黃金閱讀裡的這句話 - 英檢

During the dry periods that are common phenomena along the desert margins,
(though, the pressure on the land is often far in excess of its
diminished capacity, and desertification results.)


這是黃金閱讀裡沙漠化的文章，括號內是我看不懂的句子結構

請板上高手解析

謝謝~


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