CSIRO Agriculture and Food, 306 Carmody Road, St Lucia, QLD, 4067, Australia.
CSIRO Agriculture and Food, PMB 2, Glen Osmond, SA, 5064, Australia.
Glob Chang Biol. 2017 May;23(5):2071-2081. doi: 10.1111/gcb.13604. Epub 2017 Jan 24.
Global food security requires that grain yields continue to increase to 2050, yet yields have stalled in many developed countries. This disturbing trend has so far been only partially explained. Here, we show that wheat yields in Australia have stalled since 1990 and investigate the extent to which climate trends account for this observation. Based on simulation of 50 sites with quality weather data, that are representative of the agro-ecological zones and of soil types in the grain zone, we show that water-limited yield potential declined by 27% over a 26 year period from 1990 to 2015. We attribute this decline to reduced rainfall and to rising temperatures while the positive effect of elevated atmospheric CO concentrations prevented a further 4% loss relative to 1990 yields. Closer investigation of three sites revealed the nature of the simulated response of water-limited yield to water availability, water stress and maximum temperatures. At all three sites, maximum temperature hastened time from sowing to flowering and to maturity and reduced grain number per m and average weight per grain. This 27% climate-driven decline in water-limited yield is not fully expressed in actual national yields. This is due to an unprecedented rate of technology-driven gains closing the gap between actual and water-limited potential yields by 25 kg ha yr enabling relative yields to increase from 39% in 1990 to 55% in 2015. It remains to be seen whether technology can continue to maintain current yields, let alone increase them to those required by 2050.
全球粮食安全需要谷物产量在 2050 年前继续增长，但许多发达国家的产量已经停滞不前。这一令人不安的趋势至今仍未得到充分解释。在这里，我们表明，自 1990 年以来，澳大利亚的小麦产量已经停滞不前，并研究了气候趋势在多大程度上解释了这一观察结果。基于对 50 个具有优质天气数据的站点的模拟，这些站点代表了粮食区的农业生态区和土壤类型，我们表明，在 26 年的时间里，从 1990 年到 2015 年，水分限制的产量潜力下降了 27%。我们将这一下降归因于降雨量减少和气温上升，而大气 CO2浓度升高的积极影响使产量相对于 1990 年的水平仅减少了 4%。对三个站点的更深入调查揭示了模拟的水分限制产量对水分供应、水分胁迫和最高温度的响应的性质。在这三个站点，最高温度加快了从播种到开花和成熟的时间，并减少了每平方米的谷物数量和每粒的平均重量。这种由气候驱动的水分限制产量下降了 27%，但并没有完全体现在实际的国家产量中。这是由于技术驱动的收益前所未有地提高，缩小了实际产量和水分限制潜力产量之间的差距，使相对产量从 1990 年的 39%增加到 2015 年的 55%。目前还不清楚技术是否能够继续维持当前的产量，更不用说提高到 2050 年所需的水平了。
