main groups of land degradation processes are normally distinguished.
Mass movement is the movement of soil and/or rock downslope, under the
influence of gravity, without necessarily being influenced by water or ice.
Nevertheless, water or ice may make mass movement even more catastrophic. Mass
movement classifications based on the material (mud, soil, earth, rock and
debris), or movement type (falls, topples, slides, lateral spreads and flows)1.
Water erosion is the removal of topsoil (up to 20 cm) due to the action of
water. It is divided into the following 3 types based on increasing severity: Sheet
erosion (water moves horizontally over a large area), rill erosion (small
incisions take place as the water begins to collect along parts of the land at
lower elevation) and gully erosion (entire sections of the soil can be washed
off)2.Wind erosionWind erosion occurs when strong winds blow over light-textured soils that
have been heavily grazed during periods of drought1.
Wind erosion has many impacts. Firstly, fertility is reduced since the majority of the plant
nutrients are concentrated on the soil that is blown away. This reduces the
soils capacity to support productive pastures and sustain biodiversity. Secondly,
it makes revegetation of the land difficult since there is a lack of nutritious
soil for the plants to be planted on. SalinitySalinity in agricultural terms is the excess of salts above the required plant
level. Most often it poses constrains in the growth and productivity of the
plants and, therefore, it is a serious concern. Mingling with other environmental
factors as precipitation, temperature, flooding, soil profile, water table
exaggerates the catastrophe2.
Chemical degradation Chemical degradation refers to the accumulation of toxic chemicals and chemical
processes which impact on chemical properties that regulates life processes in
? change in one or more of these soil chemical properties has a direct and
indirect adverse effect on the chemical fertility of soils. Chemically degraded
soils have the presence of large amounts of toxic chemicals interfering with
activities of soil life processes. These toxic chemicals may also interfere
with nutrient availability. Chemical soil degradation is hard to spot and thus
may be overlooked. Physical degradation Physical soil fertility is the ability of the soil to
enable the flow and storage of water and air into it,
to permit root growth and to anchor the plants. To be
fertile a soil needs abundant and interconnected pore space. Pore space refers to the volume of soil voids that can be filled by
water and/or air. Pore space generally depends on aggregates of soil particles
held together by soil organic matter. Unfortunately, intensive or inappropriate
tillage practices have been a major contributor to
land degradation. Soil tillage breaks down aggregates, decomposes soil organic
matter, breaks pore continuity and forms hard pans which restrict water and air
movement and root growth. On the soil surface, the powdered soil is more prone
to sealing, crusting and erosion. Improving soil
physical fertility involves reducing soil tillage to a minimum and increasing
soil organic matter. Biological degradation
Soil biological fertility refers to the quantity
and diversity of soil flora (all the plant life) and fauna (all the animal life) present in the soil4.
Biological activity is necessary to break down crop residues (roots, etc.) into humus (the organic component of soil). Soil fauna (including earthworms, termites, insects,
etc.) also transfer crop residues into the soil, increase soil porosity and
pore continuity, and can help break down compacted layers. That means that a
constant food source is necessary to maintain soil fauna and flora. A bare soil means low levels of biological
activity. Tillage (we mention many of its disadvantages in the physical
degradation) also disrupts the tunnels and habitat of organisms. The best way
to increase soil biological activity is to get as close as possible to a
natural system. That means, stop soil tillage and leave plant residues as mulch
on the surface.
are five main causes of land degradation1.
is taking place at a faster rate due to increasing demands of timber, fuel and
forest products which results into degradation of land resources.
refers to excessive eating of grasses and other green plants by cattle. It
results into reduced growth of vegetation, reduced diversity of plant species,
excessive growth of unwanted plant species, soil erosion, and degradation of
land due to cattle movement.
modern agricultural practices, excessive use of fertilizers and pesticides has
adversely degraded the natural quality and fertility of the cultivation land.