Under a green sky, details below
From Science Daily a report on the increasingly worrying state of the world’s oceans and the impact on sea life:
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, 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…
The paper in question is behind the pay wall, I’m reading it:
Extinctions in ancient and modern seas. Trends in Ecology & Evolution, 2012; Paul G. Harnik, Heike K. Lotze, Sean C. Anderson, Zoe V. Finkel, Seth Finnegan, David R. Lindberg, Lee Hsiang Liow, Rowan Lockwood, Craig R. McClain, Jenny L. McGuire, Aaron O’Dea, John M. Pandolfi, Carl Simpson, Derek P. Tittensor.
The abstract:
In the coming century, life in the ocean will be confronted with a suite of environmental conditions that have no analog in human history. Thus, there is an urgent need to determine which marine species will adapt and which will go extinct. Here, we review the growing literature on marine extinctions and extinction risk in the fossil, historical, and modern records to compare the patterns, drivers, and biological correlates of marine extinctions at different times in the past. Characterized by markedly different environmental states, some past periods share common features with predicted future scenarios. We highlight how the different records can be integrated to better understand and predict the impact of current and projected future environmental changes on extinction risk in the ocean.
For those more curious, I’d suggest the “Under a green sky: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future” by Peter Ward. It’s a good popular introduction to the topic.
It recounts how scientists came to understand major extinction events, and discusses the role of increased levels of Co2 and ocean acidification in past extinction events. In particular Ward discusses the Permian-Triassic Extinction Event (PET) that occurred around 250 million years ago, when over 90% of all life vanished.
The PET is also referred to as the “Great dying”.
Watching the Deniers 
What many people generally, and deniers specifically, don’t understand about ocean ecology is just how vulnerable some foodwebs are. When we were young and in school, “fooodchains” were first introduced to us with one of two models; a terrestrial one, usually ending up with an eagle or a large cat at the top, and an oceanic one starting with plankton and ending with a shark. Of course, foodwebs are much more complicated than that, but the ocean model is possibly the better because it pretty much holds true for every ocean and by far the most important players are the planktonic larvae, not only because they occupy the bottom layers of the web but also many of the middle layers. This spatio-temporal existence within foodwebs, makes them doubly important. The loss of these creatures will be a double whammy making ecosystem collapse more likely than not. Given that so many planktonic species rely on the production of calcium carbonate for their exoskeletons and shells, acidification is a very real danger and is in fact starting to be shown to be having an effect in some systems. It’s also not just the direct effect on the ecosystem in terms of trophic interactions but also on niche functioning. For example, If you take out the water filterers there are consequences or if you take out the necrotrophs, there are other consequences for ecosystem function each having a ripple effect. Many ecosystems are robust and will tolerate perterbations to an extent, but ocean ecosystems are potentially much more vulnerable.
Indeed, I’ve been following the research for some time now. Now try explaining the concept of ecosystem services to the average person (forget the deniers and sceptics they’ll think its part of a socialist plot) and how dependent our civilisation is on these.
Simply put: the ocean and its complex web of ecosystems has a level of resilience that will be pushed and tested until a point significant disruption. At that point we’ll go “off the map”, and what we know will be in flux. A new state will emerge, but that will take many millennia.
That is a timescale not merely longer than the average human lifespan, but a period of time longer than when our species first started farming and began its long march from hunter-gatherer to urban species. Weather has, and will continue to, dramatically shape the course of societal evolution.
I live on the Fraser coast, great sandy straits, often sit and watch the crabs amongst the mangroves, they collect the fallen leaves at low tide and take them down their holes, they make little beds, SLR will drive the mangroves further inland except up here there is nowhere for them to go, many of the mangroves are growing on islands only uncovered at the bottom of the tide, others are hard up against five and six metre high shorlines, sea level rise over hundreds of years or thousands of years would probably not inhibit their retreat, over decades, no chance, mangroves as we know are vital as ocean nurseries, every HAT we go down to see if the boat ramp carpark has been inundated, won’t be long. idiots want to build a marina there using existing car park.
[…] 2012/08/22: WtD: The dead seas: will global warming usher in another mass extinction of sea life? […]