The Bramble Cay melomys was a small, brownish rodent found nowhere else on Earth. It lived among the sparse vegetation of the cay, feeding on the plants that grew in the sandy soil. Surveys in the 1970s and 1980s recorded healthy populations. By 1998, researchers documented significant vegetation loss on the island's southern and northern shores. The last confirmed sighting of the melomys came in 2009. Exhaustive trapping surveys in 2014 found nothing. In 2016, the Queensland government declared the species extinct, with the Australian federal government formally following in 2019, making it the first mammal known to have been driven to extinction by anthropogenic climate change. Rising seas had inundated the cay repeatedly, destroying the vegetation the melomys depended on. In August 2021, artists from Erub Island responded with Maizab Kaur Mukeis, sculptures of the animal crafted from ghost nets, hoping to create awareness of marine ecosystem damage. The work was selected as a finalist for the National Aboriginal and Torres Strait Islander Art Awards.

Despite its diminished vegetation, Bramble Cay remains the largest nesting site for green turtles in the Torres Strait and supports the only large seabird colony in the region. During nesting season, Darnley Islanders travel the 45 kilometres from Erub to collect turtle and bird eggs, a practice that predates any European presence by many generations. Certain families have ancestral connections with the cay, and the people of Erub also grant egg-collecting permission to communities from neighboring Ugar (Stephens Island) and Mer (Murray Island). This customary tenure, recognized by Australian law, reflects a relationship between people and this remote outcrop of land that has been sustained across centuries of rising and falling tides.

Bramble Cay marks the entrance to the Great North East Channel through the Torres Strait, a fact that has shaped its human history since before European contact. In 1862, a mining lease was granted to the Anglo-Australian Guano Company, though the phosphatic rock proved too low-quality for a permanent operation. A lighthouse was eventually erected, demolished in 1954, and replaced by the current 17-metre stainless steel tower that was equipped with solar power on 6 January 1987. The automated light still guides shipping through waters where coral reefs and fierce currents make every transit a calculation. Three kilometres to the northeast, the submerged Nautilus Reef lurks just below the surface, named for a vessel rather different from Captain Nemo's but no less subject to the strait's hazards.

Bramble Cay occupies a peculiar jurisdictional position: it lies 25 kilometres north of the seabed and fisheries jurisdiction line between Australia and Papua New Guinea, yet Australian sovereignty is undisputed and explicitly recognized by PNG. Administratively, it belongs to the Shire of Torres. But political boundaries matter less here than physical ones, and the physical boundaries are shifting. The cay has been losing vegetation since at least 1924, when surveys first documented its plant cover. The same ocean warming and sea-level rise that eliminated the melomys continues to reshape the island. The coral reef surrounding the cay is relatively small and isolated from other Torres Strait reefs, offering limited protection from wave action. What remains is a sand cay, a lighthouse, a few patches of hardy plants, and the memory of a species that lived nowhere else and vanished because its world grew too small.