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.
More than eight out of every ten Australians live within 50km of the coast.
The Intergovernmental Panel on Climate Change says global sea levels are set to increase by the equivalent of 12mm/year, four times the average of the last century.
A major challenge for managing such a large increase in sea level is our limited understanding of what impact this scale of change might have on humanity.
While there are excellent online resources to model the local physical impacts of sea level rise, the recent geological past can provide important insights into how humans responded to dramatic increases in sea level.
The last ice age
At the height of the last ice age some 21,000 years ago, not only were the Greenland and Antarctic ice sheets larger than they are today, but 3km-high ice sheets covered large parts of North America and northern Europe.
This sucked vast amounts of water out of our planet’s oceans. The practical upshot was sea level was around 125m lower, making the shape of the world’s coastlines distinctly different to today.
As the world lurched out of the last ice age with increasing temperatures, the melting ice returned to the ocean as freshwater, dramatically increasing sea levels and altering the surface of our planet.
Arguably nowhere experienced greater changes than Australia, a continent with a broad continental shelf and a rich archaeological record spanning tens of millennia.
A bigger landmass
For most of human history in Australia, lower sea levels joined mainland Australia to both Tasmania and New Guinea, forming a supercontinent called Sahul. The Gulf of Carpentaria hosted a freshwater lake more than twice the size of Tasmania (about 190,000km2).
Our study shows that lower sea levels resulted in Australia growing by almost 40% during this time – from the current landmass of 7.2 million km2 to 9.8 million km2.
The coastlines also looked very different, with steep profiles off the edge of the exposed continental shelf in many areas forming precipitous slopes and cliffs.
Imagine the current coastline where the Twelve Apostles are on Victoria’s Great Ocean Road and then extend them around much of the continent. Many rivers flowed across the exposed shelf to the then distant coast.
When things warmed up
Then between 18,000 and 8,000 years ago, global climate warmed, leading to rapid melting of the ice sheets, and seeing sea levels in the Australian region rising from 125m below to 2m above modern sea levels.
Tasmania was cut off with the flooding of Bass Strait around 11,000 years ago. New Guinea was separated from Australia with the flooding of Torres Strait and creation of the Gulf of Carpentaria around 8,000 years ago.
We found that 2.12 million square km, or 20-29% of the landmass – a size comparable to the state of Queensland – was lost during this inundation. The location of coastlines changed on average by 139km inland. In some areas the change was more than 300km.
Much of this inundation occurred over a 4,000-year period (between 14,600 and 10,600 years ago) initiated by what is called Meltwater Pulse 1A, a period of substantial ice sheet collapse releasing millions of cubic litres of water back into the oceans.
During this period, sea levels rose by 58m, equivalent to 14.5mm per year. On the ground, this would have seen movement of the sea’s edge at a pace of about 20-24m per year.
Impacts of past sea level rise
The potential impacts of these past sea-level changes on Aboriginal populations and societies have long been a subject of speculation by archaeologists and historians.
In his 1970s book Triumph of the Nomads: A History of Aboriginal Australia, the Australian historian Geoffrey Blainey hypothesised that:
Most tribal groups on the coast 18,000 years ago must have slowly lost their entire territory […] a succession of retreats must have occurred. The slow exodus of refugees, the sorting out of peoples and the struggle for territories probably led to many deaths as well as new alliances.
Archaeologists have long recognised that Aboriginal people would have occupied the now-drowned continental shelves surrounding Australia, but opinions have been divided about the nature of occupation and the significance of sea-level rise. Most have suggested that the ancient coasts were little-used or underpopulated in the past.
Our data show that Aboriginal populations were severely disrupted by sea-level change in many areas. Perhaps surprisingly the initial decrease in sea level prior to the peak of the last ice age resulted in people largely abandoning the coastline, and heading inland, with a number of archaeological sites within the interior becoming established at this time.
During the peak of the last ice age, there is evidence on the west coast that shows people continued to use marine resources (shellfish, fish etc) during this time, albeit at low levels.
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.
So what are the lessons of the past for today? Thankfully, we can show that past societies survived rapid sea level change at rates slightly greater than those projected in our near future, albeit with population densities far lower than today.
But we can also see that sea level rise resulted in drastic changes to where people lived, how they survived, what technology they used, and probable modifications to their social, religious and political ways of life.
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.
Sean Ulm, Deputy Director, ARC Centre of Excellence for Australian Biodiversity and Heritage, James Cook University; Alan N Williams, Associate Investigator, ARC Centre of Excellence for Australian Biodiversity and Heritage, UNSW; Chris Turney, ARC Centre of Excellence for Australian Biodiversity and Heritage, University of New South Wales, UNSW, and Stephen Lewis, Principal Research Officer, James Cook University
The link below is to an article reporting on plans to drill the Atlantic coast of the USA for oil.
This is the eleventh article in our Contested Spaces series. These pieces look at the conflicting uses, expectations and norms that people bring to public spaces, the clashes that result and how we can resolve these.
When we think of coasts, we are likely to think about the great sandy beaches that have been the destination for many day trips and long weekends. At times these spaces have been sources of contestation, especially in areas of public access and codes of conduct. However, behind the sand dunes are other landscapes with deep histories of social conflict.
Moments from coastal pasts have had a major impact on how we see different coasts today. They feed into distinct ideals and ethics on place, especially in terms of how it is developed.
Noosa Heads versus Surfers Paradise
Noosa Heads is a prime example of this. Noosa’s history during colonisation includes a number of difficult stories to tell. Examples include the contentious tale of the rescue of Eliza Fraser, or the fate of the traditional owners, the Gubbi Gubbi people, at the hands of the colonial settlers and the native police.
Yet it was in the 1960s when modern conflict over land use really took shape in Noosa. A proposal by the developer T.M. Burke to build a resort at Alexandria Bay created a stir among locals. The local shire was set to build an access road around the headland, destroying well-trodden walking tracks.
A group led by local Arthur Harrold fought this proposal and formed the still-operating Noosa Parks Association. Thus began a long-standing fight against over-development, mining and other impediments to what residents saw as the natural beauty of the coast. This included the Cooloola Conflict and the now-famed resistance to high-rise development.
While there are elements of conservationism here to consider, these conflicts arose in a bid to keep Noosa low-key, with a slower mentality and authentic natural surrounds. Today, these ethics of authenticity are firmly embedded in planning regulation, illustrating the strength of local resistance past.
Noosa residents’ key fear in the 1960s and ’70s was losing their sense of place to the different ideals embodied in another coastal mecca, Surfers Paradise. Like Noosa, Surfers has a long history of conflict. Yet this place developed much differently due to several key factors.
Arguably, the significant turning point was in 1925 when Jim Cavill bought the then Elston Hotel and renamed it the “Surfers Paradise” hotel. Cavill and his wife proceeded to turn the coastal setting into something more than a place to bathe or surf.
Alongside the hotel, they built a zoo full of exotic animals that gave the place a peculiar flavor. Having been influenced by the American example of how to develop coasts, Cavill exhibited a desire to construct Surfers Paradise as an exotic international resort. However, due to the war in the Pacific, Surfers Paradise was restricted by building codes, frustrating locals who were eager to begin making the space bigger.
Shortly after the war, the codes eased and developers flocked to the “Golden Coast”. In the course of development, local leaders such as the progress association often came into conflict with governance.
In the example of parking meters, this led to the controversial meter maid scheme, which further established Surfers Paradise’s theme as an overtly transgressive and sexualised place.
Conflicts of a climate-changed future
In both spaces, conflicts have continued into contemporary times.
Recently, for instance, the fight against the proposed Southport Spit development has again drawn locals into conflict with authorities. Such fights against development continue up and down our coastlines. These are mostly driven by the desire to maintain a specific lifestyle and aesthetic appeal.
However, early critics of coastal development saw other concerns about coastal development. For instance, in 1879 a journalist for The Gympie Times, while contemplating the construction of Noosa and Tewantin, wondered about the location of the village and whether one day seawater might be running between you and your neighbour.
While we have different motivations for maintaining or developing our coastal places, we seem to neglect discussions about the risks of living so close to the ocean.
History has shown that several of our coastal meccas are already susceptible to significant damage from storms and cyclones. We scramble to rebuild following these events, but few debates are had about retreating away from the sea.
As we continue into that risky climate-changed landscape, however, we might see new players like insurance companies become increasingly important.
Already in the tropics, insurance premiums have caused a stir politically and in the media. In the future, though, we may need to consider to whether we have to redefine our relationship with coasts as they become more risky places to live.
You can find other pieces published in the series here.
This is the ninth article in our Contested Spaces series. These pieces look at the conflicting uses, expectations and norms that people bring to public spaces, the clashes that result and how we can resolve these.
Head to a beach like Bondi on Christmas Day and you’ll share that space with more than 40,000 people. But we aren’t just jostling with each other for coveted beach space. Scuttling, waddling, hopping or flying away from beachgoers all around Australia are crabs, shorebirds, baby turtles, crocodiles, fairy penguins and even dingoes.
Beaches are home to an incredible array of animals, and sharing this busy space with people is critical to their survival. But, if we find it hard to share our beaches with each other, how can we possibly find space for nature on our beaches?
Here’s a classic example of how hard it is to share our beaches with nature. Head to a busy beach at dawn, before the crowds arrive, and you will most likely see a number of small birds darting about.
You may recognise them from the short movie Piper – they are shorebirds. As the day progresses, swimmers, kite surfers, dog walkers, horse riders, 4x4s and children descend upon the beach en masse, unwittingly disturbing the shorebirds.
Unlike seabirds, shorebirds do not spend their life at sea. Instead, they specialise on the beach: foraging for their invertebrate prey, avoiding waves, or resting.
There are few places you can let your dog run for as long and as far as it pleases, which is one of the reasons beaches appeal to dog owners. But this disturbance results in heavy costs to the birds as they expend energy taking flight and cannot return to favourable feeding areas. Repeated disturbance can cause temporary or permanent abandonment of suitable habitat.
The fascinating thing about many of these shorebirds is that they are migratory. Beachgoers in Korea, China, Indonesia or New Zealand could observe the same individual bird that we have seen in Australia.
Yet these journeys come at a cost. Shorebirds must undertake gruelling flights of up to 16,000 kilometres twice a year to get from their breeding grounds in Siberia and Alaska to their feeding grounds in Australia and New Zealand. In their pursuit of an endless summer, they arrive in Australia severely weakened by their travels. They must almost double their body weight before they can migrate again.
And these birds must contend with significant daily disruption on their feeding grounds. A recent study in Queensland found an average of 174 people and 72 dogs were present at any one time on the foreshore of Moreton Bay, along Brisbane’s coastline. And 84% of dogs were off the leash – an off-leash dog was sighted every 700 metres – in potential contravention of regulations on dog control.
Managing the menagerie
One conservation approach is to set up nature reserves. This involves trying to keep people out of large areas of the coastal zone to provide a home for nature. Yet this rarely works in practice on beaches, where there are so many overlapping jurisdictions (for example, councils often don’t control the lower areas of the intertidal zone) that protection is rarely joined up.
However, our work at the University of Queensland shows we don’t need conservation reserves in which people are kept out. Quite the reverse. We should be much bolder in opening up areas that are specifically designated as dog off-leash zones, in places where demand for recreation is high.
In the case of Moreton Bay, 97% of foraging migratory shorebirds could be protected from disturbance simply by designating five areas as off-leash recreation zones. Currently, dogs must be kept under close control throughout the intertidal areas of Moreton Bay.
By zoning our beaches carefully, the science tells us that the most intense recreational activities can be located away from critical areas for nature. And there’s no reason why this logic couldn’t be extended to creating peaceful zones for beach users who prefer a quiet day out.
By approaching the problem scientifically, we can meet recreational demand as well as protect nature. Proper enforcement of the boundaries between zones is needed. Such enforcement is effective when carried out in the right places at the right time.
We believe that keeping people and their dogs off beaches to protect nature is neither desirable nor effective. It sends totally the wrong message – successful conservation is about living alongside nature, not separating ourselves from it.
Conservationists and recreationists should be natural allies, both working to safeguard our beautiful coasts. The key is to find ways that people and nature can co-exist on beaches.
You can find other pieces published in the series here.
Madeleine Stigner, Research assistant, The University of Queensland; Kiran Dhanjal-Adams, Research Associate Ecological Modeller, Centre for Ecology & Hydrology, and Richard Fuller, Associate Professor in Biodiversity and Conservation, The University of Queensland
Representatives of Australian coastal communities have gathered this week to discuss the major challenges they face. Delegates at the conference in Rockingham, Western Australia, represent 40 councils around Australia, some falling within the 24 federal electorates held by a margin of 5% or less. In contrast to the federal budget, climate change is at the top of their agenda.
Sea-level rise, floods, storms and bushfire were common concerns. The Australian Coastal Councils Conference’s May 6 communique demands national action:
Coastal councils and their communities call on the Australian Government to play a leadership role in developing a co-ordinated national approach to coastal management by adopting a set of policy initiatives based on the recommendations of the bipartisan Australian Parliamentary Coastal Inquiry.
Challenges of growth and change
Australia’s population is set to grow from 24 million to 40 million people by 2050. On present trends, this growth is likely to be concentrated in coastal regions, mostly along the eastern seaboard.
Australian Coastal Councils Association chair Barry Sammels, the mayor of Rockingham, observed:
Coastal seats are among the most vulnerable at the forthcoming election. Some of them are growing very rapidly, and others are changing demographically as ‘sea-changers’ migrate to coastal areas and people with young families are relocating from the cities in search of a better quality of life. This invariably means these regional coastal electorates, which have traditionally elected conservative political candidates, are becoming politically more volatile.
These communities are “at the forefront of climate vulnerability”, Sammels said. They are already dealing with coastal erosion and the prospect of rising sea levels and more frequent and extreme weather events.
Coastal communities, in particular those which are changing in character, are demanding these risks be taken seriously. … They currently feel there is a lack of commitment from both major parties to deal with these threats.
Lack of urgency at the top
While bipartisan interest in cities policies is growing, this needs to be extended to coastal regions experiencing big changes on several fronts – demographic, economic and environmental.
The lack of long-term strategic coastal planning puts both communities and environments at risk. The bleaching of the Great Barrier Reef illustrates the impacts of environmental change on tourism, jobs and long-term economic security.
We need a national plan to support local councils to better manage coastal urban development, climate change and the consequences for their communities. We have had over 25 national reports leading to largely no action.
In the communique, coastal councils reasonably call for action on key recommendations of the comprehensive 2009 parliamentary inquiry:
We propose that the following recommendations of the coastal inquiry be adopted:
That the Australian Government, in co-operation with state, territory and local governments, and in consultation with coastal stakeholders, develop an Intergovernmental Agreement on the Coastal Zone to be endorsed by the Council of Australian Governments.
The Australian Government ensure that [the agreement] forms the basis for a National Coastal Zone Policy and Strategy, which should set out the principles, objectives and actions that must be taken to address the challenges of integrated coastal zone management for Australia.
Despite much-reduced federal funding, the National Climate Change Adaptation Facility continues to help inform action by local government. Clearly, however, better long-term planning is required. This requires deeper institutional support, including a national perspective on urban growth in the context of climate change.
Action has begun locally
Finally, not all coastal planning and management is achieved through law and policy. A great deal of activity occurs locally through goodwill and collaboration. To highlight three examples:
in the west, the Peron Naturaliste Partnership involving nine local councils in the south-west, which won the 2016 Australian Coastal Award for Climate Adaptation
in the south, the South East Councils Climate Alliance in south-east Melbourne
in the north, a wide range of stakeholders in north-east Arnhem Land work together under the Dhimmiru Arnhem Land Sea Country Plan.
Such collaboration and innovation deserves long-term funding from higher levels of government.
We may have got this far without an integrated approach to coastal planning and management, but without it there is no way we will be able to manage coastal growth with the projected demographic, economic and climate changes.
That’s why local councils are demanding immediate action on a national coastal policy to meet the needs of our coastal communities and environment. To ignore their call is a very significant political risk indeed.