Abstract
Climate is changing across the world, including the major maize-growing state of Iowa in the USA. To maintain crop yields, farmers will need a suite of adaptation strategies, and choice of strategy will depend on how the local to regional climate is expected to change. Here we predict how maize yield might change through the 21st century as compared with late 20th century yields across Iowa, USA, a region representing ideal climate and soils for maize production that contributes substantially to the global maize economy. To account for climate model uncertainty, we drive a dynamic ecosystem model with output from six climate models and two future climate forcing scenarios. Despite a wide range in the predicted amount of warming and change to summer precipitation, all simulations predict a decrease in maize yields from late 20th century to middle and late 21st century ranging from 15% to 50%. Linear regression of all models predicts a 6% state-averaged yield decrease for every 1°C increase in warm season average air temperature. When the influence of moisture stress on crop growth is removed from the model, yield decreases either remain the same or are reduced, depending on predicted changes in warm season precipitation. Our results suggest that even if maize were to receive all the water it needed, under the strongest climate forcing scenario yields will decline by 10–20% by the end of the 21st century.
Highlights
Cereal crops, including maize, are the most important food source for human consumption [1], and as global population increases, crop production must increase
While the increase in historic yield is attributed to a combination of breeding and management practices [43], Agro-IBIS implicitly simulates this trend as a result of increasing nitrogen fertilizer application rates
Simulated yields averaged across all grid cells driven by Climate Research Unit (CRU) data are overestimated compared with observations between 1970 and 2000, likely a result of the model only responding to nitrogen and moisture stress but to no other stresses that can affect actual crop yields, as well as the fixed growing degree days (GDD) required for maturity at a relatively high value
Summary
Cereal crops, including maize, are the most important food source for human consumption [1], and as global population increases, crop production must increase. It is estimated that 60% more food will be required by 2050 (compared to 2005) to meet human nutrition needs [2]. The United States (USA) is the world’s largest producer and exporter of maize (USDA ERS; http://www.ers.usda.gov/topics/crops/corn/.aspx), and Iowa accounts for only 1.5% of the land area of the USA, it has consistently produced more maize than any other state over the past 20 years [3], with nearly 14 million acres planted in 2012. Other top crops include soybean (9.8 million acres), and hay (1.1 million acres) (http://quickstats.nass.usda.gov). The future of maize production in Iowa and surrounding high-producing states is a concern for the global maize economy and future food security. With maize yield variability driven strongly by climate variability, predicting future maize yields relies on understanding how climate change will affect maize growth and development
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