Of course, tropical zones themselves are expanding.

当然热带本身也是扩张的。

SUEtheTrex, " Ornithology question: " Do birds in tropical zones migrate like they do in temperate climates?

SUEtheTrex 问，鸟类学问题：热带地区的鸟类会像在温带气候中的鸟那样迁徙吗？

But soon, some of our Sun-adapted ancestors migrated northward out of the tropical zone, spreading far and wide across the Earth.

可是不久，一些适应了强紫外线的居民开始北上，逐渐离开热带区域 分散到世界各地。

All these areas would be considered temperate compared  to subarctic, continental or tropical zones, with no extreme winter temperatures, and some  relief from heat at some time in the year.

与亚北极、大陆或热带地区相比，所有这些地区都被视为温带地区，冬季没有极端气温，一年中某些时候的炎热程度有所缓解。