The Disappearing Forests Beneath the Waves

How Tasmania’s giant kelp, one of Earth’s most spectacular ecosystems, has collapsed and the race to bring it back

Tasmania was once fringed by underwater cathedrals. Giant kelp (Macrocystis pyrifera) towered 30 metres from the seafloor, its canopy filtering sunlight into shimmering green columns. Abalone, lobster, and hundreds of fish species sheltered within. Divers described it as one of the great natural spectacles on Earth.

Today, 95% of it is gone. Hover over the chart to explore how the canopy has changed decade by decade.

The collapse did not happen overnight. Each El Nino brought warm, nutrient-poor water surging down from the north, and the kelp could not recover before the next blow arrived. Three forces conspired together with catastrophic effect.

Hover over the chart to see how ocean warming, sea urchin barrens, and kelp loss have tracked together since 1987. Notice how all three trends tighten after 2010.

The East Australian Current has pushed warm water into Tasmanian waters at four times the global average rate of ocean warming. Without large predatory lobsters to control them, urchins multiplied across the reefs and grazed them to bare rock. Kelp cannot establish where there is nothing to hold on to.

Something remarkable is beginning to happen. Click any site on the map to find out what scientists and communities are doing about it.

Hundreds of giant kelp have reached the ocean surface at active restoration sites along Tasmania’s east coast - plants absent from those reefs for over a decade. The work is led by researchers at the University of Tasmania’s Institute for Marine and Antarctic Studies, in partnership with The Nature Conservancy Australia, commercial divers, lobster fishers, and Tasmanian Aboriginal communities.

The technique is proven. The genetics are being refined using AI tools developed by CSIRO and Google. The question now is whether the project can grow fast enough to matter.

The underwater cathedrals can be rebuilt. But the window to act is narrowing with every passing summer.

References

Butler, C. L., Lucieer, V. L., Wotherspoon, S. J., and Johnson, C. R. (2020). Multi-decadal decline in cover of giant kelp Macrocystis pyrifera at the southern limit of its Australian range. Marine Ecology Progress Series, 653, 1-18. https://doi.org/10.3354/meps13510

CSIRO. (2024). An ocean forest in danger. https://www.csiro.au/en/news/all/articles/2024/june/kelp-forests

Edyvane, K. S. (1999). Conserving marine biodiversity in South Australia. South Australian Research and Development Institute.

Ling, S. D., Johnson, C. R., Frusher, S. D., and Ridgeway, K. R. (2009). Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift. Proceedings of the National Academy of Sciences, 106(52), 22341-22345. https://doi.org/10.1073/pnas.0907529106

Nature Conservancy Australia. (2024). The Tasmanian giant kelp restoration project. https://www.natureaustralia.org.au/what-we-do/our-priorities/oceans/ocean-stories/giant-kelp/

University of Tasmania. (2024). Working together to safeguard threatened giant kelp forests. https://www.utas.edu.au/about/news-and-stories/articles/2024/working-together-to-safeguard-threatened-giant-kelp-forests

Acknowledgement of generative AI use

Claude (Anthropic) was used to assist with R narrative framing and identifying relevant data sources. Kelp canopy and urchin barren values were verified against the cited peer-reviewed sources. All editorial decisions, story direction, and visualisation were made by the author.