Shark week and some numbers

The Discovery Channel’s annual Shark Week, a week of television programs devoted to these toothy ocean residents, began yesterday.  Shark Week has introduced many people to the wonder of these unique predators, the likes of which help to keep ocean ecosystems balanced, and usually includes bits on shark conservation and other scientific content.  If you head over to their website there’s a nifty interactive map where you can click on different regions and learn about what species of sharks frequent those areas and even what their conservation statuses are.  There’s also a shark facts page with shark conservation information and states that you are more likely to get bitten by another person than a shark.

However, in regards to the high-profile television programs themselves, many of the titles  evoke images of attacks, such as ‘Rogue Sharks’ and ‘Killer Sharks.’

Over the years, the media in general has not been kind to these animals, giving disproportionate attention to, as John Bruno over at SeaMonster puts it, “sharks behaving badly, i.e. eating stuff.”  However, the reality is that tens of millions of sharks are being killed every year, and the populations of these ecologically important creatures are declining globally.

Six fatal shark attacks were reported last year globally, according to the International Shark Attack File.  73 non-fatal attacks were also recorded.  Loss of life is tragic, and I am certainly not attempting to play down any individuals’ experiences who were harmed by sharks, but these sorts of numbers do not justify an all-out fear of these animals.  For example, in 2008 (the latest year data seems to be available), 39,000 people in the United States were killed in car accidents, and most of us view traveling by car as a reasonable risk.  For some other comparisons, you can see the Florida Museum of Natural History’s ‘Relative Risk’ page.

I’m not trying to pick on Discovery, which over the years, has gotten many people more interested in science.  Nor am I implying that you should rub seal innards on yourself and try to give one of these big fish a peck on the cheek.  But sharks need our help—that is, we need to stop decimating them.  And that does include considering the economics and motivations of the fin trade and presenting people with an alternative.

Be sure to check out SeaMonster, Deep Sea News, and Southern Fried Science for more on Sharks and Shark Week.

Image 1:  Caribean reef shark, Alfonso Gonzàlez on Flickr (CC). Image 2: Windell Oskay on Flickr (CC).  

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Dr Jason Hall-Spencer at the Guardian

Dr Jason Hall-Spencer has written an excellent essay on the urgency of oceanic action, fueled by the recent findings of the International Programme on the State of the Ocean (IPSO).  Make sure to check it out.

The crux of the problem is that the rate of changes in ocean systems is accelerating and outstripping what was expected just a few years ago. Destructive fishing practices, pollution, biodiversity loss, spreading low-oxygen “dead zones” and ocean acidification are having synergistic effects across the board – from coastal areas to the open ocean, from the tropics to the poles.

via A steward for our oceans | Jason Hall-Spencer | Comment is free | The Guardian.

See also:  The State of the Ocean’s site and the original full report (PDF) Dr Hall-Spencer refers to.

Is the Earth’s sixth mass extinction looming near and large?

Fossil fish sculpture. Rae Allen. CC BY 2.0.
Ideally, your expenses are offset by your paycheck, so as you spend money for say, rent and food, you have cash coming in.  On the surface at least, this is similar to the dovetailing of extinction and speciation.  The vast majority (~99%) of all the species ever to have existed on Earth are extinct, never to be seen alive again.  However, this process is balanced by new species evolving, a process known as speciation.  So what happens when species extinctions far outpace species creation?  Mass extinctions, timeframes during which 75% of species are lost in a relatively short period (usually less than two million years and sometimes significantly less), have occurred five times (the Big Five) in the past 540 million years.  They are unique, singular events that stand out above the background level of extinction that is constantly ongoing.  However, more and more modern extinctions are being observed, amidst the myriad of human-derived disturbances, such as rapid climate change, invasive species introductions, habitat fragmentation, directly killing species, among others.

It is not a straightforward task to ascertain whether or not we are on track to another mass extinction—data from the fossil record must be comparable to historic and modern species assessments.  In a paper recently published in Nature, Dr Anthony Barnosky and colleagues point out why data comparisons of this type are difficult and proceed to broadly get around them by looking at the global picture.

The fossil record is not evenly distributed across taxa or geographies.  Fossils are particularly meager in some broad swathes of Earth, such as the tropics.  On the other hand, distributions are known for many modern species.  In terms of taxa, or groups of species, usually only animals with hard bits fossilize well.  Studying modern species is easier, because they’re still around, but less than 2.7% of known species have been assessed for risks (e.g. endangered, extinct in the wild, etc.) by the International Union for the Conservation of Nature (IUCN).  There’s also trouble with the species concept.  Fossils are usually identified at the genus, rather than species, level; modern work frequently uses genetic approaches to identify individuals to species.  Fossils are also not distributed evenly through time.  Fossil extinctions are recorded when a certain group of animals vanishes from the fossil record, the extinctions known are likely underestimates since most species have no fossil record.

In spite of these caveats, the researchers evaluated the existing data and show that it is possible to circumvent these various data comparison issues by taking a ‘big-picture’ global approach.  Conservatively, mass extinctions occur when the extinction to speciation ratio becomes so unbalanced that three quarters of species disappear, usually within less than two million years.  If two million years sounds like a leisurely long time, bear in mind that the Earth is ~4.54 billion years old. Most living things forever blinking of out existence in roughly 0.04% of that time is a colossally unique situation indeed.

Using a rate-based method, the researchers compared extinctions per million species-years (E/MSY)1 from throughout the fossil record and modern time.  By using various paleontology databases and accounting for data biases, they were able to establish a background rate of extinction.  Through this approach, it is clear that the maximum extinction rates since about 1,000 years ago are much higher than the average fossil rate and the recent average extinction rates are also significantly higher when compared to pre-anthropogenic (that’s pre-us, mind you) averages.

Another way to consider this is by splitting up the fossil record into 500-year intervals and calculating the likelihood that extinction rates were as high in many of these 500-year intervals as they were in the most recent 500 years. In the case of mammals, which have an average of 1.8 extinctions per million species-years, only 6.3% of these 500-year segments could have extinction rates comparable to the current 500-year interval in order to preserve the background E/MSY.  So no, it is supremely unlikely that many of these past 500-year bins had extinction rates that were as high as they are today.

But would these current rates produce a large magnitude extinction event?  By using modern species assessments of very well-surveyed groups coupled with fossil data, Dr Barnoksy and his team calculate that extinction rates for mammals, birds, amphibians, and reptiles are as quick or quicker than all rates that would have been responsible for the previous five mass extinctions.  If all threatened species (defined by IUCN criteria) are lost within a century, and the current extinction rate continue, land-based amphibians, birds, and mammals would reach mass extinction thresholds in ~240 -540 years.  This slows down a bit if ‘only’ critically endangered species disappear within the next 100 years to ~890 – 2,265 years for those same groups of animals. Current extinction rates are higher or as high as those that preceded and caused the previous mass extinctions.  The researchers point out that while a pressing need for new research exists, the 75% species loss threshold could occur within the next three centuries.

Modern species losses are serious but does not pass the threshold for a mass extinction event yet.  Relatively small numbers of species surveyed historically have been lost, although scores of species have yet to be discovered and/or evaluated.  However, the researchers point out that losing critically endangered species would put us on the fast track to mass extinction, and losing endangered and vulnerable species would achieve the sixth extinction even faster, within a few hundred years. Sobering commonalities between the present-day and the past mass extinctions exist:

It may be of particular concern that this extinction trajectory would play out under conditions that resemble the ‘perfect storm’ that coincided with past mass extinctions: multiple, atypical high-intensity ecological stressors, including rapid, unusual climate change and highly elevated atmospheric CO2. [Barnosky et al.]

The diversity of life should be preserved while it’s still here.

 

1  Think of this as man-hours (or really person-hours).  On a purely mathematical basis, if you had one million species and an extinction rate of 1 per million species-years, one species would go extinct a year.

Barnosky AD, Matzke N, Tomiya S, Wogan GO, Swartz B, Quental TB, Marshall C, McGuire JL, Lindsey EL, Maguire KC, Mersey B, & Ferrer EA (2011). Has the Earth’s sixth mass extinction already arrived? Nature, 471 (7336), 51-7 PMID: 21368823

Image:  Rae Allen on Flickr (cc).

This article is also posted at The Urban Times.

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Marine debris

The 5th International Marine Debris Conference has been ongoing this week in Honolulu, Hawaii.  The above video from NOAA gives some insight as to what is meant by ‘marine debris’ and why it’s an issue.  While the video focuses on the larger pieces of debris, it’s important to remember that microplastic pollution, especially as they accumulate in oceanic gyres over time, is an another issue of enormous consequence to ocean creatures great and small.

You can follow the conference on the Twitter machine here and by keeping up with the hashtag #5imdc for the extra Twitter literate.  For more information, check out the Seaplex Science blog (more about the Seaplex expedition here) which debunks some misleading headlines about the North Pacific garbage patch.  Miriam Goldstein, a PhD student at the Scripps Institution of Oceanography, studies the impacts of plastics on marine invertebrates and frequently talks plastic over at Deep-Sea News, along with various sea shanties of course.

Find out about NOAA’s Marine Debris Program here.

Crushing predators reinvade the Antarctic benthos

In Gotham, Batman drives a batmobile that shoots fire out the back and has all sorts of mechanical wizardry so he can catch fiends in style.  Or something close to that, unless my childhood was dreadfully misinformed.  He isn’t supposed to turn up in a St. Patrick’s day parade in New Jersey, pedaling away on a two-wheeled crime-fighting vehicle adorned with no fewer than 13 (count them!) bat symbols.  I feel that witnessing that would be strange–similar to the feeling you get when you discover your keys in the refrigerator next to the milk.  Simply out of place.

Recently, Antarctica has its own version of things showing up in the wrong place.  King crabs, predators that the Antarctic underwater shelf has not seen in over 40 million years, appear to be making a rapid comeback.  The endemic (unique to a specific, defined locale) nature of Antarctic shelf organisms is the result of a massive climatic cooling event in the middle Eocene, approximately 41 million years ago (Ma)1.  From 41 to 33.5 Ma, coastal sea surface temperatures decreased as much as 10°C, even before the onset on glaciation; this led to the eventual extinction of shell-breaking (durophagus) predators, such as modern bony fish, decapod crustaceans, and most sharks and rays. These groups have not returned due to their lack of an ability to physiologically cope with magnesium, one of the major cations present in seawater, at low temperatures.  Under one degree C or so, these magnesium ions are lethal to these organisms1.  Due to the fact that in the Antarctic, shallower seawater is slightly colder than that of the deep, they are effectively shut out of the shallows.

Distribution of epifaunal suspension feeders before and after the Eocene cooling at 41 Ma. The graph on the left shows temperature data derived from oxygen isotope values in bivalve shells. The schematic on the right shows the relative abundance of fossil concentrations of brachiopods, stalked and unstalked crinoids, and ophiuroids. Aronson et al. 2009, PLoS ONE.

Paleontological findings on Seymour Island, near the Antarctic Peninsula, reveal that dense populations of ophiuroids (Ophiura hendleri) and crinoids (Metacrinus fossilis and Notocrinus rasmusseni) were present on the soft substrate after the 41 Ma cooling event, but not prior1.  Both ophiuroids and crinoids are vulnerable to durophagy, and thus reduced predation pressure is implied after the Eocene cooling event.  This is quite straightforward:  if the things that normally eat you are no longer there, the size of your population increases, and you can invite the folks down the way to come over and watch Buffy the Vampire Slayer and enjoy your mean gin and tonics with a decreased sense of doom2.

Even today, these and other suspension feeders are abundant across the Antarctic shelf3.  However, in the past 50 years, sea surface temperatures off the Antarctic Peninsula have risen 1°C4, and as a result, predatory crabs and duropaguous fish may be able to enter this isolated shelf environment.  Anomuran king crab populations have already been found in slightly warmer, deeper waters nearby5 and it was reported on Sunday by the Washington Post that a recent expedition observed hundreds, potentially primed for invasion into the shallows of the continental shelf.  Dr. Sven Thatje and colleagues are currently searching thousands of seafloor images for evidence that predation by these crabs is ongoing.

Current climatic warming is essentially opening a physiological door for these polar predators to reclaim their place in the Antarctic benthic community via range extensions and human-induced introductions5.  This reinvasion has the potential to drastically alter ecological relationships, perhaps even eliminate populations of dominant suspension feeders and homogenize the unique Antarctic nearshore benthos with higher latitude communities.

Images/figure:  1) Michael Bocchieri/Bocchieri Archive, from Flickr user Foto Bocch (cc).  I have been itching to find an excuse to use it since I saw it as NPR’s photo of the day. 2) From Aronson et al. 2009, PLoS ONE (cc).

1. Aronson RB, Moody RM, Ivany LC, Blake DB, Werner JE, & Glass A (2009). Climate change and trophic response of the Antarctic bottom fauna. PloS one, 4 (2) PMID: 19194490
2. I’m actually unaware of any invertebrates that enjoy Joss Whedon shows or G and T’s.  Pity for them.
3. GILI, J., ARNTZ, W., PALANQUES, A., OREJAS, C., CLARKE, A., DAYTON, P., ISLA, E., TEIXIDO, N., ROSSI, S., & LOPEZGONZALEZ, P. (2006). A unique assemblage of epibenthic sessile suspension feeders with archaic features in the high-Antarctic Deep Sea Research Part II: Topical Studies in Oceanography, 53 (8-10), 1029-1052 DOI: 10.1016/j.dsr2.2005.10.021
4. Clarke, A., Murphy, E., Meredith, M., King, J., Peck, L., Barnes, D., & Smith, R. (2007). Climate change and the marine ecosystem of the western Antarctic Peninsula Philosophical Transactions of the Royal Society B: Biological Sciences, 362 (1477), 149-166 DOI: 10.1098/rstb.2006.1958
5. Thatje, S., Anger, K., Calcagno, J., Lovrich, G., Pörtner, H., & Arntz, W. (2005). CHALLENGING THE COLD: CRABS RECONQUER THE ANTARCTIC Ecology, 86 (3), 619-625 DOI: 10.1890/04-0620

Frontiers: The deep sea and climate

When we think about climate change and the ocean, many minds turn immediately to images of shallow-water corals, bleached white from the lack of zooxanthellae (internal, photosynthetic symbionts), driven away by heat and other types of stress.  However, the consequences of an increased atmospheric CO2 reach much deeper into the ocean.  The global ocean has an average depth of 3800 meters and comprises 71% of the total area of Earth, making the deep-sea far and away the largest biome on this planet.  In terms of volume, the deep-sea pelagic—the water-column itself—contains over a billion cubic kilometers of seawater.  Less than 5% of the deep benthos (the seafloor) has been remotely sensed, and less than a hundredth of one percent has been observed directly, sampled, and studied.  Even so, species diversity in the deep-sea is among the highest known1.

As a society, we still collectively get excited about the discovery of new species. And we should—such discoveries are essential to science.  The public being interested in new species is also quite importance for the continued funding of exploratory research.  Since 1840, 28 new habitat or entire ecosystems have been discovered in the deep ocean.  Not simply new species, but entirely new environments. Cold seeps, hydrothermal vents, brine pools, xenophyophore fields, just to name a few—these are all habitats that have only been known since the 1970s1.

Year of discovery of new habitat/ecosystem in the deep sea since 1840 (Ramirez-Llodra at al. 2010)

However, the lack of taxonomists to classify and describe the new species in these novel habitats dampens the spirit of discovery somewhat—specimens languishing in collections, as of yet unidentified due to the lack of support for specialists, harkening back to the last, frustrating scene in Raiders of the Lost Ark.

Atmospheric carbon dioxide concentrations are predicted to exceed 500 ppmv before 21002,a value not seen in the past few million years3.  This is contributing towards both warming and ocean acidification4,5.  It is uncertain how benthic organisms and their associated ecosystems as a whole will react; particularly little is known regarding the effects of climate change in the deep-sea. Continue reading

Sea debris: shipping containers and marine life

Approximately 10,000 shipping containers tumble off into the sea every year, bobbing around for a bit before, in most cases, sinking into the deep ocean.  To discover what happens to these containers after reaching the seafloor and what potential effects these abrupt structures may have on marine communities, the Monterey Bay Research Institute is teaming up with the Monterey Bay National Marine Sanctuary to investigate the biological community found on a shipping container offshore of California.  The benthos in much of the deep-sea, including the vast abyssal plains, is primarily composed of sediment.  These containers could suddenly provide hard substrate in an environment that usually lacks it, altering the habitat’s physical characteristics and possibly changing the suite or abundance of species present.  Researchers will be using a remotely-operated vehicle to compare sites at different distances from the shipping container, which is under about 1,300 meters of seawater.

Fittingly, the funding for these research cruises came from a settlement between  the National Oceanic and Atmospheric Administration and the shipping company whose vessel lost this specific container and 14 others in 2004.  The discovery of this container (chock-full of 1,159 steel-belted tires) lends an important opportunity to study the impacts of this global issue.

Read the MBARI press release here (via Ed Yong on Twitter).

Image: runner310 on Flickr (cc)

Deepwater Horizon Revisited

A recent study found oil and soot blanketing multiple areas of the seafloor in the Gulf of Mexico,  seemingly inundating the microbes that usually consume oil and leaving behind dead benthic animals.

Above is an absorbing and important lecture by Dr. Peter Roopnarine from last year on the ecosystem impact of the Deepwater Horizon disaster.  Dr. Roopnarine does really interesting work on mollusks, extinction, and food webs.

[Video source:  California Academy of Sciencescc]

Mismanaged Fisheries: Don’t forget the invertebrates

When we think of fisheries, we usually think of, well, fish.  As the collective global negligence regarding fisheries is further studied and exposed, these resource management issues have been brought out of obscurity in the past decade or so.  Fisheries worldwide totaled 15-20 million metric tons (MMT) in the 1950s, rising to ~85 MMT by the 1990s.  However, this was a non-linear ascent.  Global catch increased from 6% per year in the 1950s and 1960s and declined to 2% through the 1980s, finally falling to zero in the 1990s—all the while with increasing fishing effort.  We are reaching (or have already reached) the maximum productivity potential for the global ocean.  Estimates have placed world overcapacity at around 30%:  a measure of how much more money has been invested in fishing capacity than can be returned due to the oversupply of vessels.  Ironically, this cycle of overinvestment and overfishing is not economically viable.  Humans are essentially fishing out the watery realms of Earth, fundamentally restructuring enormous ecosystems, and it’s not even cumulatively profitable.  The value of all of the fish caught worldwide is ~70 billion USD but conservatively, the global catch costs 91-116 billion USD to attain.  Although pointed out in the early 1990s, no real global action has been taken and mechanisms such as government subsidies are necessary to keep things afloat.   The northern Atlantic, once home to long-lived, piscivorous (eats fish) fishes is now dominated by shorter-lived, plankivorous species, reflecting the industry’s predilection for high trophic-level fishes.  Interesting, considering that 90% of energy is lost at each successive trophic level1.  Globally, the ocean has lost 90% of all large pelagic fishes according to a 2003 study2–a staggeringly downward trend that even some marine scientists have struggled to accept but has since been further confirmed in other works3.

In the face of such utter enormity of human-caused pressures within global fisheries, much less attention has been focused on invertebrates, particularly invertebrates collected for purposes other than food.  For example, there is much contemporary interest in developing pharmaceuticals from marine invertebrates.  This is not a new idea.  These organisms have been collected and used for medicinal purposes at least since the 5th century BCE, being especially widespread in the ancient Greek and Byzantine periods.  Inverts were used for digestive, skin, and other issues, and were described by the likes of Hippocrates and Aristotle4.  In an aesthetic rather than utilitarian vein, precious corals have been used for decorative uses for thousands of years5.  Even throughout the second half of the 20th century, precious corals were harvested sporadically offshore of Oahu, Hawaii, among other global locales particularly on other Pacific islands and in the Mediterranean Sea.  The fishery in Hawaii includes some of the oldest animals on Earth; specimens of gold (Gerardia sp.) and black coral (Leiopathes sp.) have been radiometrically dated to be over 2700 years and 4200 years old, respectively 6.

A recent study delved into the oft-overlooked ornamental invertebrate fishery in Florida7.  Many aquarium hobbyists are no longer simply displaying fish-only tanks, opting instead to recreate microcosms of reef ecosystems.  The live coral (and ‘live rock’) trade alone is worth 200-330 million USD annually.  Little attention has been given to the impact that this coral and invertebrate collection has on Caribbean reefs, which sadly are among the worst off.  By Florida law, all commercial marine fisheries collections are to be reported; these data are compiled by the Florida Fish and Wildlife Conservation Commission.  Andrew Rhyne and colleagues used records from 1994-2007 to access the scale and general nature of this multi-species ornamental fishery.

Total landings were found to have increased drastically in this 13-year period, increasing by over half a million individuals each year.  Collectors do not target various invertebrate taxa uniformly:  in 2007, the top 15 species collected represented 92% of all landings; in 1994, the top 15 represented 88%.  The composition of these catches has shifted markedly due to the shift from purely ornamental specimens to species that can provide biological controls in reef tanks; however, fishing pressure on nearly every species has increased.  There’s also the question of removing individuals which perform an ecosystem function out of that environment.  6 million individuals were collected in 2007 that were considered grazers, which is more than double the landing reported for curio and ornamental purposes combined (figure below).  Grazers are popular because they control algal growth in tanks.  But they also provide this same ecosystem function in the ocean.  Less grazers means a less resilient reef and one that is increasingly likely to being overgrown by macroalgae.

Ecosystem processes and services in FLML invertebrates. Inlays show % of the total catch. From Rhyne et al. 2010.

Rhyne et al. propose that it may be most useful to manage this fishery by 1) species complexes, to avoid taxonomic ambiguities, and 2) considering single-species management strategies for the top 15 species collected and multi-species based strategies for the reminder.  Strangely, the gloomy economic climate seems to provide an apt time to implement new regulations.  The researchers note that

“Given the stark outlook for the global economy at the present time, and given that marine home aquaria are ‘‘luxury’’ expenditures, growth in ornamental fisheries is expected to slow or decrease. While industry demand is slow, a limited window of opportunity is open where management policies can change without immediate disruption of economic livelihood.”

Considering diversity and landings, Florida’s ornamental fishery is ranked third worldwide, only behind Indonesia and the Philippines. To date, this fishery operates with a licensing scheme under which most fishing is not affected by any current regulations.  For example, not granting any new licenses and reducing current licenses has only removed small-scale or inactive organizations.  The fact that only a few licenses are responsible for most of the fishery compounds this problem.  Can a collapse be avoided?  Hope seems to exist but the ultimate outcome is uncertain.  Fishermen within the Florida Keys Marine Sanctuary are calling for stricter regulations and the implementation of monitoring programs.  This work highlights the need to consider ornamental fisheries in the conservation and management of our marine resources.
This post was chosen as an Editor's Selection for ResearchBlogging.org

1. Helfman GS (2007) Fish Conservation: A Guide to Understanding and Restoring Global Aquatic Biodiversity and Fishery Resources. Island Press. Note that this is a secondary source (textbook) that discusses a multitude of papers in the primary literature. Most of the background on global fisheries discussed here was found within this work.
2. Myers RA, & Worm B (2003). Rapid worldwide depletion of predatory fish communities. Nature, 423 (6937), 280-3 PMID: 12748640
3. Jackson, J. (2008). Colloquium Paper: Ecological extinction and evolution in the brave new ocean Proceedings of the National Academy of Sciences, 105 (Supplement 1), 11458-11465 DOI: 10.1073/pnas.0802812105
4. Voultsiadou E (2010). Therapeutic properties and uses of marine invertebrates in the ancient Greek world and early Byzantium. Journal of ethnopharmacology, 130 (2), 237-47 PMID: 20435126
5. R Grigg (1993). Precious Coral Fisheries of Hawaii and the U.S. Pacific Islands Marine Fisheries Review, 55 (2), 50-60
6. Roark EB, Guilderson TP, Dunbar RB, Fallon SJ, & Mucciarone DA (2009). Extreme longevity in proteinaceous deep-sea corals. Proceedings of the National Academy of Sciences of the United States of America, 106 (13), 5204-8 PMID: 19307564
7. Rhyne, A., Rotjan, R., Bruckner, A., & Tlusty, M. (2009). Crawling to Collapse: Ecologically Unsound Ornamental Invertebrate Fisheries PLoS ONE, 4 (12) DOI: 10.1371/journal.pone.0008413

Rogue hydrocarbons

It’s official: the Gulf of Mexico spill is the largest accidental oceanic spill (bigger than Ixtoc), with roughly 5 million barrels released.

And so static kill begins.

Something to think about (via a most excellent infographic site–information is beautiful):

I’ll let you work out which one’s the silly one.  The scale of the two non-silly ones is fairly tremendous, but interesting nevertheless.

Image licensed under CC 2.0, David McCandless 2009.  Original here.