front cover of Land Bridges
Land Bridges
Ancient Environments, Plant Migrations, and New World Connections
Alan Graham
University of Chicago Press, 2018
Land bridges are the causeways of biodiversity. When they form, organisms are introduced into a new patchwork of species and habitats, forever altering the ecosystems into which they flow; and when land bridges disappear or fracture, organisms are separated into reproductively isolated populations that can evolve independently. More than this, land bridges play a role in determining global climates through changes to moisture and heat transport and are also essential factors in the development of biogeographic patterns across geographically remote regions.

In this book, paleobotanist Alan Graham traces the formation and disruption of key New World land bridges and describes the biotic, climatic, and biogeographic ramifications of these land masses’ changing formations over time. Looking at five land bridges, he explores their present geographic setting and climate, modern vegetation, indigenous peoples (with special attention to their impact on past and present vegetation), and geologic history. From the great Panamanian isthmus to the boreal connections across the North Atlantic and North Pacific Oceans that allowed exchange of organisms between North America, Europe, and Asia, Graham’s sweeping, one-hundred-million-year history offers new insight into the forces that shaped the life and land of the New World.
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front cover of A Natural History of the New World
A Natural History of the New World
The Ecology and Evolution of Plants in the Americas
Alan Graham
University of Chicago Press, 2010

The paleoecological history of the Americas is as complex as the region is broad: stretching from the Arctic Circle to Tierra del Fuego, the New World features some of the most extraordinary vegetation on the planet. But until now it has lacked a complete natural history. Alan Graham remedies that with A Natural History of the New World. With plants as his scientific muse, Graham traces the evolution of ecosystems, beginning in the Late Cretaceous period (about 100 million years ago) and ending in the present, charting their responses to changes in geology and climate.

            By highlighting plant communities’ roles in the environmental history of the Americas, Graham offers an overdue balance to natural histories that focus exclusively on animals. Plants are important in evolution’s splendid drama. Not only are they conspicuous and conveniently stationary components of the Earth’s ecosystems, but their extensive fossil record allows for a thorough reconstruction of the planet’s paleoenvironments. What’s more, plants provide oxygen, function as food and fuel, and provide habitat and shelter; in short, theirs is a history that can speak to many other areas of evolution.

A Natural History of the New World is an ambitious and unprecedented synthesis written by one of the world’s leading scholars of botany and geology. 

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