Coastal defenses on sandy beaches in the Biobio and Maule regions: What can we learn from their effect in the earthquake of 27th february, 2010?

Abstract

Human impacts on sandy beach ecosystems include the construction of coastal defences in response to coastal erosion and retreating coastlines. Field studies carried out in January 2010 along sandy coastal beaches of the Bíobío and Maule regions (south central Chile), indicated lower populations of intertidal macrofauna at sites located in front of sea walls with direct wave interaction during high tide, compared with those found at sites with sea wall defences but without any wave interaction, or at sites without any intervention. Studies carried out since March 2010 show that the width of the intertidal zone of sandy beaches on the Arauco peninsula (ca. 36ºS) and nearby areas increased due to continental uplift (ca. 2-2.5m) as a result of the earthquake of February 27th, 2010. This resulted in unexpected interactions with sea defences including i) the creation of new upper intertidal habitat seaward of seawalls, followed by rapid recolonisation of hitherto absent mobile upper and mid shore fauna, and ii) the loss of lower shore species due to uplift of the previously submerged rocky substrate. It is suggested that outcomes such as these should be taken into consideration during planning of the reconstruction of the coastal zone devastated by the earthquake and tsunami of February 27th 2010.