What about supply? The three environmental trends—the shortage of fresh water, the loss of topsoil and the rising temperatures—are making it increasingly hard to expand the world's grain supply fast enough to keep up with demand.
出自-2016年6月阅读原文
The three environmental trends—the shortage of fresh water, the loss of topsoil and the rising temperatures—are making it increasingly hard to expand the world's grain supply fast enough to keep up with demand.
2016年6月四级真题（第一套）阅读 Section B
柯林斯高阶英汉双解学习词典释义
N-UNCOUNT
表土（层）
Topsoil is the layer of soil nearest the surface of the ground.