Between the tip of Australia's Cape York Peninsula and the Western Province of Papua New Guinea lies the Torres Strait, known to its Islanders as Zenadh Kes. It is about 150 km (93 mi) wide at its narrowest. It connects the Coral Sea and the Pacific to the east with the Arafura Sea and the Gulf of Carpentaria to the west. It is also remarkably shallow, mostly 7 to 15 m deep, and is scattered with at least 274 islands and around 580 coral reefs. Those reefs cover about 2,400 km² and sit among some of the most extensive seagrass beds in the world. That makes the strait one of the last strongholds of the dugong, a busy but hazardous shipping lane, and the home of the Torres Strait Islanders, about 4,500 of whom lived on the islands at the 2016 census. The Scottish geographer Alexander Dalrymple named it after Luís Vaz de Torres, the Spanish expedition's navigator who sailed through in 1606.
The strait is best understood through the animals that live in it, because nearly every chapter of its history, from pearling to the 1978 treaty with Papua New Guinea, comes back to what lives in its water.
Dugongs on the seagrass meadows around Thursday Island
The dugong is the only sea mammal that feeds purely on plants, and it depends on seagrass, especially the low-fibre Halophila and Halodule species. Shallow, sheltered water with wide seagrass meadows is exactly what the Torres Strait offers. Australia holds the world's largest dugong population, spread from Shark Bay in Western Australia to Moreton Bay in Queensland, and the strait holds the biggest of its regional herds. Estimates put the population there at more than 25,000 animals, in waters such as those off Thursday Island. Many animals move back and forth to the coast of New Guinea.
Even a large herd is fragile. Dugongs can live 70 years or more, but a female carries one calf for 13 to 15 months and nurses it for well over a year. A population stays stable only if fewer than about 5% of adults die each year. The IUCN lists the species as Vulnerable. For Torres Strait Islanders, dugong meat and oil have always been among the most valued foods, and traditional hunting remains legal for them. Papua New Guinea, which has the dugong as a national animal, likewise bans all but traditional hunting. Management programmes in the strait now combine Islander knowledge of "sea country" with scientific surveys, because the main pressures on the herds are hunting, nets and damage to the seagrass they need.
The islands that frame these meadows come in four kinds. Those closest to New Guinea, such as Saibai and Boigu, are low islands built from river mud. The western islands, including Muralag (Prince of Wales Island), the largest in the strait, are granite peaks at the northern end of the Great Dividing Range, cut off when the sea rose after the last ice age. The central islands, such as Warraber, are coral cays, and the eastern ones, such as Mer, are volcanic.
Green turtles and the nesting beach at Bramble Cay
Four species of sea turtle use the strait's waters: the green, hawksbill, flatback and ridley turtles. The largest green turtle nesting site in the Torres Strait, as of 2008, is Bramble Cay, called Maizab Kaur in the Meriam Mir language of Mer Island. It is a 3.62-hectare sand cay about 50 km north of Erub (Darnley Island) and about 230 km north-east of Cape York. It is the northernmost point of land in Australia and marks the end of the Great Barrier Reef. Green turtles come ashore there every year to lay eggs, and the cay also holds the only large seabird colony in the region. The cay sits at the entrance to the Great North East Channel and has caused at least five shipwrecks. A lighthouse has stood on it since 1924; the present 17 m stainless steel tower replaced the original in 1954 and has run on solar power since January 1987. People from Erub have visited the cay for generations to hunt, gather food and look after it.
The Bramble Cay melomys, last seen in 2009
Bramble Cay was also the only home of the Bramble Cay melomys (Melomys rubicola), a reddish-brown rodent 14.8 to 16.5 cm long in the body with a long tail that could grip at the tip. Sailors from HMS Bramble found it in April 1845 and, finding it everywhere, shot the animals with bows and arrows for fun. A naturalist on HMS Fly collected the type specimen the following month, and the zoologist Oldfield Thomas named the species in 1924. It lived only on the cay's vegetated core of about 2 hectares, which rises no more than 3 m above sea level, and fed on purslane and turtle eggs. It was the only mammal endemic to the Great Barrier Reef.
Visitors in 1845 and a survey in 1978 both described "hundreds" of animals. The decline after that shows up clearly in the surveys:
The last confirmed sighting was in 2009. In June 2016, Queensland's environment department and the University of Queensland reported that the species was extinct. They concluded that seawater had repeatedly flooded the cay during the previous decade, stripping its vegetation, and called this probably the first mammal extinction caused by human-driven climate change. Local sea level had been rising by about 0.6 cm a year between 1993 and 2010, and high storm surges had become more frequent. The Australian government formally recognised the extinction on 18 February 2019. The researchers left open a slim chance that a population survives undiscovered in the Fly River delta of Papua New Guinea.
Tropical rock lobster and the walk to Yule Island
One of the strait's most important catches today is the ornate tropical rock lobster (Panulirus ornatus), a large spiny lobster with a blue-green shell, big horns and striped legs. It supports fisheries on both the Australian and Papua New Guinean sides, and in north-east Australia a commercial fishery for it has existed since 1966. Its life cycle crosses the border every year. From mid-to-late August, adult lobsters leave the Torres Strait and migrate north-east to Yule Island in the Gulf of Papua to breed. The breeding season runs from November to March or April. Most breeding adults are about three years old, and a female can produce up to three broods a season. The young pass through 11 larval stages before they look like lobsters. Because the fishery depends on one migrating species, Australia has started farming the lobster as well.
Pearl shell and the Thursday Island boom, 1860s to 1970
Before lobster, the money was in shell. Islanders had always dived for pearl shell, but a commercial industry in pearl shell and trochus shell took off in the 1860s to supply mother-of-pearl for buttons and decoration. By the 1890s the Torres Strait was supplying more than half of the world's pearl shell. Experienced divers came from many countries, especially Japan. The industry was based on Thursday Island, Waiben in the local Kawrareg dialect, a 3.5 km² island 39 km north of Cape York that is still the region's administrative centre. It had 2,805 residents in 2021. Plastic buttons ended the boom, and the industry collapsed around 1970.
The boom came at a heavy cost. Queensland annexed the islands in 1879, and in June 1875 a measles epidemic had already killed about a quarter of the Islander population, up to 80% on some islands. Today the same waters carry large ships. Vessels with a draught of up to 12.2 m use the Prince of Wales Channel north of Muralag, where the shallowest charted depth was 10.3 m in 2011. Saltwater crocodiles live around the islands as on the neighbouring coasts. Upstream, the Fly River drains into the north of the strait, and between 1984 and 2013 the Ok Tedi mine discharged about two billion tonnes of untreated waste into the Ok Tedi River, a tributary of the Fly, harming about 1,000 km of the two rivers. Mining waste carried down the Fly is counted among the main environmental risks to the strait's reefs and seagrass.
The 1978 Torres Strait Treaty and its Protected Zone
Australia and Papua New Guinea signed the Torres Strait Treaty in December 1978, three years after Papua New Guinea's independence, and it came into force in February 1985. It draws two separate lines. A Seabed Jurisdiction Line divides everything on and under the seabed. A Fisheries Jurisdiction Line divides fish in the water, and the two countries agreed to share those catches. Some islands, including Saibai, Boigu and Dauan, stay Australian even though they lie north of the seabed line, within sight of the New Guinea coast. The treaty also created the Torres Strait Protected Zone. Inside it, Islanders and the people of 13 named Papua New Guinean "Treaty Villages", among them Mabadauan and Sigabadaru, may move freely without passports or visas for traditional purposes, so that both peoples can keep their traditional ways of life. The treaty is also meant to protect the habitats that the strait's dugongs, turtles and lobsters depend on.
To the east, the reefs give way to the deeper water described in our Coral Sea guide; to the west the strait opens onto the Arafura Sea; and the reef system that ends at Bramble Cay is traced from its southern end in our guide to the geography of the Great Barrier Reef.