El yali national reserve: A system of coastal wetlands in the southern hemisphere affected by contemporary climate change and Tsunamis

Abstract

El Yali is a complex wetlands system composed by more than 14 waterbodies, located in central Chile and delimited by two basins of the most important rivers of the region. Among the waterbodies is a coastal lagoon, some estuaries, artificial wetlands, salt mine and inner lagoons that were coastal lagoons in the past but due to tectonic processes have been moved and raised to their current location. The damming of the river that delimits the system to the south in 1968 cutoff the natural the sedimentary supply to the extensive beach and dunes, leaving the wetlands in a situation of vulnerability before climate change and variability, anthropic pressure, ocean swells and tsunamis. In the present chapter is illustrated the degradation that the wetlands system is suffering, by means of the estimation of tendencies of the long term records available in the zone, antecedents about its natural history, anthropic pressure and natural disasters like earthquakes, tsunamis, ocean swells and ENSO, along with field monitoring that has been carried out with the objective of implementing an ecological restoration. These antecedents show a decrease of precipitations and river discharges, an increase of ambient temperature and sea surface temperature, a rising of sea level and a change of the incident waves. El Yali was severely affected by the earthquake and tsunami in 2010, which destroyed 800 ha of beach and coastal dunes that provided natural protection. In many opportunities, El Yali was affected by earthquake and tsunamis, intense ocean swells and ENSO, all phenomena that dissipate energy destroying the natural barrier the dunes represent. However, before the construction of Rapel reservoir, the sedimentary supply allowed a rapid recovery of the beach, sandbar and dunes. When this sediment supply was cutoff, the dunes has enough material to support the equilibrium of the system for some decades, but when tsunami waves destroyed the dunes, there was no sand supply to restore the beach nor the dunes. This generated a substantial change in the system, turning it more vulnerable to tsunamis, even smaller, ocean swells, and sea-level raising associated to ENSO Kelvin waves and climate change. For this reason, the first proposed restoration action is to restore the dunes and plant a vegetal cover with native species that reinforce and maintain the dunes.