Saturday, 1 January 2022

A map of the Prehistoric Continent of Sahul

Australia and New Guinea joined together by low sea levels
sixty five thousand years ago
and the vanished megafauna of the late Pleistocene

Map of Sahul and Pleistocene megafauna

"When people lived alongside creatures unique
Giants of fur and pouch, tooth scale and beak"

It was an ice age.
Not the most recent one, but the ice age before that.

Sea levels were far lower than today as vast amounts of the Earth’s water was held frozen in glaciers.
The lower sea levels exposed great areas of continental shelf, joining the islands of New Guinea, Australia and Tasmania to form the prehistoric continent of Sahul.

Evidence suggests the first people had arrived by this time. This map shows the details of the land and the now extinct megafauna they may have encountered.

Made in respect and acknowledgement of the traditional owners of these lands, of Elders past, present and future, whose ancestors first settled the continent and whose descendants remain custodians to this day.

Why illustrate a map of Sahul?

Our perception of what these lands are today can be expanded by a clear depiction of what they were in the past.

This map represents a very specific slice of time, 65,000 years ago, and does so playfully and with great attention to researched details. Since this time a lot has changed; the climate, the diversity of plants and animals and even the shape of the land.

We learn that much of what we consider to be permanent is actually not. The world changes.

An exciting slice of prehistory

A perfect setting for a fun megafauna map! During the ice-age-before-the-last much of the continent’s megafauna were still around, the contours and climate of the land were dramatically different to today and evidence suggests modern humans had arrived on these shores.

Geeky note!
What we commonly call an ice age is referred to by scientists as a glacial.
The coldest bit of the glacial is called a glacial maximum.
The warmer times in between glacials are called interglacials.
We are living during an interglacial, one that has been going for about 7000 years.
There have been more than 50 glacials in the last 2.6 million years!

The megafauna

The animals on this map include giant marsupials, a giant monitor lizard, a long legged crocodile, a horned tortoise, a huge snake, enormous birds and even a giant monotreme. 

There is good evidence for most of these animals existing at the time.

They represent the extinct megafauna of Australia and New Guinea, in particular the creatures which are now gone but were still around when people first arrived.

Megafauna is not a scientific term, but is generally considered to be animals 45kg and heavier. Most of the animals on this map were huge, much bigger than a person, though a few were included who were not so big but are far too charismatic not to be included.

There are of course megafauna which still live in Australia today ie. salt water crocodiles, and many other amazing smaller animals besides! They are not on this map. I only depicted the ones that are gone and so hold a nostalgic mystery.

The animals have mostly been placed where they might have lived, though for balance and aesthetics I used a bit of license.

The landscape and climate

The sea level

Wow, it turns out the shape of Australia used to look very different! 
Sea levels were far lower 65,000 years ago. Exactly how low is debated. A moderate estimate I found and used was 85 metres below the present sea level.

To depict Australia’s outline with a sea level 85 metres lower than today I used GEBCO 2020 bathymetric (sea floor) data fed into QGIS mapping software, created a map exposing all land above the chosen level and traced it. Yes, I had to learn to use mapping software in the process >.<

The resulting outline joins the islands of New Guinea, Australia and Tasmania into one big continent. This continent is known as Sahul, named after the continental shelf Australia sits on.

Apparently being joined up is the usual state of these lands. We live in the unusual time!

The rivers

With so much extra land exposed by low sea levels there once existed mighty rivers where now there is ocean. To show the paleorivers with some level of accuracy i referenced a couple of papers and stared at a lot of bathymetric imagery. It turns out the old river beds are still there, hidden under the sea! With a little effort they can be traced out.

Its not totally certain they accurately show where the paleorivers were 65,000 years ago, rivers do move over time. But its a pretty good approximation.

The lakes

Gosh, both the Gulf of Carpentaria and Bass Strait used to be lakes. Big lakes! Their outlines can still be seen with sea floor imaging. In fact a lake of super cold dense water still forms most winters at the very bottom of Bass Strait. Weird.

Many of Australia’s inland lakes, which are nowadays usually salt flats, were permanently full at this time. This is because it was cold and evaporation rates were low, and because of monsoon rains falling further south than usual. 

Imagine the extra life all this fresh water would bring to the heart of the continent. It would have been amazing to see.

The climate

As it was an ice age the world was colder than today. Accordingly snow lines were lower, as were the tree lines. There were even permanent glaciers in the Great Dividing Range and the Tasmanian highlands. 

Ocean currents were different, profoundly affecting the pattern of rainfall over the land. The north of the continent was cool and wet, with monsoonal rains reaching further south than today. The south of the continent was cold, dry and windy. Brrr!

This map was a lockdown project that took me a year to research and illustrate in my free time.
I hope you enjoy it!
R : )

Visit my Redbubble shop for
The Prehistoric Continent of Sahul
on posters, t-shirts and other fun items

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