During the last recession, migration to the sunbelt accelerated.
前一个经济萧条期间，向美国南部阳光地带移民的速度加快了。
What does this migration not do?
这种迁移不能做什么？
Now, migration is a natural survival strategy.
现在，迁徙是一种自然的生存策略。
They have led some birds to give up on migration.
它们导致一些鸟类放弃迁徙。
Assisted migration really needs this level of oversight, and soon.
辅助迁移确实需要这个层次的监督，而且是急需。
Considerations of this sort lead to the development of migration flow.
这类考虑导致了移民流动的发展。
The effects of migration are more complex than these theorists presume.
移民的影响比这些理论家假设的要复杂得多。
Human behaviour, however, is having a detrimental impact on animal migration.
然而，人类行为正在对动物迁徙产生不利的影响。
Migration is usually defined as "permanent or semipermanent change of residence".
移民通常被定义为“永久或半永久的居住变化”。
Seasonal migration is another form of escape, especially for large mammals or birds.
季节性迁徙是另一种逃避方式，特别是对大型哺乳动物或鸟类来说尤为如此。
"Regions of outward migration allow planets and planetoids to survive, " Mac Low said.
麦克·劳说：“向外迁移的地区使行星和小行星得以生存。”
Certain characteristics of American society help to explain this remarkable migration.
美国社会的某些特点有助于解释这种显著的移民现象。
Animal migration, however it is defined, is far more than just the movement of animals.
无论如何定义，动物迁徙都远远不止是动物的移动。
As recently as five years ago, US migration was twice the rate of European Union states.
就在5年前，美国的移民率还是欧盟国家的两倍。
The most radical strategy being debated among conservation biologists is Assisted Migration.
保护生物学家们争论的最激进的策略是辅助迁移。
Without more research, we can't predict if Assisted Migration will work for any given species.
没有更多的研究，我们无法预测辅助迁移是否适用于某一特定的物种。
Whether to use Assisted Migration, this debate is mostly within the biology community right now.
是否应该采用辅助迁移目前主要是生物学界争议的话题。
But was there one major wave of migration across the Bering Strait into the Americas, or several?
但是有没有一次或几次大移民浪潮是穿过白令海峡到达美洲的呢？
Was there only one outward migration from a single point in Asia, or several from different points?
在亚洲，是否只有一个或多个移民点向外迁移？
When the lemmings' food supply becomes too low to support the population, a singular migration commences.
当旅鼠的食物供应不足以维持种群时，一次特别的迁徙就开始了。
The most influential proponent of the coastal migration route has been Canadian archaeologist Knut Fladmark.
沿海移民路线最具影响力的支持者是加拿大考古学家克努特·弗拉德马克。
From this evidence it was deduced that there had been three major waves of migration across the Bering Strait.
从这个证据可以推断，横跨白令海峡的大型移民潮曾经有过三次。
When the planetarium sky matched the sky outside, the birds fluttered in the direction of their normal migration.
当天文馆的天空与外面的天空相匹配时，鸟儿们就朝着它们正常迁徙的方向飞翔。
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