Guest essay by Indur M. Goklany

The BBC in an otherwise good article by Tim Harford, the well-known economist and a regular contributor to The Financial Times and Slate, reminds us that fossil fuels are essential to manufacturing nitrogenous fertilizer and, therefore, to feeding humanity. He then goes on to note that the use of such fertilizers contributes to various environmental problems:

[They emit] compounds like nitrous oxide [which] are powerful greenhouse gases. They pollute drinking water. They also create acid rain, which makes soils more acidic, disrupting ecosystems, and threatening biodiversity.] When nitrogen compounds run off into rivers, they likewise promote the growth of some organisms more than others. The results include ocean “dead zones”, where blooms of algae near the surface block out sunlight and kill the fish below.

Unfortunately, this list, like current calculations of the “social cost of carbon” (SCC) calculations, omits any mention of what is probably the single most important environmental impact of fertilizers (and fossil fuels), viz., the increased productivity of land not only helps feed humanity but that it also save land for nature.

In a previous post on this blog titled, Have Fossil Fuels Diminished the World’s Sustainability and Resilience?, I reported that fossil fuels provide at least 60% of humanity’s food and clothing, which would otherwise have to be obtained through increased conversion of land to agriculture.

About 80% of this 60% contribution from fossil fuels is due to nitrogenous fertilizers produced via the Haber-Bosch process.[1] Thus, absent fossil fuels, global cropland would have had to increase by at least 150 percent to meet current food demand. In other words, to maintain the current level of global food production, at least another 2.3 billion hectares of habitat would have to be converted to cropland, over and above the 1.5 billion hectares currently used for cropland worldwide. This is equivalent to the combined total land area of the United States, Canada, and India.

Considering that habitat conversion is widely acknowledged to be the single greatest threat to biodiversity, the additional stress on ecosystems and global biodi­versity from the conversion of an additional 2.3 billion hectares or more of habitat to cropland is inestimable.

But conversion of habitat to cropland is already the greatest threat to biodiversity (see, e.g., here). By reducing such conversion even as they enabled greater food production, fossil fuels not only saved humanity from nature’s whims, but they also shielded much of the rest of nature (that is, habitat that has not already been lost or degraded) from humanity’s covetous gaze.

There is yet another avenue by which fertilizer use helps enhance nature. Mr. Harford’s article hints at this, but does not elaborate. Specifically, nitrogenous fertilizers increase the productivity not only of the specific lands on which they are applied but any other land that they end up on via a variety of air, water or other environmental pathways. One consequence of this, is that the whole earth’s productivity has been enhanced. According to a recent paper, such nitrogen deposition, to which fertilizer usage and fossil fuel combustion contribute, may be responsible for 9% of the increase in the earth’s greening from 1982–2009. [By contrast, the paper attributes 70% of the additional greening to carbon fertilization.]

[1] Goklany, Humanity Unbound: How Fossil Fuels Saved Humanity from Nature and Nature from Humanity. Policy Analysis, No. 715, Cato Institute, Washington, DC (2012).

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