By Rachel Tompa
BERKELEY — Even a quiet stroll in the park can dramatically change natural ecosystems, according to a new study by conservation biologists from the University of California, Berkeley. These findings could have important implications for land management policies.
The study compared parks in the San Francisco Bay Area that allow only quiet recreation such as hiking or dog walking with nearby nature reserves that allow no public access. Evidence of some native carnivore populations – coyote and bobcat – was more than five times lower in parks that allow public access than in neighboring reserves where humans don’t tread, the researchers report.
The dearth of these animals in the parks carries implications beyond just these species. Since the carnivores in the study are often the top predators in their areas, these animals also shape the rest of their surrounding ecosystems. The flight of large animals from heavily visited parks for more serene surroundings could, in turn, influence populations of small animals and plants, the researchers said.
“Carnivores are sensitive indicators of human disturbance,” said Sarah Reed, postdoctoral scholar in UC Berkeley’s Department of Environmental Science, Policy and Management and the study’s lead author. “Their presence or absence can be a good, early clue to how the ecosystem is doing.”
To measure carnivore numbers, Reed studied the droppings of six native and non-native mammalian carnivores in 28 parks and preserves in northern California. The parks in her study allow public access, but don’t allow motorized vehicles or hunting and fishing. Most visitors to these parks hike or walk their dogs, Reed said. The preserves in the study have limited or no public access.
Reed found more than five times as much coyote and bobcat scat in preserves with no public access than she did in the parks. Coyotes and bobcats are both native carnivores. She also found more scat from the native gray fox and the non-native red fox in unvisited areas, and more dog and cat droppings in visited parks.
Reed said she did not expect these findings. She and many other conservation biologists assumed that activities such as hiking or horseback riding were relatively benign, she said. “I was surprised that the difference was so dramatic,” Reed said.
Adina Merenlender, cooperative extension specialist in the Department of Environmental Science, Policy and Management and senior author on the study, said the findings “are probably the most surprising results that have come out of my lab to date.”
The differences in carnivore populations are even more surprising when you consider that these animals are most active at night, dawn and dusk, and that people visit parks during the day, Reed said. “We assumed that carnivores and people were avoiding each other in time and space,” she said.
Reed was initially conducting a different study on carnivores when she realized that the differences in their numbers between sites with and without public access were so large that they obscured the data she was looking for. “The evidence I was seeing was strong enough that it warranted a study of its own,” Reed said.
Read the full article here: http://www.berkeley.edu/news/media/releases/2008/07/21_hiking.shtml