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Gone fishing: Loss of ocean predators has impact on climate change strategies

New research says keeping large fish populations intact is crucial for carbon capture and long-term storage

Griffith University

Continued unsustainable harvesting of large predatory fish, including the culling of sharks, can have far-reaching consequences for the way we tackle climate change.

Professor Rod Connolly, a marine scientist from Griffith University's Australian Rivers Institute, is the co-author of new research that says keeping populations of larger fish intact is critical to carbon accumulation and long-term storage in vegetated coastal habitats such as saltmarsh, mangroves and seagrass.

A paper, "Predators help protect carbon stocks in blue carbon ecosystems", is published in the journal Nature Climate Change and identifies the urgent need for further research on the influence of predators on carbon cycling, and improved policy and management with regard to blue carbon reserves.

The research comes as Australia in particular, in response to a recent spate of shark attacks -- some fatal -- engages in fierce public debate over shark culling.

Professor Connolly warns the loss of top order predators through excessive culling or over-fishing has serious environmental ramifications.

"Altering the numbers of top ocean predators has major consequences for the way we tackle climate change," says Professor Connolly.

"These predators have a cascading effect on the food web and the ecosystem generally that ultimately changes the amount of carbon captured and locked up in the seabed."

Coastal wetlands play a crucial role in this process, extracting carbon from the atmosphere and burying it in the mud for hundreds and even thousands of years.

"When we change the abundance of higher order predators, this affects the number of smaller animals living in the mud, and that has flow-on effects for carbon storage in coastal wetlands," says Professor Connolly.

"We are already aware of the need to manage how many fish we take and from where. But we should also know that our decisions affect climate change.

Professor Connolly says the coastal wetlands that fringe the world's continents are doing a power of environmental good, taking a quarter of a trillion kilograms of carbon out of the atmosphere every year.

However, that efficiency can be easily compromised.

"Predators play an important and potentially irreplaceable role in carbon cycling. The effect of the disproportionate loss of species high in the food chain cannot be underestimated."



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