The Australian scientists who are responding to the cry: “Kelp needs help”

The “King of Kelp” is how one colleague describes University of Western Australia’s Professor of Marine Botany, Thomas Wernberg.

So imagine his reaction when, diving one day into the crystal blue waters off the mid coast of Western Australia, he found his entire seaweed ‘kingdom’ was just … gone.

“We were pretty shocked,” he tells me in his gentle Scandinavian accent – Thomas hails originally from Denmark.

“We went on a field trip to Kalbarri and we had all the equipment to sample the kelp. But everything was gone. We went to our other sites over weeks – not a single kelp. Before it was this amazing three-dimensional forest of golden kelp. Now it was just sand and algae. Never in our wildest dreams did we think it could be this bad. It was heart-breaking.”

That was 2012, following the devastating 2011 WA marine heatwave which caused the complete loss of 93,000 hectares of kelp forest, very little of which has grown back.

It also triggered a turning point in Wernberg’s life work. He and his colleagues now lead a potentially game-changing new approach to kelp reforestation, part of a desperate global effort to restore the rapidly dwindling forests of the sea.

“We’re kind of at the forefront of what will need to happen everywhere,” he says.

Credit: Supplied

Kelp forests are the lifeblood of our temperate waters. Like their terrestrial cousins, they provide food and habitat: the very foundation of the ecosystem. Kelp reefs cover 28% of the world’s coastlines, and five times as much ocean area as the better known coral reefs. And yet these glories of the underwater world are declining 2-4 times faster than coral reefs and tropical forests. Northern California and Tasmania have lost a breath-taking 95% of their bull kelp and giant kelp respectively over the past decades, with dire consequences for the all the sea life that depends on them: sea horses, crabs, sea snails, abalone, industrial fisheries and much more. Not to mention the loss of all that embodied carbon.

So why hasn’t this ongoing disaster had the same attention as coral?

“I think there are lots of historical reasons,” says Wernberg. “Temperate reefs have been generally overlooked, from research support to media coverage. 10 years ago we did a study and found 80-90% of all media coverage of reefs was of tropical reefs, which is ironic because in Australia and the western world, most people live within a relatively short distance of a temperate kelp forest coastline, not coral.”

Kelp reforestation research has some serious catching up to do. And with kelp forests now stripped from great swathes of the WA coastline, Wernberg and his colleagues knew they urgently needed a gamechanger – a restoration method that could work at a scale that had some chance of matching the ongoing and drastic kelp loss.

“Never in our wildest dreams did we think it could be this bad.”

Professor Thomas Wernberg

That’s been the problem with kelp restoration to date – it’s extremely labour intensive and slow. The two great killers of kelp are ocean heatwaves and overgrazing by sea urchins (which multiply when their natural predators are overfished and can raze kelp forests back to bare rock, creating so called ‘urchin barrens’). The main restoration methods traditionally use divers, either through removing sea urchins by hand, or transplanting individual seaweeds onto rocky reefs.

One way of upscaling kelp restoration is to kill the predatory urchins by spreading quicklime from boats – an approach being trialled elsewhere in the world. But urchins weren’t the problem in WA: heat killed the kelp, yet even though sea temperatures have cooled again, kelp wasn’t growing back. They needed a technology that could sow new kelp plants across areas the size of hectares.

And Wernberg knew of one possibility. Even though he moved to UWA in 1999, he retained his Scandinavian connections and is concurrently a senior researcher with the Norwegian Institute of Marine Research. Back in the early 2000s, Norwegian scientists trialled a concept called ‘Green Gravel’.

It’s simple but inspired. Basically, you gather small stones – gravel – and seed them with baby kelp in an aquaculture centre. This green gravel can then be tossed off the side of a boat, sink to the rocky reef below and establish a base population to regrow kelp forest. Though promising, the original pilot project in Norway went no further. But it was ripe for revival.

Four years ago, Wernberg and his colleagues, in conjunction with European seaweed restoration company SeaForester, and the NSW Department of Primary Industries, started Australia’s first green gravel trials off the coast of Kalbarri. More than 1,000m2 of reforestation has been sown in the pilot phase, with the next multi-hectare expansion in the planning.

But that single pilot trial belies the potential global significance of green gravel. In 2020, Wernberg co-founded the international Green Gravel Action Group to coordinate and fast track projects globally. There are now almost 20 green gravel projects around the world, including at least two others in Australia: in Tasmania and off the coast of NSW.

“Our mission is bigger than just here,” Wernberg tells me. “I’ve dived in kelp forest all over the world. So many places are like WA; you see that destruction. Our mission is global. Kelp needs help.”

And that’s a sentiment shared by University of NSW Professor of Marine Ecology, Adriana Vergés. She’s the force behind pioneering Australian seaweed restoration project ‘Operation Crayweed’, based in Sydney. If Wernberg is Australia’s “King of Kelp”, Vergés is its queen.

Freshwater community planting off the Bondi shoreline. Credit: Leah Wood

“It’s a super-promising start,” she says of the WA green gravel project. “Very exciting because of the scalability. But I think the other really cool thing about the project is that they are starting to look at selecting the genetics to grow more heat tolerant plants – like is being done with corals.”

And there’s one more pioneering innovation in the WA project. ‘Kelp credits’ – attached to carbon credits. Even though seaweeds are some of the fastest growing, most productive plants in the world, there is currently no system internationally to count kelp restoration as a carbon emissions offset.

“They are pioneering ways of making it work, so this has huge potential for storing carbon and helping fund kelp reforestation,” says Vergés.

This new system pairs an accredited carbon credit with a kelp credit – each representing one newly grown kelp plant. UWA has already signed up, so its carbon abatement will include funding kelp restoration. Meanwhile, according to Jon-Paul Cox, director of Canopy Blue (the Perth based company behind the kelp carbon credits) they are working on the science of kelp’s carbon sequestration so that its reforestation can be counted for credits in future.

And every one of these cutting-edge efforts will be needed. In recognition that the global situation for kelp forests is every bit as dire as those on land, in 2022, Dr Aaron Eger in collaboration with his mentor Vergés founded the Kelp Forest Alliance – an international affiliation of over 500 people in 25 countries. For the first time, there is a live centralised database of every kelp forestation project around the world recording what works, and what doesn’t.

Location of the training data (black dots) and the low-resolution validation sites (red dots). Cartographic projection EPSG: 54042. Maps in this article are south-oriented to highlight the connectivity of giant kelp forests at sub-Antarctic latitudes. Credit: A High-Resolution Global Map of Giant Kelp (Macrocystis pyrifera) Forests and Intertidal Green Algae (Ulvophyceae) with Sentinel-2 Imagery, Mora-Soto et al.

“We’ve already discovered the best predictor of success is proximity to an existing kelp forest,” says Vergés. “So it shows the most important thing is to protect what we have.”

And they’ve issued a truly grand challenge – the Kelp Forest Challenge – aimed at restoring one million hectares of kelp forest by 2040.