过往沙漠的南部边界比现在的边界更靠北，而半干旱的草原和较浅的淡水湖泊覆盖了现在干旱平原的大部分地区。

The southern frontier of the desert was far to the north of where it is now, while semiarid grassland and shallow freshwater lakes covered much of what are now arid plains.

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在许多半干旱的地区中，同样存在树带界限的下限区域；在这片区域之内，由于缺乏水分，森林下沿区域的植被通常会逐渐变成干草原或沙漠。

In many semiarid areas there is also a lower timberline where the forest passes into steppe or desert at its lower edge, usually because of a lack of moisture.

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一路上，我们破坏了大多数我们曾经耕作过的的土地，经常把翠绿的自然生态区变成了半干旱的沙漠。

Along the way, we despoiled most of the land we worked, often turning verdant, natural ecozones into semi-arid deserts.

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