Dead Zones: Farming Destroys Fishing

This is the fourth of five blogs-slash-essays on how the breakdown of ecosystems around the planet will likely impact global civilization’s ability to feed all the many billions of people in the coming decades. To get a sense of how different our future might be (that is, how different we are making it), I review three natural catastrophes in-the-making— The End of the Amazon; Dead Zones: (Farming destroys fishing); and The Insect Armageddon. Each provides a different lens into the larger biospheric catastrophe.

The impact of industrial agriculture does not stop at the farm’s boundaries. On this planet, there are few if any impermeable boundaries. The carbon dioxide in the air is taken in by leaves and turned into the hard woody body of trees and other plants. Water moves through the oceans, the air, rivers, and the bodies of organisms, one to the next, as if it were the bloodstream of the planetary systems. With it now travel the plastics, pesticides, and nitrogen and phosphorous compounds that industrial processes have recently released into circulation. The precise impact of many pollutants has yet to be clearly identified, but that they have been implicated in cancers and numerous grizzly deaths of all types of organisms has surprised no one outside of the chemical industry.[i] The environmental consequences of using chemical fertilizers, on the other hand, are well documented.

The amount of nitrogen released by livestock manure and synthesized for fertilizers in chemical factories by companies like Nutrien and Mosaic rival, if not exceed, all the nitrogen fixed by the rest of nature.[ii] In a landmark paper in the journal Nature, Johan Rockström and a team of eminent scientists found that, along with mass extinctions and climate change, the human additions of reactive nitrogen have dangerously exceeded the “safe operating boundaries” of our planet.[iii] In the case of reactive nitrogen, they estimated that Civilization has exceeded safe limits about four-fold.[iv] Indeed, in the journal Science, scientists concluded that humans have likely had the most profound impact on the complex cycling of nitrogen “since the major pathways of the modern cycle originated some 2.5 billion years ago.”[v]

Inefficiency is greatly to blame. Very little (about twelve percent) of the reactive nitrogen we apply to farmland actually makes it all the way into our mouths.[vi] Crops take up about forty percent of what is applied to farmland, and much of the rest—easily 50 million tons a year—is removed from the fields by rain and transferred via rivers to lakes and the world’s coastal waters.[vii] Since reactive nitrogen determines, to a great extent, how much life an ecosystem can support, this nutrient behaves like a magnet to living organisms. Wherever it goes, life feeds on it and proliferates. When reactive nitrogen moves into a place suddenly and plentifully, it sets off a feeding frenzy among the one-celled organisms, often disrupting the balance of that ecosystem.

Rivers that drain the world’s large farmlands bring the excess nitrogen to estuaries, seas, and oceans. It is the same system that for billions of years has transported the nutrients eroded from the continents to the oceans, making the shallow waters off the world’s coasts the feeding grounds for ninety percent of sea life, for everything from the single-celled phytoplankton to the great whales. It is where all our seafood comes from—the tuna, salmon, cod, sardines, shrimp, crabs, shellfish, everything.

So, in these same nearshore waters, the human-synthesized nutrients stimulate a population explosion of phytoplankton and cyanobacteria, euphemistically called algal blooms. When these microscopic organisms die, the bacterial decomposers that feed on them now experience their population explosion, depleting dissolved oxygen levels in the process. This leads to hypoxic (low oxygen) or even anoxic (severe hypoxic) conditions in the water. The other organisms either flee the oxygen-starved area, or, if they cannot, they suffocate and die. Fish, shrimp, and squid usually get away.[viii] The bottom dwellers like skate, flounder, and croaker, and the immobile creatures like the shellfish do not. In this way, during the months that farmers are fertilizing their fields, the usually biologic-rich coastal waters are turned into “dead zones.”[ix] Losses due to hypoxia were estimated to be about 83 thousand tons annually of fish and other life in the Chesapeake Bay and over 235 thousand tons in the Gulf of Mexico.[x] Due to a combination of dead zones and overfishing in the Baltic Sea, cod stocks have collapsed and herring catches have plummeted from the 100,000-ton annual limit in the 1980s to a paltry 1,500 tons in 2020.[xi]

Worldwide, dead zones have rapidly increased in number, size, and longevity.[xii] There were about ten documented cases in 1960. They have doubled in number every decade since.[xiii] Presently, over four hundred coastal areas experience dead zones sometime during the year.[xiv] The North Sea, the Baltic Sea, the Black Sea, the Gulf of Mexico, the Chesapeake Bay, the Adriatic Sea, the South China Sea, the seas around Korea and Japan—these oft blighted waters were until recently the world’s seafood cornucopias.[xv] The one in the Gulf of Mexico—the sink for the Mississippi River and all the farmland it drains—grows to the size of the state of New Jersey and can persist for eight months at a time. Four times larger than that monstrosity is a dead zone in the Baltic Sea, fishing grounds for over a thousand years but now surrounded by the highly fertilized croplands and factory farms of Northern Europe.[xvi] As with the rainforests on land, we are destroying the long-term existence of the most bio-diverse, bio-dense regions in the oceans to feed ourselves for the short term.

ENDNOTES

[i] Millions—Binetti et al. (2008), Daley (2017). Plastics—Thompson et al. (2009). Implications—Préel (2022).

[ii] Crutzen (2002), Tilman et al. (2002), Clark and Tilman (2008), Gruber and Galloway (2008), Rockström et al. (2009), Bouwman et al. (2013), Milman (2017), Stevens (2019).

[iii] Rockström et al. (2009).

[iv] Rockström et al. (2009).

[v] Canfield, Glazer, and Falkowski (2010).

[vi] Galloway et al. (2003).

[vii] Galloway et al. (2004), Canfield et al. (2010), Stevens (2019).

[viii] Rabalais et al. (2002).

[ix] Matson et al. (1997), Malakoff (1998), Vance (2001), Ferber (2004), Sverdrup et al. (2005), Mee (2006).

[x] Biello (2008).

[xi] Sulija and Balsiunate (2020), Eurofish Magazine (2021).

[xii] Malakoff (1998), Ferber (2004), Diaz and Rosenberg (2008).

[xiii] Diaz and Rosenberg (2008). 

[xiv] Diaz and Rosenberg (2008).

[xv] Miller (2002:489), Galloway et al. (2003), Naylor et al. (2005), Sverup et al. (2005:339), Mee (2006), Diaz and Rosenberg (2008).

[xvi] Kryda (2014), Davis (2018).

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