Bristlecone pine. View of a bristlecone pine Pinus aristata. This remarkable species lives at an altitude of 2100 to 3600 metres, and is one of the longest-living organisms on Earth. Some specimens have been estimated as nearly 5000 years old. Studies of wood from Bristlecone trees has given much data on ancient climates. Whilst studying the Bristlecone, researchers discovered that climates more than 3600 years ago had a different carbon dioxide content, leading to a revision of the ages derived from Carbon-14 dating. Photographed in California, USA.