Soil erosion is a natural
process. It becomes a problem when human activity
causes it to occur much faster than under natural
DID YOU KNOW
* Annual soil loss in South Africa is estimated
at 300 - 400 million tonnes, nearly three tonnes
for each hectare of land.
* Replacing the soil nutrients
carried out to sea by our rivers each year, with
fertilizer, would cost R1000 million.
* For every tonne of maize,
wheat, sugar or other agricultural crop produced,
South Africa loses an average of 20 tonnes of
* The FAO (Food and Agriculture
Organisation, a branch of United Nations)
estimates that the global loss of productive land
through erosion is 5-7 million ha/year.
CAUSES OF SOIL EROSION
Wind and water are the main agents of soil
erosion. The amount of soil they can carry away
is influenced by two related factors:
* speed - the faster either
moves, the more soil it can erode;
* plant cover - plants protect
the soil and in their absence wind and water can
do much more damage.
THE IMPORTANCE OF
Plants provide protective cover on the land and
prevent soil erosion for the following reasons:
* plants slow down water as it
flows over the land (runoff) and this allows much
of the rain to soak into the ground;
* plant roots hold the soil in
position and prevent it from being washed away;
* plants break the impact of a
raindrop before it hits the soil, thus reducing
its ability to erode;
* plants in wetlands and on the
banks of rivers are of particular importance as
they slow down the flow of the water and their
roots bind the soil, thus preventing erosion.
The loss of protective
vegetation through deforestation (see Enviro
Facts "Deforestation"), over-grazing,
ploughing, and fire makes soil vulnerable to
being swept away by wind and water. In addition,
over-cultivation and compaction cause the soil to
lose its structure and cohesion and it becomes
more easily eroded. Erosion will remove the
top-soil first. Once this nutrient-rich layer of
soil is gone, few plants will grow in the soil
again. Without soil and plants the land becomes
desert-like and unable to support life - this
process is called desertification (see Enviro
Facts "Desertification"). It is very
difficult and often impossible to restore
POLITICS, ECONOMICS AND
SOIL EROSION To understand soil erosion
we must be aware of the political and economic
factors affecting land users.
In South Africa apartheid
policies ensured that 42% of the people lived on
13 % of the land (the "homelands").
This overcrowding has resulted in severe erosion.
As the land became increasingly degraded and thus
less productive, subsistence farmers were forced
to further overuse the land. The intensive
agriculture and overgrazing that followed caused
greater degradation. Soil erosion can be seen as
both a symptom of underdevelopment (i.e. poverty,
inequality and exploitation), and as a cause of
underdevelopment. A reduced ability to produce,
invest one's profit and increase productivity,
contributes to increasing poverty, and can lead
to desertification, drought, floods, and famine.
On commercial farm lands,
overstocking, mono-cropping, and the ploughing of
marginal lands unsuitable for cultivation has led
to soil erosion and desertification. Frequently
these practices have been unwittingly encouraged
by the state offering subsidies which made it
profitable to exploit the land in the short-term.
PREVENTING SOIL EROSION
Preventing soil erosion requires political,
economic and technical changes.
Political and economic changes
need to address the distribution of land in South
Africa as well as the possibility of incentives
to encourage farmers to manage their land
Aspects of technical changes
* the use of contour ploughing
and wind breaks;
* leaving unploughed grass
strips between ploughed land;
* making sure that there are
always plants growing on the soil, and that the
soil is rich in humus (decaying plant and animal
remains). This organic matter is the
"glue" that binds the soil particles
together and plays an important part in
* avoiding overgrazing and the
over-use of crop lands;
* allowing indigenous plants to
grow along the river banks instead of ploughing
and planting crops right up to the water's edge;
* encouraging biological
diversity by planting several different types of
* conservation of wetlands (see
Enviro Facts "Wetlands" and "River
WHAT CAN YOU DO
In addition to the guidelines above, try the
* Pathways can be easily eroded
when water flows over them. Prevent this by
breaking the water flow with logs, stone packs or
* Become a `Donga Doctor' and
repair erosion gullies (see "Soil is
RESTORING THE LAND:
ENVIRONMENT AND CHANGE IN POST-APARTHEID SOUTH
AFRICA. M. Ramphele and C. McDowell
(eds). Panos, London, 1991.
NEW GROUND. A
magazine published by the Environmental and
Development Agency, address below.
ENVIRONMENTS INTO THE 21ST CENTURY. B.
Huntley, C. Sunter and R. Siegfried. Human,
Rousseau & Tafelberg, Cape Town, 1990.
YOUR HEART YOUR PLANET:
SOUTH AFRICAN EDITION. H. Diamond.
Eartheart Publications, Cape Town, 1990.
BACK TO EARTH.
J. Clarke. Southern Books, Johannesburg, 1992.
SOIL IS WEALTH.
KwaZulu Dept. Nature Conservation, address below.
Desertification, Deforestation, River Catchments,
Wetlands, Estuaries, Soil, Compost.
Box 394, Howick, 3290. Tel. 0332-305721.
Development Agency. PO Box 322, Newtown,
2113. Tel. 011-834 1905
The Valley Trust.
PO Box 33, Botha's Hill, 3660. Tel. 031-777 1930.
The Farmers Support
Group. University of Natal, PO Box 375,
Pietermaritzburg, 3200. Tel. 0331-68385/6/7.
KwaZulu Dept. Nature
Conservation. Head Office, P/Bag X98,
Ulundi, 3838. Tel. 0358-700552.