The ugly origins of Florida's beautiful, mysterious tree islands

Many have marveled at the strange beauty of the tiny "tree islands" of the Florida everglades. How did they get there? Why do such small piles of land manage to sustain such healthy trees? Today, McGill paleoecologist Gail Chmura answered that question. Her research suggests strongly that the trees were originally trash mounds left by native tribes thousands of years ago.

A release about Chmura's work, which she'll present tomorrow at the American Geophysical Union's Chapman Conference on Climates, Past Landscapes, and Civilizations, explains:

Scientists have thought for many years that the so-called fixed tree islands (a larger type of tree island frequently found in the Everglades' main channel, Shark River Slough) developed on protrusions from the rocky layer of a mineral called carbonate that sits beneath the marsh. Now, new research indicates that the real trigger for island development might have been middens, or trash piles left behind from human settlements that date to about 5,000 years ago.

These middens, a mixture of bones, food discards, charcoal, and human artifacts (such as clay pots and shell tools), would have provided an elevated area, drier than the surrounding marsh, allowing trees and other vegetation to grow. Bones also leaked phosphorus, a nutrient for plants that is otherwise scarce in the Everglades.

"This goes to show that human disturbance in the environment doesn't always have a negative consequence," says Chmura.

The question now is just what humans of the future will find growing from our garbage piles full of circuit boards, CRT monitors and batteries. Learn more on the Geophysical Union conference website.

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