South-East Queensland is droughtier and floodier than we thought



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South-East Queensland residents need to prepare for more regular floods, according to new data.
Shutterstock

Jack Coates-Marnane, Griffith University; Joanne Burton, Griffith University; John Tibby, University of Adelaide; Jon Olley, Griffith University; Joseph M. McMahon, Griffith University, and Justine Kemp, Griffith University

New data recording the past 1,500 years of flows in the Brisbane River have revealed that South-East Queensland’s climate – once assumed to be largely stable – is in fact highly variable.

Until now, we have only had access to 200 years of weather records in South-East Queensland. But our new research used marine sediment cores (dirt from the bottom of the ocean) to reconstruct stream flows and rainfall over past millennia.

This shows that long droughts and regular floods are both prominent features in South-East Queensland’s climate.

This is concerning. Decisions about where we build infrastructure and how we use water have been based on the assumption that our climate – especially rainfall – is relatively stable.




Read more:
Old floods show Brisbane’s next big wet might be closer than we think


Archives of past climates

Natural archives of climate are preserved within things such as tree rings, coral skeletons, ice cores, lake or marine sediments. Examining them lets us extend our climate records back beyond documented history.

We can then undertake water planning in the context of a longer record of climate, instead of our short-term instrumental records.

In this study, we used sediment cores from Moreton Bay (next to the mouth of the Brisbane River) to reconstruct the river’s flow over the past 1,500 years. In these cores we measured various indicators of fresh water to reconstruct a record of streamflow and regional rainfall.

At the turn of the last millennium the region was in the middle of a prolonged dry spell that lasted some six centuries, from roughly the year 600 to 1200. After about 1350 the region became gradually wetter, with peaks revealing a series of extreme floods in the late 1600s and early 1700s. Large floods in the 1700s have also been documented in the upper reaches of the catchment, in the Lockyer Valley.

These broad shifts in regional rainfall and streamflow are linked to drivers of global climates, including hemispheric cooling and the El Niño-Southern Oscillation.




Read more:
Explainer: El Niño and La Niña


A cool La Niña-dominant climate that persisted from roughly 1350 until 1750 caused increased rainfall and reduced evaporation.

In addition, the southward displacement of monsoon troughs at this time may have increased the likelihood of cyclone-related weather systems reaching southern Queensland.

This information helps us contextualise the climate of the last 200 years and gives us some insights into how regional rainfall responds to shifts in global climate.

Wet and dry extremes

Over the past 20 years, South-East Queensland has experienced its fair share of extreme weather events. Severe floods have caused deaths and damaged infrastructure. Flooding cost the Australian economy some A$30 billion in 2011.

Regular droughts may mean South-East Queensland needs to rethink water resource strategies.
Shutterstock

The millennium drought, which in this region was most severe from 2003-08, resulted in widespread water shortages. This prompted major investment in the South-East Queensland Water Grid, a connected network of dams, water treatment plants, reservoirs, pump stations and pipelines.

So far Queensland has coped with everything Mother Nature has thrown at it. But what if extreme floods and droughts became the norm rather than the exception?




Read more:
Floods don’t occur randomly, so why do we still plan as if they do?


Water quality is getting worse

The 2011 and 2013 floods highlighted the vulnerability to these extreme events of Brisbane’s major water treatment facility at Mt Crosby. The drinking water supply to the city in 2013 became too muddy for purification. The 2011 flood was also alarmingly muddy.

Such events also threaten the ecosystem health of downstream waterways, including the iconic Moreton Bay

Our reconstruction found that big floods over the past 1,500 years rivalled the size of floods in recorded history (1893, 1974 and 2011), but the level of sediment in the water of more recent floods seems to be unprecedented.

This indicates that historical and ongoing land-use changes in the Brisbane River catchment are contributing to more abrupt and erosive floods.

This will continue unless better land management techniques are adopted to improve the resilience of catchments to extreme weather events.

What does this mean for the future?

We are learning that over the last millennium natural climate and rainfall have been more variable than previously thought. This means that modern anthropogenic climate change may be exacerbated by a background of already high natural climate variability.

In addition, our water infrastructure has been built based on a narrow understanding of natural climate variability, limited to the last 200 years. This may mean the quantity of reliable long-term freshwater resources in eastern Australia has been overestimated.


The Conversation


Read more:
Droughts & flooding rains: what is due to climate change?


Jack Coates-Marnane, Post-doctoral research fellow, Griffith University; Joanne Burton, Adjunct Research Fellow, Griffith University; John Tibby, Senior Lecturer in Environmental Change, University of Adelaide; Jon Olley, Professor of Water Science, Griffith University; Joseph M. McMahon, PhD candidate, Griffith University, and Justine Kemp, Senior Research Fellow in Geomorphology, Griffith University

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

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New coal doesn’t stack up – just look at Queensland’s renewable energy numbers



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As the name suggests, Windy Hill near Cairns gets its fair share of power-generating weather.
Leonard Low/Flickr/Wikimedia Commons, CC BY

Matthew Stocks, Australian National University and Andrew Blakers, Australian National University

As the federal government aims to ink a deal with the states on the National Energy Guarantee in August, it appears still to be negotiating within its own ranks. Federal energy minister Josh Frydenberg has reportedly told his partyroom colleagues that he would welcome a new coal-fired power plant, while his former colleague (and now Queensland Resources Council chief executive) Ian Macfarlane urged the government to consider offering industry incentives for so-called “clean coal”.

Last month, it emerged that One Nation had asked for a new coal-fired power plant in north Queensland in return for supporting the government’s business tax reforms.

Is all this pro-coal jockeying actually necessary for our energy or economic future? Our analysis suggests that renewable energy is a much better choice, in terms of both costs and jobs.




Read more:
Solar PV and wind are on track to replace all coal, oil and gas within two decades


Renewables and jobs

Virtually all new generation being constructed in Australia is solar photovoltaics (PV) and wind energy. New-build coal power is estimated to cost A$70-90 per megawatt-hour, increasing to more than A$140 per MWh with carbon capture and storage.

Solar PV and wind are now cheaper than new-build coal power plants, even without carbon capture and storage. Unsubsidised contracts for wind projects in Australia have recently been signed for less than A$55 per MWh, and PV electricity is being produced from very large-scale plants at A$30-50 per MWh around the world.

Worldwide, solar PV and wind generation now account for 60% of global net new power capacity, far exceeding the net rate of fossil fuel installation.

As the graph below shows, medium to large (at least 100 kilowatts) renewable energy projects have been growing strongly in Australia since 2017. Before that, there was a slowdown due to the policy uncertainty around the Renewable Energy Target, but wind and large scale solar are now being installed at record rates and are expected to grow further.

Left axis/block colours: renewable energy employment by generation type in Australia; right axis/dotted lines: installed wind and large-scale solar generation capacity.
ABS/Clean Energy Council/Clean Energy Regulator, Author provided

As the graph also shows, this has been accompanied by a rapid increase in employment in the renewables sector, with roughly 4,000 people employed constructing and operating wind and solar farms in 2016-17. In contrast, employment in biomass (largely sugar cane bagasse and ethanol) and hydro generation have been relatively static.

Although employment figures are higher during project construction than operation, high employment numbers will continue as long as the growth of renewable projects continues. As the chart below shows, a total of 6,400MW of new wind and solar projects are set to be completed by 2020.

Renewable energy projects expected to be delivered before 2020.
Clean Energy Regulator

The Queensland question

Australia’s newest coal-fired power plant was opened at Kogan Creek, Queensland in 2007. Many of the political voices calling for new coal have suggested that this investment should be made in Queensland. But what’s the real picture of energy development in that state?

There has been no new coal for more than a decade, but developers are queuing up to build renewable energy projects. Powerlink, which owns and maintains Queensland’s electricity network, reported in May that it has received 150 applications and enquiries to connect to the grid, totalling 30,000MW of prospective new generation – almost all of it for renewables. Its statement added:

A total of more than A$4.2 billion worth of projects are currently either under construction or financially committed, offering a combined employment injection of more than 3,500 construction jobs across regional Queensland and more than 2,000MW of power.

As the map below shows, 80% of these projects are in areas outside South East Queensland, meaning that the growth in renewable energy is set to offer a significant boost to regional employment.

Existing and under-construction (solid) and planned (white) wind and solar farms in Queensland.
Qld Dept of Resources, Mines & Energy

Tropical North Queensland, in particular, has plenty of sunshine and relatively little seasonal variation in its climate. While not as windy as South Australia, it has the advantage that it is generally windier at night than during the day, meaning that wind and solar energy would complement one another well.

Renewable energy projects that incorporate both solar and wind in the same precinct operate for a greater fraction of the time, thus reducing the relative transmission costs. This is improved still further by adding storage in the form of pumped hydro or batteries – as at the new renewables projects at Kidston and Kennedy.

Remember also that Queensland is linked to the other eastern states via the National Electricity Market (NEM). It makes sense to build wind farms across a range of climate zones from far north Queensland to South Australia because – to put it simply – the wider the coverage, the more likely it is that it will be windy somewhere on the grid at any given time.

This principle is reflected in our work on 100% renewable electricity for Australia. We used five years of climate data to determine the optimal location for wind and solar plants, so as to reliably meet the NEM’s total electricity demand. We found that the most cost-effective solution required building about 10 gigawatts (GW) of new wind and PV in far north Queensland, connected to the south with a high-voltage cable.

Jobs and growth

This kind of investment in northern Queensland has the potential to create thousands of jobs in the coming decades. An SKM report commissioned by the Clean Energy Council estimated that each 100MW of new renewable energy would create 96 direct local jobs, 285 state jobs, and 475 national jobs during the construction phase. During operation those figures would be 9 local jobs, 14 state jobs and 32 national jobs per 100MW of generation.

Spreading 10GW of construction over 20 years at 500MW per year would therefore deliver 480 ongoing local construction jobs and 900 ongoing local operation jobs once all are built, and total national direct employment of 2,400 and 3,200 in construction and operations, respectively.

But the job opportunities would not stop there. New grid infrastructure will also be needed, for transmission line upgrades and investments in storage such as batteries or pumped hydro. The new electricity infrastructure could also tempt energy-hungry industries to head north in search of cheaper operating costs.




Read more:
The government is right to fund energy storage: a 100% renewable grid is within reach


One political party with a strong regional focus, Katter’s Australia Party, understands this. Bob Katter’s seat of Kennedy contains two large renewable energy projects. In late 2017, he and the federal shadow infrastructure minister Anthony Albanese took a tour of renewables projects across far north Queensland’s “triangle of power”.

The ConversationKatter, never one to hold back, asked “how could any government conceive of the stupidity like another baseload coal-fired power station in North Queensland?” Judging by the numbers, it’s a very good question.

Matthew Stocks, Research Fellow, ANU College of Engineering and Computer Science, Australian National University and Andrew Blakers, Professor of Engineering, Australian National University

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

Australia’s Largest Wind Farm Approved in Queensland


The link below is to an article reporting on the approval of Australia’s largest wind farm in Queensland.

For more visit:
https://www.theguardian.com/environment/2018/jun/05/australias-largest-windfarm-wins-planning-approval

Queensland’s new land-clearing laws are all stick and no carrot (but it’s time to do better)


Philippa England, Griffith University

The Queensland government passed legislation last month to prevent the clearing of high-value regrowth vegetation on freehold and Indigenous land. The move has been deeply unpopular with many landholders. They have argued that they are footing the bill for the commmunity’s environmental aspirations – without compensation.

The government’s intention was to reinstate a “responsible vegetation management framework”, broadly in line with legislation first passed in 2004, but which the Newman government repealed in 2013.




Read more:
Queensland’s new land clearing bill will help turn the tide, despite its flaws


But time has moved on since 2004. Instead of relying on a heavy-handed regulatory approach, a mix of carrots and sticks might have generated economic value for landholders, and reduced land clearing into the bargain.

Why landholders are fuming

Broadly speaking, landholders are worried the government hasn’t listened to their concerns and won’t pay for the land that is now effectively under state regulatory control. The parliamentary committee set up to report on the bill received more than 13,000 submissions (including 777 non-pro-forma submissions) – the largest number received by any committee of the Queensland parliament.




Read more:
Australia is a global top-ten deforester – and Queensland is leading the way


The government itself has admitted stakeholders were not consulted in the preparation of the bill, although the department report cites a “substantial history” of consultation on many of its measures. Nevertheless, the Queensland Law Society felt that further consultation would have been appropriate given “the sensitive nature of this legislation”.

Many submissions raised concerns about information shortfalls, regulatory duplication and excessive red tape. The department’s fallback position was simply to argue that “the proposed amendments are consistent with the government’s 2017 election commitment”.

Ironically, it is not only landholders who have lost out financially. The Queensland government is now effectively in control of an additional 1.76 million hectares of land, which it intends to leave undeveloped. But, in today’s world, the carbon stored in this land has a market price as well as an environmental value, if it’s properly managed.

Better alternatives

With a little more preparation and creative thinking, the government might have been able to spare our vegetation, create a huge pool of lucrative carbon offsets ready to market to the world, and provide compensation to affected landholders.

For instance, instead of an outright prohibition on land clearing, the government could have put in place a three-year moratorium on land clearing. Landholders could then be given a chance to opt out of the moratorium by transferring their land to a permanent conservation covenant or similar arrangement.

Although some careful drafting would be required to ensure the offsets integrity standards and other regulatory requirements are met, landholders who opted out of the temporary moratorium could become eligible to earn carbon offsets, or any other available financial incentives.




Read more:
Can carbon farming change the face of rural Australia?


On the other hand, landholders who do not respond to this financial “carrot” would run the risk of being hit with the (uncompensated) “stick” of a more prescriptive approach (temporary or not) at the end of the moratorium period.

The government could help this transition along by helping landholders sign up for one or more of the various existing schemes for conservation covenants, carbon offsets and biodiversity offsets. One of the main factors preventing greater participation in these schemes is prohibitively high transaction costs, especially in the early stages.

I realise there is a degree of wishful thinking about this proposal. Several hurdles, particularly political ones, would need to be overcome. But if we want serious, fair and enduring land use reform, I think these options merit a more meaningful investigation.

At the moment, a heavy-handed sweep of a pen by politicians in Brisbane has locked both landholders and government out of the market for ecosystem services. Given that the government now essentially owns a huge store of carbon assets, it’s a missed opportunity.




Read more:
Australia’s biggest emitters opt to ‘wait and see’ over Emissions Reduction Fund


The ConversationWith a little more creative thinking, Queensland might have provided compensation to landholders at no cost to itself. Instead, it has used a regulatory hammer to impose rules that – judging by past performance – have no guarantee of surviving past the next election.

Philippa England, Senior Lecturer, Griffith Law School, Griffith University

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

Dugong and sea turtle poo sheds new light on the Great Barrier Reef’s seagrass meadows


Samantha J Tol, James Cook University; Alana Grech, James Cook University; Paul York, James Cook University, and Rob Coles, James Cook University

Just like birds and mammals carrying seeds through a rainforest, green sea turtles and dugong spread the seeds of seagrass plants as they feed. Our team at James Cook University’s TropWATER Centre has uncovered a unique relationship in the seagrass meadows of the Great Barrier Reef.

We followed feeding sea turtle and dugong, collecting samples of their floating faecal matter. Samantha then had the unenviable job of sifting through hundreds of smelly samples to find any seagrass seeds. These seeds range in size from a few centimetres to a few millimetres, and therefore can require the assistance of a microscope to be found. Once any seeds were found, they were stained with a chemical dye (Tetrazolium) to see if they were still viable (capable of growing).

PhD candidate Samantha Tol holding dugong poo collected from Cleveland Bay in Townsville.
TropWATER, JCU

Why is this important for turtles and dugong?

Green sea turtles and dugong are iconic animals on the reef, and seagrass is their food. Dugong can eat as much as 35 kilograms of wet seagrass a day, while sea turtles can eat up to 2.5% of their body weight per day. Without productive seagrass meadows, they would not survive.

This relationship was highlighted in 2010-11 when heavy flooding and the impact of tropical cyclone Yasi led to drastic seagrass declines in north Queensland. In the year following this seagrass decline there was a spike in the number of starving and stranded sea turtles and dugong along the entire Queensland coast.

The seagrass team at James Cook University has been mapping, monitoring and researching the health of the Great Barrier Reef seagrasses for more than 30 years. While coral reefs are more attractive for tourists, the Great Barrier Reef World Heritage Area actually contains a greater area of seagrass than coral, encompassing around 20% of the world’s seagrass species. Seagrass ecosystems also maintain vibrant marine life, with many fish, crustaceans, sea stars, sea cucumbers, urchins and many more marine animals calling these meadows their home.

These underwater flowering plants are a vital component of the reef ecosystem. Seagrasses stabilise the sediment, sequester large amounts of carbon from the atmosphere and filter the water before it reaches the coral reefs. Further, the seagrass meadows in the Great Barrier Reef support one of the largest populations of sea turtles and dugong in the world.

Seagrass meadows are more connected than we thought

Samantha’s research was worth the effort. There were seeds of at least three seagrass species in the poo of both sea turtles and dugong. And lots of them – as many as two seeds per gram of poo. About one in ten were viable, meaning they could grow into new plants.

Based on estimates of the number of animals in the coastal waters, the time it takes for food to pass through their gut, and movement data collected from animals fitted with satellite tags, there are potentially as many as 500,000 viable seeds on the move each day in the Great Barrier Reef. These seeds can be transported distances of up to 650km in total.

Green Island seagrass meadow exposed at low tide.
TropWATER, JCU

This means turtles and dugong are connecting distant seagrass meadows by transporting seeds. Those seeds improve the genetic diversity of the meadows and may help meadows recover when they are damaged or lost after cyclones. These animals help to protect and nurture their own food supply, and in doing so make the reef ecosystem around them more resilient.

Understanding recovery after climate events

Seagrass meadows have been under stress in recent years. A series of floods and cyclones has left meadows in poor condition, and recovery has been patchy and site-dependent.

This research shows that these ecosystems have pathways for recovery. Provided we take care with the environment, seagrasses may yet recover without direct human intervention.

The ConversationThis work emphasises how much we still have to learn about how the reef systems interconnect and work together – and how much we need to protect every part of our marvellous and amazing reef environment.

Samantha J Tol, PhD Candidate, James Cook University; Alana Grech, Assistant Director, ARC Centre of Excellence for Coral Reef Studies, James Cook University; Paul York, Senior Research Scientist in Marine Biology, James Cook University, and Rob Coles, Team leader, Seagrass Habitats, TropWATER, James Cook University

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

$500 million for the Great Barrier Reef is welcome, but we need a sea change in tactics too



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The new funding is focused on measures that are already in the foreground.
Robert Linsdell/Flickr, CC BY

Jon Brodie, James Cook University

The federal government’s announcement of more than A$500 million in funding for the Great Barrier Reef is good news. It appears to show a significant commitment to the reef’s preservation – something that has been lacking in recent years.

The new A$444 million package, which comes in the wake of the A$60 million previously announced in January, includes:

  • A$201 million to improve water quality by cutting fertiliser use and adopting new technologies and practices

  • A$100 million for research on coral resilience and adaptation

  • A$58 million to continue fighting crown-of-thorns starfish

  • A$45 million for community engagement, particularly among Traditional Owners

  • A$40 million to enhance monitoring and management on the GBR.

A spokesperson for federal environment minister Josh Frydenberg said the funding would be available immediately to the Great Barrier Reef Foundation, and that there was no predetermined time frame for the spending.

But one concern with the package is that it seems to give greatest weight to the strategies that are already being tried – and which have so far fallen a long way short of success.

Water quality

The government has not yet announced the timelines for rollout of the program. But if we assume that the A$201 million is funding for the next two years, this matches the current rate of water quality management funding – A$100 million a year, which has been in place since 2008.

Yet it is already clear that this existing funding is not reducing pollution loads on the GBR by the required extent. The federal and Queensland governments’ own annual report cards for 2015 and 2016 reveal limited success in improving water quality. It is also known from joint Australian and Queensland government analyses that the required funding to meet water quality targets is of the order of A$1 billion per year over the next 10 years.

In the region’s main industries, such as sugarcane cultivation and beef grazing, most land is still managed using methods that are well below best practice for water quality, such as fertiliser rates of application in sugarcane cultivation. According to the 2017 Scientific Consensus Statement on the GBR’s water quality, very limited progress has been made so far.

Progress towards targets and assigned scores in the 2015 Great Barrier Reef Report Card.
2017 Scientific Consensus Statement, Author provided

The respective load reduction targets set for 2018 and 2025 are highly unlikely to be met at current funding levels. For example, shown below are the current projections for levels of dissolved inorganic nitrogen (DIN).

Progress on reducing total GBR wide dissolved inorganic nitrogen loads and trajectories towards targets.
CREDIT, Author provided

This likely failure to meet any of the targets was noted by UNESCO in 2015 and again in 2017 as a major concern, amid deliberations on whether to put the GBR on the World Heritage in Danger list. The UNESCO report criticised Australia’s lack of progress towards achieving its 2050 water quality targets and failure to pass land clearing legislation.

As the 2017 Scientific Consensus Statement also pointed out, improvements to land management oversight are “urgently needed”. Continued government spending on the same programs, at the same levels, and with no federal legislation to mandate improvements, is unlikely to bring water pollution to acceptable levels or offer significant protection to the GBR.

In contrast to the federal government, the Queensland government is taking what are likely to be more effective measures to manage water quality. These include regulations such as the revised Vegetation Management Act, which is likely to be passed by the parliament in the next few weeks; and the updated Reef Protection Act, currently out for review. Queensland is also directing funds towards pollution hotspots under the Major Integrated Projects framework.




Read more:
Cloudy issue: we need to fix the Barrier Reef’s murky waters


Crown-of-thorns starfish

The government’s new package has pledged A$58 million for further culling of this coral-eating animal. Yet the current culling program has faced serious criticism over its effectiveness.

Udo Engelhardt, director of consultancy Reefcare International, and a pioneer in the control of crown-of-thorns starfish, has claimed that his analysis of the culling carried out in 2013-15 in reef areas off Cairns and to the south of Cairns, reveals a “widespread and consistent failure” to protect coral cover.

Nor does there seem to have been a major independent review of the program since these findings came to light. Without one, it seems a shaky bet to assume that we will expect any more success simply by continuing to fund it.

Overcoming crown-of-thorns starfish might take some more creative thinking.
Paul Asman/Jill Lenoble/Wikimedia Commons, CC BY

Reef restoration

Similar question marks hover over the A$100 million being provided to harness the best science to help restore and protect the reef, and to study the most resilient corals. Like other aspects of the package, the government has not yet promised a timeline on which to roll out the funds.

While reef restoration may be significant for the long-term (decades to centuries) status of the GBR, it is hard to believe that these studies will help within the coming few decades. And even long-term success will hinge either on our ability to stabilise the climate, or on science’s ability to keep pace with the rate of future change.

In the meantime, reef restoration seems at best to be a band-aid that could preserve select tourism sites, but is inconceivable on the scale of the entire GBR.




Read more:
Not out of hot water yet: what the world thinks about the Great Barrier Reef


Herein lies the most significant criticism of the new funding package. It avoids any mention of reducing Australia’s greenhouse gas emissions, or of working closely with the international community to help deliver significant global reductions. Yet climate change is routinely described as the biggest threat to the reef.

The ConversationThe new announcement dodges that issue, while providing a moderate amount of funding for the continuation of largely unsuccessful programs. Given that the new funding is to be managed by the Great Barrier Reef Foundation – which is a charity rather than a statutory management body – we can only hope that the foundation finds new and innovative ways to improve greatly on the current efforts.

Jon Brodie, Professorial Fellow, ARC Centre of Excellence for Coral Reef Studies, James Cook University

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

How the 2016 bleaching altered the shape of the northern Great Barrier Reef



File 20180418 163978 1aql97h.jpg?ixlib=rb 1.1
Staghorn and tabular corals suffered mass die-offs, robbing many individual reefs of their characteristic shapes.
ARC Centre of Excellence for Coral Reef Studies/ Mia Hoogenboom

Selina Ward, The University of Queensland

In 2016 the Great Barrier Reef suffered unprecedented mass coral bleaching – part of a global bleaching event that dwarfed its predecessors in 1998 and 2002. This was followed by another mass bleaching the following year.

This was the first case of back-to-back mass bleaching events on the reef. The result was a 30% loss of corals in 2016, a further 20% loss in 2017, and big changes in community structure. New research published in Nature today now reveals the damage that these losses caused to the wider ecosystem functioning of the Great Barrier Reef.

Fast-growing staghorn and tabular corals suffered a rapid, catastrophic die-off, changing the three-dimensional character of many individual reefs. In areas subject to the most sustained high temperatures, some corals died without even bleaching – the first time that such rapid coral death has been documented on such a wide scale.




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


The research team, led by Terry Hughes of James Cook University, carried out extensive surveys during the two bleaching events, at a range of scales.

First, aerial surveys from planes generated thousands of videos of the reef. The data from these videos were then verified by teams of divers in the water using traditional survey methods.

Finally, teams of divers took samples of corals and investigated their physiology in the laboratory. This included counting the density of the microalgae that live within the coral cells and provide most of the energy for the corals.

The latest paper follows on from earlier research which documented the 81% of reefs that bleached in the northern sector of the Great Barrier Reef, 33% in the central section, and 1% in the southern sector, and compared this event with previous bleaching events. Another previous paper documented the reduction in time between bleaching events since the 1980s, down to the current interval of one every six years.

Different colour morphs of Acropora millepora, each exhibiting a bleaching response during mass coral bleaching event.
ARC Centre of Excellence for Coral Reef StudiesStudies/ Gergely Torda

Although reef scientists have been predicting the increased frequency and severity of bleaching events for two decades, this paper has some surprising and alarming results. Bleaching events occur when the temperature rises above the average summer maximum for a sufficient period. We measure this accumulated heat stress in “degree heating weeks” (DHW) – the number of degrees above the average summer maximum, multiplied by the number of weeks. Generally, the higher the DHW, the higher the expected coral death.

The US National Oceanic and Atmospheric Administration has suggested that bleaching generally starts at 4 DHW, and death at around 8 DHW. Modelling of the expected results of future bleaching events has been based on these estimates, often with the expectation the thresholds will become higher over time as corals adapt to changing conditions.

In the 2016 event, however, bleaching began at 2 DHW and corals began dying at 3 DHW. Then, as the sustained high temperatures continued, coral death accelerated rapidly, reaching more than 50% mortality at only 4-5 DHW.

Many corals also died very rapidly, without appearing to bleach beforehand. This suggests that these corals essentially shut down due to the heat. This is the first record of such rapid death occurring at this scale.

This study shows clearly that the structure of coral communities in the northern sector of the reef has changed dramatically, with a predominant loss of branching corals. The post-bleaching reef has a higher proportion of massive growth forms which, with no gaps between branches, provide fewer places for fish and invertebrates to hide. This loss of hiding places is one of the reasons for the reduction of fish populations following severe bleaching events.




Read more:
The world’s coral reefs are in trouble, but don’t give up on them yet


The International Union for Conservation of Nature (IUCN), which produces the Red List of threatened species, recently extended this concept to ecosystems that are threatened with collapse. This is difficult to implement, but this new research provides the initial and post-event data, leaves us with no doubt about the driver of the change, and suggests threshold levels of DHWs. These cover the requirements for such a listing.

Predictions of recovery times following these bleaching events are difficult as many corals that survived are weakened, so mortality continues. Replacement of lost corals through recruitment relies on healthy coral larvae arriving and finding suitable settlement substrate. Corals that have experienced these warm events are often slow to recover enough to reproduce normally so larvae may need to travel from distant healthy reefs.

Although this paper brings us devastating news of coral death at relatively low levels of heat stress, it is important to recognise that we still have plenty of good coral cover remaining on the Great Barrier Reef, particularly in the southern and central sectors. We can save this reef, but the time to act is now.

This is not just for the sake of our precious Great Barrier Reef, but for the people who live close to reefs around the world that are at risk from climate change. Millions rely on reefs for protection of their nations from oceanic swells, for food and for other ecosystem services.

The ConversationThis research leaves no doubt that we must reduce global emissions dramatically and swiftly if we are save these vital ecosystems. We also need to invest in looking after reefs at a local level to increase their chances of surviving the challenges of climate change. This means adequately funding improvements to water quality and protecting as many areas as possible.

Selina Ward, Senior Lecturer, School of Biological Sciences, The University of Queensland

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