31 March 2011

The genesis of Everglades "tree islands"

As reported by the Vancouver Sun:

Canadian researchers have solved a long-standing mystery about the existence of "tree islands" in the Florida Everglades — rare heights of dry, semi-forested land that serve as nesting sites for alligators, refuges for endangered panthers and crucial hubs of biodiversity in the world-famous swamp. A McGill University-led study of the islands reached an unexpected conclusion: these life-sustaining sources of nutrients for one of America's iconic ecosystems originated thousands of years ago as the trash heaps of prehistoric people who lived around present-day Miami...

Chmura, a McGill geography professor and director of Quebec's six-university Global Environmental and Climate Change Centre, told Postmedia News that the islands appear to have begun as aboriginal middens — dumping grounds for bones, shells, charcoal, food waste and other discarded material that gradually built up over generations into permanent mounds of earth...

Scientists had previously theorized that the islands were formed on top of "perched" layers of a naturally occurring mineral called carbonate that underlies the Everglades. But excavations by the McGill researchers and others showed the prehistoric garbage dumps appeared to kick-start the process of carbonate accumulation that was deepened and hardened as tree roots repeatedly drew up groundwater and dissolved minerals.


  1. As a Miamian, I thank you very much for this post. :)

  2. Interesting article. Thanks for sharing it.

  3. This reminds me of the "islands" in the Lousiana bayous, such as "Avery Island" from whence comes Tabasco.

    Avery Island, though, is a source of both oil and salt. It is over a salt dome and was one of the early sites for oil exploration.

    O.T. comment:
    The thinking was for a long time that salt domes are the only way oil accumulates deep in the ground. That is still the way it is taught, from what I gather, that the oil creeps upward until some impervious layer catches it, like in an inverted lake. However, they have found oil in all kinds of underground formations. Scientist Thomas Gold of abiogenic/abiotic oil fame even told them they would find oil under a granite shield in Norway - about the last place the reigning theory would expect to find oil - and he was right. As to abiogenic oil, I think he is right, but I don't think it replenishes by that means as fast as we use it, so if he was right, then we would run out eventually, anyway.


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