The Mississippi dead zone will grow due to this year’s floods

Low oxygen anoxic zones due to excess nutrient runoff from agriculture and are increasingly common worldwide. On Maribo Simon Donner writes about how the ongoing floods in the upper Mississippi are likely to produce the largest ever ‘dead zone’ in the Gulf of Mexico. Simon writes:

Nitrogen applied to crops like corn in the Midwest is the major driver of the now famous Dead Zone, as I’ve described in a number of previous posts and this Google News commentary. The blame for the high nitrogen levels in the Mississippi and this year’s record Dead Zone forecast is being placed on the production of more corn for ethanol. A more complete explanation would be that the surge in corn production, and, hence, fertilizer use, the past few years has made nitrogen pollution more sensitive to the climate than ever.

Nitrogen and hydrology are tightly linked in the Mississippi River Basin, and other agriculturally intensive river basins, thanks to nature and to humans. Several nitrogen ‘species’ like nitrate are highly soluble. What has exacerbates things in the Mississippi is activities like wetlands, installing artificial drainage under fields and channelizing rivers that reduce chances for nitrogen to be consumed before moving downstream. The result is the amount of nitrogen that the Mississippi sends to the Gulf can actually be predicted from the rainfall in the Corn Belt.

In coverage of our recent paper on corn and the Dead Zone, the prediction that the US Energy Policy would increase average nitrogen loading by 10-34% drew most of the attention. What might be missed is that the nitrogen loading could be much higher if the conditions are wetter.

The reason this matters is the the continental shelf of the Gulf of Mexico has a memory. The usual tale is that the Dead Zone grows each spring and summer when the big flood of Mississippi nitrogen arrives weather and water conditions are ripe for algae growth (it breaks up in the fall when the waters cool and mix, reintroducing oxygen to the bottom waters). However, nitrogen from previous years that is deposited in the sediments can also be recycled and feed algae growth. In other words, the system remembers a big flood of nitrogen. For example, during the 1993 Mississippi floods, the Dead Zone grew to a then-record 17,600 km2; the next year, it grew to an almost equal 16,600 km2, despite 31% less nitrate flowing down the Mississippi. That’s just one reason why it is critical to consider climate and climate variability in ecological management and policy.

This year, the Dead Zone is projected to reach over 25,000 km2 in size, 20% greater than the previous maximum. What will that mean for 2009? For 2010? The longer you wait, the harder problem like the Dead Zone are to solve.

One thought on “The Mississippi dead zone will grow due to this year’s floods”

  1. If we can find ways to educate the opinion-makers and Ďtalking headsí in the mass media who are ‘educating’ us now. That could be a step forward in terms of successfully establishing behavior changes grounded in competence and improved reality-orientation.

    The family of humanity is only now starting to learn unexpectedly and painfully about certain human-induced global threats that could soon be presented to the human community by the seemingly endless growth of per human consumption and unbridled production activities increasing exponentially and overspreading the surface of Earth in our time.

    Let us the consider the way many too many economists, politicians and their super-rich benefactors who primarily govern the workings of the news media, report to us that Earth can indefinitely sustain people conspicuously consuming its limited resources the way millions of fortunate people worldwide are doing; but I fear these intelligent Ďdreamersí have lost their reality-orientation with regard to human biological limits and the limitations of the bounded physical world we inhabit. The Earth is relatively small, evidently finite and noticeably frangible; it is neither an eternal provider like a motherís teat nor is it an endlessly overflowing cornucopia. Unlimited expansion of the global economy without regard to limits to its growth that are inevitably imposed by a finite world is an end-all strategy, I suppose.

    A planet with the limitations and the make-up of Earth cannot realistically be expected to much longer maintain profligate over-consumption and adamantine hoarding of limited resources as well as seemingly endless expansion of production capabilities by millions of people, mostly in the overdeveloped world, that we see occurring as a result of actions by a tiny minority of selfish people who possess the wealth and power needed to behave in this ostentatious way.

    Obscene displays of consumption by self-seeking people with great wealth could be directly undermining the biophysical integrity of Earth as well as precipitating deleterious effects upon its environs. Please consider how scarce resources are being recklessly dissipated and global ecosystems relentlessly degraded at a much faster rate than the Earth can restore its resources and ecological services for human benefit. Unintended, pernicious challenges resulting from the unrestrained increase of per capita over-consumption of Earthís finite resources and the unbridled growth of economic globalization appear to be threatening to ravage our planetary home.

    Perhaps the current scale as well the anticipated growth of per human over-consumption and the global economy could become unsustainable well before the year 2050.

    Steven Earl Salmony
    AWAREness Campaign on The Human Population,
    established 2001

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