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While we’ve driven many to extinction, to others we’ve brought absurd levels of global success. We think of eucalyptus trees as native to Australia, but they were rare there when humans showed up forty-five thousand years ago. Our use of fire to clear other species helped these fire-resistant trees eventually thrive and spread throughout that continent. When I first visited Northern California, I assumed that eucalyptuses were native there, as they so dominate the forested hills. Yet they were introduced only during the gold rush, in the 1850s, when they were thought to be a promising source of timber for railroad ties. They turned out to be lousy for that purpose, but they took well to the dry, sunny hills, where they displaced many native trees. They are now regarded as an invasive species and, ironically, given their history in Australia,
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