Rising Sea Levels Spell Danger For Shorebirds

A James Cook University-led study which found rising sea levels will dramatically reduce shorebird numbers in Europe could forecast a similar fate for their Australian cousins – even if humanity manages to limit global warming to less than two degrees.

In a new paper, JCU Senior Lecturer in Mathematical Modelling Dr Martijn van de Pol and his research colleagues found Eurasian Oystercatcher numbers across three Dutch islands in the Wadden Sea will decline by between 56 per cent and 79 per cent due to sea level rises over the next century.

"Half of this collapse will happen in the next 50 years with numbers already declining now due to sea level rise, and the rest in the 50 years after that," Dr van de Pol said.

"So, there are both immediate impacts and delayed impacts of sea level rise and global warming."

The paper found that even in a low-emission scenario that limits global warming below two degrees, it was projected all three studied oystercatcher populations would be reduced by more than half.

The Wadden Sea is the world's largest intertidal system and a UNESCO World Heritage Area.

Dr van de Pol said given the high rates of sea level rise in northern Australia, and in particular in the Gulf of Carpentaria where sea level rise was three times the global average over past decades, he had concerns for shorebird populations closer to home.

"The main solution is to reduce greenhouse gas emissions to stop sea level rise," Dr van de Pol said.

"It is also important that there is enough space available for nature so that marshes, beaches and mangroves can move inland under sea level rise. Often this cannot happen, because humans are using this inland land for other purposes such as agriculture, roads, seawalls, or housing, meaning that these nature areas are squeezed out by sea level rise."

Eurasian Oystercatchers typically nest on the lower parts of the saltmarsh using a nest scrape on the ground.

"Historically, these nests would rarely get flooded, but they are now getting flooded more often due to sea level rise, causing fewer offspring being born and population numbers dropping," Dr van de Pol said.

Researchers analysed four decades of field data with models of sea level rise, coastal geomorphology, adaptive behaviour and population dynamics to confirm that habitat quality was already declining for shorebirds due to increased nest flooding.

"So far, scientists have typically assumed coastal wildlife will mainly be affected by sea level rise due to habitat loss, but our study shows that strong impacts already occur well before habitat drowns due to more frequent flooding events," Dr van de Pol said.

Dr van de Pol said he hoped to study the impact of sea level rise on Queensland shorebird populations in the coming years.

The study was conducted by Dr van de Pol in conjunction with JCU's Dr Lyanne Brouwer, the Netherlands Institute for Ecology's Liam Bailey, Magali Frauendorf and Martijn van der Sluijs Groningen Institute for Evolutionary Life Sciences' Nadia Hijner, Radboud University's Andrew Allen, Hans de Kroon and Eelke Jongejans, and Sovon's Bruno Ens.

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