Guest essay by Eric Worrall
Ship of Fools expedition leader Chris Turney shares more of his climate wisdom.
Australia’s coastal living is at risk from sea level rise, but it’s happened before
January 16, 2018 6.06am AEDT
With global sea levels expected to rise by up to a metre by 2100 we can learn much from archaeology about how people coped in the past with changes in sea level.
In a study published this week in Quaternary Science Reviews, we looked at how changes in sea level affected different parts of Australia and the impact on people living around the coast.
The study casts new light on how people adapt to rising sea levels of the scale projected to happen in our near future.
A shrinking landmass
With the onset of the massive inundation after the end of the last ice age people evacuated the coasts causing markedly increased population densities across Australia (from around 1 person for every 355 square km 20,000 years ago, to 1 person every 147 square km 10,000 years ago).
Rising sea levels had such a profound impact on societies that Aboriginal oral histories from around the length of the Australian coastline preserve details of coastal flooding and the migration of populations.
We argue that this squeezing of people into a landmass 22% smaller – into inland areas that were already occupied – required people to adopt new social, settlement and subsistence strategies. This may have been an important element in the development of the complex geographical and religious landscape that European explorers observed in the 18th and 19th centuries.
Following the stabilisation of the sea level after 8,000 years ago, we start to see the onset of intensive technological investment and manipulation of the landscape (such as fish traps and landscape burning).
We also see the formation of territories (evident by marking of place through rock art) that continues to propagate up until the present time. All signs of more people trying to survive in less space.
In today’s world with substantially higher population densities, managing the relocation of people inland and outside Australia, potentially across national boundaries, may provide to be one of the great social challenges of the 21st century.
The abstract of the study;
Sea-level change and demography during the last glacial termination and early Holocene across the Australian continent
Alan N. Williams, Sean Ulmc, Tom Sapienza, Stephen Lewise, Chris S.M. Turneya
Future changes in sea-level are projected to have significant environmental and social impacts, but we have limited understanding of comparable rates of change in the past. Using comprehensive palaeoenvironmental and archaeological datasets, we report the first quantitative model of the timing, spatial extent and pace of sea-level change in the Sahul region between 35-8 ka, and explore its effects on hunter-gatherer populations. Results show that the continental landmass (excluding New Guinea) increased to 9.80 million km2 during the Last Glacial Maximum (LGM), before a reduction of 2.12 million km2 (or ∼21.6%) to the early Holocene (8 ka). Almost 90% of this inundation occurs during and immediately following Meltwater Pulse (MWP) 1a between 14.6 and 8 ka. The location of coastlines changed on average by 139 km between the LGM and early Holocene, with some areas >300 km, and at a rate of up to 23.7 m per year (∼0.6 km land lost every 25-year generation). Spatially, inundation was highly variable, with greatest impacts across the northern half of Australia, while large parts of the east, south and west coastal margins were relatively unaffected. Hunter-gatherer populations remained low throughout (<30,000), but following MWP1a, increasing archaeological use of the landscape, comparable to a four-fold increase in populations, and indicative of large-scale migration away from inundated regions (notably the Bass Strait) are evident. Increasing population density resulting from MWP1a (from 1/655 km2 to 1/71 km2) may be implicated in the development of large and complex societies later in the Holocene. Our data support the hypothesis that late Pleistocene coastal populations were low, with use of coastal resources embedded in broad-ranging foraging strategies, and which would have been severely disrupted in some regions and at some time periods by sea-level change outpacing tolerances of mangals and other near-shore ecological communities.
What can I say? Even in as talented a field as the study of Climate Science, Chris Turney is kindof special.
In 2016, Chris Turney explained to us that Antarctic penguins are incapable of dealing with adverse ice conditions.
Now Turney has shown us that climate change and sea level rise created overcrowding which drove Australian Aboriginals to burn large tracts of their homeland.
One can only speculate what Turney’s next climate insight will be.