BACKGROUND :-
Only 30% of the planet's surface is land and only 11% of this
land surface is good agricultural land. It is estimated to take
over 3,000 years to form a good agricultural soil and yet we
will have destroyed over 30% of our good farmland by the year
2,000. This erosion is most severe where the land is misused
and the climate is extreme.
CAUSES :-
1. removal of the vegetation cover. This means that no further
humus is added to nourish the soil and there are no roots to
bind the soil together. If the surface is exposed to wind and
rain, the soil will be carried away leaving deep gullies or bare
rock e.g. the 'Dust Bowl" in the N. American Prairies.
If the slope is steep, the climate has dry periods or the rain
falls in heavy thunderstorms, then the effects of this are much
worse.
2. poor arable farming methods lead to soil damage.
Overcultivation, especially with one crop e.g. cotton in the
U.S.A., impoverishes the soil. With this, the soil is not allowed
time to 'rest' and restore itself naturally and eventually crops
can no longer grow in the soil and the bare soil is eroded..
Farmers find it easier to plough down a slope than across it.
When it rains, water flows down the furrows and washes away the
soil creating gullies.
Irrigation, the artificial application of water to the land,
can result in salinity (i.e. where salts are deposited in the
soil making it too salty [saline] to grow crops).
3. poor pastoral farming methods lead to soil damage. Sometimes, too many animals are kept in one area and they eat the vegetation until it becomes too short and dies off (this is called overgrazing). Wind and rain can then remove the bare soil.
4. urbanisation, highway construction and industry tend to consume vast areas of our most fertile farmland. Extractive (primary ) industry tends to be very destructive with quarries, mines and waste tips.
SOLUTIONS :-
1. to prevent erosion of bare soil, it is important to maintain a vegetation cover, especially in the most vulnerable areas e.g. those with steep slopes, a dry season or periods of very heavy rainfall. To do this may mean only partially harvesting forests (e.g. alternate trees) and using seasonally dry or wet areas for pastoral rather than arable agriculture.
2. where intensive cultivation takes place, farmers should
use a crop rotation in order to prevent the soil becoming exhausted.
Where soils are ploughed in vulnerable areas, contour ploughing
(i.e. round the hillside rather than down the hillside) should
be used.
Careful management of irrigation, to prevent the application
of too much or too little water, should help reduce the problem
of salination.
3. livestock grazing rates must be carefully managed to prevent overgrazing.
4. perhaps we must attempt to restrict highway construction and urbanisation to areas of lower agricultural potential. With extractive industries, a pledge must be secured to restore the land to its former condition before planning permission for quarries or mines is granted.
