Drylands

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Dryland farms and the Linares River [es] in the Castilla-La Mancha region of Spain Cueva de los casares 07.JPG
Dryland farms and the Linares River  [ es ] in the Castilla–La Mancha region of Spain

Drylands are defined by a scarcity of water. Drylands are zones where precipitation is balanced by evaporation from surfaces and by transpiration by plants (evapotranspiration). [1] The United Nations Environment Program defines drylands as tropical and temperate areas with an aridity index of less than 0.65. [2] One can classify drylands into four sub-types:

Contents

Some authorities regard hyper-arid lands as deserts (United Nations Convention to Combat Desertification - UNCCD) although a number of the world's deserts include both hyper-arid and arid climate zones. The UNCCD excludes hyper-arid zones from its definition of drylands.

Drylands cover 41.3% of the Earth's land surface, including 15% of Latin America, 66% of Africa, 40% of Asia, and 24% of Europe. There is a significantly greater proportion of drylands in developing countries (72%), and the proportion increases with aridity: almost 100% of all hyper-arid lands are in the developing world. Nevertheless, the United States, Australia, and several countries in Southern Europe also contain significant dryland areas. [2]

Drylands are complex, evolving structures whose characteristics and dynamic properties depend on many interrelated interactions between climate, soil, and vegetation. [3]

Biodiversity

The livelihoods of millions of people in developing countries depend highly on dryland biodiversity to ensure their food security and their well-being. Drylands, unlike more humid biomes, rely mostly on above ground water runoff for redistribution of water, and almost all their water redistribution occurs on the surface. [4] Dryland inhabitants' lifestyle provides global environmental benefits which contribute to halt climate change, such as carbon sequestration and species conservation. Dryland biodiversity is equally of central importance as to ensuring sustainable development, along with providing significant global economic values through the provision of ecosystem services and biodiversity products. The UN Conference on Sustainable Development Rio+20, held in Brazil in June 2012, stressed the intrinsic value of biological diversity and recognized the severity of global biodiversity loss and degradation of ecosystems. [5]

Drylands in East Africa

The East African drylands cover about 47% of land areas and are home to around 20 million people.[ citation needed ] Pastoralists who rely on cattle for both economic and social well-being constitute the majority of rural inhabitants in the drylands. Pastoralists use strategic movement to gain access to pasture during the dry season, using the available resources effectively. However, due to a variety of factors, this method has changed and been constrained. Challenges connected to demographics and climate change. [6] The greatest issue in drylands, is land degradation which poses a huge danger to the world's capacity to end hunger. [7] Drylands occupy around 2 million km² or respectively 90%, 75%, and 67% of Kenya, [8] Tanzania, [9] and Ethiopia respectively. More than 60 million people, or 40% of these countries’ population, live in drylands. The low level of precipitation and the high degree of variability in the climatic conditions limit the possibilities for rainfed crop production in these areas. [10]

The four sub-types

Dry and sub-humid lands

Spiny forest, Madagascar Spiny Forest, Madagascar (23985856889).jpg
Spiny forest, Madagascar

Countries like Burkina Faso, Botswana, Iraq, Kazakhstan, Turkmenistan and the Republic of Moldova, are 99% covered in areas of dry and sub-humid lands. [11] The biodiversity of dry and sub-humid lands allows them to adapt to the unpredictable rainfall patterns that lead to floods and droughts. [12] These areas produce the vast amount the world's crops and livestock. Even further than producing the vast majority of crops in the world, it is also significant because it includes many different biomes.
Biomes include:

Semi-arid lands

Semi-arid lands can be found in several regions of the world. For instance in places such as Europe, Mexico, Southwestern parts of the U.S, Countries in Africa that are just above the equator, and several Southern countries in Asia. [13]

Definition of semi-arid lands

According to literature, arid and semi-arid lands are defined based on the characteristics of the climate. For instance, Mongi et al. (2010) consider semi-arid lands as places where the annual rainfall ranges between 500 and 800mm. [14] Fabricius et al. on the other hand insist that the concept of aridity should also include conditions of aridity and semi-aridity. [15] Furthermore, they consider that a huge part of the Sub-Saharan area covering around 40 countries on the continent is land having arid conditions. Arid and semi-arid lands have much higher evapotranspiration rates as compared to the precipitation along with high air temperature mainly during dry seasons, high and almost continuous isolation throughout the year, and the presence of dry gale-force winds. [16]

Gestet forest in north Ethiopia Inda Abba Hadera forest.jpg
Gestet forest in north Ethiopia

Manifestations of Climate Change in semi-arid lands

Based on spatial repartition of greenhouse gas emissions (GGE) in the atmosphere, it seems that Africa contributes marginally in comparison to the rest of the world. Africa generates on average less than 4% of GGE produced in the world. Comparative data on GGE per person show that Europeans and Americans generate about 50 to 100 times more gas than Africans (Thiam, 2009).

Based on the consequences caused by variability and climate change, it appears that African populations are more vulnerable than others. To illustrate, the trend of reduced rainfall in the Sahel area has been marked by climatic extremes with devastating consequences on natural resources, agricultural and pastoral activities, etc. In semi-arid lands, manifestations of climate change on communities and socio-economic activities are more diversified.

The characterization and impact of the variability trend of rainfall depend on several random factors. Among the random factors, we can mention, the nature and the critical thresholds of extreme events, the frequency of these extremes according to regions, the precision of data used, and the results of mathematical simulations, and propagation. The state of scientific knowledge has allowed for the identification of the principal manifestations of climate change on the development of socio-economic activities in semi-arid lands. These manifestations are: [16]

  • Increased variability of precipitations and their characteristics (number of rainfall days, date of start, length of the season) that can be translated to an abrupt alternative between dry and humid years.
  • a shorter rainy season correlatively to its late start;

an increase in the occurrence of dry sequences that can happen at any time in space and time during the actual period;

  • a tendency to the increment of maximal rains cumulated in fewer consecutive days, that causes damage and important loss on socio-economic systems (culture, infrastructure) and humans;

Dry and violent winds associated with very scarce rainfall that prevent enough humidification of the soils; making difficult the development of the whole vegetal life;

  • The actual rise without compromise of observed temperatures according to forecasts of the GIEC creates stressful thermal situations that may seriously handicap vegetal and animal productivity.

Adaptation, Resilience in SALS

In semi-arid lands where pastoralism is the principal activity, the main adaptation measures are an early departure to transhumance, the reduction of the size of the herd, a change in the management of water, and diversification of paths of transhumance. [17] This allows breeders to safeguard their livestock and prevent huge losses as was the case in the drought of the seventies. Breeders purchase stock for the livestock or simply stock it. They become proactive (engage in trade, real estate, guarding, transport) in certain countries like Burkina Faso, Senegal, Mali, and Kenya. [17] [18] These adaptation strategies allow them to be more resilient to the socio-economic consequences of climate change.

Brazilian semi-arid region Brazilian semi-arid region.jpg
Brazilian semi-arid region

Arid lands.

Arid chaco Arid chaco.jpg
Arid chaco

Arid lands make up about 41% of the world's land and are home to 20% of the world's people. [19] They have several characteristics that make them unique :

  1. Rainfall scarcity
  2. High temperatures
  3. Evapotranspiration and low humidity

Hyper-arid lands

These lands cover 4.2% of the world [20] and consist of areas without vegetation. They receive irregular rainfall that barely surpasses 100 millimeters, and in some cases, they may not receive rainfall for several years.


Dry land Dry land - panoramio.jpg
Dry land

See also

Related Research Articles

<span class="mw-page-title-main">Desertification</span> Process by which fertile areas of land become increasingly arid

Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become arid. It is the spread of arid areas caused by a variety of factors, such as overexploitation of soil as a result of human activity and the effects of climate change. Geographic areas most affected include the Sahel region in Africa, the Gobi Desert and Mongolia in Asia as well as parts of South America. Drylands occupy approximately 40–41% of Earth's land area and are home to more than 2 billion people.

<span class="mw-page-title-main">Geography of Somalia</span> Geographical features of Somalia

Somalia is a country located in the Horn of Africa which officially consists of the intra-46th meridian east territory, the seven federal member states, namely Galmudug, Hirshabelle, Jubaland, South West, Puntland, Somaliland, Khaatumo and the municipality of Benadir. It is bordered by Ethiopia to the west, the Gulf of Aden to the north, the Somali Sea and Guardafui Channel to the east, and Kenya to the southwest. With a land area of 637,657 square kilometers, Somalia's terrain consists mainly of plateaus, plains and highlands. Its coastline is more than 3,333 kilometers in length, the longest of mainland Africa. It has been described as being roughly shaped "like a tilted number seven".

<span class="mw-page-title-main">Deserts and xeric shrublands</span> Habitat type defined by the World Wide Fund for Nature

Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this habitat type vary greatly in the amount of annual rainfall they receive, usually less than 250 millimetres (10 in) annually except in the margins. Generally evaporation exceeds rainfall in these ecoregions. Temperature variability is also diverse in these lands. Many deserts, such as the Sahara, are hot year-round, but others, such as East Asia's Gobi, become quite cold during the winter.

<span class="mw-page-title-main">Semi-arid climate</span> Climate with precipitation below potential evapotranspiration

A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-arid climates, depending on variables such as temperature, and they give rise to different biomes.

<span class="mw-page-title-main">Dryland farming</span> Non-irrigated farming in areas with little rainfall during the growing season.

Dryland farming and dry farming encompass specific agricultural techniques for the non-irrigated cultivation of crops. Dryland farming is associated with drylands, areas characterized by a cool wet season followed by a warm dry season. They are also associated with arid conditions, areas prone to drought and those having scarce water resources.

<span class="mw-page-title-main">Environmental degradation</span> Any change or disturbance to the environment perceived to be deleterious or undesirable

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<span class="mw-page-title-main">Rangeland</span> Biomes which can be grazed by animals or livestock (grasslands, woodlands, prairies, etc)

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An aridity index (AI) is a numerical indicator of the degree of dryness of the climate at a given location. The American Meteorological Society defined it in meteorology and climatology, as "the degree to which a climate lacks effective, life-promoting moisture". Aridity is different from drought because aridity is permanent whereas drought is temporary. A number of aridity indices have been proposed ; these indicators serve to identify, locate or delimit regions that suffer from a deficit of available water, a condition that can severely affect the effective use of the land for such activities as agriculture or stock-farming.

<span class="mw-page-title-main">Climate classification</span> Systems that categorize the worlds climates

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<span class="mw-page-title-main">Holdridge life zones</span> Global bioclimatic scheme for the classification of land areas

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<span class="mw-page-title-main">Climate of Zambia</span>

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<span class="mw-page-title-main">Climate of Mexico</span> Overview of the climate of Mexico

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<span class="mw-page-title-main">Earth rainfall climatology</span> Study of rainfall

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<span class="mw-page-title-main">Climate of Africa</span> Climate of the continent

The climate of Africa is a range of climates such as the equatorial climate, the tropical wet and dry climate, the tropical monsoon climate, the semi-arid climate, the desert climate, the humid subtropical climate, and the subtropical highland climate. Temperate climates are rare across the continent except at very high elevations and along the fringes. In fact, the climate of Africa is more variable by rainfall amount than by temperatures, which are consistently high. African deserts are the sunniest and the driest parts of the continent, owing to the prevailing presence of the subtropical ridge with subsiding, hot, dry air masses. Africa holds many heat-related records: the continent has the hottest extended region year-round, the areas with the hottest summer climate, the highest sunshine duration, and more.

Rainfed agriculture is a type of farming that relies on rainfall for water. It provides much of the food consumed by poor communities in developing countries. E.g., rainfed agriculture accounts for more than 95% of farmed land in sub-Saharan Africa, 90% in Latin America, 75% in the Near East and North Africa, 65% in East Asia, and 60% in South Asia.

<span class="mw-page-title-main">Climate change in Africa</span> Emissions, impacts and responses of the African continent related to climate change

Climate change in Africa is an increasingly serious threat as Africa is among the most vulnerable continents to the effects of climate change. Some sources even classify Africa as "the most vulnerable continent on Earth". This vulnerability is driven by a range of factors that include weak adaptive capacity, high dependence on ecosystem goods for livelihoods, and less developed agricultural production systems. The risks of climate change on agricultural production, food security, water resources and ecosystem services will likely have increasingly severe consequences on lives and sustainable development prospects in Africa. With high confidence, it was projected by the IPCC in 2007 that in many African countries and regions, agricultural production and food security would probably be severely compromised by climate change and climate variability. Managing this risk requires an integration of mitigation and adaptation strategies in the management of ecosystem goods and services, and the agriculture production systems in Africa.

<span class="mw-page-title-main">Climate change in Kenya</span> Emissions, impacts and responses of Kenya related to climate change

Climate change is posing an increasing threat to global socio-economic development and environmental sustainability. Developing countries with low adaptive capacity and high vulnerability to the phenomenon are disproportionately affected. Climate change in Kenya is increasingly impacting the lives of Kenya's citizens and the environment. Climate Change has led to more frequent extreme weather events like droughts which last longer than usual, irregular and unpredictable rainfall, flooding and increasing temperatures.

Natural disasters in Nigeria are mainly related to the climate of Nigeria, which has been reported to cause loss of lives and properties. A natural disaster might be caused by flooding, landslides, and insect infestation, among others. To be classified as a disaster, there is needs to be a profound environmental effect or human loss which must lead to financial loss. This occurrence has become an issue of concern, threatening large populations living in diverse environments in recent years.

<span class="mw-page-title-main">Desertification in Africa</span> Causes and effects of land degradation

Desertification in Africa is a form of land degradation that involves the conversion of productive land into desert or arid areas. This issue is a pressing environmental concern that poses a significant threat to the livelihoods of millions of people in Africa who depend on the land for subsistence. Geographical and environmental studies have recently coined the term desertification. Desertification is the process by which a piece of land becomes a desert, as the word desert implies. The loss or destruction of the biological potential of the land is referred to as desertification. It reduces or eliminates the potential for plant and animal production on the land and is a component of the widespread ecosystem degradation. Additionally, the term desertification is specifically used to describe the deterioration of the world's drylands, or its arid, semi-arid, and sub-humid climates. These regions may be far from the so-called natural or climatic deserts, but they still experience irregular water stress due to their low and variable rainfall. They are especially susceptible to damage from excessive human land use pressure. The causes of desertification are a combination of natural and human factors, with climate change exacerbating the problem. Despite this, there is a common misconception that desertification in Africa is solely the result of natural causes like climate change and soil erosion. In reality, human activities like deforestation, overgrazing, and unsustainable agricultural practices contribute significantly to the issue. Another misconception is that, desertification is irreversible, and that degraded land will forever remain barren wastelands. However, it is possible to restore degraded land through sustainable land management practices like reforestation and soil conservation. A 10.3 million km2 area, or 34.2% of the continent's surface, is at risk of desertification. If the deserts are taken into account, the affected and potentially affected area is roughly 16.5 million km2, or 54.6% of all of Africa. 5.7 percent of the continent's surface is made up of very severe regions, 16.2 percent by severe regions, and 12.3 percent by moderate to mild regions.

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