Searching for the World’s Last Pristine Seas | Nat Geo Live

We have taken fish out of the ocean faster than they can reproduce. Ninety percent of the large fish, like the tuna and the sharks, are gone. And we killed them in the last 100 years alone. Right now about a third of the fisheries of the world have collapsed. If we continue like this, before 2080 most of the fisheries of the world will have collapsed.

Not only do we take fish out of the ocean faster than they can reproduce, but we are doing it in a very destructive way. These are trawlers, shrimp trawlers, in the South China Sea. You can see their tracks from a satellite photo. In some places, for every pound of shrimp that is caught, ten pounds of other animals, including fish, starfish or corals, are killed and discarded overboard.

And on top of that, we have pollution, and now, every year, eight million tons of plastic enters the ocean. And on top of that we have climate change, global warming, which is making the ocean warmer and more acidic, which is killing coral reefs everywhere. This used to be a coral reef now this is a ghost of a coral reef, dead broken coral overgrown by seaweed and slime.

So, in 2008, I moved to Washington, and we started by asking questions. The main question was: "Are there pristine places left in the ocean?" So, we found this place in the middle of the Pacific Ocean. The Line Islands. Seven of these islands are uninhabited. And off we went for five weeks to places like this. Millennium Atoll. This is the size of Manhattan, that belongs to Kiribati. And as soon as we jump in the water, this is what we see. Not only we saw healthy reefs, but lots of predators. Lots of predators. (audience laughter) You know, you jump in the water and as soon as your bubbles clear, you are surrounded by 10-12 sharks.

If you go to the African plains, to the Serengeti, you know, you would expect to see hundreds of thousands of wildebeest, and zebras, and antelopes, and all the animals that eat the grass. The herbivores. And then just a few thousand or a few hundred lions, right? This is what we thought would happen on the reef. This is what we learned in school. This is what we found in textbooks.

But when we went to a pristine reef for the first time, we discovered then what we thought was natural was not. That biomass pyramid is upside down. You go to one of these pristine reefs and more than half of most of the biomass, more than half of the biomass of fish, is accounted for by the top predators. The big guys on top of the food chain.

But then we went to a reef with 5,000 people nearby and this is what we saw. Dead coral, no fish. Only 5,000 people were able to do this. Now, the question now is: "How many people are enough to turn something pristine into something that is not?" So, we decided to go to a place with less people and test that question. So, we went to the most extreme place. Pitcairn Island. Fifty-two people live on Pitcairn Island. It belongs to the UK.

Pitcairn is inhabited by 52 people. The other three islands are uninhabited. We jump in the water and... the visibility was extraordinary, but there are no fish. There were some fish but no sharks, no groupers, no snappers. And then, we had to do it. We had to go to these places without people and see what we find. So, we went to places like this. Henderson Atoll. And we jump in the water and the coral reefs were really, really, really healthy. Spectacular... And of course, lots of sharks. The same thing we found on the Line Islands we found here.

This inverted biomass pyramid. The place where the predators dominate. So, there you go, that was our question answered. Even 52 people, a population as small as 52, are able, over time, using just traditional fishing methods are enough to turn something pristine into something that is not. The corals were fine, they didn't have the impact that the 5,000 Polynesians had on that reef, but they were able to remove, over time, all these large fish that previously inhabited the reef.