downslope, by riparian areas with high infiltration rates, where infiltration at a depth beyond that allowed by the direct rainfall occurs, creating local fertile spots. Patchiness increases tremendously in areas where, as is the case of the Aral region, differences in salinity and subsurface water drainage accompany the spatial non-uniform water regime.

The dry sea floor of the Aral Sea at present is a huge open salt flat. The enhancement of vegetation cover by means of phytomelioration is a realistic way for stabilization of the dry sea floor surface. This will support the natural processes of vegetative and generative propagation and the creation of seed banks for natural dissemination. Two experimental plots were established for identification of perspective plants for phytoreclamation of saline soils. Seeding experiments were started on two kinds of different ecological environments. Seeds of perennial and annual halophytes: Halocnemum strobilaceum, Haloxylon aphyllum, Halostachys caspica, Climacoptera aralensis, etc. were sowed. Experiment has shown that sandy soils have more favourable conditions for implementation of phytomeliorative measures than clay soils; the aridity of the first vegetation period plays a major role on the establishment of seedlings and saplings; species from local flora are more effective for phytoreclamation.

The main purposes of the project are to study the chemical composition of soils in areas of irrigation which were withdrawn from agricultural production because of strong salinization, and to develop a technology for planting salt-tolerant cultures on such lands. The main tasks of this year: (1) to wash out strongly salinized soils in the areas which were withdrawn from agricultural rotation in Kazakhstan, Priaralia, up to the threshold level of salt toxicity in the 1-m-layer of soil; (2) to plant rice, lucerne (alfalfa), melilot and saflor on the lands that were ponded in 1997 with a water norm of 9700 m3 ha−1.An experimental site was established on the left bank of the Syrdarya River, within the Kzyl—Ordinskiy area of irrigation, where the area of lands withdrawn from agricultural rotation exceeds 30 000 ha.

DEREMOTOX is a research and development (R&D) pilot project for the development of “smarter” technological modules especially for and in small ecosystems and for optimizing the also necessary monitoring and risk assessments. Mainly it deals with the low-risk further development of so-called prototype modules or processes. “Smarter” in this context means: resource-efficient, i.e. with higher resource productivity, long-lived, labour-intensive, low-cost mass production of simple (user-friendly), basically needed (technical) modules, adaptable for various local situations. It is proposed to combine/apply at least the following methods in the selected area for recultivation, the Kalmykian steppe: The (new), successfully tested soil-conditioning process proposed in (Belouschek and Kügler 1992) under the acronym SOREC (soil sealing and recultivation), combined with so-called brush walls or Benjes Hedges (BENHEDGE), and complemented with: Solar cooking and solar water steriliziation at the recultivation location and with the extraction of freshwater from atmospheric water vapour in arid regions.Modified and complemented phyto-toxicological investigations (PTI) as done in the context of the EU research project ECCA (see chapter 2). The PTI part is subdivided into three parts: (1) Analysis of local pollution pattern and its effects. (2) Investigation of pollution transport and deposition mechanisms. (3) Concept for a future pollution control and protection from pollution and other external hazards, e.g. through a greenhouse which should be simultaneously tested.

The ecological situation of oases at the southern border of the Taklamakan desert is shortly described, and the importance of a vegetation from indigenous species at the transition from the oases to the desert is emphasized. This vegetation serves as a shelter against sand drift and as a source of livestock feed as well as of fuel and construction material. Its destruction through overexploitation and other interventions during the last decades has considerably promoted sand drift and the deterioration of arable land. Therefore, a management of this protective vegetation is to be developped that leads to a sufficient regeneration and that ensures both its preservation and its use. A research project that is carried through jointly by Chinese and European scientists shall yield an ecological basis for this sustainable management.

The Cele Oasis is located on the southern edge of the Taklamakan Desert with adverse natural conditions and serious hazard from wind-drift sand. Since starting this study work in 1983, very good results have been obtained. This cchapter introduces methods for controlling drifting sand and the results of the project.

Biological soil crusts are important microphytic communities and significantly influence both structure and processes within the ecosystem. They are built up from cyanobacteria, green algae, fungi, mosses and lichens. Various crust types could be found, depending on dune slope aspect and dewfall availability. In the sand dunes of the northern Negev they cover large areas and stabilize the sand surface against wind and water erosion. Free-living and symbiontic cyanobacteria are capable of nitrogen fixation and are important nitrogen sources in the desert sand dunes. As biological crusts enhance the surface stability and soil fertilization, they are to be considered a key factor in the protection of arid and semiarid ecosystems and, thus, in combating desertification in terms of sand dune remobilization.

Limestone quarrying activities have extremely strong environmental impact, since they imply vegetation clearing and loss of soil. A reclamation project was conducted in a limestone quarry of the Serra da Arrábida (southwest Portugal), a natural park with a dense evergreen sclerophyllous shrub community. The successive revegetation of quarry terraces results in distinct plant communities of different age and cover. In this work we examined five different terraces, which were revegetated at 3-year intervals, to evaluate the establishment and growth of introduced species as well as colonization and succession of natural vegetation.New revegetation techniques were also evaluated using three native species (Olea europaea var. silvestris, Pistacia lentiscus and Ceratonia siliqua). Different treatments were applied in a randomized block design to improve the revegetation process: (1) fertilization, to overcome growth limitation due to nutrient deficiencies; (2) mycorrhization, to improve nutrient uptake by plants, as well as their competitive capacity for other resources; (3) addition of a long-term water-holding polymer to reduce water stress. Growth and vigour of the plants was monitored and ecophysiological studies were conducted, comprising water relations and fluorescence measurements. The results of the first year revealed species-specific differences during the adaptation processes: O. europaea was the most robust species. C. siliqua was the most sensitive to the transplantation stress, but after the initial adaptation the highest growth rates were found in this species, where fertilization significantly increased growth rate. Survival rate during the first summer was high in all species, being lowest in C. siliqua and highest in O. europaea (95 and 98%, respectively).

Lake Nasser was created as a result of the construction of the Aswan High Dam, which was completed in 1969. The water of the lake has covered the whole Nubian Nile Valley and penetrated deep into the desert through tributary wadis. This lake is about 500 km long, of which 291.8 km lies in Egypt. Since its formation, the quantity of water in the lake has varied dramatically, determining the dynamics of the lake and its ecotone zone and hence the development programmes of the area and their rationale. The position of the lake, bounded by Arabian rocky desert on the east side and Libyan sandy desert on the west, creates a large habitat diversity that provides an opportunity for integrated development of the area around the lake.The downstream part of Wadi Allaqi, which is the largest of the wadis in the southern part of the eastern desert of Egypt and drains to the lake, was selected as the area for in situ research. In our research we have tested the possibilities for sustainable development of the area by enriching the diversity and productivity of the natural vegetation in the ecotonal zone. The concept of agroforestry could be applied to this type of land management. Economically important indigenous desert plants, Balanites aegyptiaca and Faidherbia albida, were selected for cultivation in ecologically favourable habitats.An experimental farm with 600 trees of Balanites aegyptiaca and 200 trees of Faidherbia albida was set up in the main channel of Wadi Allaqi. The results obtained on the growth rate show that with sufficient water supply the desert plants grow fast and some individuals of Balanites and Faidherbia reached a height above 2 m in less than 2 years. Surface and subsurface irrigation schemes were used. The homogenous growth of trees was observed at subsurface irrigation. The architecture of the roots supports the idea of subsurface irrigation, which facilitates the vertical growth of the roots.This is a long-term experiment which is still in progress. It could be considered complete when plants are self-sustaining and survive without irrigation and protection from grazing.

The progressive desertification in many semiarid regions of the world increases the need for plants that can cope with arid environments and meet peoples’ requirements for food, fodder and fuel. Species of fruit trees in the genus Ziziphus represent examples of such multipurpose plants with great potential for selection and use in drought-prone regions.Ziziphus trees and shrubs inhabit arid environments on every continent due to their versatility in being able to adapt to drought stress. They play an important role in the conservation of soil, with their strong root system which stabilizes the soil and protects it from erosion. The leaves provide fodder for livestock, the hard wood is used for turning, making agricultural implements, fuel and high quality charcoal. In many regions, Ziziphus is grown as a hedge, with its spines creating effective live-fencing, and with its highly nutritious fruits providing a valuable source of energy, vitamins and also income when sold on local markets. In addition, extracts from fruits, seeds, leaves, roots and bark of Ziziphus trees are used in many traditional medicines to alleviate the effects of insomnia, skin diseases, inflammatory conditions and fever. For these reasons, Ziziphus trees have an important role to play in the integrated economy of the arid lands.

Breeding for drought tolerance and improved water-use efficiency is important in order to use the water for irrigation more efficiently. Twelve wheat genotypes were grown under conditions of late drought in Northwest Mexico. Under these conditions, the extent of root exploration for the available soil moisture reserves is often a major determinant of drought tolerance. Distribution of root—length density (RLD) was assessed in the soil profile (0–100 cm soil depth).Most of the RLD was accumulated in the upper soil layers, however, with genotypic differences. Higher RLD across all soil depths was not responsible for improved water-use efficiency. Averaged across soil depth, the largest root fresh weight was observed in a drought-susceptible check. Grain yield was negatively correlated with RLD in the upper soil layer, but was not correlated with RLD in the deeper soil. Drought-susceptible genotypes had most of their roots restricted to the upper soil, while drought-resistant genotypes had high RLD deeper in the soil profile. Genotypes were identified to be used in a breeding program as donor parents to increase RLD for utilizing subsoil moisture and enhancing grain yield in late-drought environments.

TiO₂ — photocatalytic degradation of organic contaminants in water included studies of water samples taken from a heavily polluted well under exposure to natural sunlight; waters from liquid commercial pesticide formulations, simulating treatment of rinse waters of agricultural sprayers; in these studies most compounds were appreciabely degraded within 3.5 h but more complete detoxification required longer exposure. Photocatalytic oxidation of dye chemicals from textile industry resulted in complete degradation of selected azo and thiazine dyes. In the case of dyes the photocatalytic oxidation is accompanied by a reaction of dye sensitization. Enhanced degradation of colourless refractory pollutants has been observed in the combined process. The main advantage of the combined approach is the utilization of visible light for the degradation of refractory organic pollutants, both coloured and colourless, which cannot be photosensitized in the visible region.Different reaction patterns of photooxidation has been witnessed for the herbicides metribuzin (4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4 -triazine-5-one) and bromacil (5-bromo-3-sec-butyl-6-methyluracil). In metribuzin oxygen has a pronounced effect on the rate of photooxidation, while the influence of hydrogen peroxide is quite moderate. The photolytic process in this case would apparently start via a reaction of the excited herbicide molecule with hydrogen peroxide or with oxygen. In the case of bromacil, oxygen does not have a pronounced effect on the rate of photooxidation, which however is considerably enhanced by hydrogen peroxide. The reaction is initiated by hydroxyl radicals generated by hydrogen peroxide photolysis. These conclusions are supported by the different effects of isopropanol inhibition.

The Desert Research Institute implements an active and important part in the international efforts to research and combat desertification. At present, the Consulting Centre had prepared a number of project proposals concerning desertification and a convention of combating desertification.

The situation of desertification in China is described in this chapter. China is one of the seriously affected developing countries with vast areas of desertification, which have very large populations and frequent disasters, and with limited arable lands. The lands affected by desertification are mainly distributed at a range of longitude of 74–119°E and latitude of 19–49°N. The total area of the arid, semiarid and dry subhumid areas is about 3.32 million km2, of which 2.62 million km2, covering 79.0% of the total area, and occupying 27.3% of the total land territory of China, has been desertified, is still developing at present, at an annual rate of 2 460 km2. The authors introduce the general background on China’s desertification, such as the current situation, distribution, types, and causes of desertification, also including its damages. Major measures to combat desertification, including ecological protective project systems and special control measures (especially in sandy desertified regions) are given in this chapter. In addition, a practical study case (in Daxing County, Beijing), is introduced. The development in combating desertification in China is also reported.

Environmental problems of the region and methods to halt the existing disbalance between the environmental situation and economic policy for the sustainable development of the region on the basis of environmental rehabilitation and rational use of natural resources in accordance with the provisions of the Agenda 21 and the Concept of the Environmental Safety of the Republic of Kazakhstan are considered.

The Republic of Kazakhstan is a huge Euroasian country. The country’s area comprises 2.7 million ha, stretching for 2925 km from west to east from the Lower Volga and the Caspian to the Altai and China; 1600 km north to south, from the West Siberian Plain and the Southern Urals to the Tien-Shan ridges and the Kyzylkum Desert. Almost all landscape types of the globe are represented in the country’s vast area, from subtropics and various types of sultry deserts to Alpine tundra and glaciers. The landscape diversity, as well as the great intracontinental seas and lakes, such as the Caspian, the Aral, Balkhash, Zaisan and Alakol determine the rich diversity of Kazakhstan biota. The flora of Kazakhstan numbers over 6000 vascular plant species; its territory is inhabited by 837 vertebrate animals, including 500 birds, 52 reptiles and 150 fishes. The diversity of invertebrates and cryptoganous plants amounts to tens of thousands of species.

This chapter analyzes the relationship between natural population growth, migration and desertification. Starting from results of the standard neoclassical economic theory which concentrates on forces and conditions that lead to an equilibrium after some exogenous disturbance has taken place, it challenges the hypothesis that demographic changes taking place in reaction to increasing discrepancies between carrying capacity and population density in arid regions tend to support the way to an equilibrium between both. The empirical analysis first considers comprehensive and general investigations about people’s reactions to a deteriorating relationship between economic carrying capacity and population density. Based on this, it tests if the rules deduced from theories and general empirics are valid in rural regions affected by desertification. By doing this it will draw on experiences made in different low-income countries, relying largely on case studies from Asia, Africa and Latin America carried out by the author as well as by other researchers. The results demonstrate that predicting adjustment processes by applying conventional theoretical models may be insufficient or even misleading. For economically rational reasons the population may prefer to choose demographic strategies which lead to further deteriorating conditions and to cumulating downward processes characterized by a discrepancy between the short-term interest of the decision unit and the longer-term ecological interest. There is a high probability that they might contribute to a permanently unstable situation, implying a threat to the natural environment and to the people living in it.“In a complementary way, ecologists and other natural scientists, are increasingly recognising that economic activity is “here to stay”; human activities are coming to dominate the global ecosystem and ecosystem analysis which does not explicitly include economic activities makes less and less sense. The stage seems to be set for a coming together of these two disciplines so that problems of resource use… in the global ecosystem can be discussed and assessed in a conceptual framework worthy of these problems.” (Faber, Manstetten and Probst 1996, 24).