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The dying of Tasmania's kelp forests and an attempt to save them
The giant kelp forests that flourished on the east coast of Tasmania had almost disappeared before most people realised they were gone.
The ecological community of giant kelp forests of south-east Australia has been gradually disappearing, particularly on the east coast of Tasmania, due to changing oceanographic conditions and associated changes in processes threatened by climate change.
The climate-related loss of more than 95 per cent of Tasmania's giant kelp was cited in a recent report by the Intergovernmental Panel on Climate Change as an example of the cascading impacts on natural systems and society. The Tasmanian global warming hotspot not only cost the kelp forests, but also the aquatic ecosystem and the fishing and diving industries that relied on them.
High temperatures mean fewer nutrients and slower growth
It is the high temperatures that slow growth and limit the main growing season, and fewer nutrients, so growth becomes more difficult.
Karen Gowlett-Holmes, one of the best-known marine biologists "Down-Under" and a specialist in kelp forests, says: "If you ask me what the cause is, it's climate change."
Karen is a marine biologist and has observed the decline of kelp over many decades. She says the seas off eastern Tasmania are being affected by a combination of climate change and the southward shift of the East Australian Current. "Our little area off the Tasmanian coast is one of the places on the planet where the ocean is warming the fastest, so this is really a hotspot."
"Weedy Seadragon" in the giant kelp ecosystem
Many divers like professional photographer Gerald Nowak remember times when the seaweed in Bicheno, further north on the coast of the state of Tasmania, "was so dense that fishermen simply moored on the giant kelp instead of anchoring". "Now there's only the odd tree left," he says. "The seaweed is practically extinct on most of the east coast." It is not only ecologically important and sensible to preserve these "underwater forests". Nowak's credo: "A dive between the dense and tall poles of the kelp forest is like a sensual walk in an enchanted forest." Only here can you find the magically beautiful "Weedy Seadragons".
Scott Bennet from the Institute of Marine and Antarctic Studies gives a similar account: "I grew up in Tasmania and learnt to dive with my parents. You'd swim out from the boat ramp and there was huge kelp everywhere and you could have a fantastic dive in the huge kelp forest.
When I came back five or 10 years later, the forest was gradually disappearing, and then suddenly it was gone."
For the past 18 months, a team including Dr Scott Bennett and dive tourism entrepreneur Mick Baron has been conducting giant kelp seeding trials on a rocky reef on the Tasman Peninsula. On a recent trip with Guardian Australia, they had their first success: The kelp grew up to 3 metres in six months.
Having proven the concept - that giant kelp can be sown on strings wrapped around reef blocks and then attached to the reef itself - they now want to go even bigger. With an initial $300,000 philanthropic grant from the newly established Sea Forest Foundation, a project of climate entrepreneur Sam Elsom, they hope to seed a full half-hectare of lush kelp forest.
Because the seaweed grows so quickly - up to 10 metres in a year - a successful project could result in a full canopy covering an area of 100 by 50 metres by next summer. Everyone involved realises that the project will present challenges, but they are very ambitious about the potential goals.
"The goal is to save the huge kelp forests in Tasmania," says Bennett. "We're at a point where they're doomed if we don't do something".
From the outside looking in, the biggest question facing the company is: What's to prevent the newly seeded kelp from going the same way as the historic forests?
The warm East Australian current brings with it a major problem, a new predator of the kelp forests: the longspined sea urchin (Centrostephanus rodgersii). The population of this species is estimated to have tripled since 2016, turning many areas into a so-called "sea urchin desert". The scientists will try to counteract this by choosing a location where there are fewer urchins than average and relying on students and diving enthusiasts to protect the site by helping to collect the urchins. They hope that the state government will provide further support and take action to promote reef restoration.
Marine heatwaves are also a clear threat and Elsom's support will play a crucial role in combating this. His company, Sea Forest, aims to commercially cultivate Asparagopsis, a seaweed that could significantly reduce greenhouse gas emissions from cattle when added to their feed. Last year, Sea Forest provided 250,000 algae to scientists and is supporting work on temperature-tolerant strains that could ultimately increase the chances of survival.
Video: Revitalising Tasmania's kelp forests
In Will Murray's video: "The desperate bid to revive the giant kelp forests of Tasmania", you get a good overview of the current state of the kelp forests and the plans to save them.
Scott Bennet comments: "I'm really worried about what this summer is going to bring. The average increase in ocean temperatures that we've seen globally this year and that are predicted for Tasmania are exactly the conditions under which we've seen these losses of giant kelp forests in the past.
There are literally hundreds, if not thousands, of species of animals and algae that live in our kelp forests in Tasmania and southern Australia that are found nowhere else on Earth. We need to save them."
According to all those involved, it is certain that without active intervention, the "forests" will be lost. There are not many left, they will not recover on their own. "If we do nothing, it's a sure thing that they will disappear completely," says Bennet.