The number of people in the US who believe the planet is warming has in the last two years fallen from 77% to 57%, according to a recent survey. [photojournalists Mathias] Braschler says this level of denial shows how far removed many urbanites have become from communities who still live close to the land, such as the Inuvialuit hunters of northern Canada or the traditional farmers in Chad. "These people share an ability that most people in western societies have lost: they are able to observe changes in nature," he said. "They are like the canary in the coal mine. Their observations are early warning signs and should be taken seriously. Soon these changes will affect all of our lives. Global warming is a real threat. And we should do something about it."