is on a knife edge. 生命如履薄冰

43. Alone and without the protection of its parents,
    缺少了父母的保护
44. this hatchling's chances are slim.
    这只雏鸟的生存机会十分渺茫
45. Survival here, as in all deserts,
    在沙漠中生存
46. is on a knife edge.
    生命如履薄冰
47. So desert dwellers have had to evolve in remarkable ways.
    因此 沙漠的居民必须以非凡的方式进化
48. Some have even given rise to legends of dragons and unicorns.
    其中有些生物成了龙与独角兽传说的源头
49. And even the dunes have their own magical quality.
    甚至贫瘠的沙丘也有其独到的特质

来自《行星地球 第三季 第三集 Planet Earth S03E03 沙漠与草原》第 46 行