What Does the Bleaching of Vast Areas of the Northern Great Barrier Reef Really Mean?

On March 30^th, I briefly commented on the bleaching now taking place on the northern Great Barrier Reef.  Today I want to talk about what this really means.

XL Catlin Seaview Survey divers over bleached coral at Lizard Island, March 2016.  Photo © AFP/Getty

Reports so far indicate that there has been major damage and considerable coral death, and it has been widely reported in the media.  The Australian science community is making a major effort to document the damage, in ways that should provide answers to important questions – like is there any evidence that corals are evolving a greater tolerance of warmed water.  But all the media coverage has focused on the event, its scale and seriousness for corals on the Great Barrier Reef (GBR).  I think a much wider perspective is in order.

Back in September, I devoted space on this blog to the current el Niño, which now looks like it will definitely prove to be stronger and longer than the 1997-98 event, until now the most extreme el Niño in recent history.  What is now happening off the northeastern Australian coast is just one aspect of the effect of this huge el Niño on coral reefs around the world, but in calling for a wider perspective, I am not just referring to the on-going global bleaching event.  I will talk about what the GBR bleaching means for reefs, what it means for our appreciation of global climate change, what it means for our understanding of the task ahead if we are to bring climate change under control, what it means, in particular, for Australia’s understanding of the changes that country needs to make if it truly values the GBR, and, finally, what this all means for our collective relationship with and stewardship of this planet of which we are a part.  Wish me luck; let’s get started.

What bleaching of the northern GBR means for reefs

The meaning for reefs is simple:  “We told you so, many times”.  Extensive mass coral bleaching was first observed along the Pacific coast of Panama and in the Galapagos in 1982-3.  Peter Glynn, the coral ecologist who documented the occurrence, noted that there was a particularly strong el Niño that summer, inferred that the exceptionally warm water that resulted was the stressor causing the bleaching, and predicted that climate change would make bleaching an event that would recur and become more prevalent in subsequent years.  In all respects, Peter Glynn was right.  Unfortunately.

Since 1983, there have been multiple reports of mass bleaching from coral reefs throughout the tropics.  During 1997-98, in the presence of what was then the most intense el Niño in the recent past, the world observed the first pan-tropical mass bleaching event ever, and the mortality of coral representing approximately 16% of all live coral cover on reefs worldwide.

Most of the fish disappear soon after the reef has bleached.  Photo © O. Hoegh-Guldberg

Bleaching has now become a permanent feature of summer somewhere in the tropics, and for the last 18 years, reef scientists have been variously reporting on bleaching, studying factors leading to bleaching or traits favoring survival of warm water without bleaching, and projecting likely consequences if climate change continues to warm the oceans.  One major question has been whether, and the degree to which, corals and/or their dinoflagellate symbionts will be able to evolve adaptations to survive warmer water.  Along the way, there have been glimmers of good news along with a lot of bad news.

One of those glimmers is that in nearly all bleaching events, some corals survive unbleached, and these remain available to drive some recovery even if the great majority of bleached corals succumb.  That some do not bleach provides evidence of the inherent variation among individuals that is required for adaptation to evolve.  However, the majority of reef biologists who have commented are skeptical of the ability of corals to evolve adaptations to warming water, because of the long generation times of corals and the rapid rate at which the world is warming.

(For adaptation to evolve, it is necessary for warm water to cause some mortality, and then for the survivors (presumably corals with genetics that favor resistance to high temperatures) to reproduce successfully.  In that way, these more heat-tolerant types will become more prevalent in the population.  But when temperatures are rising so rapidly, corals are likely to be bleached repeatedly, by ever warmer water, leaving little time for the reproduction of favored types.  Clearly, the long-term outlook for coral reefs is very grim if warming is occurring too quickly to permit effective adaptation.)

Another glimmer of good news came in 2009-10, in the form of two studies, one on the GBR and one in the Florida Keys, in which water quality as well as the beaching of corals was documented during a period of warm water.  In both cases, it was possible to show that corals living in less polluted waters did not bleach until temperatures rose higher than was the case for corals in nearby, but more polluted water.  In other words, the stress of living in waters over-enriched with nutrients due to run-off made corals less tolerant of warm water, and they bleached more easily than would otherwise have been the case.  These two studies provided that essential fragment of evidence to support the otherwise tenuous argument that reefs will likely be more tolerant of warm water if they are well managed with respect to other stressors – overfishing, pollution, sedimentation, physical destruction, and so on.  This was an important argument, because otherwise the depressing news about coral bleaching could lead to a general malaise among reef managers and others, and a deterioration of reefs due to other stressors.  “Why waste time looking after the reefs; they are all going to bleach anyway.”  Over the years, managers have not given up, and the overall management of local stressors on coral reefs may have improved.  But still they bleach.

While investigating the science of bleaching, reef scientists have done their best to raise awareness over what has been happening, and to stress the importance of coral reefs, and the value that will be lost if they are gone.  About one fifth of the human population lives within 100km of a tropical coast, and many of these people are directly dependent on those coastal waters, frequently dotted with reefs, for their food and livelihood.  In addition, reefs have immense economic value in the coastal protection they provide and the fisheries and tourism they support, and further non-economic cultural, spiritual and biodiversity value.

The northern GBR is remote.  North of Cooktown there are few roads, fewer settlements, no agriculture other than some grazing, and one of the last, large, truly remote places on this planet.  That this portion of the GBR has bleached as severely as it has, confirms the worst fears of reef scientists.  Pristine reefs are now being bleached and killed by climate change.  This is serious and the future looks grim.

What this bleaching should mean for our appreciation of climate change

I write ‘should mean’ because I fear that, bad as it is, the bleaching of the northern GBR is not impacting most of us the way it should.  Despite all the effort by reef scientists and by many in the media, the bleaching of coral reefs has never really captured the attention of the mass of us the way scientists hoped it would.  Phrases like ‘canary in the mineshaft’, ‘jewels of the sea’, and ‘biodiversity storehouses of immense ecological and evolutionary importance’ have all been used along with some beautiful and other heart wrenching images, and coverage has been sufficient that few people have not heard that coral reefs are having difficulties.  But only a tiny fraction of people have understood just what is at stake.  Losing a substantial fraction of coral reefs worldwide is akin to throwing away a major fraction of marine biodiversity, but few people grasp what losing biodiversity means for the planet.  Losing the coastal protection services, or the fisheries resources of coral reefs will have profound impacts on the lives of many already marginalized people, but most scanners of the media do not know any of those people personally.  At best, most people who have heard that coral reefs are bleaching think that their opportunities for snorkeling in colorful locations may be dimmed in the future.  The bleaching of reefs is ‘too bad’ but it is not a signal of existential change for humanity on this planet.  Except that it is.

The repeated statements by informed scientists, ever since Peter Glynn first published his report of the 1982-3 bleaching in Panama, that bleaching is a clear sign that climate change has serious environmental consequences, and that bleaching will likely become more extensive and more frequent as climate warms have failed to generate the kind of widespread concern that motivates a desire to act to bring climate change under control.  Yet now we are witnessing the bleaching of some of the most pristine reefs on the planet.  If the northern GBR lacks the resilience to resist warming, what real hope is there for any coral reef if climate is permitted to continue to warm?  And given that the most dire predictions about reefs seem to be coming true, why are we not much more alarmed than we are?  I fear the efforts of reef scientists to communicate have simply not been sufficiently skillful to cut through the noise and the barrage of disinformation about climate (and, yes, I count myself among those unskilled communicators).

Aerial view of bleached reef, north Queensland, March 2016.  Image © ARC Centre for Coral Reef Studies

In my view, the claim by some among the reef science community that we must provide hope by focusing on the glimmers of good news, rather than “preach doom and gloom” has been an error.  We reef scientists need to be telling it like it is; telling the story accurately, projecting cautiously, but pointing to the near inevitability of the total loss of coral reefs under business as usual.  And we need to be doing a much better job of linking the bleaching of coral reefs to all the other manifestations that suggest humanity is pushing the biosphere towards existentially dangerous thresholds.  Roger Bradbury attempted to do this in an Op Ed in the New York Times in 2012; many of his colleagues condemned him for being too strident.

I do not even believe we have done a good job of effectively relating bleaching to all the other things going on on coral reefs.  This February, Rebecca Albright and Ken Caldeira of the Carnegie Institution’s Global Ecology Department at Stanford University, along with 16 colleagues, published an important paper in Nature on effects of ocean acidification on coral reefs.  Their study was a simple field experiment that took advantage of a unidirectional tidal flow across a reef flat at One Tree Reef, southern GBR, to temporarily adjust the pH and alkalinity of water flowing past a natural reef community.  By briefly shifting pH back to where it was in pre-industrial times (one hour per day over 22 days), they obtained a 6.9% increase in calcification rate across that strip of reef habitat.  While a short-term response to altered conditions (less than one hour per day during a falling tide) may not represent the long-term response if corals were growing continually under elevated pH, these results complement earlier work (2014, by Jacob Silverman and colleagues, including Ken Caldiera) at Lizard Island, GBR, showing that net calcification rates there have fallen by 27-49% since the mid-1970s, a rate that is consistent with the known change in pH.  They also complement still earlier work (2009) by Glenn De’ath and colleagues that revealed a marked slow-down in growth of Porites sp. corals on the GBR in recent years – a change they inferred was due to acidification.  Ocean acidification is proceeding in lock-step with warming, and there are clear indications that both impact coral reefs severely – both problems have to be solved, along with local pollution, sedimentation, physical destruction, and overfishing (see this recent paper on this topic).  Keeping reefs functional is a lot more challenging than just solving the warming.

To be fair to my colleagues, there are serious discussions of the multiple ways in which we are impacting this planet, and the plight of coral reefs was used very effectively to get the oceans into the IPCC and other discussions of climate change.  A few years ago one might have believed that climate change only affects terrestrial systems.  That has now changed.  But our messages about coral bleaching have remained too much about the corals.

To paraphrase American political adviser, James Carville,
“It’s not about corals, it’s about our ability to continue to live on this planet, stupid.”

As I am writing this, the media are reporting the new paper in Nature by Robert DeConto, U. Massachusetts, Amherst, and David Pollard, Penn State University, concerning likely rates of Antarctic melting and resultant sea level rise this century.  Using different methods than Jim Hansen, whose paper was discussed in my last post, they explore how Antarctic ice might melt, and predict global sea level rise of almost two meters by 2100, with Antarctica providing 1.05 ± 0.3 meters of that total under the IPCC RCP8.5 scenario for how we deal with CO₂ emissions.  This is double the rise IPCC projected in the latest (2014) Assessment Report.  DeConto and Pollard began by noting that present models do not do a good job of representing the changes in sea level at two past times – the Pliocene and the late Pleistocene when conditions were similar in many ways to now.  They modified the models to take account of two aspects of glacier melting: how warm ocean waters will undercut grounded ice leading to the rapid break-up of ice shelves around Antarctica’s shore, and how surface melting leads to water drilling down through the glacier causing further melting inside.  (These were also considered by Hansen).  With these adjustments their models replicated these past events appropriately, so they then applied the models to currently projected warming patterns and got their nearly two meters of sea level rise.  (Undark Magazine has an interesting account of how Hansen’s paper was received by the press – telling it like it seems to be, rather than softening the bad news with a focus on hope, can get a scientist pilloried by some.)

The messages that are not getting delivered effectively to people are that climate change is simultaneously causing multiple changes to our world, and that the impacts of climate change add to, or even enhance, the negative effects of a number of other things we are doing to our planet.  While corals are being bleached in the tropics, ice is rapidly melting at the poles, and we are going to have to deal with the consequences of both these trends, while also dealing with overfishing, rainforest destruction, desertification, rampant pollution of air, water and soil, and so on.  The science community is mostly aware of these multiple stressors on our world, the general public far less so.  And many politicians are still operating in a mindset that equates negotiations over climate to any other type of negotiations among nations – you talk for a while, you reach a compromise, everyone is happy, even though nobody got what they really wanted (I posted some more extensive comments on this issue last December).  Politicians seem not to have got the message that Nature does not negotiate, and the messaging on coral reefs does not seem to be helping much in the effort to deliver this message.  And this brings me to my next point.

What the GBR bleaching should mean for the task ahead

Even before the ink was dry on the Paris Agreement, in fact before the Paris conference started, it was clear that the agreement reached, while historic and a definite move forward, was going to be woefully inadequate if the world was serious about combating climate change.  Most national INDCs are timid, and waiting until 2020 to strengthen them is just kicking the can down the road.  (Canada’s INDC, developed by the previous, notoriously anti-climate action, Harper government, has yet to be strengthened despite all the positive words coming out of the new, pro-climate action, Trudeau government.  Will Canada wait till 2020 to do something about it?)

The new book by Johan Rockstrom and Mattias Klum provides a readable account of the problems we face, and why the world has to change.

The response is inadequate with respect to IPCC science, yet IPCC has consistently been a cautious body as it reviews current science, making that inadequacy doubly so.  IPCC’s need for consensus has meant that it has consistently underestimated the seriousness or the pace of climate change, and been overly optimistic about the ease with which the world community can bring this particular beast under control.  Thus, IPCC stated in its 5^th Assessment report (2014) that global sea level would rise 0.52 to 0.98 meters by 2100 under its most extreme (business as usual) scenario RCP8.5, despite the fact that many climate scientists expected that the increase would be significantly more.  IPCC did acknowledge that our understanding of how glaciers melt was in some flux, but reinforced the impression of only moderate sea level change by stating “the collapse of marine-based sectors of the Antarctic ice sheet, if initiated, could cause global mean sea level to rise substantially above the likely range during the 21st century.  However, there is medium confidence that this additional contribution would not exceed several tenths of a meter of sea level rise during the 21st century”.  (To translate the IPCC-speak, the ‘likely’ range (.52-.98 meters) is the range within which reality is expected to fall two-thirds or more of the time, and ‘medium confidence’ means IPCC has a middling level of confidence that this statement is correct – so ice sheet melt could make a bigger contribution.)

This tendency to favor less extreme departures from current conditions has probably helped maintain the widespread complacency about climate change.  Yes, it is a problem, but no, I do not have to radically revise my plans for my life to help deal with it.  And yet, if you read the IPCC reports carefully, they are pretty clear in spelling out the extent of the reduction in CO₂ emissions that has got to be achieved by mid-century if we want to keep climate warming to 2^oC.  The absolute need to keep nuclear power as a part of the electricity supply for at least a few decades longer, in order to be able to phase out fossil fuels, and the near certain need to develop effective new technology for carbon capture and sequestration, not to enable continued use of fossil fuels, but to strip carbon out of the atmosphere — these needs are not gaining the attention of political leaders or the industrial sector the way they should be.  That Alberta is waiting patiently for the oil boom to start back up is perhaps forgivable, if misguided.  That Canada’s national government is enabling them in this fantasy, by further delaying stricter environmental controls, and continuing the discussions about Canada’s need for additional pipelines is just unfortunate (a recent post on this topic is here).

It is not surprising that in the months following the Paris meeting there would be a pause to celebrate a significant achievement.  My fear is that the pause, like an unwelcome dinner guest, is settling in for a long stay.  Meanwhile, the global situation worsens and our chance of a good outcome in the global battle gets more remote.  The bleaching of the northern Great Barrier Reef should be causing a lot of us to remember we are engaged in a battle, and to get on with it.  I do not think it is doing that, no more than the other bits of climate news that assault us daily.

CO₂ concentration at Mauna Loa in the last week of March was 405.41ppm, 123ppm higher than it was that week in 1800.  February 2016 was the warmest February on record, as was January 2016, as were each of the previous 9 months.  February 2016 also surpassed the previous warmest February (2015) by the largest margin ever.  On 21^st March, in releasing a report on the extreme weather in 2015, the World Meteorological Organization’s Secretary General is quoted as saying “The future is happening now.  The alarming rate of change we are now witnessing in our climate as a result of greenhouse gas emissions is unprecedented in modern records.”  The statement identified shattered temperature records, intense heatwaves, exceptional rainfall, devastating drought, unusual tropical cyclone activity, unabated ocean warming and sea level rise, shrinking sea ice extent, and other extreme weather events around the world, and noted that the extreme weather was continuing into 2016.  Climate change is here, and it is worsening faster than most climate scientists expected.  And yet, for most people, life goes on, and climate change issues have been moved to a back shelf for a while, because we all did such a good job in Paris.

We remain blissfully unaware of how much more than Paris we have to do.  We keep forgetting that there are other affronts to natural systems that also must be acted on.  And population is the elephant in the room, even if the science community, every now and then attempts to make the elephant visible.  In its 25^th February issue, Nature included an essay by John Bongaarts, Vice-president of the Population Council, New York, titled ‘Slow down population growth’.  He pointed to the more than 50% expansion predicted between now and 2100, when the global population is estimated to become 11.2 billion, and stated that most of this growth will occur in the least developed parts of the planet.  Rapid population growth is a major impediment to economic and societal development, and can even pull developing countries back from the brink of success (when millions are lifted out of poverty and a viable economy can take hold).  Simultaneously, rapid population growth has severe environmental effects, and can make efforts to transition away from wasteful, polluting, CO₂-emitting economic structures.  We would all be far better off if population growth could be curtailed, and it may not even be possible to bring climate change under control if we do not address our population problem more aggressively as well.

This bleaching of the northern GBR should be one more splash of cold water across our faces, to wake us to the reality the science community has been trying to warn about for far too long.  And since the media are not using it like a splash of cold water, we scientists have got to step up and tell it clearly, and repeatedly, in simple language – people, this is how it really is; we are dangerously close to going over a cliff.  I fear the alarms are being sounded too gently; future generations will look back and wonder how we could be so blind to our peril.

What coral bleaching should mean for Australia

Australia is a country much like Canada, blessed with a small, but talented population, and a land rich in natural resources, it has developed an economy in which the extraction and export of those mineral resources is  a major part.  Australia is particularly rich in coal, and China and India are tantalizingly close neighbors who need energy resources.  Unlike Canada, Australia also has the world’s largest coral reef region, and these reefs have had far less mistreatment by people simply because the reefs are so large and so many and the people are so few.  Australia has recognized since the late 1970s that the Great Barrier Reef can provide immense economic value through its tourism and fisheries, is a powerhouse of marine biodiversity, an iconic natural wonder, and a feature that provides enormous spiritual and cultural value to Australians and to visitors from overseas.  Since the 1980s, Australia has mostly done a very good job of protecting the Great Barrier Reef while using it sustainably — exceptional, really, when compared to the usual management of reefs globally.  But too much of Australia’s coal is in Queensland, and the logical pattern for extraction is to ship it to ports along the Queensland coast and thence out through the reef and on to Asia.

Australia uses massive amounts of energy to extract the coal and ship it.  Eventually, the coal gets burnt and while the CO₂ emissions are not technically Australia’s problem, they add to the global emissions problem that Australia and all other countries are ostensibly trying to reduce.  Furthermore, the development and maintenance of commercial ports along the Queensland coast requires dredging and other activities that contribute directly to poor water quality on parts of the GBR.  While I was finishing this post, the Queensland government announced it was approving the proposed Carmichael coal mine, to be developed by the Indian mining company Adani – the same Queensland government that was recently criticizing the federal Australian government for foot-dragging on CO₂ emissions abatement.  That mine is slated to produce 60 million tonnes of coal a year, and export it via ports and ship travel through the GBR.

Australia really cannot have it both ways.  If the commitment to sustain the Great Barrier Reef in perpetuity is genuine, the bleaching now taking place on its most remote northern third has to be interpreted as a clear and unambiguous message.  The climate has now reached the point where all coral reefs are at serious risk; the need to reduce CO₂ emissions is real and urgent; supplying other countries with coal is an enabling gesture that is incompatible with sustaining the GBR.  Surely Australians are capable of building an economy that does not rely on digging up dangerous stuff and shipping it overseas to whoever wants to buy it?  But, come to think of it, I’ve asked exactly the same question of my own country.  True, Canada does not claim to be caring sustainably for a coral reef, and we have yet to recognize that our Arctic lowlands may turn out to be nearly as sensitive to climate change as is the GBR.  Australia’s coal and Canada’s tar sands oil have to stay in the ground.

What this all means for our relationship to the biosphere.

When we were few, and with limited technology, we still did some damage to this world, because we are intelligent, and saw how we could use fire to shape ecosystems to our benefit, and how we could create tools to allow us to hunt large animals on land and in the ocean.  But because we were few, and relatively weak, our impacts were local and often trivial, and if we did cause damage, we could always move away.  Now there are 7 billion of us, we are immensely powerful, and there is no longer any away to move to.

Unfortunately, we have, if anything, lost some of our awareness of our essential dependence on the biosphere, and we rarely consider the long-term, cumulative effects of our impacts, especially when there is money to be made.  As well as revitalizing our so far puny efforts to combat climate change, we must rebuild our links to nature, and cultivate once more a sense of responsibility for caring for nature.

What is happening right now on the northern GBR is just one more in a long list of object lessons.  But so far, they are object lessons that for the most part are being ignored.  Greed, thoughtlessness, short-term thinking, and a widespread lack of appreciation of the extent to which our lives are interwoven with the rest of the biosphere are trumping reason.  I fear the size of the jolt that is going to be required to wake us up to the perilousness of our condition.  Meanwhile, more coral bleaches.

The Great Barrier Reef – we need to save it to save ourselves.  Image © Hamilton Island Enterprises