“We’ve not just ruined the planet, we’ve destroyed it.”

Sir David Attenborough has seen a lot over the course of his 93 years on the planet. The beloved English broadcaster and natural historian has traveled to every continent and witnessed the natural world in all of its glory. In a new documentary, he’s using his experience to send a wake-up call about the future we face if we don’t make some serious changes. Because, as Attenborough so directly puts it, “human beings have overrun the world.”

Why is this a problem? As David Attenborough: A Life on Our Planet so clearly shows, human domination of Earth has led to some considerable issues. In this new human-led era, the Anthropocene, Attenborough has seen firsthand the impact we’ve made on nature. And unfortunately, it’s not all positive.

“We learnt how to tame the wild. Get more from the environment. Our population boomed, as did our demands,” Attenborough narrated in a separate Netflix documentary, Our Planet. “Every time a new problem arose we solved it, altering Earth’s entire surface in the process. The tables have turned. We now determine nature’s survival. We’re now totally out of balance with nature and unless we get our balance back, this age of humans is due to be short-lived.”

Attenborough began working with the BBC in the 1950s and just twenty years later, he was already starting to see some of the negative impacts our actions were having on wildlife. He recalls returning to Rwanda in the 1970s to a declining population of mountain gorillas and having to be escorted by park rangers to avoid poachers. It was a drastic change from his carefree earlier years of travel—when wilderness was truly wild.

Now, he’s very blunt in his view of the state of the planet. “We’ve not just ruined the planet, we’ve destroyed it,” he told New Scientist.

“Our planet is becoming less wild. Our species has cleared 3 trillion trees, cultivated half its fertile land and now fishes across most of the ocean,” he revealed in Our Planet. “In the last 50 years, the populations of wild animals have reduced by 60%. We’ve replaced them with ourselves and our domesticated animals and plants. Today, we and the animals we raise account for 96% of the mass of mammals and 70% of the birds on Earth. There’s very little wild left. This biodiversity loss is not just a tragedy, it’s the single biggest problem we face.”

Luckily, the documentary, which traces the famed naturalist’s life from childhood, should be the call to action we all need. With Attenborough’s reputation behind it, there’s hope that the message will get through. And though he feels that Earth is currently in disrepair, there is still hope.

Read More: Sir David Attenborough Documentary Addresses Environmental Issues