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No long-term fix

Letter to the Editor of New Scientist. Published 2001-05-28 Vol. 210 No. 2814 p.30-31 Download reference in RIS format.

Letter as published

Creating nitrogen-fixing, non-leguminous crop (7 May, p8) to boost food supply could support an increased human population only to have it face the “end’ of mineral nutrients extracted from the earth, such as phosphorus and potassium.

Nitrogen is an atmospheric plant nutrient, along with carbon, oxygen and hydrogen.  We are not at risk of running of atmospheric nutrient as the atmosphere rapidly cycles them.

Nutrients from the rocks and soil of the lithosphere are only cycled at geological speed.  The current approach of mining them and then using them, often inefficiently, to boost crop yields before they are washed away on what, in human time scales, is effectively a one-way trip to the oceans, is foolhardy. 

Phosphorus will be the first to reach its peak production, in the next 50 to 100 years.  Others will follow such as potassium about 500 years. 

There are no known practical means of recycling lithospheric nutrients from the oceans back to farmland and, unlike energy, for which there are alternatives to fossil fuels, there are no substitutes for these elements.

Nitrogen fixing crops would only be setting humanity up for an even bigger fall. 

Letter as sent

Dear Editor

I was disappointed to see both the editorial and article on creating non-legume nitrogen fixing crops propagating the erroneous concept that we have to produce more food to feed a growing population. This idea is a classic example of having the cart in front of the horse: everything from thermodynamics to ecology is clear that biological populations grow to the limit of their food supply, never that food supplies expand to meet the demands of their consumers. Half the worlds population is not fed because of Haber-Bosch nitrogen, these 3 billion people only exist because of the H-B process, i.e., without it the worlds population would be half what it currently is. The number of humans on the planet is one of the primary underlying factors causing the ecological and environmental damage that threatens civilisation and even our entire species. We have to find effective and ethical means to manage the number of people to match the amount of food and other resources that can be produced without compromising the planetary systems on which we depend for our existence.

In addition the rather casual use of the term ‘fertiliser’ to mean both reactive N and all the lithospheric nutrients confused a much more subtle and serious situation. Nitrogen is an atmospheric plant nutrient along with carbon, oxygen and hydrogen, to lump them with the lithospheric nutrients is a grave error. We are never at risk of running out of atmospheric nutrients as the atmosphere rapidly cycles them for us. The lithospheric nutrients are an entirely different kettle of fish: they are only cycled at geological speed. The current approach of mining fossil lithospheric nutrients then using them (often very inefficiently) to boost crop yields before sending them, what in human time scales is effectively, on a one way trip to the oceans, can only be described as foolhardy. Phosphorous will be the first of the lithospheric nutrients to reach its ‘peak’ in the next 50-100 years, others will follow, e.g., potassium in about 500 years. Creating nitrogen fixing, non-legume crops to boost food supply will increase the human population, only to have it to run smack into the ‘end’ of fossil lithospheric nutrients. There are no known practical means of recycling the lithospheric nutrients from the oceans back to farmland and unlike energy, for which there are plenty of alternatives to fossil fuels, there are no substitutes for the chemical elements within biological systems. Creating non-legume nitrogen fixing crops is only setting humanity up for an even bigger fall in the future.

Yours

Charles Merfield

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