Giant kelp can grow 40 meters tall and gain half a meter of height in a single day — yet Tasmania has lost more than 95% of its once-vast underwater forests since the 1970s. Now divers are replanting them one hatchery-grown strand at a time.

  • 95%+ of Tasmania's giant kelp forests lost since the 1970s
  • 40 meters — the height giant kelp (Macrocystis pyrifera) can reach
  • 50 cm of growth per day in ideal conditions
  • 16 sites tested for restoration suitability in 2023
  • 6 interns joined the first live-in "underwater gardening" program in 2026

A forest that vanished in a year

Tasmania's giant kelp forests once stretched along the state's east coast, providing the kind of dense underwater habitat divers compare to a rainforest canopy. Warming water from a strengthening East Australian Current, combined with explosive growth in grazing sea urchin populations, wiped most of it out.

Dive instructor Pauline Nuttens, who manages an internship program at the Eaglehawk Dive Centre on the Tasman Peninsula, watched it happen firsthand. She guided tours through a thriving kelp forest in 2015; by the following summer, she told ABC News, the forest was simply gone. "It was gone in less than a year... that was a big shock to me. This is when I realised how catastrophic this was," she said.

How you regrow an underwater forest

The restoration method, developed by Professor Scott Ling at the University of Tasmania's Institute for Marine and Antarctic Studies, starts in a laboratory. Kelp spores are grown onto spools, which divers then wrap around the base of existing seaweed at carefully chosen sites — a process researchers and volunteers call "underwater gardening."

The Tasmanian Giant Kelp Restoration Project — a partnership between The Nature Conservancy, IMAS, Natural Resource Management South, and CSIRO — tested 16 sites for suitability in 2023 before scaling up outplanting at the best-performing locations in 2024 and 2025. Hundreds of giant kelp plants have since reached the surface at several sites that had been barren for a decade.

"When conditions are right, you can regrow a forest within a year." — Dr. Scott Bennett, marine ecologist, Institute for Marine and Antarctic Studies

New hands in the water

In 2026, the Eaglehawk Dive Centre launched a live-in internship that brought six participants from as far as California and Sweden to spend a month training in cold-water diving and kelp-planting technique. Interns pay roughly $3,000 to cover board, food, and dive equipment — and spend their days cutting back competing seaweed around newly planted juvenile kelp so it can establish without being crowded out.

"We also do something called underwater gardening... we're basically cutting around the kelp restoration sites, so where we're out planting the juvenile giant kelp, we're cutting about a metre around all of the other kelp that could out-compete the juveniles," said intern Linnea Bird, a graduate student whose master's research focuses on giant kelp.

Why a kelp forest is worth saving

A single healthy kelp forest supports lobsters, scalefish, abalone, and countless smaller invertebrates, fish, mammals, and birds, while also buffering coastlines from erosion and improving local water quality. Losing it ripples outward to local dive tourism and commercial fisheries alike.

Results so far have been what Dr. Bennett calls "a mixed bag" — storms, marine heatwaves, and hungry herbivorous fish can knock back a young planting fast, which is why the project now puts as much effort into picking the right sites as into the planting itself. The lessons from Tasmania's east coast are already being shared with restoration efforts along the coasts of Victoria and South Australia, where giant kelp has suffered similar declines.