英语听力：自然百科 探索世界奥秘之Wild Africa - Deserts(浩瀚沙漠) Unit08（在线收听）

Within a month, the spring blooms are finished. The plants now set their seeds, taking advantage of the warm summer winds which sweep the desert.

For a while, the karoo just glows.

But trouble is stiring. Triggered by the rains, an all-devouring army-- locusts.

Millions emerge from eggs buried in the sand, gathering into columns which may stretch for ten kilometers. At this stage, they can't fly, only hop, but it doesn't hinder their progress. These sweeping hordes devastate any fresh growth in their path.

After five weeks of steady munching, the infantry becomes airborne. These breeding swarms can cover up to 80 kilometers a day, but only while the food and moisture last.

So how do you define a desert in Africa? They are places where less than 50 centimeters of rain falls a year. Neighbouring the karoo is a desert which gets the maximum, in brief, but intense summer monsoons.

words and expression:

1.karoo: an arid plateau of southern Africa非洲干旱的南方

2.locust:any of numerous grasshoppers of the family Acrididae, often migrating in immense swarms that devour vegetation and crops蝗虫

3.horde:swarm群

4.munch:to chew food audibly or with a steady working of the jaws发出声音或高兴地吃

5.infantry becomes airborne:步兵变成空降兵

6.monsoon:a wind system that influences large climatic regions and reverses direction seasonally季风