Land system intensification within safe limits balances crop production–antibiotic pollution tradeoffs

Crop intensification has increased agricultural production albeit with an increase in field antibiotic pollution. Here, we project how antibiotic pollution undermines production and how intensification needs to be kept below a threshold.
Published in Earth & Environment
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Origins and risks of soil antibiotic pollution

In China, to feed billions of people, the demand for crops will increase in the coming decade. Arable land expansion and agricultural input increases have substantially improved crop production, however, the benefits for crop yields always are paralleled with soil pollution risks (e.g., antibiotics). Antibiotics are generally used for human/animal disease treatments, and livestock production as feed additives. Most of antibiotics are excreted into environment via feces and urines. Then the antibiotic-contaminated manure application and wastewater irrigation enrich antibiotics in agricultural soils. Antibiotics as one of emerging contaminates can inhibit crop growth via complex interactions within soil-crop systems. For example, an excess of crop exposure to antibiotics can decrease germination, root and stem elongation. On the other hand, antibiotics can also change nutrient cycling (e.g., carbon, nitrogen) through disturbances to soil microbial community structure and functioning. When the concentrations of antibiotics exceeded their predicted no-effect concentrations, they will potentially imposed serious risks to crop production.

In this study, we employed risks assessment model and random forest model to project soil antibiotic pollution risks to crop production across China, where rice, wheat, maize, and vegetables consistently have relatively low yields when they were exposed at high level soil antibiotic pollution risks (i.e., risk quotient exceeding 8.30–9.98). Overall, although arable land expansion and agricultural input increases significantly promote crop production, the parallel soil antibiotic pollution will risk decline in crop yields. Behind this is the offset to benefits for crop production that is attributed to soil antibiotic pollution, raising the concerns for tradeoffs between antibiotic pollution and crop yields at different geographical scales.

a, b, Maps of the cumulative risks associated with target antibiotics and uncertainties associated with the predictions. c, Density distribution of risks associated with each antibiotic; the ridge line plots the estimated density from predicted data. d–g, Convex nonlinearities in the relationships between crop yields and antibiotic pollution risks. The lines (regression lines) and shaded areas (95% confidence intervals) were estimated by generalized additive models.

Fig. 1 | Risks of antibiotics in soil to crop production in China. a, b, Maps of the cumulative risks associated with target antibiotics and uncertainties associated with the predictions. c, Density distribution of risks associated with each antibiotic; the ridge line plots the estimated density from predicted data. d–g, Convex nonlinearities in the relationships between crop yields and antibiotic pollution risks. The lines (regression lines) and shaded areas (95% confidence intervals) were estimated by generalized additive models.

Sustainable land system intensification

Land system intensification entails tradeoffs more often than win–win outcomes. Sustainable land system intensification is central to address the world’s food needs, and it is important to know how human societies manage and interact with land systems to balance the tradeoffs between antibiotic pollution and crop yields. Our results here show that growth rates for crop yields slow down when the land system intensification reach a relative high value while the exponential growth of soil antibiotic pollution risks occurs. When relative benefits for crop yields subtract relative benefits for antibiotic pollution, we generally found convex nonlinearities in these tradeoffs at multiple geographical scales. The thresholds–maximum acceptable limits (the tradeoffs take their maximum values)–have been set in this study, which is comfortable for decision making of land system planning and management. As long as the thresholds are crossed, we can be pretty sure the relative benefits for crop yields decrease.

Fig. 2 | Examples of tradeoffs between antibiotic pollution risk and crop yield with increasing land system intensification. Nonlinear relationships between risk–yield tradeoffs and land system intensification. The green and yellow lines are constraint lines of scaled crop yields and scaled antibiotic pollution risks (RQs) based on the scattered point clouds. The tradeoff (cyan lines) is defined as scaled yield minus scaled RQ, which represents that benefits for crop yield are higher than risks when the value is higher than zero. 

The sustainable land system management is strongly encouraged to achieve win–win social-ecological outcomes. As we see anthropogenic disturbances in the Earth system, we need to decide how we begin now to sustain something that is essential for human well-being. Prevention of soil antibiotic pollution is critical now if we want to get enough food and reduce soil antibiotic pollution risks. Unfortunately, policymakers are facing difficult decisions and management on a broad scale. The safe limits of soil antibiotic pollution for soil biome security are still not defined worldwide. As the first step, land system intensification towards sustainability within thresholds can balance the tradeoffs between crop production and antibiotic pollution. (The text is edited by Fangkai Zhao and Liding Chen)

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