Academic's work presented to UN General Assembly
Trawling over fragile corals on undersea mountains is as environmentally devastating as the clear-felling of old-growth forests, says University of the Sunshine Coast marine scientist Dr Thomas Schlacher.
Dr Schlacher was part of an international team of marine biologists that reported to the United Nations General Assembly in New York this week on the impact of human activity on deep-sea ecosystems.
He said the UN had commissioned the team, led by New Zealand’s National Institute of Water and Atmospheric Research scientist Malcolm Clark and the Zoological Society of London Senior Research Fellow Dr Alex Rogers, to assess how vulnerable deep-sea ecosystems were to human activities, particularly trawling.
The team’s extensive report, which took a year to compile, is likely to be used by the UN in assessing a way forward towards international regulations on fishing near undersea mountains known as seamounts.
"We focused on seamounts which harbour unique and highly-diverse communities not found anywhere else in the ocean," Dr Schlacher said of the research work.
"There may be as many as 100,000 seamounts protruding from the world’s ocean floors, many still uncharted.
"Australia has some of the most spectacular seamounts in the world: just off the coast of southern Queensland, large mountains rise from the abyssal seafloor several thousand metres high. They dwarf anything on dry land: picture the Glass House Mountains and blow them up a hundred times."
"When we think of corals, the Great Barrier Reef comes to mind immediately and most people appreciate its unique biodiversity. Yet corals are equally prolific on deep mountains growing to depths of 3000 metres.
Dr Schlacher described these unique and highly-diverse coral reefs on seamounts as among the most fascinating ecosystems on earth.
"In the permanently dark and cold waters, the corals grow extremely slowly and some may be up to 800 years or older. The abyssal coral reefs support a diverse range of other life forms and are a valuable fish habitat."
He said the crux of the problem was that the corals promoted fish but were easily damaged by trawler gears.
"In essence, one could equate the effects of trawling over the fragile corals on seamounts with the devastation caused by clear-felling of old-growth forests on land," he said.
"Many seamounts targeted by bottom fishing lie outside areas of national jurisdiction – the high seas. Management of these activities has been complicated by the lack of knowledge where the most vulnerable seamounts are located – this is where the new report steps in.
"Because large swaths of the ocean are still poorly mapped, we had to think outside the square to come up with a solution to predict where the vulnerable coral reefs on seamounts can be found throughout the world.
"We took corals as biological indicators of how sensitive deep ecosystems are and modelled their worldwide distribution based on their preference for oxygen, temperature, salt content and the like".
"In the next step, we used anomalies in the gravity field of the ocean surface that are caused by the mountains under the surface to predict where the uncharted seamounts are. Finally, we mapped known and potential fishing grounds throughout the world."
"We now have a tool to predict which areas of the deep ocean harbour those spectacular mountains replete with corals and fish. This information is now being used to define areas that are particularly vulnerable to the impacts of deep-sea fishing.
"The most sensible approach would be to curtail all destructive fishing practices on seamounts, as the ecosystems might never be able to recover from the impacts. This is complicated on the high seas, and the United Nations is discussing international regulations.
Dr Schlacher said Australia was leading by example on protecting seamounts.
"Australia has already established protected areas around the Tasmanian seamounts where bottom fishing is prohibited, providing a good example of sensible management of our marine resources," he said.