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Zurich
Elias Landolt
Fig. 1
Grossmünster (Photo Walter Lämmler, Zürich)
Elias Landolt (
*
)
Institut für Integrative Biologie (Swiss Federal Institute of Technology), ETH Zürich,
Universitätsstr. 16, CH-8092 Zürich, Switzerland
e-mail: landolt@env.ethz.ch
J.G. Kelcey and N. Müller (eds.),
Plants and Habitats of European Cities
,
DOI 10.1007/978-0-387-89684-7_16, © Springer Science+Business Media, LLC 2011
547
548
E. Landolt
Abstract
Zurich, which is the largest city in Switzerland, is situated to the north of
the Alps and at the northern end of Lake Zurich in an area with a rather cool sub-
oceanic climate. More than 1,400 indigenous or naturalised species of higher plants
have been recorded in the city, of which almost 200 (mainly archaeophytes) have
become extinct within the last 160 years. The extinctions were caused by habitat loss
resulting from the intensification of agricultural production and residential and other
forms of development. On the other hand 300 new species have been able to colonize
and become established in the city. The reasons for this being general climatic warm-
ing and the “heat-island effect” that is a characteristic of the urban environment. The
previously relatively cool summers prevented many species from achieving their life
cycle, which the recent warmer temperatures now allow them to. Also the milder win-
ters enable many species to survive in the city, over winter, particularly in sheltered
places. The absence of really cold winters for more than 20 years has enabled some
sub-tropical plants to survive throughout the winter and even set fruit and regenerate
from seeds, for example, the palm
Trachycarpus fortunei
.
Natural Environment
Zurich is situated in the north-eastern part of Switzerland at 47°23¢ north and 8°12¢
east. The administrative city area comprises about 88 km
2
(the Canton is much
larger), it is located in the Limmat Valley at the northern end of Lake Zurich
(Fig.
2
). The valley is the extension of the lake region to the north-west between the
mountain ranges of Albis to the south-west and Pfannenstil to the north-east, see
Fig.
3
. The surroundings of the city are known as the “Swiss Midlands”.
Fig. 2
City centre towards the south with the Lake Zurich; the Alps are in the background
Zurich
549
Fig. 3
Map of the city (from “Grün Stadt Zürich” after GEOZ, Zurich). Dark shading is forest;
the light shading is Lake Zurich. The area corresponds to the upper part of the distribution maps
The north-eastern part of the city lies in the Glatt valley. The lowest part of
Zurich is 390 m a.s.l. (in the Limmat valley), the highest point is 870 m a.s.l. on
Mount Uto to the west (Fig.
4
). Most of the city has been built between 400 m a.s.l.
and 600 m a.s.l. The hills are mainly forested (Fig.
5
), while most of the sealed
surfaces occur in the flat part of the valley (Fig.
6
). The percentage of forest
and sealing are negatively correlated; within the administrative city area, the
forest occupies 24% and the sealed part 18%. Fifty-two percent of the area is
covered by fields, meadows and gardens. The height of the mountains gradually
increases southwards until about 60 km from the city; they reach an altitude
of about 3,000 m a.s.l.; on clear days, the mountains of the Alps can be seen
from the city.
The solid geology north of the Alps comprises sedimentary rocks and
deposits from the Tertiary and Quaternary Periods. The mountain ranges
comprise mostly horizontal layers of sandstone, marl and conglomerates.
550
E. Landolt
Fig. 4
Altitudinal differences of the map squares within the city limits and in a narrow strip about
10 km outside and to the south of the city (estimated from topographical maps)
During the Ice Ages, glaciers left extensive moraines on which most of the city has
been built. In the valleys, sand and gravel deposits of the rivers predominate.
The main soils in the surroundings of the city are clayey young brown earths,
which are rich in nutrients and slightly acidic in the upper layers. Within the city,
virtually all of the soils have been substantially disturbed by millennia of human
activity.
The general climate is sub-oceanic, the mean annual temperature is 7–9°C
(January −1 to +1°C, July 17–19°C); the mean annual precipitation is 100–130 cm.
The high precipitation is characteristic of the mountains on the southern side of the
city, whereas the lower parts of the north are slightly drier and the climate is more
continental, see Fig.
7
.
Zurich
551
Fig. 5
Forest cover (%) within the city limits and in a narrow strip about 10 km outside and to
the south of the city (estimated from topographical maps)
Historical Development
After the retreat of glaciers 15,000 years ago, the area now occupied by the city was colo-
nised by hunter-gatherers and fishermen. About 6,000–7,000 years ago, people estab-
lished permanent settlements along the lakeside, mainly houses on stilts. They began to
clear the forests to provide grazing land for domesticated animals and to cultivate around
their houses for the growing of cereals and other edible plants. However, their main food
was fish from the rivers and the lake. Gradually, people spread from the lakeside into the
surrounding areas and occasionally traded with other people as far south as the
Mediterranean. It was during these times that many cultivated plants and the first weeds
were introduced into this part of what is now Switzerland. In 1000 BC, the settlement
was inhabited by the Helvetians, a Celtic tribe who called it Turus.
zanotowane.pl doc.pisz.pl pdf.pisz.pl hannaeva.xlx.pl
Elias Landolt
Fig. 1
Grossmünster (Photo Walter Lämmler, Zürich)
Elias Landolt (
*
)
Institut für Integrative Biologie (Swiss Federal Institute of Technology), ETH Zürich,
Universitätsstr. 16, CH-8092 Zürich, Switzerland
e-mail: landolt@env.ethz.ch
J.G. Kelcey and N. Müller (eds.),
Plants and Habitats of European Cities
,
DOI 10.1007/978-0-387-89684-7_16, © Springer Science+Business Media, LLC 2011
547
548
E. Landolt
Abstract
Zurich, which is the largest city in Switzerland, is situated to the north of
the Alps and at the northern end of Lake Zurich in an area with a rather cool sub-
oceanic climate. More than 1,400 indigenous or naturalised species of higher plants
have been recorded in the city, of which almost 200 (mainly archaeophytes) have
become extinct within the last 160 years. The extinctions were caused by habitat loss
resulting from the intensification of agricultural production and residential and other
forms of development. On the other hand 300 new species have been able to colonize
and become established in the city. The reasons for this being general climatic warm-
ing and the “heat-island effect” that is a characteristic of the urban environment. The
previously relatively cool summers prevented many species from achieving their life
cycle, which the recent warmer temperatures now allow them to. Also the milder win-
ters enable many species to survive in the city, over winter, particularly in sheltered
places. The absence of really cold winters for more than 20 years has enabled some
sub-tropical plants to survive throughout the winter and even set fruit and regenerate
from seeds, for example, the palm
Trachycarpus fortunei
.
Natural Environment
Zurich is situated in the north-eastern part of Switzerland at 47°23¢ north and 8°12¢
east. The administrative city area comprises about 88 km
2
(the Canton is much
larger), it is located in the Limmat Valley at the northern end of Lake Zurich
(Fig.
2
). The valley is the extension of the lake region to the north-west between the
mountain ranges of Albis to the south-west and Pfannenstil to the north-east, see
Fig.
3
. The surroundings of the city are known as the “Swiss Midlands”.
Fig. 2
City centre towards the south with the Lake Zurich; the Alps are in the background
Zurich
549
Fig. 3
Map of the city (from “Grün Stadt Zürich” after GEOZ, Zurich). Dark shading is forest;
the light shading is Lake Zurich. The area corresponds to the upper part of the distribution maps
The north-eastern part of the city lies in the Glatt valley. The lowest part of
Zurich is 390 m a.s.l. (in the Limmat valley), the highest point is 870 m a.s.l. on
Mount Uto to the west (Fig.
4
). Most of the city has been built between 400 m a.s.l.
and 600 m a.s.l. The hills are mainly forested (Fig.
5
), while most of the sealed
surfaces occur in the flat part of the valley (Fig.
6
). The percentage of forest
and sealing are negatively correlated; within the administrative city area, the
forest occupies 24% and the sealed part 18%. Fifty-two percent of the area is
covered by fields, meadows and gardens. The height of the mountains gradually
increases southwards until about 60 km from the city; they reach an altitude
of about 3,000 m a.s.l.; on clear days, the mountains of the Alps can be seen
from the city.
The solid geology north of the Alps comprises sedimentary rocks and
deposits from the Tertiary and Quaternary Periods. The mountain ranges
comprise mostly horizontal layers of sandstone, marl and conglomerates.
550
E. Landolt
Fig. 4
Altitudinal differences of the map squares within the city limits and in a narrow strip about
10 km outside and to the south of the city (estimated from topographical maps)
During the Ice Ages, glaciers left extensive moraines on which most of the city has
been built. In the valleys, sand and gravel deposits of the rivers predominate.
The main soils in the surroundings of the city are clayey young brown earths,
which are rich in nutrients and slightly acidic in the upper layers. Within the city,
virtually all of the soils have been substantially disturbed by millennia of human
activity.
The general climate is sub-oceanic, the mean annual temperature is 7–9°C
(January −1 to +1°C, July 17–19°C); the mean annual precipitation is 100–130 cm.
The high precipitation is characteristic of the mountains on the southern side of the
city, whereas the lower parts of the north are slightly drier and the climate is more
continental, see Fig.
7
.
Zurich
551
Fig. 5
Forest cover (%) within the city limits and in a narrow strip about 10 km outside and to
the south of the city (estimated from topographical maps)
Historical Development
After the retreat of glaciers 15,000 years ago, the area now occupied by the city was colo-
nised by hunter-gatherers and fishermen. About 6,000–7,000 years ago, people estab-
lished permanent settlements along the lakeside, mainly houses on stilts. They began to
clear the forests to provide grazing land for domesticated animals and to cultivate around
their houses for the growing of cereals and other edible plants. However, their main food
was fish from the rivers and the lake. Gradually, people spread from the lakeside into the
surrounding areas and occasionally traded with other people as far south as the
Mediterranean. It was during these times that many cultivated plants and the first weeds
were introduced into this part of what is now Switzerland. In 1000 BC, the settlement
was inhabited by the Helvetians, a Celtic tribe who called it Turus.