The Emerald Planet: How Plants Changed Earth's History
David Beerling
Language: English
Pages: 312
ISBN: 0199548145
Format: PDF / Kindle (mobi) / ePub
Global warming is contentious and difficult to measure, even among the majority of scientists who agree that it is taking place. Will temperatures rise by 2ºC or 8ºC over the next hundred years? Will sea levels rise by 2 or 30 feet? The only way that we can accurately answer questions like these is by looking into the distant past, for a comparison with the world long before the rise of mankind. We may currently believe that atmospheric shifts, like global warming, result from our impact on the planet, but the earth's atmosphere has been dramatically shifting since its creation. Drawing on evidence from fossil plants and animals, computer models of the atmosphere, and experimental studies, David Beerling reveals the crucial role that plants have played in determining atmospheric change--and hence the conditions on the planet we know today-- something that has often been overlooked amidst the preoccuputations with dinosaur bones and animal fossils. "Beerling uses evidence from the plant fossil record (mutant spores, tree stumps from the Artic and Antarctic, growth rings) to reconstruct past climates and to help explain mass extinctions. Too often this evidence has been disregarded, but Beerling gives it its due, and then some."--BioScience
new possibility: was some feature external to biology—the environment—holding back leaf evolution? New questions open new doors and suddenly cast a diVerent light on the notion that the photosynthetic proWciency of leaves makes their evolution inevitable. Crucial elements of the conceptual framework necessary for a radical rethink began to emerge, with reports showing that a remarkable change in the carbon dioxide content of the ancient atmosphere had taken place between 400 and 350 million years
notoriously capricious—dinosaur fossils are, relatively speaking, rare even in the western interior of North America—allowing one group to argue forcibly for a gradual pattern of die-oV and the other for a sudden extinction.5 The current situation divides the community into a minority of ‘gradualists’ and a majority of ‘suddenists’.6 The big question of what caused the dinosaur extinction still causes sparks to Xy and is Wercely contested; the issue is not easily divorced from the divisive
man-hauling sledges is not the deadweight but the friction between the runners of the sledges and the snow. Just over a week later, ‘Evans collapsed, sick and giddy, unable to walk even by the sledge on ski’.7 He died quietly on 17 February 1912. Over the past three and a half months he had marched a staggering 1200 miles (1930 km). The sad end was in sight for the rest of the party. Steadily dropping temperatures, and Oates’ deteriorating condition, slowed the progress of the other men. By 16 or
Eocene climate puzzle. As evidence of this sort begins to accumulate, greenhouse gases other than carbon dioxide take on an altogether more profound signiWcance for their involvement in producing a warm Eocene climate. By themselves, they are minor agents of warming but collectively they are a more potent climatic force. Not only had their high levels in the atmosphere been diYcult to establish, but when added to the picture they also generated a pattern of warming more consistent with that
Because their biochemical machinery operates most eYciently at high temperatures and in bright sunlight, it conWnes most C4 plants to subtropical climates, where they dominate the grasslands and savannas. Only a single species of tree is known to use C4 photosynthesis, Chamaesyce forbesii, and it occurs on Hawaii, an island where evolutionary pressures are altered by millions of years of isolation. Other than C. forbesii, the closest we have to a C4 tree are a few woody shrubs that approach