Since the middle of the 20th ...

Since the middle of the 20th century, more has been learnt about the ocean than during all preceding human history; at the same time, more has been lost.
 Sylvia Earle

Quotes from the same author

By the end of the 20th century, up to 90 percent of the sharks, tuna, swordfish, marlins, groupers, turtles, whales, and many other large creatures that prospered in the Gulf for millions of years had been depleted by overfishing.
 Sylvia Earle
The end of commercial fishing is predicted long before the middle of the 21st century.
 Sylvia Earle
Humans are the only creatures with the ability to dive deep in the sea, fly high in the sky, send instant messages around the globe, reflect on the past, assess the present and imagine the future.
 Sylvia Earle
I hope that someday we will find evidence that there is intelligent life among humans on this planet.
 Sylvia Earle
My first breath was just...it just seemed impossible that you could actually breathe underwater. I knew in my mind it was possible, but actually experiencing it was such a gulp of joy and I feel it every time I go under the ocean. I love doing it, to be able to feel weightless, to spin on one finger, to do somersaults, to be like a graceful ballerina - even with a huge tank on your back you can do the most extraordinary things.
 Sylvia Earle