Wednesday, January 07, 2009

Tiny Assassin

"Based on extensive field studies, the work challenges six decades of salt marsh science. Ecologists have long thought that stressed soil – too much salt, not enough oxygen – was the main killer of this critical marine habitat.

But Brian Silliman, a Brown University research fellow and a University of Florida assistant professor, said drought-stressed soils pave the way for predatory periwinkles that spread fungal disease as they graze on cordgrass. “Snails can transform healthy marsh to mudflats in a matter of months,” said Silliman, lead author of the Science paper. “This finding represents a huge shift in the way we see salt marsh ecology. For years, scientists thought marsh die-off was simply a ‘bottom-up’ problem related solely to soil conditions. We found that the trouble also comes from the top down. Drought makes the marsh vulnerable, then the snails move in.”

"The findings, the authors argue, underscore the interplay of climate and consumers in the worldwide collapse of coastal systems. While an overabundance of snails may fuel southeastern salt marsh destruction, they point to other examples of habitat destruction that may be caused, in part, by a plethora of grazers: sea urchins wiping out California kelp beds, sea stars devastating Australian coral reefs, snow geese decimating marshes along the Arctic Sea, bark beetles killing off Arizona pine forests."

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