Our Oceans Are In Trouble:

What is the state of the ocean today?

It's actually very bad. It's probably worse in many ways than the state of conservation on land, but we don't think about it because we don't live in it.

Basically it comes down to what we put into the atmosphere and ocean and what we take out of the ocean. What we put into the atmosphere is carbon dioxide, which makes the ocean hotter. And when it dissolves in the oceans themselves, it makes them more acidic. From the land, you're getting all this runoff into the oceans—vast amounts of nutrients associated with excess fertilizer, pesticides, industrial waste, waste from cars and city streets. There's a lot of stuff that fertilizes the ocean and causes bacteria and other slimy stuff to proliferate, plus things that actually poison the ocean.

We also have the massive scale of fisheries. We're pulling out the tops of the food chain. Most of the big fish in the ocean are already gone. We've also strip-mined the bottom of the sea floor with trawls.We've basically created a massive disturbance to the ocean, which is resulting in collapsing ecosystems, failing fisheries, toxic blooms.

When did scientists realize the damage we're causing the ocean?

In the last 50 years, things have really deteriorated. People have had some impact for a long time, but the ocean can suffer a certain amount of assault from human activity and not have a major problem with it. Now everything is increasing. Carbon dioxide is increasing dramatically. Industrial fisheries, since about the 1950s, have increased dramatically.