The Sixth Extinction: Chapter 7

     In Chapter 7, Kolbert talks about the research station in One Tree Island where teams of scientists from around the world study the chemical composition of coral reefs. She then talks about the history of the Great Reef Barrier and its first explorer Captain James Cook. Cook had never seen a coral reef before and didn’t understand how it was formed. Sixty years later, Lyell came up with the theory that reefs grew from the rims of extinct underwater volcanoes. Darwin then visited a coral reef in Tahiti, and concluded that a large reef that became submerged in water due to rising sea levels. Scientists now know that coral reefs are part animal/vegetable/mineral and contain many calcifying creatures. The reefs grow over time, but they grow by adding new life forms to their composition, rather than ending them. Kolbert meets Ken Caldeira, a researcher who studies the impact of CO2 on ocean ph levels, and takes her on a diving expedition to photograph octopi. She then goes on to explain how CO2 could destroy reefs. The Biosphere project was a glass structure designed to be a self-sustaining ecosystem, however it failed because the high CO2 levels caused altitude sickness. Scientists concluded many things after this. The high carbon dioxide levels eroded the composition of coral inside the Biosphere, challenging that coral reefs are immune to changes in carbon dioxide levels. Scientists also concluded that the reefs will disappear at a quick rate because of he rising temperature. Warm water threatens coral reefs by increasing the amount of algae and plankton in the ecosystem, which decreases the food available for larger coral species.

     The theme that most resonated with this chapter is biogeochemical systems vary in ability to recover from disturbances. The coral reef is essentially a biogeochemical system and throughout history, has been affected by CO2 levels. In the book it states, “Yet curiously enough, the first evidence that CO2 could kill a reef came from...the self-enclosed, supposedly self-sufficient world known as Biosphere 2...Oxygen levels inside the building fell sharply, and the Biospherians developed what amounted to altitude sickness, Carbon dioxide levels, meanwhile, soared.” (Pg. 135) (R) As CO2 in the ocean increases, ocean acidification occurs and corals can’t absorb the calcium carbonate they need to maintain their skeletons, which causes them to dissolve. Because of this it becomes even harder for the reefs to evolve and to follow their paradigms. It also becomes impossible for them to establish new paradigms, because as the reefs die out and new ones form, it becomes hard to adjust to the soaring levels, especially for the remaining reefs. (C) This also connects to the theme of the previous chapter because us humans are producing fossil fuels at an increasing constant rate, and with ocean acidification, it kills most of the fishes, which is food supply for humans. And with it impacting the reef it’s preventing the reefs from doing their job. Coral reefs provide a buffer to  protect our coasts from waves, storms, and floods and they form barriers to protect the shoreline from waves and storms. The coral reef structure also buffers shorelines against waves, storms, and floods, helping to prevent loss of life, property damage, and erosion.

By: Mousumi Dhar