Featured Research

from universities, journals, and other organizations

Ancient human trash heaps gave rise to Everglades tree islands, research suggests

Date:
March 21, 2011
Source:
American Geophysical Union
Summary:
Garbage mounds left by prehistoric humans might have driven the formation of many of the Florida Everglades' tree islands, distinctive havens of exceptional ecological richness in the sprawling marsh that are today threatened by human development.

Everglades National Park Florida USA. Garbage mounds left by prehistoric humans might have driven the formation of many of the Florida Everglades' tree islands, distinctive havens of exceptional ecological richness in the sprawling marsh that are today threatened by human development.
Credit: iStockphoto

Garbage mounds left by prehistoric humans might have driven the formation of many of the Florida Everglades' tree islands, distinctive havens of exceptional ecological richness in the sprawling marsh that are today threatened by human development.

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

These middens, a mixture of bones, food discards, charcoal, and human artifacts (such as clay pots and shell tools), would have provided an elevated area, drier than the surrounding marsh, allowing trees and other vegetation to grow. Bones also leaked phosphorus, a nutrient for plants that is otherwise scarce in the Everglades.

"This goes to show that human disturbance in the environment doesn't always have a negative consequence," says Gail Chmura, a paleoecologist at McGill University in Montreal, Canada, and one of the authors of the study.

Chmura will be presenting her research on March 22, at the American Geophysical Union's Chapman Conference on Climates, Past Landscapes, and Civilizations.

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

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

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

Chmura's team now wants to explore exactly when trees started growing on the tree islands.


Story Source:

The above story is based on materials provided by American Geophysical Union. Note: Materials may be edited for content and length.


Cite This Page:

American Geophysical Union. "Ancient human trash heaps gave rise to Everglades tree islands, research suggests." ScienceDaily. ScienceDaily, 21 March 2011. <www.sciencedaily.com/releases/2011/03/110321134627.htm>.
American Geophysical Union. (2011, March 21). Ancient human trash heaps gave rise to Everglades tree islands, research suggests. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2011/03/110321134627.htm
American Geophysical Union. "Ancient human trash heaps gave rise to Everglades tree islands, research suggests." ScienceDaily. www.sciencedaily.com/releases/2011/03/110321134627.htm (accessed April 23, 2014).

Share This



More Earth & Climate News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

California Drought Is Good News for Gold Prospectors

California Drought Is Good News for Gold Prospectors

AFP (Apr. 22, 2014) — For months California has suffered from a historic drought. The lack of water is worrying for farmers and ranchers, but for gold diggers it’s a stroke of good fortune. With water levels low, normally inaccessible areas are exposed. Duration: 01:57 Video provided by AFP
Powered by NewsLook.com
Raw: MN Lakes Still Frozen Before Fishing Opener

Raw: MN Lakes Still Frozen Before Fishing Opener

AP (Apr. 22, 2014) — With only three weeks until Minnesota's fishing opener, many are wondering if the ice will be gone. Some of the Northland lakes are still covered by up to three feet of ice, causing concern that just like last year, the lakes won't be ready. (April 22) Video provided by AP
Powered by NewsLook.com
Scientists Warn Of Likely El Niño Event This Year

Scientists Warn Of Likely El Niño Event This Year

Newsy (Apr. 22, 2014) — With Pacific ocean water already showing signs of warming, the NOAA says there's about a 66 percent chance the event will begin before November. Video provided by Newsy
Powered by NewsLook.com
Is North Korea Planning Nuclear Test #4?

Is North Korea Planning Nuclear Test #4?

Newsy (Apr. 22, 2014) — South Korean officials say North Korea is preparing to conduct another nuclear test, but is Pyongyang just bluffing this time? Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins