How a vanished golden forest once thrived beneath Sydney's waves
In short: In the 1980s, 70km of vital marine habitat disappeared from Sydney’s coast without a trace. This wasn't a forest of trees, but a golden seaweed called Crayweed. Now, a dedicated team is working to replant these underwater meadows to restore a broken ecosystem.
Between Palm Beach and Cronulla, a massive expanse of temperate seaweed forest vanished during the 1980s. This habitat, dominated by the golden-coloured Phyllospora comosa, or Crayweed, once flourished along the Sydney coastline. Scientists believe the decline was driven by human activity, specifically the high volumes of sewage pumped directly into Sydney’s bays and beaches prior to the 1990s. While water quality has since improved dramatically, the forests have failed to return to the metropolitan area on their own.
The loss of these underwater landscapes is significant. Professor Adriana Verges, a marine ecologist at UNSW and the Sydney Institute of Marine Science, compares the disappearance of large seaweeds to the destruction of tropical coral reefs. These forests are much more than just seaweed; they underpin coastal food webs by providing essential food and habitat for hundreds of species, including abalone, rock lobster, and various epifauna. Beyond biodiversity, these forests play a role in the global climate by producing oxygen and capturing atmospheric carbon.
Restoration is being led by the Operation Crayweed campaign, featuring researchers like Dr. Ziggy Marzinelli and Derrick Cruz. The process is far more complex than traditional terrestrial reforestation. Because they cannot simply sow seeds, the team must harvest fertile, adult plants from healthy, established populations—such as those found between Port Macquarie and Tasmania—and transplant them to deforested sites. To ensure long-term success, they collect samples widely to maintain genetic diversity, while carefully harvesting only small amounts to ensure the source populations remain undamaged.
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Sources
- Summary by Intellect · source: Meet the team restoring critically important underwater forests | Discovery | Gardening Australia
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