June 23, 2016

The Bramble Cay melomys (Melomys rubicola)—seen here in 2002—has vanished from the Earth. Scientists blame the small rodent’s extinction on climate change. Credit: Queensland Department of Environment and Heritage Protection

On June 7, Australian authorities confirmed the extinction of a small rodent called the Bramble Cay melomys. The animal was native only to Bramble Cay, a small northern Australian island in the Torres Strait. The main reason for the rodent’s extinction was the elimination of its habitat on the small, sandy reef island. Climate change has caused rising tides and sea levels, wiping out much of Bramble Cay’s leafy plants—the rodent’s main food source. Some rodents likely drowned, and the rest simply starved. The Bramble Cay melomys, then, became the first mammal casualty of anthropogenic (human-caused) climate change. In 1999, the death of the last Golden Toad in Central America marked the first documented species extinction driven by climate change.

Bramble Cay is a reef island of about 12 acres (5 hectares) at the northern end of the Great Barrier Reef near Papua New Guinea. At most, the island reaches 10 feet (3 meters) above sea level. The Bramble Cay melomys was first seen there in the 1800’s. The small animal had a round brownish body, long whiskers, and a lumpy tail. In 1978, researchers counted several hundred of the rodents on Bramble Cay, noting that they were distinct from other types of Australian melomys. Since then, however, the island’s population of the melomys—also called the mosaic-tailed rat—had dwindled along with its quickly disappearing habitat. In 2009, fishermen saw a few of the critters scurry from beneath a pile of sticks, and that was the last time the Bramble Cay melomys was seen. In recent years, extensive searches for the rodents turned up nothing. Bramble Cay’s seemingly insignificant but unique species of animal life is gone forever.

March 29, 2016

The Great Barrier Reef, off Australia’s northeastern coast, is the largest coral reef system on Earth.
Credit: © Gary Bell, Getty Images

Recent studies reveal that the Great Barrier Reef, the world’s largest system of coral reefs, is suffering from severe and record-setting bleaching. Bleaching, as the term suggests, is a whitening coral disease caused by the loss of colorful single-celled algae called zooxanthellae. Most coral depend on zooxanthellae for food and the creation of their limestone skeletons. Coral cannot survive for long without zooxanthellae. The main cause of bleaching is heat stress caused by rising water temperatures produced by global warming. This year’s El Nino, a periodic warming current in the Pacific Ocean, has added to the heat stress. The Great Barrier Reef is made up of more than 3,000 individual reefs that extend about 1,400 miles (2,300 kilometers) along the northeast coast of Australia.

Great Barrier Reef
Credit: WORLD BOOK map

Australia’s Coral Reef Studies group filmed the northern half of the Great Barrier Reef over a period of six days. The group—based at James Cook University in northeast Australia—found that 95 percent of 500 reefs studied showed evidence of severe bleaching, a drastic and record-setting percentage. Professor Terry Hughes, who led the film survey, fears the current bleaching event could kill up to 50 percent of the system’s reefs. The group will soon have results on the lower half of the reef, and the Great Barrier Reef Marine Park Authority will conduct in-water surveys to more exactly determine the extent of the bleaching. This year’s bleaching is the third such event since 1998, when the disease killed 16 percent of the world’s coral reefs. A 2005 bleaching wiped out half the coral reefs in American waters of the Caribbean Sea.

If water temperatures cool, zooxanthellae will return and corals will survive and resume their normal colors. This process can take decades, however, and bleaching stress decreases coral’s future ability to grow and reproduce. It also increases the likelihood of later—and increasingly worse—bleaching events.