Hunch confirmed:

Corridors rescue plant diversity

By Charlene Polk

  A variety of plants and animals have a better chance of survival because of landscape corridors, according to a recent South Carolina study.

  For years, ecological planners have used habitat corridors to connect patches of natural environments in hopes that they would raise the diversity of plant and animal life, but without any proof that they were effective. Now a six-year study headed by Dr. Ellen Damschen at the Savannah River Site in South Carolina has proven that these corridors are in fact helping increase biodiversity.

  “Corridors are used all of the time in management plans by cities, counties, etc on a variety of scales,” said Damschen, a postdoctoral fellow at the University of California-Santa Barbara. “This study answers the question of whether corridors actually work and the answer is yes.”

  According to the study, published in the September,2006, issue of Science, “Habitat patches connected by corridors retain more native plant species than do isolated patches, this difference increases over time, and corridors do not promote invasion by exotic species.”

  Damschen and her associates started the study to measure the effectiveness of plant corridors because the only previous studies had been done on very small scales and were not able to really judge whether or not corridors affected anything, she said.

  “This shows how corridors affect entire landscapes,” Damschen said, “and it’s the first study to look at plants.”

  To conduct the study, researchers created six experimental landscapes in the midst of a dense pine forest, all of which comprised one connected patch and three unconnected patches. Damschen and her associates surveyed the plant species in each patch from 2000 to 2005.

  There was no immediate increase of species in the connected patches of land but over time the connected patches contained 20 percent more plant species than the unconnected patches, according to the study.

  Damschen’s study is the first good demonstration of the effects of corridors on species richness, and not just the viability of individual species, said Reed Noss, the Davis-Shine Professor at Central Florida University. Noss stressed the importance of corridors as connectors in the ecosystem.

  “Corridors are important to the extent that they maintain existing and natural connections, or restore lost connections, between populations of fragmentation-sensitive species,” he said.

  Because corridors provide connectivity, they contribute to gene flow and so can even help reduce extinction rates in small populations, Noss said.

  Damschen’s study, funded by the National Science Foundation and the US Forest Service, reported that this increase in plant species was apparent in spite of environmental variables, such as high amounts of rainfall.

  Now that they are certain that corridors work, researchers want to know even more.

  “The second question is when and for which species. Now we’re asking how corridors affect those species, when corridors matter,”  Damschen said.

  And why should we care about her research?  “If the average person appreciates a diversity of wildflowers and other plants,” Noss said, “they should want natural areas in the landscapes where they live to be well connected to other natural areas.”