Sydney, Australia

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Restoring Sydney's Lost Kelp Forests

With the support of our local project partner Operation Crayweed, SeaTrees is conducting the restoration of 43,056 sq-ft (4,000 sq-m) of kelp within two separate project sites along the South Bondi subtidal rocky reef in Sydney, New South Wales, Australia.

Our vision is to restore all of the 70km of lost kelp forests along the Sydney coast.

Crayweed Restoration

Phyllospora comosa, known locally as 'Crayweed' after the crayfish that use these underwater forests for shelter, once formed dense beds on shallow reefs along the Sydney coastline. These underwater forests have become locally extinct, causing detrimental repercussions for native fish, abalone, crayfish, and coastal marine biodiversity. 

Project Summary

Impact Metrics:

  • 70% of Australia’s population lives along Sydney’s underwater crayweed forests.
  • Crayweed decline is linked to climate change and warming ocean waters, poor water quality, outbreaks of disease, and the removal of predators at the top of food webs by overfishing.
  • Young crayweed appears about 6 months after transplanting and grows into mature adults after 18 months.
  • This project restores critical habitat for hundreds of species including abalone and crayfish, improves local marine biodiversity, and increases the likelihood of critical marine species returning to the area.


In Rapid Decline

Beginning in the early 1980s, the crayweed population suffered an abrupt decline, eventually going locally extinct. This decline was primarily due to poorly treated sewage pumped directly onto Sydney’s beaches and bays. Although water quality in Sydney has improved dramatically since the addition of deep ocean sewage outfalls, the crayweed forests have not returned.

Crayweed is among the most important ecosystems on the planet, providing critical food and habitat for hundreds of species. These vast underwater forests support coastal food webs, sequester immense amounts of atmospheric carbon, produce oxygen for marine life, and support unique coastal biodiversity, which is not supported by any other seaweed species.


Subtidal Rocky Reefs


Operation Crayweed

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Crayweed Restoration Process

Prior to planting, a series of underwater surveys are completed to characterize biodiversity, so that changes that result from reintroducing crayweed can be adequately quantified.

With the support of our project partner Operation Crayweed, this project involves the transplantation of healthy, fertile adults from existing populations and attaching them to deforested rocks using mats made of biodegradable mesh drilled into the bottom of the rocky reef. 

The newly reproduced ‘baby’ crayweed is attached to the reef, forming the basis of a new, self-sustaining population, which expands from the initially restored patch. Divers then continuously monitor the project site for crayweed survival and the return of marine life to the area. This process has already proven successful as adult crayweed has been observed hundreds of meters from the original patch.

By creating patches of transplanted crayweed on a reef, we are restoring forests of this essential species. Through this effort, we are also restoring its marine biodiversity and increasing the likelihood of critical marine species returning to the area and thriving as they once did. 


Sustainable Development

This project provides long-term employment for the local community. This in turn drives other Sustainable Development benefits.

* Thanks to the support of our generous brand partners, this project has been fully funded. If you'd like to support one of our other great projects, send an email to and let us know what lights you up the most!