In the past decade, scientists who study the movement of animals have found that of the four thousand species that they’d tracked, between 40 and 70 percent had altered their distribution. On average, terrestrial creatures are moving nearly twenty kilometers every decade. Marine creatures, who are largely free of barriers to seeking cooler waters, are moving four times faster than land-based animals. Some animals are making spectacular leaps. Scientists estimate that Atlantic cod are moving north at a rate of a hundred miles per decade. In the Andes, frogs and fungi species have climbed four
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