Low lying coral Islands form on top of living reefs. Varying in size, the islands arise from sediments of the reef, skeletons and shells of living biota. Sometimes barely a couple of meters above sea level, hence the name ‘low lying’.
And that is the problem. Scientists at the University of Sydney have found a quarter of Australia’s coral islands are at risk of being wiped out by climate change.
And the risk is not only ecological. If such tiny reefs go under, Australia could lose its right to the ocean water around them.
The report, published in the journal Science of the Total Environment, found 56 Australian coral islands at risk. Three islands in Western Australia were most vulnerable: Scott, Clerke and Imperieuse reefs.
Lead researcher Dr Tommy Fellowes at the USyd’s School of Geosciences Geocoastal Research Group says climate change is destabilising the reefs.
“The fate of low-lying coral reef islands and their associated reef ecosystems hangs in the balance,” says Fellowes, “threatened by the compounding effects of climate change – rising sea levels, warming oceans, intensifying storms and acidification.
“This paper brings those biologically threatening and physical processes together.”
But how does an island destabilise?
“What we mean is, are they going to succumb to the compound effects of climate change? Is sea level rise going to flood them? Are storms then going to be able to erode them? These are the questions we really need to answer.”
Fellowes and the research team used a matrix method to rank the islands for risk, assigning values of between 1 (Very Low) and 5 (Very High).
“If sea level rise was lower than the global average, we assign a lower risk value. If it’s higher, we give a higher one.”
The scientists would repeat the process for various other threats and characteristics, sum them and allocate each site a risk.
Reefs in global decline
A key takeaway, however, was that no island had zero risk.
“They all had some degree of risk,” Fellowes told Cosmos. “But being able to identify that 25% are at more risk will inform … the government or coastal managers to go, okay, we need to go there, collect data, maybe take imagery; understand what’s going on now, before it’s too late and something happens or it changes.
“Just ensuring that the living reef is maintained and intact, is equally as important as the structural stability of the island itself.”
Fellowes says scientists don’t know exactly how many low-lying coral reef islands there are, but estimates roughly 500 to 700.
Even so, the study examined only 56 offshore reef islands, chosen for their ‘strategic importance’.
He says maritime territories grant sovereign rights over critical resources, including fisheries and mineral exploration, making the stability and resilience of coral islands a matter of strategic importance for Australia’s and the region’s coastal management.
Fellowes paraphrases the UN convention on the Law of the Sea to explain: “If you have a reef with an island on it, and that is part of your sovereign nation, you can draw maritime zones from that reef and island to up to 200 nautical miles.
“Now, we’ve seen in the Pacific that’s an extremely important thing to delineate, or to have boundaries with your neighbors.
“In Australia, [reef islands] play a pivotal role, supporting approximately 15 percent, or 1.2 million km2, of our maritime zone across the Indian and Pacific oceans and to the north in the Torres Strait.”
The research is crucial worldwide to some 65 million people living on similar reef island and for whom the future is uncertain,
The islands are located mostly in the Pacific but also Southeast Asia and the Caribbean. In Australia, however, the Cocos Keeling Islands are at risk. Administered by Australia’s Department of Regional Australia, the permanent population of 600 live on about 14km2 of land “only a couple of metres above sea level.”
“In terms of their risk, we still don’t understand the timescale until it may be inundated.
“[But] there is ongoing research, given that it is a strategically important place for Australia.”
The Greenlight Project is a year-long look at how regional Australia is preparing for and adapting to climate change.
The Ultramarine project – focussing on research and innovation in our marine environments – is supported by Minderoo Foundation.