Sir David Attenborough will front a new natural history documentary for Netflix, in the latest example of the streaming company muscling in on the BBC’s territory.

The 92-year-old broadcaster has been synonymous with the BBC’s natural history output for decades but will now provide the voiceover for Netflix’s eight-part series Our Planet, which will be released in April.

“Our Planet will take viewers on a spectacular journey of discovery showcasing the beauty and fragility of our natural world,” Attenborough said as the series was announced on Thursday. “Today we have become the greatest threat to the health of our home but there’s still time for us to address the challenges we’ve created if we act now. We need the world to pay attention.”

The programme is produced by Alastair Fothergill and Keith Scholey, who have previously worked with Attenborough on BBC projects such as Planet Earth and Blue Planet. Unusually, their Netflix series has been produced in collaboration with the World Wide Fund for Nature (WWF), which helped gain access to filming locations and provided advice.

The WWF’s Colin Butfield, who served as an executive producer on the project, said: “I’ve never seen a natural history series that combines real stuff you’ve never seen before but that always has a really, really great narrative in each episode. It’s not at all preachy, it’s spectacular mass public entertainment, but by the end you are absolutely aware of the challenge of climate change and overfishing and deforestation.”

Our Planet was initially announced without Attenborough’s involvement in 2015 and the team have spent four years filming in 50 countries around the world, with more 600 members of crew.

Last year the BBC aired Blue Planet II, fronted by Attenborough. It was the year’s most-watched TV show in the UK and became a global success, and it prompted a reappraisal of the impact of plastic use on the oceans.

Butfield said Netflix would make Our Planet available on the same day around the world – something that is impossible to achieve with traditional TV channels – in an attempt to influence governments. The series will be available only to paying subscribers.

“I can’t think of a better platform that will reach that many people at the same time,” he said. “For this particular one it’s all about having that global moment. It’s hard to get a programme on lots of national broadcasters at the same time. Whether it’s London or Delhi or Rio or Washington, we want it out at exactly the same time.”

He said other material produced alongside each episode would be made freely available online. “Our motive is educational and [improving] public understanding of the natural world. [It] is telling a much bigger, deeper story about the state of the planet and how nature can recover.”

Our Planet represents an enormous financial investment for Netflix, given the substantial cost of producing natural history films. The BBC has teamed up with TV channels around the world to share production costs, although it is likely to find itself battling with deep-pocketed online rivals for future series.

Attenborough is not cutting his ties with the BBC, and his new five-part series Dynasties, for which he was involved in on-location filming, will begin on BBC One this Sunday.