This weekend's 60 Minutes featured this great segment on coral reefs, in which a well-protected "Gardens of the Queen" in Cuba are used a possible example of a resilient reef ecosystem.
The segment touches on coral bleaching, though perhaps not with the authority or depth that is warranted by science. What's most striking, however, is that the segment does not even mention ocean acidification.
I'm sure the media conspiracy theorists might claim this all as evidence a U.S. network shying away from discussing "controversial" subjects like climate change. But I suspect something else is at play, and it is something that science communicators everywhere need to consider. This is television - you need engaging, interesting video. Just how do you film ocean acidification? It's a slow, invisible process, nothing like the exciting action shots of the host and scientists diving among sharks and lionfish.
This is not a criticism - it is a challenge. What are the best ways for documentarians to capture the effect of changing ocean chemistry on coral reefs?
Tuesday, December 20, 2011
60 Minutes on Coral Reefs and the challenge of depicting ocean acidification
Friday, August 26, 2011
Storm surge calculus
Jeff Masters' latest forecast for Hurricane Irene, besides warning New York City and coastal New England of damage, serves as a reminder of something to consider whenever you see a static map depicting what your community would look like if sea level rises by X m: the level of the sea is constantly varying, because of the astrononomical tides, storm systems and ocean currents.
On Sunday, New York City could be seriously damaged by the storm surge from Irene, even though the storm will have weakened to Category 1 at most, because the passage of the storm could coincide with a high tide:
At 9:30am EDT this morning, a wind analysis from NOAA/HRD (Figure 1) indicated that the potential storm surge damage from Irene rated a 5.1 on a scale of 0 to 6. This is equivalent to the storm surge a typical Category 4 hurricane would have. While this damage potential should gradually decline as Irene moves northwards and weakens, we can still expect a storm surge one full Saffir-Simpson Category higher than Irene's winds. Since tides are at their highest levels of the month this weekend due to the new moon, storm surge flooding will be at a maximum during the high tidal cycles that will occur at 8 pm Saturday night and 8 am Sunday morning. At those times, Irene is expected to be near the NC/VA border, then close to Long Island, NY, respectively. Thus, storm surge damage rivaling that experienced during Hurricane Isabel in 2003 is likely in northern NC, southern Maryland, and up Chesapeake Bay on Saturday night. It looks like Irene will pass New Jersey during low tide, which may limit the storm surge inundation to 3 - 6 feet there. Coastal New England from New York City to Massachusetts may also see storm surges characteristic of a Category 1 hurricane during Sunday morning's high tide, even if Irene has weakened to a tropical storm. I continue to give a 20% chance that a storm surge high enough to over-top the Manhattan flood walls and swamp the New York City subway system will occur on Sunday.
Monday, July 11, 2011
Farming the sea
Especially troubling, many of the most popular farmed species are carnivores, meaning they need to be fed at least partly with other fish. By one count, about 2 lb. of wild fish ground up to make fish meal is needed on average to produce 1 lb. of farmed fish, which leaves the ocean at a net loss.
I've written about this before: A substantial proportion of the wild harvest is used to maintain marine aquaculture of carnivorous species like salmon. It is wildly inefficient, the marine equivalent of farming wolves rather than herbivorous cattle. This is why many experts conclude that the future for pescetarians is probably the blander, lower-on-the-food-chain species like tilapia and catfish.
In coverage of aquaculture, we tend to focus on the sexier and scarier subjects: pollution from farms, genes mixing with the wild population, PCBs in farmed salmon, etc. Certainily, no doubt, these are all serious concerns (except perhaps the PCBs). But the feed-to-fish ratio is the very core of the matter; if you get less fish protein out than you put in, aquaculture doesn't make a heck of a lot of sense.
Walsh gets to this central dilemma in the second half of the article:
When producers began raising fish intensively, they picked species that people like to eat: salmon and sea bass. But those species are high on the food chain, and raising them on a farm is a bit like trying to domesticate tigers. [ed - nice. I always say wolves] The aquaculture industry has gotten better at replacing fish meal with plant-based feed, but not fast enough. You're not feeding the world sustainably if you need to remove the base of the marine food chain to do it.
The solution that many propose is expanding the use of plant-based products in fish food. That brings it's own complications. For one, salmon certainly didn't evolve eating soymeal, cornmeal or wheat, so shifting to a majority plant-based diet will likely involve further genetic engineering, which has supporters and detractors.
And second, feeding plant products to fish would add another player in the struggle for the world's productive croplands.
Forget food vs. feed. Or food vs. fuel. In the future, it will be a battle of the 4 Fs: food vs. feed vs. fuel vs. fish.
Wednesday, April 06, 2011
Faster sailing across the Central Pacific: Wind speeds and El Nino
The new paper by Young et al. about increasing wind speeds and wave heights over the past twenty years created a bit of a buzz in the climate science world, not to mention the sailing world. Finally some good news, the windsurfer in me first upon seeing the paper.
The paper itself does not speculate about whether human-caused climate change is the driver of the global trend in wind speeds. That may have been a wise choise, as it would be difficult, statistically or dynamically, to attribute the rend in the reasonably short time series (~23 years) to any single forcing factor.
The spatial pattern, however, is quite striking:
If there were no labels on this figure, I'd have guessed it was the trend in sea surface temperatures over the same time period. The steepest trend is in the Central Pacific, including the waters around the Gilbert and Phoenix Islands of Kiribati.
In a map of temperature trends over the past two to three decades, the Central Pacific should jump out because of the increasing frequency of "Central Pacific" El Nino events, also known as El Nino Modoki. The more freuqent occurences of the "CP" El Nino is a subject of much research, and has been attributed by some authors to climate warming. The CP El Nino is responsible for a number of mass coral bleaching events, including 2002-3 in the Phoenix Islands, 2004-5 in the Gilbert Islands, and 2009-10 across the whole region.
It is not surprising to find a similar -- at least visually, take this with a grain of salt, I've not done the statistics -- spatial pattern in the surface wind speeds across the Pacific. More frequent Central Pacific warm events likely means larger pressure gradients, more convergence, and higher winds across the region (my paper in the Atoll Research Bulletin describesa CP El Nino event in relatively lay terms). More analysis will need to be done, but at first glance, the wind speed trends over the Pacific appear to be driven by temperature trends and the status of climate oscillations, which themselves may be driven in part by climate change.
Monday, March 14, 2011
Climate change and the oceans; UCAR Magazine
The UCAR Magazine has a good short review of recent research into the ocean's response to climate change. Bob Henson manages to summarize some of the new thinking about coral bleaching, plankton productivity, ocean acidification, and ocean "deoxygenation" all in one article. It's worth a read.
Monday, March 07, 2011
Banning the trade of shark fins
I took the picture at left just a couple weeks back in a market on the Pacific Coast of Central America. Frankly, it the photo could be from the Indian Ocean, the Caribbean or the western Pacific, I've seen the same thing on the coasts of all the tropical oceans.
You'll notice the fin-less sharks in the bin are all small: the larger sharks are dumped at sea after being "finned". The fin is worth so much more than the meat that there's no value in bringing a big heavy dead shark back ashore, even though it is obviously a potential food source. In Kiribati, people do catch sharks and sell the fins, but at least they also take the shark home to eat.
You don't have to be the least bit interested in marine conservation or the dwindling global shark population to see the practice as finning and leaving the shark behind as ridiculously wasteful. Perhaps a ban of shark fishing may be politically or logistically impossible in today's world, I don't know. I can say that if we are going to continue to catch sharks for human consumption, let's at least catch the whole shark.
Friday, November 19, 2010
Summary of Caribbean Bleaching in PLoS-One by Eakin et al.
The new paper by Eakin et al. in PLoS-One (open access) summarizes the extent of the 2005 coral bleaching event in the Caribbean, an event discussed at length on Maribo. The paper includes data from dozens of coral reef sites across the Caribbean that were affected by the prolonged period of water water in the late summer and fall of 2005, the same unusual warmth which helped promote the strong Atlantic hurricane season. The figures at right give an idea of the scale of the event, and the scale of the data collected by Eakin et al. The top panel shows the heat stress ("degree heating weeks") experienced by reefs across the Caribbean; the lower panel summarize the percent of corals in each region that bleached (data is collected in some cases by counting number of bleaching colonies, in others by estimating the percent of total coral cover that bleached). The figure shows that bleaching tended to be the most extensive in the areas that experienced the greatest heat stress, particularly the core of the "hot spot" in the Lesser Antilles.
We've seen a near repeat of this event in the past few months; the effect of the follow-up event on living coral cover won't be known for some time. From a climate standpoint. The fact that it has happened again five years later is, in itself, remarkable. Eakin et al. report that the sea surface temperatures in the fall of 2005 were the warmest since records began in the mid-1800s. The new record appears to have only lasted five years.
Monday, October 25, 2010
Climate change and the Caribbean coral bleaching, again
When I give talks about climate change and coral reefs, I almost always use the two slides on the right. The first slide is a map of "degree heating weeks" (DHW), a measure of accumulated heat stress experienced by corals, in the Caribbean in mid-October in 2005. Severe bleaching and coral morality is typically observed when the values of DHW exceed 8 deg C-week. Basically, the same long period of warm water temperatures that helps spawn the destructive 2005 Atlantic hurricane season caused unprecedented coral bleaching event in the eastern Caribbean.
Five years later, a Caribbean "heat wave" has happened again. I've been writing for months that there was a strong likelihood of extensive coral bleaching in the Caribbean this fall according to NOAA's advance forecast of sea surface temperatures (in fact, we had a good inkling of this last summer). Now we're getting reports of bleaching from observers in the Caribbean. Add this to the observations (following predictions, once again!) from Southeast Asia and the Equatorial Pacific, and we have what may be the most, or second most, extensive "global" coral bleaching event in recorded history.
For all those writing about this event, keep in mind the predictions. This is what the scientific community predicted was likely to happen. An event which we calculated would be a once in a millennium occurrence without human impact on the climate, happened again five years later.
There are caveats, for sure. There is uncertainty in the model simulations of interannual variability which can affect the specific calculations of odds (see the 2007 paper for some details). And once-in-a-thousand year events can in reality happen five years apart; we'd need to collect data for thousands and thousands of years to properly calculate the statistics. Obviously, that's not feasible, which is the very reason we have computers help us do the math on these problems.
The real climate doesn't care about the political climate.
Monday, September 28, 2009
Important viewing on corals
It is worth taking the time to watch Charlie Veron's talk "Is the Great Barrier Reef on Death Row?", presented at the British Royal society earlier in the summer. A version of this talk inspired Chris Turner's terrific article in this month's issue of the Walrus.
Veron literally wrote the book about corals. His three volume tome Corals of the World has a prominent place on the shelf of every coral reef scientist. In 2008, he published a paper in the journal Coral Reefswhich posited that CO2-related changes in ocean chemistry, like what is happening today, may have contributed the five mass marine extinctions in the geological record. It was awarded the best paper of the year by the International Society of Reef Sciences.
Monday, September 21, 2009
Important listening and reading on the oceans
A week ago, CBC's Quirks and Quarks did a full one-hour episode on the state of the world's oceans. The show is a one-stop shop for learning about dead zones, ocean acidification, coral bleaching (my bit), overfishing and the Pacific Garbage Patch.
The October issue of Canadian literary magazine the Walrus also has a long meditation by Chris Turner on the "anthropocene", ocean acidification and the fate of the Great Barrier Reef, based in part on the thoughts of the dean of corals Charlie Veron.
Thursday, September 17, 2009
The slippery slope to slime
Overfishing and increasing ocean dead zones are thought to be leading us on a oceans dominated by fleshy algae and jellyfish, a trend coined the "slippery slope to slime" by Jeremy Jackson. This photo is from Fast Company:
fishermen in the Sea of Japan are tormented by invasive swarms of Echizen Kurage (Nomura's jellyfish), a giant jellyfish that weighs up to 450 pounds and measures two meters wide... The students capture Nomura's jellyfish in fixed fishing nets from a lake in Fukui prefecture, an area plagued by the swarms.
Friday, August 21, 2009
Hurricane Bill, the Atlantic hurricane season and Pacific warming
The first Atlantic hurricane of the season, Hurricane Bill, is on its way north towards the east coast of Canada (and creating huge waves in Bermuda and the northeastern US). Forecasters expect Bill to pass the coast of Nova Scotia on Sunday and run towards Newfoundland and Labrador.
The offshore path of the first and only hurricane of the Atlantic season brings to mind an interesting paper published earlier this summer, that warrants more attention than (I think) it received. In this post a few weeks back, before I disappeared for the Ontario leg of the Canadian Summer of ’09 heat wave tour (ah, Rex Murphy, what happened to global cooling?), I briefly mentioned the paper by Kim et al. that looked at the response of Atlantic hurricane activity to different types of El Nino events.
The conventional thinking is that Atlantic hurricane activity is low during El Nino events. Basically, the increase in eastern and central equatorial Pacific Ocean temperatures that happens during El Ninos shifts upper-level atmospheric circulation, which in turn, creates wind shear in Atlantic that disrupts hurricane activity.
Kim et al. went an important a step further. They found that the relationship depends on the nature of the Pacific warming.
The above figure tells the story. When the warming occurs throughout the eastern equatorial Pacific (EPW), the more classic El Nino, there are significantly fewer hurricanes in the in the Caribbean and up the eastern seaboard of North America. When warming is centered in central equatorial Pacific (CPW), as happened in 2002 and 2004, there actually is a significant increase in hurricanes reaching North America. Central Pacific warming events basically cause less vertical wind shear.
The ongoing development of El Nino conditions in the Pacific is the major reason for predictions of a less active than normal hurricane season in the Atlantic (and an active eastern Pacific season). That Pacific surface temperature anomaly is currently centered in the eastern Pacific, which suggests that all other factors being equal, which of course they never are, there is a higher likelihood of hurricane track density depicted in Part A of the figure above.
Now one hurricane does not a season make: you could argue that Bill's track is loosely bucking that prediction. Nonetheless, it will be interesting to follow hurricane development this year, and during the next episode of central Pacific warming, to see whether Kim et al. are correct in asserting that location of all those flapping butterflies in the Pacific predictably determines the development of storms in the Atlantic.
Thursday, July 23, 2009
El Nino and the likelihood of mass coral bleaching
The seasonal forecasting system recently developed by NOAA Coral Reef Watch suggests that coral reefs in the Caribbean and in part of the central equatorial Pacific (the Line Islands, including Kiritimati or "Christmas Island") are at risk of coral bleaching in the coming months due to warm ocean temperatures. The forecast is due to the seeming return of El Nino in the Pacific.
The word from the NOAA Climate Prediction Center is that El Nino conditions are expected to prevail though the winter. Climate buffs can "see" the El Nino development in maps of sea surface temperature anomalies (warm water in the central and eastern Pacific) the thermocline (deepening in the eastern Pacific, meaning less upwelling off of South America) and sea surface height (the wind reversal on the equator means higher water in the central and eastern Pacific).
Not all El Nino events are created equal, and the models currently disagree on the current trajectory. This is especially important to remember when predicting the effect that El Nino conditions may have on other parts of the planet, what we luddites call "teleconnections". For example, a terrific paper by Kim et al. in Science demonstrated clear differences between the effect of "central pacific warming" and "eastern pacific warming" - which can both be classified as an El Nino event, depending what metric is applied - on ocean temperatures and hurricane tracks in the Caribbean.
One silver lining: For people living in the central Pacific, especially the parched islands of the southern Gilberts (Kiribati) Islands like Arorae, the development of El Nino conditions hopefully also means an end to the two-year drought that has claimed many of the coconut trees.
UPDATE: More on the Caribbean bleaching threat here
Tuesday, June 02, 2009
Coping with Commitment: New study on the challenge facing coral reefs
Maribo's back from a long hiatus, during which the host was overseas collecting data, samples and unfortunately some sort of parasite.
Good timing, for the return home, not the parasite, since a new study of mine on climate change and coral reefs appeared in PLOS-One today (link - no subscription required).
As many of the regular readers have heard before, one of the biggest challenges posed by climate change is the timing.
First, you have the time lag between greenhouse gas emissions and the climate effect of those emissions. Basically, it takes time for the big complicated mix of atmosphere, ocean, land and ice to come to equilibrium. That’s why you sometimes here the climate compared to a big ship. You can hit the brakes but it will take a while for ship to actually come to a stop. Similarly, even if we froze emissions today, the climate would continue to warm a bit, because that warming is physically built into the system. This is often referred to as "committed warming".
Society may impart a second warming commitment. There is a lag between the decision to take action and the action itself. Using the ship analogy, it takes time for the officers on deck who first see the iceberg to relay the message to the captain. In other words, even if we decided to drastically emissions tomorrow, those reductions would not occur for some time. Hence all the hysteria about the construction of new coal-burning power plants. Since coals plants may last for decades they come with a considerable emissions “commitment”.
The new study looks at the implications of “committed warming” for conserving the world's coral reefs.
The dangerous impacts of climate change on coral reef are expected to occur sooner than most other prominently discussed climate change impacts (e.g. ice sheet melt, rainfall shifts in the topics). Why? Water temperatures, only 1-2 degrees Celsius over the usual summer maximum temperatures can cause bleaching of corals and some other reef organisms. Bleaching, described here many times, is the paling of the corals caused by a breakdown of the symbiosis between the reef-building animals themselves and the colourful algae that live in the coral tissue. A bleached coral is still alive, but is deprived of its primary energy source. If the conditions persist, the bleached coral can die.
Now, corals can grow back after a bleaching event, just as trees grow back after a fire, but it takes time. If bleaching events happen too often – say, because of ocean warming - most corals and the ecosystem as a whole will be unable to recover. Now, combine that with the rise in CO2 levels reducing the ability of corals to actually build the reef, and you’ve got one of the most threatened ecosystems on the planet.
This new study evaluates the “committed" frequency of bleaching events, and what it all means for coral reef conservation and for climate policy. The results show that the physical commitment alone is enough to make bleaching events harmfully frequent at over half of the world’s reefs by the end of the century. A possible additional commitment, caused by the time required to shift from a “business-as-usual” future to a GHG “mitigation” future, may cause over 80% of the world’s coral reefs to experience harmfully frequent events by 2030.
There is a possible silver lining. Thermal adaptation of 1.5 degrees C, whether via biological mechanisms, coral community changes or extreme management interventions, could postpone the forecast for 50-80 years in the “business-as-usual" case. That could provide time to change the trajectory of greenhouse gas emissions and then prevent the majority of the world's reefs from experiencing harmfully frequent bleaching events this century.
Let's be clear. This is no panacea - the ecological costs of proposed adaptive mechanisms and the implications for climate policy are outlined in the discussions. Here's the final paragraph:
In summary, the results of this study indicate that a combination of greenhouse gas mitigation and improved coral reef management will be required to avoid the degradation of the world’s coral reef ecosystems from frequent mass coral bleaching events. Actions that enhance reef resistance and reef resilience - including protection of bleaching-resistant reefs, reduction of other stressors, and possibly even more radical suggestions like “seeding” reefs with more temperature-tolerant species of Symbiodinium – may be necessary to help coral reef ecosystems endure through the committed warming over the next several decades. These management actions, while important, will alone prove to be insufficient to protect coral reefs through the latter half of the century. The difference between the future scenarios presented in this study demonstrates that protecting the world’s coral reefs from increasing thermal stress will require a dramatic reduction in greenhouse gas emissions over the next several decades.
Sunday, February 08, 2009
Levelling the science of sea-level rise
One of my biggest pet peeves with the climate change communication world is widespread use of sea-level rise ‘maps’. There are countless maps and animations out there. Think the simulated flooding of New York in An Inconvenient Truth or, for a local example, the Sierra Club’s post-Greenland map of Vancouver in which my home becomes coveted waterfront property. Anyone with a digital elevation dataset and some GIS skills can draw a map of what land will “disappear” if the sea level rises by 6 m, or 6 km for that matter.
Leave aside for now the uncertainty about future rates of sea-level rise, the usual beef with graphic representations of sea level rise. Spend a few weeks in a coral atoll and you’ll know the real problem with these simplistic graphics. The sea is not actually level. And there’s no scientific reason to think that the rise will be. A part of this issue is tackled in a terrific new paper by Mitrovica et al. in last week’s Science.
The paper estimates the regional variation in sea level rise that would occur from the melting of the West Antarctic Ice Sheet (WAIS). Unlike the brute force mapping exercises, Mitrovica et al. consider the actual physics of the ice melt, including gravitational attraction of the ice sheet, migration of shorelines and the effect of all that ice on the Earth’s rotations. For example:
The rapid melting of ice sheets and glaciers leads to a sea-level change that departs dramatically from the assumption of a uniform redistribution of meltwater (4). An ice sheet exerts a gravitational attraction on the nearby ocean and thus draws water toward it. If the ice sheet melts, this attraction will be reduced, and water will migrate away from the ice sheet. The net effect, despite the increase in the total volume of the oceans after a melting event, is that sea level will actually fall within ~2000 km of the collapsing ice sheet and progressively increase as one moves further from this region. Each ice reservoir will produce a distinct geometry, or fingerprint, of sea-level change... Although the physics of fingerprinting has been embraced in studies of past sea-level change, it has been largely ignored in discussions of future projections.
The conclusion which drew media attention (the Globe and Mail) and a bold-ed and italicized post from Joe Romm is that sea-level rise from melting of WAIS will be higher along will the coastlines of North America, including cities like Washington, DC, New York, and Vancouver.
The media coverage is not wrong, but misses the point. The paper demonstrates how melting of an ice sheet leads to uneven sea level rise, using WAIS as an example. In reality, if all of WAIS were to melt, so presumably would some or all of the Greenland Ice Sheet, the East Antarctica Ice Sheet and the mountain glaciers. The melting of all that other ice would also influence the geography of sea level rise. The take home message of the paper is not we need to start sandbagging along English Bay beaches here in Vancouver. The message is that the scientific community – and I assume by extension the environmental community – needs to remember that the oceans’ rise will not be level. The concluding sentences of the paper:
Any robust assessment of the sea-level hazard associated with the loss of major ice reservoirs must, of course, account for other potential sources of meltwater, namely Greenland, the East Antarctic, and mountain glaciers. Nevertheless, future projections should avoid simple, eustatic estimates and be based on a suitably complete sea-level theory.
Amen to that.
[You can give thanks for this post to my father, who notified me of the Mitrovica et al. press coverage, and who many of you know through the macro-economic advice he periodically delivers in the Toronto Star, The Globe and Mail and on the CBC. Forget my deranged comments on economics – he is the one they really should be calling to fix the federal budget.]
Monday, February 02, 2009
Skepticism about corals and rising CO2
The recent spate of "skeptical" climate change reporting and posting - which I personally feel is largely weather and opportunity-based - have included some serious misinterpretations and misrepresentations of coral reef science. For example, Climate Shifts tells the story of an amusing report from the "Center for the Study of Carbon Dioxide and Climate Change".
The latest screed comes from Watts up with that goes after the threat of rising CO2:
This does indeed sound alarming, until you consider that corals became common in the oceans during the Ordovician Era - nearly 500 million years ago - when atmospheric CO2 levels were about 10X greater than they are today.
What follows is a graph of temperature and CO2 over the past several hundred million years which I'll let the geologist argue over.
Now like the author of that post, I'm not one of the world's experts on reef development. So, instead, let me defer to one. This is a quote from the beginning of Charlie Veron's Corals of the World (page 33-34), the three volume tome found on the shelf of pretty much every reef scientist out there:
By the Middle Ordovician, complex algae and invertebrate reef communities had become widespread and reef biota had diversified... Reef development reached a peak in the Devonian Period and even after all this time, what remains today of those reefs are sometimes of awesome size... Corals were seldom the dominant organisms of Devonian reefs although rugose corals are often abundant in them and have a wide variety of growth-forms. Tabulate corals, which were a less varied group, mostly occupied protected or inter-reef environments.
There were reefs during those earlier era. Read on:
Unlike the Scleractinia (ed - the order of stony corals found today), both these groups of corals made excellent fossils becauase their skeletons were made of calcite, a far more stable form of calcium carbonate that the aragonite skeltons of Scleractinia.
Yes, corals evolved over time. Today's coral species date back in the tens not the many hundreds of millions of years. The type of calcium carbonate (aragonite) today's corals secrete is more sensitive to changes in the CO2 or carbonate concentration, no doubt in part because those corals have persisted through a period in which CO2 was lower than today.
Any reef experts wish to comment?
Update: A reader reminded me of this recent article by Veron in the journal Coral Reefs. The author hypothesizes that high CO2 /acidification may have caused some of the major marine extinction events in the geological past. It also addresses the very question of whether corals could have persisted in a high CO2 world in the past:
Two possibilities present themselves: (1) Reefs may not have proliferated at all
during CO2 highs; they may just appear to have survived because they were able to resume growth when levels fell. (2) The high apparent CO2 levels of ancient times may be
an artefact of a lack of data and measuring method.
Veron also again addresses the fact that today's corals are different:
Reef proliferation in the distant past during periods when atmospheric CO2 may have been high could mean that the reef builders and consolidators were better adapted to these conditions and could exploit the enhanced calcification and photosynthesis promoted by warmer sea surface temperatures without adverse effects. Many organisms in the ancient oceans would have been more tolerant to acidification through their dependence on calcitic skeletons rather than aragonite or high-magnesium calcite. There may have been other aspects of coral biology that allowed ancient corals to tolerate water chemistries that are lethal to today’s Scleractinia. If so, it would be more than interesting to know what those physiological mechanisms were.
Friday, January 30, 2009
Monaco Declaration on Ocean Acidification
A group of the world's experts on ocean chemistry and marine ecosystems are calling for immediate action on CO2 emissions to avoid further damage to the oceans (link to pdf). The
"Monaco Declaration" is the outcome of the second "The Ocean in a High-CO2 World" international symposium.
Here's their take-home message:
Ocean acidification can be controlled only by limiting future atmospheric CO2 levels. So-called geo-engineering strategies that would not aim to restrict future atmospheric CO2 concentrations would not reduce ocean acidification. Mitigation strategies that aim to transfer CO2 to the ocean, for example by direct deepsea disposal of CO2 or by fertilising the ocean to stimulate biological productivity, would enhance ocean acidification in some areas while reducing it in others.
Climate-change negotiations focused on stabilizing greenhouse gases must consider not only the total radiation balance; they must also consider atmospheric CO2 as a pollutant, an acid gas whose release to the atmosphere must be curtailed in order to limit ocean acidification. Hence, limits (stabilization targets) for atmospheric CO2 defined based on ocean acidification may differ from those based on surface temperature increases and climate change. Despite a seemingly bleak outlook, there remains hope.
We have a choice, and there is still time to act if serious and sustained actions are initiated without further delay. First and foremost, policymakers need to realize that ocean acidification is not a peripheral issue. It is the other CO2 problem that must be grappled with alongside climate change. Reining in this double threat, caused by our dependence on fossil fuels, is the challenge of the century.
Solving this problem will require a monumental worldwide effort. All countries must contribute, and developed countries must lead by example and by engineering new technologies to help solve the problem. Promoting these technologies will be rewarded economically, and prevention of severe environmental degradation will be far less costly for all nations than would be trying to live with the consequences of the present approach where CO2 emissions and atmospheric CO2 concentrations continue to increase, year after year.
Fortunately, partial remedies already on the table, if implemented together, could solve most of the problem. We must start to act now because it will take years to change the energy infrastructure and to overcome the atmosphere’s accumulation of excess CO2, which takes time to invade the ocean.
Sunday, January 11, 2009
Bush protects remote Pacific Islands
Maribo began last year with an "elevator figure" describing the threat that climate change poses to the world's coral reefs. This year, we'll begin with some good news.
In a decision that has drawn widespread applause from scientists and conservationists, and had a lot of reporters scrambling for an atlas, the outgoing US President used a century-old antiquities law to create three huge marine protected areas or "national monuments" out in the middle of the Pacific Ocean. Two of the monuments protect the Marianas Trench, offshore of the Northern Marianas Islands, and Rose Atoll, an isolated atoll north of American Samoa. The third, grouped together as the "Pacific Remote Islands", includes the water around seven "islands": Kingman Reef and Palmyra Atoll, Wake Island, Johnston Atoll, Howland, Baker, and Jarvis Island
These places are probably only be known to WWII buffs, marine scientists or members of the military -- they are almost all either off limits to non-military personnel (e.g. Johnston), uninhabited (Rose), or uninhabitable (landless Kingman). But these islands, especially the Pacific Remote Islands, are exciting to scientists.
Kingman Reef and Palmyra Atoll were the subjects of an extensive biological survey co-ordinated by colleagues at Scripps and National Geographic a couple years ago. Kingman is generally considered "pristine"; the survey found an "inverted" food web, dominated by large predators like sharks, thanks to the lack of human pressure and also to favourable currents.
While Kingman and Palmyra have more of the fanfare, I'd bet that Howland, Baker and Jarvis could prove to be just as important. They lie closer to the equator, in an area more directly affected by the El Nino / Southern Oscillation. Thanks to tempermental El Nino, the surface waters in the area can be highly variable, at least by equatorial standards. The reefs may - that is may, not will - help us better understand if and how corals can acclimate or adapt to heat stress (not that this is mentioned in the lengthy White House press release).
Sunday, November 30, 2008
Farming the oceans
An NY Times article a couple weeks back included this snapshot of global fisheries decline, based on data compiled by the experts here at the UBC Sea Around Us Project. The image tells the story of the article, a story not repeated often enough. Without a drastic change in management, we are nearing the end of the wild harvest in fish.
The world is in the middle of phase transition from wild harvest to farming, similar to what happened with land animals. The depletion of the natural resource itself is driven in part by the rapid transition to an energy-intensive farming industry. Consider the proportion of wild fisheries required to support fish and animal feed:
Nearly one-third of the world’s wild-caught fish are reduced to fish meal and fed to farmed fish and cattle and pigs. Aquaculture alone consumes an estimated 53 percent of the world’s fish meal and 87 percent of its fish oil. (To make matters worse, as much as a quarter of the total wild catch is thrown back — dead — as “bycatch.”)
A substantial proportion of the wild harvest is used to maintain marine aquaculture of carnivorous species like salmon. It is wildly inefficient, the marine equivalent of farming wolves rather than herbivorous cattle. This is why many experts conclude that the future for pescetarians is probably the blander, lower-on-the-food-chain species like tilapia and catfish. Continued consumption of popular favourites like tuna and salmon could only happen with drastic improvements in fisheries management.
Marine aquaculture shares many of the shortcomings of industrial animal agriculture. A high input of energy (fish meal, animal feed) is required per unit of food production. Also, a large proportion of the natural resource base (wild-caught fish, agricultural land) must be used to produce the inputs. Finally, research concludes that shifting towards less energy-intensive options (lower on the food chain or "closer to the sun", effectively the same statement) would help sustain the natural resource.
Sure, fish did not evolve to eat grain. Then again, neither did cattle.
Saturday, November 15, 2008
Tracking changes in CO2
The NOAA Coral Reef Watch program has a new "ocean acidification" online tool that maps changes in ocean chemistry brought about by rising carbon dioxide concentrations. The information is critical to understanding the long-term threats to coral reefs.
Here's a brief explanation (see NOAA's site for more):
Carbon dioxide dissolves in water - that's how you make a carbonated beverage. Around one-quarter to one-third of the CO2 emissions from human activity each year are absorbed by the oceans. The CO2 react with water to form carbonic acid (H2CO3), reducing pH in the process. That's where we get the term "ocean acidification".
The central concern for coral reefs is that this alters the balance of the common dissolved carbon compounds. The process of "buffering" the pH change consumes carbonate ions (CO3--) which corals and other calcifying organisms use to build their skeletons. So as CO2 levels increase, the proportion of ocean carbonate decreases, and the ability of corals to build reefs decreases. The slower-growing, weaker reefs are then more vulnerable to erosion. This can be seen today in parts of the eastern equatorial Pacific like the Galapagos, where corals do persist but naturally high carbon dioxide levels (from upwelling of high pCO2 deep waters) limit reef growth and ecosystem development.
