For many coastal regions, sea-level rise is a looming crisis threatening our coastal society, livelihoods and coastal ecosystems. A new study, published in Nature Climate Change, has reported the world will lose almost half of its valuable sandy beaches by 2100 as the ocean moves landward with rising sea levels.
Sandy beaches comprise about a third of the world’s coastline. And Australia, with nearly 12,000 kilometres at risk, could be hit hard.
This is the first truly global study to attempt to quantify beach erosion. The results for the highest greenhouse gas emission scenario are alarming, but reducing emissions leads to lower rates of coastal erosion.
Our best hope for the future of the world’s coastlines and for Australia’s iconic beaches is to keep global warming as low as possible by urgently reducing greenhouse gas emissions.
Losing sand in coastal erosion
Two of the largest problems resulting from rising sea levels are coastal erosion and an already-observed increase in the frequency of coastal flooding events.
Erosion during storms can have dramatic consequences, particularly for coastal infrastructure. We saw this in 2016, when wild storms removed sand from beaches and damaged houses in Sydney.
After storms like this, beaches often gradually recover, because sand from deeper waters washes back to the shore over months to years, and in some cases, decades. These dramatic storms and the long-term sand supply make it difficult to identify any beach movement in the recent past from sea-level rise.
What we do know is that the rate of sea-level rise has accelerated. It has increased by half since 1993, and is continuing to accelerate from ongoing greenhouse gas emissions.
If we continue to emit high levels of greenhouse gases, this acceleration will continue through the 21st century and beyond. As a result, the supply of sand may not keep pace with rapidly rising sea levels.
Projections for the worst-case scenario
In the most recent Intergovernmental Panel on Climate Change (IPCC) report, released last year, the highest greenhouse gas emissions scenario resulted in global warming of more than 4°C (relative to pre-industrial temperatures) and a likely range of sea-level rise between 0.6 and 1.1 metres by 2100.
For this scenario, this new study projects a global average landward movement of the coastline in the range of 40 to 250 metres if there were no physical limits to shoreline movement, such as those imposed by sea walls or other coastal infrastructure.
Sea-level rise is responsible for the vast majority of this beach loss, with faster loss during the latter decades of the 21st century when the rate of rise is larger. And sea levels will continue to rise for centuries, so beach erosion would continue well after 2100.
For southern Australia, the landward movement of the shoreline is projected to be more than 100 metres. This would damage many of Australia’s iconic tourist beaches such as Bondi, Manly and the Gold Coast. The movement in northern Australia is projected to be even larger, but more uncertain because of ongoing historical shoreline trends.
What happens if we mitigate our emissions
The above results are from a worst-case scenario. If greenhouse gas emissions were reduced such that the 2100 global temperature rose by about 2.5°C, instead of more than 4°C, then we’d reduce beach erosion by about a third of what’s projected in this worst-case scenario.
Current global policies would result in about 3°C of global warming.
That’s between the 4°C and the 2.5°C scenarios considered in this beach erosion study, implying our current policies will lead to significant beach erosion, including in Australia.
Mitigating our emissions even further, to achieve the Paris goal of keeping temperature rise to well below 2°C, would be a major step in reducing beach loss.
Why coastal erosion is hard to predict
Projecting sea-level rise and resulting beach erosion are particularly difficult, as both depend on many factors.
For sea level, the major problems are estimating the contribution of melting Antarctic ice flowing into the ocean, how sea level will change on a regional scale, and the amount of global warming.
The beach erosion calculated in this new study depends on several new databases. The databases of recent shoreline movement used to project ongoing natural factors might already be influenced by rising sea levels, possibly leading to an overestimate in the final calculations.
Regardless of the exact numbers reported in this study, it’s clear we will have to adapt to the beach erosion we can no longer prevent, if we are to continue enjoying our beaches.
This means we need appropriate planning, such as beach nourishment (adding sand to beaches to combat erosion) and other soft and hard engineering solutions. In some cases, we’ll even need to retreat from the coast to allow the beach to migrate landward.
And if we are to continue to enjoy our sandy beaches into the future, we cannot allow ongoing and increasing greenhouse gas emissions. The world needs urgent, significant and sustained global mitigation of greenhouse gas emissions.
Where does beach sand come from? – Sly M., age 6, Cambridge, Massachusetts
There’s more to beach sand than meets the eye. It has stories to tell about the land, and an epic journey to the sea. That’s because mountains end their lives as sand on beaches.
Over time, mountains erode. The mud, sand, gravel, cobbles and boulders they shed are washed into streams, which come together to form rivers. As they flow down to the sea, all this sediment is ground up and worn down in nature’s version of a rock tumbler.
Big rocks break down into smaller pieces, so most of what reaches the sea is mud. These silt and clay particles are too small to perceive with the naked eye. But you can see individual grains of sand, which are just bigger bits of rock.
Next time you’re at the beach, pick up a handful of sand and look closely at it. Are all the grains the same color, or a rainbow assortment? Are they jagged and angular, or smooth and round?
Different colors of sand come from different minerals, like khaki feldspar, smoky white quartz, green olivine or black basalt. The mix of colors in beach sand tells you what kinds of rocks produced it.
The shape of sand grains also provides clues about where they come from. Angular grains of the same type of sand have not traveled as far as smooth round grains, which have been more worn down. And weak rocks break down to mud faster than hard rocks, so sand tends to be made of the harder types that break down slowly.
About a tenth of the supply of sediment that reaches the sea is sand. These particles are between about half a millimeter and 2 millimeters in size – roughly as thick as a penny. These particles are large enough that they don’t flow right out to the deep sea.
But the beach is just a temporary stop for sand. Big waves pull it offshore, and smaller waves push it along the coast. So keeping a beach nourished with sand is essential for keeping it sandy.
Yet today many beaches are starving. Many dams trap the sand that flows down rivers, piling it up in reservoirs. All in all, human activity has cut off about half the sand that would otherwise end up on the world’s beaches.
But humans haven’t turned the waves off, so as beach sand washes away and isn’t replenished, the shoreline erodes. That means that many beaches around the world are shrinking, slowly but surely.
So next time you dig your toes into beach sand think about the epic journey it took to arrive beneath your feet. Take a moment to think about where the sand came from and where it’s going.
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Carbonate sands on coral reefs will start dissolving within about 30 years, on average, as oceans become more acidic, new research published today in Science shows.
Carbonate sands, which accumulate over thousands of years from the breakdown of coral and other reef organisms, are the building material for the frameworks of coral reefs and shallow reef environments like lagoons, reef flats and coral sand cays.
But these sands are sensitive to the chemical make-up of sea water. As oceans absorb carbon dioxide, they acidify – and at a certain point, carbonate sands simply start to dissolve.
The world’s oceans have absorbed around one-third of human-emitted carbon dioxide.
Carbonate sand is vulnerable
For a coral reef to grow or be maintained, the rate of carbonate production (plus any external sediment supply) must be greater than the loss through physical, chemical and biological erosion, transport and dissolution.
It is well known that ocean acidification reduces the amount of carbonate material produced by corals. Our work shows that reefs face a double-whammy: the amount of carbonate material produced will decrease, and the newly produced and stored carbonate sands will also dissolve.
We measured the impact of acidity on carbonate sands by placing underwater chambers over coral reefs sands at Heron Island, Hawaii, Bermuda and Tetiaroa in the Pacific and Atlantic Oceans. Some of the chambers were then acidified to represent future ocean conditions.
The rate at which the sands dissolve was strongly related to the acidity of the overlying seawater, and was ten times more sensitive than coral growth to ocean acidification. In other words, ocean acidification will impact the dissolution of coral reef sands more than the growth of corals.
This probably reflects the corals’ ability to modify their environment and partially adjust to ocean acidification, whereas the dissolution of sands is a geochemical process that cannot adapt.
Sands on all four reefs showed the same response to future ocean acidification, but the impact of ocean acidification on each reef is different due to different starting conditions. Carbonate sands in Hawaii are already dissolving due to ocean acidification, because this coral reef site is already disturbed by pollution from nutrients and organic matter from the land. The input of nutrients stimulates algal growth on the reef.
In contrast, carbonate sands in Tetiaroa are not dissolving under current ocean acidification because this site is almost pristine.
What will this mean for coral reefs?
Our modelling at 22 locations shows that net sand dissolution will vary for each reef. However, by the end of the century all but two reefs across the three ocean basins would on average experience net dissolution of the sands.
A transition to net sand dissolution will result in loss of material for building shallow reef habitats such as reef flats and lagoons and associated coral cays. What we don’t know is whether an entire reef will slowly erode or simply collapse, once the sediments become net dissolving, as the corals will still grow and create reef framework. Although they will most likely just slowly erode.
It may be possible to reduce the impact of ocean acidification on the dissolution of reef sands, by managing the impact of organic matter like algae at local and regional scales. This may provide some hope for some already disturbed reefs, but much more research on this topic is required.
Ultimately, the only way we can stop the oceans acidifying and the dissolving of coral reefs is concerted action to lower CO₂ emissions.
In 2005, when I was chair of the National Committee on Soil and Terrain, I started a debate: where is Australia’s whitest beach? This was a diversion from the committee’s normal business of looking at the sustainable management of Australia’s soils, but it led down a path I hadn’t expected.
What began as a bit of after-hours banter became a serious look across Australia in search of our whitest beaches. New South Wales had already laid claim to the title, arguing that Hyams Beach at Jervis Bay has the whitest sand in the world, purportedly backed up by Guinness World Records.
As it turned out, both claims were false. Guinness World Records has no such category, and the whitest beach (as we found) is actually elsewhere.
So we drafted terms of reference, and the search for Australia’s Whitest Beach began. Over the next year samples were collected across the nation. The criteria were simple: samples had to be taken from the swash zone (the gently sloping area between the water and the dunes) and the samples could not be treated in any way apart from air-drying. No bleaching. No sieving out of impurities. Marine environment only.
The results of the first judging in 2006 were startling. Of all the states and territories, the much promoted Hyams Beach in New South Wales came in fourth. Third was Victoria, second Queensland, and first Western Australia.
The other states and territories came in at Tasmania fifth, Northern Territory sixth, and South Australia seventh. The ACT didn’t have a beach to sample, although technically some of the Commonwealth lands around our coasts could possibly come in under their banner (but that’s another debate altogether).
The winning beach was Lucky Bay in Cape Le Grand National Park on WA’s south coast, but in reality any of the beaches in this area could have been winners – Hellfire Bay, Thistle Cove and Wharton’s beach (just to name a few) are all magnificently white.
A quick qualification here: the southwestern end of Lucky Bay, where many people enter the beach, is covered with seaweed – not the whitest bit! I should also note that all of the finalists in the whitest beach challenge were in their own right fabulously white. But when compared side-by-side, some beaches are clearly whiter than others.
The Queensland team felt aggrieved, so in 2007 I carried out a repechage with new samples from Queensland at Whitehaven Beach in the Whitsundays, and Lake McKenzie on Fraser Island. Lake McKenzie was ultimately disallowed as it is a freshwater lake and the rules stipulated a marine environment. Meanwhile, Whitehaven didn’t quite cut the mustard in the judging and Lucky Bay in WA was again the winner.
So what makes a beach white, and is it important anyway?
The assessments were based on a visual comparison, so to remove any possible visual bias after the 2007 challenge all the samples were scanned for their reflectance – how much light bounced off the sand, essentially – in the visible and infrared wavelengths. Our assumption was that higher reflectance throughout the visual spectrum correlates with greater whiteness.
As it turned out, the results from the scanning exactly correlated with the visual assessments. The eye is quite good at discerning small differences in colour and reflectance. (More background and the results from the competition are available here.)
So what makes a beach white? Obviously, a pristine environment helps. Another factor is the distance from rivers, which deliver coloured organic and clay contaminants to the coast.
The geology of the area and the source of the sand are also critical, with quartz seemingly a major requirement for fine sands. Most white sandy beaches are derived from granitic, or less commonly sandstone, geologies that weather to produce fine, frosted quartz sand grains. Interestingly, sands made from shell or coral fragments just aren’t as white.
Is it important?
While this competition began in fun, I do believe it’s important. Beaches are places of refuge in this crazy world, and a pristine white beach indicates a cleanliness that is worth striving for. The reflectance of light off these sands through shallow waters near the beach creates a surreal, magical turquoise colour. White beaches are like the canary in the coalmine – once they’re spoiled, we know we’re in trouble.
Even though this study was a first look at some of Australia’s whitest beaches, and sampling was limited, it did highlight the sheer number of wonderful sandy beaches that Australia has.
The story’s not finished though. There are many white beaches out there yet to be sampled, and if you’d like to alert me to your potentially award-winning beach please email me or leave a comment on the whitest beach website.
It’s our responsibility, and I believe honour, to protect these amazing places. I’m sure there are more wonderful beaches out there that we haven’t sampled which may defeat Lucky Bay.
Shelburne Bay in northern Queensland, for example, is a contender yet to be sampled, and there are some magnificent beaches on the east coast of Tasmania. Whatever the outcome, let’s celebrate the natural wonders that surround our country.
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.