Tasmania

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History of Tasmania's Giant Kelp Forests

Tasmania’s coastal waters were once home to thriving Giant Kelp forests, scientifically known as Macrocystis. These colossal seaweeds played a vital role in Tasmania’s marine ecosystems for centuries. Towering up to 35 meters in height, Giant Kelp provided shelter and sustenance to a diverse array of marine creatures including fish, molluscs, crustaceans and other species.

Just like large trees on land create wind barriers, Giant Kelp forests are crucial in buffering coastlines from erosion. The thick forests not only slow the water movement, they also catch the drifting spores and larvae of a variety of organisms, like rock lobster and kelp, and help them to settle on the seabed to grow.

Giant Kelp forests are a major contributing factor to the overall health of our ecosystem. They maintain water quality by absorbing excess nutrients, sequester carbon dioxide and slow down ocean acidification and produce up to 100 times more oxygen than a terrestrial forest of equivalent size.

The Disappearance of Giant Kelp

Unfortunately, there has been a dramatic decline of Giant Kelp forests in recent decades. Research has shown that since the 1960s 95% of Giant Kelp forests have disappeared on Tasmania’s east coast. This resulted in Giant Kelp to be listed as an endangered community by the Australian Government in 2012 – the first such listing for a marine community in Australia.

The dramatic decline of Giant Kelp Forests is primarily due to Tasmania’s east coast ocean water temperature rising at three to four times the global average. Eddies that spin off the EAC and south towards Tasmania are larger and more frequent, resulting in warmer, nutrient poor water. Giant Kelp however typically needs cold, nutrient rich water to grow. The warming waters bring non-native invasive species to the area, like the long-spined sea urchin (Centrostephanus rodgersii) which is responsible for destructive overgrazing of Giant Kelp forests.

Efforts to restore Giant Kelp Forests

Over the last few years, the Australian Government, scientists, and nature conservation organisations have been working on management strategies and solutions to restore the Giant Kelp Forests along Tasmania’s east coast.

Researchers from UTAS have cultivated Giant Kelp that tolerates warmer and more fluctuating ocean temperatures. In collaboration with dive operators, they have been working on replanting the kelp seedlings manually.

Governmental management strategies are in place to control the long-spined sea urchin population by supporting the commercial dive fishery, recreational dive community and research programs and by increasing the lobster population through the East Coast Rock Lobster Stock Rebuilding Strategy.

How we contribute to a healthy Giant Kelp population & the restoration of marine habitat

Southern Ocean Carbon is a partner of the Blue Economy CRC and has been involved with extensive research in this field, before setting up a trial mariculture site in Southern Tasmania in June 2023, where heat tolerant cultivars of Giant Kelp are being farmed. The trial farm will be in place for ~18 months to enable the testing of systems for kelp deployment, monitoring, and harvesting. This is phase 1 of a research trial designed to test seaweed species and infrastructure for potential offshore (deep ocean) farming. The co-benefit is that seaweed mariculture farms will create habitat and protect the growing area for a variety of marine life, effectively contributing to a healthy ecosystem.

Going Global

We have identified various locations worldwide where human operations have negatively impacted seabeds and marine habitats, and local businesses and governments are actively seeking opportunities to rewild the coastal waters and look for positive impact investing strategies.