Posted on 03/21/2011 9:35:06 AM PDT by decimon
SANTA FE, N.M. Garbage mounds left by prehistoric humans might have driven the formation of many of the Florida Everglades' tree islands, distinctive havens of exceptional ecological richness in the sprawling marsh that are today threatened by human development.
Tree islands are patches of relatively high and dry ground that dot the marshes of the Everglades. Typically a meter (3.3 feet) or so high, many of them are elevated enough to allow trees to grow. They provide a nesting site for alligators and a refuge for birds, panthers, and other wildlife.
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 Gail Chmura, a paleoecologist at McGill University in Montreal, Canada, and one of the authors of the study.
Chmura will be presenting her research tomorrow, Tuesday 22 March, at the American Geophysical Union's Chapman Conference on Climates, Past Landscapes, and Civilizations. About 95 scientists have converged on Santa Fe this week to discuss the latest research findings from archeology, paleoclimatology, paleoecology, and other fields that reveal how changes in regional and global climate have impacted the development and fates of societies.
In a previous scientific investigation of tree islands, Margo Schwadron, an archeologist with the National Park Service, cut through the elevated bedrock at the base of two islands and discovered that it was actually a so-called "perched carbonate layer," because there was more soil and a midden below. Later, a team including Chmura's graduate student Maria-Theresia Graf performed additional excavations in South Florida and found more of the perched carbonate layers.
Chemical analysis of samples of these curious perched layers revealed that they are made up partially of carbonates that had dissolved from the bedrock below, Chmura says. The layer also contains phosphorus from dissolved bones, she adds. Her team concluded that trees are key to the formation of this layer: During South Florida's dry season, their roots draw in large quantities of ground water but allow the phosphates and carbonates dissolved in it to seep out and coalesce into the stone-like layer.
The perched carbonate plays a key role in letting tree islands rebound after fires: because it does not burn, it protects the underlying soil, and it maintains the islands' elevation, allowing vegetation to regrow after the fire. Humans are now threatening the existence of tree islands, by cutting down trees (whose roots keep the perched layer in place) and artificially maintaining high water levels year-round in some water control systems, which could cause the layer to dissolve.
Chmura's team now wants to explore exactly when trees started growing on the tree islands.
###
Notes for Journalists
This research by Chmura et al. is being presented on Tuesday, 22 March, at the American Geophysical Union's Chapman Conference on Climates, Past Landscapes, and Civilizations.
To read the abstract of this presentation, please use this search engine: http://agu-cc11cp.abstractcentral.com/itin.jsp
Click on Search, type Chmura in the Author/Presenter field and click on the orange Search button at the bottom.
Neither the abstract nor this press release are under embargo.
Contact information for the author: Gail L. Chmura, Telephone: +1 (514)926-6854, Email: gail.chmura@mcgill.ca
Mike
“Idiots planted they to try to drain the everglades.”
How about:
“Government idiots planted them to try to drain the Everglades.”
The aerial seeding of the Everglades with Australian Melaleuuca tree seed WAS a gooberment project.
Typical of Gooberment AgencyPersons, there was a monument to that project in the city of Davie, Fl.
Long gone, vanished into the black hole of revisionist history.
I’m skeptical of this explanation. There’s so many ‘heads’ that I can’t imagine ancient human garbage accounting for them.
The phosphorus could have come from the huge phosphate mines N. W. of Lake Okeechobee and been carried in the aquifer.
I say we evacuate the site and nuke it from orbit. It’s the only way to be sure.
Seriously, if this is true, isn’t an EPA superfund cleanup site warranted?
/sarc
Thanks for not mentioning “ancient” and “mound” together in the same sentence.
“...This goes to show that human disturbance in the environment doesn’t always have a negative consequence...”
-
Stupid statement.
So these mounds, especially there size & proliferation, is the direct result of a concerted effort by our forefathers to crap there way out of the muck & mire of their lives.
They did the same thing with Australian pines in Palm Beach County. Now the taxpayers are paying to have those removed.
Typically, archeologists capture the field and then occupy the language.
Tree Island = Hummock
The thesis is that the hummocks were where humans lived and left trash
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No...this just shows us that trees, like humans, are NOT part of nature.
;-)
These trash heap middens go all the way north up the Everglades tributaries up towards Orlando FL and Shingle Creek. From Northeast of there they are shown again in the St John’s tributaries heading north toward the FL/GA border.
http://www.volusia.org/history/sitemap.jpg
I’ve visited afew of these places, beautiful spots, but I can’t believe the mosquitos didn’t cause endemic tropical diseases in the native population.
Most nutrients are scarce in the Everglades. It's like a desert with water. I don't know why people get all misty eyed about it.
That's their money quote.
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