Introductory Chapter: Arid Environment

1. Introduction

Arid environments cover more than one-third of the world’s land area and represent the most common habitat on Earth after the oceans. Aridity poses a threat to the environment, as well as the economy, security, development, food security, and social life around the world. The causes of increased aridity are complex and are thought to be both natural and man-made. Factors such as climate change, population growth, soil erosion, inappropriate irrigation, wrong farming, soil, water, and groundwater contamination, urbanization, deforestation, improper water management, desertification of arid and semiarid zones appear as causes of drought.

This book covers a wide range of scientific research studies, from water management to groundwater management, from land rehabilitation to soil reclamation, which will help prevent and minimize man-made aridity. In addition, many studies related to aridities such as environmental education, environmental awareness, sustainable development, and management policies and plans are also welcome.

2. Aridity

Aridity is the imbalance between the long-term average water supply and the long-term average water demand [1]. Unlike drought, which is defined as a period of abnormally dry air long enough to cause a serious hydrological imbalance, aridity is permanent, not temporary. Aridity is a condition in which the amount of usable water in an area is reduced to such an extent that it hinders or prevents the growth and development of plants and animals. Regions with arid climates lose or tend to lose their vegetation. These regions, which are generally located close to the equator, are called xeric, arid, or desert according to their aridity levels. In the more extreme areas, called extreme arid deserts, the average annual precipitation is below 25 mm, under which conditions microorganisms must cope with not only by water scarcity but also by deadly UV radiation, high and low temperatures, high evaporation rates, prolonged drying times, oligotrophic conditions, and high salinity levels. Aridity is often evaluated with the aridity index (Table 1) and aids in determining whether there is a water shortage in the region and deciding the measures to be taken in case of a possible arid climate [3].

	Climate type	Aridity i
Dry land subtypes	Hyper-arid	AI < 0.05
	Arid	0.05 ≤ AI < 0.2
	Semiarid	0.2 ≤ AI < 0.5
	Dry subhumid	0.5 ≤ AI < 0.65
Non-dry lands	Humid	AI ≥ 0.65
	Cold	PET* < 400 mm

Table 1.

Climate classification and dry land subtypes based on the Aridity Index.

*

PET: Potential evapotranspiration

Adopted by [2]

3. Sustainable development of arid regions

The main causes of dry weather in arid ecosystems are high regional temperature caused by the sun's rays, high pressure caused by pressure centers, ocean coast streams, high mountain ranges and high plateaus, lack of exposure to marine influences, absence of upward movement of air, and air turbulence [4]. In addition to the adverse effects of the climatic factors, arid areas also have some potential if they are well analyzed and defined. Among them are solar and wind energies; salt, sand, and gravel pits; coal, uranium, copper, and zinc mines; natural touristic sights and horticultural activities. To evaluate these potentials and to realize possible industrial and tourism investments, sustainable development plans and activities in arid areas should be investigated [5]. Environmental management and sustainable development approaches in arid ecosystems are summarized in Figure 1.

Figure 1.

Environmental management and sustainable development approaches in arid ecosystems (Adopted from [4].

4. Combating climate change and drought

Climate change is one of the most important global challenges of our time, with its borderless nature that affects all countries regardless of their level of development. In the report titled "Human Cost of Climate-Related Natural Disasters" published by the UN in October 2015, 90% of a total of 6,457 natural disasters recorded in 20 years are caused by floods, storms, heat waves, droughts, and other extreme climate movements. It is stated that 606 thousand of people have lost their lives and 4.1 billion people have been affected since 1995 due to disasters caused by extreme climate movements. In total, 80% of the poorest group, which receives the least share of income distribution worldwide, lives in rural areas doing small-scale agriculture and animal husbandry. The decrease in precipitation due to climate change and the pressure on natural resources caused by soil degradation can force these vulnerable groups to migrate, which triggers instability and brings security risks [6]).

Aridity/drought and desertification are important environmental challenges of our time and are directly related to climate change. Desertification, drought, and land degradation because of extreme weather conditions triggered by climate change are a global test that threatens the living space and most basic livelihood of most of the world's population and may pose a food security risk, rather than an environmental problem. Balancing land degradation is key to achieving the Sustainable Development Goals (SDGs). On the other hand, sustainable land management is also of great importance for combating climate change, because the soil whose organic component is preserved acts as a sink with the ocean and forests by trapping the carbon in the atmosphere. It is possible to realize approximately one-third of the greenhouse gas reduction potential with land degradation balancing and sustainable land use. The most important tool for balancing land degradation and combating desertification is the "United Nations Convention to Combat Desertification in Countries Exposed to Severe Drought and/or Desertification, Especially in Africa" (UN Convention to Combat Desertification – UNCCD) adopted in 1994. The Convention is the only binding international agreement linking the issue of environment and development with sustainable land management [6].

5. Conclusions

Within the scope of combating climate change, the transition to a low-carbon economy on a global level envisages a radical transformation that will change people's lifestyles, production, and manufacturing methods. For this reason, efforts to combat and adapt to climate change should not be perceived as a mere environmental problem. This struggle can directly affect the growth strategies, energy policies, health and agriculture-related programs, use of water resources, food security, transition to a low-carbon economy, and sustainable development goals to be followed by developed and developing countries and may be decisive in their development. To achieve these goals, developed countries need to fulfill their commitments to financing, technology transfer, and capacity building. To combat aridity and desertification, it is necessary to determine the situation on a global scale and to force countries to work on combating drought and desertification. In addition, national and global funds should be mobilized to promote good practices, contribute to sustainable development in countries affected by drought and desertification, develop cooperation in combating drought and desertification, and support studies in this field.