Susan Casey, THE UNDERWORLD: JOURNEYS TO THE DEPTHS OF THE OCEAN

 5 stars

This is a nonfiction account of the author's journeys with explorers venturing into the deepest parts of the ocean in submersibles. With engaging anecdotes from others as well as her own experiences, Casey writes in an accessible, familiar way, leaning into her own wonder and into the natural suspense of these adventures, with machines that have systems that fail sometimes, when they are miles below the surface. (There's an account of being in a submersible, on the ocean floor, with water leaking in and another with the batteries failing...!) I appreciated the history, including how "nature-crazed Victorian England ... was enthralled by any aquatic discovery." I also enjoyed the color photographs [in the hardback edition] of the bizarre lifeforms in the deep ocean -- some of them truly otherworldly. James Cameron and his fascination with the Titanic appears as an interesting side story. The most significant part of the book, however -- a ball that doesn't really get rolling until later -- is the significance of the ocean for the climate of our planet and the dangers we face if we don't protect it. "It's the engine that runs the climate system." For example, "Since 1970, it has gulped down 93 percent of the excess heat and 30 percent of the carbon dioxide we've generated from burning fossil fuels." What is scary is that there are groups increasingly determined to mine the deep -- scrape the bottom for the nuggets of minerals on the ocean floor -- a process that will disturb the ecosystems for thousands of square miles, rendering them uninhabitable and disturbing their ability to sink carbon and regulate temperature for us. There is a group called the ISA -- International Seabed Authority -- with 168 member nations -- that is ostensibly independent and supposed to evaluate mining contracts for their environmental impact. But the ISA seems to have cozied up to metal companies, granting 31 mining exploration contracts covering seabed the size of Alaska. (They have never turned down a proposal.) The other scary thing is plastics. There are amphipods that have plastic microfibers embedded in its guts. "Along with microplastics and synthetic fibers, scientists have found that the hadal trenches are thick with every toxin we've ever unleashed -- PCBs (industrial poisons), PBDEs (flame retardants), DDT, ... lead, mercury, pharmaceutical waste, and radioactive carbon from nuclear bombs. Form the ocean's surface to its deepest sediments, all the way up the marine food chain, we have left our mark." I'd recommend to anyone who wants to understand the role of the oceans in our world. [Read for bookclub.]