A couple of things on which we can all pretty much agree: Sir David Attenborough is a living national treasure, and the BBC Natural History Unit makes some of the world’s greatest TV programmes (the second point is not unrelated to the first). Now Sir David, a beast who is slow to anger and loath to court controversy, has sprung like a mountain lion to attack BBC cuts that could cost the NHU almost a third of its staff. The result could be “very skimpy” programmes. Coming from a man who invented the natural history documentary and once topped a poll asking who was the most trusted figure in Britain, the criticism is damaging to the BBC.

The son of an academic, David Attenborough spent his childhood roaming Leicestershire and beyond in search of fossils, flora and fauna. He read Natural Sciences at Cambridge and joined the BBC in 1952. He made his name with a series about collecting zoo animals. He ranged across the globe, getting into wonderful scrapes and creating his own style of broadcasting. His enthusiastic chats to the camera from exotic locations spawned an entire genre. In the 1960s he was Controller of BBC Two, but returned to making programmes in the 1970s, becoming a global name with the landmark Life on Earth. Life in Cold Blood, which starts next month, will complete his project to make a series about every major group that lives on land.

His brilliance lies in communicating, often breathlessly, his boundless enthusiasm for the wonders of nature. No one who has seen his peaceful encounter with mountain gorillas will forget it. The same goes for the times he was chased off by an elephant seal and a displaying capercaillie. It took him a while to become convinced that man was responsible for climate change, saying: “If you’ve got any degree of authority, you have to be very, very sure.” Last year he presented programmes on the subject. He is sounding off in a way he avoided when he was younger.

His wife, Jane, died of a cerebral haemorrhage in 1997 after 47 years of marriage. “Life’s different. Your days are different, your conversation’s different, what you eat is different. You can’t go back so you get on with it,” he has said of that time. His daughter Susan runs his affairs. His son Robert, an anthropologist, lives in Australia with Sir David’s two grandchildren. At 81, he has said Life in Cold Blood is his last big series. But he will continue to make programmes and is working on a project about Darwin.

There was a kerfuffle recently over a sequence in the new series in which he encounters a Mozambique spitting cobra on a desert rock. The snake, it transpires, was taken from captivity and put on the rock. Sir David defended the action, saying it would have been “a great misuse of licence payers’ money wandering around just hoping I was going to come across a spitting cobra”. He, more than anyone, knows how much more thinly that money must now be spread.

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010