Dry lands are particularly affected by these trends, as livestock are often the only source of livelihoods for the people living in these areas.
干旱土地尤其受到这些趋势的影响，因为畜牧业往往是生活在这些地区的人口的唯一生计来源。
Agriculture provided a more dependable source of food, causing populations to increase; eventually excess population migrated to new lands.
农业提供了更加可依赖的粮食来源，使人口增长；最终过多的人口迁移到新的土地。
Now genetic studies show that the southern United States, not these native lands in South America, is the source of multiple new invasions around the globe.
现在的遗传学研究表明，这些美国南部的火蚁并不是南美原产的那种，而是来自世界各地的生物入侵。
Animal manures were the main source of organic fertilizer, but their application for farming lands were limited due to a lot of pathogens, parasite ova and toxicant contained.
尽管畜禽粪便是有机肥料的主要来源，但是其携带的大量病原菌、寄生虫卵和有毒物质是影响畜禽粪便农田利用的主要原因。
Animal manures were the main source of organic fertilizer, but their application for farming lands were limited due to a lot of pathogens, parasite ova and toxicant contained.
尽管畜禽粪便是有机肥料的主要来源，但是其携带的大量病原菌、寄生虫卵和有毒物质是影响畜禽粪便农田利用的主要原因。
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