The Coming Mass Extinction In The Oceans

I must have been having a particularly cynical day on August 24, 2012 when I wrote the original post. I wrote this when presidential election hysteria was reaching a crescendo. We all know how that turned out. So I cleaned this post up a bit, and added some detail from the scientific paper the post is based on — Dave

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Earlier this week a story surfaced about the threat of a future mass extinction in the oceans. A Google news search reveals that this story appeared at phys.org, scienceblog.com, sciencealert.com.au (Australia) and sciencedaily.com, and nowhere else, at least not here in the United States.

We see, then, that this story was confined to the science ghetto. It was not reported by the Associated Press, Reuters, CNN, ABC, MSNBC, or any of the rest. The story was based on a research paper called Extinctions In Ancient And Modern Seas (pdf) which recently appeared in the journal Trends In Ecology And Evolution.

I'll quote from the Science Daily story called World's Sea Life Is 'Facing Major Shock', Marine Scientists Warn.

Life in the world's oceans faces far greater change and risk of large-scale extinctions than at any previous time in human history, a team of the world's leading marine scientists has warned.

That's a stunning lead. You might think the world would pay attention to a story that starts off like that.

The researchers from Australia, the US, Canada, Germany, Panama, Norway and the UK have compared events which drove massive extinctions of sea life in the past with what is observed to be taking place in the seas and oceans globally today.

Three of the five largest extinctions of the past 500 million years were associated with global warming and acidification of the oceans — trends which also apply today, the scientists say in a new article in the journal Trends in Ecology and Evolution.

Other extinctions were driven by loss of oxygen from seawaters [anoxia], pollution, habitat loss and pressure from human hunting and fishing — or a combination of these factors.

"Currently, the Earth is again in a period of increased extinctions and extinction risks, this time mainly caused by human factors," the scientists stated. While the data is harder to collect at sea than on land, the evidence points strongly to similar pressures now being felt by sea life as for land animals and plants...

Marine extinction events vary greatly. In the 'Great Death' of the Permian 250 million years ago, for example, an estimated 95 per cent of marine species died out due to a combination of warming, acidification, loss of oxygen and habitat. Scientists have traced the tragedy in the chemistry of ocean sediments laid down at the time, and abrupt loss of many sea animals from the fossil record.

"We are seeing the signature of all those [Permian] drivers today — plus the added drivers of human overexploitation and pollution from chemicals, plastics and nutrients," Prof. Pandolfi says.

"The fossil record tells us that sea life is very resilient — that it recovers after one of these huge setbacks. But also that it can take millions of years to do so."

The researchers wrote the paper out of their concern that the oceans appear to be on the brink of another major extinction event.

"There may be still time to act," Prof. Pandolfi says. "If we understand what drives ocean extinction, we can also understand what we need to do to prevent or minimize it.

Here are two figures and some text from the paper, but this material may be hard to understand out of context. There is no substitute for reading it.

An increasing number of marine species are currently threatened by extinction [Figure 2c, Box 1, reproduced below]. At least 830 marine species have been classified as critically endangered, endangered, or vulnerable and at least 1538 as data deficient. Overall, the assessment of marine species lags behind that of terrestrial species: out of the 41,500 assessed species in 2007, only 1500 were marine, with another 1500 marine species added by 2008. This included complete assessments of sharks and rays, groupers, reef-building corals, seabirds, marine mammals, and sea turtles.

Since then, assessments for all mangroves, seagrasses, and tunas have been completed, and the International Union for the Conservation of Nature (IUCN) aims to have 20,000 marine species assessed by 2012. Nevertheless, assessments for many groups are incomplete or entirely lacking.

A comparison of Cenozoic extinction rates, historical rates, and currently endangered species. Click to enlarge.

The degree to which current extinction threats differ from past extinction drivers is an important question when considering the utility of fossil and historical records for understanding current and predicting future extinction risk. Even if the ultimate drivers of extinctions have changed over time, the proximal effects experienced by organisms might be similar. For example, ultimate sources of elevated atmospheric CO₂ differ between the late Permian (volcanic activity) and present day (burning of fossil fuels), but in both instances marine organisms have had to contend with the proximal effects of acidification and warming [Table 1, reproduced below].

Similarly, large changes in the area of shallow benthic habitat have occurred throughout geologic time (e.g., via sea-level fall due to the growth of continental ice sheets), which might bear similarities to human-driven habitat degradation and loss today. Below, we compare the similarity and relative importance of current threats and ancient drivers of marine extinction, and consider synergistic effects among multiple drivers.

Past drivers of marine extinctions and current threats. Click to enlarge

I used to worry about this stuff more than I do now. Years ago, I would have gotten all bent of shape about the fact that only a few people seem to care about the very real, looming possibility of a mass extinction in the oceans. I believe the probability of such an event occurring in the next 200 years is near unity (= 1). Trends in the oceans are well-established, and to the extent these trends are based on characteristic human behavior, there is little reason to believe the ongoing destruction of marine ecosystems will be reversed.

Nonetheless, given that grim prognostication, I do want our collective descendants to know there were a few people in 2012 who thought such probable catastrophes were worth noting and reporting on.

In the United States, the media are too preoccupied with Hopey-Changey versus The Mittster to notice that there is a coming mass extinction in the oceans. I want our descendants to know that, too. Few people will remember in 2070 who ran for president in 2012, but those hapless folks will remark frequently on the fact that humans are dying left and right because the oceans have turned to shit.

 

Comments

[Oliver]

Yes Dave - for my part, previous worry has mutated past angst into utter weariness with my fellow "man".

As if further proof was required for the impossibility of any change to "our" behavior, look at this abject failure dressed up as success in protecting the oceans:

http://www.bbc.co.uk/news/world-europe-21598367

Phased in ... certain exemptions ... later debate about how it will work ... what a load of bollocks, as they say in these parts.