Tag Archives for erosion

Climate change is making ocean waves more powerful, threatening to erode many coastlines


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Thomas Mortlock, Macquarie University; Itxaso Odériz, Universidad Nacional Autónoma de México (UNAM); Nobuhito Mori, Kyoto University, and Rodolfo Silva, Universidad Nacional Autónoma de México (UNAM)Sea level rise isn’t the only way climate change will devastate the coast. Our research, published today, found it is also making waves more powerful, particularly in the Southern Hemisphere.

We plotted the trajectory of these stronger waves and found the coasts of South Australia and Western Australia, Pacific and Caribbean Islands, East Indonesia and Japan, and South Africa are already experiencing more powerful waves because of global warming.

This will compound the effects of sea level rise, putting low-lying island nations in the Pacific — such as Tuvalu, Kiribati and the Marshall Islands — in further danger, and changing how we manage coasts worldwide.

But it’s not too late to stop the worst effects — that is, if we drastically and urgently cut greenhouse gas emissions.

An energetic ocean

Since the 1970s, the ocean has absorbed more than 90% of the heat gained by the planet. This has a range of impacts, including longer and more frequent marine heatwaves, coral bleaching, and providing an energy source for more powerful storms.

Since at least the 1980s, wave power has increased worldwide as more heat is pumped into the ocean.
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But our focus was on how warming oceans boost wave power. We looked at wave conditions over the past 35 years, and found global wave power has increased since at least the 1980s, mostly concentrated in the Southern Hemisphere, as more energy is being pumped into the oceans in the form of heat.

And a more energetic ocean means larger wave heights and more erosive energy potential for coastlines in some parts of the world than before.



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Ocean waves have shaped Earth’s coastlines for millions of years. So any small, sustained changes in waves can have long-term consequences for coastal ecosystems and the people who rely on them.

Mangroves and salt marshes, for example, are particularly vulnerable to increases in wave energy when combined with sea level rise.

To escape, mangroves and marshes naturally migrate to higher ground. But when these ecosystems back onto urban areas, they have nowhere to go and die out. This process is known as “coastal squeeze”.

These ecosystems often provide a natural buffer to wave attack for low-lying coastal areas. So without these fringing ecosystems, the coastal communities behind them will be exposed to more wave energy and, potentially, higher erosion.

Mangrove forests are among the most imperilled ecosystems as sea levels rise and ocean waves crash harder against the coast.
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So why is this happening?

Ocean waves are generated by winds blowing along the ocean surface. And when the ocean absorbs heat, the sea surface warms, encouraging the warm air over the top of it to rise (this is called convection). This helps spin up atmospheric circulation and winds.

In other words, we come to a cascade of impacts: warmer sea surface temperatures bring about stronger winds, which alter global ocean wave conditions.



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Our research shows, in some parts of the world’s oceans, wave power is increasing because of stronger wind energy and the shift of westerly winds towards the poles. This is most noticeable in the tropical regions of the Atlantic and Pacific Oceans, and the subtropical regions of the Indian Ocean.

But not all changes in wave conditions are driven by ocean warming from human-caused climate change. Some areas of the world’s oceans are still more influenced by natural climate variability — such as El Niño and La Niña — than long-term ocean warming.

In general, it appears changes to wave conditions towards the equator are more driven by ocean warming from human-caused climate change, whereas changes to waves towards the poles remain more impacted by natural climate variability.

Ocean waves are generated by winds blowing across the ocean surface.
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How this could erode the coasts

While the response of coastlines to climate change is a complex interplay of many processes, waves remain the principal driver of change along many of the world’s open, sandy coastlines.

So how might coastlines respond to getting hit by more powerful waves? It generally depends on how much sand there is, and how, exactly, wave power increases.

For example, if there’s an increase in wave height, this may cause increased erosion. But if the waves become longer (a lengthening of the wave period), then this may have the opposite effect, by transporting sand from deeper water to help the coast keep pace with sea level rise.

Sandy beaches, including those around South Australia and Western Australia, may see greater risk of erosion in coming decades as wave power increases.
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For low-lying nations in areas of warming sea surface temperatures around the equator, higher waves – combined with sea level rise – poses an existential problem.

People in these nations may experience both sea level rise and increasing wave power on their coastlines, eroding land further up the beach and damaging property.
These areas should be regarded as coastal climate hotspots, where continued adaption or mitigation funding is needed.

It’s not too late

It’s not surprising for us to find the fingerprints of greenhouse warming in ocean waves and, consequentially, along our coastlines. Our study looked only at historical wave conditions and how these are already being impacted by climate change.

But if warming continues in line with current trends over the coming century, we can expect to see more significant changes in wave conditions along the world’s coasts than uncovered in our backward-looking research.

However, if we can mitigate greenhouse warming in line with the 2℃ Paris agreement, studies indicate we could still keep changes in wave patterns within the bounds of natural climate variability.



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Still, one thing is abundantly clear: the impacts of climate change on waves is not a thing of the future, and is already occurring in large parts of the world’s oceans.

The extent to which these changes continue and the risk this poses to global coastlines will be closely linked to decarbonisation efforts over the coming decades.

This story is part of Oceans 21

Our series on the global ocean opened with five in depth profiles. Look out for new articles on the state of our oceans in the lead up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.The Conversation

Thomas Mortlock, Senior Risk Scientist, Risk Frontiers, Adjunct Fellow, Macquarie University; Itxaso Odériz, Research assistant, Universidad Nacional Autónoma de México (UNAM); Nobuhito Mori, Professor, Kyoto University, and Rodolfo Silva, Professor, Universidad Nacional Autónoma de México (UNAM)

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Managed retreat of settlements remains a tough call even as homes flood and coasts erode


Tayanah O’Donnell, Australian National UniversityIt is no joke that New South Wales residents are in the midst of their fourth “one in 100 year” event since January 2020. Much of the Australian east coast continues to experience heavy rainfall, strong winds and abnormally high tides. All will make the current floods worse.

As climate tipping points are reached and the Earth’s systems begin to buckle under the strain, the need for considered adaptation strategies is overwhelmingly clear. One of these strategies is for human settlements to retreat from areas most at risk, whether from floods or bushfires. While something needs to be done to ensure future generations do not suffer catastrophic consequences, managed retreat is a complex tool.

These strategic decisions in the next five to ten years will be challenging. And these decisions really matter: where and how do we build residential areas that can cope with a climate-changed world?



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What is managed retreat?

Managed retreat can be defined as “purposeful, co-ordinated movement of people and assets out of harm’s way”. Managed retreat more often refers to the retreat of existing development out of harm’s way. Planned retreat is usually the preferred phrasing for new development that is planned for possible future relocation.

Both planned and managed retreat are focused on the permanent relocation of people and assets, as opposed to the evacuations we are seeing now.

Managed retreat is experiencing a resurgence in scientific literature as the impacts of climate change become increasingly frequent, severe and more obvious. These impacts bring with them a recognition of the need for adaptation even as we urgently reduce greenhouse gas emissions.

Of course, relocating away from high-risk locations is not an entirely new concept. However, managed retreat in response to a changing climate is not only complex, but also has a lot of political baggage. The complexity spans legal, financial, cultural and logistical factors among others: the political baggage seemingly associated with effective climate action in Australia often hinders governments’ abilities to respond properly.

Societies around the world need to grapple with the reality that managed retreat will become a suite of tools to respond to crisis. Insurers will not always be available, and the costs to governments (and therefore to you, the taxpayer) of responding to increasing rates of disasters, irrespective of insurance, will continue to grow exponentially.



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Responding to events after the fact is an unsustainable model of adaptation. There is, too, a need to acknowledge settlement needs and historical built environment legacies that have put significant state infrastructure in harm’s way.

Managing difficult trade-offs

We know trade-offs need to be made between what we protect and what we let go in suburban floodplain areas.

Legal machanisms to force people and assets to move can and must be thoughtful. The implementation of managed retreat in urbanised areas faces multiple hurdles. These include:



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It is wrong to see managed retreat as the panacea for climate risk and development in vulnerable locations. In many cases, once development is in place, it can be more appealing to some to protect an at-risk area rather than work towards managed retreat. Even where managed retreat has been successful, as in the case of the flood-prone township of Grantham, it was not without pain.

There are also other, more basic needs, such as having land available where people can relocate.

Working out highest and best use of land

There are ways that land can be used for its highest and best use at a point in time. For example, tools like easements can enable vulnerable land to be used, subject to event-based or time-based trigger-point thresholds. Once these thresholds are reached, the land is put to some other use. The advantage of these machanisms, especially for new development, is that owners are clear about the risks from the start.

This still leaves us with hard decisions about responding to at-risk current developments. Putting off these hard decisions and leaving them for future decision-makers will result in a huge injustice, because there will be catastrophe as Earth’s tipping points are passed. Development decisions made now will determine the impacts on our children and grandchildren.

Urban development decisions for both new and existing development in this coming decade demand courage and leadership. If we accept that Australian cities will continue to expand and increase in density, then we have some serious questions to ask ourselves. What kind of future do we want?

Some areas should simply not be developed.



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There is a risk that an over-reliance on managed retreat will over-simplify the challenge of working out what to do about development in at-risk locations. There is a clear need to separate out what to do about current and past developments, and how to approach new developments.

The latter is easy – do not rebuild residential homes in at-risk areas. Governments should repurpose these zones for uses that permit nature-based solutions to the need to adapt to climate change.

Current development is much more complex. In some cases, managed retreat – done thoughtfully and considerately – will be the only option.The Conversation

Tayanah O’Donnell, Honorary Senior Lecturer, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

One of Australia’s most famous beaches is disappearing, and storms aren’t to blame. So what’s the problem?



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Thomas Murray, Griffith University; Ana Paula da Silva, Griffith University; Darrell Strauss, Griffith University; Guilherme Vieira da Silva, Griffith University, and Rodger Tomlinson, Griffith University

Storms or tropical cyclones usually get the blame when Australia’s beaches suffer severe erosion. But on the New South Wales north coast at Byron Bay, another force is at play.

Over the past six months, tourists and locals have been shocked to see Byron’s famous Main Beach literally disappearing, inundated with water and debris. In October, lifesavers were forced to temporarily close the beach because they couldn’t get rescue equipment onto the sand. Resident Neil Holland, who has lived in the area for 47 years, told the ABC:

It’s the first time I’ve seen it this bad in all the time that I’ve been here, and it hasn’t stopped yet. The sand is just being taken away by the metre.

So what’s happening? To find the answer, we combined a brief analysis of satellite imagery with previous knowledge about the process behind the erosion and how it has been occurring at Byron Bay. The erosion is due to a process known as “headland bypassing”, and it is quite different to erosion from storms.

What is headland bypassing?

Headland bypassing occurs when sand moves from one beach to another around a solid obstruction, such as a rocky headland or cape. This process is mainly driven by wave energy. Along the coast of southeast Australia, waves generate currents that move sand mostly northward along the northern NSW coastline, and on towards Queensland.

However, sand does not flow evenly or smoothly along the coast: when sand arrives at a beach just before a rocky headland, it builds up against the rocks and the beach grows wider. When there is too much sand for the headland to hold, or there’s a change in wave conditions, some sand will be pushed around the headland – bypassing it – before continuing its journey up the coast.



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This large lump of moving sand is called a “sand pulse” or “sand slug”. The sand pulse needs the right wave conditions to move towards the shore. Without these conditions, the beach in front of the pulse is deprived of sand and the waves and currents near the shore erode the beach.

Headland bypassing was first described in the 1940s. However, only about 20 years ago was it recognised as an important part of the process controlling sand moving along the coast. Since then, with better technology and more data, researchers have studied the process in more detail, and helped to shed light on how headland bypassing might affect long-term coastal planning.

Recent studies have shown wave direction is particularly important to headland bypassing. Importantly, weather patterns that produce waves are affected by climate drivers including the El Niño Southern Oscillation and the Interdecadal Pacific Oscillation. So, future changes in the way these drivers behave will affect the waves and currents that move sand along our coast, which in turn affects headland bypassing and beach erosion.

Man sitting near eroded beach
Byron Bay’s beaches have badly eroded in recent months.
Byron Shire Council

What’s happening at Byron Bay?

In October and November this year, a large amount of sand was present just north of Cape Byron, from Wategos Beach to The Pass Beach. As this sand pulse grew, Clarkes Beach, and then Main Beach, were starved of their usual sand supply and began to erode.

The sand pulse is visible on satellite images from around April 2020. Each month, it slowly moves westward into the bay. As the sand pulse grows, the beach ahead of the pulse gradually erodes. At present Main Beach is at the eroding stage.



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Similar erosion was observed at Main Beach in the early 1990s. The beach became wider again from 1995 to 2007. From 2009 onwards, the shoreline erosion slowly began again, and became very noticeable in the past six months.

The effect of sand pulses on beach erosion is not exclusive to Byron Bay. It has been described previously in other locations, such as NSW’s Kingscliff Beach in 2011. In that case, the erosion risked damaging a nearby holiday park and bowling club.

Satellite images showing sand movement around Cape Byron
Satellite images showing sand movement around Cape Byron.
Author provided

When will this end?

Mild waves from the east to northeast, which usually occur from October to April each year, will help some of the sand pulse move onto Clarkes Beach and then further along to Main Beach. This normally happens over several months to a year. But it’s hard to say exactly when the beach will be fully restored.

This uncertainty underscores the need to better forecast these processes. This would help us to predict when bypassing sand pulses will occur and to manage beach erosion.

Climate change is expected to affect wave conditions, although the exact impact on the headland bypassing process remains unclear. However, better predictions would allow the community to be informed early about expected impacts, and officials could better manage and plan for future erosion.

Meanwhile, Byron Bay waits and watches – knowing at least that the erosion problem will eventually improve.The Conversation

People walking along Main Beach
The sand at Main Beach at Byron Bay, pictured here under good conditions, will eventually return.
AAP

Thomas Murray, Research Fellow (Coastal Management), Griffith University; Ana Paula da Silva, PhD Candidate, Griffith University; Darrell Strauss, Senior Research Fellow, Griffith University; Guilherme Vieira da Silva, Research Fellow, Griffith University, and Rodger Tomlinson, Director – Griffith Centre for Coastal Management, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Unwelcome sea change: new research finds coastal flooding may cost up to 20% of global economy by 2100



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Ebru Kirezci, University of Melbourne and Ian Young, University of Melbourne

Over the past two weeks, storms pummelling the New South Wales coast have left beachfront homes at Wamberal on the verge of collapse. It’s stark proof of the risks climate change and sea level rise pose to coastal areas.

Our new research published today puts a potential price on the future destruction. Coastal land affected by flooding – including high tides and extreme seas – could increase by 48% by 2100. Exposed human population and assets are also estimated to increase by about half in that time.

Under a scenario of high greenhouse gas emissions and no flood defences, the cost of asset damage could equate up to 20% of the global economy in 2100.

Without a dramatic reduction in greenhouse gas emissions, or a huge investment in sea walls and other structures, it’s clear coastal erosion will devastate the global economy and much of the world’s population.

In Australia, we predict the areas to be worst-affected by flooding are concentrated in the north and northeast of the continent, including around Darwin and Townsville.

Man cleans up after Townsville flood
A clean-up after flooding last year in Townsville, an Australian city highly exposed to future sea level rise.
Dan Peled/AAP

Our exposed coasts

Sea levels are rising at an increasing rate for two main reasons. As global temperatures increase, glaciers and ice sheets melt. At the same time, the oceans absorb heat from the atmosphere, causing the water to expand. Seas are rising by about 3-4 millimetres a year and the rate is expected to accelerate.

These higher sea levels, combined with potentially more extreme weather under climate change, will bring damaging flooding to coasts. Our study set out to determine the extent of flooding, how many people this would affect and the economic damage caused.



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We combined data on global sea levels during extreme storms with projections of sea level rises under moderate and high-end greenhouse gas emission scenarios. We used the data to model extreme sea levels that may occur by 2100.

We combined this model with topographic data (showing the shape and features of the land surface) to identify areas at risk of coastal flooding. We then estimated the population and assets at risk from flooding, using data on global population distribution and gross domestic product in affected areas.

Homes at Collaroy in Sydney damaged by storm surge
Many coastal homes, such as these at Sydney’s Collaroy beach, are exposed to storm surge damage.
David Moir/AAP

Alarming findings

So what did we find? One outstanding result is that due to sea level rise, what is now considered a once-a-century extreme sea level event could occur as frequently as every ten years or less for most coastal locations.

Under a scenario of high greenhouse gas emissions and assuming no flood defences, such as sea walls, we estimate that the land area affected by coastal flooding could increase by 48% by 2100.



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This could mean by 2100, the global population exposed to coastal flooding could be up to 287 million (4.1% of the world’s population).

Under the same scenario, coastal assets such as buildings, roads and other infrastructure worth up to US$14.2 trillion (A$19.82 trillion) could be threatened by flooding.

This equates to 20% of global gross domestic product (GDP) in 2100. However this worst-case scenario assumes no flood defences are in place globally. This is unlikely, as sea walls and other structures have already been built in some coastal locations.

In Australia, areas where coastal flooding might be extensive include the Northern Territory, and the northern coasts of Queensland and Western Australia.

Elsewhere, extensive coastal flooding is also projected in:
– southeast China
– Bangladesh, and India’s states of West Bengal and Gujurat
– US states of North Carolina, Virginia and Maryland
– northwest Europe including the UK, northern France and northern Germany.

A woman struggles through floodwaters in Bangladesh
Bangladesh is among the nations most exposed to coastal flooding this century.
SOPA

Keeping the sea at bay

Our large-scale global analysis has some limitations, and our results at specific locations might differ from local findings. But we believe our analysis provides a basis for more detailed investigations of climate change impacts at the most vulnerable coastal locations.

It’s clear the world must ramp up measures to adapt to coastal flooding and offset associated social and economic impacts.

This adaptation will include building and enhancing coastal protection structures such as dykes or sea walls. It will also include coastal retreat – allowing low-lying coastal areas to flood, and moving human development inland to safer ground. It will also require deploying coastal warning systems and increasing flooding preparedness of coastal communities. This will require careful long-term planning.

All this might seem challenging – and it is. But done correctly, coastal adaptation can protect hundreds of millions of people and save the global economy billions of dollars this century.



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The Conversation

Ebru Kirezci, PhD candidate, University of Melbourne and Ian Young, Kernot Professor of Engineering, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The world may lose half its sandy beaches by 2100. It’s not too late to save most of them



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John Church, UNSW

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.



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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.



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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.



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The implications

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.The Conversation

John Church, Chair Professor, Climate Change Research Centre, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Climate change may change the way ocean waves impact 50% of the world’s coastlines


Mark Hemer, CSIRO; Ian Young, University of Melbourne; Joao Morim Nascimento, Griffith University, and Nobuhito Mori, Kyoto University

The rise in sea levels is not the only way climate change will affect the coasts. Our research, published today in Nature Climate Change, found a warming planet will also alter ocean waves along more than 50% of the world’s coastlines.

If the climate warms by more than 2℃ beyond pre-industrial levels, southern Australia is likely to see longer, more southerly waves that could alter the stability of the coastline.

Scientists look at the way waves have shaped our coasts – forming beaches, spits, lagoons and sea caves – to work out how the coast looked in the past. This is our guide to understanding past sea levels.



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But often this research assumes that while sea levels might change, wave conditions have stayed the same. This same assumption is used when considering how climate change will influence future coastlines – future sea-level rise is considered, but the effect of future change on waves, which shape the coastline, is overlooked.

Changing waves

Waves are generated by surface winds. Our changing climate will drive changes in wind patterns around the globe (and in turn alter rain patterns, for example by changing El Niño and La Niña patterns). Similarly, these changes in winds will alter global ocean wave conditions.



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Further to these “weather-driven” changes in waves, sea level rise can change how waves travel from deep to shallow water, as can other changes in coastal depths, such as affected reef systems.

Recent research analysed 33 years of wind and wave records from satellite measurements, and found average wind speeds have risen by 1.5 metres per second, and wave heights are up by 30cm – an 8% and 5% increase, respectively, over this relatively short historical record.

These changes were most pronounced in the Southern Ocean, which is important as waves generated in the Southern Ocean travel into all ocean basins as long swells, as far north as the latitude of San Francisco.

Sea level rise is only half the story

Given these historical changes in ocean wave conditions, we were interested in how projected future changes in atmospheric circulation, in a warmer climate, would alter wave conditions around the world.

As part of the Coordinated Ocean Wave Climate Project, ten research organisations combined to look at a range of different global wave models in a variety of future climate scenarios, to determine how waves might change in the future.

While we identified some differences between different studies, we found if the 2℃ Paris agreement target is kept, changes in wave patterns are likely to stay inside natural climate variability.

However in a business-as-usual climate, where warming continues in line with current trends, the models agreed we’re likely to see significant changes in wave conditions along 50% of the world’s coasts. These changes varied by region.

Less than 5% of the global coastline is at risk of seeing increasing wave heights. These include the southern coasts of Australia, and segments of the Pacific coast of South and Central America.

On the other hand decreases in wave heights, forecast for about 15% of the world’s coasts, can also alter coastal systems.

But describing waves by height only is the equivalent of describing an orchestra simply by the volume at which it plays.

Some areas will see the height of waves remain the same, but their length or frequency change. This can result in more force exerted on the coast (or coastal infrastructure), perhaps seeing waves run further up a beach and increasing wave-driven flooding.

Similarly, waves travelling from a slightly altered direction (suggested to occur over 20% of global coasts) can change how much sand they shunt along the coast – important considerations for how the coast might respond. Infrastructure built on the coast, or offshore, is sensitive to these many characteristics of waves.

While each of these wave characteristics is important on its own, our research identified that about 40% of the world’s coastlines are likely to see changes in wave height, period and direction happening simultaneously.

While some readers may see intense waves offering some benefit to their next surf holiday, there are much greater implications for our coastal and offshore environments. Flooding from rising sea levels could cost US$14 trillion worldwide annually by 2100 if we miss the target of 2℃ warming.



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How coastlines respond to future climate change will be a response to a complex interplay of many processes, many of which respond to variable and changing climate. To focus on sea level rise alone, and overlooking the role waves play in shaping our coasts, is a simplification which has great potential to be costly.

The authors would like to acknowledge the contribution of Xiaolan Wang, Senior Research Scientist at Environment and Climate Change, Canada, to this article.The Conversation

Mark Hemer, Principal Research Scientist, Oceans and Atmosphere, CSIRO; Ian Young, Kernot Professor of Engineering, University of Melbourne; Joao Morim Nascimento, PhD Candidate, Griffith University, and Nobuhito Mori, Professor, Kyoto University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Cleaning up runoff onto the Great Barrier Reef: how art and science are inspiring farmers to help


Sarah Hamylton, University of Wollongong and Lucas Ihlein, University of Wollongong

The most recent report card on the Great Barrier Reef’s water quality highlighted major changes that need to be made to meet targets by 2018. Sediment and pollutant runoff from land use have increased 2-3 fold since 1850, largely driven by agricultural land clearing and grazing, while fertiliser used in sugar cane farming contributes to nitrogen runoff.

Runoff increases coral’s sensitivity to bleaching and disease, shifts the balance between coral and algae, leads to a build-up of pollutants in marine species that are long-lived or high in the food web, and increases the chances of crown-of-thorns starfish outbreaks.

Improving water quality will likely increase the health of reef organisms, and help reefs to bounce back from disturbances.

Government investment plans need to account properly for the total estimated value of the Great Barrier Reef and past progress in reducing runoff. An estimated A$500 million per year is needed to improve management action.

So what’s the best way to meet these targets? You won’t be surprised to find that scientists are working on the answer. But innovative projects fusing art and science are also appearing in north Queensland.

The problem of collective action

Like many environmental issues, runoff on the Great Barrier Reef is a classic example of a collective action problem. Collective action is at the heart of this issue in two ways.

First, the alongshore transport of sediment and runoff pollutants by currents means that the effects of managing runoff along one section of coastline may be felt elsewhere. The condition of the reef adjacent to a particular river mouth may not, therefore, necessarily reflect the land management within that river’s catchment.

Second, the health of the reef is dependent on other factors, such as bleaching driven by increased sea surface temperatures related to climate change. These are caused by many geographically remote activities (for instance, someone burning coal in London).

Collective action problems can be understood through US academic Garret Hardin’s famous “tragedy of the commons” theory. This theory states that self-interested individuals acting rationally may not behave in the best interests of the whole group.

Hardin used the example of a group of herdsmen allowing their cattle to graze a pasture that is running out of fodder. For an individual herdsman, the cost of removing cattle exceeds the benefit of leaving some pasture for the future, unless other herdsmen also agree to remove cattle.

Similarly, it takes an exceptional individual to reduce their runoff impacts, in light of the agricultural benefits to be gained from activities that increase runoff volume and decrease its quality (such as land clearing and use of fertilizers). This is particularly the case when others are not acting to abate their own activities.

Many farmers say that the Reef 2050 target to reduce runoff by 80% by 2025 is not economically viable. But without acting now, our metaphorical common (the inshore Great Barrier Reef) will continue to degrade.

Best environmental practice

Agriculture is a social and cultural activity, just as much as it is a process of environmental engineering, and the push to transform farming practices needs to recognise this. Top down incentive schemes do have some impact, but could there be a better way?

For instance, for sugar cane growers, the Smartcane Best Management Practice (BMP) Guidelines are an attempt by the industry to shift farming practices towards compliance with government directives to reduce run-off impacts on the reef.

The Smartcane BMP guidelines aim to improve farming practices through seven principles:

  1. Soil health and plant nutrition management

  2. Pest, disease and weed management

  3. Drainage and irrigation management

  4. Crop production and harvest management

  5. Natural systems management

  6. Farm business management

  7. Workplace health and safety management

As with many corporate social responsibility initiatives, growers who volunteer for Smartcane BMP are required to assess their current practices and set benchmarks for improvement in order to receive accreditation that indicates good environmental practice. There are clear marketing and, in many cases, cost-cutting benefits that motivate farmers to participate.

This has driven some examples of good practice within the farming community. However, as the 2015 report card shows, “only 23% of sugarcane land was managed using best management practice systems”, which is inadequate for achieving the Reef 2050 goal of an 80% reduction in dissolved nitrogen loads from agricultural runoff by 2025.

Motivating farmers

One project which engages with this problem is Sugar vs the Reef? by artists Lucas Ihlein, Kim Williams and Ian Milliss. This project is based on the idea that there is a greater chance of influencing farming practices if the desire to improve environmental performance comes from within the farming community. Innovation is celebrated from below by staging public collaborative events to generate dialogue about agriculture’s complex social and environmental interactions.

Innovative Mackay farmers Simon Mattsson and Allan Maclean in a dual crop of sugar cane and sunflowers. The sunflowers shade out weeds, break the sugarcane monocrop by diversifying soil biology, and attract a lot of attention, triggering public discussions about the crucial role of soil health in reducing runoff to the Great Barrier Reef.
Photo by Lucas Ihlein

For example, over the next two years, the project will coordinate a collaboration between Mackay Botanical Gardens, sugar cane farmers and community members to plant a dual crop of sunflowers and sugar cane as a highly visible work of “land art”.

This crop – whose cycle of planting, growth and harvesting will exceed the minimum standards of BMP – will stretch over four hectares near the centre of Mackay. Over two years, the project will engage sugarcane farmers, artists, high school students, members of the Australian South Sea Islander community, the Greater Whitsunday Food Network, soil and reef scientists, as well as the Great Barrier Reef Marine Park Authority.

While it is easy to point the finger at agricultural practices as a major cause of poor water quality in the inner waters of the Great Barrier Reef, change will be slow until the complex social factors that shape modern farming are recognised. This requires deeper engagement with the varied cultures of farming.

The Conversation

Sarah Hamylton, Senior Lecturer, School of Earth and Environmental Sciences, University of Wollongong and Lucas Ihlein, ARC DECRA Research Fellow, University of Wollongong

This article was originally published on The Conversation. Read the original article.

Coastal communities, including 24 federal seats at risk, demand action on climate threats


Barbara Norman, University of Canberra

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.

At the coming federal election, 24 coastal electorates are held by a margin of 5% or less.
Compiled with NATSEM, University of Canberra and the Australian Coastal Councils, Author provided

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

Population growth is concentrated in coastal centres vulnerable to climate change.
p.16 State of Australian Cities 2014-15, Australian Government

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.

And that:

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.

Mandurah, WA, epitomises both the pace of growth of coastal communities and their vulnerability to climate change.
Rexness/flickr, CC BY-SA

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:

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.

The Conversation

Barbara Norman, Chair of Urban & Regional Planning & Director of Canberra Urban & Regional Futures, University of Canberra

This article was originally published on The Conversation. Read the original article.