Together they've brought us unforgettable series including The Blue Planet, Planet Earth and Frozen Planet.
Now, stunning images in their latest venture, Our Planet, show never before seen environmental change and animal behaviour.
Our Planet took four years to make with a worldwide cast of 600 crew working in 50 countries.
It has an optimistic message with stories demonstrating nature's resilience and possibilities for restoration - that it's not too late to protect the planet.
Fothergill told Lynn Freeman that the natural world is in a much more precarious state than when he started working with Attenborough for the BBC 35 years ago.
“There's a real job just to explain to people what's out there and what's precious, and also the value of it, why it's so important. When I started making wildlife films nature was a nice to have and I think what we realise now is it's a must have, and it's a must have for our own survival, for the health of our own planet.”
The programme was a huge logistical undertaking, he says.
“We spent a record 3,500 days in the field to make this series which means for every minute that you see in the final show, we spent 10 days in the field.”
Improved technology allowed them to capture never before seen images, it was shot in 4K, twice the resolution of HD, he says.
This improved technology allowed them to capture footage of polar bears and Siberian tigers that wouldn’t have been previously possible, he says.
“I'm very passionate about polar bears, an amazing animal, the Inuit name for a polar bear is the wanderer, because it's an animal that's always on the move. And we decided that we needed to photograph them in a different way.
“We wanted to take the camera off a tripod, the normal sort of static way of filming animals, and mount a special gyro stabilised camera on a snow machine.”
This meant they could track alongside the polar bears, but from a distance that wouldn’t disturb them, he says.
Another hard-won sequence was of Siberian tigers of which there are only 600 left.
“We had three cameramen locked in hides, special wooden hides to protect them from the tigers frankly, and they didn't get out of those hides at all for six weeks. They did that over two winters and they didn't film a single frame of tiger footage. They heard them roaring at night, but they never saw them in front of the hides.
“Luckily, we'd mounted around 40 or 50 motion control remote cameras in the forest. In the first year again, we didn't get any images, but the second year, we began to understand where the tigers were moving, and we captured just 37 images of Siberian tigers.
“Those were very, very precious shots very, very hard-won.”
A section in the programme on forests shows both bad and good news. In one sequence shot in Madagascar, Attenborough’s voiceover explains that forest where they were filming is now gone.
Only three percent of Madagascar’s native forest remains, he says.
“Madagascar is home to the lemurs and a lot of other amazing endemic species found nowhere else on Earth. So it's a very important story to tell.”
However, the forest episode ends with filming in Chernobyl which is now a green oasis, he says.
“The forest has reclaimed Chernobyl, and we deliberately ended that show with that story to explain that forests are very resilient, they really can bounce back.
“Using those same motion control cameras that we filmed the Siberian tiger, we caught images of wolves, and wolves are apex predators, you know that if there's healthy population of wolves, there's a healthy population of wildlife beneath it.”
He says there is now a greater density of wolves in the Chernobyl exclusion zone than anywhere else in eastern Europe.
The production crew captured some extraordinary footage by using drones, which are now able to carry high-definition cameras, Fothergill says.
“They were particularly useful in the open ocean because if you go out into the Big Blue, looking for some of the amazing events that happen out there, they tend to be very ephemeral, they’re very unpredictable, you don't know where they're going to happen and often they'll all be over in 20 minutes or 30 minutes.”
Drones allowed the crew to respond quickly, he says.
“A drone can take off in a couple of minutes and that caught some wonderful action. It caught bluefin tuna attacking anchovies and you have to look at look down on it from the air to really understand what's going on.
“Some of my most favourite images in the whole series is of a blue whale mother with a new born calf. And the drone is literally 50 meters above her, but she is utterly, utterly relaxed. She really has no sense of the drone being there at all. It’s the most intimate image I've ever seen of a blue whale mother and her calf.”
Netflix gave them the time and resources they needed to make Our Planet, Fothergill says.
“They said they’d leave us alone to do it and they did. I think the one massive advantage that Netflix provided this series was on April the fifth it was in 190 countries on the same day, 150 million subscribers, and it's there forever.
"I've done some fantastic work with the BBC, and I'm still delighted to work with them. But they have more complex deals around the world. It'll come out in the UK one month, it may come out in France two months later, it may come out come out in New Zealand three months after that. And in this day and age, the ability to communicate globally at once was amazing. The other great thing about the Netflix audience is they are young, the average age of Netflix viewers is substantially lower than certainly the BBC audience here in the UK.”
Fothergill says despite the multiple threats facing the natural world, he remains optimistic we can turn back from the destructive path we are on.
"If anybody thinks the planet isn't under enormous threat they're not being honest with themselves. But I have faith in humanity, I genuinely do. I think the human species is the most intelligent, the most ingenious species on the planet.
"We have the technology today to solve the problems, we just need the political will to do it.
"But also, I have enormous faith in nature.”
One of the sequences in Our Planet of which he is most proud was filmed off the coast of South Africa.
“It's the largest aggregation of humpback whales ever filmed, over 250 humpback whales feeding together. Now, even three or four years ago, you never could have filmed that spectacle. It just simply wasn't happening. And you know, back in the 1980, we had almost driven all the great whales to extinction.
“In 1986, the world got together and banned commercial whaling. And now just over 30 years later, there are more humpback whales in the ocean than before commercial whaling started. So that shows, you given the opportunity, nature can bounce back. So yeah, I am optimistic.”