Does Holocene climate change cause societal collapse

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Does Holocene climate change cause societal
collapse?

• When climate attacks

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The Akkadian Empire

• Ruled Mesopotamia during 3rd millenium BC
• Dependant on agriculture
• Sargon of Akkad created worlds first united
  empire
• Northern Mesopotamian plains very fertile
  rainfall fed
• Collapsed abruptly 4170150 cal yr BP

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Tel Leilan

• 1 of 3 major cities, primary cereal producer
• Immediately above collapse horizon 0.5cm layer
  of volcanic ash overlain by 100cm layer of well
  sorted wind blown silts barren of all signs of
  life.
• Indicates extreme aridity
• Re-inhabited 300 years later
• But could just be local phenomenon

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Cullen et al that dust

• Satellite imagery shows dust flux of 100x106tons
  per year to Persian gulf Gulf of Oman
• Dust characteristically high concentrations of
  detrital dolomite, calcite quartz
• During last dry periods at LGM YD 50 of
  calcite content in Gulf of Oman was from fin
  silt sized detrital carbonate eolian dust
• Found dramatic increase in dolomite and calcite
  between 4025 3625 yrBP

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Death Stalks the Land

• 4025150 yr BP event lasted for a few centuries,
  uncommonly large amplitude for Holocene, nearly
  matched amplitudes for Younger Dryas
  aridification
• Lake Van Turkey level fell 30-60m around 4190BP
  Dead Sea level fell abruptly
• Cave Deposits in Israel show 20-30 decrease in
  precipitation between 2200-2150BC
• Possibly caused collapse of Egyptian Old Kingdom-
  affected Nile flooding Dry is the river of
  Egypt, and one can cross it by foot

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Why?

• Later material described how the fall of Akkad
  was due to Naram-Sin's attack upon the city of
  Nippur. The king sacked the E-kur temple,
  supposedly protected by the god Enlil. As a
  result of this, eight chief deities were supposed
  to have withdrawn their support from Akkad.
• For the first time since cities were built and
  founded, the great agricultural tracts produced
  no grain, the inundated tracts produced no fish,
  the irrigated orchards produced neither syrup nor
  wine, the gathered clouds did not rain, the
  masgurum did not grow. At that time, one shekel's
  worth of oil was only one-half quart, One
  shekel's worth of grain was only one-half quart.
  . . .These sold at such prices in the markets of
  all the cities! He who slept on the roof, died on
  the roof, he who slept in the house, had no
  burial, people were flailing at themselves from
  hunger.

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Classical Maya

• Noted for its spectacular art, monumental
  architecture, and sophisticated mathematical and
  astronomical systems.
• Classic period 250-900AD

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Loss of Faith

• Looks like most cities were just abandoned, no
  evidence of violence or famine (ie no corpses
  lying in street)
• Archaeologists put down to a loss of faith in
  their kings and society
• Kings derived power from faith of masses, had to
  undergo ritual bloodletting of the tongue and
  genitals as an offering to the Gods so that the
  sun would keep rising and the rains keep falling

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Chichancanab- little sea

• Hodell et al looked at sediments of Lake
  Chichancanab
• Today rainy season May-September dry
  October-April d18O of lake heavier than rainwater
  evaporation
• Assumed high evaporation/precipitation?? d18O
  ?gypsum/calcite
• Low E/P ? ? d18O ?gypsum/calcite
• Found driest conditions 1300-1100BP (800-1000AD)
• Classic Maya collapse 700-900AD

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Survival in the north

• Only the southern central lowland cities were
  abandoned while northern cities thrived
• Water table very deep in south so relied on rain
  water, but in northern Yucatan much shallower and
  had access through cenotes

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Why??

• from Hodell et al 2001