Casefile: Abandoned Australia

This post is the first in a series which will be looking at historical examples of societal collapse and the environmental factors that possibly drove them. This first casestudy is all about the collapse of Aboriginal settlements in Ancient Australia...

Background:
The study area is located in the region of Kimberly in North-Western Australia (see map below). The area is bordered by the Indian Ocean to the west, the Timor Sea to the north and the Great Sandy and Tanami deserts in the South.
Kimberly is thought to have been one of the first area settled by humans in the Late Pleistocene and it is believed that the early population were nomadic communities that arrived in boats from Timor and other Indonesian islands. Excavations of the site found evidence for human settlements in the form of cultural materials (artefacts, charcoal, paper bark, seeds, ochre), bone and rock art which indication that humans have inhabited Kimberly from around 40,000 yrs ago.

source: Bradshaw Foundation

Evidence:
Evidence for the collapse of the early Aboriginal inhabitants in Kimberly comes from rock art found in caves. These rock art paintings are the largest in the world and from them archaeologists were able to differentiate two different forms - the Gwion Gwion (or Bradshaw) paintings and the Wandjina rock art. The Gwion Gwion rock art has ‘fine featured human anthropomorphic figures’ whereas the Wandjina art is distinctive in that the paint strokes are much broader. Dates for both rock art were found by identify the species drawn and by using luminescence dating from mud wasp nests - the Gwion Gwion paintings have been dated to be present since 17,000 B.P. whereas the Wandjina art dates from 3800 B.P. As well as the Wandjina art being painted much later there is also evidence of a hiatus of rock art for a period of 1200 years, thus the change in style and dates for the rock art indicate that they were painted by another aboriginal community and that the Gwion Gwion painters society are thought to have declined whilst a new Aboriginal community resettled in the area later. Evidence for this new population comes from a rise of charcoal in the sediment record from farming.

Pollen and trace metals analysis of a sediment core from Black Springs showed that an increase in Pandus pollen and a decrease in ferns and aquatic plants were indicative of the environment becoming a dry swamp at 5750yrs B.P.. The landscape then alternated between a wetter (4600 yrs B.P) and drier environment (320 and 2750 yrs B.P.) with the Wandjina painters arriving at period (46000-3600 yrs B.P.) when the environment was wetter (Wandjina means rain spirit!) as the monsoon re-established itself.

 Sediment analysis also found that aeolian dusts from central Australia were deposited in the Kimberly sites that were most likely due to a change in wind patterns. And so sediment core analysis and depictions in the caves indicate that conflict over dwindling resources and changes in the environment are the cause for the decline of the early Aboriginal society.

The famous Kimberly Aboriginal rock art with the fine figured earlier Gwion Gwion rock art on the left and the broader Wandjina rock art that was painted later by a different community on the right.
source: Bradshaw Foundation

So what happened?:
Anti-cyclonic circulation was more dominant during the period of the hiatus in rock art and this meant: the monsoon was further north; that southeast trade winds re-established themselves over central Australia and were stronger, the dry south-east winds were more frequent over Kimberly and the region was much drier. These changes in wind and rain patterns were the effects of the mid-Holocene ENSO (don’t know what ENSO is? watch this clip here!) which caused the summer monsoon to fail and led to a mega-drought that lasted 1500 yrs and it is this sudden change of environment that led to the decline of the Gwion Gwion painters. These drought conditions were made even worse due to changes in the land surface and aerosol loading in the atmosphere which made the summer monsoon less active. Thus archaeological studies suggest that the population either operated at a lower intensity or probably abandoned the region as rainfall became less reliable and the environment arid. 

However, Kimberly was not the only region that experienced climatic changes as several archaeological studies in other Australian sites also show that the change in ENSO frequency and intensity placed environmental stress on other Aboriginal populations as well. Therefore, changes to the ENSO circulation exacerbated challenges in the local environment and made landscapes hard to adapt to causing societies around Australia decline.

Looking forward:

I thought this casestudy was interesting to look at in light of the ENSO event this year which is being ranked as one of the top three events in 50yrs. The ENSO this year (which hasn't reached its peak yet!) has had severe impacts on Australia including :causing extremely hot and dry conditions, increased fire and flood danger, record warm temperatures in the Indian ocean which has meant below average rain for Australia, a rise in Pacific ocean temperatures 2.4 ⁰C above average,  drought risk and a increase in daytime temperatures. These impacts are also predicted to affect the national economy  by reducing agricultural output and the income from agricultural production as well as the economic cost of dealing with excessive floods and fires.

However, Australia isn't he only nation that gets impacted by ENSO! ENSO causes a multitude of changes across the globe from: droughts, failing rice harvests and reduced water security in Indonesia; below average temperatures and rainfall in the USA; cyclones in the Pacific; forest fires in Borneo; the death of marine species  off the coast in California; water salinity issues in Vietnam and to colder weather in Europe. In fact the ENSO this year is predicted to cause a series of storms in the USA and can already be attributed to causing the hottest global temperatures seen this year, the forest fires in the Amazon and the deadly floods in Chennai.

Past ENSO events have severely disrupted livelihoods and has had environmental impact too. For example, the 1982-83 EL Nino weakened trade winds, caused sea level to rise, lead to the deaths of seals in Peru , caused malaria incidence to rise and led to economic losses of around $8 billion. EL Nino can also cause massive human disasters as a two year drought in China lead to starvation and the deaths of 9 million people. 

These impacts have been devastating to societies throughout history and the extreme events caused by ENSO could exacerbate the environmental stresses we feel today. Moreover, the uncertainty about the processes of El Nino and La Nina and the added threat of the unknown impact climate change will have on them may increases the risk to societies and their development. Thus studying the decline of the Gwion Gwion painters in ancient Kimberly and by bettering our understanding of the impact ENSO has on the environment and humans. This could place us in a better position to predict ENSO impacts and to be able mitigate against their negative effects on society so as to prevent any future collapse.