and their strength is more or less constant all year round. 全年始终或多或少地 受到这种影响力的控制

163. the world's entire population in a single flock.
     仅这一群便集中了世界上所有的花脸鸭
164. But there are parts of the world that have no seasons.
     但是 世界上有些地方却没有四季
165. In the tropics the sun's rays strike the earth head on
     在热带地区 太阳辐射直射大地
166. and their strength is more or less constant all year round.
     全年始终或多或少地 受到这种影响力的控制
167. That is why the jungle grows so vigourously
     因此 这里的丛林茂密葱郁
168. and supports so much life.
     生命在此欣欣向荣
169. This forest covers only 3 percent of the planet's surface,
     这些森林仅覆盖了地球表面的3%

来自《行星地球 第一季 第一集 Planet Earth S01E01 从北极到南极》第 166 行