Physical Resources / 123Erosion by water may remove more than just the soil. If the land has been tilled, sown, and fertilized,
the seed and fertilizer may also be lost, possibly to the advantage of the next field downhill, but more
likely to the detriment of the water body into which it drains. Wind erosion may do even worse: it
may carry away young plants that have only just emerged and are not yet anchored by strong root
systems. The eroded soil also causes damage. It pollutes rivers, for example, and forms sediments in
reservoirs, reducing their capacity. Wind-blown soil particles can severely batter crop plants and the
soil can accumulate rapidly, sometimes to considerable depth, around fences and buildings, and may
cover roads.
It is somewhat scandalous that soil erosion should still be a problem of such magnitude. Ancient as
farming itself, its causes and remedies are very well known. It continues where they are not applied,
through ignorance, rural poverty, or indolence, or where farmers who could afford to implement
remedial measures perceive the cost to them as greater than their occasional loss.
30. Mining and processing of fuels
Originally, the word ‘fossil’ described anything dug up from below ground; zoologists still describe
burrowing animals as ‘fossorial’. Later, the word came to be applied to the preserved remains or
traces of organisms that lived long ago (technically, more than ten thousand years ago). What we call
‘fossil fuels’ warrant their name on both grounds, but it may be more informative to describe them as
‘carbonaceous’, or ‘carbon-based’ fuels, because their combustion represents the rapid oxidation to
carbon dioxide of the carbon they contain, which is an exothermic (heat-releasing) reaction.
Ordinarily, metabolic wastes and dead organisms are decomposed more or less rapidly. Most of the
organisms responsible for decomposition require oxygen for respiration, however, and in anoxic
environments their activities are curtailed. Under these circumstances it is possible for organic matter
to become trapped, compressed beneath the weight of material that continues to accumulate above it,
and subjected to rather different processes. Suitably airless environments are found, for example, in
seafloor muds and below the surface of bogs and some swamps.
Plant material buried below the surface of a bog may be compressed into peat. If, later, the bog partly
dries, the peat remains and can be dug for use as fuel. In some countries, such as Ireland, it is used
in electricity power stations. Peat is the first stage in the formation of coal, into which it is converted
by being subjected to much greater pressure and then heated: a 1 m seam of coal probably began as
a 12 m layer of peat. The conditions necessary for the formation of coal occur only in the swamps
found beside tropical rivers and seashores. Some of the coal being mined now formed around 400
Figure 3.16 Effect of a windbreak in reducing wind speed