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Beneath the feet of dinosaurs 165 million years ago, a green fuzz of mossy vegetation was surviving the crush. As the Indian landmass began to slam into Asia 65 million years ago, eventually thrusting the Himalayas into existence, the plants rode along to the rooftop of the world, adapting to their new frozen, sunny environment. But this genus of land plants, thought to be among the oldest living on Earth, is now in decline, probably caused in part by climate change.