My Seven Perspectives on the Great Barrier Reef


I remember the first time I saw the Great Barrier Reef.  It was in early November 1968.  I had driven up from Sydney, parked my car in long-term parking in Gladstone, Queensland, and suffered through what seemed an eternity of a trip on the aptly named Saramoa, to arrive at Heron Island, and the Heron Island Research Station.  That cow of a vessel would roll and pitch in anything other than a glassy calm, all the while bathing its passengers in diesel fumes that somehow travelled a corkscrew path from engine room, out through the stack, down past the stern and then back and in the open door to the cabin.  After five or more hours of this, few arrived at Heron Island as comfortable as they were departing Gladstone, and I learned the value of getting out in the breeze and watching the horizon intently for the duration of the trip.

Heron Island gave me immediate access to the richest coral reef I had yet seen, filled with innumerable creatures for whom I had no names.  The small library at the research station provided some names of doubtful value, and I began to learn.  The scale of Heron Reef was impressive.  At low tide, standing on the shore, the reef stretched out to the horizon, and knowing it was just one tiny portion of the Great Barrier Reef filled me with wonder.  While I knew it had a history, and had not always been here, I thought of the Great Barrier Reef as eternal, something dependable that could be relied upon to be here, as it was then, forever.

Heron Island in 2008 – the reef flat, dry or close to it at low tide, stretches 5 km towards the east of the island.  It’s just one of numerous such reefs within the Great Barrier Reef complex. 
Photo © P Sale.

In 1968, Australians by and large took the Great Barrier Reef for granted.  It was largely unmanaged and underused.  It would have been overused but for the fact it was a long way offshore (Heron Island was 80 km off Gladstone), and Australians were not numerous.  They had a proclivity to overuse, however.  Spearfishing derbies were frequent and popular, and hook and line fishers seldom stopped when they had caught more than enough fish to eat.  But then, Australia was the country where it was said, “if it moves, shoot it; if it doesn’t, cut it down; and if it’s underground, dig it up.”  The ocean was ‘known’ to be full of fish, and the Great Barrier Reef stretched on forever.

I continued to visit the Great Barrier Reef regularly over the next 20 years.  I watched as Australia awoke to the incredible value of this amazing natural wonder.  Not long after that first visit as the Queensland government got ready to sell off mining leases along the reef, a simple bumper sticker made its appearance.  Save the Barrier Reef. 

Australia opened its eyes to the possibility that greed and the hunt for hydrocarbons might damage the Great Barrier Reef.  Suddenly that was not okay.  (That certain leading Queensland politicians had hefty investments in the companies being awarded the leases may have helped swing the tide.)  And so there was a Royal Commission – a whole lot of talking by learned people – that dragged on for a while but resulted in a changed perspective.   The country decided the Great Barrier Reef was too important to be dug over for oil and gas; Australia had a responsibility to care for it.  This was my second perspective on the Great Barrier Reef.

Fast forward to the heady days of the late 1970s and the 1980s, and Australia was proposing, putting into law, and establishing the Great Barrier Reef Marine Park.  The Federal and Queensland governments cooperated in this venture, even when ruled by political parties of differing perspective!  Relatively large sums of money were spent and talented people with the necessary scientific and other skills were hired to manage what was, at the time, far and away the largest managed marine area in the world.  This became my third perspective on the Great Barrier Reef – the best managed, highly valued piece of marine real estate on the planet.

The Great Barrier Reef Marine Park remains one of the largest marine managed areas on the planet.  Its waters are zoned to permit different types of use at different places within the region, and management is done jointly by the state of Queensland and the federal government, through the Great Barrier Reef Marine Park Authority.  Map © GBRMPA.

Around that time, the first mass bleaching of coral reefs occurred.  It was far from Australia, and I only learned about it when accounts appeared in the technical journals a year later.  But in 1982, reefs along the Pacific coast of Panama, north into Costa Rica and south into Ecuador, as well as reefs in the Galapagos archipelago to the west all bleached severely as corals expelled their algal symbionts, and turned ghastly, ghostly white.  Many of those corals subsequently died.  Reef ecologist, Peter Glynn provided the most detailed information on the event, and drew a tentative connection to the unusually warm water caused by what was, at the time, the strongest el Niño ever recorded.  I’d like to think I woke up to what might be happening at that time.  But I did not, and nor did many of my reef science colleagues.  I knew something important had just happened, but figured it was a problem for coral scientists to solve – just one more fascinating feature of coral reefs.

By the late 1980s, I had left Australia, was exploring coral reefs in the Caribbean, and the Great Barrier Reef settled into my past, as a hazy image of wondrousness, a profoundly impressive ecological system that I had been privileged to study and to know.  That was my fourth perspective on the Great Barrier Reef.

A Great Barrier Reef reefscape.  Photo © Pablo Cogolos & Afar Productions.

Fast forward to 1997-1998, when another el Niño, the first to be more powerful than that in 1982 and now the second most powerful ever, led to mass coral bleaching around the world.  That was the first time we had witnessed circumtropical bleaching, and that time it got through to me.  About bloody time, you say! 

Many parts of the Great Barrier Reef bleached, as did coral reefs in other regions around the world as summer and el Niño spread that killing warm water.  Slowly it dawned on me that the Great Barrier Reef, that magnificent example of coral reef development, that immaculately unlikely, improbable exuberance of evolutionary magic, might actually be at real risk of becoming degraded into a depressing mass of eroding limestone covered by algal turfs.  That became my fifth perspective on the Great Barrier Reef.  Massive as it was, we appeared to be in the process of eliminating it from the planet.

I had watched from afar as Australian scientists and reef managers discovered some of the inadequacies of their initial management of the Great Barrier Reef.  I had seen a progressive strengthening of regulations each time the Great Barrier Reef Marine Park came up for re-zoning.  I had watched as they grappled with the challenges of regulating the land management practices of people and communities who lived far inland from the reef, but whose fertilizers and pesticides were impinging on portions of the reef every time severe rain led to flooding.  And I had watched as they grappled with the similarly challenging, though perhaps more obvious, tasks of regulating fishing and tourism on the reef itself, all while tourism to the Great Barrier Reef exploded. 

The Great Barrier Reef Marine Park was still the best managed large marine protected area in the world, though its management was definitely not perfect.  And management practices first developed there were being applied in other marine protected areas in other coral reef regions throughout the world.  My sixth perspective on the Great Barrier Reef was one in which that marine park, a paragon of how a country might protect a significant coral reef system, continued to be strengthened, all while threats to that park multiplied and signs of ecological stress became too obvious to ignore.  Despite the excellent park management, Australians were failing at the task of caring for the Great Barrier Reef.  Just this month, Andeas Dietzel from James Cook University and three colleagues published a report in Proceedings of the Royal Society B detailing the more than 50% decline in abundance of coral colonies of various size classes along the Great Barrier Reef between the mid-1990s and today.  Most of that loss is due to mortality caused by warming-induced bleaching, although other factors are also involved.

Change in abundance of coral taxa by colony size on the Great Barrer Reef between 1995/1996 and 2016/2017.  Histograms on left show change in size frequency.  Chart on right shows percent change in abundance for each of three size categories.  Image © Andreas Dietzel and colleagues.

During the first decade of this century, now based in Canada, I noticed the similarities in national attitudes of Australia and Canada to climate change.  Both countries have long relied on export of fossil fuels and other minerals for a significant part of their economies.  In Canada, the fuel has been mostly oil.  The hard to extract, hard to refine bitumen that exists in enormous quantities in northern Alberta has in recent years come to be the primary source, and Canada’s carbon footprint is high because of the reliance on this resource.  In Australia, the fuels have been gas and coal, the latter enormously abundant in deposits in Queensland and norther New South Wales.  Coal is the most carbon-intensive of the fossil fuels, and since a third of Australian coal is exported from ports along the Queensland coast, and growth in the industry is primarily within Queensland, that industry has direct negative impacts on the Great Barrier Reef as well as its impacts on climate change.

Both Canada and Australia have mediocre records when it comes to taking action on climate change, and politicians in both countries have plenty of reasons for the poor performance to trot out when questioned.  Mostly they rely on the fact that Canada contributes only 1.63% of global GHG emissions while Australia contributes just 1.28%.  What difference would it make if either country reduced its emissions?  This facile argument could be used by any nation other than the nine with higher percentages of total emissions than Canada (if the EU is considered a ‘nation’, it also falls higher on the percentage scale than Canada).  It’s a great argument for doing nothing to reduce your emissions! 

Both countries also take pains to claim that it is none of their business what overseas purchasers of their fossil fuels do with the fuel – in other words, producers/exporters of fossil fuels cannot be held accountable for the damage done by using those fuels.  The same argument exonerates gun manufacturers and producers of cigarettes from responsibility for the human suffering that results from use of those products.  Canada also tried making the pitch that we produce tar sands oil ethically and whined about being a northern country which means we have to burn lots of energy to heat our buildings.  (It’s hard to imagine how ethical bitumen extraction might differ from unethical extraction.)  Never mind the ethics; try out the northern excuse on Sweden (0.11% of emissions) or Norway (0.10%) which, last I looked, are even more northern than Canada. 

Enthusiastic about their fossil fuel resources, Australia and Canada subsidize their fossil fuel industries substantially.  In May 2019, the International Monetary Fund released a study of energy sector subsidies by country in 2015 and 2017.  The more comprehensive 2015 data (subsidies grew slightly overall by 2017) reveal Canada and Australia among the more active although by no means the most benevolent countries when it comes to subsidizing this industry with tax dollars.  According to IMF, global fossil fuel subsidies in 2015 were US$ 4.7 trillion or 6.3% of global GDP; that total grew slightly to US$ 5.2 trillion or 6.5% of GDP in 2017.  Using the online data behind this report reveals that Canadian 2015 subsidies total US$ 42.83 billion putting it 5th among a group of 39 ‘advanced’ countries, and 17th overall among some 191 countries.  Australia fared slightly better with US$ 28.51 billion in 2015 subsidies putting it 8th among the advanced countries and 25th overall.  On a per capita basis, Canada, subsidizing its fossil fuel industry at $ 1191.41 per person is 8th among the advanced countries and 27th overall, while Australia is slightly worse.  Australia’s $ 1198.02 per person in subsidies to its fossil fuel sector, is 7th among the advanced countries and 26th overall.  As a Canadian, I’d like to see my $1191 used for something more productive than digging up Alberta’s tar sands.  As someone who cares about the Great Barrier Reef, I’d like to see Australia scale back its subsidies as well.

Both Canada and Australia persisted for as long as they could in claiming climate change was unimportant.  Canada, under the leadership of political parties of both liberal and conservative persuasion, routinely said nice things about combatting climate change, even signed onto international agreements, notably the Kyoto Accord, and then did nothing.  When Stephen Harper came to power in 2006, his government had the misguided honesty to maintain that climate change was a trivial issue about which there was considerable scientific doubt.  It was a time in which Canadian government websites ceased talking about climate change, and government scientists were actively muzzled to ensure they’d not reveal any disturbing evidence.  During Harper’s tenure, however, Canadian politicians largely gave up on that quaintly flat earth view – it ceased being national policy with the end of the Harper government in 2015.  But I’m still waiting to see the aggressive action on climate change that in-coming Prime Minister Justin Trudeau promised (and spending those $40+ billion in subsidies somewhere else would be a good start).

I’m sad to see climate denial still a well-supported stance in Australia.  While Canada made a valiant effort to reform its posture at the 2015 Paris climate conference, and its delegates were central to getting the aspirational goal of +1.5oC written into the agreement, Australia continued its lacklustre, vote-for-the-minimum performance and won several more ‘Fossil’ awards to add to its collection.  (I don’t know whether the Climate Action Network has awarded more Fossils to Australia or to Canada, but both have been frequent winners of this dubious distinction at climate conferences since these awards first began at COP5, Bonn Germany, 1999.)  Canada has yet to announce any meaningful expansion of its woefully inadequate commitment on greenhouse gases made at Paris, but Australia appears now to be in danger of backtracking and there is even talk of leaving the Paris Agreement (for some unaccountable reason, many Aussie pols seem to admire Donald Trump’s actions on the world stage).

In truth there are good reasons why Australia has failed to move on emissions reduction.  Climate change denialism is alive and well in the Aussie population.  In a recent poll conducted by the University of Canberra early in 2020 of 40 countries, Australia had the third highest proportion of people who considered climate change unimportant.  This was a poll of people who consumed chiefly digital news.  True, the percentage considering climate change ‘not at all serious’ was only 8%, but the average among the 40 countries was 3%.  The percentage of Australian respondents considering climate change ‘extremely’ or ‘very serious’ (58%) was also lower than the average among countries (69%).  The 8% are more commonly found in rural districts, and so they have a greater effect than they might on electoral politics of Australia.  [The two more denying countries than Australia were Sweden (9%) and the USA (12%); Canada came in at 6%.]

The top end of the histogram showing the proportion of news consumers in each country that considered climate change not at all serious.  Image is from article in The Conversation redrawn from one in the U Canberra report, Digital News Report: Australia 2020.

These results are at first surprising given Australia’s recent experience with drought, fires and extreme heat, not to mention the Great Barrier Reef which has lost ~50% of the living coral it possessed in the mid 1990s.  In September, the British think tank, InfluenceMap, released a report that explored the way in which the fossil fuel industry has been particularly influential over a number of years both in lobbying governments on policies that would favor their industry and in dissemination of information designed to raise doubt about the science behind climate change.  In many ways, what they have uncovered is an Australian version of the effective denialism campaigns waged by the fossil fuel giants in the USA.  Influence Map also details how these same corporations have funded political parties and politician’s electoral campaigns, supporting both left-leaning and conservative parties.  The predictable result: government policies that favor continued development of fossil fuel resources, pay lip-service to, or act against activities that could hasten a transition towards a decarbonized society, and a sufficient population of supporters among the general public, particularly in less densely populated rural ridings which provide the core of support for right of center political parties.

Meanwhile, Aussie pols regularly denigrate the science community, and others who articulate the risks of unchecked climate change and demonstrate the evident impacts on the Great Barrer Reef and other parts of Australia’s environment.   What I find particularly depressing is the manner in which successive Aussie governments have paid lip-service to the need to curtail climate change while loudly proclaiming their intention to care for the Great Barrier Reef, while acting to support, if not strengthen the position of the fossil fuel sector in the economy.  They have, of course, been helped in this by Rupert Murdock’s News Corp, and its flagship paper, The Australian.

This, then, is my seventh and most recent perspective on the Great Barrier Reef.  A treasured icon, a national treasure, one that has been managed successfully, if not perfectly, since the 1970s that is being guaranteed a continuing decline by governments seduced by the fossil fuel industry into believing that there is no way forward for Australia that puts this coral reef marvel ahead of a continuing worship of the money to be made from digging up fossil fuels and shipping them out.  It’s a depressing perspective, signalling a national rejection of informed, inspired environmental management.  It is also one that risks collapsing the enormous success that environmental science has had in that nation.  Why spend money on learning how to better protect national icons like the Great Barrier Reef when protecting them prevents you continuing traditional carbon-intensive resource extraction?

Damaged by us, for sure, but still an incredible place, the Great Barrier Reef inspires as it reveals the superlatives of which time and evolution are capable.  Image © Trafalgar and The Real Word.

Will I get to gain an eighth perspective on the Great Barrier Reef?  That will depend on whether the Australian public demands better from their politicians than they have demanded until now.  From the other side of the world, I have no idea if that is possible.  But I’d like to believe that the pride, the sheer enjoyment, and even the reverence many Australians have come to see in the Great Barrier Reef provides a force capable of shifting the political leaders away from the enticements offered by Australia’s fossil fuel developers.  Time will tell.

Categories: Canada's environmental policies, Climate change, Coal, coral reef science, In the News, Politics, Tar Sands, Uncategorized | 1 Comment

Polar Regions Compete with Coral Reefs to Shout Out a Warning. Is Anyone Listening?


The number caught my eye.  Because of its immensity.  Twenty-eight trillion tonnes.  That is one hell of a lot of ice.  On the 23rd of August, The Guardian reported that planet Earth had lost 28 trillion tonnes of ice since 1994.  Slowly, over 30 years, it had melted away.  It was lost from glaciers, from the ice caps on Greenland and Antarctica, from coastal Arctic lands, from ice shelves that can be a couple of hundred meters thick, rising like great, glistening cliffs around Antarctica or northern Canada, and from floating sea ice.  Even from the upper reaches of Kilimanjaro.  The Guardian was referring to a new paper now under review, for eventual publication in The Chryosphere.  It appeared on-line on 14th August.  In it, Tom Slater of University of Leeds, and seven colleagues from that and other UK climate science research groups, reported on a series of calculations they had made using satellite-derived measurements of ice mass across the planet collected since the early 1990s.  These data were supplemented and confirmed with more direct measurements of ice loss in specific sites.  They calculated that immense number.

So, how much is 28 trillion tonnes of ice anyway?  A quick look at Google advised me that one cubic meter of ice weighs 919 kilograms.  Reminding myself that one tonne equals 1000 kg, and that a trillion is a thousand billion (the aging brain needs these mini-refresher courses), I realized that if one had a column of ice, 100 meters square (a column about the size of a small city block in size), it would need to rise 3,046,789,989 meters into the sky to weigh 28 trillion tonnes.  Assuming, of course, that the weight of ice did not melt, deform, or crush the bottom tiers, that 3 billion plus meters is roughly from here to the moon, and onward, eight times further.  Some of that ice, the sea ice, has not contributed to sea level rise.  But most of it has.  And the melting did not stop in 2017 (the final date in the Slater group’s calculations).  Yes, there remains a lot of ice on this planet, but the amount lost over those 30 years is still substantial – and most of us have been barely aware that it was happening.

The ability to simultaneously embrace two conflicting ideas is a strange human trait.  In 1936, F. Scott Fitzgerald said, “The test of a first-rate intelligence is the ability to hold two opposed ideas in mind at the same time and still retain the ability to function.”  He saw it as a valuable ability because ideas are usually biased by perspective and two apparently opposed ideas could be two different perspectives on a topic.  With more than one perspective you have greater options for effective action.

But what about the ability to cling to two conflicting ideas that are truly incompatible – say the idea that the Earth is flat and the idea that it is a sphere floating in space?  Or the idea that climate is only changing trivially or scarcely at all, and the idea that climate change is an existential threat to humanity?  Each idea may be supported by evidence, but they cannot both be correct.  The evidence supporting one is misleading. 

I think we have long since reached the point where the evidence supporting an argument that the changes we are seeing on this planet are merely natural variability around some average state – that evidence now pales into insignificance when contrasted with the abundant and growing evidence that the world’s climate is changing dramatically.  And yet, many of us continue to act as if climate change will only be a minor inconvenience, a triviality, compared to all those other truly important things that affect our lives – stock market gyrations, political unrest, income inequality, Presidential tweets.  This clinging to a belief that climate change will turn out to be ‘no big deal’ is not a mark of intelligence; it may be a sign of Pollyannaism run amok.  The sad fact is that whole governments are operating as if the climate crisis is a minor impediment to carrying on as usual.  It isn’t, and that column of ice stretching far beyond the moon shows how un-trivial climate change is.

The coral reefs of the world first delivered a mass bleaching event during the strong el Niño of 1982-83; reefs throughout the Galapagos, along the Pacific coast of Panama, and at some points north and south bleached severely.  The Galapagos reefs have never recovered.  Reefs delivered the first circumtropical mass bleaching episode during the even stronger el Niño of 1997-98, and they have continued to bleach intermittently.  Now the Great Barrier Reef has been hit by three severe bleaching events in 2016, 2017-18 and 2020 – only the 2016 event occurred during a strong el Niño.  Bleaching events are becoming more frequent and are less strongly tied to major el Niños than they were originally (see my comments here and earlier).  The global pattern is clear: something novel is happening, and it is happening more frequently year by year.  That novel thing is our warming of the planet and coral reefs have been shouting about it for almost forty years.  It is now apparent that the glaciers, the ice caps, the shelves and sea ice have also been shouting in their own quiet but inexorable way.  This world is warming fast, and the warming is changing the nature of the planet.  The world has been without stores of ice in the past, and its been without coral reefs in the past.  But at times when the world lacked reefs, or ice, it was a very different place to now, a place ill suited to sustaining our immense human economy.

Recent research reports make clear that the melting of ice has broad implications for the functioning of marine ecosystems, the productivity of marine fisheries, and the biodiversity of polar and alpine ecosystems.  The melting also has implications for global weather patterns, global ocean circulation, and most importantly for the rate of future climate warming.  The recent report from the Canadian Department of Fisheries and Oceans (DFO) on the state of the Canadian Arctic sets out clearly the importance of ice to Arctic environments, and how loss of ice is leading to dramatic changes in Arctic ecosystems.  Some of these changes may be positive, in the sense they will maintain or enhance opportunities for life, but many will be negative.  Unfortunately, our relative lack of understanding of how Arctic ecosystems function precludes any certainty on this topic.

Vast ice shelves many meters thick and extending kilometers from shore have long been a feature of polar landscapes.  The ice is permanent, in that it has been there for thousands of years.  And the ice supports an ecosystem adapted to its special features.  Now, Arctic ice shelves have largely disappeared.  The Milne Ice Shelf, on the northwest coast of Canada’s Ellesmere Island, was the last intact ice shelf in the Canadian Arctic until July 31st when it began to break up.  By August 6th, it had lost over 40% of its area as two large pieces (the bigger about the size of Manhattan Island) floated away.  Loss of ice shelves forces a reorganization of coastal ecosystems, disrupts the access by people to sea ice and the hunting that provides, and increases erosion of shorelines by ocean waves.

Recently, Mercé Casas-Prat and Xiaolan Wang of Environment and Climate Change Canada published results of their analysis of the effects of the loss of sea ice on wave height in the Arctic.  As summarized by the Globe and Mail, their article in Geophysical Research: Oceans modelled changes in periodicity and height of oceanic swells and coastal waves as climate change removes ice during the rest of this century.  They found open the average height of ocean swells could increase by almost six meters by 2080-2100, while coastal waves could grow by two meters.  These changes in average conditions will disrupt shipping and lead to widespread coastal erosion.  Canadian towns like Tuktoyuktak are already experiencing serious erosion that threatens infrastructure.

A more dynamic ocean will likely also hasten the breakup of sea ice, providing a positive feedback to warming and further storminess.  As Glenn Macgillivray wrote in the Globe and Mail on August 19th, it is clear as ice that ‘the Arctic is unravelling’.

Figure 2 from the Science article by K.M. Lewis and colleagues shows (top graph) that while the extent of open water in the Arctic has increased since 1998, the rate of increase is now slowing.  Yet the rate of primary production (bottom graph) continues a near-linear upward trend.  The middle graph reveals that the density of phytoplankton in the water column was almost unchanged through the early 2000s but has been increasing dramatically since 2008. Image © Science magazine.

One of the changes in the Arctic which might be positive is an increase in primary production – the photosynthesis by phytoplankton is increasing because the surface waters are warmer, the loss of ice is allowing light to penetrate further, and, in coastal areas, there is enhanced nutrients available because of the enhanced erosion.  As Stanford University’s K.M. Lewis and colleagues describe in their July 10th article in Science, there is considerable uncertainty in future trends in production because of the complex interactions among nutrients, water temperature, salinity, ice extent and storminess.  Their data reveal that while the increase in production was explained almost entirely by the increase in open water between 1998 and 2008, the increase since then has been due to an increase in the density of phytoplankton in the water column.  That increase in density can only be sustained by an increase in nutrients available, an increase which has likely been due to inputs via coastal erosion.  In the future, warmer and less saline surface waters may become sufficiently segregated from cooler, saltier, more nutrient-rich deeper waters curtailing the provision of nutrients to the phytoplankton.  Conversely, the stronger ocean swells and stormier weather anticipated may facilitate continued, or even enhanced delivery of nutrients from deeper waters.  Whatever the future trend, the substantial increase in productivity that has occurred over the past twenty years, and which will continue for at least the near future, has implications for fisheries production, and maintenance of Arctic biodiversity.

These changes in polar environments are being reported at a time when our confidence in the projections of future climate change is growing.  Any projection of a system’s state into the future, particularly for a complex system such as Earth’s climate, will entail some uncertainty.  Even the best models will never be able to account precisely for every butterfly wing flap that plays a role in determining our future climate.  As a result, we have gotten used to viewing projections of future temperature, rainfall, windspeed and so on as a mean projection, the best estimate, surrounded by an increasingly broad cone of possible futures for the measurement in question.  The best models provide the narrowest cones of uncertainty, and the good news is that the recent results of what is called the World Climate Research Programme (WCRP) have dramatically narrowed the uncertainty around future climate projections.

The improvement in estimates of climate sensitivity achieved in the WCRP study.  Image © Science.

Ever since 1979 when efforts to estimate the effects of CO2 on climate began in earnest, climate scientists have referred to ‘climate sensitivity’ — the likely average global temperature increase for a doubling of the CO2 concentration in the atmosphere.  This is a useful index for climate change, given that we have already increased atmospheric CO2 from the preindustrial ~280 ppm to above 417 ppm in the final week of May 2020.  That’s about a 49% increase or half a doubling.  But since 1979, the estimated climate sensitivity has stubbornly sat at about 1.5o to 4.5oC.  That is an enormous range, from an inconvenience to a disaster if it happened, but climate scientists could not do better, and we all had to remember that projections of climate contained this considerable uncertainty.

The efforts of the consortium within WCRP have reduced that uncertainty.  Now the world’s climate sensitivity is estimated as between 2.6o and 3.9oC.  What this means is that if we continue to add CO2 as we certainly will, at least in the sort term, and if atmospheric CO2 approaches 560 ppm, as it easily could, the average global temperature could increase between 2.6o and 3.9oC above preindustrial levels.  That increase still poses real problems for us and for the biosphere, but the extent of those problems is estimated much more precisely.  Which means that planning for adaptation and mitigation can proceed with greater certainty about what we will be up against in coming decades.

One thing’s for sure though.  Climate is changing, and the idea that the coming changes will have trivial effects is clearly incorrect.  The tropics and the Arctic are both changing dramatically now.  The world will be changing dramatically long before we get to 2100 unless we get serious about containing climate change.  Keeping the average global temperature increase to within 1.5oC above preindustrial temperatures is still an important and appropriate goal that we, collectively, have yet to get solidly behind.  It represents the amount of warming likely with less than a 50% increase in CO2 concentration from the preindustrial 280 ppm.  In other words, once the warming effects of the CO2 already in the atmosphere are fully realized, we are pretty well there – meaning there is absolutely no time to lose in cutting emissions.  We knew this was the case back in 2015!

The results of the new WCRP work to refine the estimate of climate sensitivity mean that the science is even more certain of this than it was before.  And that is why the current dithering of politicians of all shapes, sizes, and political stripe should be particularly concerning to all of us.

Climate change is real.  The biosphere is shouting out that we face a real emergency.  The science is better refined than ever before, so we have real certainty about what is coming and what we need to do.  And yet… politicians continue to hold onto their belief that ‘maybe things won’t get too bad’ or ‘maybe some small adjustments will suffice’.  Sort of like suggesting that the covid-19 pandemic will fade away any time now all by itself.

It’s way past time to act on climate change! Image ©Olivia Vanni/AP

Categories: Arctic, Changing Oceans, Climate change, coral reef science, In the News, Uncategorized | Comments Off on Polar Regions Compete with Coral Reefs to Shout Out a Warning. Is Anyone Listening?

Is There Any Future for Coral Reefs?


Back in March, I took a look at the state of climate change and the tasks facing nations if we are to limit average warming to 1.5oC.  Those tasks were, and remain, demanding.  Now we are enduring the covid-19 pandemic, and action on climate change has slowed perceptibly, even as the economic collapse leads to bluer skies, and much lower rates of CO2 emissions.  Meanwhile the warming has continued.

I have a book in press, due out in early 2021.  In it I refer to the increasingly slim chance that we will have anything resembling 20th century coral reefs by the end of this century, so I remain personally very interested in how coral reefs are doing these days.  Will that slim chance have vanished to no chance at all before the book even hits the market?  Or will something unexpected have happened that makes it laughable that we would be concerned at all for the well-being of these iconic oceanic wonders?

Bleached Acropora on the Great Barrier Reef.  It has happened again in 2020.  Image © ARC Centre of Excellence for Coral Reef Studies.

The warming has continued to cause trouble from time to time at locations around the world as sea surface temperatures reach critical thresholds for coral reefs.  This year, there was serious bleaching again along the Great Barrier Reef (the third major bleaching event there since 2016) as well as in some other southwest Pacific locations.  The media, preoccupied with Covid-19, paid little attention and it is hard to find reports of bleaching other than on the GBR.

The Great Barrier Reef bleaching event, like the ones that preceded it, however, has been particularly well documented because of the science and monitoring resources able to be thrown at it and the media have responded accordingly.  Once more, scientists from James Cook University were able to conduct aerial surveys along the full 1500 km of the reef region during the second half of March, making 11 flights in 9 days, surveying 1036 reefs and scoring them for extent of bleaching.  They also did some in-water ground-truthing of the surveys.  Work was curtailed as the country shut down because of covid-19.  Later this year, the James Cook team will be diving many of these reefs to determine the extent of mortality.

Of the 1036 surveyed reefs, 39.8% exhibited little or no bleaching (less than 10% of corals bleached).  But 25.1% were severely affected (meaning at least 60% of the corals in shallow water were bleached.  The remaining 35% showed moderate bleaching (i.e 10% to 60% of corals bleached).  Compared to the bleaching in 2016, there are more unbleached or lightly bleached reefs and fewer severely bleached reefs, making this the second most extreme event since the first extensive bleaching of the GBR in 1998.  However, in contrast to both 2016 and 2017, bleaching in 2020 has impacted reefs throughout the length of the GBR province.  At the far southern end, I’m told by others that shallow reef flat corals at Heron Reef were severely bleached but that bleaching deeper on the slopes was lower (20% to 40% of corals) and more variable.  Shallow corals at nearby One Tree Reef have also been bleached.  I’ll be watching for the official report on the surveys of this bleaching event.

These three maps show each of the reefs surveyed during each of the last three bleaching events along the Great Barrier Reef.  Red circles reflect >60% of coral colonies bleached.  Green circles reflect <10% of coral colonies bleached.  The remaining 35% of reefs surveyed, scattered among the reds and greens, are omitted from the figure but had intermediate levels of bleaching (10 – 60%). Image © ARC Centre of Excellence for Coral Reef Studies.

The most notable thing about Great Barrier Reef bleachings is that of the five major ones that have occurred, only 1998 and 2016 occurred during el Niño years when water temperatures might be unusually warm.  The others (2002, 2017, 2020) have occurred in non-el Niño years, showing that global warming has now reached the point, at least in the south-west Pacific, that typical temperature fluctuations due to local weather (heat waves) are sufficient to trigger bleaching.  February 2020 had the warmest sea surface temperatures ever recorded in the GBR region.

In the Caribbean, records have always shown that the degradation of reefs, as measured in loss of live coral cover, had been well under way long before climate change was on the scene.  This is also true of the GBR – until 2016, climate change was a distant third to explosions in numbers of Crown-of-thorns seastars, and cyclones, as causes of coral loss – but while significant loss of live coral cover was evident in the 1970s on the GBR, that downward trend in coral cover began in the 1950s in the Caribbean.  Climate change became important there in the 1980s and subsequently, but, unlike the Pacific, the Caribbean has suffered from a number of pandemic diseases of corals and other major organisms.  Diseases, while important in the Pacific and elsewhere, have been particularly destructive of Caribbean reef systems. 

Rapid progression of Stony Coral Tissue Loss Disease is shown in this time series of photos off St. Thomas, USVI.  Photo © Sonora Meiling and Science News.

There is a growing suspicion among scientists who study such things that the serious diseases prevalent in the Caribbean are themselves a consequence of the long-term degradation of reefs by a multitude of human activities.  The problem for corals is now being exacerbated by the warming due to climate change.  Among the most destructive causes for reef integrity have been the unidentified pathogen that virtually wiped out Diadema sea urchins throughout the Caribbean in 1983, removing a major reef herbivore that has never really recovered.  This facilitated a shift towards a much more algae-dominant reefscape.  White Band Disease, which was largely responsible for the near disappearance of Acropora palmata and A. cervicornis during the late 1970s and the 1980s, continues to crop up.  And Stony Coral Tissue Loss Disease (usually just called SCTLD) is a new one currently ravishing populations of about 20 coral species in the northern Caribbean (many of these species are among the ones less likely to bleach as water warms).

SCTLD, first seen in Florida in 2014, has since been sighted in many locations throughout the northern Caribbean, including sites along the Mexican Yucatan but not Belize, and as far south in the eastern Caribbean as St. Kitts and Nevis, according to data compiled by the AGRRA monitoring program.

Two recent papers provide new information on the current threats to Caribbean reefs (both are open access).  Aaron Muñiz-Castillo and Ernesto Arias, both from Centro de Investigación y de Estudios Avanzados del I.P.N. (CINVESTAV), Mérida, Mexico, and five colleagues from Mexican and U.S. labs, published an article late in 2019 in Scientific Reports.  Their article deals with the spatial and temporal pattern of heat stress faced by coral reefs across the Caribbean, and therefore with the way warming is influencing different parts of the Caribbean in different ways and to different extents.  Katie Cramer of Arizona State University, and six, chiefly U.S.-based colleagues published an article in Science Advances on 22nd April that concerns the temporal pattern of loss of the two species of Acropora.  Their article is sure to generate discomfort in a number of places because of the putative causes they list. 

Muñiz-Castillo and colleagues used remote sensing to plot heat stress variation over the period from 1985 to 2017 at sites throughout the Caribbean.  They showed, as expected, that heat stress was overall greater in more equatorial regions and in more recent years, but they revealed significant variation among locations in these trends.  They showed that heat stress does not map simply according to the ecoregions recognized across the Caribbean and proposed a new set of heat stress regions to be used when considering effects of warming in this region.  Among the most stressed, and most rapidly warming, locations are central and eastern Venezuela, the Honduran and Nicaraguan Miskito Keys, and the more southern Lesser Antilles along with the western Venezuelan coast, Aruba and Curaçao.  At the other extreme are the northern Lesser Antilles, most of the Mesoamerican Reef, and most of the Greater Antilles, the eastern Bahamas and Florida.  These least stressed regions may serve as heat refugia for coral reef systems.

The main message for me from their article is that patterns of heat stress vary significantly across the Caribbean and that, by knowing the local pattern, it is possible to infer likely relative heat stress in the future among locations.  All coral reefs, even within the Caribbean, are not experiencing the same thermal stress as the planet warms, and there may be opportunities to use the differences among locations in managing reefs more effectively.  For example, it would be wise to look after those putative heat refugia.

Cramer’s paper is a historical look at the decline in abundance of the two Acropora species found in the Caribbean – very historical in that it includes Pleistocene data.  When Tom Goreau first described the structure of Caribbean reefs in 1959, he named two of the nine zones he recognized as the cervicornis zone and the palmata zone because those two species tended to be overwhelmingly common at those parts of the reef.  He described the typical occurrence of A. palmata as starting at the top of the reef slope in “a narrow zone which is populated almost exclusively by huge tree-like colonies of Acropora palmata that take the full force of the surf. The great serried outliers of this coral are predominantly oriented in the direction of the prevailing seas which thus give the whole zone the characteristic appearance of a great jagged comb with irregular teeth….  In this region, Acropora palmata is clearly dominant and exists as a nearly pure population except on the sides of surge channels…  [To depths of 5 – 6 meters] Acropora palmata is still the dominant coral, growing in large isolated heads that also are strongly oriented into the prevailing seas”.  Needless to say, very few people diving today have ever seen those serried ramparts that formed the upper portion of most Caribbean reefs; that species, along with A. cervicornis, is on the endangered species list.

The crashes of those two iconic species were under way or about to begin as Goreau completed his article.  Cramer and colleagues have used a variety of types of data, from many locations across the Caribbean, and extending from Pleistocene times to the present.  While White Band Disease, which caused widespread die-offs of both species during the 1980s, has long been identified as a major factor, these new data show clearly that the decline in A. palmata was well under way at the time Goreau was working in Jamaica.

The proportion of reef sites with the species present (gray line) or dominant (black line), Pleistocene to the present.  The onset of White Band disease, and the Diadema die-off are both marked in red.  Stars mark the first period with a significant decline in abundance from Pleistocene levels.  Note that A. palmata is characteristic of reef crest sites and A. cervicornis is characteristic of midslope sites.  Image © K. Cramer and Science Advances.

At reef crests, the proportion of sites dominated by A. palmata declined from 78% during the Pleistocene to 6% in 2011.  Even by the 1950s, palmata abundance was significantly lower than in the Pleistocene.  At midslope sites, the prevalence of A. cervicornis declined from 63% of sites in the Pleistocene to 12% of sites in the 1960s.  Its prevalence has declined to <1% of sites at the present time.  Clearly, White Band Disease, or even White Band Disease and climate change are not the whole story here. 

In their search for drivers of these trends, Cramer and colleagues argue that several local human stresses have played major roles before WBD and climate change began their involvement.  In particular, they point to water quality, but their analysis is hampered by the lack of water quality data for reef locations even today.  (A little bit like Covid-19 testing, if you don’t monitor water quality, you cannot be asked or ordered to clean things up.)  The only long-term water quality data for the Caribbean – data on clarity for Belize and Puerto Rico – reveal a trend to increasing turbidity between 1993 and 2012.  Cramer and colleagues argue convincingly (at least to me) that the long-term decline of reefs coincides not only with increasing use of fertilizers on agricultural land, but also with increasing use of synthetic herbicides and pesticides.  Many of these are known to interfere with coral reproduction through effects on fecundity, larval development, and settlement success.  As well, human settlements near coastlines deliver a stream of pharmaceuticals and other chemicals through wastewater that can enter the reef environment.  These also have seldom been tested for their impacts on reef organisms.

I vividly remember a tiny pilot experiment Chris Metcalfe and other colleagues of mine carried out in the Yucatan in December-January 2008-2009.  With the help of experienced cave divers from the region, they deployed passive samplers in a series of cenotes that were downstream from tourism developments along the Mexican Riviera and in one cenote upstream from all development.  Water in these cave systems was all flowing towards the coast and would be expected to percolate up at offshore sites along the Mesoamerican Barrier Reef.  (Such sites are readily visible to a diver on the shallow forereef as the brackish water slowly mixes with surrounding salt water.)  They showed easily measurable concentrations of a variety of anthropogenic chemicals ranging from PCBs and organochloride pesticides to pharmaceuticals and illicit drugs.  Few of these compounds have been tested for toxicity to reef organisms such as corals.  Their results demonstrated clearly that runoff from agriculture and sewage from the hotel developments were entering the ocean along that shore.  But without time series of data, it is not possible to be certain that such chemicals have increased in abundance in reef waters – not possible to be certain, but does anyone really doubt this has happened as tourism has grown over the years?

In addition to onshore pollution, overfishing is the other local impact of people on reefs that could have played a major role.  Overfishing appears to have been rampant at many Caribbean sites but again there are not the long-term data across this region that would be necessary to test any trends in this factor against Cramer’s coral abundance data.

I think the main message from Cramer’s article is that while we spend plenty of time talking about the very real, and growing, link between climate change, bleaching and reef decline, we need to remember those other human impacts, that are still playing a role, although more locally.  They were sufficient to commence the deterioration of reefs before climate was a problem and mostly they are still acting.  The second message is the reminder that the trajectory for coral reefs in the Caribbean has been particularly severe, with diseases playing a much larger role than elsewhere.  The prevalence of these diseases is almost certainly also influenced by the various human stresses acting on reefs.

Coral-dominated reefs such as this one are getting harder to find as the various human-caused stresses act against them.  With loss of coral, the structural complexity of the habitat, and the rich biota characteristic of coral reefs disappears also.  Image © Robert S. Steneck.

A coral reef exists as an exquisite balance between calcification processes and a variety of forces of destruction, physical and biological.  As human use of the coastline increases, and as direct use of the reef increases, a multitude of human-caused stresses act to shift this equilibrium.  Whether we facilitate algal growth through overfishing of herbivores, reduce coral survivorship or reproductive success through pollution or climate change, or simply disrupt reefs physically through our sometimes thoughtless manipulation of coastal lands, dredging of navigation channels, or construction of artificial islands, our actions shift that equilibrium in the direction of reef degradation and decline.  We are now at a point where we have increased our impacts on many reefs so far that they are disappearing before our eyes.  My suggestion that we will not have anything resembling the coral reefs of the 1960s by the end of this century is not in danger of becoming obsolete before my book emerges next spring.  I wish I could be more positive about the future.  I would love for us all to begin acting in ways that will prove me wrong!

Categories: Changing Oceans, Climate change, coral reef science, diseases | Comments Off on Is There Any Future for Coral Reefs?