The world’s oceans cover 140 million square miles and have remained stable for most of human history. But in the last 30 years, man’s impact on the seas has taken a heavy toll: global fish supplies are declining thanks to new technologies and overfishing. Climate change has led to a rise in ocean temperatures and the loss of 75 percent of large sea animals. Plastics and agricultural fertilizers are polluting our oceans and killing marine life. On this month’s Environmental Outlook: How humans are harming the world’s oceans and what can be done about it.
A recent survey of California beaches found 140,000 bits of plastic trash for every 100 yards of beach. Marine scientist and conservationist Callum Roberts discussed water pollution, climate change, overfishing and other human impacts on the seas in his new book, "The Ocean of Life." In it, he traced the origin of the world’s oceans and proposed a new deal for oceans that aims to establish marine reserves.
More Fish In the Sea
Roberts said there’s a false assumption that there will always be more fish in the sea. He said fish are the perfect renewable resource if you take less than is being produced, but the amount of fish dwindles over time if more is taken than is produced. He said this is what’s happening now, in a form of exploitation called serial over-fishing. Once a species has been depleted, we move on to something else, which is why we eat more squid and lobster today even though these species were used as bait 50 years ago.
Early Humans Ate Seafood
Roberts said humans are creatures of the sea, and that the building blocks of human nervous systems come from omega-3 fatty acids found in marine life. Humans owe their large brain size, cleverness and heart health to a diet that’s rich in seafood. Roberts said some of the earliest evidence of modern humans comes from South African coastal caves, where they gathered and ate lots of shellfish.
History Of Fishing
Fishing is one of the earliest ways that humans affected the seas, Roberts said. Commercial fisheries first developed in the Mediterranean, evidenced by a type of canned tuna that shipped around the Black Sea five millennia ago. “Five thousand years ago, just think that people were packing amphorae with fish and then shipping them hundreds or even thousands of miles. That's quite extraordinary,” Roberts said. Roberts attributed the industrialization of fishing to the invention of boat engines in the late 19th century. He said sea ports were full of engine-powered vessels, which meant boats could drag bigger fishing gears. “We could get out further and faster. We could bring back fresh fish from further afield. We could go deeper down in the oceans,” Roberts said. Later, the invention of flash freezing allowed people to go further offshore and preserve more types of fish.
Despite improved fishing technology, the life of a fisherman has become more difficult. “The paradox of improving technology is that it's always chasing a dwindling prize,” Roberts said. As the ability to catch fish improves, the amount of fish that can be caught declines. About two-thirds of fish species have collapsed since the 1950s, such as the Atlantic Blue Fin Tuna, and the rate is accelerating.
You can read the full transcript here.
Excerpt from "The Ocean of Life" by Callum Roberts. Copyright 2012 by Callum Roberts. Reprinted here by permission of Viking Books. All rights reserved.
Appendix from "The Ocean of Life" by Callum Roberts. Copyright 2012 by Callum Roberts. Reprinted here by permission of Viking Books. All rights reserved.