Reliable projections of crop production are an essential tool for the design of feasible policy plans to tackle food security and land allocation, and an accurate characterization of the long-run trend in crop yield is the key ingredient in such projections. We provide several contributions adding to our current understanding of the impact of climatic factors on crop yield. First of all, reflecting the complexity of agricultural systems and the time required for any change to diffuse, we show that crop yield in Europe has historically been characterized by a stochastic trend rather than the deterministic specifications normally used in the literature. Secondly, we found that, contrary to previous studies, the trend in crop yield has slowly changed across time rather than being affected by a single abrupt permanent change. Thirdly, we provide strong evidence that climatic factors have played a major role in shaping the long-run trajectory of crop yield over the decades, by influencing both the size and the statistical nature of the trend. In other words, climatic factors are important not only for the year-to-year fluctuations in crop yield but also for its path in the long-run. Finally, we find that, for most countries in this study, the trend in temperature is responsible for a reduction in the long-run growth rate of yield in wheat, whereas a small gain is produced in maize, except for Southern European countries.

中文翻译：

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欧洲农业产量和气候因素的长期趋势

可靠的作物产量预测是设计解决粮食安全和土地分配的可行政策计划的重要工具，准确描述作物产量的长期趋势是此类预测的关键因素。我们提供了一些贡献，增加了我们目前对气候因素对作物产量影响的理解。首先，反映农业系统的复杂性和任何变化扩散所需的时间，我们表明欧洲的作物产量历来以随机趋势为特征，而不是文献中通常使用的确定性规范。其次，我们发现，与之前的研究相反，作物产量的趋势随时间缓慢变化，而不是受到单一突然的永久性变化的影响。第三，我们提供了强有力的证据，表明气候因素通过影响趋势的规模和统计性质，在过去几十年中在塑造作物产量的长期轨迹方面发挥了重要作用。换句话说，气候因素不仅对作物产量的逐年波动很重要，而且对其长期路径也很重要。最后，我们发现，对于本研究中的大多数国家，温度趋势是导致小麦长期产量增长率下降的原因，而玉米产量略有增加，但南欧国家除外。气候因素不仅对作物产量的逐年波动很重要，而且对其长期路径也很重要。最后，我们发现，对于本研究中的大多数国家，温度趋势是导致小麦长期产量增长率下降的原因，而玉米产量略有增加，但南欧国家除外。气候因素不仅对作物产量的逐年波动很重要，而且对其长期路径也很重要。最后，我们发现，对于本研究中的大多数国家，温度趋势是导致小麦长期产量增长率下降的原因，而玉米产量略有增加，但南欧国家除外。