Nature News & Comment
Many tropical species never experience extreme heat or cold. That may doom them in a warming world.
Janzen's pivotal idea came to him in the mid-1960s, when the young ecologist at the University of Kansas in Lawrence was travelling around Costa Rica with 20 US students and a Costa Rican assistant. The trip began in the assistant's home city of San José, which had a 'bland' climate that was, Janzen says, “not too hot, too cold, too wet or too dry”. From there, they travelled to a dry tropical forest at sea level, where the weather was hotter. During a lecture, Janzen saw sweat pouring off his assistant. “And I looked at the students and none of them was sweating,” says Janzen.
Later, when the group moved to a field station at 3,000 metres elevation in the cold, wet cloud forest, Janzen saw his assistant “sitting with piles of blankets on him. Everyone else was sitting there in khakis. I realized this guy has spent his life in San José, which is like sitting in a climate-controlled cabinet.”