Nine kilometres beneath the sea off the coast of Japan, there are fields of yellow flowers that stretch for hundreds of miles. They are not real flowers – not even plants at all but animals called crinoids, related to sea urchins and starfish, which anchor themselves to the deep seabed and feed off plankton filtered by their delicate frond-like arms.
The cliche that we know more about the surface of the moon than about our own oceans is given vivid new currency in this blend of natural history, popular science, travelogue and ecocriticism by the Australian novelist and poet James Bradley. The book takes us from pole to pole and surface to bottom of the blue realm that covers most of Earth.
For the majority of the planet’s biosphere, including some of its most sophisticated minds (whales, dolphins, octopuses), all our land-borne empires and terrains are irrelevant. Forests, mountains, rivers, sky, rain count for next to nothing; they have their own versions, such as the crinoid meadows, soaring subsea peaks and valleys, and the ocean currents that bear vast quantities of heat and nutrients around the world. Even gravity means rather little when you live forever in deep water, and some species dwell where sunlight never reaches.
We have little notion of the scope of evolution’s inventiveness while we remain so ignorant about the oceans. Only there can we find creatures comparable to the first animals that ever existed. Sponges, comb jellies and cnidarians (which include jellyfish) reveal what the earliest multicellular organisms from before the Cambrian explosion about 540m years ago would have been like. The portuguese man o’war is not the jellyfish it appears to be but is a colony of tiny creatures called zooids. Corals are the archetypal symbionts: small animals that coexist with photosynthetising microorganisms. And there are sea anemones on the vast abyssal plains beneath the Pacific that appear to live alone, a hundred miles from their nearest neighbour. How such a dispersed population is even viable remains puzzling.
The tiny crustacean known as the Antarctic krill is the most populous wild animal on the planet, its total biomass amounting to several hundred million tonnes. It is the linchpin of ecosystems that support penguins, seals and whales. Yet we don’t even know where it migrates to when the polar sea ice expands in winter. At the other end of the scale, of course, are the great whales, which can communicate through sound over thousands of miles – or could, before human marine activities cluttered up the acoustic environment with noise.
Bradley Vividly conveys the awe-inspiring scale of the deep seas, both in space and time. They constitute the most capacious environment on the planet: close to 90% of the livable space, and host to 95% of the biosphere. Their lowest point is the Mariana Trench, almost 11km down in the western Pacific where two tectonic plates converge. The intense pressures at such depths make exploration challenging and – if done by humans – risky.
Yet these abysses, far too deep for light to penetrate, host oases of biodiversity. At hydrothermal vents – discovered by submersible missions in the 1970s – the heat and nutrients carried by waters that pass through volcanic fissures support communities of tube worms and other organisms. It’s widely thought that life on Earth might have begun here, sheltered from the torrid conditions at the planet’s surface, well before any microbe learned to harness the energy of the sun.
Evolved for life on land, we are nevertheless dependent on the ocean. More than three billion people, says Bradley, derive their livelihood from it. And that’s the root of all manner of problems, both for us and for the marine ecosystems. Deep Water is often painful to read; each account of a wonder is followed by a description of how we are despoiling it. The magical portrait of bioluminescence with which the book opens – waves spilling pale blue light on to an Australian beach at night, thanks to the microorganisms called noctiluca that glow when squeezed by fluid flow – becomes an ominous fable about how ocean warming is causing blooms where they never used to be, as well as creating toxic “red tides” that turn the waters the colour of rust and kill fish.
Ocean travel enabled humans to learn the extent and diversity of our planet, but exploration was accompanied by exploitation of people and of resources. Our webs of commerce are now totally dependent on seaborne cargo: shipping accounts for nearly 3% of global greenhouse gas emissions. One of the book’s saddest chapters describes the inundation of the remote Cocos Islands by pieces of plastic. That is just the latest episode in the abject history of these atolls in the Indian Ocean, visited and admired by Charles Darwin but run by descendants of a Scottish merchant as a feudal colony until the 1970s.
The litany of destruction and violence at sea is shocking. There may be less than a tenth as many fish as there were a century ago, and savage conditions on some vessels rival the slavery and piracy of three centuries ago. Indeed, genuine slavery and human trafficking are rife in some parts of the global fishing industry, where ever-declining catches breed desperate measures. The current rate of rise in global average temperature, however troubling, only disguises how much worse the situation is at the poles, raising the prospect of a catastrophic collapse of the Antarctic or Greenland ice sheets. Human-induced ocean warming is devastating coral reefs – and as one researcher warns, in previous mass extinctions “coral reefs are always the first to go. And then everything else follows.”
Bradley seeks beacons of hope, interviewing engineers, conservationists, scientists and campaigners who are looking for ways to reverse these damaging trends. Some are developing alternative fuels for shipping, or even promoting a return to sail power via hi-tech clippers that make use of new materials or “Flettner rotors” spun by wind. Marine biologists are seeking to identify or create heat-tolerant corals to repopulate reefs. But the scale of these challenges seems overwhelming, and earnest efforts can end up as tokenistic PR. “Fossil fuel companies love coral-reef restoration,” one researcher tells him, “because they can use it in their greenwashing campaigns.”
“We now live in an Age of Emergency that will not end in my lifetime,” Bradley writes. While the crisis seems beyond comprehension, he adds, “the ocean provides a way of thinking about these questions”. Not only does it reveal the dangers, but it also delivers a sorely needed reminder that “the world still hums with beauty and astonishment”. Deep Water joins two other recent and splendid books, Helen Czerski’s Blue Machine and Olive Heffernan’s The High Seas, in both celebrating our blue planet and highlighting the perils it faces as a result of our own greed and ignorance.
• How Life Works: A User’s Guide to the New Biology by Philip Ball is published by Picador. Deep Water: The World in the Ocean, by James Bradley, is published by Scribe (£22) on 28 March. To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply.
