There’s no end to the damage humans can wreak on the climate. This is how bad it’s likely to get

Andrew King, The University of Melbourne; Nerilie Abram, Australian National University, and Sarah Perkins-Kirkpatrick, UNSWA major new report published last week by the Intergovernmental Panel on Climate Change (IPCC) contained grave warnings on where Earth’s climate is headed. So what happens if humanity doesn’t get its act together? How bad could climate change actually get?

The IPCC report canvassed various scenarios, from the most terrifying to the best possible case. It’s increasingly unlikely Earth will follow the path of very high greenhouse gas emissions, represented in dark red on the graph below, which would very likely lead to global warming of 3.3℃ to 5.7℃ this century.

But given current policy settings, it’s plausible Earth will follow a mid-range emissions scenario such as that represented in orange. Such a pathway would lead to global warming of between 2℃ and 3.5℃, relative to pre-industrial levels.

So what will Earth look like under warming of that magnitude? And what will life on this planet be like? Academic research can shed light on those crucial questions. And a warning: the answers are confronting.

An angrier, less hospitable world

The IPCC report confirmed Earth has warmed 1.09℃ since pre-industrial times. This level of warming is already causing significant damage.

Around the world over the past few months, the damage has been strikingly evident. Record-shattering heatwaves have struck North America’s west and southern Europe, while extreme rain and flooding has hit central Europe and China.

At 3℃ global warming, heatwaves would be even more frequent, intense and longer, while extreme rain will be heavier. The relationship between average global temperature and heat extremes is very strong, although this varies across regions.

Over Australia, heatwaves are expected to be slightly hotter than the corresponding global warming threshold. So with 3℃ of global warming, the hottest day of a heatwave will be about 3.6℃ warmer than pre-industrial conditions.

What’s more, heatwaves in Australia are projected to become four to five days longer for each degree of global warming.

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IPCC

The IPCC findings show in some parts of the world, there’s a clear relationship between future increases in global warming and a rise in extreme rainfall events. This includes the eastern part of the United States, Alaska and western Canada, Europe and parts of Russia and Africa. The projected increase applies to both daily rainfall events and those lasting five days.

Explore future projections of extreme rainfall and other climate variables with the IPCC’s interactive climate atlas.

Climate change has already damaged the world’s coral reefs. The Great Barrier Reef has bleached three times in the past five years, giving little time for the ecosystem to recover. In a 2018 report, the IPCC found coral reefs would decline by a further 70-90% under global warming of 1.5℃. Virtually all reefs would be lost with 2℃ warming.

Bushfire risk also increases the more we let the climate warm. As the Australian Academy of Science outlined in a report earlier this year, extreme fire days in Australia will increase with global temperatures.

Greater increases are projected for southern and eastern Australia. However, in much of Australia the frequency of extreme fire days increases by 100-300% once 3℃ global warming is reached.

And conditions conducive to mega-fires – such as those which occurred during the 2019-20 Black Summer – will occur more often over southeast Australia under continued climate change, especially during late spring.

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At 2℃ warming, the Great Barrier Reef and others like it will be virtually gone.
ARC Centre of Excellence/Tane Sinclair-Taylor

On thin ice

The more the planet warms, the more we risk triggering disastrous irreversible changes known as “tipping points”. Scientists have identified several potential tipping points which might occur – especially if the climate warms by more than 2℃, in line with the IPCC’s midway scenario.

For example, global warming may cause the West Antarctic ice sheet to collapse, resulting in several metres of sea level rise. The exact extent of global warming required to trigger such changes is very uncertain, and climate projections suggest we won’t hit any trigger points this century.

However, these irreversible changes remain a distinct possibility if greenhouse gas emissions continue their current trajectory.

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Ice sheet collapse in Antarctica would trigger irreversible sea level rise.
Natacha Pisarenko/AP

The choice is ours

Some climate changes we’ve described under the midway emissions scenario are awful for society and our environment.

And as CSIRO climate scientist Pep Canadell, a coordinating lead author of a chapter of the IPCC report, told the Guardian last week, if greenhouse gas emissions continue unabated “there is no bottom end to how much damage we can create”.

Humanity is now at a crossroads. The IPCC says if we halve global greenhouse gas emissions within the next 15 years, and reach net-zero emissions before 2060, we have a more than 90% chance of keeping global warming below 2℃.

That means every action matters. Each fraction of a degree of global warming prevented will reduce the climate damage and increase the chance Earth avoids the most catastrophic impacts of global warming.

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Andrew King, ARC DECRA fellow, The University of Melbourne; Nerilie Abram, Chief Investigator for the ARC Centre of Excellence for Climate Extremes; Deputy Director for the Australian Centre for Excellence in Antarctic Science, Australian National University, and Sarah Perkins-Kirkpatrick, Chief Investigator on the ARC Centre of Excellence for Climate Extremes; ARC Future Fellow, UNSW

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

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Wetlands have saved Australia $27 billion in storm damage over the past five decades

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Obadiah Mulder, University of Southern California and Ida Kubiszewski, Crawford School of Public Policy, Australian National University

Australia is in the midst of tropical cyclone season. As we write, a cyclone is forming off Western Australia’s Pilbara coast, and earlier in the week Queenslanders were bracing for a cyclone in the state’s far north (which thankfully, didn’t hit).

Australia has always experienced cyclones. But here and around the world, climate change means the cyclone threat is growing – and so too is the potential damage bill. Disadvantaged populations are often most at risk.

Our recent research shows 54 cyclones struck Australia in the 50 years between 1967 and 2016, causing about A$3 billion in damage. We found the damages would have totalled approximately A$30 billion, if not for coastal wetlands.

Wetlands such as mangroves, swamps, lakes and lagoons bear the brunt of much storm damage to coast, helping protect us and our infrastructure. But over the past 300 years, 85% of the world’s wetland area has been destroyed. It’s clear we must urgently preserve the precious little wetland area we have left.

Wetland areas provide important protection from cyclones.
Shutterstock

A critical buffer

National disasters cost Australia as much as A$18 billion each year on average. About one-quarter of this is due to cyclone damage.

Wetlands can mitigate cyclone and hurricane damage, by absorbing storm surges and slowing winds. For example in August 2020, Hurricane Laura hit the United States’ midwest. Massive damage was predicted, including a 6.5-metre storm surge extending 65 kilometres inland.

However the surge was one metre at most – largely because the storm drove straight into a massive wetland that absorbed most of the predicted flood.

In Australia, wetlands are lost through intentional infilling or drainage for mosquito control, or to create land for infrastructure and agriculture. They’re also lost due to pollution and upstream changes to water flows.

Australia’s wetlands are at risk. Pictured is the Caley Valley Wetlands, next to Adani’s Abbot Point coal terminal. Adani was fined for releasing polluted water into the wetland.
Gary Farr/ACF

Putting a price on cyclone protection

Our research set out to determine the financial value of the storm protection provided by Australia’s wetlands.

We examined the 54 cyclones that struck Australia in the five decades to 2016. We gathered data including:

• physical damage wrought in each storm swath (or storm path)
• gross domestic product (GDP) in the storm’s path
• maximum windspeed during each storm, which helps predict damage
• total area of wetlands in each swath.

Using a powerful type of statistics called Bayesian analysis, we estimated the extent to which GDP, windspeed and wetland area affected total damage. This allowed us to estimate damage caused in the absence of wetlands.

We found for every hectare of wetland, about A$4,200 per year in cyclone damage was avoided. This means the A$3 billion in cyclone damage over the past 50 years would have totalled approximately A$30 billion, if not for coastal wetlands.

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Importantly, the percentage of damage averted falls rapidly as wetland area decreases. And the protection afforded by a single hectare of wetland increases drastically if there are fewer other wetlands in the path of the storm. This makes protecting remaining wetland even more critical.

If the average cyclone path in Australia were to contain around 30,000 hectares of wetlands, it would avert about 90% of potential storm damage. If the wetland area dropped to 3,000 hectares, only about 30% of damage would be averted.

Climate change is making cyclones worse. By 2050, Australia’s annual damage bill could be as high as A$39 billion, assuming current levels of wetlands are maintained.

Seawalls and other artificial structures can be built along the coast to protect from storms. However, research in China has found wetlands are more cost-effective and efficient than man-made structures at preventing cyclone damage.

Unlike man-made structures, wetlands maintain themselves. Their only “cost” is the opportunity cost of not being able to use the land for something else.

Wetlands can help prevent cyclone damage, such as this wrought in Queensland during Cyclone Debbie in 2017.
Dan Peled/AAP

Keeping wetlands safe

According to recent analysis by the authors, which is currently under peer review, global wetlands provide US$447 billion (A$657 billion) worth of protection from storms each year.

Of course, wetlands provide benefits beyond storm protection. They store carbon, regulate our climate and control flooding. They also absorb waste including pollutants and carbon, provide animal habitat and places for human recreation.

Wetlands are an incredibly important resource. It’s critical we protect them from development and keep them healthy, so they can continue to provide vital services.

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This story is part of a series The Conversation is running on the nexus between disaster, disadvantage and resilience. You can read the rest of the stories here.

Obadiah Mulder, PhD Candidate in Computational Biology, University of Southern California and Ida Kubiszewski, Associate Professor, Crawford School of Public Policy, Australian National University

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

Climate explained: did atomic bomb tests damage our upper atmosphere?

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Brett Carter, RMIT University and Rezy Pradipta, Boston College

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Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

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I recently read an article stating the atomic bomb testing in the Pacific destroyed so much of the upper atmosphere that the US could no longer bounce communications off the atmosphere and had to deploy artificial satellites for communication. Is this true? And just how much damage did they do?

The article the question refers to doesn’t mention satellites, so let’s focus on the atmospheric damage part of the question. Indeed, surface and atmospheric (high-altitude) detonations of nuclear weapons can have short-term and long-term effects.

One short-term effect was a temporary blackout of long-distance high-frequency (HF) radio communication over the surrounding area. But this radio communication blackout was not a result of the nuclear explosions destroying the ionosphere.

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On the contrary, the nuclear detonations temporarily increased the natural level of ionisation in the upper atmosphere.

The ionosphere and radio communication

The Earth’s ionosphere is a natural layer of charged particles at approximately 80-1,000km altitude. This ionised portion of the Earth’s upper atmosphere largely owes its existence to solar radiation, which strips electrons from neutral atoms and molecules.

The ionosphere consists of three major layers, known as D, E and F layers. The lower D and E layers typically exist only during daylight hours, while the highest F layer always exists.

The ionosphere showing the approximate levels of the D, E and F layers. The D and E layers are much weaker at night time. The two yellow arrows show example ray paths of high-frequency radio waves from transmitters at ground level. Encounters with the D layer will result in some absorption.
The Conversation, CC BY-ND

These layers have distinct characteristics. The E and F layers are very reflective to HF radio waves. The D layer, on the other hand, is more like a sponge and absorbs HF waves.

In long-distance HF radio communications, the radio waves are bounced back and forth between the ionosphere and the Earth’s surface. This means you don’t need to establish a line of sight for HF radio communication.

Many applications, such as emergency services and aircraft/maritime surveillance, rely on this mode of HF radio propagation.

But this radio communication scheme only works well when there is a reflective E or F layer, and when the absorbing D layer is not dominant.

During regular daytime hours, the D layer often becomes a nuisance because it weakens radio wave intensity in the lower HF spectrum. However, by changing to higher frequencies you can regain broken communication links.

The D layer may become even more dominant when intense X-ray emissions from solar flares or energetic particles are impacting the atmosphere. The absorbing D layer then breaks any HF communication links that traverse it.

Bomb blasts and the ionosphere

Nuclear detonations also produce X-ray radiation, which leads to additional ionisation in all layers of the ionosphere. This makes the F layer more reflective to HF radio waves, but, alas, the D layer also becomes more absorptive.

This makes it difficult to bounce radio waves off the ionosphere for long-distance communication soon after a nuclear explosion, even though the ionosphere stays intact.

Beyond additional ionisation, shock waves from nuclear detonations produce waves and ripples in the upper atmosphere called “atmospheric gravity waves” (AGWs).

These waves travel in all directions, even reaching the ionosphere where they cause what are known as “travelling ionospheric disturbances” (TIDs), which can be observed for thousands of kilometres.

Other atmospheric disturbances

Bomb blasts are not the only things that cause disturbances in the atmosphere.

In September 1979, there were reports of bright flashes of light off the South African coast, igniting theories South Africa had nuclear weapon capabilities.

Analysis of ionospheric data from the Arecibo Observatory, in Puerto Rico, confirmed the presence of waves in the ionosphere that corroborated the theory of an atmospheric detonation. But whether the detonation was artificial or natural could not be determined.

The reason for the ambiguity is that meteor explosions and nuclear detonations in the atmosphere both generate AGWs with similar characteristics.

Common sources of atmospheric gravity waves (AGW) that could cause travelling ionospheric disturbances (TID).
Rezy Pradipta, Author provided

The 2013 Chelyabinsk meteor explosion in Russia generated waves in the ionosphere that were detected all across Europe, and as far away as the United Kingdom.

Volcanic eruptions, such at the 1980 Mount St Helens eruption in the US, and large earthquakes, such as the 2011 Tohoku earthquake in Japan, are other examples of energetic processes at the ground impacting the upper atmosphere.

Waves observed in the ionosphere above Japan during the 2011 Tohoku earthquake.

Another well-known source of ionospheric disturbances is the geomagnetic storm, typically caused by coronal mass ejections from the Sun or solar wind disturbances impacting Earth’s magnetosphere.

Satellites as backup

In summary, nuclear detonations can impact the upper atmosphere in many ways, as do many other non-nuclear terrestrial and solar events that carry enormous energy. But the damage (so to speak) isn’t permanent.

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Did the impact of these nuclear tests on the ionosphere specifically lead to the immediate launch of communications satellites? Not directly, because the impacts were temporary.

But in the Cold War setting, the potential for adversaries to even briefly interrupt over-the-horizon communications would certainly have been a motivating factor in developing communications satellites as backup.

Brett Carter, Senior lecturer, RMIT University and Rezy Pradipta, Research scientist, Boston College

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

Climate explained: methane is short-lived in the atmosphere but leaves long-term damage

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Zebedee Nicholls, University of Melbourne and Tim Baxter, University of Melbourne

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Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

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Methane is a shorter-lived greenhouse gas – why do we average it out over 100 years? By doing so, do we risk emitting so much in the upcoming decades that we reach climate tipping points?

The climate conversation is often dominated by talk of carbon dioxide, and rightly so. Carbon dioxide is the climate warming agent with the biggest overall impact on the heating of the planet.

But it is not the only greenhouse gas driving climate change.

Comparing apples and oranges

For the benefit of policy makers, the climate science community set up several ways to compare gases to aid with implementing, monitoring and verifying emissions reduction policies.

In almost all cases, these rely on a calculated common currency – a carbon dioxide-equivalent (CO₂-e). The most common way to determine this is by assessing the global warming potential (GWP) of the gas over time.

The simple intent of GWP calculations is to compare the climate heating effect of each greenhouse gas to that created by an equivalent amount (by mass) of carbon dioxide.

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In this way, emissions of one gas – like methane – can be compared with emissions of any other – like carbon dioxide, nitrous dioxide or any of the myriad other greenhouse gases.

These comparisons are imperfect but the point of GWP is to provide a defensible way to compare apples and oranges.

Limits of metrics

Unlike carbon dioxide, which is relatively stable and by definition has a GWP value of one, methane is a live-fast, die-young greenhouse gas.

Methane traps very large quantities of heat in the first decade after it is released in to the atmosphere, but quickly breaks down.

After a decade, most emitted methane has reacted with ozone to form carbon dioxide and water. This carbon dioxide continues to heat the climate for hundreds or even thousands of years.

Emitting methane will always be worse than emitting the same quantity of carbon dioxide, no matter the time scale.

How much worse depends on the time period used to average out its effects. The most commonly used averaging period is 100 years, but this is not the only choice, and it is not wrong to choose another.

As a starting point, the Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment Report from 2013 says methane heats the climate by 28 times more than carbon dioxide when averaged over 100 years and 84 times more when averaged over 20 years.

Many sources of methane

On top of these base rates of warming, there are other important considerations.

Fully considered using the 100-year GWP and including natural feedbacks, the IPCC’s report says fossil sources of methane – most of the gas burned for electricity or heat for industry and houses – can be up to 36 times worse than carbon dioxide. Methane from other sources – such as livestock and waste – can be up to 34 times worse.

Livestock are a source of methane emission into the atmosphere.
Flickr/mikeccross, CC BY-NC-ND

While some uncertainty remains, a well-regarded recent assessment suggested an upwards revision of fossil and other methane sources, that would increase their GWP values to around 40 and 38 times worse than carbon dioxide respectively.

These works will be assessed in the IPCC’s upcoming Sixth Assessment Report, with the physical science contribution due in 2021.

While we should prefer the most up to date science at any given time, the choice to consider – or not – the full impact of methane and the choice to consider its impact over 20, 100 or 500 years is ultimately political, not scientific.

Undervaluing or misrepresenting the impact of methane presents a clear risk for policy makers. It is vital they pay attention to the advice of scientists and bodies such as the IPCC.

Undervaluing methane’s impact in this way is not a risk for climate modellers because they rely on more direct assessments of the impact of gases than GWP.

Tipping points

The idea of climate tipping points is that, at some point, we may change the climate so much that it crosses an irreversible threshold.

At such a tipping point, the world would continue to heat well beyond our capability to limit the harm.

There are many tipping points we should be aware of. But exactly where these are – and precisely what the implications of crossing one would be – is uncertain.

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Unfortunately, the only way we can be sure of where these tipping points are is to cross them. The only thing we know for sure about them is that the impact on lives, livelihoods and the places we love would be beyond catastrophic if we did.

But we cannot ignore disturbing impacts of climate change that are already here.

For example, damage to the landscape from the Black Summer bushfires may be irreversible and this represents its own form of climate tipping point.

The scientific understanding of climate change goes well beyond simple metrics like GWP. Shuffling between metrics – such as 20-year or 100-year GWP – cannot avoid the fact our very best chance of avoiding ever-worsening climate harm is to massively reduce our reliance on coal, oil and gas, along with reducing our emissions from all other sources of greenhouse gas.

If we do this, we offer ourselves the best chance of avoiding crossing thresholds we can never return from.

Zebedee Nicholls, PhD Researcher at the Climate & Energy College, University of Melbourne and Tim Baxter, Fellow – Melbourne Law School; Senior Researcher – Climate Council; Associate – Australian-German Climate and Energy College, University of Melbourne

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

Extreme weather caused by climate change has damaged 45% of Australia’s coastal habitat

Bleached staghorn coral on the Great Barrier Reef. Many species are dependent on corals for food and shelter.
Damian Thomson, Author provided

Russ Babcock, CSIRO; Anthony Richardson, The University of Queensland; Beth Fulton, CSIRO; Eva Plaganyi, CSIRO, and Rodrigo Bustamante, CSIRO

If you think climate change is only gradually affecting our natural systems, think again.

Our research, published yesterday in Frontiers in Marine Science, looked at the large-scale impacts of a series of extreme climate events on coastal marine habitats around Australia.

We found more than 45% of the coastline was already affected by extreme weather events caused by climate change. What’s more, these ecosystems are struggling to recover as extreme events are expected to get worse.

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There is growing scientific evidence that heatwaves, floods, droughts and cyclones are increasing in frequency and intensity, and that this is caused by climate change.

Life on the coastline

Corals, seagrass, mangroves and kelp are some of the key habitat-forming species of our coastline, as they all support a host of marine invertebrates, fish, sea turtles and marine mammals.

Our team decided to look at the cumulative impacts of recently reported extreme climate events on marine habitats around Australia. We reviewed the period between 2011 and 2017 and found these events have had devastating impacts on key marine habitats.

Healthy kelp (left) in Western Australia is an important part of the food chain but it is vulnerable to even small changes in temperature and particularly slow to recover from disturbances such as the marine heatwave of 2011. Even small patches or gaps (right) where kelp has died can take many years to recover.
Russ Babcock, Author provided

These include kelp and mangrove forests, seagrass meadows, and coral reefs, some of which have not yet recovered, and may never do so. These findings paint a bleak picture, underscoring the need for urgent action.

During this period, which spanned both El Niño and La Niña conditions, scientists around Australia reported the following events:

2011: The most extreme marine heatwave ever occurred off the west coast of Australia. Temperatures were as much as 2-4℃ above average for extended periods and there was coral bleaching along more than 1,000km of coast and loss of kelp forest along hundreds of kilometres.

Seagrasses in Shark Bay and along the entire east coast of Queensland were also severely affected by extreme flooding and cyclones. The loss of seagrasses in Queensland may have led to a spike in deaths of turtles and dugongs.

2013: Extensive coral bleaching took place along more than 300km of the Pilbara coast of northwestern Australia.

2016: The most extreme coral bleaching ever recorded on the Great Barrier Reef affected more than 1,000km of the northern Great Barrier Reef. Mangrove forests across northern Australia were killed by a combination of drought, heat and abnormally low sea levels along the coast of the Gulf of Carpentaria across the Northern Territory and into Western Australia.

2017: An unprecedented second consecutive summer of coral bleaching on the Great Barrier Reef affects northern Great Barrier Reef again, as well as parts of the reef further to the south.

Heritage areas affected

Many of the impacted areas are globally significant for their size and biodiversity, and because until now they have been relatively undisturbed by climate change. Some of the areas affected are also World Heritage Areas (Great Barrier Reef, Shark Bay, Ningaloo Coast).

Seagrass meadows in Shark Bay are among the world’s most lush and extensive and help lock large amounts of carbon into sediments. The left image shows healthy seagrass but the right image shows damage from extreme climate events in 2011.
Mat Vanderklift, Author provided

The habitats affected are “foundational”: they provide food and shelter to a huge range of species. Many of the animals affected – such as large fish and turtles – support commercial industries such as tourism and fishing, as well as being culturally important to Australians.

Recovery across these impacted habitats has begun, but it’s likely some areas will never return to their previous condition.

We have used ecosystem models to evaluate the likely long-term outcomes from extreme climate events predicted to become more frequent and more intense.

This work suggests that even in places where recovery starts, the average time for full recovery may be around 15 years. Large slow-growing species such as sharks and dugongs could take even longer, up to 60 years.

But extreme climate events are predicted to occur less than 15 years apart. This will result in a step-by-step decline in the condition of these ecosystems, as it leaves too little time between events for full recovery.

This already appears to be happening with the corals of the Great Barrier Reef.

Gradual decline as things get warmer

Damage from extreme climate events occurs on top of more gradual changes driven by increases in average temperature, such as loss of kelp forests on the southeast coasts of Australia due to the spread of sea urchins and tropical grazing fish species.

Ultimately, we need to slow down and stop the heating of our planet due to the release of greenhouse gases. But even with immediate and effective emissions reduction, the planet will remain warmer, and extreme climatic events more prevalent, for decades to come.

Recovery might still be possible, but we need to know more about recovery rates and what factors promote recovery. This information will allow us to give the ecosystems a helping hand through active restoration and rehabilitation efforts.

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We will need new ways to help ecosystems function and to deliver the services that we all depend on. This will likely include decreasing (or ideally, stopping) direct human impacts, and actively assisting recovery and restoring damaged ecosystems.

Several such programs are active around Australia and internationally, attempting to boost the ability of corals, seagrass, mangroves and kelp to recover.

But they will need to be massively scaled up to be effective in the context of the large scale disturbances seen in this decade.

Mangroves at the Flinders River near Karumba in the Gulf of Carpentaria. The healthy mangrove forest (left) is near the river while the dead mangroves (right) are at higher levels where they were much more stressed by conditions in 2016. Some small surviving mangroves are seen beginning to recover by 2017.
Robert Kenyon, Author provided

Russ Babcock, Senior Principal Research Scientist, CSIRO; Anthony Richardson, Professor, The University of Queensland; Beth Fulton, CSIRO Research Group Leader Ecosystem Modelling and Risk Assessment, CSIRO; Eva Plaganyi, Senior Principal Research Scientist, CSIRO, and Rodrigo Bustamante, Research Group Leader , CSIRO

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

Protecting wetlands helps communities reduce damage from hurricanes and storms

Protecting coastal wetlands, like this slough in Florida’s Everglades National Park, is a cost-effective way to reduce flooding and storm damage.
NPS/C. Rivas

Siddharth Narayan, University of California, Santa Cruz and Michael Beck, University of California, Santa Cruz

2017 was the worst year on record for hurricane damage in Texas, Florida and the Caribbean from Harvey, Irma and Maria. We had hoped for a reprieve this year, but less than a month after Hurricane Florence devastated communities across the Carolinas, Hurricane Michael has struck Florida.

Coastlines are being developed rapidly and intensely in the United States and worldwide. The population of central and south Florida, for example, has grown by 6 million since 1990. Many of these cities and towns face the brunt of damage from hurricanes. In addition, rapid coastal development is destroying natural ecosystems like marshes, mangroves, oyster reefs and coral reefs – resources that help protect us from catastrophes.

In a unique partnership funded by Lloyd’s of London, we worked with colleagues in academia, environmental organizations and the insurance industry to calculate the financial benefits that coastal wetlands provide by reducing storm surge damages from hurricanes. Our study, published in 2017, found that this function is enormously valuable to local communities. It offers new evidence that protecting natural ecosystems is an effective way to reduce risks from coastal storms and flooding.

Coastal wetlands and flood damage reduction: A collaboration between academia, conservation and the risk industry.

The economic value of flood protection from wetlands

Although there is broad understanding that wetlands can protect coastlines, researchers have not explicitly measured how and where these benefits translate into dollar values in terms of reduced risks to people and property. To answer this question, our group worked with experts who understand risk best: insurers and risk modelers.

Using the industry’s storm surge models, we compared the flooding and property damages that occurred with wetlands present during Hurricane Sandy to the damages that would have occurred if these wetlands were lost. First we compared the extent and severity of flooding during Sandy to the flooding that would have happened in a scenario where all coastal wetlands were lost. Then, using high-resolution data on assets in the flooded locations, we measured the property damages for both simulations. The difference in damages – with wetlands and without – gave us an estimate of damages avoided due to the presence of these ecosystems.

Our paper shows that during Hurricane Sandy in 2012, coastal wetlands prevented more than US$625 million in direct property damages by buffering coasts against its storm surge. Across 12 coastal states from Maine to North Carolina, wetlands and marshes reduced damages by an average of 11 percent.

These benefits varied widely by location at the local and state level. In Maryland, wetlands reduced damages by 30 percent. In highly urban areas like New York and New Jersey, they provided hundreds of millions of dollars in flood protection.

Wetland benefits for flood damage reduction during Sandy (redder areas benefited more from having wetlands).
Narayan et al., Nature Scientific Reports 7, 9463 (2017)., CC BY

Wetlands reduced damages in most locations, but not everywhere. In some parts of North Carolina and the Chesapeake Bay, wetlands redirected the surge in ways that protected properties directly behind them, but caused greater flooding to other properties, mainly in front of the marshes. Just as we would not build in front of a seawall or a levee, it is important to be aware of the impacts of building near wetlands.

Wetlands reduce flood losses from storms every year, not just during single catastrophic events. We examined the effects of marshes across 2,000 storms in Barnegat Bay, New Jersey. These marshes reduced flood losses annually by an average of 16 percent, and up to 70 percent in some locations.

Reductions in annual flood losses to properties that have a marsh in front (blue) versus properties that have lost the marshes in front (orange).
Narayan et al., Nature Scientific Reports 7, 9463 (2017)., CC BY

In related research, our team has also shown that coastal ecosystems can be highly cost-effective for risk reduction and adaptation along the U.S. Gulf Coast, particularly as part of a portfolio of green (natural) and gray (engineered) solutions.

Reducing risk through conservation

Our research shows that we can measure the reduction in flood risks that coastal ecosystems provide. This is a central concern for the risk and insurance industry and for coastal managers. We have shown that these risk reduction benefits are significant, and that there is a strong case for conserving and protecting our coastal ecosystems.

The next step is to use these benefits to create incentives for wetland conservation and restoration. Homeowners and municipalities could receive reductions on insurance premiums for managing wetlands. Post-storm spending should include more support for this natural infrastructure. And new financial tools such as resilience bonds, which provide incentives for investing in measures that reduce risk, could support wetland restoration efforts too.

The dense vegetation and shallow waters within wetlands can slow the advance of storm surge and dissipate wave energy.
USACE

Improving long-term resilience

Increasingly, communities are also beginning to consider ways to improve long-term resilience as they assess their recovery options.

There is often a strong desire to return to the status quo after a disaster. More often than not, this means rebuilding seawalls and concrete barriers. But these structures are expensive, will need constant upgrades as as sea levels rise, and can damage coastal ecosystems.

Even after suffering years of damage, Florida’s mangrove wetlands and coral reefs play crucial roles in protecting the state from hurricane surges and waves. And yet, over the last six decades urban development has eliminated half of Florida’s historic mangrove habitat. Losses are still occurring across the state from the Keys to Tampa Bay and Miami.

Protecting and nurturing these natural first lines of defense could help Florida homeowners reduce property damage during future storms. In the past two years our team has worked with the private sector and government agencies to help translate these risk reduction benefits into action for rebuilding natural defenses.

Across the United States, the Caribbean and Southeast Asia, coastal communities face a crucial question: Can they rebuild in ways that make them better prepared for the next storm, while also conserving the natural resources that make these locations so valuable? Our work shows that the answer is yes.

This is an updated version of an article originally published on Sept. 25, 2017.

Siddharth Narayan, Postdoctoral Fellow, Coastal Flood Risk, University of California, Santa Cruz and Michael Beck, Research professor, University of California, Santa Cruz

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

Desal plants might do less damage to marine environments than we thought

Some sea creatures are displaced by the desalination plant, but others actually grow.
Supplied

Graeme Clark, UNSW and Emma Johnston, UNSW

Millions of people all over the world rely on desalinated water. Closer to home, Australia has desalination plants in Melbourne, Adelaide, Perth, the Gold Coast, and many remote and regional locations.

But despite the growing size and number of desalination plants, the environmental impacts are little understood. Our six-year study, published recently in the journal Water Research, looked at the health the marine environment before, during and after the Sydney Desalination Plant was operating.

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Fixing cities’ water crises could send our climate targets down the gurgler

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Our research tested the effect of pumping and “diffusing” highly concentrated salt water (a byproduct of desalination) back into the ocean.

Contrary to our expectation that high salt levels would impact sea creatures, we found that ecological changes were largely confined to an area within 100m of the discharge point, and reduced shortly after the plant was turned off. We also found the changes were likely a result of strong currents created by the outfall jets, rather than high salinity.

Desalination is growing

We examined six underwater locations at about 25m depth over a six-year period during which the plant was under construction, then operating, and then idle. This let us rigorously monitor impacts to and recovery of marine life from the effects of pumping large volumes of hypersaline water back into the ocean. We tested for impacts and recovery at two distances (30m and 100m) from the outfall.

This study provides the first before-and-after test of ecological impacts of desalination brine on marine communities, and a rare insight into mechanisms behind the potential impacts of a growing form of human disturbance.

About 1% of the world’s population now depends on desalinated water for daily use, supplied by almost 20,000 desalination plants that produce more than 90 million cubic meters of water per day.

Increasingly frequent and severe water shortages are projected to accelerate the growth in desalination around the world. By 2025, more than 2.8 billion people in 48 countries are likely to experience water scarcity, with desalination expected to become an increasingly crucial water source for many coastal populations.

Effect of the diffusers

The diffusers that pump concentrated salt water into the ocean at a high velocity (to increase dilution) are so effective that salinity was almost at background levels within 100m of the outfall. However, the diffusion process increased the speed of currents close to the outfall.

This strong current affects species differently, depending on how they settle and feed. Marine species with strong swimming larvae, such as barnacles, can easily settle in high flow and then benefit from faster delivery of food particles. These animals increased in number and size near the outfall. In contrast, species with slow swimming larvae, such as tubeworms, lace corals and sponges, prefer settling and feeding in low current and became less abundant near the outfall.

Therefore, the high-pressure diffusers designed to reduce hypersalinity may have inadvertently caused impacts due to flow. However, these ecological changes may be less concerning than those caused by hypersalinity, as the currents were still within the range that marine communities experience naturally.

Our findings are important, because as drought conditions around the nation worsen and domestic water supplies are coming under strain, desalination is starting to ramp up in eastern and southern Australia.

For instance, water levels at Sydney’s primary dam at Warragamba have dropped to around 65% and the desalination plant is contracted to start supplying drinking water back into the system when dam levels fall below 60%. This plant can potentially double in capacity if needed.

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Read more:
Melbourne’s desalination plant is just one part of drought-proofing water supply

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There is a rapid expansion of the use of desalination, with global capacity increasing by 57% between 2008 and 2013. Our results will help designers and researchers in this area ensure desalination plants minimise their effect on local coastal systems.

Graeme Clark, Senior Research Associate in Ecology, UNSW and Emma Johnston, Professor and Dean of Science, UNSW

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

Banning fishing has helped parts of the Great Barrier Reef recover from damage

Camille Mellin, Australian Institute of Marine Science; Aaron MacNeil, Australian Institute of Marine Science, and Julian Caley, Australian Institute of Marine Science

The world’s coral reefs face unprecedented threats. Their survival depends on how well they can cope with a long list of pressures including fishing, storms, coral bleaching, outbreaks of coral predators and reduced water quality. Together, these disturbances have caused the Great Barrier Reef to lose half of its coral cover since 1985.

One often-used way of protecting marine ecosystems is to close parts of the ocean to fishing, in no-take marine reserves. From research, we know that by reducing fishing you end up with more and bigger fish (and other harvested species such as lobsters).

But other benefits of protection might be more surprising. In a new study, we show that no-take reserves helped the Great Barrier Reef’s corals to resist a range of disturbances, such as bleaching, disease and crown-of-thorns starfish, and to recover more quickly from damage.

More exposure, but better protection

Our study used observations between 1993 and 2013 of 34 types of coral and invertebrates and 215 fish species on 46 reefs spread across the Great Barrier Reef. Among the 46 study reefs, 26 were open to fishing and 20 were in no-take marine reserves.

During the study period, several occurrences of coral bleaching, coral disease, storms and outbreaks of crown-of-thorns starfish were recorded.

The total number of disturbances affecting our study reefs increased in recent years (2010-12), mostly due to severe storms affecting the central and southern sections of the Great Barrier Reef. Among our study reefs, those located inside no-take marine reserves were more exposed to disturbance than those outside no-take marine reserves.

Our study showed that, inside no-take marine reserves, the impact of disturbance was reduced by 38% for fish and by 25% for corals compared with unprotected reefs. This means that no-take marine reserves benefit not only fish but entire reef communities, including corals, and might help to slow down the rapid degradation of coral reefs.

Damaged coral reef around Lizard Island a few days after cyclone Ita.
Photo by Tom Bridge, http://www.tethys-images.com

Faster recovery

In addition to greater resistance, reef organisms recovered more quickly from disturbance inside no-take marine reserves. After each disturbance, we measured the time that both coral and fish communities took to return to their pre-disturbance state.

We found coral communities took the longest to recover after crown-of-thorns starfish outbreaks. Outside no-take marine reserves, it took on average nine years for these communities to recover. It took just over six years inside no-take marine reserves.

Although there is more work to be done, one reason that reefs inside no-take zones are able to cope better with disturbances is that they preserve and promote a wider range of important ecological functions. Where fishing reduces the numbers of some species outside protected areas, some of these functions could be lost.

Coral reef showing signs of recovery.
Photo copyright Tom Bridge/www.tethys-images.com

Knowledge for conservation

Marine reserves (including no-take zones) currently cover 3.4% of the world’s ocean, which is still well below the 10% target for 2020 recommended by the Convention on Biological Diversity. The slow progress towards this target is partly due to the perceived high costs of protection compared to true ecological benefits, which can be difficult to gauge. While some surprising benefits are beginning to be revealed in studies like ours, such benefits remain little understood.

Our results help to fill that gap by showing that no-take marine reserves can boost both the resistance and recovery of reef communities following disturbance. In ecology, resistance plus recovery equals resilience.

Our work suggests that the net benefit of no-take marine reserves is much greater than previously thought. No-take marine reserves host not only more and bigger fishes, but more resilient communities that might decline at slower rates.

These results reinforce the idea that no-take marine reserves should be widely implemented and supported as a means of maintaining the integrity of coral reefs globally.

Our conclusions also demonstrate that we need long-term monitoring programs which provide a unique opportunity to assess the sustained benefits of protection.

Camille Mellin, Research Scientist, Australian Institute of Marine Science; Aaron MacNeil, Senior Research Scientist, Australian Institute of Marine Science, and Julian Caley, Senior Principal Research Scientist, Australian Institute of Marine Science

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

Australia: New South Wales – Sugarloaf State Conservation Area Mining Damage

The link below is to an article reporting on the mine subsidence disaster in the Sugarloaf State Conservation Area of New South Wales, Australia.

For more visit:
http://www.theherald.com.au/story/1743298/mine-subsidence-rehab-credibility-mess-video/

Media Release: Stockton Bight

The link below is to a media release concerning damage to a midden at Stockton Bight in New South Wales, Australia.

For more visit:
http://www.environment.nsw.gov.au/media/OEHmedia13080101.htm