Two extreme ENSO-driven oscillations in mean sea level destabilise protective shoreline mangroves of Northern Australia
Our investigations confirm over the last half century, there were two widespread instances of extremely low ENSO-related oscillations in mean sea level each causing catastrophic mass dieback and the sudden death of up to 80 km2 of mangrove forests along more than 2,000 km of shorelines of Australia’s remote north. These previously unrecognised instances of severe desiccation in 1982 and 2015 created a longer- term cycle of shoreline collapse and recovery bringing enhanced vulnerability to already depauperate tidal wetland habitats across this semi-arid region faced with rapidly rising sea levels and other pressures. Accordingly, the impacted shorelines of the Gulf of Carpentaria displayed acute sensitivity to not only the extreme sea level lows but also accumulative damaging instances of locally-destructive cyclones combined with other damaging pressures from feral pigs, invasive exotic weeds and uncontrolled scrub fires. These factors together reduced landward migration of mangrove vegetation - much needed for coping with local rapidly rising sea levels. So, along with these things, the newly recognised extremes in atmospheric-driven ENSO processes seriously threaten the longer-term survival and recovery of otherwise enduring shoreline ecosystems and the beneficial services they offer - including their role in slowing down coastal erosion in their retreat across the drowning shorelines.
