GAINESVILLE, Florida, September 17, 2002 (ENS) - An extensive, University of Florida led study shows that wildlife that corridors encourage the movement of plants and animals across fragmented landscapes. Fragmented habitats can isolate species, reducing their chances to reproduce and survive. Many communities are beginning to set aside small strips of open space linking larger natural areas in hopes of helping wildlife to survive and thrive.
But ecologists have long debated whether these so called wildlife corridors actually help species, and few studies have provided enough data to help answer the question one way or the other.
A new, multiyear study, covering hundreds of acres, examines two indicators of healthy ecosystems - plant pollination by insects and the dispersal of seeds by birds - and concludes that corridors can encourage species to migrate between islands of intact habitat.
"This is by far the largest experimental look at the effects of corridors that has ever been done," said Josh Tewksbury, a UF postdoctoral associate and lead author of a report on the study scheduled to appear next week in the journal "Proceedings of the National Academy of Sciences.
The researchers mapped out eight similar sites, each measuring about 158 acres, along the South Carolina-Georgia state line. This site, the Savannah River Site National Environmental Research Park, is a 482 square mile federal research area set aside during the Cold War for nuclear weapons development.
Forests of 50 year old pine trees dominate all eight sites. At the researchers' request, in 1999 the U.S. Forest Service arranged for workers to log trees and burn the remaining groundcover in selected areas, creating one central clearing and four peripheral clearings on each site.
They also logged corridors connecting each central clearing to just one of the four peripheral clearings, leaving the other three separated by forest. The clearings grew into fields, creating a patchwork of forest and field habitats hosting very different species.
Research on the sites lasted for two years, with most data collected in 2000 and 2001.
For one of two major experiments, the researchers planted male holly bushes in the central patch and female hollies in the four peripheral patches. They chose holly because it is not naturally present in the forest and the female trees cannot bear fruit unless pollinated by males.
The researchers waited until the hollies had flowered and then measured the fruit set, or the percentage of flowers that turned into berries, in each of the clearings. The hollies in the connected patches were consistently more fruitful than in the unconnected ones, indicating that more wasps, butterflies and other insect pollinators made it from each central patch through the corridor than through the forest.
In a second experiment, the researchers looked at how corridors affected seed dispersal by birds. The researchers marked thousands of seeds of wax myrtle and holly in the central patch with a sticky powder that can be seen only with a florescent light.
The researchers then placed seed traps under 16 bird perches built in each of the connected and unconnected peripheral patches. Over several months, they collected and analyzed the resulting bird droppings in a lab, finding that more droppings containing wax myrtle and holly seeds were carried from central patches to connected patches than to unconnected patches.
"Our study suggests that these corridors do help in connecting populations, and theoretically they should help sustain networks of populations existing in increasingly fragmented landscapes," Tewksbury concluded.:
