Harvested perennial grasslands: Ecological models for farming’s perennial future

Humanity’s unprecedented global demand for farm products poses one of the greatest threats to global biodiversity and ecosystem function. This demand will almost certainly increase as the human population continues to expand over the next several decades. Annual crops supply much of that demand and occupy roughly 85% of global croplands (Monfreda et al., 2008). Staple grain crops, such as wheat, rice, and maize, alone provide more than 70% of human food calories and occupy 69% of global cropland. During the last half of the 20th century, farmers, overall, kept pace with or exceeded global food demands by expanding production onto previously unexploited landscapes and by utilizing new crop varieties, agricultural technologies, and management practices. Now, however, much of the global lands best suited for annual crop production are already in use. More marginal lands, which are at greater risk of degradation under annual crop production, are increasingly being exploited. Climate change, resource scarcity, and continued land degradation, which forces farmers onto even more marginal lands, exacerbates the problem of developing sustainable agricultural systems in the 21st century.

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