Some of the most memorable, appalling statistics in history are those of the accidental genocides wrought by human exploration. After its introduction to Central America by the conquistadors in 1520, for example, smallpox had by 1527 killed millions in Mexico and precipitated the collapse of the Inca empire. The same disease, introduced by Europeans to north America, killed 90% of the Massachusetts Bay Indians between 1617 and 1619. By the end of the 18th century, European diseases—of which smallpox was the worst—had managed to kill 90-95% of the native population of the Americas (Roy Foster gives a brief, haunting account of this process in the first section of his masterpiece, The Greatest Benefit to Mankind).
In the 10th December edition of The New Yorker, there's a piece by the writer Richard Preston, "A Death in the Forest," that describes something alarmingly similar currently taking place in the plant kingdom. Preston focuses on the plight of the eastern hemlock, a tree native to north America, which is now threatened by the spread of an Asian insect known as the hemlock woolly adelgid. Just like humans, plants have evolved immune mechanisms that protect them from pests and infections; and, just like humans, plants are almost totally unprotected by these mechanisms against threats that are "exotic"—that come from distant places with which, until recently, they had no possibility of contact.
We've all heard about this kind of thing before, but the examples Preston produces—combined with the quality of his expert, restrained, appalled narrative—prove truly astonishing. Since 1904, the fungal disease chestnut blight has killed almost every American chestnut tree. Since the 1930s, the American elm has virtually disappeared thanks to an Asian fungus and a European beetle. Sudden oak death disease has now killed hundreds of thousands of oaks in California, and may soon reach eastern oaks. The American beech has lately been dying in its tens of thousands due to a European fungus, while the arrival of an Asian beetle in packing wood from China in 2001 has begun to devastate a number of species of American ash. The sugar maple could also be almost wiped out by the invasion of the Asian long-horned beetle. And the list goes on.
What can we do? Preston lists measures that can be taken for individual trees, but acknowledges that little so far has stopped the waves of dying, and he closes with an account that has an air of horrible historical familiarity—a few people, belatedly, picking up the pieces and trying to preserve the memory of what has been lost:
When it became apparent that the eastern hemlock might nearly cease to exist, Blozan [president of the Eastern Native Tree Society] and his partners founded the Tsuga Search Project, an effort to identify and measure the world's tallest and largest eastern hemlocks before they were gone… In the Cataloochee Valley, Blozan walked into groves where he found what had been the world's tallest hemlocks. They were already dead, but he climbed the skeletons and measured them anyway. "The data are for someone someday," he said.
