On the Decline of Coral Reef Ecosystems (II): John Bruno Responds

Coral White Syndrome

As the lead author of the recent articles on coral disease outbreaks on the GBR and Indo-Pacific reef decline, Dr John Bruno raises some valid points regarding the recent critique on the decline of GBR corals by Peter Ridd:


Ove, thanks for posting Peter Ridd’s critique of Pandolfi et al. 2003. I’d be interested in hearing from Peter about whether he had a hard time getting this published and what type of reaction he got from reviewers at journals like Science or Coral Reefs. Although I agreed with some of his specific criticisms of the methodology used by Pandolfi et al., Peter’s overall arguments about the status of the GBR are demonstrably incorrect. Below I briefly comment on some his main problems (in caps) and points (in quotes) and correct some of his major errors about the state of reef-building corals on the GBR. PROBLEM 1: EFFECT OF WEIGHTING OF THE GUILDS
“The problem with equal weighting of the guilds is that the fundamental importance of corals to coral reef ecosystems is not adequately recognized.”I totally agree. This seems like a major flaw. But I imagine that the authors would respond that their intent was to quantify the status of entire reef ecosystems, including food web structure and trophic dynamics. I certainly agree that a reef without large vertebrates is aesthetically and ecologically impoverished. But it is hard to ignore the fact that without corals you have no ecosystem but without top predators you just have an altered and possibly “degraded” ecosystem.As Peter (sorry for the informality, but the Dr. Ridd said, Dr. Bruno replied thing feels a bit stuffy to me in a blog discussion) succinctly states, “coral reefs cannot exist without reef-building corals.” A seemingly obvious point that is sometimes lost.“Because the guilds and species that are subject to human exploitation (e.g. large herbivores) are often in worse state than corals”
As I discuss below, this is not the case due to the indirect and often long distance effects of humans on corals.

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Glaciers dominate eustatic sea-level rise in the 21st Century

Glacier



Sheet ice dynamics and glacial meltwater have been somewhat of a contentious issue in the past (link, read more). Mark Meier and colleagues from the Institute of Arctic and Alpine Research, University of Colorado have made the headlines in the journal Science magazine recently:




Ice loss to the sea currently accounts for virtually all of the sea-level rise that is not attributable to ocean warming, and about 60% of the ice loss is from glaciers and ice caps rather than from the two ice sheets. The contribution of these smaller glaciers has accelerated over the past decade, in part due to marked thinning and retreat of marine-terminating glaciers associated with a dynamic instability that is generally not considered in mass-balance and climate modeling. This acceleration of glacier melt may cause 0.1 to 0.25 meter of additional sea-level rise by 2100. (link to full article)

As blogged on their website:

The team summarized satellite, aircraft and ground-based data from glaciers, ice caps, the Greenland ice sheet, the West Antarctic ice sheet and the East Antarctic ice sheet to calculate present and future rates of ice loss. They concluded that glaciers and ice caps are currently contributing about 60 percent of the ice delivered to the world’s oceans and the rate has been markedly accelerating in the past decade. The contribution is presently about 100 cubic miles of ice annually — a volume nearly equal to the water in Lake Erie — and is rising by about three cubic miles per year. The accelerating contribution of glaciers and ice caps is due in part to increased meltwater at the ice surface. Some glaciers are also experiencing increased meltwater at the base of the ice, which can lead to faster sliding of the glaciers against their beds.

This is especially the case for tidewater glaciers that discharge icebergs directly into the ocean, and their analogs, the outlet glaciers from the great ice sheets. Many tidewater glaciers are undergoing rapid thinning, stretching and retreat, which in turn causes them to speed up and deliver increased amounts of ice into the world’s oceans.

On the Decline of Coral Reef Ecosystems

This has already been posted in the blogosphere recently, so I will put it out here for comment:

The supposedly already-degraded state of coral reef ecosystems is sometimes claimed to be a reason why anthropogenic global warming will have a major impact on the reefs, i.e. they are already close to extinction and can easily be tipped over the edge.

A recent paper** by Peter Ridd challenges the methodology used to conclude that the outer and inner Great Barrier Reef (GBR) are already 28% and 36% respectively, down the path towards ecological extinction.

**A CRITIQUE OF A METHOD TO DETERMINE LONG-TERM DECLINE OF CORAL REEF ECOSYSTEMS
by Peter V. Ridd. Reprinted from ENERGY & ENVIRONMENT, VOLUME 18 No. 6 2007

The full article is archived here.

Nature Reports Climate Change

Getting accurate information on the effects of climate change and updates of the science is often tricky, particularly with the campaign for disinformation from the right wing think tanks. Nature magazine, which is in the top two scientific journals in the world, has put together a website which provides a digest of a topical issues associated with climate change. I found this very useful in catching up on some of the complex issues – particularly their new blog “Climate Feedback” which is doing a great job in dissecting climate change science and the wider implications of global warming.

“Climate tipping points loom large”

My friend and colleague, Professor David Stout, pointed me in the direction of this special report in new scientist (16 August 2007). The article highlights the uncertainties that are involved in some of the non-linear changes in climate and points out that the more we know, the less certain we’re about the directions or the rate at which some of these potentially catastrophic changes in climate may occur.

Climate tipping points loom large – Fred Pearce

SOME climate tipping points may already have been passed, and others may be closer than we thought, it emerged this week. Runaway loss of Arctic sea ice may now be inevitable. Even more worrying, and very likely, is the collapse of the giant Greenland ice sheet. So said Tim Lenton of the University of East Anglia, UK, speaking on Monday at a meeting on complexity in nature, organised by the British Antarctic Survey in Cambridge.

Lenton warned the meeting that global warming might trigger tipping points that could cause runaway warming or catastrophic sea-level rise. The risks are far greater than suggested in the current IPCC report, he says.

Yet climate modellers are in a quandary. As models get better and forecasts more alarming, their confidence in the detail of their predictions is evaporating.

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Temporarily offline

Apologies for Climate Shifts being off the air since the weekend – a few minor modifications caused quite a few major problems somewhere behind the scenes and caused the site to go down albeit temporarily. I now have a team of people helping me behind the scenes with the technical side Climate Shifts in light of mishaps like these. I am assured everything is back up and running in good working order! Meanwhile expect to see some changes to Climate Shifts over the coming weeks – please feel free to send your suggestions and comments to climateshifts@gmail.com or reply in the comments section below.

11th International Coral Reef Symposium

Every four years the International Coral Reef Symposium convenes as a major scientific conference of the International Society for Reef Studies to provide the latest knowledge about coral reefs worldwide. The theme for the 11th ICRS is REEFS FOR THE FUTURE. Goals are:
• provide a scientific basis for coral reef ecosystem management
• improve the understanding of reef condition, function, and productivity; and
• grow coral reef science, conservation, and research by facilitating exchange of ideas.

The 11th International Coral Reef Symposium will be held in Ft. Lauderdale, FL, USA, July 7-11, 2008. Over 2,000 attendees are expected from the international marine science, management, and conservationist communities, making this the largest ICRS ever. Twenty-five Mini-Symposia will provide a wide diversity of coral reef science and management participation opportunities. The South Florida venue has convenient access to visit and study reef systems in the Atlantic, Caribbean Sea, Gulf of Mexico, and Meso-America.

Symposium Co-Hosts include the State of Florida and the US Coral Reef Task Force (chaired by NOAA & DOI). The meeting is organized by a Local Organizing Committee. The 11th ICRS is a keystone event within the International Year of the Reef (IYOR) 2008.

Online Symposium and field trip registration, abstract submission, and hotel reservations are now open. Please visit www.nova.edu/ncri/11icrs/ for information and registration.

Opposing viewpoints: Freeman Dyson & Alun Anderson

Freeman Dyson: My first heresy says that all the fuss about global warming is grossly exaggerated. Here I am opposing the holy brotherhood of climate model experts and the crowd of deluded citizens who believe the numbers predicted by the computer models. Of course, they say, I have no degree in meteorology and I am therefore not qualified to speak. But I have studied the climate models and I know what they can do. The models solve the equations of fluid dynamics, and they do a very good job of describing the fluid motions of the atmosphere and the oceans. They do a very poor job of describing the clouds, the dust, the chemistry and the biology of fields and farms and forests. They do not begin to describe the real world that we live in. The real world is muddy and messy and full of things that we do not yet understand. It is much easier for a scientist to sit in an air-conditioned building and run computer models, than to put on winter clothes and measure what is really happening outside in the swamps and the clouds. That is why the climate model experts end up believing their own models. (Read more)


Alun Anderson: Knowing that Arctic climate models are imperfect, it would be reassuring for me, if not for the scientists, to be able to write that scientists keep making grim predictions that just that don’t come true. If that were so, we could follow Dyson’s line that the models aren’t so good and "the fuss is exaggerated". Scarily, the truth is the other way around. The ice is melting faster than the grimmest of the scientist’s predictions, and the predictions keep getting grimmer. Now we are talking about an Arctic free of ice in summer by 2040. That’s a lot of melting given that, in the long, dark winter the ice covers an area greater than that of the entire United States. (Read More)