Prehistoric Garbage Piles Created "Tree Islands" 111
sciencehabit writes "Piles of garbage left by humans thousands of years ago may have helped form 'tree islands' in the Florida Everglades--patches of relatively high and dry ground that rise from the wetlands. They stand between 1 and 2 meters higher than the surrounding landscape, can cover 100 acres or more, and host two to three times the number of species living in the surrounding marsh. Besides providing habitat for innumerable birds, the islands offer refuge for animals such as alligators and the Florida panther during flood season. The trash piles—a mix of discarded food, charcoal, shell tools, and broken pottery—would have been slightly higher and drier than the surrounding marsh, offering a foothold for trees, shrubs, and other vegetation."
Re:Correlation is not causation (Score:4, Interesting)
The rubbish in this situation was
a mix of discarded food, charcoal, shell tools, and broken pottery
While of course people do not likely live on top of their trash, lack of motorised transport means that trash likely wasn't moved far away. Especially charcoal which can be re-used as fuel. Broken pottery well from daily accidents. Shell tools just left behind. Discarded food smells and attracts predators so that one is something they would likely try to at least take to the perimeter of their settlement.
So indeed I think it's likely a combination: dryer patches where humans started to live, making the patches even dryer with their activities. And considering we're talking humans here, I wouldn't be surprised if those activities were intentional. Like bringing in rocks or soil, or even deliberately keeping their broken pottery as foundation, to make the area better to live on. Maybe they were involved in agriculture already? The article indeed mentions that in some cases there was clear evidence of trees and shrubs growing at that place before the arrival of the human settlers.
cause/effect? (Score:4, Interesting)
It seems like they simply found middens with some regularity deep in/on these tree islands.
Therefore one scientist contends that some of the islands may have grown from middens. Isn't it substantially more plausible that primitive humans, who generally tend to want to stand/sit/live on dry ground, would have sought out these relatively isolated (and thus somewhat safer) locations for habitation? That the middens are found deep in the islands only seems to me to mean that this - the value of a secure home - was even obvious to primitive humans?
One comment in the article bothered me: "The authors say the findings show that human disturbance of the environment doesn't always have a negative consequence." That seems...a rather insipid comment.
We're still doing it (Score:4, Interesting)
By far the highest points in south Florida are its landfills; see, for example, this beauty [google.com] on Florida's Turnpike in Deerfield Beach. When global warming floods the area in [insert date of your choice here], these landfills will become tree islands in the new Everglades.