**2.1 Destruction of plant resources**

Degradation of vegetation through harvesting and destruction is the dominant desertification process. Ma et al. [7] cited vegetation degradation as an essential factor in southwest China's socio-economic development. The researchers also identified nutrients in the soil, especially N, P, and K, as the main factors influencing plant species composition in rocky desert areas. Vegetation conservation in Greece has been introduced as an influential factor in reducing water and wind erosion [6]. Vegetation cover and vegetation composition are the most common characteristics of many terrestrial ecosystems. These characteristics are associated with many ecosystem services, including biodiversity, soil and water conservation, food production, and fiber. It is also common to use these two indicators to assess land degradation and rehabilitation and rehabilitation project success. Deforestation contributes to about 17% of annual human greenhouse gas (GHG) emissions [8]. Humans resort to deforestation to meet their wood and energy needs. Deforestation for fuelwood is much more significant in developing countries with high populations and less access to commercial energy sources. Forests are also being destroyed to provide more land for agriculture [9]. Desertification risk scenarios in northeastern Brazil predict that 75% of forest areas will decline from 2010 to 2040. In this scenario, most forest areas will be replaced by agricultural lands [1]. Therefore, lands with more suitable vegetation are more resistant to degradation. In contrast, poor vegetation areas are fragile and accelerate desertification over time due to adverse environmental factors.

#### **2.2 Destruction of soil resources**

Land degradation in recent years has become a primary global concern due to increased waste disposal and demand for food production. Soil flexibility is limited, and soil degradation can never be easily reversed. In this century, the focus of land degradation has been on soil erosion, since forests, grasslands, and wetlands have been destroyed for crop production.

#### *Desertification in Agricultural Lands: Approaches to Mitigation DOI: http://dx.doi.org/10.5772/intechopen.98795*

Severe land use without proper soil management, especially in fragile ecosystems, can accelerate desertification [10]. Human activities or climate change negatively affecting vegetation can lead to irreversible soil degradation in semiarid regions [11]. Soil degradation in the semi-arid region of northeastern Brazil is driven by a limited set of variables, the most important of which are climatic, economic, and population growth variables. These factors lead to the expansion of agricultural lands and overgrazing, which increase the rate of deforestation [12].

Soil degradation processes:

#### *2.2.1 Physical destruction*

These refer to drastic changes in the soil's physical properties, including reduced permeability and porosity, reduced stability of the soil structure, and loosening and compaction of the soil [13]. Root zone compaction is the main form of physical degradation in arable lands and pastures, reducing soil fertility and reducing the amount of soil organic matter. Low structural stability of compacted soils leads to high vulnerability to mechanical stresses from agricultural operations. Therefore, reducing soil permeability, increasing runoff, increasing erosion, reducing soil aeration, and reducing biomass production are side effects of soil compaction and tuber formation that should be considered an indicator to assess the intensity of desertification.

#### *2.2.2 Chemical degradation*

A change in the soil's chemical properties in such a way that it interferes with nutrient uptake is called soil chemical degradation. Soil salinization, soil acidity imbalance, soil leaching, and ultimately reduced soil fertility are the most critical consequences of chemical soil degradation. Chemical degradation of soil can also occur due to increased concentrations of some toxic components such as aluminum.

#### *2.2.3 Soil biodegradation*

Microorganisms in agricultural soils play a crucial role in soil fertility. The reduction of soil organic matter and living microorganisms in soil is called biodegradation. Humus is an essential soil substance that increases soil porosity, soil stability, soil water holding capacity, and micronutrients. Organic matter depletion is the first state of biodegradation that leads to changes in other soil properties. In arid regions, depletion of soil organic matter leads to a decrease in soil moisture-holding capacity, a reduction in crops, and an increase in soil erosion [14]. Land-use change affects the physical, chemical, and biological properties of the soil. The conversion of pastures into agricultural lands in some areas of Iran has reduced the soil quality and increased soil degradation. It has been reported that the transformation of ranges to agricultural fields in three regions in Isfahan province has reduced soil organic matter by about 26% in agricultural lands, which is probably due to poor vegetation density (**Figure 1**) [15].

#### **2.3 Soil and water erosion**

In the last century, the significant destruction of land has been through soil erosion, as the areas of forests, grasslands, and wetlands have been removed for crop production. Soil erosion is one of the essential desertification processes during which soil particles are separated, transported, and deposited. Moreover, the soil decays and its organic matter decreases in the process of erosion. Humans obtain more than 99.7% of their food (calories) from land and less than 0.3% from the

#### **Figure 1.**

*Percentage of soil organic matter in the lands of three regions. The same letters for the regions indicate no statistical difference at the 5% level with the LSD test [15].*

**Figure 2.** *Erosion stages by water [17].*

oceans and other aquatic ecosystems. About 10 Mha of crops are lost each year due to soil erosion, thus reducing the amount of arable land available for food production [16]. Water erosion means the removal, transport, and deposition of soil particles by rain, runoff, and gravity **Figure 2** [18] shows the mechanism of water erosion. Rain erosion is one of the most critical water erosion types, which occurs more widely than other types. As rainfall occurs, the raindrops onto the soil surface and makes the first contact with the soil [19]. The loosening of soil particles or the detachment process takes place when soil particles disengage as the rain touches down on the soil. Afterward, soil particles are transported by rolling, splashing, or dragging and translocate to another place. Finally, soil particles are deposited at some other place at a lower elevation [17].
