Desertification Flashcards
Define desertification
The process by which fertile land becomes desert typically as a result of drought, deforestation, or inappropriate agriculture.
Desertification is the loss of productive land in specific dryland regions of the world. It is an extreme process, whereby areas become more desert like.
Describe the distribution of deserts during the LGM
The spatial distribution of deserts during the LGM is evenly clustered. Large areas of Australia, Northern and Southern Africa, Central Asia, and Northern Siberia and Canada have a less than 2% vegetation cover and are as a result classified as extremely deserted during the LGM. An exception to the evenly clustered pattern would be the linear distribution of deserts in high latitudinal regions near to the arctic circle such as Northern Europe and Northern Siberia and Canada.
Describe the distribution of deserts during the HCO
The spatial distribution of deserts during the HCO is unevenly clustered. The only regions with less than a 2% vegetation cover are small areas in central Asia, southern Africa and western South America. There are no exceptions to the pattern.
Describe the distribution of deserts today
The spatial distribution of deserts today are unevenly clustered. Regions with a 2% vegetation cover include a large area of northern Africa (the Sahara) and the Middle East, and smaller areas in central Asia, southern Africa and western South America. There are no exceptions to the pattern.
Describe the distribution of desertification globally
The spatial distribution of regions vulnerable to desertification is linear adjacent to arid to hyper-arid regions. An example of this pattern would be the stretch of land in central Africa spanning from the Atlantic Ocean to the Red Sea being adjacent to the Sahara Desert resulting in a very high vulnerability to desertification. Another example is the areas of land surrounding the deserts of Australia such as the Gibson Desert are all at a very high vulnerability to desertification. An exception to this pattern would be the region of north-eastern South America which is surrounded by forests and grasslands being highly vulnerable to desertification likely due to deforestation.
Describe the nature of desertification
Much of life on Earth is dependant on soil.
It helps regulate climate, provide kilojoules for life, filter water amongst other things.
Although it is considered a renewable resource, it takes an extremely long time to renew 500 years for 25 cm of topsoil.
Soil is being lost from agricultural regions and 10 – 40 times faster than it is being formed, via the process of land degradation.
The loss of vegetation can reduce soil nutrients and soil structure which reduces the ecosystems ability to recover quickly
Globally, two billion hectares of land are degraded, with 12 million hectares being lost per year.
Define drylands regions
Drylands are areas with growing seasons less than 179 days
Describe drylands regions
Reduced productivity of dryland regions, reduced land cover and increased erosion.
Occurs at the margins of dryland areas
40% of the world classified as dryland (including western Victoria)
Drylands support 1/3 of the world’s population & 50% of the world’s livestock
Describe the rate of the Desertification
12 million hectares of land per year
Combination of drying climate (+ droughts), increasing population (including refugees), fire-wood collection, over-grazing.
Vicious cycle of degradation and increasing pressure.
Weak government regulation.
There is a strong spatial association between countries with large scale land degradation and low levels of economic development
Discuss why Dryland regions are most at risk to desertification
Water scarcity – low irregular, unpredictable precipitation (temporal and spatial)
High evaporation – rain that does fall, falls in short burst and then evaporates quickly
Windy – Strong winds and poor soil = dust storms. Little organic matter in soil and very low soil moisture.
5 – 10 times longer for natural soil regeneration and vegetation regeneration
Given this, they are prone to desertification, over-exploitation and poor land use.
Outline Environmental factors causing desertification
Loss of vegetation cover – wood is the main source of heating, cooking and construction. 50-90% of energy used in Africa is derived from wood clearing
Loss of vegetation cover – grazing animals deplete vegetation
Loss of vegetation cover – trees considered as to be competing with agricultural crops
Loss of vegetation- exposes soils to both wind and water erosion
Drought – if prolonged it can cause desertification. Land can usually recover, unless land use is unsustainable and it is prolonged.
Climate Change - Changing rainfall patterns, temperature stress on vegetation, soil erosions. Without vegetation cover, there is lower humidity, fewer clouds, more sun and thus higher temperatures and less precipitation.
Excessive water – when added to soils cab cause a rise in water tables and bring salts to the surface (salinity). Vegetation dies off and soil is degraded.
Over irrigation - when large scale irrigation systems remove water from a natural water body, desertification can occur
Outline Economic factors causing desertification
Poverty – both a cause and consequence of desertification. In some areas people have no choice but to overcrop, overgraze and reduce the time soil has to recover between crops.
Overgrazing – becomes unsustainable when there is not enough time for plants to recover (soil is trampled and compacted and erodes)
Over cultivation – occurs when the same land is used repeatedly without the chance to rest and recover. Subsistence farming traditionally relies on periods of fallow.
Outline Social factors causing desertification
Population growth – given 2.5 billion people live in dryland areas, then an increase in people increases pressure on these areas. Rapid population growth drives an increasing need for drylands ecosystems to provide food, water, animal feed, building materials and fuelwood. Areas will in turn require more agricultural land to mitigate food insecurity
Outline Political factors causing desertification
Pressure to provide for basic human needs – means that environmental needs get little attention. There are insufficient laws dealing with land and resource ownership.
Restriction of nomadic farming – traditional farming method that moves grazing to match rainfall patterns and pasture. In modern times this is restricted which leads to overgrazing.
Conflict – conflict can create a movement of refugees into degraded areas putting further pressure on land resources.
Describe the impacts of Desertification
Deforestation: Vegetation plays a critical role in protecting land from degradation and desertification. This loss of vegetation cover can affect other aspects of the environment as vegetation protects soil and crops from wind erosion, decomposing plant matter improves soil fertility and soil is held together by the root system.
Soil erosion: land unprotected by vegetation is exposed to water and wind erosion. In hot and dry conditions, exposed soils can develop a crusted surface which further reduces water infiltration. This soil once dried out can move large distances (Scientists have tracked down soils blown from northern Africa blown to North America and London)
Loss of biodiversity: loss of habitat and decline in biodiversity. This includes both plants and animals.
Economic losses: many people rely on farming in drylands for their livelihood. Therefore loss of land results in poverty.
Human wellbeing: Food production reduces leading to food insecurity, reduced incomes, poor diets, illness.
Essentially desertification is a symptom of poverty and a cause of poverty.
80% of the Sahelian population rely on the land and is resources for a living , thus they are highly vulnerable to natural disasters or human induced land degradation. There has been a cyclic pattern of drought and famine over the past decade. In 2017 an estimated 30 million people suffered from food insecurity as a result of desertification in the Sahel region.
