Review: Back-of-the envelope Fermi calculations in plant science

I think one of the most important lessons a scientist learns is to cross-check their findings with a different approach in order to determine if the findings are reasonable. This interesting article by Oliveira-Filho and Campos-Silva et al. lays out several examples of using back-of-the envelope or Fermi calculations to “gauge reality”. The authors provide a step-by-step guide including a logic chain and then demonstrate how this is done in practice. As an example, consider the feasibility of aviation “going green” by using only bio-jet fuels to power planes. It sounds like a great plan, but is it achievable? I’ll leave you to find the answer in the article. I think this resource can be quite useful for educators; an instructor can pose the provided questions to students, ask them for their a priori responses, and then ask them to run their calculations using the guidance provided. Sample calculations are provided to determine the amount of nitrogen fertilizer needed to replace the nitrogen harvested with corn grain, how much nitrogen fixed by the Haber-Bosch process can be replaced by legume cover crops, and others. This article is part of a Plant Physiology Focus Issue on the topic of Numeracy, Realism, and Relevance in Plant Science, coming out in May, 2025. (Summary by Mary Williams @PlantTeaching) Plant Physiol. 10.1093/plphys/kiae347