More on ENSO

After discussing ENSO as the primary cause for the Aboriginal decline in Kimberly in an earlier blogpost I kept seeing new articles popping up about the devastating impacts this 2015 ENSO was having across the world.

What I did not realise however was that the ENSO was having such a massive affect on so many countries including the UK! I came upon this Buzzfeed article describing how El Nino is the cause of some of this horrid weather we've been having. Okay so I know it's hard to distinguish between the different rubbish weather we've been getting but this winter has been one of the wettest and this year has also been one of the warmest. This is the result of both ENSO and climate change. An El Nino event causing warming of the equatorial waters of the Pacific which in turn warms the atmosphere driving global weather. The El Nino has led to warm and wet conditions in the North which has resulted in the severe floods we've seen in Britain this winter, and its predicted to do the in 2016. 

The floods in Leeds (Source:The Guardian)

Moreover with rising temperatures due to climate change and future ENSO events the frequency and intensity of storms are expected to increase with unprecedented impacts on societies. This will not only affect the UK but nations around the globe too and whilst there are already worries on the UK's flood defences just imagine the impacts in densely populated developing countries!

ENSO is also predicted to cause environmental damage as this articles suggest record temperatures will cause serious fires in the Amazon which may devastate the local ecology and lead to more carbon being released into the atmosphere. 

Thus like the the situation in Kimberley, climate change coupled with a strong and slightly unpredictable ENSO may have serious consequences on societies across the globe if preventative methods are not taken. Nevertheless, continual monitoring and possible warning systems may help nations be better prepared to deal with future climatic stress.

Merry Christmas!!

Just a little present to spread the Christmas cheer! Click here for some special climate change carols we'll all be singing in a few year (yay?!)....

source: Gareth's World

Casefile: Aridity in Akkad

Background:

The Akkadian empire was ruled from the ancient city of Akkad (location unknown) and commanded Mesopotamia from the Tigris-Euphrates river to the Persian Gulf. It was built by King Sargon who ruled from 2334 to 2279 BC and was the first to command a 'multi-national empire'. The great king is said to have ruled an area that ran all the way from the Persian Gulf through to Cyprus with his military and the empire is believed to have had 5 kings.

His empire was prosperous as seen by the development of roads, trade, farming including irrigation, religion, the arts and sciences. However, this empire wasn't to last as once it reached a peak in 22nd century it decline by 2154 lasting only 180 yrs. 

Map of Akkadian empire (Source: Ancient History Encyclopaedia)

Theories:

One theory is that he empire became weaker and experienced regional declines with the reign of Shar-Kali-Sharri. Anarchy ensued (2192-2168 BC) until its collapse as invaders from the Zagros Mountians took over. These invaders - the Gutians- are thought to be the cause of the Akkadian decline as they did not maintain the empire and a collapse in trade and famine meant the population retreated to the city before disappearing. 

However, another theory is that the region became more arid and this lead to the failure crops and famine. It is thought a global drought that lasted a century is also to blame as precipitation fell causing the region to become more water scarce than it was previously. H. Weiss (1993) stated that sediment data illustrated a rise in aridity and changes to wind patterns in 2200 BC. These climatic changes occurred beyond the Akkadian empire and that the North Atlantic Oscillation changed the flow of the Tigris and Euphrates river further exacerbating problems. Another sediment record from a nearby ocean basin found several pieces of evidence for the major 4200 BP drought event that took place. This included a rise in aeolian dust from Mesopotamia and tephra shards which link the drought event and rising aridity to the societal collapse that occurred in Akkad. This event is thought to have also been the cause for the collapse of the Old Kingdom in Ancient Egypt. 

The city Tell Lilan in Mesopotamia was also abandoned and had no signs of settlement after its construction. Sediment samples from the region also indicate an arid environment and other evidence suggest that livestock had died, that around 28000 people left and the city shrank as people moved to wetter regions. 

Rain- fed farming also collapsed and the water level in rivers fell which placed water stress on local populations which my have in turn led to conflicts. Eventually it is thought that the Akkadians split into to two different states Assyria and Babylonia. 

In this example it seems the obvious cause of societal collapse was the increasingly drier conditions and the devastating 4200 BP event. This placed enormous stress on the society, led to conflict over dwindling resources and the displacement of regional populations. In the near future climate change, increasing soil erosion and desertification may cause regions to become arid and unable to support local people. However, I believe that this would not occur today as advances in technology (e.g. GM crops that are adapted to growing in dry conditions) and global aid may help nations in a similar situation thereby preventing them from having conflicts that lead to collapse like that which occurred in Akkad. What do you think? Do you reckon a a similar event could lead to a collapse in society today? Comment below... 

(Source: ZME Science)

Casefile:Mystery of the Ancient Indus Civillization

Background:

This casestudy takes us to Ancient India and one of the earliest urban civilizations in the world - the Harappans. Whilst the origins of the society is debated the Harappan society is thought to have existed from around 3300 to 1300 BC in three phases (early, mature and late) and to have spread to cover a vast area (Fig 1) which included parts of both Pakistan and India.

Fig. 1 The Harappan civilization covered a large geographical area from as far as Saurashtra and the Ganges- Jumna Doab. The settlement was bordered by the Himalayas in the North, the Arabian sea in the South and by Baluchistan in the West. However, it is debated whether these areas were inhabited at the same time or sequentially. (Source: Kings Academy)

The ancient city was first discovered accidently by the British in the mid 19th century and further excavations revealed a highly sophisticated society. Evidence of this complex society was found in the form of: pottery, ornaments, weaponry, bronze, clay figurines, uniform bricks, technologically advanced crafted jewels and seals with inscriptions, early depictions of gods and animals motifs (Fig 3). The settlement itself also suggested a highly developed society as it had a high degree of urban planning (Fig 2) with separated private and public area, houses with their own latrines, drinking wells, bathing houses, a waste removal system, a sewage system that provided nearby agricultural farms with fertilizer and the streets were built in a grid patterns with buildings facing specific directions.

Archaeologists have also inferred that the Harappans were a successful civilization from crafted artefacts and Harappan seals that were found in places such as Mesopotamia and Oman, the result of trading that must have occurred between these cities. The Harappans most likely traded in livestock, agricultural produce, jewels, honey, raw materials and crafted ornaments such as ivory beads. It is thought that a ruling elite may have controlled a widespread trade network and that they ruled with religion as opposed to with military as no Harappan art glorified warfare and, unlike other urban cities during this period there was evidence of different classes and occupations. Radio carbon dating showed that due to trade and advanced craft technology the civilisation experienced a peak in urban growth and as a result was a major economic centre in 26-1900 BC with new settlements emerging in surrounding areas. The high craftsmanship of the Harappans and the fact that the city systems and material wealth were found across these sites suggests a regularity of the civilization spatially and temporally.  

However, as still little is known about the Harappan Civilization- including its exact origins, its un-deciphered script and sudden disappearance- the ancient city has become something of a mystery and of great interest to archaeologists.

Fig 2. Mohenjo-Daro a city complex of the Harappan Civilization (Source: National Geographic)

The Decline: 

The Harappans are thought to have started declining in 1800BC with the main cities being completely abandoned by 1500BC. This decline was due to the Harappans moving away from their cities to become mixed with nearby villages and less developed cultures until the 'Harappan culture' effectively became extinct. So how did this great civilization decline? Two theories have been put forth as the possible causes for the reduced density and number of sites of the Harappans– conflict and natural disasters…

Theory 1 - Attack of the Aryans!

One popular theory that emerged is that the Harappan cities were invaded by hill raiders or (more commonly) the Aryans. This theory was presented by Wheeler in 1953 who had inferred an attack from finding 37 skeletons that date to the Indus Civilization at the sites and had previous knowledge that around 1500BC the Aryans were conquering other cities. However this theory is now widely discredited as no site indicated damage from an attack and the belief that if the Aryans had invaded they would have enforced their own belief system - when in reality the continuation of the Harappans’ religion, technology and societal organisation indicates that a conquest did not occur. Moreover, other studies suggest a gap between the end of the Harappans and the arrival of the Aryans. 

On another hand, Kenoyer believes that the decline of the city was due to a rising population which caused stresses being placed on dwindling water sources, the economy and political strife. This meant societal organisation became harder for the ruling elite which led to a drastic change in society. However, this was in part due to changes in water supply and so the environmental changes offer a more probable primary explanation for the Harappans' decline.

Theory 2 – A Natural Disaster!

The more plausible theory on the Indus collapse is that a change in environmental conditions put pressure on society which eventually led to people moving away to the countryside and into areas such as Gujarat, Punjab and Uttar Pradesh whilst the old Harappan settlements became ghost towns. Archaeologists believe that changes to water supply are to blame- although it should be noted that as the region regularly experienced floods (seen by silt deposits) they had built embankments and foundations that were higher than the water level which provided them with a degree of resilience. Nonetheless, 2 different authors give their views on what may have occurred:

1. G.F. Dales (1966) states that the Harappan collapse is the result of floods. Whilst he acknowledges that silt deposits and slumping brinks indicate that the city is used to dealing with floods he argues that the regular overflow from the river was on a much larger scale and this was the source of the city’s demise. Tectonic activity (seen by faulting in rocks) induced an upheaval in Sehwan which altered the Indus River's flow as a build up of mud blocked the rivers path to the sea and instead made water fill up in a reservoir. This would have flooded settlements as, despite the protective measures built, water may have overflowed from the reservoir’s natural dam. Moreover, this flooding is thought to have been periodic and occurred at least 5 times and so as the Harappans rebuilt foundations over sinking and decaying soil their resilience to flooding fell. Thus after the 3^rd phase of Harappan society there came a squatter phase where the city degenerated from one with highly technical architecture and artefacts to one with simple pottery, plain seals and broken brick housing. The population eventually left the area to Gujarat as the devastation from sequential flooding meant a lower quality of life for the Harappans.

2.  L.Giosan et al (2011) found that the civilisation grew and prospered in 4500BC when a stable period in the late Holocene meant Himalayan rivers stopped incising and reduced sediment deposition downstream. This in turn reduced the intensity of floods and allowed the Harappans to intensively farm land and increase output. However, during a weaker monsoon rivers ran dry as monsoonal rivers were no longer active and land became more arid. This placed food insecurity on the Harappans as farming practices failed and output could on longer sustain the growing urban settlement. Food and water stresses made the civilization scale down and move away. Evidence for these changes correlate with the rise in settlements in regions where a moist monsoon was occurring (e.g. Haryana, Punjab) and forced farmers to diversify their crops.

So what caused these environmental shifts?

Other than the possibility of tectonics as discussed in Dales’ article, changes to the Pacific Ocean and solar variability may be to blame.

The summer Indian monsoon was vital for the Harappans as they provided the city with a reliable supply of water for domestic and agricultural uses. During 9000-3000BP insolation reduced in the Northern Hemisphere and meant the Pacific’s sea-surface temperature decreased and so ENSO events were much stronger. Evidence showed that the region became more arid and there was a particular pronounced drought at 4200BP.The region continued becoming more arid and this presented problems with water supply which may have contributed- among other factors- to the Harappans’ desertion. Oxygen isotopes from plankton also back the theory that a significant change in 4200BP led to reduced river flow from the Indus and variability in precipitation over Asia. The drought event fluctuated between 200 and 800yrs which also correlates with findings of cosmogenic 14C indicating that a change in solar variability is the reason for the changes seen in precipitation and aridity.

However, the difference in timings of increasing aridity and the phases in Harappan history suggest that whilst these environmental conditions may have hindered development they are not the sole cause as a societal collapse is unlikely to the effect of a single event. Moreover, an article by Enzel (1999) goes further stating that inferred water levels from lake sediments collected from Lunkaransar (a lake created when water tables are above ground) indicate a shallow lake during the early Holocene that rose rapidly in 6300 14C yrs BP and fell again drastically after 1000yrs. The sudden decrease in lake levels may be explained y changes in vegetation and precipitation but these changes were not uncommon and the conditions were in fact similar to present. Thus this sequence suggests there was no link between the rise and fall of the Harappans and that the major drought event –which happened 1500yrs earlier- had caused their collapse. However, this article does not seem to consider wider precipitation patterns and changes to the monsoon and local rivers which have also been considered as factors for the Harappan decline.

Therefore, of all the theories proposed changes to the natural environment seem to be the most probable cause for the collapse. This is in light of the fact that there is not enough evidence to support the Aryan invasion theory and correlating  evidence from other civilizations such as the Sumer Empire also show a sharp decline in society due to drought caused by changes to the climate during the same period. These environmental conditions most likely placed stresses on the ancient societies by reducing food and water security which in turn probably led to secondary factors such as strike, societal problems, the degradation of the city and eventual movement away from Harappa.  The changes to the monsoon (similar to the Australian casestudy) seem to have majorly impacted the society. Looking forward this is worrying as many societies still heavily rely on the monsoon for water security, for agricultural production for food security and as a major source of income (e.g. India gained $39billion in 2013for agricultural exports). Thus will climate change negatively impact the reliability of monsoons? Will farming methods have to change to deal with changes? Will these changes be done in time? And will future societies collapse if they can’t cope?

Feel free to comment below what you think will happen…

Fig. 3 - The intricate and famous Harappan seals (Source: Tes)

Climate change causing collapses currently?

So I came across this interesting comic a while back and saw the theory again on the BBC and it got me thinking on whether this is an example of how environmental conditions may lead to detrimental effects (even a possible collapse!) on society in the 21st century.

The articles states how the unrest in Syria could be linked back to environmental factors - in particular climate change.

Between 2006-2011 Syria suffered its worst drought, it was more intense and lasted longer than what could be explained by natural variability and so its is believed anthropogenic climate change is to blame. The effects of the drought were disastrous for the country with crop failures, 85% of livestock dying, pepper fields failing and more than 1 million farmers losing their land and livelihoods. With little government help farmers were forced to move into overcrowded cities and this exacerbated the problems of water supply, unemployment and poverty.

Eventually demonstrations against the governments and protests around the country lead to the uprising and civil unrest we've seen in the papers. around Million have been displaced, there have been numerous deaths and around 4 million people have left Syria.

This figure shows that the drought caused a significant loss of vegetation in Syria which led to massive reductions in agricultural productivity and displacement of the populations (source: USDA)

This severe drought and change to the landscape and livelihoods of people had caused a mass displacement of people and ended up leading to changes in society itself thus in this situation climate change can be seen as the 'unhinging stressor' for Syria but the impacts won't end there! Rising temperatures are expected to reduce agricultural capacity by 50% leading to food insecurity, droughts, economic losses and water shortages.
The director of Climate and Security has stated that the situation in Syria has illustrated the need to take environmental stress seriously and that future  of global security relies on our ability to manage climate stresses. This statement is important as changes to the environment can have major impact on lives, industry, governance and societies and harsh environmental conditions can even push societies to the brink (just look at the past collapses!).

But is this theory pushing it too far?  Could this situation even be considered as a collapse? Whilst I think this hypothesis is interesting and changes to the local environment do seem to have had a knock on effect on society in Syria, the underlying political situation seems to be the main reason for what we see going on. As far as the second question goes one misconception people may have of a collapse is that it means the population have moved away or died but Jared Diamond defines a collapse as ‘a decrease in population and/or in the political or economic complexity in a certain area over a period of time’. The ongoing migration out of Syria and the weakening of societal organisation and governance suggests that there has been a breakdown of how the nation’s society operates but I do not think this situation could be classified as a complete collapse like those seen in the past.

Nonetheless I started out this blog thinking that society would not collapse to such a scale in the past so it was interesting to see this example of how a collapse may occur in this century. And whilst the political situation seems to be the main driver of the issues facing Syria, environmental stresses –the drought and unreliable precipitation- seem to have exacerbated problems and are thus an important factor to take into consideration. Moreover, the devastation that can occur when a nation with political instability also faces climate change putting stress on resources such as food and water security illustrates how they can lead to conflicts and problems in the effective running of society. Thus we need to take the real threat that environmental stresses can cause seriously and as stated by Prince Charles start acting now in regards to climate change and future security.

On the whole this example does bring into the question the issue of societal collapse in this century and what it could mean to societies around the world through the implications of changes to the local climate and environmental processes. Comment below if you reckon something like climate change or changes to regional environments could lead to similar issues or even a collapse in the future.

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.