The oceans have changed more in the past 30 years than in all of human history. In many places, more than 75% of marine megafauna has been lost, and almost nowhere shallower than 3,000 feet has been untouched by commercial fishing.
These are just some of the stark facts presented by Callum Roberts, professor at the University of York and member of the Save Our Seas Foundation Science and Conservation Advisory Panel, in a new book titled The Ocean of Life. In an excerpt published this week in Newsweek, Roberts describes the extent to which we have impacted the oceans through overfishing and CO2 emissions, painting a disheartening picture of the future in store for over 70% of our planet if we don’t change course.
On the subject of ocean acidification, he writes:
The oceans have absorbed around 30 percent of the carbon dioxide released by human activity since pre-industrial times, mainly from fossil-fuel burning, conversion of forests and swamp to cities and agriculture, and cement production. If carbon-dioxide emissions are not curtailed, ocean acidity is expected to rise 150 percent by 2050, the fastest rate of increase at any time in at least the last 20 million years and probably as long as 65 million years, which takes us back to the age of dinosaurs. As Carol Turley, an expert on ocean acidification from Plymouth Marine Laboratory put it, “the present increase in ocean acidity is not just unprecedented in our lifetimes, it is a rare event in the history of the planet.”
As a consequence of rising ocean temperatures and acidity, combined with a massive decrease in the numbers of predatory fish, many parts of the world are seeing an explosion of "slime" – jellyfish, microbes and algae:
Jellyfish, for example, are great opportunists, and some scientists fear that large parts of our most productive seas will transform into jellyfish empires. Jellyfish positively thrive in pollution-enriched seas. Given unlimited food, they can reach adult size fast. With their stinging tentacles, they are formidable predators. Here one of the quirks of ocean food webs comes into play to seal their dominance. Most animals that might eat jellyfish go through tiny egg, larval, or juvenile stages when the tables turn and they are themselves jellyfish prey. Such role reversals of predator and prey are rare on land. In the sea, however, they are prevalent, with surprising effects. The American oceanographer Andrew Bakun invites us to imagine a world in which zebras and antelopes are voracious predators of young of lions or cheetahs. What would the Serengeti look like if this were so?
In the face of such gloomy facts, what can we do? Professor Roberts stresses that there are dietary choices individuals can make that, on a worldwide scale, can positively impact the future of the oceans:
The full article is available here, and the book goes on sale later this month.