Monday, January 12, 2009

Significant Sorcerers, But Still Apprentices: How Nature Can Dispel Our Ocean Dead Zones

In pursuit of covering significant science stories I was going to write something about the perennial problem of excess nitrogen on the land, which I shall mention briefly, but the story led me to a reminder of a deeper principle, that should encourage us to analyse as much as possible before taking actions at scale.

Some scientists have been conducting a research program for more than decade to see whether nitrogen fertiliser might be useful in the struggle against climate change by aiding carbon sequestration in forests. It's in an interesting and potential important story, but the scientists caution that the systems they are dealing with are very complex, and that they couldn't be sure that their experiment would be net positive in terms of atmospheric carbon reduction.

A wise caveat, since unintended consequences have been a rising and unfortunate fact for us and our world ever since we started trying to control our environment and food supply, which appears to be at least sixty thousand years ago. However, sometimes what we might view as a negative event in nature has a useful unintended consequence, which is something that our scientific and policy analysis should also be watching for.

One of the problems of using a lot of nitrogen to fertilise anything, be it for forests in the research mentioned above, or for crops for humans, is that much of the nitrogen won't stay on the land, but runs off into the water system. As far as I know, absolutely nobody wants this to happen, certainly not the farmers, who have to pay a lot of money for something which mostly ends up in coastal oceans or inland seas. Whereupon, it often forms algal blooms which in turn take all the oxygen at the bottom of the water and thus kill off all the other life forms that live there, which then causes all the creatures which depend on them to die off. Technically this oxygen shortage is called hypoxia (a 'low oxygen event'), but in common parlance it's a dead zone.

Worldwide, these dead zones have increased from 49 in the 1960s to 405 now. Scientific American gives one graphic example of why dead zones are bad news:
A single low-oxygen event off the coasts of New York State and New Jersey in 1976 covering a mere 385 square miles (1,000 square kilometers) of seabed ended up costing commercial and recreational fisheries in the region more than $500 million. As it stands, roughly 83,000 tons (75,000 metric tons) of fish and other ocean life are lost to the Chesapeake Bay dead zone each year—enough to feed half the commercial crab catch for a year.
Various schemes are being put forward to reduce the amount of nitrogen being applied to the land (though the forest experiment I mentioned first would ironically add to the problem), but the article continues:
[efforts at nitrogen reduction] still might not solve the dead zone problem. So much nitrogen is now reaching...coastal waters that much of it ends up buried in sediment [and] even when new nitrogen sources are removed those sediments release that nitrogen over time, perpetuating the cycle.

That inability to recover is driven not only by the nitrogen buried in the sediment but also by water layers that don't mix with one another, despite the massive flow of rivers like the Mississippi. Instead, warmer, fresher water on the surface sits on top of cooler, denser, saltier water...

So what does it take to make that mixing take place? takes the energy of multiple powerful hurricanes to blend the two.

And there's the paradox and complexity. Very few humans want hurricanes, but it seems that because hurricanes exist, time and co-evolving ecosystems have found a way of using this natural force:

For example, as Hurricane Katrina bore down on the Louisiana coast with its powerful winds blowing faster than 130 miles (210 kilometers) per hour, the monstrous tropical storm delivered a benefit: it mixed the warm, oxygen-rich surface waters with the colder, almost oxygen-free waters beneath, dispelling the largest dead zone in the U.S. for a time. Hurricane Rita followed and finished the work, ending early the seasonal dead zone that forms each year at the mouth of the Mississippi [at the top of the Gulf of Mexico].

That dead zone—which last year stretched over roughly 8,500 square miles or 22,000 square kilometres, an area the size of New Jersey, and is predicted to grow even more extensive in 2008, thanks to the early summer floods—forms because of the rich load of nitrogen and phosphorus the Mississippi carries down from the farm fields of the U.S. Midwest.

The dead zone in question is more than twenty times bigger than the 1976 event which cost half a billion dollars. The Scientific American article was written before the busy 2008 hurricane season really got blowing, so maybe the dead zone was dispelled early again in 2008.

The main point is that despite the extraordinary advances we have made in scientific understanding we keep finding out that everything in nature is more complex than we thought - it's like an endless Russian doll. That doesn't mean we should not keep trying to understand more, far from it, but rather that we should try to remember that large natural events that we find very negative will very likely have positive features seen from a larger systems perspective and that when we start interfering with those systems at scale, we are bound to be interfering with many dynamic systems we don't understand very well.

Thus, even at this late stage, beset with ever more urgent problems - a bit like the Sorcerer's Apprentice - we need to mix caution with innovation. That is not an easy task, though in a sense, all living things in every ecosystem are doing this, albeit unconsciously. We have the advantage and disadvantage of being able to analyse and plan. What we almost certainly don't have is a master magician waiting to bail us out, as it were, so the more we can find out about how things work and work with nature rather than against it the better.

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