Excavations show the role early humans played in forming the tree islands that dot the river of grass.
Dotting the landscape of Everglades National Park are teardrop-shaped elevations of hardwood trees (or hammocks) named, “tree islands.” The significance of tree islands as the only dry ground has long been acknowledged, but their significance also lies beneath the earth, as archeological findings from a dig in 2010 present data that prehistoric humans played a significant role in the formation of tree islands, and in turn, the archeological discoveries should be considered in current Everglades restoration models.
“Tree islands are the nucleus of the Everglades,” said Traci Ardren, chair and professor of anthropology at the University of Miami’s College of Arts and Sciences. “They are rich habitats for plants, birds, and other animals and provide higher ground and stability for the Everglades drainage system.”
Ardren says Everglades restoration models used by scientists and government entities do not take human factors into account, specifically prehistoric human occupation.
“This research provides an example of how humans were involved in the way tree islands were formed, so if we want to have the best models we can for Everglades restoration, we need first to understand the original formation of tree islands,” she said.
Ardren’s research, entitled “Prehistoric human impact on tree island lifecycles in the Florida Everglades,” was published in the journal The Holocene and illustrates the archeological discoveries from a tree island known as the Booth site. There are currently hundreds of archeological sites in the Everglades, and almost every tree island has evidence of prehistoric human occupation; unfortunately, most tree islands have not been archeologically investigated.
In 1998, a team visited the Booth site and uncovered archeological artifacts of pre-Columbian human occupation, but according to Ardren, the research was minimal. When she and her team visited the site in 2010, there was extensive digging and richer analysis of the findings. “The activities on the site were not that different from the 1998 visit, but it was more about the conclusions we drew from the data collected,” she added.
Overall, archeological research in the Everglades is very minimal due to the belief that the terrain is very challenging; these perceptions may contribute to the lack of archeological research and excavation.
“We do not think of the Everglades as a place where there were people living for thousands of years,” Ardren explains.
“Tree islands in the Everglades certainly present a nutrient anomaly in the otherwise oligotrophic wetland. Currently, there are three major hypotheses explaining this nutrient enrichment: nutrient enrichment via plant transpiration; bird guano as birds nest in the islands; and pre-Columbian human occupation,” said Cooper Fellow and Professor of Biology Leonel Sternberg. “Indeed, there is evidence for all three factors and Dr. Ardren’s research points out that these hypotheses are not mutually exclusive, and they all could be part of the explanation why tree islands are nutrient sinks.”
Ardren says the main point of her research is to contribute quantifiable data on the human influence in tree island formation, which is a major factor ignored in most Everglades restoration research and models. She hopes her research will generate discussion among scientists today who are working on Everglades restoration in many disciplines with the outcome to collaborate and take into account the human impact on the landscape, not just in the 21st century but thousands of years into the past.