$60 million to save the Great Barrier Reef is a drop in the ocean, but we have to try

David Suggett, University of Technology Sydney

The Great Barrier Reef has never faced such a dire future. Amid increasingly doom-laden headlines, the federal government this week unveiled a recovery package aimed at securing the reef’s prospects. The question is whether this is indeed a rescue, or just a smokescreen of false hope.

The A$60 million package will be split between various projects:

  • A$36.6 million will be spent on reducing the runoff of land-based agricultural fertilisers and pesticides onto the reef

  • A$10.4 million will go towards an “all-out assault” on the coral-eating crown-of-thorns starfish

  • A$4.9 million will fund improved monitoring and early warning of issues such as mass bleaching

  • A$6 million will be spent on a new national Reef Restoration and Adaptation program.

But what return can we expect for this A$60 million investment, which is only 0.1% of the A$56 billion estimated economic value of the Great Barrier Reef?

Value for money

At face value, splitting the funding across several priority areas seems logical. Many local stressors, from pollution to overfishing, affect the Great Barrier Reef in different ways and in different places, so tackling them locally seems like a nice direct way to intervene.

But here’s the problem: these stressors interact and amplify each others’ effects. This means that spreading the money so thinly is a risky move, because successfully tackling any one problem rests on successfully tackling all the others.

Crown-of-thorns starfish is a great example. Even if we can remove or destroy them in sufficient numbers to make a difference, their populations will simply bounce back unless we also reduce the agricultural pollution that feeds their larvae. Alongside this, we need to ensure that their natural predators such as the giant triton mollusc also thrive.

Local impacts on the Great Barrier Reef are also amplified by global climate factors, such as the warming and increased ocean acidity caused by rising atmospheric carbon dioxide levels.

Focusing purely on local issues risks diverting attention from this wider problem. The unprecedented back-to-back mass bleaching that catastrophically damaged the Great Barrier Reef in 2016 and 2017 was a direct result of global climate change.

Preventing this from accelerating further requires global and collective
action on greenhouse gas emission reductions. As custodian of the Great Barrier Reef, as well as a major coal exporter and a signatory to the Paris Climate Agreement, Australia has a responsibility to lead from the front to find alternatives to fossil fuels.

For this reason, the new funding package has unsurprisingly been criticised for not attempting to “cure” the ultimate problem that ails the Great Barrier Reef. Local interventions such as the ones being funded are often called out for being band-aid solutions. But the reality is that we need band-aids more than ever – although perhaps “tourniquets” would be more apt.

Cutting emissions and curbing climate change must remain our absolute priority.
However, even relatively optimistic emissions reduction scenarios will leave us
with warmer and acidic reefs for the coming decades. This means we will have to think well outside the box if we are to ensure that the Barrier Reef stays great. We cannot deny treatment while we attempt to find the cure.

Read more:
The Great Barrier Reef can repair itself, with a little help from science

The problem is that most current local reef interventions are considered too risky or too expensive, and are therefore dismissed without trying them. But unless we try alternatives, and are prepared to learn by trial and error, how can we find the solutions that work? What the government’s new package ultimately therefore provides is the incentive to innovate.

In this sense it follows parallel calls from the Queensland government to find new ways to boost coral abundance. As such, the federal funding may only be successful if we ensure that the proposed investment focuses on tackling the priority areas in new ways, rather than simply scaling up the current efforts.

As the stress builds on the Great Barrier Reef, one thing is certain: its future will depend on maximising its resilience. This necessarily calls for a range of efforts, focusing on biology, ecosystems, and changing human behaviour – not just defaulting to a single solution. Intensifying efforts to harness corals that are already adapted to extreme conditions will likely be crucial.

The ConversationAnd of course, all of this will count for nothing unless we also take parallel action to tackle the underlying problem: climate change.

David Suggett, Associate Professor in Marine Biology, University of Technology Sydney

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


How can we halt the feminisation of sea turtles in the northern Great Barrier Reef?

Ana Rita Patricio, University of Exeter

In the northern part of Australia’s Great Barrier Reef, the future for green sea turtles appears to be turning female.

A recent study has revealed that climate change is rapidly leading to the feminisation of green turtles in one of the world’s largest populations. Only about 1% of these juvenile turtles are hatching male.

Read more: What does climate change mean for sea turtles?

Among sea turtles, incubation temperatures above 29ºC produce more female offspring. When incubation temperatures approach 33ºC, 100% of the offspring are female. Cooler temperatures yield more males, up to 100% near a lower thermal limit of 23ºC. And if eggs incubate at temperatures outside the range of 23-33ºC the risk of embryo malformation and mortality becomes very high.

As current climate change models foresee increases in average global temperature of 2 to 3ºC by 2100, the future for these turtles is in danger. Worryingly, warmer temperatures will also lead to ocean expansion and sea-level rise, increasing the risk of flooding of nesting habitats.

How scientists are tackling the problem

Green sea turtles’ sensitivity to incubation temperatures is such that even a few degrees can dramatically change the sex ratio of hatchlings.

Sea turtles are particularly vulnerable because they have temperature-dependent sex determination, or TSD, meaning that the sex of the offspring depends on the incubation temperature of the eggs. This is the same mechanism that determines the sex of several other reptile species, such as the crocodilians, many lizards and freshwater turtles.

Scientists and conservationists are well aware of how future temperatures may threaten these species. For the past two decades they have been investigating the incubation conditions and resulting sex ratios at several sea turtle nesting beaches worldwide.

This is mostly done using temperature recording devices (roughly the size of an egg). These are placed inside nest chambers among the clutch of eggs, or buried in the sand at the same depth as the eggs. When a clutch hatches (after 50 to 60 days) the device is recovered and the temperatures recorded are analysed.

Research has revealed that most nesting beaches studied to date have sand temperatures that favour female hatchling production. But this female bias is not immediately a bad thing, because male sea turtles can mate with several females (polygyny). So having more females actually enhances the reproductive potential of a population (i.e. more females equals more eggs).

But given that climate change will likely soon increase this female bias, important questions arise. How much of a female bias is OK? Will there be enough males? What is the minimum proportion of males to keep a sustainable population?

These questions are being investigated. But, in the meantime, alarming reports of populations with more than 99% of hatchlings being female stress the urgency of science-based management strategies. These strategies must be designed to promote (or maintain) cooler incubation temperatures at key nesting beaches to prevent population decline or even extinction.

The challenge of reversing feminisation

There are two general approaches to the problem:

  1. mitigate impacts at the most endangered nesting beaches
  2. identify and protect sites that naturally produce higher proportions of males.

Several studies emphasise that the natural shading native vegetation provides is essential to maintain cooler incubation temperatures. Thus, a key conservation action is to protect beach vegetation, or reforest nesting beaches.

Coastal vegetation also protects the nesting beach against wave erosion during storms, which will worsen under climate change. This strategy further requires coastal development to allow for buffer zones. Construction setback regulations should be enforced or implemented.

When natural shading is not an option, clutches of eggs can be moved either to more suitable beaches, or to hatcheries with artificial shading. Researchers have tested the use of synthetic shade cloth and found it is effective in reducing sand and nest temperatures.

Other potential strategies involve adding light-coloured sand on top of nests. This can help by absorbing less solar radiation (heat) compared to darker sand. Beach sprinklers have also been tested to simulate the cooling effect of rainfall.

The effectiveness of these actions has yet to be fully tested, but there is concern about some potential negative side effects. For example, excess water from sprinklers may cause fungal infections on eggs.

Finally, as much as mitigation measures are important, these are always short-term solutions. In the long run, prevention is always the best strategy, i.e. protecting the nesting beaches that currently produce more males from deforestation, development and habitat degradation.

Our recent research on the largest green turtle population in Africa reports unusually high male hatchling production. We found almost balanced hatchling sex ratios (1 female to 1.2 males). We attributed this mostly to the cooling effect of the native forest.

This, and similar nesting beaches, should be designated as priority conservation sites, as they will be key to ensuring the future of sea turtles under projected global warming scenarios.

Sea turtles face an uncertain future

Sea turtles are resilient creatures. They have been around for over 200 million years, surviving the mass extinction that included the dinosaurs, and enduring dramatic climatic changes in the past.

There is potential for these creatures to adapt, as they did before. This could be through, for example, shifting the timing of nesting to cooler periods, changing their distribution to more suitable habitats, or evolution of critical incubation temperatures that produce males.

Read more: Turtle hatchlings lend each other a flipper to save energy

But the climate today is changing at an unprecedented rate. Along with the feminisation of these turtles in the northern Great Barrier Reef, sea turtles globally face many threats from humans. These include problems associated with by-catch, poaching, habitat degradation and coastal development, plus a history of intense human exploitation.

The ConversationIn 2018, the prevalence of these species depends now more than ever on the effectiveness of conservation measures.

Ana Rita Patricio, Postdoctoral research fellow, University of Exeter

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

It’s official: 2016’s Great Barrier Reef bleaching was unlike anything that went before

Sophie Lewis, Australian National University and Jennie Mallela, Australian National University

It is no longer news that the Great Barrier Reef has suffered extreme bleaching.

In early 2016, we heard that the reef had suffered the worst bleaching ever recorded. Surveys published in June that year estimated that 93% of coral on the vast northern section of the reef was bleached, and 22% had already been killed.

Further reports from this year show that bleaching again occurred. The back-to-back bleaching hit more than two-thirds of the Great Barrier Reef and may threaten its UNESCO World Heritage listing.

After recent years of damage, what does the future hold for our priceless reef?

Our new research, published in the Bulletin of the American Meteorological Society’s special report on climate extremes, shows the news isn’t good for the Great Barrier Reef’s future.

Read more: How to work out which coral reefs will bleach, and which might be spared

Coral reefs are complex ecosystems that are affected by many factors. Changes in sea surface temperatures, rainfall, cloudiness, agricultural runoff, or water quality can affect a reef’s health and resilience to stress.

Early analysis of the 2016 bleaching suggested that the Great Barrier Reef was suffering from thermal stress brought on by human-caused climate change.

Our study took a new and comprehensive approach to examine these multiple climatic and environmental influences.

We set out to answer the crucial question: could anything else have bleached the Great Barrier Reef, besides human-induced climate change?

Clear fingerprint

The results were clear. Using a suite of climate models, we found that the significant warming of the Coral Sea region was likely caused by greenhouse gases from human activities. This warming was the primary cause of the extreme 2016 bleaching episode.

But what about those other complex factors? The 2016 event coincided with an El Niño episode that was among the most severe ever observed. The El Niño-Southern Oscillation system, with its positive El Niño and negative La Niña phases, has been linked to bleaching of various coral reefs in the past.

Our study showed that although the 2016 El Niño probably also contributed to the bleaching, this was a secondary contributor to the corals’ thermal stress. The major factor was the increase in temperatures because of climate change.

We next analysed other environmental data. Previous research has found that corals at sites with better water quality (that is, lower concentrations of pollution particles) are more resilient and less prone to bleaching.

Pollution data used in our study show that water quality in 2016 may have been better than in previous bleaching years. This means that the Great Barrier Reef should have been at lower risk of bleaching compared to long-term average conditions, all else being equal. Instead, record bleaching hit the reef as a result of the warming temperature trend.

Previous events

The final part of our investigation involved comparing the conditions behind the record 2016 bleaching with those seen in previous mass bleaching episodes on the Great Barrier Reef, in 1997-98 and 2010-11.

When we analysed these previous events on the Reef, we found very different factors at play.

In 1997-98 the bleaching coincided with a very strong El Niño event. Although an El Niño event also occurred in 2016, the two were very different in terms of the distribution of unusually warm waters, particularly in the eastern equatorial Pacific. In 1997-98, the primary cause of the bleaching – which was less severe than in 2016 – was El Niño.

In 2010-11, the health of the Great Barrier Reef was impaired by runoff. That summer brought record high rainfall to eastern Australia, causing widespread flooding across Queensland. As a result of the discharge of freshwater onto the reef reducing the salinity, bleaching occurred.

Read more: Feeling helpless about the Great Barrier Reef? Here’s one way you can help

There have been many reports in recent years warning of trouble for the Great Barrier Reef. Sadly, our study is yet another warning about the reef’s future – perhaps the most comprehensive warning yet. It tells us that the 2016 bleaching differed from previous mass bleaching events because it was driven primarily by human-induced climate warming.

This puts the Great Barrier Reef in grave danger of future bleaching from further greenhouse warming. The local environmental factors that have previously helped to protect our reefs, such as good water quality, will become less and less able to safeguard corals as the oceans warm.

The ConversationNow we need to take immediate action to reduce greenhouse gas emissions and limit further warming. Without these steps, there is simply no future for our Great Barrier Reef.

Sophie Lewis, Research fellow, Australian National University and Jennie Mallela, Research Fellow in Coral Reef Monitoring and Reef Health Appraisal, Australian National University

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

How we found 112 ‘recovery reefs’ dotted through the Great Barrier Reef

File 20171129 28869 lod9mh.jpg?ixlib=rb 1.1
Some reefs are strong sources of coral larvae.
Peter Mumby, Author provided

Peter J Mumby, The University of Queensland

The Great Barrier Reef is better able to heal itself than we previously imagined, according to new research that identifies 112 individual reefs that can help drive the entire system towards recovery.

The back-to-back bleaching events in 2016 and 2017 that killed many corals on the Great Barrier Reef have led many researchers to ask whether and how it can recover. Conventionally, we tend to focus on what controls recovery on individual reefs – for example, whether they are fouled by seaweed or sediments.

But in our study, published in PLoS Biology, my colleagues and I stepped back to view the entire Great Barrier Reef as a whole entity and ask how it can potentially repair itself.

Read more: The Great Barrier Reef can repair itself, with a little help from science

We began by asking whether some reefs are exceptionally important for kick-starting widespread recovery after damage. To do this we set three criteria.

First, we looked for reefs that are major sources of coral larvae – the ultimate source of recovery. Every year corals engage in one of nature’s greatest spectacles, their mass reproduction during a November full moon. Fertilised eggs (larvae) travel on ocean currents for days or weeks in search of a new home.

With our partners at the CSIRO we’ve been able to model where these larvae go, and therefore the “connectivity” of the reef. By using this modelling (the Great Barrier Reef is far too large to observe this directly), we looked for reefs that strongly and consistently supply larvae to many other reefs.

Healthy reefs supply far more larvae than damaged ones, so our second criterion was that reefs should have a relatively low risk of being impacted by coral bleaching. Using satellite records of sea temperature dating back to 1985, we identified reefs that have not yet experienced the kind of temperature that causes mass coral loss. That doesn’t mean these reefs will never experience bleaching, but it does mean they have a relatively good chance of surviving at least for the foreseeable future.

Our final criterion was that reefs should supply coral larvae but not pests. Here we focused on the coral-eating crown-of-thorns starfish, whose larvae also travel on ocean currents. We know that outbreaks of these starfish tend to begin north of Cairns, and from that we can predict which reefs are most likely to become infested over time.

Fortunately, many good sources of coral larvae are relatively safe from crown-of-thorns starfish, particularly those reefs that are far offshore and bathed in oceanic water from the Coral Sea rather than the currents that flow past Cairns. Indeed, the access to deep – and often cooling – ocean water helps moderate temperature extremes in these outer reefs, which also reduces the risk of bleaching in some areas.

Using these three criteria, we pinpointed 112 reefs that are likely to be important in driving reef recovery for the wider system. They represent only 3% of the reefs of the Great Barrier Reef, but are so widely connected that their larvae can reach 47% of all the reefs within a single summer spawning season.

Unfortunately, their distribution across the reef is patchy. Relatively few are in the north (see map) so this area is relatively vulnerable.

Black dots show reefs identified as strong sources of coral larvae; grey dots show other reefs.
Hock et al., PLoS Biol.

Our study shows that reefs vary hugely, both in their exposure to damage and in their ability to contribute to the recovery of corals elsewhere. Where these patterns are pretty consistent over time – as is the case for the reefs we identified – it makes sense to factor this information into management planning.

It would be sensible to improve surveillance of these particular reefs, to check that crown-of-thorns starfish do not reach them, and to eradicate the starfish if they do.

To be clear, these are not the only reefs that should be managed. The Great Barrier Reef already has more than 30% of its area under protection from fishing, and many of its other individual reefs are important for tourism, fisheries and cultural benefits.

But the point here is that some reefs are far more important for ecosystem recovery than others. Factoring these patterns into tactical management – such as how best to respond in the aftermath of a cyclone strike – is the next step. It’s a need that has been articulated repeatedly by the Great Barrier Reef Marine Park Authority.

Read more: Coal and climate change: a death sentence for the Great Barrier Reef

Taking the long-term view, the greatest threats to the reef are rising sea temperatures and ocean acidification caused by elevated carbon dioxide levels. This is clearly a challenge for humanity and one that requires consistent policies across governments.

But local protection is vital in order to maintain the reef in the best state possible given the global environment. Actions include improvements to the quality of the water emerging from rivers, controlling crown-of-thorns starfish, and maintaining healthy fish populations.

The ConversationThis is an expensive process and resources need to be deployed as effectively as possible. Our results help target management effectively by revealing the underlying mechanisms of repair on the reef. If management can help protect and facilitate corals’ natural processes of recovery, this might go a long way towards sustaining the Great Barrier Reef in an already challenging environment.

Peter J Mumby, Chair professor, The University of Queensland

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

Is it too cheap to visit the ‘priceless’ Great Barrier Reef?

File 20171016 27708 hx6tj4.jpg?ixlib=rb 1.1
Would you pay more if you thought it would help?
Wikimedia Commons, CC BY-SA

Michael Vardon, Australian National University

The Great Barrier Reef is one of the world’s finest natural wonders. It’s also extraordinarily cheap to visit – perhaps too cheap.

While a visit to the reef can be part of an expensive holiday, the daily fee to enter the Great Barrier Reef Marine Park itself is a measly A$6.50. In contrast, earlier this year I was lucky enough to visit Rwanda’s mountain gorillas and paid a US$750 fee, and the charge has since been doubled to US$1,500.

To me, seeing the reef was better than visiting the gorillas. Personally, I would be happy to pay more to visit the Great Barrier Reef. Does this mean we’re undervaluing our most important natural wonder? And if we do ask visitors to pay a higher price, would it actually help the reef or simply harm tourism numbers?

Read more: Money can’t buy me love, but you can put a price on a tree

Putting dollar values on the natural world can be a heated topic. Earlier this year Deloitte Access Economics valued the Great Barrier Reef at A$56 billion “as an Australian economic, social and iconic asset”, but was met with the retort that its true value is priceless.

The A$56 billion estimate was based on surveys that measured “consumer surplus and non-use benefits”. This common research technique involves asking people what they would be willing to pay to get a particular benefit. For example, the entrance fee for the reef is A$6.50 but if I am willing to pay A$50 (say), that equates to a consumer surplus of A$43.50. In other words, I am receiving A$43.50 worth of value that I did not have to pay for.

I understand that some people instinctively object to the idea of trying to put monetary values on things like the Great Barrier Reef. But I think valuation helps, on balance, because it offers a way to assimilate environmental information into the economic processes through which most decisions are made. Money makes the world go around, after all.

However this should be done on the proviso that the valuation is systematic and based on sound environmental and economic data.

Accounting for the Great Barrier Reef

The process by which these values are calculated is called “environmental accounting”, and estimates have to meet international standards known as the System of Environmental-Economic Accounting or SEEA in order to be valid. This builds on the System of National Accounts (which among many other things gives us the GDP indicator). In this accounting, as in business accounting, the values recorded are exchange values – that is, what someone paid (or was likely to pay) for a good, service or asset. For assets that aren’t regularly traded, this figure can be based on either previous sales or expected future income.

It does not use willingness-to-pay measures. The Deloitte report also estimated exchange values in line with accounting values, with the Great Barrier Reef contributing A$6.4 billion to the economy through tourism, fishing, recreation, and research and scientific management.

The Australian Bureau of Statistics has a huge amount of data on the Great Barrier Reef, covering the physical state of the reef and its surroundings, the economic activity occurring in the region, and more besides.

Unsurprisingly, tourism is the region’s most valuable industry, contributing A$3.8 billion in gross value added in 2015-16 (see Table 1 here). That year the Marine Park had 2.3 million visitors, who together paid just under A$9 million in park entry charges (see Table 4 here).

Ecosystem services are the contributions of the natural world to benefits enjoyed by people. For example, farmers grow crops that are pollinated by insects and use nutrients found in the soil. These things are not explicitly paid for, but by examining economic transactions we can estimate their value.

Surprisingly, the value of ecosystem services used by tourism was A$600 million – just half the value of the ecosystem services used by the agriculture industry.

Value of ecosystem services (in millions of dollars) used by selected industries in the Great Barrier Reef Region in 2014-15.

The result is partly explained by the way things are valued. Agricultural products are bought and sold in markets, whereas the Great Barrier Reef is a public asset and the fee for visiting it is set by governments, not by a market.

On these numbers, paying A$6.50 to visit one of the great treasures of the world is a bargain indeed. But what does it mean for the reef itself?

Reef under threat

The reef is under pressure from many factors, including climate change, nutrient runoff, tourism impacts, and fishing. Managing the pressure requires resources, and it makes sense to ask those who use it to pay for it.

Increased funding to help manage these pressures would therefore be good. What’s more, governments could conceivably also use natural resources to generate money to fund other public goods and services, such as roads, education, health, defence, and so on.

Before you protest at this idea, ask yourself: why should the Great Barrier Reef not be used to generate revenue for government? Other natural resources are used this way. The federal and Queensland governments are pursuing economic benefits from the coal in the nearby Galilee Basin. If government revenue from the Great Barrier Reef were increased, it might reduce the need for revenue from elsewhere.

So what next?

Environmental accounting offers a clear way to assess such trade-offs, and will hopefully lead to better decisions. To achieve this we will need:

  • Regular environmental-economic accounts from trusted institutions like the ABS
  • Governments and business to incorporate this new accounting into their strategic planning and management (including, in the case of the Great Barrier Reef, assessing the likely revenue from increased marine park fees)
  • The public to use the accounts to hold our government and business leaders to

The ConversationThe last will no doubt make some uncomfortable, while the second will take some time. The first is already a reality. I hope others take the time to understand and analyse the accounts already available, and that we get as much debate about managing the environment as we do about managing the economy.

Michael Vardon, Visiting Fellow at the Fenner School, Australian National University

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

The Great Barrier Reef can repair itself, with a little help from science

File 20171008 32184 1wf4zmb.jpg?ixlib=rb 1.1
How the Great Barrier Reef can be helped to help repair the damaged reef.
AIMS/Neal Cantin, CC BY-ND

Ken Anthony, Australian Institute of Marine Science; Britta Schaffelke, Australian Institute of Marine Science; Line K Bay, Australian Institute of Marine Science, and Madeleine van Oppen, Australian Institute of Marine Science

The Great Barrier Reef is suffering from recent unprecedented coral bleaching events. But the answer to part of its recovery could lie in the reef itself, with a little help.

In our recent article published in Nature Ecology & Evolution, we argue that at least two potential interventions show promise as means to boost climate resilience and tolerance in the reef’s corals: assisted gene flow
and assisted evolution.

Both techniques use existing genetic material on the reef to breed hardier corals, and do not involve genetic engineering.

But why are such interventions needed? Can’t the reef simply repair itself?

Damage to the reef, so far

Coral bleaching in 2016 and 2017 took its biggest toll on the reef to date, with two-thirds of the world’s largest coral reef ecosystem impacted in these back-to-back events. The consequence was widespread damage.

Bleached corals on the central Great Barrier Reef at the peak of the heat wave in March 2017. Most branching corals in the photo were dead six months later.
Neal Cantin/AIMS, CC BY-ND

Reducing greenhouse gas emissions will dampen coral bleaching risk in the long term, but will not prevent it. Even with strong action to tackle climate change, more warming is locked in.

So while emissions reductions are essential for the future of the reef, other actions are now also needed.

Even in the most optimistic future, reef-building corals need to become more resilient. Continued improvement of water quality, controlling Crown-of-Thorns Starfish, and managing no-take areas will all help.

But continued stress from climate change – in frequency and intensity – increasingly overwhelms the natural resilience despite the best conventional management efforts. Although natural processes of adaptation and acclimation are in play, they are unlikely to be fast enough to keep up with any rate of global warming.

So to boost the reef’s resilience in the face of climate change we need to consider new interventions – and urgently.

That’s why we believe assisted gene flow and assisted evolution could help the reef.

Delaying their development could mean that climate change degrades the reef beyond repair, and before we can save key species.

What is assisted gene flow?

The idea here is to move warm-adapted corals to cooler parts of the reef. Corals in the far north are naturally adapted to 1C to 2C higher summer temperatures than corals further south.

This means there is an opportunity to build resistance to future warming in corals in the south under strong climate change mitigation, or to decades of warming under weaker mitigation.

There is already natural genetic connectivity of coral populations across most of the reef. But the rate of larval flow from the warm north to the south is limited, partly because of the South Equatorial Current that flows west across the Pacific.

The South Equatorial Current splits into the north-flowing Gulf of Papua Current and south-flowing East Australian Current off the coast of north Queensland. This means coral larvae spawned in the warm north are often more likely to stay in the north.

So manually moving some of the northern corals south could help overcome that physical limitation of natural north-to-south larval flow. If enough corals could be moved it could help heat-damaged reefs recover faster with more heat-resistant coral stock.

We could start safe tests at a subset of well-chosen reefs to understand how warm-adapted populations can be spread to reefs further south.

These two-year old corals reared in AIMS’s National Sea Simulator are hybrids between different species of the genus Acropora. They are the results of artificial selection under experimental climate change and show tolerance to prolonged heat stress expected in the future.
Neal Cantin/AIMS, CC BY-ND

What is assisted evolution?

While assisted gene flow may be effective for southern or recently degraded reefs, it will not be enough or feasible for all reefs or species. Here, we argue that assisted evolution could help.

Assisted evolution is artificial selection on steroids. It combines multiple approaches that target the coral host and its essential microbial symbionts.

These are aimed at producing a hardier coral without the use of genetic engineering. Experiments at the Australian Institute of Marine Science are already making progress, with results yet to be published.

First, evolution of algal symbionts in isolation from the coral host has been fast-tracked to resist higher levels of heat stress. When symbionts are made to reengage with the coral host, benefits to bleaching resistance are still small, but with more work we expect to see a hardier symbiosis.

Secondly, experiments have created new genetic diversity of corals through hybridisation and researchers have selected these artificially for increased climate resilience.

Natural hybridisation happens only occasionally on the reef, so this result gives us new options for climate hardening corals using existing genetic stocks.

The danger of doing nothing?

The right time to start any new intervention is when the risk of inaction is greater than the risk of action.

Assisted gene flow and assisted evolution represent manageable risk because they use genetic material already present on the reef. The interventions speed up naturally occurring processes and do not involve genetic engineering.

Read more: Back-to-back bleaching has now hit two-thirds of the Great Barrier Reef

These interventions would not introduce or produce new species. Assisted gene flow would simply enhance the natural flow of warm-adapted corals into areas on the reef that desperately need more heat tolerance.

Risk of increasing the spread of diseases may also be low because most parts of the Reef are already interconnected. A full understanding of risks is an area of continued research.

The ConversationThese are just two examples of new tools that could help build climate resilience on the reef. Other interventions are developing and should be put on the table for open discussion.

Ken Anthony, Principal Research Scientist, Australian Institute of Marine Science; Britta Schaffelke, Research Program Leader – A Healthy and Sustainable Great Barrier Reef, Australian Institute of Marine Science; Line K Bay, Senior Research Scientist and Team Leader, Australian Institute of Marine Science, and Madeleine van Oppen, Marine molecular ecologist, Australian Institute of Marine Science

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

How to work out which coral reefs will bleach, and which might be spared

Clothilde Emilie Langlais, CSIRO; Andrew Lenton, CSIRO, and Scott Heron, National Oceanic and Atmospheric Administration

Regional variations in sea surface temperature, related to seasons and El Niño, could be crucial for the survival of coral reefs, according to our new research. This suggests that we should be able to identify the reefs most at risk of mass bleaching, and those that are more likely to survive unscathed.

Healthy coral reefs support diverse ecosystems, hosting 25% of all marine fish species. They provide food, coastal protection and livelihoods for at least 500 million people.

But global warming, coupled with other pressures such as nutrient and sediment input, changes in sea level, waves, storms, ventilation, hydrodynamics, and ocean acidification, could lead to the end of the world’s coral reefs in a couple of decades.

Read more: How much coral has died in the Great Barrier Reef’s worst bleaching event?

Climate warming is the major cause of stress for corals. The world just witnessed an event described as the “longest global coral die-off on record”, and scientists have been raising the alarm about coral bleaching for decades.

The first global-scale mass bleaching event happened in 1998, destroying 16% of the world coral reefs. Unless greenhouse emissions are drastically reduced, the question is no longer if coral bleaching will happen again, but when and how often?

To help protect coral reefs and their ecosystems, effective management and conservation strategies are crucial. Our research shows that understanding the relationship between natural variations of sea temperature and human-driven ocean warming will help us identify the areas that are most at risk, and also those that are best placed to provide safe haven.

A recurrent threat

Bleaching happens when sea temperatures are unusually high, causing the corals to expel the coloured algae that live within their tissues. Without these algae, corals are unable to reproduce or to build their skeletons properly, and can ultimately die.

The two most devastating global mass bleaching events on record – in 1998 and 2016 – were both triggered by El Niño. But when water temperatures drop back to normal, corals can often recover.

Certain types of coral can also acclimatise to rising sea temperatures. But as our planet warms, periods of bleaching risk will become more frequent and more severe. As a consequence, corals will have less and less time to recover between bleaching events.

We are already witnessing a decline in coral reefs. Global populations have declined by 1-2% per year in response to repeated bleaching events. Closer to home, the Great Barrier Reef lost 50% of its coral cover between 1985 and 2012.

A non-uniform response to warming

While the future of worldwide coral reefs looks dim, not all reefs will be at risk of recurrent bleaching at the same time. In particular, reefs located south of 15ºS (including the Great Barrier Reef, as well as islands in south Polynesia and Melanesia) are likely to be the last regions to be affected by harmful recurrent bleaching.

We used to think that Micronesia’s reefs would be among the first to die off, because the climate is warming faster there than in many other places. But our research, published today in Nature Climate Change, shows that the overall increase in temperature is not the only factor that affects coral bleaching response.

In fact, the key determinant of recurrent bleaching is the natural variability of ocean temperature. Under warming, temperature variations associated with seasons and climate processes like El Niño influence the pace of recurrent bleaching, and explain why some reefs will experience bleaching risk sooner than others in the future.

Different zones of the Pacific are likely to experience differing amounts of climate variability.
Author provided
Degrees of future bleaching risk for corals in the three main Pacific zones.
Author provided

Our results suggest that El Niño events will continue to be the major drivers of mass bleaching events in the central Pacific. As average ocean temperatures rise, even mild El Niño events will have the potential to trigger widespread bleaching, meaning that these regions could face severe bleaching every three to five years within just a few decades. In contrast, only the strongest El Niño events will cause mass bleaching in the South Pacific.

In the future, the risk of recurrent bleaching will be more seasonally driven in the South Pacific. Once the global warming signal pushes summer temperatures to dangerously warm levels, the coral reefs will experience bleaching events every summers. In the western Pacific, the absence of natural variations of temperatures initially protects the coral reefs, but only a small warming increase can rapidly transition the coral reefs from a safe haven to a permanent bleaching situation.

Read more: Feeling helpless about the Great Barrier Reef? Here’s one way you can help

One consequence is that, for future projections of coral bleaching risk, the global warming rate is important but the details of the regional warming are not so much. The absence of consensus about regional patterns of warming across climate models is therefore less of an obstacle than previously thought, because globally averaged warming provided by climate models combined with locally observed sea temperature variations will give us better projections anyway.

The ConversationUnderstanding the regional differences can help reef managers identify the reef areas that are at high risk of recurring bleaching events, and which ones are potential temporary safe havens. This can buy us valuable time in the battle to protect the world’s corals.

Clothilde Emilie Langlais, research scientist at CSIRO Oceans and Atmosphere, CSIRO; Andrew Lenton, Senior Research Scientist, Oceans and Atmosphere, CSIRO, and Scott Heron, Physical Scientist, National Oceanic and Atmospheric Administration

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