Magazine contents note: "The English colonists who landed at Jamestown 400 years ago undermined an ecosystem and changed the continent forever."
Key paragraphs: "It is just possible that John Rolfe was responsible for the worms--specifically the common night crawler and the red marsh worm, creatures that did not exist in the Americas before Columbus. Rolfe was a colonist in Jamestown, Virginia, the first successful English colony in North America. Most people know him today, if they know him at all, as the man who married Pocahontas. A few history buffs understand that Rolfe was one of the primary forces behind Jamestown's eventual success. The worms hint at a third, still more important role: Rolfe inadvertently helped unleash a convulsive change in the American landscape."
"[Rolfe traded in tobacco.] Ships bellied up to Jamestown and loaded up with barrels of tobacco leaves. To balance the weight, sailors dumped out ballast, most stones and soil. That dirt almost certainly contained English earthworms. And little worms can trigger big changes. The hardwood forests of New England and the upper Midwest, for instance, have no native earthworms--they were apparently wiped out in the last Ice Age. In such worm-free woodlands, leaf litter piles up in drifts on the forest floor.
"But when earthworms are introduced, they can do away with the litter in a few months. The problem is that northern trees and shrubs beneath the forest canopy depend on that litter for food. Without it, water leaches away nutrients formerly stored in the litter. The forst becomes more open and dry, losing much of its understory, including tree seedlings.
"Whether the night crawler and the red marsh worm actually first arrived on Rolfe's tobacco ships is not known. What is clear is that much of the northern forests in America were worm free until the Europeans arrived there, inadvertently importing earthworms on the root-balls of their plants or in the ballast of ships. The effects of this earthworm invasion have been slow to show themselves because the creatures don't spread rapidly on their own. 'If they're born in your backyard, they'll stay inside the fence their whole lives,' says John Reynolds, editor of Megadrilogica, the premier earthworm journal. But over time, the effect on the ecosystem can be dramatic."
"Two hundred and fifty million years ago the world contained a single landmass known to scientists as Pangaea. Geologic forces broke this vast expanse into pieces, sundering Eurasia and the Americas. Over time the two halves of the world developed wildly different suites of plants and animals. Columbus' signal accomplishment was, in the phrase of historian Alfred Crosby, to reknit the torn seams of Pangaea. After 1492, the world's ecosystems collided and mixed as European vessels carried thousands of species to new homes across the oceans. The Columbian exchange, as Crosby called it, is why there are tomatoes in Italy, oranges in Florida, chocolates in Switzerland, and hot peppers in Thailand. It is arguably the most important event in the history of life since the death of the dinosaurs."