One example of a climate change-related forest pathogen is the Swiss needle cast, a fungal foliar disease that is affecting Douglas fir in the Pacific Northwest. Stone and his colleagues eventually concluded that the pathogen that had always been present at low levels in the Pacific Northwest had turned into a full-blown disease outbreak. The fungus, which slowly strangles trees, is, according to Stone, now present in half a million hectares of Oregon's stands of Douglas fir, 160,000 hectares of which are severely affected.