Low-hanging fruit? Identifying opportunities to enhance crop diversity in the United States

Abstract

The benefits of crop diversification for key agro-environmental outcomes are well-established, yet the pathways to realizing this diversification at larger scales remain murky. We propose a framework to evaluate possible spatial and temporal crop arrangements that meet specific crop diversity targets by drawing on empirical data across millions of individual crop fields and their recent cropping histories in the US (2015-2022). Specifically, we develop a simple rule-based model to raise crop species diversity to various levels of spatial and temporal crop diversity (driven by crop rotations) already attained by farmers in areas with broadly similar soils and climate (‘attainable diversity’). We demonstrate that small changes on the local scale have sizeable cumulative effects. For example, switching crops in 3.4% of fields (corresponding to 12.4% of US cropland area) in the 75th percentile attainable diversity scenario would raise national-scale crop diversity by over 50% (effective number of crop species increased from 7.6 to 11.5). These simulated changes in crop diversity have clear spatial patterns associated with cropland extent and field size. Finally, we examine how the geographic redistribution of key commodity crops (maize, soybean, and wheat) resulting from these crop switches would influence crop yield and production outcomes. While geographic redistribution has limited influence on yields of these three crops, including some potential yield gains, net national production declines (by ∼10%-13% in our main spatial diversification scenario) due to their reduced share in the cropland portfolio as minor crop groups expand. By drawing on a pool of crops that are already grown in areas with similar field sizes, climate, and soils, our results can help inform realistic strategies toward national-scale crop diversification—illustrating potential ‘low-hanging fruit’ for crop transitions across different landscapes. Our proposed empirical attainable diversity framework adds nuance around the opportunities and barriers associated with efforts to raise agrobiodiversity.