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.
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:
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.
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.
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
Organize an excursion close to your school. Look for an area damaged by erosion.
How could you stop the erosion process and make the soil more fertile?
Do you know of a polluted area nearby?
In your view, how long has this area existed and what needs to be done so that this area becomes less polluted and eventually restored?
Try this experiment:
Take 4 buckets filled with soil.
Plant an equal number of grasses in each. Place two buckets permanently in the sun.
Place the other two in a shady area. Label the buckets. Regularly water one of the buckets placed in the sun and one in the shade.
Do the same with the other 2 buckets (water one of them and not the other). Keep a check on the buckets, and at the end of a few weeks describe and compare the grasses.
What do you notice? What do you think has happened?
Find 2 large buckets.
In the centre of one of them, place a compact mix of water and soil.
In the other bucket, place some plants and their accompanying soil, in the centre.
Now, water the 2 buckets with a substantial quantity of water. What do you notice?