Australia’s thousand year-old wetlands could be wiped out

By Angela Heathcote 10 August 2017
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Researchers have found that by accounting for the impact of man-made structures on sea-level rise in our wetlands, the rate at which these vital ecosystems are predicted to disappear is increased by 50 per cent.

WETLANDS— one of the most vital ecosystems in the world, providing habitats for fish and birds while simultaneously intercepting the impacts of climate change—may now have a short life expectancy of just 80 years, scientists have found.

In a study published today in Nature Communications, researchers from the University of Newcastle analysed the impacts of man-made structures on the health of coastal wetlands, finding that they significantly increased a wetland’s vulnerability to sea-level rise. 

While scientists have understood for some time the dramatic effects of sea-level rise on low lying areas such as wetlands, until now little was known about the disturbances caused by the development of roads, drains and other obstructions to the water tide.

Jose Rodriguez, who led the study, explained that when roads are built across wetlands, the tide is forced to move from one side of the road to another through bridges or culverts, rather than allowing the tide to naturally flow across the mud flats.

“As a result, it takes more time and energy for the water to reach the other side. This results in water sitting in the wetland longer and in a reduction of the high tide water level. Then at low tide, some areas of the wetland are not able to fully drain resulting in ponding,” he said.

The researchers further explained that wetlands have very intricate inundation regimes that are dictated by the timing, frequency, duration and the extent of particular water flows. “Changes such as prolonged water exposure will essentially drown the vegetation,” Jose added.

wetlands wiped out

A close up of a mangrove. (Image Credit: The University of Newcastle)

The bathtub model

Scientists have been using the bathtub model to predict the effect of sea level rise on coastal wetlands.

The model assumes that water flows in and out of a wetlands uninterrupted and has therefore resulted in a dramatic underestimation of the threat of sea-level rise. 

Patricia Saco, co-author of the paper, explained that when the impact of man-made structures and how these impede tidal flows are accounted for the rate at which wetlands are predicted to disappear is increased by 50 per cent.

In place of the bath tub model the pair of researchers have developed a ‘hydrodynamic’ approach to understanding the effect of sea-level rise on wetlands, which acknowledges the impact of man-made structures on inundation regimes.

“It’s not that we need to put more structures in place, rather we have to regulate the flow in a way that reduces the inundation period,” Patricia told Australian Geographic