Florida Tree Islands are Ancient Middens

Again we are continuing todevelop evidence of extensive human settlement throughout semi tropical Florida.  This was effectively confirmed by theearliest post Columbian penetration of these lands but those exploratory forayswere exploratory at best.  Thus we havescant information as indigenous populations promptly collapsed. 

Archeology is now establishingthe existence of uplifted midden based platforms that acted as likely townsites.  Obviously waste was tossed ontothe edges of the camps and the platforms grew steadily over thousands of years.

It is reasonable to presume thatshellfish was consumed daily by everyone as that was the local staple incoastal waters.  In fact, these localeswere well nigh impenetrable for anything but canoes and thus land game waslikely a rarity.  Thus fish and shellfishmust be consumed. 

As we know on the West coast,such a system can support huge populations were shell fish and salmon providedsustenance for communities of even ten thousand and produce huge middens.

Now we know were the hugepopulations in Floridaactually lived.

Ancient Trash Heaps Gave Rise To Everglades Tree Islands

by Staff Writers

Santa Fe NM(SPX) Mar 23, 2011

Garbage mounds left by prehistoric humans might have driven the formation ofmany of the Florida Everglades' tree islands, distinctive havens of exceptionalecological richness in the sprawling marsh that are threatened by humandevelopment.

Tree islands are patches of relatively high and dry ground that dot themarshes 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 treeislands (a larger type of tree island frequently found in the Everglades' mainchannel, Shark River Slough)developed on protrusions from the rocky layer of a mineral called carbonatethat sits beneath the marsh. Now, new research indicates that the real triggerfor island development might have been middens, or trash piles left behind fromhuman settlements that date to about 5,000 years ago.

These middens, a mixture of bones, food discards, charcoal, and humanartifacts (such as clay pots and shell tools), would have provided an elevatedarea, drier than the surrounding marsh, allowing trees and other vegetation togrow. Bones also leaked phosphorus, a nutrient for plants that is otherwisescarce in the Everglades.

"This goes to show that human disturbance in the environmentdoesn't always have a negative consequence," says Gail Chmura, apaleoecologist at McGill University in MontrealCanada, and one of the authors of the study.

Chmura will be presenting her research tomorrow, Tuesday 22 March, atthe American Geophysical Union's Chapman Conference on Climates, PastLandscapes, and Civilizations. About 95 scientists have converged on Santa Fe this week todiscuss the latest research findings from archeology, paleoclimatology,paleoecology, and other fields that reveal how changes in regional and globalclimate have impacted the development and fates of societies.

In a previous scientific investigation of tree islands, MargoSchwadron, an archeologist with the National Park Service,cut through the elevated bedrock at the base of two islands and discovered thatit was actually a so-called "perched carbonate layer," because therewas more soil and a midden below. Later, a team including Chmura's graduatestudent Maria-Theresia Graf performed additional excavations in South Florida and found more of the perched carbonatelayers.

Chemical analysis of samples of these curious perched layers revealedthat they are made up partially of carbonates that had dissolved from thebedrock below, Chmura says. The layer also contains phosphorus from dissolvedbones, she adds. Her team concluded that trees are key to the formation of thislayer: During South Florida's dry season,their roots draw in large quantities of ground water but allow the phosphatesand carbonates dissolved in it to seep out and coalesce into the stone-likelayer.

The perched carbonate plays a key role in letting tree islands reboundafter fires: because it does not burn, it protects the underlying soil, and itmaintains 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 highwater levels year-round in some water control systems, which could cause thelayer to dissolve.

Chmura's team now wants to explore exactly when trees started growingon the tree islands

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