Climate, Climate Variability and Impacts in the Mediterranean Area: An Overview
21
3.2 Pleistocene (1 Ma - 10 ka B.P.)
An overview of the climatic and vegetational development within the more recent
period of the Earth's history was presented by Yassoglou (1998, 2000) based upon
the work of Gilman and Thomes (1985), Verheye (1991), Tzedakis (1993), Runnels
(1995), Grove (1996) and the ARCHAEOMEDES Project (van der Leeuw 1998,
McGlade and van der Leeuw, 1998), A description of the succession of vegetation
phases is given by Wagner (2001) as well,
About 1 Ma ago the Aegean and the Adriatic Seas opened. The era of the
periodic glacials started during which fluvial terraces were formed from 300 ka B.P.
on. Southern Europe was covered during the cold stages of the Quaternary by open
Artemisia (mugwort) steppes with scattered forest stands, at least during 70% of the
last 2 Ma. From temperate forests which developed during warmer and wetter
periods the vegetation degraded to steppe forest, grassland steppe and finally desert
steppe during the cold periods. During the Wiirmian, as an example, the Epirus area
was arid and treeless except in favoured areas with a mosaic of grassland and open
vegetation, seasonally with a fair amount of bare ground, unstable slopes and poor
soil development. With the retreat of the glaciers and the advent of a wetter period
around 15 ka B.P. Pine-Juniperus forests appeared followed by oak forests and as
climate became wetter, 12.5 - 11 kaB.P., these forests expanded. Around 11000 B.P.
the first settlement in Jericho is dated. At that time there was enough water in the
Negev to support a larger population concentrated in one place without modern
technology (Bloch, 1970).
During the suddenly cooler upper Dryas period (10.5 ka B.P.) with its reduced
precipitation wind blown silt from Africa was deposited over wide areas of the
Mediterranean.
3.3 Early Holocene
The Juniperus-Pinus-Amygdalus (almond)-Pistacea forests and steppe mostly
survived the cold spell of the Dryas. After that phase wild olive trees appeared and
a rich vegetation developed at the time of the climate optimum around 8 ka B.P.
with oak, birch, hazel, elm, ash-tree, lime, pine (Quercus, Betula, Corylus, Ulmus,
Fraximus excelsior, Tilia, Abis).
The development at the end of the last glaciation is closely related to the
latitudinal position of the Westerlies. The subtropical high pressure belt is assumed
to be positioned until 10 000 years B.P. at approximately 21 ON in winter and 33°N
in summer. The subpolar low pressure system was at that time around 500 N with
small seasonal variations. About 9000 B.P. its winter position suddenly moved
northward. By the time of the optimum of the interglacial, about 9000 B.P., the
polar front had reached its extreme northern position at 80 0 N. The subtropical high
pressure system followed this development and reached its extreme northern position
at 41 ° N in winter respectively 47°N in summer around 5000 years B.P .. This is
21
3.2 Pleistocene (1 Ma - 10 ka B.P.)
An overview of the climatic and vegetational development within the more recent
period of the Earth's history was presented by Yassoglou (1998, 2000) based upon
the work of Gilman and Thomes (1985), Verheye (1991), Tzedakis (1993), Runnels
(1995), Grove (1996) and the ARCHAEOMEDES Project (van der Leeuw 1998,
McGlade and van der Leeuw, 1998), A description of the succession of vegetation
phases is given by Wagner (2001) as well,
About 1 Ma ago the Aegean and the Adriatic Seas opened. The era of the
periodic glacials started during which fluvial terraces were formed from 300 ka B.P.
on. Southern Europe was covered during the cold stages of the Quaternary by open
Artemisia (mugwort) steppes with scattered forest stands, at least during 70% of the
last 2 Ma. From temperate forests which developed during warmer and wetter
periods the vegetation degraded to steppe forest, grassland steppe and finally desert
steppe during the cold periods. During the Wiirmian, as an example, the Epirus area
was arid and treeless except in favoured areas with a mosaic of grassland and open
vegetation, seasonally with a fair amount of bare ground, unstable slopes and poor
soil development. With the retreat of the glaciers and the advent of a wetter period
around 15 ka B.P. Pine-Juniperus forests appeared followed by oak forests and as
climate became wetter, 12.5 - 11 kaB.P., these forests expanded. Around 11000 B.P.
the first settlement in Jericho is dated. At that time there was enough water in the
Negev to support a larger population concentrated in one place without modern
technology (Bloch, 1970).
During the suddenly cooler upper Dryas period (10.5 ka B.P.) with its reduced
precipitation wind blown silt from Africa was deposited over wide areas of the
Mediterranean.
3.3 Early Holocene
The Juniperus-Pinus-Amygdalus (almond)-Pistacea forests and steppe mostly
survived the cold spell of the Dryas. After that phase wild olive trees appeared and
a rich vegetation developed at the time of the climate optimum around 8 ka B.P.
with oak, birch, hazel, elm, ash-tree, lime, pine (Quercus, Betula, Corylus, Ulmus,
Fraximus excelsior, Tilia, Abis).
The development at the end of the last glaciation is closely related to the
latitudinal position of the Westerlies. The subtropical high pressure belt is assumed
to be positioned until 10 000 years B.P. at approximately 21 ON in winter and 33°N
in summer. The subpolar low pressure system was at that time around 500 N with
small seasonal variations. About 9000 B.P. its winter position suddenly moved
northward. By the time of the optimum of the interglacial, about 9000 B.P., the
polar front had reached its extreme northern position at 80 0 N. The subtropical high
pressure system followed this development and reached its extreme northern position
at 41 ° N in winter respectively 47°N in summer around 5000 years B.P .. This is