- Big cats play a pivotal role in the survival of ecosystem that they inhabit.

Taking them out of the ecosystem will cause an imbalance.

They will not keep the prey in check, and it would upset the balance of nature.

- Each species is affected slightly differently.

There are several hundred thousand leopards, we believe, which is much more than you would expect.

The most concern at the moment, lions and cheetahs.

Lion population has dropped, I think it's 75% in the last 50 years alone.

And cheetahs are down to just seven or so thousand individuals on the continent.

- Arguably the most iconic, charismatic predator on the planet.

We shouldn't ever envisage a future without them in the wild.

We need to do everything that we can to protect them.

(animal roaring) (birds squawking) (lion roars) - When it comes to understanding big cats, we need long-term data, and we can link that back to trends in flooding, changes in climate, changes in prey availability.

And that's really important from a conservation perspective 'cause if we can understand the natural drivers of populations, then we know how best to conserve them.

- All of these cats need sort of the freedom of movement.

So as places are fenced and restrict the movement of prey, that has an impact.

I think people would be surprised to learn, you know, that there aren't that many truly wild places left.

- [Narrator] As the number of people has grown across our planet, we've come into closer proximity with wild spaces.

This has put the future of many species at risk.

- I think that lions are a lot more threatened than people realize.

You have maybe 20,000 lions left in Africa.

- We are the problem that lions face.

It could be human-wildlife conflict.

It could be climate change.

It could be loss of habitat.

It could be poaching.

But it comes back to the same thing.

Human beings, we're the common denominator in the demise of this species.

- A lot of the lions who disperse out of their prides are going out into the far reaches on the borders with communities and settlements, and they are falling victim to conflict with humans.

Fortunately, we've got about 16,000 square kilometers of Okavango to work with for the big cats.

- [Narrator] There's relatively little impact from humans in the Okavango Delta, which has allowed the region's lions to thrive.

- We've created a safe haven, the Okavango Delta, where we have got multiple prides living the same way they did hundreds of years ago.

- That's what makes the Okavango such a precious place because this is genuinely one of the last strongholds of this species.

- I like to term it as an ark of life.

It's one of these small places that has a healthy enough population that can feed into all the other areas surrounding it.

- [Robynne] There's a really good number of lions here that enables the whole system to be self-sustaining, and that's really rare throughout Africa because most populations are too small, which is why connectivity between different protected areas is really important.

- The Okavango is linked to a huge swathe of Africa that is as natural as we've got left.

We've got the biggest area of protected and semi-protected land on the continent surrounding the Okavango.

- [Narrator] One big cat in particular relies on having large protected areas like this one, the cheetah.

- They can cover huge distances as part of a home range, and within that space, they need enough prey.

So the biggest challenge for them is human encroachment on their habitats.

They're not great with disturbance from people.

It affects their reproductive success.

- [Narrator] So while cheetahs lucky enough to be in the protected Okavango are doing well, that's not necessarily the case for cheetahs elsewhere.

But there is another species that has proven surprisingly resilient in the delta and the changing world beyond.

- Leopards are one of the more successful of all big cats.

They are able to adapt.

I think a lot of it pays to their intelligence.

They also have a huge variety of prey species that they can rely on.

- They can eat anything from an insect to a wildebeest, so they can deal with the changes in Africa a little bit better than lions and cheetahs.

- [Narrator] As the habitats they call home continue to change, the futures of these three big cats hang in the balance.

- It's easy to be pessimistic, but there is sort of, there is hope there because there is this desire for cheetahs, leopards, lions to be part of this world, not in zoos, but in wild places.

And there are amazing people working towards that.

There's a lot of African communities that want to protect the lions, the cheetahs, the leopards that they live alongside.

- I think one of the most important things that will really improve the future for lions is for us to support the local communities that live alongside them.

And we need to be innovative in finding solutions to allow people and lions to coexist within the same landscape.

- The continuous survival of big cats for me means a lot.

I would personally love to one day show my kids big cats that are living in a safe paradise, such as this one in the Okavango Delta.

- I believe all of our wildlife here should be protected.

We need to keep on creating safe areas for our animals, such as the Okavango Delta.

- The fight's not over, and as long as there are a lot of people passionate and fighting for it, then we stand a chance.