Friday, May 04, 2012

Destroying the world's most successful killing machine

Humans killed by sharks annually: 5.

Sharks killed by humans annually: 100,000,000.

Source, based on this study and others (see comments for more).

This discrepancy points to a common feature of our predicament, the often vast gulf between our usual assumptions (sharks are a dangerous animal) and our rapidly changing situation (during my lifetime, literally billions of sharks have been killed and their populations have fallen off a cliff, declining by somewhere in the region of 90%). The fact that sharks are survivors from the Silurian period (making them roughly twice as old as the oldest dinosaurs! And there is some evidence that they may be even been around during the Ordovician) and yet our actions are having such drastic effects during the blink of a geological eye highlights just how powerful we (collectively) are. We have truly become a force of nature. I get the impression that few people have really grasped emotionally how shocking and radically novel this new situation is.

There seems to me to be a misunderstand claiming a particularly Christian character holding back such understanding, namely, the idea that it is somehow arrogant to think that puny little humans can have such large, planet-wide effects. Yet true humility is really an extension of the virtue of honesty. There is no virtue in pretending to be something other than we are. Romans 12.3 says "Do not think of yourself more highly than you ought" but does not go on to say "but think of yourselves as lowly worms, capable of nothing and worth even less". Instead, the second half of the verse is "but rather think of yourself with sober judgment". Sober judgement is what is needed. We have all kinds of reasons to be humble - from dust we came and to dust we return - yet let us acknowledge that various historically novel quantitative developments over the last few decades have brought us into a qualitatively new relationship to the rest of the natural world. To do so is not arrogance, but sober judgement. And when we notice that this relationship is increasingly one of destruction, then the potential for arrogant boasting of our powers is quickly chastised.

The title of world champion apex predator, held for over 400 million years by sharks, is now ceded to homo sapiens sapiens, who will be doing well if we can make it through the next 400 years without being the cause of another mass extinction.

Shark Extinction The Shocking Truth
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byron smith said...

Having had the numbers behind this infographic questioned on Facebook, I'm posting my response that did a little article searching.

After a quick search, here is the best reference I've found, a 2006 study estimating global trade in shark fins and shark meat.

"Estimates of the total number of sharks traded annually worldwide, based on all fin positions combined, ranged from 26 to 73 million/year (95% PI), with an overall median of 38 million/year."

They the note: "In addition, our trade-based biomass calculations may underestimate global shark catches. For example, due to the lack of data on domestic production and consumption of shark fins by major Asian fishing entities such as in Taiwan and Japan, unless exported for processing and then re-imported, these fins are not accounted for within our methodology (Clarke 2004b). Furthermore, shark mortality which does not produce shark fins for market, e.g. fishing mortality where the entire carcass is discarded, is also not included. These discrepancies suggest that world shark catches are considerably higher than reported, and thus shark stocks are facing much heavier fishing pressures than previously indicated."

This study estimates that bycatch comprises 40.6% of global marine catches. Obviously, this is not all shark, but even if only a tiny fraction is shark, then we're still talking many millions more added to the numbers. I'm also not sure of the scale of domestic shark trade in "major Asian fishing entities", but don't expect it to be small, since these locations are the primary drivers of the trade so their local production is very likely to be extensive. I don't know how they get from 38 million up to 100 million, but it is clear from this study that the numbers are likely significantly north of 38 million/yr. Furthermore, it is not necessary to assume that 100 million/yr have been killed every year for the last 20.

Furthermore, I think the 90% reduction figure is based on this 2003 study, which I'm aware has been contested, but still seems to be quoted frequently, indicating that perhaps the criticisms have not yet won the day or enabled an improved estimate to be reached. In any case, even if the decline is only 80% or 70%, this still represents a truly staggering human intervention into the functioning of one of the most resilient animals to have ever evolved.

A couple of other studies of some relevance.

Mike W said...

We may only be dust, but you can smother anything with a big enough pile of dust

byron smith said...

Mongabay: 79 possible new species of sharks and rays, many likely endangered.

byron smith said...

This is precisely the overblown reaction likely when we lose all perspective on an issue.

byron smith said...

The Conversation: Australia not doing enough to prevent shark finning

byron smith said...

Guardian: Global conservation plan talks - taking steps towards banning finning.

byron smith said...

Guardian: Shark fin fishing in Mozambique.

byron smith said...

Guardian: Updated numbers.

New study says between 63 million sharks and 273 million a year, with a best guess of 97 million. This represents between 6.4% and 7.9% of all sharks being killed every year.

byron smith said...

Guardian: Sharks: Feared or revered - but very rarely understood.

byron smith said...

Infographic on risk assessment: Shark deaths vs other forms of death.

byron smith said...

The Conversation: Shark fin soup drops off the menu. Consumption in China down by as much as 70%.

byron smith said...

Guardian: Shark finning in decline. Maybe.

byron smith said...

YT: A snarky video about the WA shark cull.

See also discussion and links on FB in Jan 2014.

byron smith said...

Motherboard: One company (UPS) has a big impact on shark finning.

byron smith said...

ScienceDirect: 2014 study finds 97m sharks killed annually (with a uncertainty range of 63m-273m).