Fairfax - Tom Arup
The Great Barrier Reef is often described as the largest living thing
on the planet, but swimming over the coral reefs around Heron Island it
is the little things that you notice.
Like the way the parrot fish gnaw at the bright coloured reefs for algae. Or how the fire coral shimmers in sunlight.
Heron Island has been lucky. It has been spared from the devastating mass coral bleaching unfolding elsewhere on the reef.
There
have been only a handful of major bleaching events in the Great Barrier
Reef's 8000-year existence. They first emerged in the early 1980s, with
the 1998 and 2002 events regarded by scientists as the worst.
 |
| The tourist brochure version: scuba diving on the Great Barrier Reef Photo: Supplied |
At least until this latest one.
This time more than 1000
kilometres of reef has been subjected to some extent of bleaching. The
pristine northern stretches between Cooktown and the Torres Strait have
been hit the hardest, with images emerging of ghostly white reefs from
places such as Lizard Island.
The event's spread and intensity has again raised uncomfortable
questions about the damage climate change is doing to Australia's most
important natural tourism site.
Professor Ove Hoegh-Guldberg, a
prominent marine scientist who has studied coral reefs for decades, says
he has little doubt about what is behind the bleaching.
 |
| A diver checking out the bleaching at Heron Island in February 2016. Photo: XL Catlin Seaview Survey |
"This event, I would say with 99 per cent certainty, is being driven by anthropogenic climate change," he says.
Heron
Island sits towards the southern end of the Great Barrier Reef's
2300-kilometre reach. It takes a stomach-turning two-hour boat ride from
Gladstone to get there.
 |
| Bleached coral at Heron Island. Photo: Eddie Jim |
When you arrive though the plentiful corals surrounding the island
look like the Reef" we all imagine – bathed in turquoise water,
colourful and littered with endless fish, rays, sharks and turtles.
Dr
Selina Ward, a coral reef ecologist at the University of Queensland,
says Heron's biodiversity is a stark reminder there is still much to
lose if the Great Barrier Reef is not looked after.
Bleaching does not necessarily lead to death. If water
temperatures drop in time corals can start rebuilding their algae and
recover within months.
"We've lost 50 per cent of coral cover on the reef in 27 years,
mostly due to cyclones, crown of thorns and bleaching," she says.
There is still enough coral left to turn the reef around, she says, but only if we do right by it.
 |
| Looking dead flat at Heron Island. Photo: Eddie Jim |
Across the planet ocean temperatures have risen as a result of global
warming. In Australia, average sea surface temperatures are a degree
higher than in 1910.
These elevated temperatures have driven
corals closer to thresholds where bleaching conditions occur. When a
weather event like El Nino emerges that threshold is often exceeded.
 |
| Bleached Coral at Heron Island. Photo: Eddie Jim |
"The mass bleaching is a result of climate change and a strong El
Nino exacerbating high sea surface temperatures that usually occur at
this time of year," says Dr Russell Reichelt, chairman of Great Barrier
Reef Marine Park Authority.
"This temperature trifecta has created heat stress and pushed corals beyond their ability to cope."
 |
| Coral off Heron Island. Photo: Eddie Jim |
Coral animals, called polyps, have a crucial symbiotic relationship
with algae that live in their cells and provide them with energy.
When
hard corals are stressed they expel this algae, which turns their
tissue translucent, and exposes their white skeletons. This leaves them
vulnerable to starvation, disease, and potentially death.
 |
| Bleached coral off Heron Island. Photo: Eddie Jim |
Dr Paul Marshall, the former head of the climate change program at
the marine park authority and now an adjunct professor at The University
of Queensland, says the link between coral stress, bleaching and
warming oceans is not in dispute.
"It is simple equation, you heat
up the atmosphere, you heat up the oceans. You heat up the oceans, the
corals get stressed. All of the causal links are absolutely robust," he
says.
 |
| Dr Selina Ward, senior lecturer, School of Biological Sciences, University of Queensland, checking out the acropora aspera coral at Heron Island. Photo: Eddie Jim |
Beyond warming seas, climate change poses other problems for the
reef, including increased ocean acidity, turbocharged storms and
sea-level rise.
Ward says rising ocean acidification is
particularly troubling for corals because it undercuts their ability to
lay skeleton, which forms the basis of reefs, and makes them more
brittle and vulnerable to erosion.
These climate pressures
interact with each other, multiplying the risks. And they present
problems not just for coral, but also for fish, other marine life and
the overall ability of the ecosystem to function.
They also come
against a backdrop of other environmental problems hampering the reef's
overall resilience. Water pollution from farming runoff is chief among
them.
Marshall says of the climate threats, bleaching can do the
most immediate damage. When it is severe enough, corals hundreds of
years old can die.
"That's something that has been really depressing for me," Marshall says.
"There
are corals that were here when Captain Cook sailed by, and they're
dying under our watch and they're not coming back in anyone's lifetime."
Bleaching
does not necessarily lead to death. If water temperatures drop in time
corals can start rebuilding their algae and recover within months.
Some
coral species – there are over 600 on the reef – are also naturally
hardier than others, so rather than total die-off bleaching can lead to
species switching instead.
According to the Australian Institute
of Marine Science about 55 per cent of the reef was bleached during the
2002 event. About 5 per cent died.
Given the right conditions new
corals can also rebuild on dead reefs in about a decade. One study of 21
reefs in the Seychelles, on which 90 per cent of corals died during a
1998 global bleaching event, found that 12 were eventually restored.
Ultimately
it will take weeks for the full extent of the current bleaching event
to emerge. The levels of coral mortality may not be known for longer
still.
Reichelt says: "experience tells us that corals can recover
from major disturbances, but they need to be given time and the right
conditions to do so."
The concern is that if coral bleaching
occurs more frequently, as it is projected to do, reefs won't have
sufficient time to recover.
Back in 1999 Hoegh-Guldberg forecast
that rising greenhouse gas emissions would see most oceans become too
hot for corals on a yearly basis by the 2040s and 2050s.
In the
most recent major assessment of the reef's health by the marine park
authority reported that under moderate future emissions, bleaching
conditions could be expected about once every five years for most parts
of the reef by 2018.
By 2052 to 2067 it could occur every year.
It
means some changes to the reef because of climate change appear
inevitable (though there is some scientific inquiry into whether corals
may be able to adapt somewhat to warmer and more acidic oceans).
Marshall says by 2050 the reef will ultimately be a different place and he paints four possible scenarios:
Good water quality, lower emissions
Under
this future some areas escape the worst damage and big and old corals
survive on some sites. Corals are able to grow and maintain themselves,
but will be in a recovery phase more regularly. The reef can support
diverse fish communities and habitat for other marine life.
Overall there is less coral cover, more algae, more open space. But it is still beautiful.
Good water quality, high emissions
Here
not much of the old corals remain, with smaller, faster growing ones
surviving instead. There is more open space and a lot of seaweed in it.
The big "architecture" of the reef no longer exists, reducing its
ability to support other marine life, especially the larger fish.
This is akin to moving from an old growth forest to scrubby regrowth next to a farm field.
Poor water quality, lower emissions
A
"dynamic tension" is established between seaweed and corals. Smaller
corals grow among the seaweed, both competing for the same space. The
seaweed increasingly gans the advantage as coral bleaching becomes more
frequent.
This environment still supports some marine life, such as smaller fish. But it is not beautiful.
Poor water quality, high emissions
An
effective wipeout. Only a fairly flat reef structure remains with very
few corals growing and a lot of seaweed. Constant stress from coral
bleaching and high levels of fertiliser and sediments entering from the
land means corals are largely replaced by seaweeds, and the reef is
unable to provide habitat for much fish life at all.
None of these futures are ideal.
Marshall
says the sad reality is that future generations will inherit a coral
reef that doesn't match the travel brochures of the 20th century. But he
adds smart decisions today "can still secure a beautiful, productive
reef for future generations."
Here is where it gets tricky.
The
federal and Queensland governments are already attempting, with mixed
success, to address water pollution problems through multibillion-dollar
commitments to tackle pesticide runoff from farms and damaging crown of
thorns infestations.
But what will largely decide the reef's fate
is how fast the world cuts emissions and how high global temperatures
are allowed to rise.
Reichelt points to a consensus statement
by the International Society for Reef Studies
released last year which argues the average global temperature increase
must be kept below two degrees in the short term, and below 1.5 degrees
in the long term, to allow coral reefs to survive in perpetuity.
It
is in that light green groups are trying to link the fate of the Great
Barrier Reef with new coal mine development. In their sights is the $21
billion Carmichael project in Queensland's Galilee Basin, which is
backed by Indian company Adani and if built, would be Australia's
largest coal mine.
Last Sunday the Queensland government signed
off on mining licences for Adani, which still needs to attract finance
for the Carmichael project. Green groups argued this was a moment of
enormous cognitive dissonance given the mass bleaching on the reef.
The
Australia Conservation Foundation, which flew media to Heron Island
this week to press its arguments, is also trying to make the link
legally.
It has launched court action to try overturn
environmental approvals for Carmichael, arguing the federal government
should have taken into account the damage that would be inflicted on the
reef from the emissions from burning the mined coal once it was shipped
to India
The Queensland Resources Council rejects this
connection. A spokeswoman says the emissions associated with the coal
would be lower than other energy sources like "burning dung for cooking,
which is one of the many high-emitting fuels that 300 million Indians
without power are using."
To say Carmichael coal would not have
any impact on the reef requires some rejection of the well-established
link between burning fossil fuels and global warming. But nor is it in
isolation enough to push the planet beyond two degrees of warming.
A
2014 expert study into the pollution associated with Carmichael coal
found it would use up 0.53-0.56 per cent of the remaining global
emissions that can occur and still see the world still avoid exceeding
two degrees.
The study also notes the Carmichael coal emissions is among the highest from any single project in the world.
Marshall
says if the Great Barrier Reef is stave off climate change then
Carmichael is not the only equation. The entire planet will have to cut
emissions from all sources.
"That's a great thing to anchor it in," Marshall says of the Carmichael-reef debate, "but really it is much bigger than that."
"The
future of the Great Barrier Reef, and reefs everywhere, depend on
society's ability to totally shift away from fossil fuels."
Lisette Collins from the Department of Government and International Relations has compiled the first ever database of climate change adaptation plans (CCAPS) developed by local councils nationwide.