By Annelies Gartner
Finding solutions to restore declining kelp forests damaged by climate change.
Kelp forests dominate temperate coastal rocky shores worldwide where they create a habitat for many marine species, store nutrients and capture underwater carbon as efficiently as tropical rainforests capture atmospheric carbon.
Seaweed such as kelp can help us address many problems including several of the United Nations Sustainable Development Goals.
It can help improve food security, be used in manufacturing sustainable products, become a biofuel or used to feed livestock. Kelp has nutritional properties, aids carbon sequestration, supports ecosystems and biodiversity and provides economic benefits for coastal communities.
ARC Laureate Fellow Professor Thomas Wernberg, from The University of Western Australia’s Oceans Institute and School of Biological Sciences, and a team of marine biologists are helping secure the future of kelp forests.
"We're working to understand how coastal habitats where kelp grows respond to stressors such as climate change, marine heatwaves, invasive species and nutrient run-off from the land,” Professor Wernberg says.
"It’s important we find solutions to habitat decline through protection and restoration and increase knowledge of the many benefits our marine ecosystems provide, such as their potential role in climate mitigation.”
Professor Wernberg and colleagues have compiled a database of thousands of time series points for kelp forests, and consulted almost 40 experts globally, and found that 40 to 60 per cent of the world’s kelp forests have been in decline over the past 50 years.
The decline has been caused by many factors including overfishing, direct harvesting, nutrient run-off and, in particular, global warming including increasingly frequent marine heatwaves.
Over the past 20 years, the team has repeatedly surveyed 2000km of coastline from Albany and Cape Leeuwin to Ningaloo Reef in Western Australia.
In 2011, WA experienced an extreme marine heatwave, which lasted 10 weeks. The climate event featured ocean temperatures up to six degrees above normal and had devastating impacts across WA’s marine environment.
Based on the team’s extensive data collection and modelling, they estimated that 385 sq km of kelp forest was wiped out by the 2011 marine heatwave.
“We found the event was responsible for altering the ecological structure of the ecosystem,” Professor Wernberg says.
“Among the factors preventing re-establishment of kelp were expanding turf algae and an increase in tropical grazing fish species.”
This year, Professor Wernberg, Dr Karen Filbee-Dexter and Dr Shinae Montie led a review into the long-term impacts of marine heatwaves on biodiversity and management strategies required to mitigate further damage.
“The past two years – 2023 and 2024 – have been the most extreme years on record for marine heatwaves,” Professor Wernberg explains.
“Globally, marine heatwaves are a natural phenomenon, but they have become stronger, longer and more frequent since 1980 because of man-made climate change.”
It’s important we find solutions to habitat decline through protection and restoration and increase knowledge of the many benefits our marine ecosystems provide, such as their potential role in climate mitigation.
ARC Laureate Fellow Professor Thomas Wernberg.
The team found marine heatwaves had a direct impact on species’ productivity and distribution, and indirect impacts through altered species’ interactions.
“We found a shift in species’ abundance and distribution, decimation of seagrasses, corals and kelps and megafauna mortality,” Professor Wernberg says.
“Impacts on species that play an important part in the ecosystem resulted in cascading changes to the biodiversity, through loss of food sources and habitats.”
Professor Wernberg and an international team of ecologists, oceanographers and atmospheric scientists have proposed a framework and categorisation scheme for marine heatwaves, based on similar schemes for cyclones and other extreme events.
The framework has helped increase scientific and public awareness of severe marine events and is now being applied globally to the study of marine heatwaves.
“Marine heatwaves have been at the core of environmental, biological, ecological and socioeconomic change in marine ecosystems in virtually all oceans and seas and these impacts have increased exponentially,” Professor Wernberg says.
The marine heatwaves have had a significant impact on one of Professor Wenberg’s key research focus areas, the Great Southern Reef.
Kelp forests dominate the interconnected ecosystem of temperate rocky reefs of the area that stretches 8,000km around the southern coastline of Australia, from the mid-west coast of WA, along South Australia and Tasmania, and up along the east coast to the northern border of New South Wales.
The biodiversity hotspot is home to thousands of species including seaweed, giant cuttlefish, sea urchins, leafy sea dragons, reef fish, snails and great white sharks.
Depending on the group, somewhere between 30 to 80 per cent of the species in the reef system are found nowhere else on the planet and the kelp species that dominates this ecosystem is the Golden Kelp Ecklonia radiata.
“Although around 70 per cent of Australians live within 50km of a temperate coastline, few are aware of their spectacular blue front yard and its importance,” he says.
“This motivated us to not only understand the ecology of the kelp forests, but also to work to boost local and global awareness of the this truly unique temperate marine ecosystem.”
In 2019, The Great Southern Reef was acknowledged by Mission Blue’s founder, ocean pioneer, marine biologist and ocean activist Dr Sylvia Earle, as a Hope Spot. Hope Spots are recognised as places that are critical to the health of the oceans.
In 2024, Professor Wenberg was awarded more than $3.6 million for his project The Great Southern Reef: Surviving and Thriving in the Anthropocene.
“The project will integrate long-term ecological field data with seascape genomics and novel breeding and stress experiments to better understand the functions, challenges, opportunities and trajectories for Australia's Great Southern Reef and its kelp forests,” Professor Wernberg explains.
Image: Professor Thomas Wernberg with past and current students.
In Australia, decisions affecting the Great Southern Reef are divided across five states and the Federal Government.
As human impact and climate events continue to take a toll on the world’s kelp forests the biggest priorities are protection and restoration, but it comes with difficulties.
“Traditional methods for restoring kelp under water rely on scuba divers manually planting the reef with kelp one by one, which can be inefficient, expensive and potentially dangerous,” Professor Wernberg says.
In 2020, with funding from the Australian Research Council, and in collaboration with scientists at the Institute of Marine Research in Norway, the team developed green gravel – small rocks seeded with kelp.
“Green gravel can be an efficient solution for the safer, and potentially large-scale restoration and replenishment of damaged kelp forests,” he explains.
The restoration starts in the lab where during its early stages of life the kelp secretes a sticky substance, which it uses to attach itself to the small rock.
Once established, the kelp and their rock anchors can be scattered from a boat on to the reef where some species can reach full canopy height in about a year.
The green gravel work has gained international recognition, and the team now leads the Green Gravel Action Group, whose mission is to develop, test and apply green gravel and other seeding-based methods to restore carbon-capturing forests.
Countries trialling and testing these green gravel techniques include Norway, Portugal, Sweden, UK, USA, Canada, Peru and Chile.
“Initial trials have shown promising results, and we are now working to develop the technology for cost-effective, large-scale production,” Professor Wenberg says.
Interest in the team’s work is growing from fish and seaweed farmers who see the potential of green gravel as an alternative revenue stream.
They have also collaborated with the Schmidt Marine Technology Partners who have funded the team to develop a concept to upscale green gravel seeding and make it available to community groups and local municipalities.
“We want to promote the value proposition for kelp: not only ecological, but also socio-economic services that kelp forests provide,” Professor Wernberg says.
Read the full issue of the Summer 2025 edition of Uniview [Accessible PDF 13MB] .