To conclude its groundbreaking and visually arresting nature series "Planet Earth II," the BBC trained its cameras not on some wild vista, but on the top of the Shard skyscraper in London. There, perched high above the urban landscape, Sir David Attenborough delivered a stirring message to the millions of viewers watching throughout Europe.

“Only a small number of animals have managed to find ways of living alongside us,” said Attenborough during the series finale dedicated to the impact of urban environments on species. “And every 10 years, an area the size of Britain disappears under a jungle of concrete. But it doesn’t have to be like this. Could it not be possible to build cities more in harmony with nature?”

Attenborough, 91, is making his appeal at a time when the technosphere, the whole of humanity's manufactured impact on the planet, is growing at a incredible rate. In addition, our global population continues to climb, with the number of people on the planet expected to top 11.2 billion by 2100. As you might expect, Earth's biodiversity is suffering. A recent WWF report estimated an average annual decline of 2 percent in the number of mammals, birds, reptiles, amphibians and fish left living in the wild.

"Now over half of us live in an urban environment," Attenborough continued. "My home too is here in the city of London. It’s also sobering. It reminds me of just how easy it is for us to lose our connection with the natural world."

That connection, he added, will make all the difference in determining the future fate of all species. "It’s surely our responsibility to do everything within our power to create a planet that provides a home not just for us, but for all life on Earth."

It's a moving plea –– and likely one that Attenborough knows he won't get too many more chances to deliver to such a widespread audience. After more than 50 years of promoting the natural world like no one else, it's unclear how many more specials will benefit from what many have dubbed "the official voice of Mother Nature." Like the very species he's trying to protect, Attenborough himself is a unique cultural treasure.

"We love working with Sir David, and I think he loves working with us, and we want that to last as long as possible," Mike Gunton, producer for "Planet Earth II," told The Star. "When he decides he doesn't want to do it any more, we will have to rethink how we make these programs."

Added Gunton: "You can't replace him — it's pointless trying."

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.