London – David Attenborough, a leading voice on climate change and biodiversity loss whose landmark documentaries transformed popular understanding of the natural world for a global audience, marks his 100th birthday on Friday. Attenborough's natural history series, such as "Life on Earth," in which he had a famous encounter with mountain gorillas in Rwanda, have brought the most remote corners of the planet into living rooms worldwide. "He's taken us all to places that we would never otherwise go. That's a huge gift," said botanist Sandra Knapp, director of research at London's Natural History Museum. The BBC is leading the celebration of the Briton's centenary with a full week of programming dedicated to his life. Classic episodes of series including "Planet Earth II" and "Blue Planet II" are being reshown along with others such as "Life in the Freezer" and "Paradise Birds" available on the BBC's iPlayer service.…