How can someone who is not a climate scientist keep track of all that's going on in the current climate upheaval? It's an interesting question. Even more so when you are confronted with that climate scientists can't.
I had bought yet another book on the topic. Just working in science makes you a bit over-focused, and it can be good to read books that re-broaden your view. This one dealt with anthropogenic influence on the sea. The climate debate tends to focus on land and atmosphere, as land is where we live and the atmosphere is where we put our exhaust gases. But the ocean is vast. The oceans are the origin of life. They are the lungs of the world; the Amazonian forest is overrated! And if you kill off all life on land the oceans will still thrive, but if you do it the other way around that may not work. 90% of life seems to live in the sea to start with. And this book dealt with everything we are doing to it. Changing its temperature. Creating acidification. Overfishing. And oxygen depletion.
I have been long aware of oxygen minimum zones in the ocean. Where you have high productivity all the little critters use up all the oxygen there is. I did my PhD on the Arabian Sea, and that's one of the most productive areas there are. And I was aware of anoxia in places like the Black Sea (what's in a name) and the Baltic Sea. And where there is no oxygen hardly anything can live. But I hadn't realised yet that nowadays, there's lots of near-coast anoxia, all of it man-made. Actually, the Baltic Sea wasn't anoxic before humans started messing with it. And the deep oceans are losing oxygen too. And if I don't know it, there may be plenty of people who don't know it.
Dead zones in the media: mass fish mortality on a scuba diving website
I was still shaking with this knowledge when a talk at PML was announced, on exactly this topic. So I went! It was an eminent scholar from the USA: Peter Bremner, from MBARI in California, and he gave a state of the art update. I was pleased to see I'm still there where it happens.
Hundreds of nearshore zones of no oxygen, also known as "dead zones", have already been identified, and all of them have been linked to human influence; mainly land fertilising. Most of them came into being in the last 60 years. The fertilisers don't stay where they're spread, and flush into the sea, where they boost primary productivity, and thus decay of organic matter, and thus the use of oxygen. Generally these dead zones wax and wane with the seasons. And as dead zones are not exactly good for economically interesting activities such as fisheries, people tend to care, and in many areas legislation has been developed to limit the damage. In some cases with success, but unfortunately the rate at which new dead zones pop up is higher than the rate at which the law manages to get rid of them again.
All dead zones identified in 2008. Taken from: http://infranetlab.org/blog/2008/08/dead-zones/
An interesting thing is that it's not just oxygen concentration in water or air that allows creatures to breathe in it. It's the ratio between CO2 and O2. If it's 1 on 1 you die. If it's 1 to 10 you're not too happy. It seems that USA safety regulations allow humans to passively stay in an environment with such atmosphere for 1 hour. Not more. You will find life in water with such a ratio but it won't thrive. The speaker compared it to the top of the Everest: you may find humans there, but it doesn't mean they can comfortably live there. So the increasing amounts of CO2 we're pumping into the atmosphere are not helping.
Unfortunately, the best remedy against dead zones is churning it all up. Mix these waters! But climate is warming, so the surface waters are warmer too, and there's an increase in meltwater into the sea, so the upper layer of the sea now tends to be less dense than it used to be. So that layer is sitting there, and is not inclined to let the deeper, denser deep water come up. And that means the deep oceans also have problems. They loose their circulation too, getting anoxic too... nasty how all these things work together.
What it can look like... picture from the Baltic Sea, taken from wikipedia
A scary thing about this process is that it reminds one of something. Most people have heard of the mass extiction 65 million years ago, at the end of the Cretaceous, when the dinosaurs perished. There were more of those. It's only one of the "big five" of mas extinctions in the Earth's history. The real big one was about 250 million years ago, at the end of the Permian. At the end of the Cretaceous about 50% of all life died, when for the end of the Permian the estimate is about 95%... and what happened that was so bad? It's not that easy to unravel such things in detail that long afterwards, but one thing is clear: the global ocean turned anoxic...
And again I was at the right place: I popped by at one of our geologists, who is one of the big authorities on this extinction... he was willing to dig out an image of the sediments from that time. He hasn't yet, but I have good hopes I can add it soon!
I have to be careful with my words now. Climate sceptics would like to hear me say we're definitely heading for number six of the big five mass extinctions and call me an alarmist, and as nobody can look into the future such claims would be easily rebutted. But mass extinctions are not instantaneous events. It's not the stereotypical explosion after which all is dead. They take time, while species after species is lost from the Earth. And it's no secret that we are already eradicating unimagineable numbers of species. Perhaps already at the rate of that of a typical mass extinction. If we don't do something about what we're doing to the oceans I must say at least I am personally convinced we have a real fair chance at creating number six. An impressive feat, for only one species! But not really something to be proud of...
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