When the predator species, such as rockfish, at the top of the food chain are removed, then the species that they normally eat, such as snails and barnacles, begin to increase in number. Many of these are herbivores that eat kelp. When their numbers increase, they decrease the amount of kelp, in turn changing how kelp forests look and the type of species that are associated with the kelp forest.

"Kelp forests are so sensitive," said Halpern. "If you remove some of the predators, then you can have an effect on the entire kelp forest ecosystem."

He explained that until now studies of kelp forests looked at either overfishing or increased nutrients. This is the first study to put both variables together to see which is more important.

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Contact: Gail Gallessich
gail.g@ia.ucsb.edu
805-893-7220
University of California - Santa Barbara
25-May-2006