Geoscience Reference
In-Depth Information
25
environments
Interest in Mediterranean environments has always been
strong. The Mediterranean proper has been the scenario
for the classical civilizations of Greece and Rome, the Arab
and Ottoman empires, and the birth of the religions of
Judaism, Christianity and Islam. Since the 1960s the era
of mass travel has meant that millions of people from
northern Europe can now visit and appreciate its distinc-
tive landscape. In recent years many geography depart-
ments in northern Europe have used the Mediterranean
for teaching and research. Mediterranean parts of other
continents were settled from the seventeenth century
onwards. Climates defined as Mediterranean are found on
the western subtropical coasts of continents between
latitudes 30
where winter precipitation (
R
w
) is at least three times the
total amount of summer precipitation (
R
s
).
The total area of the world occupied by Mediterranean
environments is only about 2 M km
2
, about half of which
occurs in the Mediterranean itself: southern Europe,
North Africa, the Levant and the Mediterranean islands.
Although plant species differ between each of the five
main regions, evolutionary convergence has led in each
to vegetation dominated by evergreen woodland with
sclerophyllous trees and evergreen shrubs. In all Mediter-
ranean regions much of this woodland has been replaced
by agricultural land, originally for the traditional dry-
farmed crops of cereals and tree crops (e.g. the vine, olive,
carob, almond), but increasingly for high-value irrigated
land use (e.g. vegetables, citrus fruits, rice). Outside
the limits of farmland, human impacts on the natural
vegetation have been severe, mainly through grazing,
ranching, wood collection and deliberate firing. The native
woodland has therefore been replaced by dense scrub
(
maquis
in France;
monte bajo
in Spain) or aromatic heath
(
garrigue
in France;
matorral
in Spain). In California scrub
known as
chaparral
is common, whilst the term
matorral
is used in central Chile. In South Africa the shrubby
veld
contrasts with the heathy
fynbos
. In south-western and
southern Australia the term
mallee
is used for similar
vegetation formations.
Because of the difficulty of knowing how far vegeta-
tion has been influenced by human activities, it is difficult
to delimit the exact coverage of the Mediterranean
climate. The range of the domesticated olive (
Olea
europea
) is commonly used as a biological indicator for
the Mediterranean environment.
Figure 25.2
shows an
, namely in the Mediterranean region
proper, California, Chile, South Africa and south-western
and southern Australia (
Figure 25.1
).
Mediterranean environments are controlled by a
distinctive climatic regime of hot, dry summers and cool,
moist winters. This unique climate influences natural
processes (erosion, hydrology, soil formation, ecological
processes) and human activities (agriculture, forestry,
conservation, water abstraction). Under the Köppen
system of climatic classification, Mediterranean climates
are designated Cs, i.e. temperate with dry summers. A
third letter indicates temperature; thus 'a' designates the
warmest month above 22
C and 'b' the four coldest
months above 10
and 40
C. Mediterranean climates are thus Csa.
Köppen also defined the Mediterranean climate by the
equation:
R
w
3
R
s
