Global warming pushes species uphill and polewards. For higher latitudes this expansion has been observed hundredfold. But the crucial question is: What happens with the biodiversity hotspots in the rainforests?

Some scientists predict that many species will soon retract from the tropics or even disappear, but the lack of data has so far made it impossible to test this.

A current long-term study shows that birds in the Peruvian rainforest move uphill with higher temperatures or will even disappear to the mountaintop. "It's not a prediction anymore," says lead author Benjamin Freeman. "These changes are happening right now in front of our eyes."

The setting of this project is on a hike up the Cerro de Pantiacolla. The mountain transect serves as a miniature model for what might be happening in rainforests around the world.

It shows that biodiversity is being threatened in even untouched regions because of global warming. Conservationists are now facing the task of halting deforestation and providing enough space for animals and plants so that they can at least move uphill.