By Ray Grigg
When we think about environmentalism, we tend not to consider the oceans because we don’t live on or in them, and they are just there as they have always been, defining the edge of the land that we occupy. Of course, oceans provide us with most of our fish, but in the popular understanding, they are mostly experienced as vast spaces of waves and wet that separate the faraway continents that we visit. So we tend to give much more importance to landscapes that we occupy. And because we live within the thin layer of air that girdles the globe, weather is also a concern to us. But we generally don’t consider that much of our climate and weather is determined by what happens in the oceans.
Maybe our interest in oceans can be encouraged by the perspective provided by the book review of James Bradley’s Deep Water (Philip Ball, The Guardian Weekly, 15 March 2024). Maybe it’s the significance of the world’s oceans in the environmental issues that makes his subject particularly arresting. Or maybe it’s the dark and watery mysteriousness of the oceans that attract our attention because of the little we actually know about them. But Bradley gives us a context to raise our awareness and to elevate the relevance and importance of our oceans to our planet’s history, to its ecology, and to our future.
As Bradley points out, 70% of our planet is covered by oceans. Its deepest point is the Marianna Trench, which is 11 km below the surface, and everywhere between the ocean’s floor and its surface teems with life. Consequently, 90% of the liveable space on Earth is ocean, and it constitutes 95% of the biosphere that sustains life. This is something that we forget when we think of ecology.
Oceans were the source of life on our planet. With the exception of a few species of air-breathing mammals that made the return trip back to the oceans, most species live where they originated. So the oceans contain a cornucopia of animals, plants, and exotic combinations that represent the entire history of evolutionary life on Earth. It is our planet’s largest store of biological treasures, mysteries and wonders.
Bradley describes hundreds of kilometres of seafloor off the coast of Japan that are covered with yellow flowers—not flowers at all, but crinoids, plankton filter-feeders related to sea urchins that anchor themselves to the bottom in uncountable numbers. He explains that the Portuguese man o’war is not a sea-jelly at all, but “a colony of tiny creatures called zooids.” He draws our attention to the little crustacean known as Antarctic krill, the most abundant animal on the planet. Its total biomass totals “several hundred million tonnes”, and its numbers are so huge that this single species supports everything from the smallest of fish to the greatest of whales.
As for us, Bradley points out, about 3 billion people depend on the oceans for their livelihood. But, he estimates, the world’s oceans only contain about 10% of the fish that they did a century ago. In addition to our unsustainable pillaging of this resource, we have been treating the oceans as a sewer for our wastes. Plastics now pollute the once pristine water and beaches in the most remote places, and can now be found in the flesh of most fish—and commonly found in human blood, organs and fetuses, too. Our toxins are now ubiquitous in the oceans. Our marine commerce is responsible for about 3% of our greenhouse gas emissions, about the same amount emitted by airplane traffic.
Most alarming, however, and mostly unrecognized, is that nearly 95% of the planetary heating produced by our emissions of carbon dioxide is transferred to the oceans—a cubic metre of ocean absorbs 2,100 times more heat than a cubic metre of air. Without the oceans, we would have cooked ourselves off the surface of the planet decades ago. The top 700 metres of the world’s oceans have risen in temperature by nearly 1.0°C in the last century. This rise is expected to continue until at least 2300, notes Professor Matthew England, an oceanographer and climate scientist from the University of New South Wales. As a consequence, there is, and there will be, “sea level rise, coastal inundation, increased floods and drought cycles, bleached corals, intensification of cyclones, ecological impacts, melting ice at higher latitudes and coastal margins… . The oceans have stored [our emissions] problem, and it’s coming back to bite us.” Nor only do the higher temperatures of oceans contain less dissolved gases such as the oxygen that is required for the vitality and survival of fish, but the stored heat generates extreme weather events.
A significant part, about 30%, of our carbon dioxide emissions do not stay in the atmosphere, but are absorbed by the oceans to form carbonic acid. This acidification lowers the pH of oceans, impairing the ability of marine animals to create the calcium carbonate shells that they need for survival. One of those little animals is the Antarctic krill, not to mention crabs, shrimp, lobsters, coral and all shellfish.
Because of the heat absorption characteristic of the oceans and their propensity to remove carbon dioxide from the air, they have been a shock absorber for the impact that we are having on our planet’s ecosystems. But the shock has not gone away. It has merely been slowed and delayed beyond our immediate notice. These effects are now becoming discernible, and will become more apparent as ocean temperatures rise and as their changing currents alter weather and climate patterns, as fish become less plentiful and viable, as crustacea struggle against acidity, and as rising sea levels continue their unstoppable inundation of our coastal cities. The experiment that we are conducting with our environment is slowly revealing the delayed effects, while saving some of its most sensational surprises for the future.
Ray Grigg for Sierra Quadra
Top image credit: Prophetic words from 70 years ago sadly coming true – Photo by john shortland via Flickr (CC BY 2.0) www.johnshortlandwriter.com