It's the length of Africa, home to more than 2,000 marine species—many found nowhere else on Earth—and one of the world's largest underwater forests

There’s a magical place off the coast of Australia that is home to 1,500 types of seaweed, 1,000 different sponges, more than 730 different fishes and over 750 species of molluscs – and, no, it’s not the Great Barrier Reef (GBR). 

While the GBR is known for its corals, the rocky reefs of the GSR are connected by another key ecosystem: kelp.

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Although lesser known than the GBR, Australia’s Great Southern Reef (GSR) is equally impressive. This 8,000km stretch of interconnected temperate reefs – many of which are easily accessible from the coastline – run along the bottom of the country from Kalbarri in Western Australia to Coolangatta in Queensland.

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Put another way, if you think of the shape of Australia as an irregular biscuit, the Great Southern Reef is found on the edges that would be touched by tea if you gave it a good dunk in a cuppa. 

This extraordinary habitat is known for its marine biodiversity. It is home to a vibrant community of marine animals, many of which are found nowhere else on the planet. 

This includes one of the rarest fish in the world: the red handfish. These grumpy-looking fish might look like sad little toads with lipstick smeared around their mouths but they have developed a very special skill: using their fins like hands to walk along the seabed. 

There are very few of these teeny fish remaining in the wild. “Known from just two small 50m patches of reef in Tasmania, red handfish are thought to be one of the rarest fish species in the world,” writes the Great Southern Reef Foundation on its website. 

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In 2024, there were believed to be fewer than 100 wild red handfish. The situation was so dire that scientists stepped in, taking some individuals into captivity to shield them from marine heatwaves before breeding and releasing 65 captive-raised fish into the wild in 2025. 

Another threatened species found in these waters is the spotted handfish, related to the red handfish. This “extremely rare species of anglerfish [is] found only in a very specific location along the Great Southern Reef – near the Derwent River estuary in Tasmania,” according to the Great Southern Reef Foundation’s website. 

More subtle than their red handfish cousins, these fish don’t have scarlet markings but, instead, are sprinkled with delicate black, brown or orange dots across their pale bodies. 

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These aren’t the only bizarre creatures unique to the Great Southern Reef. 77% of the fish and mobile invertebrates in these waters aren’t found anywhere else in the world.

Leafy seadragons, which look like seahorses that have dressed up like showgirls with feathery headdresses and elaborate leaf-like appendages, also live here. 

Giant Australian cuttlefish flock here during the winter (May and June) to mate, bringing spectacular drama as males fight with each other over the females. 

Not forgetting the adorable Southern dumpling squid which are often hiding out just under the sand. “They will burrow themselves into the seafloor during the day, using their second pair of arms to rake sand over the top of their body as a form of protection,” explains the Great Southern Reef Foundation. “The upper surface of their skin is highly specialised and contains two special cell types. One acts like glue to hold the sand in place even if they are flushed out of the seabed by a potential predator. The other contains special acid cells that allow the sand coat to disconnect all at once — leaving it as a sinking decoy while the squid jets away.”

These are just a few of the many delightful beings living in the GSR. Sadly, the habitat and the magnificent organisms found there are under threat from climate change and warming waters.  

"When the temperature changes, everything biological changes,” says marine ecologist Thomas Wernberg on the University of Western Australia’s website. “For example, the metabolism of species goes up and suddenly organisms have to eat more to stay alive. Shifting ocean currents also influence temperature changes and can cause an invasion of tropical species that over-graze kelp forests.”

Researchers like Wernberg are trying to study how to protect and restore unique ecosystems like the Great Southern Reef. But, while restoration can have an impact, it’s “just a little Bandaid” compared to what really needs to be done, he says. 

“Importantly, no measure of restoration can stop climate change – only limiting carbon emissions will,” he adds. “We need to treat the cause not the symptom.”

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Top image: Sixbar coralfish Tilodon sexfasciatus at Greenly Island, Great southern Reef, South Australia. Credit: Peter Southwood, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons