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Greenhouse
effect and desertification
A.Giommi, S.
Sciascia - 2 ° A, ITI G. Galilei - translated by Linguistic
high school Deledda
In the last congress
in Kyoto the greenhouse effect and desertification were discussed very
much.
GREENHOUSE
EFFECT
The greenhouse effect has always existed, but these last years the scientists
have placed it more and more in evidence.
The earth receives warmth from the sun and disperses it in the atmosphere,
but the rays reflected upward are stopped by the gases which perform
the some role of a greenhouse-wall, adding to the planet's temperature.
CAUSES
The atmosphere that surrounds the earth is a fundamental part of our
planet, invaluable for keeping life. Its chemical composition varies
with altitude and the gases present in the various strata, in different
percentages and sometimes just in traces, interfer deeply in Earth-Sun
relations, playing a key role in regulating the weather.
Carbon dioxide in particular makes up a sort of "blanket"
of gas which keeps the earth warm as respects the various middle constant
values.
Just as it happens in a greenhouse where the function carbon dioxide
performs in the atmosphere is played by glass-rafters, the sun's energy
arrives down at the earth, where it is partially absorbed and partially
reflected. Such reflected heat, however, is reflected again, by glass
as for the greenhouse, by carbon dioxide as for the atmosphere, down
on earth: it is as if a part of the heat were entrapped, thus determining
a growth of temperature on the ground.
The presence of carbon dioxide in the atmosphere, up to a certain concentration,
allows, then, for the maintenance of today's climate, while its excessive
growth brings in a progressive growth of temperature on the planet as
well.
The human activities which contribute in a dramatic way to the growth
of the atmosphere's carbon dioxide are chiefly two.
On the one hand the oxidation of carbon compounds which make up the
fossil fuels (charcoal, petrol and gases burned to get heat and energy:
discards of vehicles, radiator-systems and carbon-working industries
producing electric power, etc…) to which we add also the effects
of forest-fires. On the other hand, the massive tree-felling that determines
a dramatic reduction of the absorbing process of carbon and of the immission
of oxygen on the part of plants through the photosynthesis. From the
time of the industrial revolution up to our day there has been a fast
growth of carbon world production. It is estimated that the total quantity
of carbon present in the atmosphere is 700 milliards of tons, 85 milliards
of tons of which thrown out during the last two centuries. If today's
trend of needless consuming of fossil resources, not renewable, will
go on unchanged, the quantity of carbon dioxide present in out atmosphere
will double within about 50 years.
On the other side, every minute, 40 hectares of tropical forest disappear
from the earth by man's action, every day 50 thousand hectares of trees
are cut off; every year about 15 million hectares of green grass are
definitely destroyed. The search for new cultivating fields or to be
employed for pasture and production of hamburgers for rich lands, within
the short term of a human life (c. 80 years), will wipe off the earth
the tropical forests; in Amazonia, in Mexico and in Central America,
where 2/3 of the existing forests have already been cut down, it is
supposed that in twenty years we could get to their final destruction.
We should not anyway forget that even Italy was once thickly covered
with trees, before the industrial revolution, by the wood-drawn charcoal,
as chief energetic resource, took to destruction most of Umbria's, Sardinia's,
Puglia Plateau's and Calabria's woods. Finally, European forests undergo
also the attacks on the part of acid rains, which we will discuss later,
and the Italian ones fall short each year because of fires, often actual
arsons ever related to the bad care granted to the forest-ensemble.
The installing of high-precision devices at Mauna Loa on the Hawaii
Islands, and in U.S. bases in the Antarctica, has permitted to register
with unmisunderstandable exactness the fast growth of the degree of
atmosphere's carbon dioxide in these latter decades, to which a lowly
growth in earth's temperature (about half a degree) corresponds.
But if, as it was predicted, the quantity of carbon dioxide present
in earth's atmosphere actually doubles within the next 50 years, it
is estimated an average growth in temperature of c. 3 degrees, with
circa one and a half degree variation. Comparatively, North Pole's temperature
would grow of 7-8 degrees.
It has been calculated that suchlike variations in temperature would
be very similar to those which divide the major geologic eras, and that
these might cause heavy environmental and biological changes, similar
to the ones occurred in those periods. This time, however, the very
changes that occurred by the slow flowing of eras, would be performed
within few decades: as if the geologic time were quickened, giving birth
to a fast and maybe harmful physico-chemical and biological evolution
of the earth.
We can thus state with B. Bolin, one of the greatest world experts in
weather problems, that "man has started, without realizing it,
a type of global climate and geologic experiment which can easily slip
out of any control". The sorcerer-apprentice makes experiments
on himself, without knowing what the consequences will be and how to
control them.
ENVIRONMENTAL
DAMAGE
A raising in temperature, even of a few degrees, could cause the partial
liquefying of eternal ices and, consequently, a raising of the sea-level
with flooding of cities on the coast or placed on low zones, and of
agricultural plateaus. London, Bangkok, New York, Tokyo, Alexandria
in Egypt, Amsterdam or Venice would risk to be flooded by the tide and
a similar fate would be met by entire lands, such as Bangladesh or the
Netherlands.
The monsonic systems and rain-level could change, making dry territories
which now are very fertile, such as rice-plantations in Asia or the
Pianura Padana itself. Middle regions would disappear and great summer
droughts would appear; desertification processes would get quicker in
the half-dry zones of the world and their extension also to Southern
Europe, a trend already realizable in Spain and Southern Italy. The
regions next to deserts and Third World-countries with a badly-working
agriculture would be the zones most hurt by a form of pollution coming
mostly from richer lands of the world. Agriculturally valid fields,
if the process goes on, will progressively become the ones in zones
nearer and nearer to the Poles: the south of the Northern Hemisphere,
the lands of the Tropical Belt and the ones of the Third World in general
will pay for the industrial activities and for the crazy consuming of
energy on the part of the industrialized lands; the production of food
needed to support the growing world populace might diminish.
Remedies
To do a way with the risks of the greenhouse effect and guarantee still
for many centuries the survival on this planet, we need a decisive and
orderly action on the part of all the world's governments as regards
energy.
On one hand it is necessary to fix precise limits to unresponsible demographic
growth, for example through the energetic saving: introduction of more
efficient devices (long-lasting bulbs, high-level house devices, low-consuming
vehicles, etc…); strengthening of public transport; stocks transported
by ironway etc…
On the other hand it is necessary to impose also a quick transaction
from fossil and non-renewable energetic sources (which produce dangerous
discards) to renewable and clean sources, such as the direct use of
sun's energy and from wind, water, ground, tides and biologic discards.
Further, a decisive part might be played by the adoption, on the part
of the industrialized States and not yet industrialized ones, of a strict
anti-pollution bill (veto in using pollution fuels, imposed adoption
of the filtering silencer on cars, traffic stop in downtowns etc…)
accompanied by the massive introduction of the so called ecologic taxes,
adopted to discourage the consuming of energetic sources, fossil and
non-renewable and to make those who pollute pay for the damage caused
by pollution itself to the community.
Finally, it is more than necessary the adoption of very strict tutorship
actions on forests all over the world.
Desertification
Desertification is a phenomenon of soil-degrade in dry, semi-dry and
sub-humid zones, resulting from various factors, including weather changes
and human activities. It is a process of progressive reduction of the
ability of natural systems to support animal and vegetal life. In a
few words desertification is the process of progressive drying-out of
a region.
The term "desertification" was used for the first time in
reference to the degrading zones in tropical Africa, in the 50s of the
20th century.
Desertification has been one of the first ruining phenomena ( a worldwide
one ) that was acknowledged, and the formal process of this acknowledgment
has occurred at the Desertification Congress of the UNO, held in Nairobi
in 1977.
From 1984, the year of its foundation, the United Nations Environmental
Program has furthered and coordinated various initiatives to stop the
growing problem.
Mistakes made by the humans in managing the natural resources can open
the way to degrading processes which within vary few years would bring
to soil destruction.
The excessive exploitation of pasture grounds is one of the chief causes
of desertification: when the number of herds is superior to that which
the pasture ground can support, the soil degrade begins.
Quickly, yearly species and unwanted bushes for herds substitute themselves
to ever-remaining vegetal species; afterwards herbal kinds diminish,
the animals' downtreading does away with the bit which remains and the
soil is uncovered to be eroding action of winds and water. Almost likewise,
the excessive exploitation of agricultural grounds brings to a progressive
impoverishing of grounds, that, once exhausted their own reservation
of substances, stay exposed to atmospherical agents and, as a consequence
start to get eroded. The desertification process can be started also
by the needless downcutting of forests or the bad management of watering
systems, which, in many regions, is a cause for the development of salt
in soil.
The forest-downcutting performed by local populace to create spaces
to reserve for agriculture and shepherding, and above all to get wood
to burn (a practice which includes many dry regions of developing countries)
is one of the primary causes of desertification of vast areas. The case
of Sahel is particularly dramatic: the region most stricken by this
phenomenon where the tree-cutting in the urban inland, due to the need
to satisfy the demand of wood to burn, has brought to the almost complete
disappearance of trees around the most important towns.
The extent to which man's intervention on the environment is responsible
for the desertification of some regions results evident if we consider
a phenomenon such as the development of salt in soil, a calamity caused
by the bad management of watering systems.
It is not easy to be able to distinguish the effects produced on the
environment by the bad management of resources and by human activities,
from the ones deriving from the natural process of transformation of
the ecosystems. The place of deserts and nearby territories is naturally
subject to changes related to rains ( which often are unsteady and may
vary from day to day or season to season ) and to the lengths of drought
periods ( which often last decades ).
In the case of Sahel, for example, it is not easy to establish to which
extent the long period of drought that has stricken the region from
the 60s has contributed to the disappearance of vegetation and the soil
degrade.
The actions to seek to stop the phenomenon are often inadequate and
based on a mistaken interpretation of the forms in which the problem
displays itself.
In the general opinion, the phenomenon is often associated with the
idea of sandy scenarioes which move ahead, devouring green fertile areas.
Actually, the soil "sterilization" regards also highly watered
areas or the ones placed at latitudes very far from the wilderness regions.
For example, 33% of Europe's surface is threatened by desertification.
Some initiatives have anyway effectively contributed to "brake"
the process of desertification: in some countries, placed at margins
of Sahara, there have been implanted "vegetal belts" made
up of throngs of particularly resistant trees, and in Sahel such a practice
has permitted to snatch out of desertification 620 hectares of soil
( 60 of which have even been recovered by agriculture ) and to save
some villages which would otherwise have disappeared. The solutions
more recently adopted differ basically from some old ideas.
In particular the trend is to esteem better hypotheses of work studied
fittingly for a certain territory, giving greater importance to the
involvement of local communities, to the recovering of precious traditional
practices and to the reesteeming of the role of rural communities to
avoid territory degrade. Further, while in the past the trend was to
look for more technical solutions, the trend today is to face the whole
problem, due also to the continuous demographic grows, as well as to
factors of practical and socio-economical nature.
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