Updated: 19 Dec 2020, 7:49 15 IF there is anyone who knows what it takes to beat the threat of extinction, it’s Sir David Attenborough. But while some campaigners, such as militant animal rights group PETA, have branded zoos “pitiful prisons”, the TV legend has a different view. 15 Sir David Attenborough has worked to save numerous species, but it's not just the animal kingdom he fears being wiped outCredit: BBC 15 15 Now it has almost tripled to 7.8billion - leading Sir David to warn of a 'real crisis'Credit: BBC Having witnessed the planet’s most extraordinary animals thriving in their natural habitats, the 94-year-old deems some zoos essential for certain species to survive.