Drift logs destroying intertidal ecosystems in B.C., study finds

A new study by biologists at the University of Victoria has revealed why the simple back-and-forth motion of drift logs on B.C. beaches has destroyed critical ecosystems that keep the ocean healthy.

Visitors to most beaches on the West Coast will quickly notice the free-floating drift logs that have washed up onto shore.

When the tides go out the logs go with them, and when they come in the logs crash onto rocks and beaches.

"That intertidal zone ... between the high tide and the low tide [supports] a tremendous diversity of life," said Thomas Reimchen, adjunct professor at the University of Victoria.

The study published in the Marine Ecology journal, found that 20 to 80 per cent fewer barnacles on rocks that were exposed to logs, compared to protected crevices.

The fewer the barnacles, the less food there is for species who rely on them.

"This is a coast-wide phenomena that we're losing those foundation species that are so important for so many other species," said Reimchen.

Chris Harley, a zoology professor at the University of British Columbia who wasn't involved in the study, said scientists have always known drift logs could be a problem.

"I have often shaken my fist at drift logs which float by and destroy my precious experiments on the shore," said Harley.

The UBC professor says the study out of UVic did a nice job of examining how extensive a problem that might be.

"Drifting logs are a form of disturbance. So they'll knock off mussels and barnacles and other marine life," said Harley.

He said a little bit of disturbance is good for promoting diversity, but too much will remove habitat-forming species, which results in a loss of food for birds, fish and sea stars.

Reimchen and two undergraduate students, Esteban Pérez Andresen and Melanie Marchant, used Google Earth's satellite imagery and archival photos to measure the log abundance along the western shores of B.C. and Haida Gwaii.

They found a 520 per cent increase in drift logs since the late 19th century — including on remote shores — with more than half of them from the logging industry.