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.