White-tip reef shark, Fiji © 2011 Angelo Villagomez

Causal relationships can be fiendishly tricky. Spend an hour watching any of Star Trek Voyager’s time travel episodes and you begin to understand why the show’s writers often resort to lines such as, “It’s better if we don’t talk about this too much.” Consider another example of causality. I’m hammering-out this post at home with a real doozy of a head cold. My sinuses are completely congested. I can feel a chest full of gunk as I breathe. And my body generally feels achy and sore. Retracing my steps, I might place contraction from surface contact or airborne transmission at work where one of my officemates was complaining last week of “a cold.” Or it may have been aboard the overheated, moist Petri dish of my commuter ferry. Or maybe it was from the plates, silverware, water, or food from any of the restaurants I visited last week.

Not having the Center for Disease Control’s Epidemic Intelligence Service activated at every case of the common cold, I will likely never know the ultimate cause of my dreary, mucus-filled weekend. But I can connect enough dots, enough small actions, to construct a few compelling transmission scenarios that might hold water. The more dots I connect, however, the more provisional and potentially implausible my scenarios might become. Causally, they may seem tenable. But at some point, the casual relationships become so tenuously hair-thin that it simply strains credibility.

In his 1758 Poor Richard’s Almanac, Benjamin Franklin captured the causal notion that small actions can result in large consequences through the proverb, For want of a Nail the Shoe was lost; for want of a Shoe the Horse was lost; and for want of a Horse the Rider was lost, being overtaken and slain by the Enemy, all for want of Care about a Horse-shoe Nail. But Franklin’s verse was a further contraction of yet more causal links in an earlier version of the proverb,

For want of a nail the shoe was lost.
For want of a shoe the horse was lost.
For want of a horse the rider was lost.
For want of a rider the message was lost.
For want of a message the battle was lost.
For want of a battle the kingdom was lost.
And all for the want of a horseshoe nail.

As I’ve written about before, the practice of marine conservation is full of deciphering causal relationships and complex dependencies. When environmental problems strike, a natural response is to point to the cause. Sometimes that’s easy. A ship grounding scar on a coral reef is essentially the marine equivalent of a ballistics crime scene investigation. You trace a spent shell or gunshot damage back to a specific firearm, and then you search for gun owners with motive, means, and opportunity. But more often, like my head cold, it’s a very complex process to identify causal relationships. In marine ecosystems, it’s often incredibly complicated. In part because it’s an open system with many inputs. But it’s also because we still don’t fully understand how marine ecosystems operate.

So the challenge for constructing meaningful conservation interventions is to untie the often messy causal knots in order to get to the root of the problem. And recently, marine conservation knots don’t seem to get much messier than shark conservation.

Before we get into the messiness, let’s start with what we know:

• In general, sharks grow slowly, mature late and produce few young over long lifetimes, leaving them exceptionally vulnerable to overexploitation and slow to recover from depletion.
• The onset of industrial fishing over the past 60 years has drastically depleted global shark populations. Of the shark and ray species assessed by scientists for the International Union for Conservation of Nature (IUCN), 30 percent are threatened or near-threatened with extinction.
• Shark finning–the practice of catching a shark, slicing off its fins and then discarding the body at sea–takes a tremendous toll on shark populations. Finning primarily supports the global shark fin industry, valued for the Asian delicacy shark fin soup.

So far, not much handwringing needed to provide answers. Where we start to get into the weeds however is when we ask a basic question such as, “How many sharks are there in the oceans?” Washington Post journalist and author Juliet Eilperin did a good job of capturing this uncertainty in her recent book, Demon Fish: Travels Through the Hidden World of Sharks. Scientists at the IUCN gave her an estimate as high as five-billion individuals. When asking Dalhousie University fisheries biologist Boris Worm, who spends his time trying to quantify how many fish are actually still swimming in the oceans, she got a more nuanced (but still vague) answer,

“There are nearly seven billion people on earth right now, right? There are five-hundred species of sharks, so in order to have more sharks than people, you’d have to have ten to twenty million per population. That seems like a lot. My guess would be there are more people than sharks in the world, but it’s hard to say because there are some shark populations we don’t know anything about, like deepwater sharks.”

Eilperin’s conclusion? There is no precise way at this moment to calculate whether shark populations outnumber human populations, or vice versa. It will take research for years to come.

More important to shark conservationists at the moment is the question of how many sharks are killed annually for the global fin trade. As with estimating global shark populations, estimating annual kill rates is also nebulous. Some online shark conservation petitions have claimed harvest rates at 100 million to over 200 million (all using somewhat fuzzy math). The Pew Global Shark Conservation group uses the statistic that “up to 73 million sharks are killed every year…” based on Shelley Clarke’s estimate of 26 to 73 million sharks killed each year. Admittedly, that’s quite a range! But even if we assume the annual harvest was at the low end (23 million sharks killed annually) or the median (38 million sharks killed annually), that’s a tremendously high harvest rate for an already depleted species that matures late and produce few young over long lifetimes.

I won’t spend more time rehashing what other writers have already done a great job in summarizing. The fact is we simply do not know exact numbers involved in the global shark trade. Absent that ability to know for certain, a precautionary approach of promoting shark protections wherever possible seems warranted. Besides, the intention of this piece is not to argue quantitative methods. It’s to discuss how the shark conservation community argues causal relationships from those numbers.

Currently, I’m engaged in three separate shark conservation efforts in my coral reef conservation work around the world. Why is a coral reef conservationist focusing on a single species? Good question (and one my board of directors has asked on numerous occasions). My rationale has been based on causal relationships that affect ecosystem health and national economics.

The ecological argument: Coral reef shark species are often apex or top predators, helping to regulate species abundance and diversity while maintaining balance throughout an ecosystem. Studies have shown that coral reef ecosystems with high numbers of apex predators tend to have greater biodiversity and higher densities of individual species.

The loss of apex predators in a reef ecosystem upsets the natural food web and changes the composition of the reef community, eventually leading to the decline of critical reef species like herbivorous fish. With fewer herbivores, algae can become overgrown, suffocating the reef and reducing the number of available niches for fish species.

The economic argument: In addition to being important for overall ecosystem health, sharks are also valuable to the tourism industry and to the economic health of coral reef tourism destinations. A recent report from the Australian Institute of Marine Science found that shark tourism accounts for approximately eight percent of the G.D.P of the island nation of Palau. The study showed that the roughly one hundred sharks inhabiting the most popular dive sites in the area were each worth $179,000 annually to the local tourism industry, giving each shark an approximate lifetime value of $1.9 million. A similar report is soon to be released for the Nation of Fiji.

Is it good strategy to hitch ecosystem conservation to a series of causal relationships (essentially “what if” statements) that boils down to the premise that removing sharks threatens the ecology and economies of coral reef nations? Time will tell. And critics of the shark/coral reef cascade-effect research, such as my colleague Pete Mumby, have not been shy to point out that many of the studies have significant limitations and there are far more substantial (and less spurious) rationales we could leverage to protect reefs than dealing the shark card.

But last week I came across what might be the ultimate spurious causal relationship claim for shark conservation. The Global Shark Conservation Initiative Facebook page linked to the article, Haaienvinnensoep drijft haaienpopulaties wereldwijd de soep in! (Shark fin soup driving shark populations worldwide in the soup!) by Katrien Vandevelde, director of a conservation organization called Sea First. I’ve had to rely on Google Translate for the Dutch to English translation of the original PDF article, so apologies in advance for any errors here.

In her first several paragraphs, Vandevelde runs through the usual shark basics… the long evolutionary lineage, humans aren’t very good shark food, how sharks might mistake humans as prey, slow growth and limited reproductive rate of sharks. Your basic “Sharks for Dummies” narrative. But then Vandevelde jumps the shark on this passage:

Het belang van haaien gaat echter nog verder dan dat. Tot 70% van de zuurstof die wij ademen wordt geproduceerd in de zee, door fytoplankton. Dit fytoplankton bestaat uit microscopische plantjes en algen en samen vormen ze de bouwstenen van het ecosysteem in de zee. De zee absorbeert ook tot 80% van de CO2 die wij uitstoten en fytoplankton zet een groot deel daarvan om in zuurstof. Zo zorgt de zee dat de opwarming van de aarde wordt getemperd en er voldoende zuurstof wordt geproduceerd. Maar een zware verstoring van het evenwicht, veroorzaakt door het wegvissen van de roofdieren in de bovenste lagen van de voedselketen, kan een exponentiële toename van kleine planktonetende visjes en diertjes tot gevolg hebben. In dat scenario is het realistisch dat onze zuurstofvoorraad in het gedrang kan komen. De zee kan de door ons uitgestoten CO2 dan ook niet meer bufferen waardoor de opwarming van de aarde en de verzuring van het zeewater door een teveel aan CO2 zich sterker zullen laten gelden.

[Imperfect translation]
The importance of sharks goes however still further then that. Up to 70% of oxygen which we breathe is produced in the sea, by phytoplankton. This phytoplankton exists in the from of microscopic plants and algae and together form the base of ecosystems in the sea. The sea also absorbs up to 80% of CO2 which we expel and the phytoplankton use to produce oxygen. This ensures that the sea is tempered and there is enough oxygen produced. But if a heavy disruption or imbalance removes carnivorous fish in the upper layers of the food chain, it is possible an exponential increase of small plankon-eating fishes and other animals to occur. In that scenario, our oxygen supply may be affected. The sea, the CO2 emitted by us is therefore not buffering so global warming and the acidification of sea water by excess CO2 will be more prominent.

Readers may recall that I’ve written before on the old “the ocean produces most of the Earth’s oxygen” trope, so I won’t spend any time on it here. But Ms Vandevelde is arguing for a causal chain that starts with sharks being depleted and ends with global warming and ocean acidification. Why not just throw the global stock market crash into the mix as well and we may really have a cascade trifecta that gets people to prick up their ears!

Consider the following: I am fat. Not just a little overweight, but fat. Probably obese by a physicians height/weight table. Now, I can start eating better, moving more, and developing some muscle at the gym. This might lead to fitting into more flattering clothes that accent my new bod. Fitting into more flattering clothes might encourage me to show off my new wardrobe and bod by sitting around in San Francisco café’s. Sitting around in San Francisco café’s looking chic and buff might attract the attention of Ricky Martin on his next swing through San Francisco. And capturing the eye of Ricky Martin might mean I could retire to Puerto Rico and not worry about coral reef and shark conservation for a while.

Or I could realize that as a fat, 48 year-old man in a fairly stressful job, I have heart disease, a few strokes, or diabetes to look forward to.

Which of the two makes a more plausible and compelling argument for losing weight?

Look, I’m not here to make another conservation professional’s life difficult.  We don’t get paid enough and we have true bad guys to fight on a daily basis.  I realize that the bad guys are not bound by any codes of ethics, honesty, or integrity in their tactics.  But if we are attempting to build long-term, environmentally-conscious constituents,  shouldn’t conservation seek a higher path?  I can only assume that Ms Vandevelde is sincere in her call for protections.  But if we are going to be taken seriously by policy shapers, the scientific community, our public, and each other, then our words and arguments matter.

Causal relationships can be fiendishly tricky. Spend an hour watching any of Star Trek Voyager’s time travel episodes and you begin to understand why the show’s writers often resort to lines such as, “It’s better if we don’t talk about this too much.” Consider another example of causality. I’m hammering-out this post at home ...