Seasick: Ocean Change and the Extinction of Life on Earth by Alanna Mitchell. University of Chicago Press, Chicago, 2009; 161 pages, ISBN 978-0-226-53258-5, hardback, $25.00.The ocean is so vast that it has long been taken for granted that it can absorb any human insult, whether pollution and nuclear waste or overfishing. Yet scientific evidence is revealing that human activity is having an alarming impact on the seas. Science journalist Alanna Mitchell travels the world to speak with experts on this frontier of knowledge, producing a fascinating read that is a wakeup call to change. She accompanies researchers to the large dead spot in the Caribbean, caused by runoff of artificial fertilizers into the Mississippi. The number of these areas without oxygen and unable to support any life have been doubling every decade since the 1960s, so that there are now about 500 worldwide. She visits the Great Barrier Reef and coral reefs in the Caribbean, learning about the factors that have destroyed one quarter of the world's reefs and left another quarter struggling. The ocean's ecosystem, comprising 99% of living space on earth, is more delicate and interconnected than formerly believed, as she discovers from scientists concerned with biodiversity, overfishing, and the seas' metabolism and fertility. Each stop adds substance and urgency to the conclusion that the present combination of technology, ignorance, and scale of human activity, if unchecked, is likely to lead to a major extinction of ocean life.
Few realize how vital ocean health is to life on land. Climate is largely determined by ocean temperature and currents, as El Nino and La Nina remind us. Half of atmospheric oxygen is produced by plankton, one-celled organisms living in the top portions of the ocean. One third of the carbon released into the atmosphere is absorbed by the ocean. This comes at a cost, however. The excess carbon in the air, largely from fossil fuels, cement making, and cutting down trees, is changing the pH of the ocean, making it more acidic than it has been in tens of millions of years. Because pH is measured on a logarithmic scale where each unit is ten times that of the one before, changes that sound small are actually large. For example, the human blood must stay between a pH of 7.35 and 7.45 to maintain health and life. The changes in ocean pH have already dropped by a wider range than this. Growing acidity will kill off tiny organisms and small fish that make their shells and bones from calcium, organisms that form the base of the sea food chain.
Today, the concentration of carbon dioxide in the atmosphere is about 387 parts per million by volume. Before the industrial ear it was 280 parts per million. The latest intergovermental panel report on climate change has predicted that once the level reaches 450, possibly by midcentury, humans will have pushed roughly a quarter of the planet's creatures into extinction. If it reaches 550 parts per million – about double preindustrial levels – we will have caused the genetic extermination of up to 70 percent of living things. Such a massive spasm of extinctions would not be without precedent, but we know of just five others in the planet's 4.5 billion-year history. – pp. 9-10Since global carbon emissions were more than a third higher in 2006 than in 1990, this remains an uncontrolled problem. Unlike global warming, the causes of which often appears ambiguous in the popular press, worrisome changes in the ocean are undeniably the result of human decisions and can only be prevented by new human attitudes and actions.
The author concludes by asking what story we'll tell ourselves in response to these facts, and how will it affect us. Will it make us despair, go into denial, or beat ourselves up? Or will it make us take action?
The story we tell matters because it alone determines the actions we take or fail to take. In other words, the final vital sign, the one that will fix the fate of the global ocean, is how the agent of destruction – us – reacts. Will we turn the destruction off? Will we bring on our own destruction so that the earth can survive? Will we continue to attack the organism of the earth, pushing it into a new system that will be unlikely to harbor us?
. . . The future is in our hands. It strikes me as critically important that we understand this. – p. 134
This is a persuasive book that allows cutting-edge scientists to speak
for themselves. And ultimately it is a hopeful one because it provides,
explains, and gives a human context to the information needed for
intelligent choices that have huge consequences. – Sally Dougherty (December 2009)