May 042012

The ecological recovery at some of our sandy beach sites was remarkable

The reappearance of long-forgotten habitats and the resurgence of species unseen for years may not be among the expected effects of a natural disaster. Yet that’s exactly what researchers have found on the sandy beaches of south central Chile, after an 8.8-magnitude earthquake and devastating tsunami in 2010. Their study also revealed a preview of the problems wrought by sea level rise — a major symptom of climate change.

In a scientific first, researchers from Universidad Austral de Chile and UC Santa Barbara‘s Marine Science Institute (MSI) were able to document the before-and-after ecological impacts of such cataclysmic occurrences. A new paper appearing in the journal PLoS ONE elucidates the surprising results of their collaborative study, pointing to the potential effects of natural disasters on sandy beaches worldwide.

“So often you think of earthquakes as causing total devastation, and adding a tsunami on top of that is a major catastrophe for coastal ecosystems. As expected, we saw high mortality of intertidal life on beaches and rocky shores, but the ecological recovery at some of our sandy beach sites was remarkable,” said Jenifer Dugan, an associate research biologist at MSI. ” Dune plants are coming back in places there haven’t been plants, as far as we know, for a very long time. The earthquake created sandy beach habitat where it had been lost. This is not the initial ecological response you might expect from a major earthquake and tsunami.”

Their findings owe a debt to serendipity. With joint support from Chile’s Fondo Nacional de Desarrollo Científico y Tecnológico and the U.S. National Science Foundation‘s Long Term Ecological Research program, the scientists were already knee-deep in a collaborative study of how sandy beaches in Santa Barbara and south central Chile respond, ecologically, to human-made armoring such as seawalls and rocky revetments. As part of that project, the Chilean team surveyed nine sandy beaches along the coasts of Maule and Bíobío in late January, 2010. The earthquake hit in February.

Realizing their unique opportunity, the scientists quickly changed gears and within days were back on the beaches to reassess their study sites in the catastrophe’s aftermath. They have returned many times since, diligently documenting the ecological recovery and long-term effects of the earthquake and tsunami on these coastlines, in both natural and human-altered settings.

The magnitude and direction of land-level change brought the greatest impact, drowning beaches especially where the tsunami exacerbated earthquake-induced subsidence — and widening and flattening beaches where the earthquake brought uplift. The drowned beach areas suffered mortality of intertidal life; the widened beaches quickly saw the return of plants and animals that had vanished due to the effects of coastal armoring.

“With the study in California and our study here, we knew that building coastal defense structures, such as seawalls, decreases beach area, and that a seawall results in the decline of intertidal diversity,” said lead author Eduardo Jaramillo, of Universidad Austral de Chile. “But after the earthquake, where significant continental uplift occurred, the beach area that had been lost due to coastal armoring has now been restored. And the re-colonization of the mobile beach fauna was under way just weeks after.”

Read more . . .

via Science Daily

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