**2. Definition to the causes and results of land degradation in arid and semiarid regions: current situation in Turkey**

and poor agricultural management practices are common causes of land degradation, but extreme climatic events also accelerate this process. It is reported that today 1.5 billion people worldwide are affected by land degradation processes [2]. Especially in arid and semiarid ecosystems, land degradation is one of the most significant environmental treats. The major problems encountered in terms of sustainable land management in these ecosystems are mentioned as the salinity, desertification and drought and soil erosion. However, these problems are defined in different forms in different sources. The result is the same for humans who base their life on agricultural bases. This is the gradual decline of the fertility capacity of the soil. At this point, it is extremely important that the soil, which is one of the main resources for living beings to survive on earth, is sustainable. Today, land resources in terms of soil and water are limited to meet the needs of future generations as we completely depend on these resources. In the world, it is estimated that 12 million hectares of land are degraded annually (corresponding to 23 ha per minute), which corresponds to 20 million tons of grain due to the results of drought and desertification. In the economical aspect, annual cost of land degradation is estimated to be about US\$300 billion. This includes losses to both agricultural produc-

To combat land degradation processes, many strategies have been defined by both governments and intergovernmental platforms under several titles such as United Nations Sustainable Development Goals (SDGs), Food and Agriculture Organization of the United Nations (FAO), Global Soil Partnership and Land Degradation Neutral World. In particular, Goal 2 (end hunger), Goal 3 (good health and well-being), Goal 12 (responsible consumption and production) and Goal 15 (life on land) of the Sustainable Development Goals (SDGs) that are planned to be reached for the period covering 2015–2030 include measures and policies related to the use of land and water resources [2]. Of course, the applied agricultural policies have direct and very important effects on land use. The subsidies, incentives and taxes imposed by governments have great implications for which crops are grown and where land is well managed. Inappropriate land management practices applied in marginal areas and fragile ecosystems that are sensitive to climatic, topographic and soil conditions cause the rapid deterioration of land resources. But, land resources are limited and demands for different land-use types especially in the developing countries are greater than the available land resources and these demands become more pressing on natural resources [4]. And so, the only way to protect and sustain soil and water resources from negative effects of erosion, salinity and desertification and other land degradation types in fragile ecosystems is to prepare and enforce appropriate land-use plans. Because of that, sustainable resource management can only be successful if it is based on appropriate land uses. In summary, sustainable promotion of soil and land management is necessary for the provision of healthy food and the environment. Within the scope of this chapter, the aim is to attract attention to land degradation processes in arid and semiarid regions (mostly focused on Turkey's conditions), to analyze the conditions in terms of policy-science interaction by performing situation analysis (SWOT) and develop the effective strategies for sustainable use of land resources under arid and semiarid

tion and other ecosystem services [3].

4 Arid Environments and Sustainability

Turkey conditions.

As mentioned above, land degradation is one of the major environmental problems worldwide and has become particularly severe in the last decades in Turkey [5]. It causes the significant reduction of the ecosystem functionality with unfavorable effects on biodiversity, desertification and water resource quality [6–9]. FAO [10] figured that the main causes of land degradation are the deforestation, population growth, urban expansion, pollution and waste disposal, climate change and unsustainable land management practices, and their results led to discovering significant problems especially in the arid ecosystems having great water scarcity to survive ecosystem services at the optimal conditions. These problems are defined as biodiversity loss, salinization and sodification, nutrient imbalance, compaction, sealing, pollution, acidification, erosion and loss of soil organic carbon. As a result, water scarcity, food and nutrition insecurity, rapid climate change, poverty and social insecurity, migration and reduction of the ecosystem services are basically affecting our lives.

The rate of land degradation processes is closely related to the interactions between climate, soil, land use and topography. Today, Turkey is classified as degraded in terms of soil according to the degradation map [11]. In this context, it was stated that a large part of Turkey is rated highly susceptible to desertification in terms of climate, soils, topography and land cover status [12], although no region could be classified as "desert" in the country based on the general evaluation of the 1965–2007 period using the Aridity Index [13]. Ninety percent of Turkey's total land area is climatologically classified as arid and semiarid regions; especially, Aksaray, Cihanbeyli, Ereğli (Konya), Iğdır, Karaman, Karapınar, Konya, Nallıhan and Niğde stand out in the semiarid-very arid border. In general, Thrace, Central Anatolia, the interior of the Central Black Sea and eastern Anatolia are regions where arid and semiarid areas spread [13].

Other significant studies related to the long-term variability of climatic conditions over the rainfall regions of Turkey mostly indicated that annual and seasonal precipitation totals have been in the decreasing trends for many stations in Turkey, particularly at those in the Aegean and Mediterranean regions and South-eastern Anatolia and the continental interiors of Turkey that have significant potential to be arid lands in future. And it is estimated that these regions will become more sensitive to desertification in the future with anthropogenic effects such as forest fires, land conversion, urbanization, pollution, etc. [13–20]. Considering the variation of rainfall erosivity values, a trend analysis for the Mediterranean part of Turkey was performed (**Figure 1**) [21]. And, the obtained results showed that rainfall erosivity values statistically increased in the period of 1993– 2004. Not surprisingly, increasing rainfall intensities led to increase in flooding and water erosion risk in several parts of Turkey [22, 23]. This situation is not only specific to the Mediterranean region but also to the whole of arid areas. Although there is a decrease in the amount of rainfall with global warming, climate change scenarios state that rainfall intensities in dry areas significantly tend to increase [24]. Another potential threat is the degradation of soil moisture balance and the depletion of groundwater levels throughout the country as a result of reduced winter precipitations [17].

highlands [29]. Similarly, land-use transformation effects on soil erodibility in the Central Anatolian conditions were investigated [37]. And, findings showed that soil organic matter content, hydraulic conductivity and soil erodibility value statistically changed with changing land use, and soils of the recreational land and cropland were more sensitive to water erosion than those of the woodland, grassland and plantation usage. More recently, the changes in aggregate-associated and labile soil organic C and N fractions were evaluated after conversion of a natural forest to grassland and cropland in northern Turkey [38]. And, the results showed that long-term conversion of forest to grassland and cropland significantly decreased microbial biomass C, mineralizable C and physically protected soil organic C. Recently, it was reported that 70% of SOM was lost from agricultural soils due to cultivation practices; however, there is no definite information about dehumidification ratios [39]. Moreover, when evaluated in terms

**Figure 2.** Greenhouse gas emissions according to the sectors in Turkey [34].

of the levels of organic matter in Turkey, it is less than 1% in two-thirds of soils [40–42].

sediment yield was 155 ton y−1 km−2 or 119 m3

Not surprisingly, the lower organic matter contents make the soil more susceptible to erosive forces in these fragile arid and semiarid ecosystems. In addition to that, considering the topographical conditions, the country generally has a mountainous topography with higher slope degrees and shallower soil profile depth. With 47.98% of the total land having 'steepness of slope' greater than 20% and 62.15% of land, the slope greater than 12% was not suitable for machinery agricultural activities. It also accelerated the soil erosion risk [43]. Today, 16.4 million hectares of the 27.7 million hectares of agricultural land soil erosion is the major problem in Turkey. If an overall assessment of the erosion potentials of Turkey's soil is to be made, it can be said that more than 75% of the land is at risk of erosion at different levels [44, 45]. It was reported that suspended

Turkey [43, 46], considering that the soil formation rate is naturally 1 mm within 200–400 years [47]. In this way, the soil formation rate was calculated as "0.025 mm y−1, 0.025 m3 ha−1 y−1 or 0.0325 ton ha−1 y−1 if taking into consideration the upper limit of soil formation rate for arid and semiarid conditions of Turkey. Accordingly, the rate of soil loss was estimated approximately 48 times higher than the rate of soil formation in Turkey [43]. It is also well known that for agricultural purposes the breaking of the natural soil formation rates 40 times and for other reasons,

such as breaking with up to 100 times more soil losses occurred in worldwide [47, 48].

y−1 km−2 based on the detailed river observation in

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**Figure 1.** Trend analysis result for rainfall erosivity values in the Mediterranean part of Turkey.

At the basis of all these problems are actually anthropogenic effects. People in fragile ecosystems promote land degradation processes due to land-use conversions by farming in fragile soils and applying poor crop management techniques. And, those facilities have significant effects on salinization and nutrient exploitation in terms of degraded natural soil and water interactions. [25]. Another drastic effect on resource management of land-use transformations in these ecosystems could be mentioned as the mineralization of soil organic carbon (SOC) by cultivation activities. These changes under the Mediterranean climate conditions have been closely examined by various researchers [26–28]. And, the effects of these conversions on land resources, global warming and soil are being discussed frequently in recent times [29]. As reported, three main reasons of the global increase of CO<sup>2</sup> and other greenhouse gas emissions, resulting in global warming, are fossil fuel combustion, cement manufacturing and land-use changes [30]. It is known that the conversion from natural to agricultural ecosystems, tillage and soil degradation with erosion and other processes in the world resulted in a reduction of about 60% of carbon stock in the soil from the beginning of agriculture 10,000 years ago [31–33]. It is an important fact that the effect of agriculture on greenhouse gas emissions is increasing day by day in terms of CO<sup>2</sup> equivalent (**Figure 2**) [34]. In addition to inappropriate mechanization techniques, exploitation of grassland and forest areas in fragile ecosystems, especially for agricultural activities, is triggering this situation.

Soil organic carbon (SOC) is the significant parameter to evaluate land-use conversions' effects on vulnerability of soil erodibility. This unsuitable land-use changes cause the decomposition of aggregates as a result of organic matter being oxidized [5, 35, 36]. In this context, a comprehensive investigation on the effects of changes in land-use type on some soil properties was performed in a Mediterranean plateau and searched for land-use effects for three adjacent land-use types including the cultivated lands, which have been converted from pastures for 12 years, fragmented forests and unaltered pasture lands [29]. Results indicated that cultivation of the pastures caused the degradation of soil physical properties and increased the soil susceptibility to the erosion under the limited soil depth conditions in the southern Mediterranean

**Figure 2.** Greenhouse gas emissions according to the sectors in Turkey [34].

At the basis of all these problems are actually anthropogenic effects. People in fragile ecosystems promote land degradation processes due to land-use conversions by farming in fragile soils and applying poor crop management techniques. And, those facilities have significant effects on salinization and nutrient exploitation in terms of degraded natural soil and water interactions. [25]. Another drastic effect on resource management of land-use transformations in these ecosystems could be mentioned as the mineralization of soil organic carbon (SOC) by cultivation activities. These changes under the Mediterranean climate conditions have been closely examined by various researchers [26–28]. And, the effects of these conversions on land resources, global warming and soil are being discussed frequently in

**Figure 1.** Trend analysis result for rainfall erosivity values in the Mediterranean part of Turkey.

6 Arid Environments and Sustainability

recent times [29]. As reported, three main reasons of the global increase of CO<sup>2</sup>

greenhouse gas emissions is increasing day by day in terms of CO<sup>2</sup>

greenhouse gas emissions, resulting in global warming, are fossil fuel combustion, cement manufacturing and land-use changes [30]. It is known that the conversion from natural to agricultural ecosystems, tillage and soil degradation with erosion and other processes in the world resulted in a reduction of about 60% of carbon stock in the soil from the beginning of agriculture 10,000 years ago [31–33]. It is an important fact that the effect of agriculture on

In addition to inappropriate mechanization techniques, exploitation of grassland and forest areas in fragile ecosystems, especially for agricultural activities, is triggering this situation.

Soil organic carbon (SOC) is the significant parameter to evaluate land-use conversions' effects on vulnerability of soil erodibility. This unsuitable land-use changes cause the decomposition of aggregates as a result of organic matter being oxidized [5, 35, 36]. In this context, a comprehensive investigation on the effects of changes in land-use type on some soil properties was performed in a Mediterranean plateau and searched for land-use effects for three adjacent land-use types including the cultivated lands, which have been converted from pastures for 12 years, fragmented forests and unaltered pasture lands [29]. Results indicated that cultivation of the pastures caused the degradation of soil physical properties and increased the soil susceptibility to the erosion under the limited soil depth conditions in the southern Mediterranean

and other

equivalent (**Figure 2**) [34].

highlands [29]. Similarly, land-use transformation effects on soil erodibility in the Central Anatolian conditions were investigated [37]. And, findings showed that soil organic matter content, hydraulic conductivity and soil erodibility value statistically changed with changing land use, and soils of the recreational land and cropland were more sensitive to water erosion than those of the woodland, grassland and plantation usage. More recently, the changes in aggregate-associated and labile soil organic C and N fractions were evaluated after conversion of a natural forest to grassland and cropland in northern Turkey [38]. And, the results showed that long-term conversion of forest to grassland and cropland significantly decreased microbial biomass C, mineralizable C and physically protected soil organic C. Recently, it was reported that 70% of SOM was lost from agricultural soils due to cultivation practices; however, there is no definite information about dehumidification ratios [39]. Moreover, when evaluated in terms of the levels of organic matter in Turkey, it is less than 1% in two-thirds of soils [40–42].

Not surprisingly, the lower organic matter contents make the soil more susceptible to erosive forces in these fragile arid and semiarid ecosystems. In addition to that, considering the topographical conditions, the country generally has a mountainous topography with higher slope degrees and shallower soil profile depth. With 47.98% of the total land having 'steepness of slope' greater than 20% and 62.15% of land, the slope greater than 12% was not suitable for machinery agricultural activities. It also accelerated the soil erosion risk [43]. Today, 16.4 million hectares of the 27.7 million hectares of agricultural land soil erosion is the major problem in Turkey. If an overall assessment of the erosion potentials of Turkey's soil is to be made, it can be said that more than 75% of the land is at risk of erosion at different levels [44, 45]. It was reported that suspended sediment yield was 155 ton y−1 km−2 or 119 m3 y−1 km−2 based on the detailed river observation in Turkey [43, 46], considering that the soil formation rate is naturally 1 mm within 200–400 years [47]. In this way, the soil formation rate was calculated as "0.025 mm y−1, 0.025 m3 ha−1 y−1 or 0.0325 ton ha−1 y−1 if taking into consideration the upper limit of soil formation rate for arid and semiarid conditions of Turkey. Accordingly, the rate of soil loss was estimated approximately 48 times higher than the rate of soil formation in Turkey [43]. It is also well known that for agricultural purposes the breaking of the natural soil formation rates 40 times and for other reasons, such as breaking with up to 100 times more soil losses occurred in worldwide [47, 48].

Other significant problems encountered in arid and semiarid regions in Turkey are drought, salinity and desertification due to lack of precipitation, high evapotranspiration rates and unsuitable land management practices [49]. Today, agricultural sector is one of the most important users of water resources in Turkey. Annually, we are economically using 44 billion cubic meters of 112 billion cubic meters of water resources, and 74% of this water is only being used for agricultural activities [50]. Excessive and unsuitable use of both surface and subsurface waters for agricultural purposes led to significant changes in the quantity and quality of water resources. In the world, 60 million hectares, which account for about 20% of the world's irrigated areas, are facing serious salinity problem. And, more than 50% of these areas are located in India, China, USA and Pakistan. Turkey is also affected by irrigation-derived salinity at considerable levels. Today, 1.5 million hectares of soils have salinity problem due to improper management of irrigation and inadequate drainage in Turkey [2]. As a result of unsustainable agricultural practices, a considerable amount of agricultural land is put out of production each year. This situation results in reducing agricultural productivity and limiting agricultural production areas [49]. Thus, it is estimated that increased salinization of arable land will led to a land loss of 50% in 2050 [51]. At the beginning of the causes that increase the activity of salinity in these regions is the drought. In Turkey, on average, a moderate drought every 6 years and a most severe drought every 18 years are observed. For this reason, World Meteorological Organization (WMO) listed Turkey among the 76 countries that have the risk of drought [50, 52].

regulations under the sustainable land management approach are significant issues to reach

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Related to the subject, revised soil charter [55] defined the responsibilities under the three main groups, which are individuals and private organizations, government and intergovernmental organizations, to overcome degradation process and build restoration of degraded areas. The success of national scale works related to land resource sustainability is closely linked to the actions and strategies that governments will implement. For that, 10 significant actions to be realized by governments are defined [55]. Among them, the last three actions (VIII, IX and X) emphasize the need to develop the land and soil information systems to combat climate change and land degradation processes in terms of sustainability of land resources effectively.

To more effectively and sustainably combat desertification and erosion throughout Turkey, both national and international projects have to been seriously implemented. National Soil Erosion Map by USLE/RUSLE algorithm (Universal Soil Loss Equation – Revised Universal Soil Loss Equation) [56] is one of the most important attempts by General Directorate of Combating Desertification and Erosion bureau. In this context, constantly updated 'Erosion Monitoring System' is preparing for monitoring studies and creating data archive in the web [57]. It is aimed to gather available information throughout the country related to applied or planned soil conservation practices. It is supported with web-available system for applying different scenarios to estimate its effects on soil loss ratios [12]. Another important monitoring system is created for the problem of desertification. For that, a risk map has been established by determining the vulnerability classes of desertification-sensitive arid and semiarid lands of Turkey [57]. Studies at national scale are also being conducted in the same way to evaluate

In addition to this, considerable steps have been taken with the efforts to increase the presence of forests and the improvement of the existence of damaged forests. Over the last 37 years, total forest area has increased by 1.3 million hectares with afforestation projects. For future projections, it is aimed to increase the total forest area from 27 to 30% by 2023 by Ministry of Forestry and Water Affairs. Afforestation of degraded soils by converting into forests or other perennial land uses has a large potential of soil organic carbon sequestration. It will enhance

Other significant projects on management of limited land resources in Turkey are related to watershed managements, soil and water resource monitoring facilities, drought, desertification, snowslide, flood and landslide control and monitoring systems, rehabilitation of degraded areas in the context of Land Degradation Neutrality approach have been progressed

The Ministry of Food, Agriculture and Livestock, which is also responsible for combating climate change in Turkey, has various projects, strategies and policies related to agriculture

• *Land Consolidation Strategy* aims to increase the efficiency and reduce the energy usage by reaching the optimum size of the enterprises. In Turkey, 5.1 million hectares of land

the risk of wind erosion and take effective precautions against to it.

the carbon accumulation in soil organic matter [32].

by Ministry of Forestry and Water Affairs.

as follows [58–61]:

the desired targets.

According to the drought predictions, the tendency of meteorological drought in our country to turn into agricultural drought is rather high [53]. This is in our country that uses 74% of total water for agricultural purposes; the fact that agricultural drought is one of the most important limiting factors for the agriculture sector in terms of having enough moisture in the soil during the plant development periods for agricultural production [50]. According to the 2020, 2050 and 2080 projections in Turkey, a decrease in production rates of the grains such as wheat, barley, rye and oat by 4.9, 8.3 and 13.8 per percent, respectively, due to climate change and drought is estimated [54]. Considering that 80% of the 24 million hectares of agricultural land is rainfed, it is clear that if necessary measures are not taken, agricultural production will be adversely affected in the future from the climate change processes. As a result, the sustainability of land resources in semiarid and arid ecosystems, such as Turkey that has high sensitivity to land degradation in terms of climate, soil and topographic conditions, is directly related to the effective implementation of sustainable land management practices. And, it can be achieved on the condition that the science-policy interface is actively formed.
