A polytunnel is a similar structure but made using plastic instead of glass.

塑料大棚是一个类似的结构，但由塑料而非玻璃制成。

Production is decreasing despite improvements in how food is grown, especially the use of glasshouses and polytunnels.

尽管粮食种植方式有所改善，特别是温室和塑料大棚的使用，但粮食产量仍在下降。

And when you think about how much investment there has been in glasshouses and polytunnels since 1985 in a way that's transformed UK supply, quite frankly, the fact that this is what's being forecast is extraordinary.

想一想自1985年以来，有多少投资花在温室和塑料大棚上，这在某种程度上改变了英国的供应，坦白地说，人们预测出的事实非同寻常。