Environmental consequences
of desertification

1. 2.

Objective: To introduce the physical consequences of desertification

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Intro

Soils erode or disappear

Water becomes scarce

Biodiversity decline

Consequences of land degradation

Activities

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Pictures:

1. When drought periods are sustained, the soil surface hardens and begins to break up. Cracks appear forming deep fissures that damage the soil structure. When rains eventual arrive, the water seeps into the cracks rather than being retained on the surface.
© Jean-Michel Battin

2. Soil salinity has immediate consequences on the ability of vegetation to maintain and regenerate itself.
© Michel Le Berre

3. Mustang in Nepal:
wind erosion. In some cases, the wind causes land erosion, if violent enough, the superficial layers are blown away
© Yazid Tizi

4. Erosion removes part of the soil and often unearths root systems.
© Michel Le Berre

5. 6. Examples of hydraulic erosion. Soils are washed away by the rains, when they dry up, a crust forms that renders the soil impermeable, thereby reducing water infiltration.
© Yann Arthus-Bertrand / Earth from Above / UNESCO

 

Human activities in the drylands, together with climatic factors and drought conditions, influence changes in the natural environment and its productivity. In return, these changes bear consequences on human populations and the quality of life.

Soils erode or disappear

This precious covering, the very flesh of the planet, is painfully slow to form and can be destroyed terrifyingly fast. Just a thin layer of soil can take centuries to develop but, if mistreated, can be blown and washed away in a few seasons. Soil is now rapidly vanishing all over the planet.
Despite the fact that animals and plants are able to adapt to the drylands, desertification has serious consequences on the environment. Depending on the type of agricultural technique employed, different forms of land degradation occur.
The following have been observed:

• loss of nutritive matter (due to agricultural over-exploitation).
• loss of soil surface due to wind and rain erosion, particularly due to the loss of vegetation (See the case study from Spain).
• landslides occur by the action of water, also due to the effects of vegetation loss (See the case study from Kenya).
• increased salinity and soil acidification (due to irrigation malpractice) (See the case study from the Aral Sea).
• soil pollution (due to the excessive use of chemical fertilizer).
• the effects of compression and the encrusting of the soil surface (due to heavy use of agricultural machinery).

Water becomes scarce or is threatened

Land degradation in the drylands can have direct consequences on the water cycle.
If there is low rainfall then drought ensues: groundwater reserves do not refill, water sources become depleted, wells run dry, plants and animals die and humans have to migrate to more hospitable regions.

On the other hand, during periods of high rainfall, the ensuing floods kill people and animals, notably in regions where vegetation cover is reduced or totally destroyed.
The torrential rain flow causes a substantial loss of soil, which is then flushed out by the rains, and when the land becomes dry again, a hard crust forms on the surface that renders it impermeable, reducing water infiltration.

Biodiversity decline

Land degradation due to drought, salinity or over-exploitation has immediate consequences on the capacity of vegetation to maintain or reconstruct itself. Animal species, dependant on this vegetation, have to migrate to other areas to find sufficient resources or they risk disappearing altogether. The importance of this loss derives from the fact that animal and plant species from the drylands are particularly well adapted to this extreme environment. They act as indicators of the environmental condition of these areas and their disappearance is a sign of significant habitat degradation. Moreover, these species remain important resources for the population. Their disappearance increases food insecurity and the impoverishment of the world’s most fragile populations.

Consequences of land degradation

• Erosion: the loose particles and nutritive elements of the soil are flushed out.
• In irrigated lands, where water from underground reserves is often polluted, evaporation leads to a rise in the mineral salts to the surface resulting in high salinity, rendering the soil unsuitable for crops, since they are intolerant of high salt concentrations and may consequently die.
• The vegetation cover is not given enough time to re-establish itself during intensive grazing periods or when grazing activities affect plots that have already been cultivated.
• Due to the acceleration of erosion by rain as a direct result of clearings and deforestation, the forest ecosystem disappears. This has severe consequences on soil fertility as well as on the preservation of animal and plant species.
  In fact, roots maintain soil structure and can limit soil erosion since they contribute to water infiltration, which reduces water run-off, encouraging the composition of a rich and productive soil. Also, tree leaves reduce the action of the wind on the soil surface. Dead tree parts that fall to the ground decompose and enrich the soil with organic matter.

5. 6. Examples of hydraulic erosion. Soils are washed away by the rains, when they dry up, a crust forms that
renders the soil impermeable, thereby reducing water infiltration.
© Yann Arthus-Bertrand / Earth from Above / UNESCO

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