Geoscience Reference
In-Depth Information
Horn of Africa. Other European countries - mainly the
British - had taken advantage of ENSO-related
droughts to expand their empires in Africa. However,
Emperor Menilek took advantage of his weakened
enemies to consolidate his position as the country's
absolute ruler. When the La Niña of 1892 brought rain
and harvests to feed his army, Menilek was able to
defeat the Italians at the Battle of Adowa and become
the first African ruler to repel colonialism in Africa.
Third is the effect of the 1982-1983 ENSO event on
Australia. This brought the worst drought Australia
has experienced. Approximately $A2000 million was
erased from the rural economic sector as sheep and
cattle stocks were decimated by the extreme aridity.
Wheat harvests in New South Wales and Victoria were,
respectively, 29 per cent and 16 per cent of the average
for the previous five years. The resulting lack of capital
expenditure in the rural sector deepened what was
already a severe recession, and drove farm machinery
companies such as International Harvester and
Massey Ferguson into near bankruptcy. By January
1983, dust storms in Victoria and New South Wales
had blown away thousands of tons of topsoil. Finally,
in the last stroke, the Ash Wednesday bushfires of
16 February 1983, now viewed as one of the greatest
natural
conflagrations
observed by humans, destroyed
another $A1000 million worth of property in South
Australia and Victoria. At the peak of the event,
Malcolm Fraser's Liberal-National Party coalition
government called a national election. The timing
could not have been worse, and the government of the
day was swept convincingly from power.
Other natural hazards are associated with the
Southern Oscillation. This is exemplified in Figure 2.11
for Australia between 1851 and 1980. (The index here is
part of the one used in Figure 2.8.) Shaded along this
index are the times when eastern Australia was either in
drought or experiencing abnormal rainfall. Sixty-eight
per cent of the strong or moderate ENSO events
between 1851 and 1974 produced major droughts in
eastern Australia. Sixty per cent of all recoveries after an
ENSO occurrence led to abnormal rainfall and floods.
Figure 2.11 also includes the number of tropical
cyclones in the Australian region between 1910 and
1980; the discharge into the Murray River of Victoria's
central north Campaspe River between 1887 and 1964;
beach change at Stanwell Park, south of Sydney,
between 1930 and 1980, described in Chapter 8; rainfall
this century at Helensburgh, south of Sydney; and the
Comparison of drought in Indonesia with El Niño-Southern
Oscillation events, 1844-1983 (Quinn et al., 1978).
Table 2.1
1844-96
1902-83
Drought
El Niño
Drought
El Niño
event
event
1844
1844
1902
1902
1845
1845-46
1905
1905
1850
1850
1913-14
1914
1853
none
1918-19
1918-19
1855
1855
1923
1923
1857
1857
1925-26
1925-26
1864
1864
1929
1929-30
1873
1873
1932
1932
1875
1875
1935
none
1877
1877-78
1940
1939-40
1881
1880
1941
1941
1883
none
1944
1943-44
1884-85
1884-85
1945-46
1946
1888
1887-89
1953
1953
1891
1891
no data
1954-55
1896
1896
1976
1976
1982-83
1982
fact. First is the effect of ENSO events on civilization
in Peru. The story is one of successive development
and collapse of city-states. By the end of the eleventh
century, most of Peru's desert coast had come under
the influence of the Chimu civilization. They devel-
oped a vast network of irrigation canals stretching
hundreds of kilometres between river valleys. Around
1100 AD, extraordinary flooding exceeding 18 m
depths wiped out all of their engineering achievements
in the Moche Valley. Rival city-states were also
affected; however the Chimu undertook military action
to expand their area of influence so that they could
relocate. While the rival states sank into revolt and
anarchy, the Chimu conquests succeeded to rival the
Incas in power. This example was but one phase in a
sequence of rapid cultural advancement, abandon-
ment, and expansion of opportunistic city-states trig-
gered by ENSO events along the west coast of South
America. Over four centuries, this process has covered
an area of 30 000 km
2
of coastal plain.
The second example is the historical development of
Ethiopia. The ENSO events of 1888 and 1891 killed
a third of this country's population at a time when
the Italians hoped to establish a colonial empire in the
