New Study Concludes: If We Artificially Raise the Cost of Fertilizers, Farmers Will Use Less and Grow Less Food

Of course that’s not how this one is framed. It’s all about water quality.

Abstract

We utilize a coupled economy–agroecology–hydrology modeling framework to capture the cascading impacts of climate change mitigation policy on agriculture and the resulting water quality cobenefits. We analyze a policy that assigns a range of United States government’s social cost of carbon estimates ($51, $76, and $152/ton of CO₂-equivalents) to fossil fuel–based CO₂ emissions. This policy raises energy costs and, importantly for agriculture, boosts the price of nitrogen fertilizer production. At the highest carbon price, US carbon emissions are reduced by about 50%, and nitrogen fertilizer prices rise by about 90%, leading to an approximate 15% reduction in fertilizer applications for corn production across the Mississippi River Basin. Corn and soybean production declines by about 7%, increasing crop prices by 6%, while nitrate leaching declines by about 10%. Simulated nitrate export to the Gulf of Mexico decreases by 8%, ultimately shrinking the average midsummer area of the Gulf of Mexico hypoxic area by 3% and hypoxic volume by 4%. We also consider the additional benefits of restored wetlands to mitigate nitrogen loading to reduce hypoxia in the Gulf of Mexico and find a targeted wetland restoration scenario approximately doubles the effect of a low to moderate social cost of carbon. Wetland restoration alone exhibited spillover effects that increased nitrate leaching in other parts of the basin which were mitigated with the inclusion of the carbon policy. We conclude that a national climate policy aimed at reducing greenhouse gas emissions in the United States would have important water quality cobenefits.

https://www.pnas.org/doi/10.1073/pnas.2302087120#

They’ve got models.

Evaluation using four coupled models to relate carbon pricing to nitrate export to the Gulf of Mexico. (A: Left) Integrated modeling framework. The ENVISAGE global economic model determines the change in agricultural input prices due to climate policy. These price changes feed into the SIMPLE-G-US-CS gridded economic model of corn–soy production which has been calibrated to capture the yield responses to changes in nitrogen fertilizer applications estimated using the Agro-IBIS agroecosystem model. When confronted with these input price changes, farmers alter their fertilizer usage, thereby changing nitrogen leachate. Nitrogen leachate is routed through the Mississippi River Basin hydrologic system into the Gulf of Mexico using the WBM hydrological model. Imposed policies are depicted in white or black boxes, and uncertainties in key model parameters characterized by sensitivity analyses are listed in gray boxes (Table 1). (B: Right) Spatial distribution of the relative changes of key factors including crop output (top maps), nitrogen fertilizer applied (Middle), and fraction of nitrate flux ultimately entering the Gulf (Bottom). Callouts identify points in the modeling framework where each factor is calculated. Inset values for each map provide the basin-wide average value for each depicted variable (blue), and the total change for basin export in black. (C: Top) Nonlinear response between fertilizer application rate with crop yield and nitrate leachate below the root zone represented, respectively, by Gompertz and quadratic functions. Callout identifies the grid cell location of this example response.
https://www.pnas.org/doi/10.1073/pnas.2302087120#

They do note that their prescriptions will reduce agricultural output, although they likely underestimate the impact. That’s ok though. We can just buy more from overseas farmers. I kid you not. Emphasis mine.

The carbon prices imposed in this study resulted in consequential reductions on the order of 7.2% in corn and soy output from the Mississippi River Basin—roughly 20,000 tons of corn-equivalent output. SIMPLE-G-US-CS accommodated reduced corn and soy production through reduced domestic use (primarily in livestock feed), as well as diminished grain exports. In response to the elevated corn–soy prices, foreign producers would expand production.

https://www.pnas.org/doi/10.1073/pnas.2302087120#

Draconian Climate Policies fix everything. Don’t worry. Someone else will feed you.

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October 17, 2023 at 08:08PM