Foremost among Attenborough's TV documentary work as writer and presenter is the "Life" series, which begins with the trilogy: Life on Earth (1979), The Living Planet (1984) and The Trials of Life (1990). These examine the world's organisms from the viewpoints of taxonomy, ecology and stages of life respectively.They were followed by more specialised surveys: Life in the Freezer (about Antarctica; 1993), The Private Life of Plants (1995), The Life of Birds (1998), The Life of Mammals (2002) and Life in the Undergrowth (2005). The most recent, Life in Cold Blood (dealing with reptiles and amphibians), is currently being broadcast on BBC One. The 'Life' series as a whole comprises 79 programmes.Attenborough has also written and/or presented other shorter productions. One of the first after his return to programme-making was The Tribal Eye (1975), which enabled him to expand on his interest in tribal art. Others include The First Eden (1987), about man's relationship with the natural habitats of the Mediterranean, and Lost Worlds, Vanished Lives (1989), which demonstrated Attenborough's passion for discovering fossils. In 2000, State of the Planet examined the environmental crisis that threatens the ecology of the Earth. The naturalist also narrated two other significant series: The Blue Planet (2001) and Planet Earth (2006). The latter is the first natural history series to be made entirely in high-definition.In May–June 2006, the BBC broadcast a major two-part environmental documentary as part of its "Climate Chaos" season of programmes on global warming. In Are We Changing Planet Earth? and Can We Save Planet Earth?, Attenborough investigated the subject and put forward some potential solutions. He returned to the locations of some of his past productions and discovered the effect that climate change has had on them.In 2007, Attenborough presented "Sharing Planet Earth", the first programme in a series of documentaries entitled Saving Planet Earth. Again he used footage from his previous series to illustrate the impact that mankind has had on the planet. "Sharing Planet Earth" was broadcast on 24 June 2007Life in Cold Blood is Attenborough's last major series. In an interview to promote it, he stated:The evolutionary history is finished. The endeavour is complete. If you'd asked me 20 years ago whether we'd be attempting such a mammoth task, I'd have said 'Don't be ridiculous'. These programmes tell a particular story and I'm sure others will come along and tell it much better than I did, but I do hope that if people watch it in 50 years' time, it will still have something to say about the world we live in.However, in subsequent interviews with Radio Times, Parkinson and on Friday Night with Jonathan Ross, he said that he did not intend to retire completely and would probably continue to make occasional one-off programmes. In 2008, he stated that he is planning a series about Charles Darwin and evolution.