Under a Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us about Our Futureby Peter D. Ward
More than 200 million years ago, a cataclysmic event known as the Permian extinction destroyed more than 90% of all species and nearly 97% of all living things. Its origins have long been a puzzle for paleontologists, and during the 1990s and the early part of this century a great battle was fought between those who thought that death had come from above and those
More than 200 million years ago, a cataclysmic event known as the Permian extinction destroyed more than 90% of all species and nearly 97% of all living things. Its origins have long been a puzzle for paleontologists, and during the 1990s and the early part of this century a great battle was fought between those who thought that death had come from above and those who thought something more complicated was at work.
Paleontologist Peter D. Ward, fresh from helping prove that an asteroid had killed the dinosaurs, turned to the Permian problem, and he has come to a stunning conclusion. In his investigations of the fates of several groups of mollusks during those extinctions and others, he discovered that the near-total devastation at the end of the Permian was caused by rising levels of carbon dioxide leading to climate change. But it's not the heat (nor the humidity) that's directly responsible for the extinctions, and the story of the discovery of what is responsible makes for an fascinating, globe-spanning adventure.
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Under a Green Sky
Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future
Welcome to the Revolution!
Zumaya, Spain, July 1982
A warm but wet wind from the sea, a wind pushing gray scudding clouds onshore from the squall-torn Bay of Biscay greeted the two geologists as they slowly drove through the narrow, building-lined streets of a small, tiled Basque town named Zumaya, in the quiet of an early Sunday morning. Their knees were still cramped from the daylong drive of the day before, when they had crossed the neck of France by a route that began on the sun-kissed Mediterranean coast at Banyuls-sur-Mer in the Languedoc region, then clung to the edges of the rugged Pyrénées Mountains for their entire south to north length before ending late that night at a cavernous and gloomy hotel perched on the stormy Atlantic Ocean coast in the Basque city of San Sebastián, Spain.
One of the two was Jost Wiedmann, a famous German paleontologist from Tübingen University, itself the most famous and storied paleontological center in the world. He had spent his career studying the geological ranges of one particular group of fossils, one of the most celebrated of all fossil groups, the ammonite cephalopods. He practiced the standard methodology of his German predecessors: studying the collection of the fossils from known locations in strata to produce a "biostratigraphy," literally the differentiation of the many great piles of sedimentary or layered rock so prodigiously scattered across Earth's crust. His particular interest was mass extinction, those short-term bioticcatastrophes that were the most dramatic bookmarks in the tables of strata. He had spent much of his fieldwork among the strata of the Cretaceous period making up the fabulously beautiful coastline of France and Spain known as the Basque Country, a place inhabited by a dour race still wishing to be known as a country separate from either France or Spain.
Wiedmann had published widely reports that the ammonites showed no evidence of a rapid extinction but of something quite different. In a number of famous papers that had been published in journals read not just by the small band of professional paleontologists but also by a far wider spectrum of geologists and evolutionary biologists, Wiedmann had presented evidence that the final extinction of the ammonites was the final act of a long, slow diminution of diversity that had lasted more than 20 million years. By the end, almost none were left anyway, making the K-T event (an event straddling the Cretaceous and Tertiary periods) a minor extinction at best—at least for the ammonites.
I was the other member here, at that time a young American from the University of California, Davis, one of the new breed of American scientists who styled themselves as "paleobiologists," not one of the paleontologists of old, in an effort to bring new intellectual vibrancy into the oldest field of Earth science, paleontology, by trying to master two fields, not just one. I had completed two quite different research projects for my still rather newly minted Ph.D., the central goal of which was an attempt to understand how the long-extinct ammonite cephalopods could, after a wildly successful existence on Earth of more than 360 million years, would have gone extinct, while their nearest, lookalike relatives, the still living chambered nautilus, had escaped that fate at the end of the Cretaceous period. I had approached this topic from two different directions, one very nontraditional. The old-school approach was the study of the fossils themselves: anything defective here, any morphology antiquated there, as I examined fossil after fossil over a 20-million-year period prior to their final extinction? Actually, pretty boring work. But the other was a very different approach. Long a deep-water salvage diver of professional skill and experience, I had through chance and fortitude talked my way into a research grant that took me to the one place on Earth where a living nautilus could be actually seen in the wild, the island of New Caledonia, some 700 miles east of the Great Barrier Reef region of Australia. Since that four-month expedition in 1975, I had managed to spend at least a month each year in the water with the wild nautilus and by this time in 1982 had expanded my study area to include Fiji, and I was anticipating with enormous excitement my 1983 field season, already planned for Palau, Micronesia, home to the largest nautiluses (and most beautiful reef walls) in the world. Even the cuttlefish there were giant.
In those years, work with the nautilus was directed by questions that more traditional biologists had never asked of this oldest of cephalopod mollusk, ones that hopefully could shed light on the life span, growth rate, food, and predators of the nautilus that might through inference inform about the ammonites as well, and year by year I arrived in the sunny tropics with better equipment, more grant money, and new ideas and colleagues. But this side of my scientific schizophrenia was increasingly shoving aside geological pursuits, and my presence in Europe in the summer of '82 was not to study fossil ammonites but to look at another living cephalopod that might lend insight into the ammonites, a squidlike animal known as the cuttlefish. This work had drawn me to France, and it was a sheer accident that a chance letter to Wiedmann had led to this invitation to visit one of the few sites on Earth where fossil ammonites could be found in stratigraphic sections with both youngest Cretaceous and oldest Tertiary found in a continuous and well-exposed outcrop.
Wiedmann was definitely old school, a classically trained paleontologist. Sadly enough for the field, by the middle of the twentieth century when Wiedmann had trained in the carnage and chaos of immediate postWorld War II Germany, the discipline of paleontology, once a vibrant and necessary area of science important in the study of evolution, had become a sleepy enclave whose every practitioner could spend an entire career writing detailed monographs about the slight differences to be . . .Under a Green Sky
Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future. Copyright © by Peter Ward. Reprinted by permission of HarperCollins Publishers, Inc. All rights reserved. Available now wherever books are sold.
Meet the Author
Dr. Peter D. Ward is a professor of biology and earth and space sciences at the University of Washington in Seattle. He also serves as an astrobiologist with NASA. Ward is the author of more than a dozen books, including the highly acclaimed Rare Earth: Why Complex Life Is Uncommon in the Universe with Donald Brownlee and Out of Thin Air: Dinosaurs, Birds, and Earth's Ancient Atmosphere.
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The ocean's thermohaline circulation is driven by dense, salty water east of Greenland that then sinks, pulling the Gulf Stream far north and then proceeding on a world-encircling journey. It has been long recognized as the primary cause of Europe's anomalously high temperatures. It is now also generally recognized that the thermohaline circulation is equally important at supplying the ocean's deep waters with oxygen; namely, the ocean conveyor belt mixes the seas vertically, assuring that surface-oxygenated water reaches the deep ocean. Peter Ward has traveled to the ends of the Earth in search of evidence for the causes of several major mass-extinction events - most notably in this text, the K/T (aka K/P, ~65 mya) , the P/T (~251 mya), the T/J (~200 mya), and the P/E (~60 mya) extinctions. Initially, Ward had set out to corroborate Louis and Walter Alvarez's blockbuster hypothesis of 1980 that a meteor/comet impact was responsible for the K/T extinction of the dinosaurs. Most of Under a Green Sky is a personal recounting of Ward's field expeditions. The author does an excellent job conveying the excitement and challenge of fieldwork under sometimes very trying conditions. Ward's humor is flawlessly blended with precise scientific field observations. He contrasts the nature of the K/T boundary extinction with what he found at other major geologic boundaries - namely, that boundaries such as the P/T, T/J and Paleocene/Eocene did not indicate a single, sudden mass extinction of many species from which the world rapidly recovered, but rather a gradual, episodic dying group-by-group ("insults") from which the world often took a long time to recover. Ward concludes that the major extinctions at the end of the Permian, Triassic and Paleocene were in fact due to global warming events brought on by the sudden increase in greenhouse gases whose source was either deep-ocean sediments or volcanic eruptions. The warming, he postulates, triggered an alternative thermohaline ocean circulation pattern which eventually led to a highly stratified ocean with nearly-complete anoxic conditions. These anoxic conditions not only helped to produce an amplified release of greenhouse gases but were also accompanied by the release of toxic amounts of hydrogen sulfide (hence the Green Sky) which contributed to land-based as well as ocean-based extinctions. The gist of Ward's argument is that the current man-induced increase in greenhouse gases may be laying the foundation for a similar catastrophic event in our future. A few technical errors in the book were made all the more annoying because Under a Green Sky is otherwise a free-wheeling discussion not a textbook. For example, Ward mistakenly identifies Milankovitch as a Russian (he was Serbian), invents a new and impossible isotope of He (2He - he meant 4He, the most common earthbound isotope of He) and states, unnecessarily, that sea-level rise over the past century was only 1 centimeter (it was at least 20 centimeters). Under a Green Sky is a valuable contribution to the growing (but often same old story) literature on global climate change. Ward offers a unique, concrete, paleontological, and field-oriented perspective that is often missing from technical global-warming discussions based on laboratory data and modeling. Richard R. Pardi, Environmental Science, William Paterson University