求翻译：我国国土面积和美国差不多，但是可耕地面积只有美国的一半。因为中国拥有世界屋脊青藏高原，决定我国地势西高东低，并且将东亚季风气候限制在中国东部地区。导致降水量从东南向西北递减。其北侧形成了常年的西风带，使西北地区的蒸发量远远大于降水量，生态环境十分脆弱，并且造就了黄土高原。西部缺少淡水资源，严重限制了产业的进一步发展。中国的农业文明源于黄河流域，但是由于北方自然环境的限制以及高产作物的引入，使得人口不断向南转移，从而经济中心也随人口向南转移。是什么意思？

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My size and the United States, but almost arable land area is only half of that in the United States. Because China has the world's roof, and decided that my lying plateau west high and low, and East Asian monsoon climate restrictions will be in China's eastern region. lead to diminishing rainfall f

Land area in China and the United States, but arable land area of just United States half. Because China has a roof of the world in Qinghai-Tibet plateau, decided in China where West-East high low, and limit the East Asian monsoon climate in East China region. Lead to diminishing rainfall from the S